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Suggested Citation:"3 Meeting the Challenges With New Technologies and Tools." National Research Council. 2006. Geological and Geotechnical Engineering in the New Millennium: Opportunities for Research and Technological Innovation. Washington, DC: The National Academies Press. doi: 10.17226/11558.
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CHAPTER THREE
Meeting the Challenges With New Technologies and Tools

The seven areas of national need served by geoengineering and the associated critical issues identified in the 1989 National Research Council report on geotechnology (see Table 2.1) has helped the geoengineering community in the United States to define its research agenda for the last 15 years. The knowledge gaps and new realities discussed in Chapter 2 provide a basis for establishing the research agenda for the geoengineering community at the beginning of the twenty-first century.

In this chapter we present an overview of promising current and emerging technologies in various fields of engineering and science that have the potential to improve significantly the practice of geoengineering in the twenty-first century. Emphasis is placed on the emerging technologies that are focal areas for research expenditures nationwide, including bioengineering, nanotechnology, sensors and sensing, geophysical methods, remote sensing, and information technology and cyber infrastructure. National Science Foundation (NSF) priority areas and fiscal year (FY) budget requests for some of them are given in Table 3.1. Of special interest to geoengineering are Biocomplexity in the Environment, Mathematical Sciences, and Nanoscale Science and Engineering. Each section of the chapter consists of two parts. The first part presents a brief description of the technology designed for readers in the geoengineering research community; a short list of selected references is included to

Suggested Citation:"3 Meeting the Challenges With New Technologies and Tools." National Research Council. 2006. Geological and Geotechnical Engineering in the New Millennium: Opportunities for Research and Technological Innovation. Washington, DC: The National Academies Press. doi: 10.17226/11558.
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TABLE 3.1 NSF Budget Request by Priority Area

PRIORITY AREA

FY 2005 REQUEST (IN MILLIONS)

Biocomplexity in the Environment

$100

Human and Social Dynamics

$ 23

Mathematical Sciences

$ 90

Nanoscale Science and Engineering

$305

Workforce for the 21st Century

$ 20

 

SOURCE: http://www.nsf.gov/about/budget/fy2005.

provide an entrée to the field for geoengineering researchers. The second part is intended to spark the imagination about the possible application of these technologies.

3.1 BIOTECHNOLOGIES

3.1.1 Background

The latter half of the twentieth century witnessed the transformation of biology from a descriptive science to a science that is fully able to describe the structure, mechanisms, and chemistry that control the behavior of living things. This transformation has led to an explosion of new applications in fields as disparate as medicine, agriculture, computing, and Earth processes. Applications to Earth processes in particular may provide exciting new avenues for geoengineering.

Initially, abiotic physical and chemical processes dominated the shaping of Earth. These same processes also led to the establishment of self-replicating molecules that started to exploit the residual stored energy in inorganic constituents using existing energy gradients and flux driven by the geoheat gradient and sunlight. From this aseptic beginning, life began to build more complex systems and initiate a radical reshaping of the geochemical and geological environment of Earth. The biologically induced changes are dramatic. For example, life has changed Earth’s

Suggested Citation:"3 Meeting the Challenges With New Technologies and Tools." National Research Council. 2006. Geological and Geotechnical Engineering in the New Millennium: Opportunities for Research and Technological Innovation. Washington, DC: The National Academies Press. doi: 10.17226/11558.
×

surface fundamentally from a highly reducing environment to an oxidized environment. The evolution of photosynthetic organisms beginning approximately 3.5 billion years ago established present-day oxygen concentrations and radically changed physical, geological, chemical, and biological processes on our planet (see Figure 3.1). Increased oxygen affected geologic processes by causing the oxidation of minerals as well as biology by creating conditions favorable for oxygen-breathing organisms. Life even affects the weather and helps to regulate the temperature of Earth. For example, some algae or phytoplankton in the ocean emit dimethyl sulphide that is capable of nucleating raindrops and causing rain. As the sun shines, more phytoplankton grow. These in turn nucleate clouds, which in turn control the temperature (http://www.oceansonline.com/gaiaho.htm).

Biological processes affecting Earth work on very small scales and in short time frames. It is the sheer magnitude of the amount of biomass and the cumulative effects of these processes over long time frames that shape Earth. It is estimated that the approximately 350 to 550 × 1015 grams

FIGURE 3.1 The biogeological time line. Approximate timing of major events (billion years from present day) in the history of life on Earth. SOURCE: Image courtesy of Dr. Bharat Patel, http://trishul.sci.gu.edu.au/courses/ss13bmm/introduction_MAM.pdf.

Suggested Citation:"3 Meeting the Challenges With New Technologies and Tools." National Research Council. 2006. Geological and Geotechnical Engineering in the New Millennium: Opportunities for Research and Technological Innovation. Washington, DC: The National Academies Press. doi: 10.17226/11558.
×

of carbon are stored in 4 to 6 × 1030 microorganisms, which represent 50 percent of the total amount of carbon stored in living organisms on Earth (Whitman et al., 1998). Assuming an average cell diameter of 1 μm, the surface area of 1030 microorganisms would amount to over 1 × 1013 square kilometers of a one-cell-thick live membrane acting as a biochemical factory. In contrast, Earth’s surface is much smaller, only approximately 1 × 108 square kilometers. Therefore, small-length-scale bioprocesses that work at the micro- to millisecond time frame can affect large areas and operate over millennia.

Biomediated geochemical interactions have a significant effect on the composition and properties of soil and rock near Earth’s surface. Microbial life (or any biological activity, for that matter) requires a source of energy (sunlight or chemical reactions), a source of cellular carbon (inorganic or organic compounds), water, and an adequate environment for growth. Microorganisms can have a short reproduction period (10 minutes to an hour). These high-speed generation rates, mutations, and natural selection lead to very fast adaptation and extraordinary biodiversity and rapid propagation. Therefore, microbial activity can be expected everywhere in the near surface.

There are from ~ 109 to 1012 microorganisms per kilogram of soil in Earth’s near surface (upper few meters). Bacteria, the most common microorganisms in soils, are 0.5 μm to 3 μm in size, and spores can be as small as 0.2 μm. Thus, microorganisms are in the same size range as fine sand and smaller soil particles as shown in Figure 3.2. Most biological activity occurs in silt-size or coarser particles and rock fractures. Additional information on biological principles and biomediated geochemical processes, their role on the evolution of Earth, and their potential applications is in Chapelle (2001), Ehrlich (1996, 1999), Hattori (1973), and Paul and Clark (1996), among others.

3.1.2 Biology and Geoengineering

Given the ubiquitous presence of biological processes in the subsurface, it is surprising that only recently are geoengineers becoming

Suggested Citation:"3 Meeting the Challenges With New Technologies and Tools." National Research Council. 2006. Geological and Geotechnical Engineering in the New Millennium: Opportunities for Research and Technological Innovation. Washington, DC: The National Academies Press. doi: 10.17226/11558.
×

FIGURE 3.2 Comparative sizes of microorganisms and soil particles. SOURCE: Mitchell and Santamarina (2005); used with permission.

aware of them and are beginning to study their role in determining and controlling soil properties and behavior and exploiting them in engineering applications.

Geoenvironmental engineering applications. Perhaps the greatest progress in practical application of biological processes in geoengineering has been in bioremediation of contaminated ground, and much of this work has been under the purview of environmental engineers. Nonetheless, geoengineers have contributed significantly to these developments through their work on site characterization, developing means for bioaugmentation and biostimulation in the ground, the definition of seepage flows and pathways, the development and implementation of sampling and monitoring programs, and the design and construction of passive reactive barriers. A passive reactive barrier consists of a reactant-filled trench across which a contaminated seepage plume must pass. The reactants in the trench then neutralize the contaminants so that the seepage emerging from the trench no longer poses an environmental risk.

Even anthropogenic compounds in soil are broken down by many different microorganisms and plants. Chlorinated aliphatics and aromatics

Suggested Citation:"3 Meeting the Challenges With New Technologies and Tools." National Research Council. 2006. Geological and Geotechnical Engineering in the New Millennium: Opportunities for Research and Technological Innovation. Washington, DC: The National Academies Press. doi: 10.17226/11558.
×

are readily degraded, as are such complex compounds as polychlorinated biphenyls (PCBs), dioxins, and chlorofluorocarbons (CFCs) (NRC, 1993). Microorganisms can also remediate contamination due to metals and radionucles (http://www.lbl.gov/NABIR/). The organisms take their energy and carbon from these compounds and grow on them. Bioremediation takes advantage of these microbial processes to transmute or immobilize harmful substances. Still incomplete, however, is detailed understanding of how microbes transform contaminants at the molecular level, the nature of bioavailability of contaminants to microbes, interactions between biological and geochemical behavior, and microbial community dynamics and ecology.

Geomechanical applications. Biomediated geomechanical processes can have significant impacts on the geomechanical behavior of Earth materials. Microorganisms can selectively pull or immobilize metals and other inorganic compounds from solution, release enzymes and proteins that change their environment (e.g., charges, cation capacity, and pH of soils), and cause the precipitation of inorganic compounds. Microbial activity can directly or indirectly affect the physical properties of soils on a permanent or a temporary basis. Conceivably, it could even be used for such purposes as producing self-healing infrastructure.

Consider, for example, the construction of a conventional, aboveground building with subsurface infrastructure that requires a supported excavation in sand. Traditionally, this construction would normally require the installation of sheet piling or other shoring techniques to prevent infiltration of groundwater, to control movement of soil into the excavation, and to minimize subsidence of other existing and adjacent structures. Imagine instead that six months before construction and excavation a solution of specialized or genetically engineered microorganisms, along with special amendments to sustain the microorganisms, was injected into the sand throughout the depths requiring soil improvement. Assume that these microorganisms then produced a polymer or resulted in the precipitation of inorganic compounds that cemented the soil particles together and made the soil very stiff and possibly even impervious

Suggested Citation:"3 Meeting the Challenges With New Technologies and Tools." National Research Council. 2006. Geological and Geotechnical Engineering in the New Millennium: Opportunities for Research and Technological Innovation. Washington, DC: The National Academies Press. doi: 10.17226/11558.
×

to groundwater flow. A process of this type would also have application for the passive stabilization of loose saturated sands that are susceptible to liquefaction in seismic areas.

Or perhaps we could learn to grow foundations with biological processes much like trees grow roots. These foundations might require no disruptive excavation and might well provide the most appropriate support systems in unconsolidated soils. Applications of such stabilization technology might well also apply to tunneling, where biota could be called on to limit water inflows and prevent tunnel collapse. Even further, perhaps biological media would soften rock before it is excavated thus decreasing excavation costs and facilitating the use of the underground. Such techniques could result in faster excavation methods, and a reduction or elimination of excavation support and water control. These are only a few examples of the potential applications offered by a new paradigm of biomediated geochemical processes in geoengineering.

Even further, could biotechnology be developed such that a soil and microbial system could behave as a smart material responding to changing conditions such as occur during earthquakes or fires? Biotechnology is already used in resource recovery, with bioleaching being used to extract base metals, such as copper, zinc, and cobalt, and as a pre-treatment process to enhance extraction of gold. Thus, the promise of biotechnology to improve geoengineering and construction is already being realized. It is on a steep slope of advancement, and as new information, understanding, and technology become available new applications can surely follow.

In mining, truly revolutionary developments could occur if microorganisms could be used in situ to increase permeability and porosity of hard rock, specifically a sulfide mineral deposit, to enable good solution contact between the mineralized material and the lixiviants used to solubilize the minerals. This development would enable in situ mining of base and precious metals, which would significantly minimize the environmental impacts of mining. As well, microorganisms could be used to create an impermeable cavity underground to contain and control solutions in situ so that metals dissolved in the lixiviant could be

Suggested Citation:"3 Meeting the Challenges With New Technologies and Tools." National Research Council. 2006. Geological and Geotechnical Engineering in the New Millennium: Opportunities for Research and Technological Innovation. Washington, DC: The National Academies Press. doi: 10.17226/11558.
×

collected and to eliminate the possibility of contaminating groundwater in an in situ mining application.

3.2 NANOTECHNOLOGIES

3.2.1 Background

Nanotechnology deals with the structure and behavior of materials at a very small scale, typically from less than a micron down to submolecular sizes. Although perhaps never considering themselves nanotechnologists, soil scientists and engineers, with their interest in the study of clay-size particles (< 0.002 mm), are among the earliest workers in the field. Most material types and properties change with scale. For example, soil particles change in composition and shape from predominantly bulky quartz and feldspar to platy mica and clay over the range of particle sizes from sand and gravel down to silt and clay. A central challenge in geoengineering is to understand the changes in properties and behavior in moving from large to small, whereas a central theme in nanotechnology is to take advantage of this transition and attain novel material performance through nanostructuring of new materials. Material properties may be affected or engineered using nanoscale building blocks, controlling their size, size distribution, composition, shape, surface chemistry, and manipulating their assembly. Building nanoscale structures requires a fundamental understanding of nanoscale processes. Sidebar 3.1 highlights events in the development of nanotechnology.

Several important effects relative to inter-particle interactions gain relevance at the nanoscale. Nanomaterials possess very high specific surface (ratio of surface area to mass), and chemical activity is specific surface dependent. For example, the specific surface of a 1 nm cube is about 2400 m2/g. The maximum specific surface for bentonite clay (sodium montmorillonite) is about 800 m2/g, and about half of the constituent atoms are exposed at the surface and thus available for chemical interactions. High specific surface means high adsorption capacity and great sensitivity of nano-size particles to specific adsorbed

Suggested Citation:"3 Meeting the Challenges With New Technologies and Tools." National Research Council. 2006. Geological and Geotechnical Engineering in the New Millennium: Opportunities for Research and Technological Innovation. Washington, DC: The National Academies Press. doi: 10.17226/11558.
×

SIDEBAR 3.1
A Brief History of Nanotechnology

1959

Richard Feynman addresses the American Physical Society with “There’s Plenty of Room at the Bottom: An Invitation to Enter a New Field of Physics.” He recognizes the potential for new, exciting discoveries, the possibility of fabricating new materials and devices at the molecular scale, and identifies the need for new equipment and instrumentation for manipulation and measurement.

1980s

Important advances in instrumentation (e.g., scanning tunneling microscopes, atomic force microscopes, near-field microscopes), and in computer capability that can support extensive simulation studies (e.g., molecular dynamics). E. Drexler (1986) in “Engines of Creation: The Coming Era of Nanotechnology” coins the term “nanotechnology.”

2000

President Clinton announces a $500 million national nanotechnology initiative to generate breakthroughs in “materials and manufacturing, nanoelectronics, medicine and healthcare, environment, energy, chemicals, biotechnology, agriculture, information technology, and national security.”a

2005

There are more than 30 centers dedicated to nanotechnology research at U.S. universities and industrial laboratories. The annual research and development funding approaches $1 billion (combining National Science Foundation, Department of Defense, National Institutes of Heath, National Institute of Standards and Technology, National Aeronautics and Space Administration, Environmental Protection Agency allocations), with similar investments in Western Europe and in Japan. Atomic force microscopes can reach a sensitivity of sub-attonewton (10−18N) and deploy multiple parallel sensing probes for faster data gathering. Single-electron devices (transistors and memory) have already been demonstrated. Many commercial applications of nanotechnology research affect everyday life. The health risks of nanomaterials remain mostly unknown.

a Office of the Press Secretary. National Nanotechnology Initiative: Leading to the Next Industrial Revolution. Press Release, January 21, 2000. Available at: http://clinton4.nara.gov/WH/New/html/20000121_4.html. Accessed September 1, 2005.

Suggested Citation:"3 Meeting the Challenges With New Technologies and Tools." National Research Council. 2006. Geological and Geotechnical Engineering in the New Millennium: Opportunities for Research and Technological Innovation. Washington, DC: The National Academies Press. doi: 10.17226/11558.
×

materials. Interactions between nanoparticles are determined by inter-particle electrical forces. The pH and ionic concentration of the aqueous pore fluid alter the surface chemistry through dissolution, protonation, and adsorption. Therefore, pore fluid characteristics affect the self-assembly of nanocomponents and their long-term stability.

Nanosystems exhibit phenomena not usually observed in continuous systems. Some salient comparisons between different types of behavior at macro- and nanoscales and how analysis and engineering are done at these two levels are summarized in Table 3.2. Among the challenges to be met in introducing nanotechnology into geoengineering is to be able to upscale the nano-level phenomena and process descriptions to the macroscale behavior, materials, and structures that are the usual end points of the engineer’s efforts.

Current research in the nanotechnology field falls into three main areas:

  1. Fundamental issues that are concerned with improved dimensional and structural definition, local chemistry control, and surface properties;

  2. Assembly, segregation, and aggregation; effective biological synthesis, self-replication, and assembly; and environmental effects and fabrication control. Nanomaterials by design involve bottom-up fabrication, synthesis from solution rather than solid-state fabrication, short manufacturing times, and reproducibility.

  3. Application challenges. Among the application areas receiving attention at the present are nanoelectronics, optoelectronics, and magnetics; microspacecraft; bionanodevices for detection and mitigation of health threats; healthcare, therapeutics and diagnostics healthcare; and energy conversion and storage.

Additional information on fundamental aspects of nanotechnology and its applications is given in Zhang et al. (2002), Wang et al. (2002), and elsewhere. Articles and keynote lectures by Ken P. Chong are readily found on the Internet and are excellent sources of information on nanotechnology and the National Science Foundation’s vision for its future.

Suggested Citation:"3 Meeting the Challenges With New Technologies and Tools." National Research Council. 2006. Geological and Geotechnical Engineering in the New Millennium: Opportunities for Research and Technological Innovation. Washington, DC: The National Academies Press. doi: 10.17226/11558.
×

TABLE 3.2 Analysis and Engineering at Macro- and Nanoscales

 

MACROSCALE ENGINEERING IS DONE CONSIDERING THAT

NANOSCALE ENGINEERING IS DONE CONSIDERING THAT

General properties

 

  • Continuum behavior

  • Generalized constitutive models are applicable

 

  • Analysis of discrete particle behavior

  • In terms of discrete atomic nature of matter

  • The discrete distribution of charges

  • Quantized energy

  • The failure of continuum theories at this scale

Magnetic properties

 

  • Magnetic responses reflect the average of individual magnetic fields of a system’s constituents

 

  • Magnetic response reflects the electron’s intrinsic spin

  • Quantum tunneling of magnetic moment is observed (nanomagnets)

Conduction and transport processes

 

  • Flow is continuous according to Darcy’s law, Ohm’s law, Fourier’s law, Fick’s law, Advection-dispersion equation

 

  • Mean free path of phonons becomes comparable to the prevailing scale

  • Transport is sporadic and irregular

  • Charge confinement and surface effects produce electronic density states (nanodots) rather than the continuum density state in bulk matter

Thermo-dynamic conditions

 

  • Temperature and pressure are state parameters

 

  • Thermodynamic limits are reached at the nanoscale

  • Brownian motion cannot be disregarded

  • Thermal energy can exceed other excitations

  • Nanodevices are very sensitive to thermal noise

  • Strong coupling effects can develop among all forms of energy (thermal, electrical, optical, magnetic, mechanical, chemical). For example, nanodots exhibit strong optical emission

Suggested Citation:"3 Meeting the Challenges With New Technologies and Tools." National Research Council. 2006. Geological and Geotechnical Engineering in the New Millennium: Opportunities for Research and Technological Innovation. Washington, DC: The National Academies Press. doi: 10.17226/11558.
×

3.2.2 Nanotechnology and Geoengineering

A comparison of scales in nanotechnology and geomaterials was noted above and is presented graphically in Figure 3.3. As this figure shows, the fundamental behavior of clays is a nanomechanics problem, suggesting that concepts and models developed in nanotechnology can provide new insights and enhanced understanding of the behavior of clay-size particles and, even more important, new means to manipulate or modify this behavior.

Soil and rock are the world’s most abundant and lowest-cost construction materials. In some states (e.g., dense, dry, and cohesive) they are strong and durable. In others (e.g., loose, wet, and soft) they are weak and unsuitable. Is it possible or even conceivable that new knowledge and the development of processes at the nanoscale may someday transform these materials in ways that can make them even more useful and economical? The committee believes that investment in research on the possibilities should be a high priority.

In particular, developments in nanotechnology can aid in understanding the fundamental behavior of fine-grain soil at the particle level and lead to the development of engineered fine-grain soils. Readily available atomic force microscopes are now being used in mineral studies to explore local mineral variations in clays, such as surface charge and local hydrophobicity on mineral surfaces. Further developments will permit the use of nanomagnets to manipulate very small diamagnetic clay

FIGURE 3.3 Length scales: Nanotechnology and clay minerals.

Suggested Citation:"3 Meeting the Challenges With New Technologies and Tools." National Research Council. 2006. Geological and Geotechnical Engineering in the New Millennium: Opportunities for Research and Technological Innovation. Washington, DC: The National Academies Press. doi: 10.17226/11558.
×

minerals and to study mineral surface reactions using chemical force microscopy.

Although most nanoscale phenomena have not been studied in the context of geomaterials, the self-assembly of nanoparticles in aqueous solutions involves particle-level phenomena similar to fabric formation by clay-size particles. Clay soil fabric formation is mineral and pore fluid chemistry dependent. Figure 3.4 shows a phase diagram illustrating the relationship between the chemistry (pH and concentration) of an aqueous solution and the type of fabric formed by clay particles sedimenting down through that solution.

Although nanotechnology applications in geoengineering are largely exploratory at present, other applications in geoengineering can be

FIGURE 3.4 This fabric map for montmorillonite shows the inherent variety of self-assembly affecting clays. The states vary between repulsion dominated (dispersed fabric) and attraction dominated (aggregated fabric). These states reflect the balance between double layer/osmotic repulsion and van der Waals attraction. In turn, pH determines the charge of a particle, which changes from negative at high pH to positive at low pH (the transition point is called the isoelectric point, IEP, which takes place around the salinity of seawater in many clays). Combining the two regions in pH and concentration results in four states and transition regions. SOURCE: Modified from Santamarina et al., 2001.

Suggested Citation:"3 Meeting the Challenges With New Technologies and Tools." National Research Council. 2006. Geological and Geotechnical Engineering in the New Millennium: Opportunities for Research and Technological Innovation. Washington, DC: The National Academies Press. doi: 10.17226/11558.
×

imagined that will radically change practice. For example, imagine building clay liners, clay cores, and soil bases using engineered high-surface-area mineral particles consolidated from controlled self-assembled clay aggregates to obtain macroscale behavior resulting from exceptional mechanical properties (e.g., very high ductility); external friction control to facilitate compaction while increasing long-term strength, fluid-sensitive porous membranes, as well as special and unique chemical properties (e.g., specie-selective diffusion); engineered wetting conditions such as in NanoTurf; altered phase equilibrium for fluids in small pores; and specified electrical properties (e.g., exceptional magnetic and polar properties). Some of these developments are already taking place, for example, in the engineering of kaolin and precipitated carbonates for the paper coating and paint industries.

Nanoparticles might also be engineered to act as functional nanosensors and devices that can be extensively mixed in the soil mass or used as smart tracers for in situ chemical analysis, characterization of groundwater flow, and determination of fracture connectivity, among other field applications.

Although some of these applications seem almost magical in their potential, and many of those we can imagine will face some major unanticipated difficulties in reaching application, it behooves the geoengineering community to explore the possibilities of how the nanoscale material we know as soil can benefit from the nanoscale knowledge and new materials that are being developed by our colleagues in other disciplines.

3.3 SENSORS AND SENSING SYSTEM TECHNOLOGIES

3.3.1 Background

Microelectromechanical systems (MEMS) integrate mechanical elements, sensors, actuators, and electronics on a common silicon substrate using microfabrication technology, as described in Sidebar 3.2. Recent technological advancements in materials science, microfabrication

Suggested Citation:"3 Meeting the Challenges With New Technologies and Tools." National Research Council. 2006. Geological and Geotechnical Engineering in the New Millennium: Opportunities for Research and Technological Innovation. Washington, DC: The National Academies Press. doi: 10.17226/11558.
×

of MEMS, and bioengineered systems have made the dream of inexpensive, powerful, and ubiquitous sensing an achievable reality for many applications. Potential examples of such applications include (1) smart airframes that can adapt their performance to applied stresses and movements and self-evaluating buildings and infrastructure that can assess their condition and provide real-time responses for natural hazard mitigation and (2) data acquisition for weather forecasting and self-organizing energy systems. These applications will probably require that MEMS-based sensors integrate with networking and computational capabilities.

The assembly techniques used to build MEMS (described in Sidebar 3.2) are based on the accretionary and etching technologies commonly used by the integrated electronics circuit industry, which allow for involved micron-scale machining. The basic material used, silicon, has excellent structural properties. It is easy to add complementary metal oxide semiconductor (CMOS) circuitry directly onto the silicon to form very small, low-power-consumption, accurate, and rugged sensing devices. For example, the Sensirion barometer module for atmospheric pressure measurement is only 5 mm × 5 mm × 3 mm and has integral linearization, temperature compensation, 16-bit analog to digital conversion, and a common digital interface. In mass production the cost of such a device is typically only a few dollars.

Common to all advanced sensing systems is the vast amount of data generated. Processing these data encourages development of sensor systems that preprocess data in order to return decisions and information directly to the user. Traditionally deployed sensors are a collection of individual components in which the data collected must be processed by additional hardware downstream. Networks containing preprocessing sensors could become powerful, dynamic, and user-friendly in comparison to the traditional sensor data.

Wireless communication offers important advantages in the development of sensing systems. A generic wireless sensor platform includes an antenna, a power supply, a transceiver, signal processing circuitry, and a microprocessor to run the sensing and networking software. Each of

Suggested Citation:"3 Meeting the Challenges With New Technologies and Tools." National Research Council. 2006. Geological and Geotechnical Engineering in the New Millennium: Opportunities for Research and Technological Innovation. Washington, DC: The National Academies Press. doi: 10.17226/11558.
×

SIDEBAR 3.2
What Are MEMS?

The following description of MEMS was taken from the MEMS and Nanotechnology Exchange at http://www.memsnet.org/mems/what-is.html:

Microelectromechanical systems (MEMS) integrate mechanical elements, sensors, actuators, and electronics on a common silicon substrate through microfabrication technology. While the electronics are fabricated using integrated circuit process sequences (e.g., CMOS, Bipolar, or BICMOS processes), the micromechanical components are fabricated using compatible micromachining processes that selectively etch away parts of the silicon wafer or add new structural layers to form the mechanical and electromechanical devices.

MEMS promise to revolutionize nearly every product category by bringing together silicon-based microelectronics with micromachining technology, making possible the realization of complete systems-on-a-chip. MEMS are an enabling technology allowing the development of smart products, augmenting the computational ability of microelectronics with the perception and control capabilities of microsensors and microactuators and expanding the space of possible designs and applications.

Microelectronic integrated circuits can be thought of as the brains of a system and MEMS augment this decision-making capability with eyes and arms to allow microsystems to sense and control the environment. Sensors gather information from the environment by measuring mechanical, thermal, biological, chemical, optical, and magnetic phenomena. The electronics then process the information derived from the sensors and through some decision-making capability, the actuators respond with actions such as moving, positioning, regulating, pumping, or filtering, thereby controlling the environment for some desired outcome or purpose. Because MEMS devices are manufactured using batch fabrication techniques similar to those used for integrated circuits, unprecedented levels of functionality, reliability, and sophistication can be placed on a small silicon chip at a relatively low cost.

SOURCE: Courtesy of MEMS and Nanotechnology Exchange, http://www.memsnet.org/mems/what-is.html.

Suggested Citation:"3 Meeting the Challenges With New Technologies and Tools." National Research Council. 2006. Geological and Geotechnical Engineering in the New Millennium: Opportunities for Research and Technological Innovation. Washington, DC: The National Academies Press. doi: 10.17226/11558.
×

FIGURE: A MEMS gyroscope is shown as it (a) appears to the end user (as an integrated circuit [IC]), (b) the die within the chip and the micromachine within the die, and (c) a detail of the packaged die. This gyroscope has many common mechanical elements, and measures rate of twist around the normal to the plane of the device. The center of the gyro is a mass suspended on micromachined springs and damped by dashpots. The mass is resonated and the resultant Coriolis force, the same force that gives us the trade winds, is measured during motion (images courtesy of Andrei Shkel, University of California, Irvine).

Suggested Citation:"3 Meeting the Challenges With New Technologies and Tools." National Research Council. 2006. Geological and Geotechnical Engineering in the New Millennium: Opportunities for Research and Technological Innovation. Washington, DC: The National Academies Press. doi: 10.17226/11558.
×

these components presents design challenges and opportunities for MEMS applications. Limitations in wireless communication include power demand because radio frequency (RF) communication requires relatively large amounts of power compared to MEMS-based sensors; ensuring privacy of the data transmission; poor quality of low-power RF transmission that is susceptible to failure by seemingly insignificant changes in surroundings; and limited data transmission rates over low-power RF networks compared to the simplest wired bus. Furthermore, RF signals cannot be broadcast through soil, which limits their applications in geoengineering.

The very convergence of new sensor technologies, communications, and computing creates new potential. With the simultaneous use of these technologies, geoengineers could collect data over large time and space scales in a variety of materials and environments, analyze these data in situ, and make highly informed engineering decisions. Ultimately, the sensor and system (network) technology and devices must be inexpensive enough to allow their use in great numbers. Furthermore, the sensing systems must be easy to deploy, configure, and maintain so that researchers from disciplines other than computer science or electrical engineering can use them.

Current research themes in the Sensors and Sensor Networks Initiative at NSF (Liu and Tomizuka, 2003) involve sensor design for such purposes as biomimetic (life mimicking) applications, toxic agent detection, chip-based sensing systems, remote activation and interrogation, and self-calibration; sensor arrays and networks for multisensor monitoring, information transfer, ultralow power nodes, data management, distributed network control, and smart devices that self-assemble into networks; and information interpretation and use for decision and feedback, sampling, location optimization, monitoring, and diagnostic tools. MEMS research problems include identifying the optimal physical location of sensors to gather independent and complementary data, quantifying the uncertainties involved in measurements, developing autocalibration strategies, and validating sensor output using independent measurements.

Suggested Citation:"3 Meeting the Challenges With New Technologies and Tools." National Research Council. 2006. Geological and Geotechnical Engineering in the New Millennium: Opportunities for Research and Technological Innovation. Washington, DC: The National Academies Press. doi: 10.17226/11558.
×

Data interpretation requires knowledge of the uncertainties involved in taking the measurement. Hardware solutions to this problem must include autocalibration so that rational estimates of uncertainty can be made. System solutions must include sensor output validation with independent measurements and predictive modeling. The massive amounts of data that sensors gather must be manageable and interpretable to have any value. The user wants information, not numbers. One approach is to synthesize design models with the data to be collected (i.e., use sensing as a link between the real world and an abstract world). This synthesis leads to adaptive data interrogation systems.

Additional information on sensors and sensing systems is given in Kovacs (1998), Madou (2002), Petersen (1982), Elwenspoek and Wiegerink (2001), Ristic (1994), and Senturia (2001).

3.3.2 Sensing Systems and Geoengineering

Unobtrusive, smart, and inexpensive monitoring of geostructures can help greatly in providing knowledge and characterization of Earth through the four dimensions: the three spatial dimensions and time. Micron-scale sensors are being produced that measure displacements, strain, strain rate, tilt, location, species of gas and fluids, temperature, relative humidity, water content, fluid pressure, light intensity and spectral content, fracture growth, and other mechanical and chemical parameters. The integration of these new sensor technologies and systems into geoengineering research and practice must take into consideration the high cost of developing new sensors and sensor networks. Consequently, it is important to consider the use and adaptation of commercial off-the-shelf devices for geoengineering applications whenever possible.

The continuing revolution in sensing technology enhances our ability to see into Earth (NRC, 2000). The new technologies have dense sensor arrays that provide an order-of-magnitude increase in overall sensitivity over what was previously possible. These sensor arrays will have to be based on wireless communication and must incorporate in situ data

Suggested Citation:"3 Meeting the Challenges With New Technologies and Tools." National Research Council. 2006. Geological and Geotechnical Engineering in the New Millennium: Opportunities for Research and Technological Innovation. Washington, DC: The National Academies Press. doi: 10.17226/11558.
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reduction to minimize bandwidth requirements if they are to be practical. Potential users must consider the inherent physical limitations, such as the penetration depth of radio frequency signals through geomaterials.

Advanced information technology will allow adaptive arrays that can function and react on multiple scales without direct human intervention. Advances in sensors and sensing systems complemented with information technologies will allow advances in multivariate sensing and multiconstrained inversions. Imagine a dense dataset compiled from such methods as seismic, electromagnetic, gravitational, magnetic, and streaming potential. Each type of data contributes independent information. Together, these datasets can provide a comprehensive image of the subsurface, including the distribution of utilities and the spatial variability of the soil mass or rock structure.

Fiber optic seismic sensors are now available for boreholes that allow high-resolution imaging of the subsurface without interfering with the borehole. MEMS-based three-component accelerometers can provide high-accuracy digital data. High-resolution geophysical testing is complemented with microdrilling technology, which drills holes as small as 1.25 in to depths of 500 ft with the potential to maintain that hole size to depths of 5,000 ft (Shirley, 2003). The Badger Explorer (Bradbury, 2004) is a new rigless, battery-powered drill that carries sensors directly into the subsurface, collects data, and transmits the data to the surface. It measures shale volume, water saturation, porosity, bulk density, pore pressure, temperature, and acoustic velocity. In the coming decade, integration of autonomous sensing, computing, and communications systems—such as Smart Dust (http://robotics.eecs.berkeley.edu/~pister/SmartDust/) and downhole fiber optic, MEMS, or nanosensors—will be combined with information management technology to take us to a new level of data gathering and interpretation (also see Pister, 2003).

We can imagine geoengineering applications such as real-time monitoring of geostructures during occurrence of natural hazards (e.g., hurricanes, floods, and earthquakes) and the instrumentation of an earthfill dam with a network of devices so small that they do not have a structural effect but so ubiquitous that we can monitor seepage, piping,

Suggested Citation:"3 Meeting the Challenges With New Technologies and Tools." National Research Council. 2006. Geological and Geotechnical Engineering in the New Millennium: Opportunities for Research and Technological Innovation. Washington, DC: The National Academies Press. doi: 10.17226/11558.
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displacements, and dislocations throughout the structure in real time. If enough information can be gathered and analyzed in near-real time, it may be possible to deploy self-sealing technology to waste containment barriers where they are leaking, know where strain is accumulating along a fault zone to provide advance warning of seismic events, and image ahead of an advancing drill bit or tunnel machine to identify obstructions and hazards before they are encountered.

Integration of advances in wired and wireless communications protocols and hardware will put geoengineers in an entirely different position with respect to design and problem solving. Traditional geoengineering is predicated on not having complete knowledge of the underground. If the promise of MEMS is met, geoengineers could have the opposite problem of having more data than they know what to do with. Learning to use massive amounts of detailed information effectively and inexpensively could even introduce new challenges.

3.3.3 Human Factors

While this section of the report has focused on the potential contributions to geoengineering from new sensing tools, the importance of human factors in applying these tools and technologies cannot be overlooked. For instance, successful application of any monitoring program, whether using old established technology or new innovative sensors and networked instrumentation systems, depends on a variety of seemingly mundane tasks, including procurement, calibration, and acceptance of hardware and software, installation and baseline monitoring of equipment, maintenance and recalibration as needed, data collection and processing, and data interpretation with response actions as warranted. Without these steps, even the most advanced and sensitive instrumentation and monitoring system in the world could be rendered useless. While some of these functions can be built into a monitoring system (e.g., self-calibration, automated data collection and reduction), human interaction will still be required for proper interpretation and response.

Suggested Citation:"3 Meeting the Challenges With New Technologies and Tools." National Research Council. 2006. Geological and Geotechnical Engineering in the New Millennium: Opportunities for Research and Technological Innovation. Washington, DC: The National Academies Press. doi: 10.17226/11558.
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3.4 GEOPHYSICAL METHODS

3.4.1 Background

Geophysical sensing involves using techniques deployed from the ground surface or a borehole to define soil and rock profiles and to determine physical, chemical, or biological properties of Earth materials. Geophysical sensing can be employed for infrastructure-related characterization, resource development (hydrocarbon, mineral, and water), and monitoring processes (construction, remediation). Most geophysical methods are based on detecting a physical property contrast in space or time. The target must have sufficient size or contrast to be detectable by the geophysical sensor, and there is an inherent tradeoff between resolution and target depth. Although geophysical measurements are often conducted at a boundary, they can be processed using inversion techniques to infer the field of the parameter away from the boundary.

An overview of geophysical methods and their underlying principles is presented in Table 3.3. These methods generally provide independent

TABLE 3.3 Geophysical Methods

METHOD

PRINCIPLE

TYPICAL MEASUREMENT

PHYSICAL PROPERTY MEASURED

INTERPRETED PARAMETERS

Airborne sensing

Detects reflected electromagnetic radiation

Aerial photography and remote sensing in several spectral bands

Spectral-dependent reflectance of electromagnetic radiation

Geologic lineations, variations in vegetation, surface disturbances

Electrical and electromagnetic

Detects current flow in subsurface materials

Currents, voltages, spatial locations

Electrical resistivity

Depth, Earth material resistivity, porosity, inferred fluid chemistry

Suggested Citation:"3 Meeting the Challenges With New Technologies and Tools." National Research Council. 2006. Geological and Geotechnical Engineering in the New Millennium: Opportunities for Research and Technological Innovation. Washington, DC: The National Academies Press. doi: 10.17226/11558.
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METHOD

PRINCIPLE

TYPICAL MEASUREMENT

PHYSICAL PROPERTY MEASURED

INTERPRETED PARAMETERS

Ground-penetrating radar

Transmits radio waves in the 10 MHz to 500 MHz band into subsurface and detects returning reflected waves

Distance, wave arrival times, and wave amplitude

Dielectric permittivity, electrical resistivity, magnetic susceptibility

Shallow interface depth and geometry, electromagnetic wave speed, electromagnetic wave attenuation

Magnetics

Detects local variations in Earth’s magnetic field caused by magnetic properties of subsurface materials

Proton precession frequency

Magnetic susceptibility

Geometry and magnetic susceptibility of local subsurface features

Microgravity

Detects localized minute variations in the gravitational field of Earth

Displacement of a gravitational- force-sensitive mass

Mass density

Depth, geometry, and density of local subsurface features

Seismic methods

Source of seismic waves provides sampling of elastic properties in a localized volume of Earth

Distance, wave arrival time, and wave amplitude, different wave types

Speeds of compressional, shear, and surface waves; attenuation of these waves

Interface depth and geometry, elastic moduli, location of faults

Thermal methodsa

Measures temperature and changes related to active or passive thermal sources

Temperature and temperature changes at specific locations

Thermal conduction, heat capacity

Density, moisture content, thermal anomalies, thermal sources, rate of geochemical reactions

a Thermal methods added for this report.

SOURCE: NRC (2000, 2001b).

Suggested Citation:"3 Meeting the Challenges With New Technologies and Tools." National Research Council. 2006. Geological and Geotechnical Engineering in the New Millennium: Opportunities for Research and Technological Innovation. Washington, DC: The National Academies Press. doi: 10.17226/11558.
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information, which is analogous to the complementary nature of human senses, such as hearing (elastic waves) and seeing (electromagnetic waves). With respect to geoengineering, corresponding geophysical techniques (e.g., seismic methods and ground-penetrating radar) provide complementary information as well. It follows from this analogy that the best approach to looking into Earth is to use several different methods (including traditional geoengineering invasive techniques) and to consider the multiple constraints imposed by the results to limit and guide the inversion and interpretation process. In all cases, interpretation of the data requires proper understanding of the physical, chemical, or biological properties of Earth materials and their impact on the measured physical property.

The relationship of geophysics to geoengineering may be viewed from the perspective of the relationship of imaging technology to medical diagnosis. From this perspective the revolution in noninvasive medical diagnostic technology provides a guiding example for the geoengineering community, because it faces equally challenging diagnostic problems. Current medical imaging technology, such as computer-aided tomography (CAT), positron emission tomography (PET), magnetic resonance imaging (MRI), and ultrasound, can render both high-resolution and high-speed images that allow monitoring of subsecond-scale processes such as heartbeats. Recent extensions of medical imaging technology to the field of material science include very-high-resolution MRI and microcomputed tomography with micron-scale resolution. Additional information on geophysical methods, principles, and applications is given in Ward (1990), Yilmaz (1987), Telford et al. (1990), Aki and Richards (2002), and the Society of Exploration Geophysicists website (http://seg.org/publications/opubs/).

3.4.2 Geophysics and Geoengineering

The balance between the use of noninvasive geophysical methods and traditional invasive subsurface investigation methods reflects in part the cost of needed information that can be gathered with each technique.

Suggested Citation:"3 Meeting the Challenges With New Technologies and Tools." National Research Council. 2006. Geological and Geotechnical Engineering in the New Millennium: Opportunities for Research and Technological Innovation. Washington, DC: The National Academies Press. doi: 10.17226/11558.
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This balance is different in geoengineering applications from that in medicine, mining, or petroleum applications (as suggested in Table 3.4), which may explain in part the delayed adoption of geophysical methods in geotechnical practice. In medicine the shapes, locations, and properties of the organs are usually known, and they can be imaged from all sides. In geoengineering applications there is limited access and the components of the systems, as well as the properties of the components, are not well known. Therefore, medical imaging is much more accurate than geoengineering imaging.

In addition, complexities in processing geophysical data associated with underlying physical concepts, mathematical modeling and inversion, and final interpretation have further deterred the direct involvement of the geoengineering community in the development and application of geophysical methods for near-surface applications. However, new, efficient geophysical sensing devices coupled with versatile modeling and inversion software that can run on personal computers facilitate the application of geophysical techniques and permit the real-time visualiza-

TABLE 3.4 Cost of Information Versus Extent of Application of Invasive and Noninvasive Methods in Various Fields

APPLICATION (MAIN CONSTRAINT)

RELATIVE COST OF INFORMATION (INVASIVE / NONINVASIVE)

CURRENT PRACTICE

Petroleum

(target thousands of meters deep)

Very high

Mostly noninvasive

Medicine

(human life)

High

Mostly noninvasive

Mining

(aerial extent)

Intermediate

Mixed methods

Geoengineering

(near surface, limited aerial extent)

Low

Mostly invasive

Suggested Citation:"3 Meeting the Challenges With New Technologies and Tools." National Research Council. 2006. Geological and Geotechnical Engineering in the New Millennium: Opportunities for Research and Technological Innovation. Washington, DC: The National Academies Press. doi: 10.17226/11558.
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tion of subsurface conditions. These developments offer the promise of a shift in the balance between traditional invasive exploration techniques and geophysical methods.

Geophysical tools that can have the greatest impact on geotechnical engineering are related to

  • delineation of stratigraphy and subsurface variability, including the detection and characterization of small but significant geologic structures such as thin clay seams;

  • fracture network characterization in rock masses (dip, strike, spacing, condition) and soil classification and porosity (without nuclear sources);

  • degree of aging and diagenesis, assessment of fluid conditions (chemistry, saturation, pressure), and hydrogeological characteristics (including water table depth and variability in hydraulic conductivity);

  • small-strain parameters and anisotropy;

  • the values of effective stresses; and

  • detection and monitoring of movement of Earth and built structures.

As the presence and potential role of biological activity are recognized and better understood as important factors in geoengineering, geophysical sensing tools will be needed to assess metabolic activity and biomass distribution.

Wave propagation techniques based on electromagnetic waves (electromagnetic induction, ground-penetrating radar, and resistivity) or elastic waves (reflection, refraction, vertical seismic profiling, cross-hole, and spectral analysis of surface waves) are most efficient for near-surface applications. Electromagnetic methods provide information about the specific surface of the soil, the volume fraction of water, and the conductivity of the soil-water mixture. The effectiveness of noncontacting electromagnetic techniques remains unmatched by seismic methods; however, the limited penetration depth of electromagnetic waves in

Suggested Citation:"3 Meeting the Challenges With New Technologies and Tools." National Research Council. 2006. Geological and Geotechnical Engineering in the New Millennium: Opportunities for Research and Technological Innovation. Washington, DC: The National Academies Press. doi: 10.17226/11558.
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geomaterials often restricts their application. Sensor arrays (antennas for ground penetrating radar or coils in probes for electromagnetic surveys) have been coupled to state-of-the-art imaging and visualization software to produce very-high-resolution images of the near surface for utility detection in urban environments. Figure 3.5 presents an example of the application of high-resolution geophysical methods for locating subsurface utilities in West Palm Beach.

Seismic methods provide parameters that are more intimately related to the geomechanical properties of the subsurface than many of the other geophysical methods. For example, the shear S-wave velocity, Vs, is a direct measurement of the small strain shear stiffness, Gmax (knowing the mass density), and stiffness anisotropy. The primary compression or P-wave velocity, Vp, indicates proximity to full saturation (critical for

FIGURE 3.5 A plan-view 24-in depth-slice from imagery captured in downtown West Palm Beach, Florida, using radar tomography, an arrayed ground-penetrating radar technique used for shallow-subsurface 3-D surveying. This slice, which is one of 120 1-ft slices that make up a full “movie,” has all (regardless of depth) utilities found overlaid, color-coded by facility type. This is a combination of radar tomography’s two normally separate deliverables: PC video files and CAD drawings. (Copyright, Witten Technologies Inc.; used with permission.)

Suggested Citation:"3 Meeting the Challenges With New Technologies and Tools." National Research Council. 2006. Geological and Geotechnical Engineering in the New Millennium: Opportunities for Research and Technological Innovation. Washington, DC: The National Academies Press. doi: 10.17226/11558.
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pore water pressure generation and liquefaction); when the soil is fully saturated, Vp and Vs can be used to infer porosity.

The importance of Gmax in geomechanics stems from its ability to assess the skeletal stiffness even under saturated soil conditions. Seismic measurements of Gmax can also detect the effects of aging and diagenesis on soil structure, effects that are destroyed by penetration-based testing or during sampling. Therefore, Gmax measurements provide unparalleled information for cemented soil characterization, settlement computation, and even as an indicator of liquefaction potential (in particular for coarse deposits such as gravelly alluvium, where penetration testing can be either impossible or unreliable). Imagine deploying tomographic S-wave velocity systems beneath foundation systems prior to construction, behind retaining walls prior to excavation or in cross-sections prior to tunneling, and monitoring the evolution of soil stiffness (through changes in mean effective stress or loss of cementation) to help assess and monitor soil-structure interaction and its evolution in time.

There are important potential applications of geophysical techniques in laboratory studies as well. Imagine running a centrifuge-modeling experiment and assessing the evolution of the soil mass in the model with nonintrusive tomographic techniques; or monitoring the evolution of soil processes in laboratory cells while simultaneously gathering information with elastic and electromagnetic waves without perturbing the process (consider for example: consolidation, cementation, liquefaction, freezing, remediation, biomediated geochemical stabilization). Imagine using microtomographers (CAT and MRI) developed in medicine and material science to explore fabric evolution, mixed fluid flow, strain localization, and other microscale phenomena during laboratory testing. Imagine being able to determine the velocity and flux of fluids (water, oil, gas, injected CO2) in the field without having to drill boreholes. These are not esoteric concepts; prototypes of such devices are already available and ready to be explored to address geoengineering needs.

Important research needs remain for near-surface geophysical technology, including better understanding of the effects of mechanical, electrical, chemical, thermal, and biological processes on geophysical and

Suggested Citation:"3 Meeting the Challenges With New Technologies and Tools." National Research Council. 2006. Geological and Geotechnical Engineering in the New Millennium: Opportunities for Research and Technological Innovation. Washington, DC: The National Academies Press. doi: 10.17226/11558.
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geotechnical parameters; the optimization of sensors and sources (arrays, permanent sensor deployment, embedded sensors in natural and built environments, sensor reliability, calibration, communication, power requirements, control, and data transmission); and adequate processing algorithms that reveal the inherent high gradients in stiffness, porosity, and saturation conditions in the near surface. These new techniques must address the need for high resolution compatible with engineering applications, the complementary nature of multiple geophysical methods, and the need for ground truth provided by invasive techniques.

3.5 REMOTE SENSING

3.5.1 Background

Remote sensing techniques involve noncontact observation, measurement, and recording from an airborne or space platform of electromagnetic energy reflected by or emitted from a target. Passive systems measure energy that is reflected or transmitted from an object on Earth’s surface back to the sensor (e.g., satellites that record visible, near-infrared and thermal infrared wavelengths), whereas active systems generate energy and record the reflection from the body that it strikes (e.g., radar). The digital images captured by remote sensing systems can be manipulated and enhanced to highlight subtle features, such as vegetation type and density, water turbidity or pollutants, lithology and mineralogy, soil type and moisture, and many more features.

Space-based remote sensing systems deployed by governments or commercial enterprises are designed to make measurements of the land, atmosphere, and oceans. Starting with the Landsat series in 1973, a variety of space-based remote sensing systems have been deployed by the United States, Russia, India, Japan, and Canada. Numerous commercial remote sensing systems are now available.

The oil exploration industry offers an example of the potential for broader application of remote sensing in solving geoengineering problems. The demand for better petroleum reservoir characterization and manage-

Suggested Citation:"3 Meeting the Challenges With New Technologies and Tools." National Research Council. 2006. Geological and Geotechnical Engineering in the New Millennium: Opportunities for Research and Technological Innovation. Washington, DC: The National Academies Press. doi: 10.17226/11558.
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ment has transformed geophysics from an exploration tool to a drilling, development, and management tool. Some of the newer technologies have applicability to depths and scales important in geoengineering, and include time-lapse seismic imaging, measurement while drilling, geosteering for directional (e.g., lateral) well drilling, multicomponent seismic acquisition and processing (P-waves and S-waves in multiple directions), passive seismic monitoring, multifrequency and spectral measurements, through-casing borehole logging tools, and a wide variety of automated and semiautomated processing techniques involving artificial intelligence and advanced mathematical algorithms.

Visualization of large, complex datasets gathered by remote sensing can have a tremendous impact on our ability to understand, predict, and manage the subsurface. Development of software for visualization and management of these large data streams requires collaboration of interdisciplinary technical teams (engineers, geologists, geophysicists). Rapid simulation software allows what-if scenarios to be played out in advance. Autonomic computing involving the self-management, self-optimizing, self-configuring, self-healing, and self-protecting of data assets is only a few years from reality. But all these developments require very high data storage and computation power (see the section on information technology below).

Additional information on remote sensing and geoengineering applications is given by Short and Bolton (2004).

3.5.2 Remote Sensing and Geoengineering

The spatial and topographic resolution that can be attained with current remote sensing technology is relevant to many geoengineering applications. Two examples follow.

Synthetic aperture radar (SAR) uses antennas mounted on spaceborne, airborne, or ground-based carriers to generate high-resolution images by repeating measurements at selected spatial intervals along a straight trajectory. Attainable resolution is from 10 m to 25 m for satellite-based systems and from 1 m to 3 m for airborne systems.

Suggested Citation:"3 Meeting the Challenges With New Technologies and Tools." National Research Council. 2006. Geological and Geotechnical Engineering in the New Millennium: Opportunities for Research and Technological Innovation. Washington, DC: The National Academies Press. doi: 10.17226/11558.
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SAR data consists of a grid of complex numbers (amplitude and phase); two SAR images gathered at different times can be compared to produce interferograms that display phase difference (i.e., changes in elevation). Spaceborne interferometric synthetic aperture radar (InSAR) can determine displacement as small as a few millimeters over hundreds of square miles. Interference images gathered with synthetic aperture radar are shown in Figure 3.6, with applications to ground subsidence and tectonic displacements. InSAR technology has started to see some commercial applications (e.g., detection and monitoring of ground subsidence due to groundwater extraction in Phoenix). However, the technology is not widely accessible to the practicing geotechnical engineer. Making remote sensing technologies more accessible through research, development, and training will facilitate both advancement of technology and application to engineering practice.

Light detection and ranging (LIDAR) is an exciting new development in remote sensing that can provide very-high-resolution imagery of geologic features by measuring the time it takes for a laser pulse to travel roundtrip from the laser source to a target and back to a sensor. LIDAR

FIGURE 3.6 Synthetic aperture radar interferograms. (a) Ground surface subsidence induced by changes in groundwater in Phoenix, Arizona (Tatlow and Buckley, 2003; used with permission). (b) Tectonic displacement field after the 1994 Northridge earthquake (image courtesy of Gilles Peltzer, University of California, Los Angeles; used with permission).

Suggested Citation:"3 Meeting the Challenges With New Technologies and Tools." National Research Council. 2006. Geological and Geotechnical Engineering in the New Millennium: Opportunities for Research and Technological Innovation. Washington, DC: The National Academies Press. doi: 10.17226/11558.
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has traditionally been employed from satellites and aircraft but can also be employed from a fixed station on the ground. LIDAR can produce high-resolution topographic maps over large areas with grid spacings as little as 0.3 m (see Figure 3.7). In forest terrain, LIDAR-based terrain maps can be more revealing than high-resolution photographs (NRC, 2004d). In urban areas recent advances in photogrammetry offer enhanced resolution in interpretation of high-resolution aerial photography. Landslide hazard maps, flood plain assessments, landslide prediction, monitoring, slope stability in mines and road cuts, and coastal erosion are a few of the geotechnical engineering applications that have used this remote sensing technology.

Potential applications of remote sensing in geoengineering are related mainly to large-scale projects and regional activities and planning. Examples include hazard forecasting, monitoring regional subsidence, disaster response and recovery management, infrastructure planning, avalanches and regional instability, near-surface resource characterization and mining operation monitoring, and coastal erosion. Imagine the ability to monitor the movement of large, active landslide complexes from space-borne platforms with sufficient accuracy and frequency to

FIGURE 3.7 LIDAR 3-D topographic image of Pikes Peak. SOURCE: Data was developed using LIDAR methods by Merrick & Company in support of a project for El Paso County, Colorado. http://www.merrick.com/servicelines/gis/lidarsamples.aspx.

Suggested Citation:"3 Meeting the Challenges With New Technologies and Tools." National Research Council. 2006. Geological and Geotechnical Engineering in the New Millennium: Opportunities for Research and Technological Innovation. Washington, DC: The National Academies Press. doi: 10.17226/11558.
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detect accelerating movements that could eventually lead to a catastrophic failure. Near-real-time processing of the data could be linked with preset alarm levels to provide early warning of impending disaster in sufficient time for evacuation or other emergency action, and perhaps even allow for remedial action to prevent it. Imagine post-event damage surveys performed by space-borne platforms that could be used to direct response and recovery efforts in the immediate aftermath of a catastrophic event such as an earthquake or terrorist attack. These types of systems are within the realm of existing technologies, and could become reality with appropriate investment in research and development.

3.6 INFORMATION TECHNOLOGIES AND CYBERINFRASTRUCTURE

3.6.1 Background

The staggering increases in computing power and communications capabilities over the past 50 years have led to the development of information systems unimaginable just a few decades ago. The evolution in computer simulation capability since 1993 is shown in Figure 3.8. The growth in computer power has been driven by energy, scientific, and engineering applications, and especially by defense applications such as the Accelerated Strategic Computing Initiative (ASCI), a project started in 1996 to replace traditional nuclear testing by highly tuned, massive computer simulations (Messina, 1999).

As shown in Figure 3.8, the performance of supercomputers evolves rapidly. Today’s fastest computers perform up to 71 × 1012 floating-point operations per second. A list of the fastest computers can be found on the Web at http://www.top500.org. In November 2004, the fastest computer was the Department of Energy/IBM BlueGene/L beta system, which has the record benchmark performance of 70.72 Tflop/s (“teraflops,” or trillions of calculations per second). It is closely followed (51.87 Tflop/s) by the Columbia system built by Silicon Graphics and installed at the National Aeronautics and Space Administration Ames Research Center

Suggested Citation:"3 Meeting the Challenges With New Technologies and Tools." National Research Council. 2006. Geological and Geotechnical Engineering in the New Millennium: Opportunities for Research and Technological Innovation. Washington, DC: The National Academies Press. doi: 10.17226/11558.
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FIGURE 3.8 Evolution of fastest computer performance since 1993 (http://www.top500.org/lists/2004/11/PerformanceDevelopment.php).

in Mountain View, California. Both computers recently exceeded the performance of the Earth Simulator supercomputer (35.86 Tflop/s) in Yokohama, Japan, which was the fastest computer between 2002 and 2004. These supercomputers are clusters of thousands of processors (Earth Simulator involves 5,120 processors). Even with this computing power, large-scale problems are still based on crude material models and employ simplified geometry and boundary conditions. Spatially varying material properties and geometries representative of actual in situ conditions would result in problems too large and complex for modern computers.

The integration of computer technology and communication networks has made distributed information systems possible. Unlike conventional networks that focus on communications among devices, the Grid harnesses unused processing cycles of all computers in a network for solving problems too intensive for any stand-alone machine. Grid

Suggested Citation:"3 Meeting the Challenges With New Technologies and Tools." National Research Council. 2006. Geological and Geotechnical Engineering in the New Millennium: Opportunities for Research and Technological Innovation. Washington, DC: The National Academies Press. doi: 10.17226/11558.
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computing is intended to provide extraordinary computational power by dynamically linking high-performance computational resources over wide areas, thus balancing supply and demand. Many large-scale computer simulations now use the Grid (Foster and Kesselman, 1999).

In a related initiative NSF has recently launched a middleware project to enable the seamless federation of resources across networks. Middleware software is an evolving layer of services that connects two or more separate applications across the Internet or local area networks. It resides between the network and more traditional applications for managing security, access, and information exchange.

The Grid and middleware are examples of current developments of the cyberinfrastructure. The term “cyberinfrastructure” refers to the “system of information and communication technologies together with trained human resources and supporting service organizations that are increasingly required for the creation, dissemination, and preservation of data, information, and knowledge in the digital age” (Atkins et al., 2003). Cyberinfrastructure is an enabler of research. It is recognized that an advanced cyberinfrastructure can be the basis for revolutionizing the conduct of scientific and engineering research and education, and it can have broad impact in many other knowledge-intensive domains. The creation and usage of the cyberinfrastructure requires synergy among the computer science, engineering, and science research communities.

Extrapolating in large part from prior NSF investments in cyberinfrastructure (including high-performance computing, networking, middleware, and digital libraries, trends in the information technology industry, and the vision and innovation coming from many research communities), the NSF Blue-Ribbon Advisory Panel on Cyberinfrastructure asserted in 2003 (http://www.cise.nsf.gov/sci/reports/toc.htm) that the capacity of information technology has crossed thresholds that now make possible a comprehensive cyberinfrastructure on which to build new types of scientific and engineering knowledge environments and organizations and to pursue research in new ways and with increased efficacy. Such environments and organizations enabled by cyberinfrastructure are increasingly required to address national and global priorities

Suggested Citation:"3 Meeting the Challenges With New Technologies and Tools." National Research Council. 2006. Geological and Geotechnical Engineering in the New Millennium: Opportunities for Research and Technological Innovation. Washington, DC: The National Academies Press. doi: 10.17226/11558.
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such as global climate change, protecting our natural environment, applying genomics and proteomics to human health, maintaining national security, mastering the world of nanotechnology, predicting and protecting against natural and human disasters, as well as to address some of our most fundamental intellectual questions, such as the formation of the universe and the fundamental character of matter. For additional information on information technology and cyberinfrastructure, see NRC (1993, 2001b,c).

3.6.2 Information Technology and Geoengineering

The importance of information systems and technology to advances in geoengineering cannot be overstated. Geoengineers will need to understand, implement, and benefit from such technology at all scales. For example, it will not just be that geoengineers will need more information about urban systems; urban systems will become characterized at all levels by the development of information systems: smart materials, smart buildings, smart urban geoplatforms, smart infrastructure, and the like. The twenty-first century should see the advent of smart geosystems: geoengineered systems with information structures built into them. These systems will not just talk hierarchically (that is, to geoengineers), but they will also be self-referential: self-defining, self-diagnosing, and self-healing. This is where communications networks have already gone, and where other infrastructure systems are heading. This has implications not only for research and innovation but also for geoengineering curricula and professional practice. The profession must address not just geosensing and monitoring, but also the evolution of information-rich, self-referential geosystems.

The explosion in information technology offers the potential for added value from existing hardware and software systems as well as for development of new hardware and software. Many (perhaps most) existing monitoring and sensing systems are easily integrated into an information-rich smart system context. There are more than 1,600 catalogued computer programs specifically written to solve geoengineering

Suggested Citation:"3 Meeting the Challenges With New Technologies and Tools." National Research Council. 2006. Geological and Geotechnical Engineering in the New Millennium: Opportunities for Research and Technological Innovation. Washington, DC: The National Academies Press. doi: 10.17226/11558.
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problems in soil mechanics, rock mechanics, engineering geology, foundation engineering, hydrogeology, geoenvironmental engineering, and environmental engineering. Some of these programs are capable of solving very complex nonlinear problems, time-dependent dynamic phenomena, including combined mechanical-chemical-thermal-biological processes and complex construction sequences (tunnels, foundations, excavations). State-of-the-art examples of computational geoengineering are illustrated in Figure 3.9 for multiphase flow (oil, water, and gas) and pollutant dispersion followed by biochemical reactions. The figure also illustrates the power of result visualization when interpreting the results of large, complex simulations.

Advances in computational geoengineering have benefited from multidisciplinary collaborations. For example, the Seismic Performance for Urban Regions (SPUR) project is designed to simulate the effects of earthquakes on urban regions, and is the collective result of structural engineers, computer scientists, and seismologists (ERC, 2005). Based on a distributed simulation framework and on advanced computational and

FIGURE 3.9 Computer simulations. (a) Oil production: 3-D maps of an oil reservoir and the flow of oil, water, and gas through a complex porous medium. (b) Remediation: dispersion of pollutants in porous substrata where biochemical reactions are followed. Various species concentrations are shown using different colors. SOURCE: Oden et al. (2003). Reprinted with permission from Elsevier.

Suggested Citation:"3 Meeting the Challenges With New Technologies and Tools." National Research Council. 2006. Geological and Geotechnical Engineering in the New Millennium: Opportunities for Research and Technological Innovation. Washington, DC: The National Academies Press. doi: 10.17226/11558.
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visualization methods, SPUR permits forecasting and visualizing the extent and distribution of damage to buildings, bridges, and lifelines caused by earthquakes of different magnitudes and depths (see Figure 3.10).

Geoengineers work extensively with spatial data. Databases that have the capability to code, store, manipulate, and display spatial data are herein grouped under geographic information systems (GIS). These systems gain critical importance in facilitating the identification of patterns and trends, in extracting information from massive datasets, and through valuable analysis and management tools, which include two- and three-dimensional displays and extensive imbedded modeling capabilities

FIGURE 3.10 Seismic Performance for Urban Regions (SPUR) simulation of regional effects after a large earthquake. (a) This image shows the intensity of earthquake shaking that originates from a fault rupture at depth. SOURCE: Java-based Web interface for earthquake ground motion simulation. Web interface: Tomasz Haupt, Engineering Research Center, Mississippi State University. Visualization: Joerg Meyer, University of California at Irvine; used with permission. (b) Images represent buildings (tall rectangles) that respond to the earthquake ground motion propagating across the city. SOURCE: Ground motion and structural response simulation in a 3-D virtual environment. Prashant Chopra and Joerg Meyer, University of California at Irvine; used with permission. Available at http://imaging.eng.uci/~jmeyer/SPUR/.

Suggested Citation:"3 Meeting the Challenges With New Technologies and Tools." National Research Council. 2006. Geological and Geotechnical Engineering in the New Millennium: Opportunities for Research and Technological Innovation. Washington, DC: The National Academies Press. doi: 10.17226/11558.
×

(e.g., statistical, logical, mechanical). GIS technology not only supports the geoengineer but also facilitates communication between researchers, practitioners, and the public. Current developments are oriented toward fully exploiting the capabilities of GIS with new sensor technology to allow us to capture and manipulate three-dimensional time-varying data.

The integration of sensor technology in geophysical measurements discussed above with visualization tools and data management that can be scaled to the types of problems encountered in the broader field of geoengineering provides an example of the role of information technology. Imagine the application of hybrid systems that will extensively combine dense sensor arrays with computer models to drastically increase the availability of data and decrease uncertainty in geoengineering applications, and allow the rational consideration of all available subsurface data in real-time decision making. While current GIS technology may be employed for developing smart sensor networks for data management, to take full advantage of their database capability current two- and three-dimensional databases must evolve into true geologic data models in which data is stored and interpreted in a geologic context and with multidimensional modeling and interpretation capabilities integrated into the data management, manipulation, and display schemes.

In the future, geoengineering researchers and practitioners will be able to implement complex computer models and examine multiscale and multiphysics phenomena, examine the complete range of physical phenomena at all applicable spatial and temporal scales, integrate computational models with large datasets originating from dense sensor arrays and satellite remote sensing, and examine uncertainties of computer simulations through realistic modeling. They will be able to conduct these analyses and control laboratory and field testing remotely, in cooperation with other colleagues in interdisciplinary teams pulling together human, technological, and computational capabilities in the cyberinfrastructure. Information technology will enable geoengineers to mine and analyze the voluminous information produced by field and airborne sensors. Using advanced computer networks, geoengineers will query and scrutinize gigabytes of information. They will construct

Suggested Citation:"3 Meeting the Challenges With New Technologies and Tools." National Research Council. 2006. Geological and Geotechnical Engineering in the New Millennium: Opportunities for Research and Technological Innovation. Washington, DC: The National Academies Press. doi: 10.17226/11558.
×

efficiently realistic computer models of geoengineered structures that include detailed information on geometries and material properties. They will have a large digital library of in-depth case histories to train students in geoengineering. They will have the opportunities to make more educated real-time decisions based on the realistic computer simulations and rapid exchanges of information.

3.7 THE POTENTIAL OF THE NEW TECHNOLOGIES FOR ADVANCING GEOENGINEERING

A comprehensive and complete understanding of soils and rocks and the development of effective, efficient, and economical new solutions to problems in geoengineering must consider not only mechanical interactions but also interactions with all forms of energy: mechanical, thermal, chemical, and electrical. New ways of obtaining and processing information about soils and rocks have the potential to revolutionize our engineering capabilities. Some of the ways that the new technologies we have discussed in this chapter may make this happen are summarized in Table 3.5. Application of all these new technologies and the need to incorporate more electronics, biology, chemistry, material science, and information technology into geoengineering has major implications for education as well as practice, and these issues are discussed in Chapter 5.

The committee sees tremendous opportunities for advancing geoengineering through interaction with other disciplines, especially in the areas of biotechnology, nanotechnology, MEMS and microsensors, geosensing, information technology, cyberinfrastructure, and multispatial and multitemporal geographical data modeling, analysis, and visualization. Pilot projects with vertical integration of research of multiple disciplines—perhaps including industry, multiple government agencies, and multiple universities—should be explored as alternatives to more traditional interdisciplinary proposals.

The importance of the human factors discussed earlier in this chapter should not be neglected in the application of advanced technology, whether it be advanced sensors, geophysical exploration, remote sensing,

Suggested Citation:"3 Meeting the Challenges With New Technologies and Tools." National Research Council. 2006. Geological and Geotechnical Engineering in the New Millennium: Opportunities for Research and Technological Innovation. Washington, DC: The National Academies Press. doi: 10.17226/11558.
×

TABLE 3.5 The Potential of New Technologies to Advance Knowledge and Practice in Geotechnology

DISCIPLINE

POTENTIAL IMPACT ON GEOTECHNOLOGY

TIMING

REQUIRED KNOWLEDGE FOR GEOENGINEERS

Biotechnology

High

  • improved understanding of Earth material behavior

  • new construction materials

  • applications for in situ ground remediation of contaminated soil and groundwater will increase

  • passive methods for ground stabilization may be possible

  • better resource recovery methods may develop

Mature concepts permit high impact in the short-term.

 

  • biology

  • geochemistry

Nanotechnology

Medium to Low

  • nanotechnology is a recognized part of soil technology

  • enhanced understanding based on more study of reactions at the nanoscale

  • new materials and methods

  • solutions looking for problems at this stage?

Field in early stages of development. Its full impact in geotechnology should be expected in the long term.

 

  • physics

  • chemistry

Sensors and sensing systems

Medium to High

Depending on whether the promise of MEMS is met, MEMS developers should be connected to geotechnical problem solvers (see Chapter 5).

  • will require geoengineers to increase their knowledge of electronics

  • proper integration can revolutionize laboratory measurement through noninvasive sensing

  • can make geophysical methods cheaper and more pervasive

  • integration of development work by other industries essential

Revolutionary developments in progress. Sensors already available and systems can have high impact in the short term.

 

  • electronics

  • signal processing

  • inversion math

Suggested Citation:"3 Meeting the Challenges With New Technologies and Tools." National Research Council. 2006. Geological and Geotechnical Engineering in the New Millennium: Opportunities for Research and Technological Innovation. Washington, DC: The National Academies Press. doi: 10.17226/11558.
×

DISCIPLINE

POTENTIAL IMPACT ON GEOTECHNOLOGY

TIMING

REQUIRED KNOWLEDGE FOR GEOENGINEERS

Geophysical methods

High

  • will require increasing the benefit-cost ratio

  • noninvasive methods need more development

  • new data acquisition and processing methods enhance applicability

  • tomographic methods allow 3-D characterization

Revolutionary and mature tools available. Further emphasis on high-resolution near-surface characterization will have renewed impact in the mid-term.

 

  • electronics

  • signal processing

  • inversion math

Remote sensing

High

  • ongoing, fruitful area for research and development

  • ground-truthing observations remain a research issue

  • research could address the potential for real-time decision making

A new family of unprecedented tools will have significant impact in the short term.

 

  • signal processing

  • data management

  • computer science

Information technology

High

  • ongoing developments

  • provides a mechanism for collaboration

  • requires synergy among the computer science, engineering, and science research communities for fruition

  • aspire to 4-D GIS for real-time decision making

  • development of self-referential smart geosystems with built-in information structures

Its critical role in sensing systems, geophysics, and remote sensing will determine their impact in the short term. Smart infrastructure systems are already on the drawing board and under development. Existing geosensing and monitoring devices are available and ready for integration with these systems.

 

  • data management

  • computer science

Suggested Citation:"3 Meeting the Challenges With New Technologies and Tools." National Research Council. 2006. Geological and Geotechnical Engineering in the New Millennium: Opportunities for Research and Technological Innovation. Washington, DC: The National Academies Press. doi: 10.17226/11558.
×

information technology, or some other technological advancement. Such issues as procurement, calibration, validation, data collection, and data interpretation remain vital to successful implementation of new tools and technologies.

We conclude that many of the most important tools for achieving major advances in geoengineering are likely to come from forward-looking, creative, and inspired individuals working alone or with one or two colleagues in related disciplines. We urge, therefore, that NSF increase its investments in this type of research, including especially the support of a greater proportion of projects that may be classified as high risk but high reward.

Suggested Citation:"3 Meeting the Challenges With New Technologies and Tools." National Research Council. 2006. Geological and Geotechnical Engineering in the New Millennium: Opportunities for Research and Technological Innovation. Washington, DC: The National Academies Press. doi: 10.17226/11558.
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×
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×
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The field of geoengineering is at a crossroads where the path to high-tech solutions meets the path to expanding applications of geotechnology. In this report, the term "geoengineering" includes all types of engineering that deal with Earth materials, such as geotechnical engineering, geological engineering, hydrological engineering, and Earth-related parts of petroleum engineering and mining engineering. The rapid expansion of nanotechnology, biotechnology, and information technology begs the question of how these new approaches might come to play in developing better solutions for geotechnological problems.

This report presents a vision for the future of geotechnology aimed at National Science Foundation (NSF) program managers, the geological and geotechnical engineering community as a whole, and other interested parties, including Congress, federal and state agencies, industry, academia, and other stakeholders in geoengineering research. Some of the ideas may be close to reality whereas others may turn out to be elusive, but they all present possibilities to strive for and potential goals for the future. Geoengineers are poised to expand their roles and lead in finding solutions for modern Earth systems problems, such as global change, emissions-free energy supply, global water supply, and urban systems.

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