Geotechnical Solutions for Soil Improvement, Rapid Embankment Construction, and Stabilization of the Pavement Working Platform (2012)

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13 C h a p t e r 3 Introduction The main product of the R02 project is a web-based informa- tion and guidance system for geotechnical solutions for trans- portation infrastructure. The web-based information and guidance system contains important information for the 46 geoconstruction technologies previously identified under Background in Chapter 2. This information allows for technol- ogy screening, applying, designing, cost estimating, specifying, and monitoring those technologies. The information and guidance system provides a compilation and toolkit of geo- technical information to address all phases of decision making, from planning to design to contract specifications to construc- tion, which will allow transportation projects to be built faster, to be less expensive, or to last longer. The website allows imme- diate and well-organized access to the results of the second Strategic Highway Research Program Renewal Project R02 (SHRP 2 R02) research project products. The title for the web- site, Geotechnical Solutions for Transportation Infrastructure, comes from the objectives associated with the SHRP 2 R02 project. The website is currently housed at http://www.intrans .iastate.edu/geotechsolutions/index.cfm. The information and guidance system has intentionally avoided endorsing certain geoconstruction technologies over others. To the extent possible, naming specific manufacturers and contractors has also been intentionally minimized. The intent of the system is to offer a means for evaluating a particu- lar geoconstruction technology. A thorough study of the infor- mation and guidance system should enable the user to assess where, when, and how a certain geoconstruction technology should be used. Two systems are referenced in this report. The first system is the web-based information and guidance system, which refers to the entire website and contains a vast amount of technical and nontechnical information and guidance. Within the infor- mation and guidance system, a dynamic interactive selection assistance tool has been developed. This is a knowledge-based decision support system that assists in identifying candidate technologies. The four primary components of the web-based informa- tion and guidance system are illustrated in Figure 3.1. The cata- log of technologies provides a listing of all the technologies with associated links to the products and tools for the respec- tive technologies. Technology selection contains a listing of technologies by classification and an interactive tool to identify candidate technologies for specific geoconstruction applica- tions using project information and constraints. Final technol- ogy selection requires project-specific engineering. Before technology selection, site-specific conditions and constraints must be identified. The geotechnical design process presents an overview of the considerations involved in evaluating site con- ditions and implementing a geoconstruction technology. This website contains technical terms and industry-specific jargon. Therefore, abbreviations and glossary terms have been com- piled to assist in understanding the acronyms and terminology used throughout this website and in its documents. Framework for the System The R02 web-based system provides a framework for using the technologies. “Information and guidance” refers to the entire web-based system that provides products and tools for use of the technologies. “Interactive selection assistance” refers to the portion of the website that assists the user in determining a list of candidate technologies for a specific set of project conditions. The objectives of the information and guidance website are to do the following: • Identify potential technologies for design and construction applicable to 44 Construction over unstable soils, 44 Construction over stable or stabilized soils, 44 Geotechnical pavement components (base, subbase, and subgrade), and 44 Working platforms. SHRP 2 R02 System

14 • Provide assistance to identify a short list of applicable technologies. • Provide guidance for detailed project-specific screening of technologies. • Provide an interactive, programmed system. • Provide up-to-date information in technology products and tools. The information and guidance website is simple, functional, and completely populated. The selection assistance tool guides a user to a short list of potential (unranked) technolo- gies. The entire system is updatable. The system was developed along the lines of the three ele- ments listed in Chapter 1; however, the final applications were divided into four areas, as shown in Figure 3.2. The sys- tem was developed with input from the research team mem- bers, the project advisory board, an expert contact group, FHWA, and SHRP 2. Meetings were conducted throughout the project to bring together STA personnel, practitioners, contractors, and academics who work with the relevant geo- technical materials, systems, and technology areas. These meetings provided valuable brainstorming opportunities to identify technical and nontechnical obstacles limiting wide- spread effective use of these technologies, best available opportunities for advancing the practice of existing and emerging technologies, and future directions of these tech- nologies in transportation works. Comments from these meetings assisted in developing the objectives, content, and details of the final system. The information for identifying technologies that may apply to a particular set of geotechnical and loading conditions comes from the R02 team’s work efforts, including the develop- ment of three source documents for each of the technologies Figure 3.1. Relationship of the four primary components of the information and guidance website. Information and guidance website Catalog of technologies Technology selection assistance Geotechnical design process Abbreviations and glossary Figure 3.2. Illustration of four application areas for the technologies. Construction over Unstable Soils Geotechnical Pavement Components (Base, Subbase, and Subgrade) Construction over Stable/Stabilized Soils EMBANKMENT SOLUTIONS ABOVE GRADE STABLE SOILS EMBANKMENT UNSTABLE SOILS SOLUTIONS ABOVE OR BELOW GRADE Working Platforms SUBGRADE SOILS GEOTECHNICAL PAVEMENT COMPONENTS (SOLUTIONS FOR BASE, SUBBASE, AND SUBGRADE) PAVEMENT SURFACE BASE SUBBASE STABLE SOILS WORKING PLATFORM SOLUTIONS UNSTABLE SOILS GROUND SURFACE UNSTABLE SOILS OR

15 listed under Background in Chapter 2. These source docu- ments are the comprehensive technology summary (CTS), the design quality control assessment (QC), and the design quality assurance (QA) assessment. The web-based system is programmed utilizing Adobe ColdFusion software in conjunction with a Microsoft Access database. This combination of software allowed the tables developed as part of the selection assistance tool to be ported to a database that can be dynamically queried via the web. The combination of Adobe ColdFusion and Microsoft Access provided these benefits: • Built-in searching, control, and backtracking mechanisms • An internal database to hold the knowledge base • Tools with windows, menus, frames, and drop boxes • The ability to house the system on a server and allow the program to be run by multiple users via the web Like most geotechnical analytical solutions, the guidance provided must be measured against the opinion of an expe- rienced geotechnical engineer practicing in the local area of the project. The selection assistance tool was developed with a “keep it simple” philosophy, using two approaches. The first approach is that the tool conservatively removes potentially inapplicable technologies during the process. The second approach, which is a common theme through- out the selection assistance procedure, is that the tool will lead to a short list of candidate technologies. Hence, the final selection of the appropriate technology will be the responsi- bility of the user. The tool leads the user to multiple tech- nologies for a particular project, and it provides information necessary to understand, design, specify, estimate costs, and verify construction. This tool does not replace the project geotechnical engineer. The geotechnical engineer’s judgment is the final step in the selection process, which takes into con- sideration the following: local geological conditions, local construction practices, construction costs, maintenance costs, design and quality control issues, performance and safety (e.g., pavement smoothness, hazards caused by maintenance operations, and potential failures), inconvenience (an impor- tant factor, especially for heavily traveled roadways or long detours), environmental aspects, aesthetic aspects (appear- ance of completed work with respect to its surroundings), and many other factors. Web-Based Information System The homepage for the web-based information system is shown in Figure 3.3. The title of the web page is shown in the upper left corner. Along the left side of the page are several buttons (Home, Project Background, Geotechnical Design Process, Catalog of Technologies, Technology Selection System, Glossary, Abbreviations, Frequently Asked Questions, Submit a Comment, Links, and About this Website) that are always available to the user. The part outlined in the bold box will change as other pages are selected. In subsequent screenshots, only the material within the bold box is shown. As shown within the bold box in Figure 3.3, there are four main parts to the system: Geotechnical Design Process, Catalog of Tech- nologies, Technology Selection, and Glossary. The Geotechnical Design Process page is included to alert the user to the basic background information needed to con- duct geotechnical design, such as project loading conditions and constraints, soil site conditions, and evaluation of alter- natives. The page contains links to FHWA documents on review of geotechnical reports, evaluation of soil and rock properties, subsurface investigation, and instrumentation. In addition, links to several geotechnical design manuals by state departments of transportation are provided. During the development of the system, it was realized that numerous technical terms and abbreviations were used and that in some cases different technologies used terms in different ways. Thus, a Glossary is included with the system so that users are able to find definitions of terms used in the various documents. The technologies can be accessed in several ways. The Cata- log of Technologies page provides a listing of the 46 ground improvement and geoconstruction technologies in the system, organized to address the three element areas. An exception is that two traditional technologies—excavation and replace- ment, and traditional compaction—are included because they are often-used, “base” technologies, to which ground improve- ment and geoconstruction methods are compared. The list of technologies in the catalog is shown under Background in Chapter 2. The name of each technology is a hot-link button on the website that takes the user to a web page for that tech- nology. The technology-specific web pages will be discussed in more detail subsequently. The Technology Selection page pro- vides two further means of accessing technologies: through a classification system and through an interactive selection sys- tem. The classification system groups technologies into the fol- lowing categories: • Earthwork construction • Densification of cohesionless soils • Embankments over soft soils • Cutoff walls • Increased pavement performance • Sustainability • Soft-ground drainage and consolidation • Construction of vertical support elements • Lateral earth support • Liquefaction mitigation • Void filling

16 Figure 3.3. Homepage for the SHRP 2 R02 project information and guidance system. Thus, an experienced engineer can access solutions accord- ing to particular categories of problems. The interactive selec- tion system provides the user the opportunity to assess technologies based on several applications. A selection proce- dure has been developed for each application area shown in Figure 3.2, and as defined in the R02 project work scope. The third element area, stabilization of pavement working plat- forms, was split into two parts to recognize differences between permanent and temporary applications. The interactive selection system is entered through the screenshot shown in Figure 3.4, wherein the first decision in the process is to select the potential application. In the selection system, the list of applicable technologies is shown on the right side of the page (see Figure 3.4), all of which are hot-linked to their respective technology pages. At the start of the selection, all technologies are shown on the right side, and as selections are made, nonapplicable technologies are grayed out. After clicking on one of the four application areas shown in Figure 3.4, the user will encounter a page requesting additional information to narrow the list of candidate technologies for the particular application. The requested input and order of queries to the user were established after considering the effect of the requested information on the determination of the potential technologies list. Potential queries (in no particular order) gen- erated during development of the system include the following: • What type of project is being constructed? • What is the size of the project being constructed? • Are there any project constraints to be considered in select- ing a possible technology?

17 • What is the soil type that needs to be improved? • To what depth do the unstable soils extend? • At what depth do the unstable soils start? • Is there a “crust” or “rubble fill” at the ground surface? • What is the depth to the water table? • How does the water table fluctuate? • What constraints (i.e., utilities, material sources, or exist- ing adjacent structures) exist? • What is the desired outcome (i.e., decrease settlement, decrease construction time, or increase bearing capacity) of the improvement? • With which technologies does the user already have experience? The questions used to narrow the technologies are dependent on the application selected. Generally, three or four questions are used to develop a short list, which can then be further refined by answering additional questions. To illustrate use of the system, solutions for Construction over Unstable Soils are presented herein in more detail. The other three applications are discussed in detail in the Web-Based Information and Guidance System Development Report. Construction over Unstable Soils Selecting the Construction over Unstable Soils application leads to a decision process for foundation soil improvement Figure 3.4. Screenshot for the Interactive Selection System page.

18 or reduced loading. This application is focused on ground improvement to support embankments or transportation structures, such as walls or box culverts over unstable soils. This system is focused on identifying geoconstruction solu- tions to these problems; however, users should also consider that structural solutions to such problems may be preferred alternatives. From the list of potential queries, two questions (What is the soil condition that needs to be improved? To what depth do the unstable soils extend?) were selected as the initial ques- tions to reduce the number of potential technologies for this application. These two queries were most beneficial in pro- viding a preliminary short list of applicable technologies. A screenshot of the first page for the Construction over Unsta- ble Soils application is shown in Figure 3.5. The list of tech- nologies shown on the right side of this page has narrowed from the complete list shown on the previous Interactive Selection System page (see Figure 3.4). The unstable soil con- ditions considered in the system are: • Unsaturated and saturated, fine-grained soils • Unsaturated, loose, granular soils • Saturated, loose, granular soils • Voids—sinkholes, abandoned mines, etc. • Problem soils and sites—expansive, collapsing, dispersive, organic, existing fill, and landfills Figure 3.6 shows a screenshot of what appears after answer- ing the question about soil type. On the right side of the screenshot several technologies are grayed, indicating that they generally are not appropriate for the soil type selected (unsaturated and saturated, fine-grained soil). The next question to be answered is the depth range for improvement. The depth ranges selected for inclusion in the system follow: • 0–5 ft (0–1.5 m) • 5–10 ft (1.5–3 m) • 10–30 ft (3–9 m) • 30–50 ft (9–15 m) • Greater than 50 ft (15 m) After answering the question on unstable soil depth, additional technologies may be grayed on the right side. At this point, the Figure 3.5. Screenshot for the first Construction over Unstable Soils page.

19 Figure 3.6. Screenshot for the second Construction over Unstable Soils page. user can stop and assess the candidate list of technology solu- tions or enter additional project-specific information, as shown in Figure 3.7. Because many of these technologies are used in combination with other ground improvement methods, guidance on combining technologies is contained in the linked white paper titled Integrated Technologies for Embankments on Unstable Ground (see Figures 3.5 and 3.6). A final technology selection screenshot (Figure 3.8) shows the resulting candidate technologies on the right side of the page when the questions have been answered as indicated. It can be seen that the list of technologies applicable to the selected conditions has been narrowed. At this point, a user can click on any of the highlighted technologies to obtain technology-specific information. For example, clicking on Prefabricated Vertical Drains and Fill Preloading will bring up the screenshot shown in Figure 3.9. The documents listed can be accessed through hot-links on the website. Ratings are provided for each technology on the degree of technology establishment and a technology’s potential to achieve SHRP 2 objectives. As shown in Figure 3.9, several information documents about a given technology are accessible from the system. Table 3.1 provides a list of these products and tools and indi- cates the document formats. These documents are hot-linked and can be opened from this page, or the box shown can be clicked and the selected documents can be printed or saved to a file for further use. The information documents are generally provided in Adobe PDF format. Technology fact sheets are two-page summary information sheets that provide basic informa- tion on the technology, including basic function, general description, geologic applicability, construction methods, SHRP 2 applications, complementary technologies, alternate technologies, potential disadvantages, example successful applications, and key references. Photos show equipment or methods used in the technology and can be valuable to get a perspective on the technology. Case histories provide a summary of project(s), preferably conducted in the United States by a state department of transportation (DOT), if available, and contain project location, owner, performance, contact information, and a project summary. The design and QC/QA procedures documents provide a summary of recommended procedures for the technology. The recom- mended design and QC/QA procedures come from an

20 Figure 3.7. First screenshot for Project-Specific Technology Selection for Construction over Unstable Soils. assessment of the current state of the practice of each tech- nology. In cases where a well-established procedure (e.g., a FHWA manual) exists, that procedure is recommended. In cases of technologies with multiple procedures but with no established procedure, the assessment led to a recommen- dation of procedure(s) to use. For a few technologies, design or QC/QA procedures were established based on additional research conducted during the project. For most technolo- gies, two cost estimation documents are available. The first provides an explanation of the cost item specific to the technology, generally emanating from the payment meth- ods contained in specifications. Available regional and cost numbers, generally from DOT bid tabs or national databases, are compiled for each technology. The second document for cost estimation consists of an Excel spreadsheet developed to estimate costs for the use of the technology. This document could not be prepared for some technologies due to insuffi- cient information. The spreadsheet can be modified by the user to estimate specific project cost based on either a pre- liminary or final design. Example specification(s) are pro- vided for each technology in Adobe PDF and Microsoft Word (if available). The final document available for each technology is a bibliography compiled during the research project.

21 Figure 3.8. Second screenshot for the Project-Specific Technology Selection for Construction over Unstable Soils.

22 Table 3.1. Information and Guidance System Products and Tools Available for Review or Download Format Technology fact sheets Adobe PDF Photos Adobe PDF Case histories Adobe PDF Design procedures Adobe PDF QC/QA procedures Adobe PDF Cost estimation Adobe PDF and Microsoft Excel Example or guide specifications Adobe PDF or Microsoft Word Bibliography Adobe PDF Figure 3.9. Screenshot for the Prefabricated Vertical Drains and Fill Preloading Technology list of available documents. Other Pages Buttons for frequently used pages are located on the left side of the homepage for the web-based system (see Figure 3.3). The Geotechnical Design Process, Catalog of Technologies, and Technology Selection system pages have been discussed in some detail. Other pages, such as Project Background, Glos- sary, Abbreviations, About this Website, and Frequently Asked Questions, are self-explanatory. They are reviewed in more detail in the Web-Based Information and Guidance System Development Report. To keep the system a living, updatable system, an extensive comment page has been developed and is shown in Figure 3.10. Comments can be submitted related to a case history for a technology, photographs or videos, speci- fications, cost information, and references, as well as general comments about the information and guidance system.

23 Figure 3.10. Screenshot of Submit a Comment page. Summary Programming of the information and guidance system is func- tionally complete. Internal review of the programming and project documents has been completed. Revisions and additions are actively being incorporated with every review and comment cycle. The next step is a beta testing program, as described in Chapter 6. Prior to full, public release of the Information and Guidance System website, the beta testing should be performed and website and products revised as appropriate.