Development of the Geoconstruction Information and Technology Selection Guidance System (2014)

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30 C h a p t e r 5 Introduction An interactive selection system was developed to aid the user in identifying potential geoconstruction technologies for a user-defined set of project conditions. The interactive selec- tion system is a qualitative tool to assist the engineer in com- pleting a project-specific quantitative analysis and comparison of potential technologies. Quick solutions in geotechnical engineering are generally not found, and this system does not shortcut the proper formulation of a problem and assess the alternatives. This system does assist the user in identifying and sorting possible alternatives or geoconstruction technologies. The comparison and final selection of the geoconstruction technology(s) will require judgment of an experienced engi- neer on a project-by-project basis. The scope of the interactive selection system is limited to technologies applicable to one or more of the three elements of the project: new embankment and roadway construction over unstable soils, roadway and embankment widening, and stabilization of pavement working platforms. The system was initially developed along the lines of these three elements. However, the final system was developed for four transporta- tion applications, as noted under the first item in the follow- ing list. The objectives of this interactive selection system are: • Identify potential technologies for design and construction for the following transportation applications: 44 Construction over unstable soils 44 Construction over stable or stabilized soils 44 Geotechnical pavement components (base, subbase, and subgrade) 44 Working platforms. • Provide assistance to develop a short list of applicable technologies. • Provide guidance for detailed project-specific screening of technologies with consideration of SHRP 2 R02 objectives. • Provide an interactive, programmed system. • Provide current, up-to-date information in technology products and tools. The interactive selection system is represented in hard copy form through a series of flowcharts and tables. The flow- chart layout allows user-defined inputs, which lead to a series of tables. At points along the system, tables are listed that identify potential technologies. Thus, the “knowledge” of the appropriate technologies is contained in the tables and the “reasoning” or inference engine is formed through the user inputs, as outlined in the flowcharts. The method of flow- charts and tables facilitated the programming of a rule-based, automated system. The interactive selection system is a knowledge-based sys- tem. The simplest knowledge-based systems have two mod- ules: the knowledge base and the inference engine (Hopgood, 1993). The knowledge base is contained in the tables and the inference engine is shown graphically through flowcharts. Strategies for Development To support the goals and objectives of the R02 project, strate- gies for development of the selection procedure were estab- lished. The system was developed with input from the advisory panel, outside experts, and SHRP 2. Meetings were conducted throughout the project to bring together state agency trans- portation personnel; practitioners; contractors; and academ- ics who work with the relevant geotechnical materials, systems, and technology areas. The following guiding principles were established as a result of these meetings for the development of the selection system: • The procedure should be simple. • The process used for decision making should be transparent. • The system will conservatively remove potential technologies. Interactive Selection System

31 • The system will lead the user to a list of potential, unranked technologies. • The final selection of the appropriate technology will be the responsibility of the user. • The knowledge for potentially applicable technologies comes from the comprehensive technology summaries and Task 10 documents. The knowledge was supplemented with expert input from the project team and advisory board. the Knowledge “The most important process in a knowledge-based system is knowledge acquisition. How the knowledge is obtained and where it is obtained determines the usefulness of the system” (Fredlund et al., 1996). Knowledge for identifying potentially applicable technologies to a set of geotechnical and loading conditions (the selection system) comes from two sources: from the result of the research team’s work products and from experts on the research team and advisory board. research team Work products The research team’s work efforts included the development of comprehensive technology summaries (CTSs), design method assessments, and quality control and quality assurance (QC/ QA) procedure assessments for each of the technologies listed under SHRP 2 R02 Project Background in Chapter 1. CTS development entailed an in-depth technology overview that included advantages, potential disadvantages, applicable soil types, depth/height limits, groundwater conditions, material properties, project-specific constraints, equipment needs, and environmental considerations. Additionally, for each technol- ogy, case histories, design procedures, QC/QA procedures, and specifications were collected. The assessment efforts then quantitatively and qualitatively assessed the current design methods and QC/QA procedures. The development of these CTS and assessment documents provided significant technical information related to each tech- nology and the application of that technology with regard to geotechnical and loading conditions. FHWA manuals and guid- ance documents were identified in the CTS and assessment work efforts. These sources and other available information on the technologies were incorporated into the work products. expert Input from research team and advisory Board After developing the selection system, comprised of flowcharts and tables, the system was reviewed by the research team and advisory board members to obtain their expert input as to the applicability of certain technologies to certain condi- tions. Research team members had multiple opportunities to comment on the selection system. The advisory board had one opportunity to comment on the selection system on November 9, 2010. (The advisory board members are part of the proposed beta testing group, and will have an additional opportunity to comment then.) Comments from both the research team and advisory board have been tracked through the use of comment logs, which include the action taken on the comments. elimination of technologies In describing the process of the elimination of technologies during the selection procedure, the selection system should be considered a heuristic program. Intuition, experience, and judgment can be used to develop heuristic rules (Ignizio, 1991). Heuristics such as “Do you know a related problem?” require the recollection of previous projects (Baron, 1988). These rec- ollections from the experts were used to form the knowledge base for the selection system. Chameau and Santamarina (1989) found that a geotechnical expert’s comprehension of a problem is affected by a large number of factors, including those that are case-specific, context-dependent, and subjective. Geotechnical experts make decisions based upon the recollec- tion of previous cases, which is relevant in geotechnical engi- neering where an emphasis is placed on experience (Chameau and Santamarina, 1989). An acceptable solution(s) is generally sought, rather than the optimal solution. Heuristic programs are used to identify acceptable solutions. A general characteristic of many heuris- tics is the focus on screening, filtering, or pruning (Ignizio, 1991). Heuristics can be used to reduce the number of alter- natives that are considered. An expert typically learns through time and experience which solutions tend to work well and which solutions tend to work poorly. Thus, even though it is possible that a better solution might be missed, the appar- ently less-attractive solutions are eliminated in the selection process (Ignizio, 1991). The crux of viewing the selection sys- tem as a heuristic program is that the solution(s) identified as a result of using the selection system may or may not be the best or optimal solution. The best or optimal solution requires consideration of both technical and nontechnical project issues and constraints. In recognition of the ultimate responsibility for final tech- nology selection resting with the user, the following dis- claimer was developed for the selection system: The application of this selection system is the responsibility of the user. It is imperative that the responsible engineer under- stand the potential accuracy limitations of the program results, independently cross checks those results with other methods, and examines the reasonableness of the results with engineering knowledge and experience.

32 The research team, advisory board, and other stakeholders supported the development of a system that does not define the “best” or “most applicable” geotechnical technology or tech- nologies for a particular set of input parameters, but rather pro- vides a short list of potential technologies. Then the system leads the user to the catalog of technologies to provide the infor- mation for the user to complete a project-specific analysis. Fuzzy logic and probability theory were considered for use in the development of the interactive selection system. How- ever, a simpler rule-based system was chosen for the inter- active selection system to allow the system to be used by a wide range of technical and nontechnical users. Initial Inputs into Selection System As noted, the system was initially developed along the three R02 elements. A list of potential questions was generated initially and shown as follows as an indication of all the factors that may influence the selection of a geoconstruction technology. • What type of project is being constructed? • What is the size of the area needing improvement? • Are there any project constraints to be considered in select- ing a possible technology? • What is the soil type that needs to be improved? • To what depth do to the unstable soils extend? • At what depth do the unstable soils start? • Is there a “crust” at the ground surface? • What is the depth to the water table? • How much does the water table fluctuate? • What is the desired improvement? (i.e., decrease settlement, decrease construction time, or increase bearing capacity) • With what technologies does the user already have experience? • What is the geologic setting of the project? As the project progressed, other potential, nontechnical queries were also identified, such as: • Experience with geoconstruction technology? • Experienced contractors available in project area? • What materials are available for use on the project? • What is the schedule? Many meetings and discussions were held to discuss the first few steps of the interactive selection system. From these meetings, the initial input into the system will be through the selection of one of the four applications shown in Figure 5.1. Each application resulted in a unique set of inputs. A separate selection procedure has been developed for each application. Application 1, Construction over Unstable Soils, leads to a decision process for foundation soil improvement, reinforce- ment of the embankment, or reduction in load. Application 1 Figure 5.1. Illustration of four application areas for technologies.

33 includes ground improvement technologies to support embankments of any height over unstable soils. Application 2, Construction over Stable or Stabilized Soils, leads to a deci- sion process for construction over stable or stabilized soils. Application 2 is focused on topics pertaining to embankment construction. Application 3, Geotechnical Pavement Compo- nents, leads to a decision process for improving materials directly supporting the surface pavement. Application 4, Working Platforms, leads to technologies that can provide working platforms. Interactive Selection System The system operates in a step-by-step process through the answers to preset questions. The system was intentionally developed such that users must be able to answer the current Figure 5.2. Interactive Selection System web page. question before proceeding to the next question. The initial questions and order of the questions along each application represent the minimum information required to sort the geo- construction technologies. Examples of using the selection system are provided in Appendix A, User’s Guide to the Infor- mation and Guidance System. To begin the interactive selection system, the user selects one of the four application areas, as illustrated in Figure 5.2. In the selection system, the list of potentially applicable tech- nologies is shown on the right side of the page (see Figure 5.2), all of which are hot-linked to the respective technology pages. At the start of the selection process, as shown in Figure 5.2, all of the technologies in the system are shown in the right column. Upon selection of an application, the list of technologies in the right column will shorten to just a list of technologies that could potentially be used for that application. As additional decisions

34 are made, nonapplicable technologies are grayed out (fade). Both the remaining technologies and the grayed technologies on the right side are linked to their respective Technology Infor- mation web pages. After completion of the interactive selection system for any of the four applications, the user has the option to select Go to Selection Summary. This will open a new window that lists the user inputs, the potential technologies with the SHRP 2 R02 ratings, and provides a space to enter user-specific infor- mation. Within this window, the user will have the option to Create PDF, which generates a PDF documenting the inter- active selection system choices. The individual technologies shown as potential technologies within both the Selection System Summary window and the PDF are linked to the indi- vidual Technology Information pages on the Information and Guidance System website. A date stamp is automatically generated at the time of PDF generation. project-Specific technology Selection for Construction over Unstable Soils During project development, many possible queries were developed that provide further sorting of technologies. The flowchart and table system quickly became inefficient with the addition for further selections. To address this, the project- specific technology selection for construction over unstable soils tool was developed. The potential project-specific tech- nology selection inputs include the following: • Purpose of improvement(s). • Select project type. • Site characteristics. • Size of area to be improved. • Project constraint(s). • Select the best description of the construction or imple- mentation schedule. • Select unstable soil condition that best describes site. • Are sufficiently thick peat layers present that will affect construction and settlement? • If unstable fine-grained soils are present, do the unstable soils have a shear strength less than 500 psf? • Are water-bearing sands present in the soil to be improved? • Are any subsurface obstructions that would cause drilling difficulty, such as cobbles, boulders, buried tree trunks, or construction debris, present? This tool queries a large table with no associated flowcharts. This tool is an example of how the interactive selection sys- tem can be further refined.