Seeing into the Earth Noninvasive Characterization of the Shallow Subsurface for Environmental and Engineering Applications (2000) / Chapter Skim
Currently Skimming:
2 Why Characterize the Subsurface?
2 Why Characterize the Subsurface?
Pages 18-30
The Chapter Skim interface presents what we've algorithmically identified as the most significant single chunk of text within every page in the chapter.
Select key terms on the right to highlight them within pages of the chapter.
From page 18... ...
Characterization also commonly involves obtaining information about the processes that occur in the subsurface. These processes include the natural processes that form and modify the geological materials and the structure of the subsurface, and induced processes such as fluid pumping or injection.
|
From page 19... ...
In summary, noninvasive techniques are widely used in some resource exploration and well-integrated with the often more expensive drilling and direct sampling programs. GROUNDWATER CONTAMINATION AND REMEDIATION There is a growing concern about contaminated soil and groundwater, both from surface spills and from underground sources such as leaking storage tanks or landfill sites.
|
From page 20... ...
As discussed later, electromagnetic methods in some cases can directly detect inorganic contaminants, depending on the concentration of the contaminant and the geological setting. Direct detection of organic contaminants by noninvasive methods is considerably more challenging, with some reported success using resistivity sounding, ground penetrating radar (GPR)
|
From page 21... ...
Noninvasive methods have had some success in this area, as discussed in detail in Chapter 3. LAND MINES AND UNEXPLODED ORDNANCE Noninvasive techniques are frequently used to locate buried land mines and unexploded ordnance (UXO)
|
From page 22... ...
Lowmetal-content land mines make detection with magnetometers difficult if not impossible, whereas magnetometers are the common "tool of choice" for UXO detection (see Figure 2.2~. Locating land mines and UXO involves both invasive and noninvasive technologies.
|
From page 23... ...
The top figure is from a high-resolution magnetic survey over a contaminated World War II artillery range. Data were collected with an automated survey system consisting of an array of optically pumped magnetometer sensors combined with a differential Global Positioning System, operated from an all-terrain vehicle.
|
From page 24... ...
cites the needs for proper use of geophysics in locating underground utilities before digging, excavating, or drilling, and for statistics on inadequate implementation of geophysical sensing. It also states that "a single pipeline accident has the potential to cause a catastrophic disaster that can injure hundreds of persons, affect thousands more, and cost millions of dollars in terms of property damage, loss of work opportunity, ecological damage, and insurance liability." Typically about 70 such events occur in the United States every year (National Transportation Safety Board, 1997~.
|
From page 25... ...
the likelihood that these properties may change with time. Current limitations of noninvasive methods for geotechnical applications include the inability to define boundaries and identify material types with sufficient accuracy, the inability to analyze small volumes or zones that may have a critical importance (e.g., failure to detect small-scale heterogeneity)
|
From page 26... ...
Known air-filled cavities passing under the profile line are shown in the geological section. The gravity anomaly profile indicates a negative anomaly over the cavities and positive and negative anomalies correlating to limestone pinnacles and clay-filled pockets, respectively.
|
From page 27... ...
Traditional archaeological field research involves invasive methods such as the careful digging of pits and trenches to find, extract, and document artifacts. The time and cost involved in these methods have increased interest in the use of noninvasive techniques, particularly geophysical methods, to map archaeological sites and plan the locations of invasive sampling.
|
From page 28... ...
Rather than being restricted to a twodimensional exposed section of material at the surface or a one-dimensional sample of the earth obtained from drilling, noninvasive characterization provides a unique opportunity to study an undisturbed region of the earth. In addition, noninvasive technologies can provide continuous sampling of a region at a sam
|
From page 29... ...
Studies of sedimentary environments require a quantitative description of the spatial variability in hydraulic properties for modeling fluid flow in groundwater aquifers. Although detailed analyses of outcrops can provide direct measurements of variation in properties such as porosity and permeability, noninvasive techniques can characterize the three-dimensional spatial variability of a region.
|
From page 30... ...
, 1994. Unexploded ordnance advanced technology demonstration program at Jefferson Proving Ground (Phase I)
|
Key Terms
This material may be derived from roughly machine-read images, and so is provided only to facilitate research.
More
information on Chapter Skim is available.