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

Below is the uncorrected machine-read text of this chapter, intended to provide our own search engines and external engines with highly rich, chapter-representative searchable text of each book. Because it is UNCORRECTED material, please consider the following text as a useful but insufficient proxy for the authoritative book pages.

41 A p p e n d i x A introduction The Geotechnical Solutions for Transportation Infrastruc- ture system provides a means for transportation engineers, geologists, planners, officials, engineering consultants, and others to access critical information for geoconstruction technologies. The primary value of the web-based informa- tion and guidance system is that it collects, synthesizes, inte- grates, and organizes a vast amount of critically important information about geoconstruction technologies in a system that makes the information readily accessible to the transpor- tation agency personnel who need it most. The homepage is shown in Figure A.1. The system was developed with the intent that both nontechnical and technical personnel would use the system, albeit at different levels. This user’s guide pro- vides a brief introduction to the system and some examples of how different users can use the available tools. Users want- ing detailed information are referred to the second Strategic Highway Research Renewal Project R02 (SHRP 2 R02) proj- ect reports, which describe the development of the system and available documents. Responsibilities of the User The Geotechnical Solutions for Transportation Infrastruc- ture system is not a “black box” that provides solutions that can be blindly implemented. During the development stage, every review group expressed concern that the potential exists for inexperienced users to inappropriately apply the informa- tion provided on the website. The application of this system is the responsibility of the user. It is imperative that the responsible user understands the potential accuracy limitations of the program results, independently cross checks those results with other methods, and examines the reasonableness of the results with engineer- ing knowledge and experience. Marr (2006) developed the following five take-home messages concerning geotechnical engineering and judgment in the information age: • Engineering judgment without relevant experience is weak. • Engineering judgment without relevant data is foolish. • Good judgment needs good data and evaluated experience. • Good judgment is essential for the effective use of infor- mation technology tools. • Good judgment is central to geotechnical engineering, even in the information age. Site disclaimer The opinions and conclusions expressed or implied on this system are those of the research agency. They are not necessar- ily those of the Transportation Research Board, the National Academies, or the program sponsors. This system and the information provided are offered as is, without warranty or promise of support of any kind either expressed or implied. Under no circumstance will the National Academy of Sciences or the Transportation Research Board (collectively, “TRB”) or will the R02 project team (individually or universities or firms) (collectively, “project team”) be liable for any loss or damage caused by the installation, use, or oper- ation of this product. TRB and the project team make no rep- resentation or warranty of any kind, expressed or implied, in fact or in law, including without limitation, the warranty of merchantability or the warranty of fitness for a particular pur- pose, and shall not in any case be liable for any consequential or special damages. Technology-Specific information The individual technology information is accessed through the Catalog of Technologies through selection of a specific tech- nology, as shown in Figure A.2. The downloadable documents User’s Guide to the Information and Guidance System

42 Figure A.1. Geotechnical Solutions for Transportation Infrastructure homepage. provided on the individual Technology Information web page for each technology provide the mechanism for the user to access technology-specific information. The intent of all the website features surrounding the Catalog of Technologies is to aid the user in understanding the technical information or aid in the selection and application of the technology. An illustra- tion of the structure of the downloadable documents is pre- sented in Figure A.3. Also included on the Technology Information page are the R02 ratings for each technology. The location of the rat- ings on the page is circled in red in Figure A.2. Some specific studies were completed for a few technologies, and links to these special studies are provided on this page as well, when appropriate. Options for Technology Selection Assistance The Technology Selection page provides the means of access- ing technology-specific information through a classification system and through an interactive selection system. A sche- matic of the technology selection system and its interlink with the Technology Information web pages is illustrated in Figure A.4. The flow of the technology selection system is illustrated in Figure A.5. In the classification system, the tech- nologies are grouped into categories that allow an experi- enced engineer to access solutions according to a particular category of problems. The interactive selection system pro- vides the user the opportunity to access potential technologies

43 Figure A.2. How to access individual Technology Information page. Individual Technology Information Catalog of Technologies Technology Fact Sheet Photographs DesignGuidance QC/QA Cost Information Specifications Case Histories Case Histories Bibliography Additional Resources* * Not available for all technologies. Cost Estimating Spreadsheet* Figure A.3. Concept of individual Technology Information page.

44 Figure A.4. Conceptual layout of technology selection. Technology Selection Individual Technology Information Technologies by Classification Interactive Selection System Interactive Selection System Summary (in a new window) Interactive Selection System Output (PDF) based on several applications. The inner workings of the interactive selection system are described in detail in the R02 project Web-Based Information and Guidance System Devel- opment (Douglas et al., 2012). Decision help notes have been developed for each decision encountered in the interactive selection system. These notes are available on all the Interactive Selection System web pages to assist both experienced and inexperienced users with deci- sions. On the website, these notes are appropriately placed and are accessed by clicking on a help link that appears as a boxed question mark (?). After completion of the interactive selection system, the user has the option to select Go to Selection Summary, which opens a new window that documents the user inputs, shows the potential technologies with the SHRP 2 R02 ratings, and provides a space to enter user-specific information. Within this window, the user has the option to Create PDF, which generates a PDF documenting the results of the interactive selection system. The individual technologies within the Selec- tion Summary window and the PDF are linked to the individ- ual technology information for ease of use. A limitation of the interactive selection system is that only singular technologies appear as potential solutions. To assist the user in identifying possible combinations of technologies for the construction over unstable soils application, a document titled White Paper on Integrated Technologies for Embank- ments on Unstable Ground was developed and is available for download throughout the selection system, as shown by the red oval in Figure A.5. Introduction to System Through Examples To provide a further introduction to the system, several examples have been developed to illustrate both information provided in the system and the use of the website. The exam- ples consider different user backgrounds and a wide range of projects. Example 1: State Transportation Official Question Regarding Micropiles Example Intent Illustrate an example where an upper-level transportation official is requesting additional information to understand a proposed solution. Project Information • Application: existing bridge retrofit. • Project site: existing bridge over river. • Subsurface conditions 44 Moderately weak, intermixed, sandy, and clayey soils from surface to depth of 40 ft; and 44 Hard clay below 40 ft. • The State Transportation geotechnical department devel- oped a plan to underpin the existing foundations with micropiles. Problem Identify introductory material for micropiles and similar applications by other transportation departments. Discussion The Technology Information page for micropiles can be accessed through the Catalog of Technologies and is shown in Figure A.6. The circled area in Figure A.6 highlights the down- loadable products that can be used to provide an introduction to the technology. The technology fact sheets are two-page summary information sheets that provide basic information on the technology, including basic function, general descrip- tion, geologic applicability, construction methods, SHRP 2 applications, complementary technologies, alternate technol- ogies, potential disadvantages, example successful applica- tions, and key references. The photos show the equipment or methods used in the technology and can be valuable to get a perspective on the technology. Case histories provide a sum- mary of project(s), which were preferably conducted in the United States by a state department of transportation (DOT),

45 Figure A.5. Technology selection assistance.

46 Figure A.6. Technology Information web page for micropiles.

47 and contain project location, owner, a project summary, per- formance, and contact information. Example 2: Experienced DOT Engineer/ Geologist with Known Solution Example Intent Illustrate an example where an experienced engineer/geologist has a desired solution and is attempting to locate current tech- nical information for a technology. Project Information • Application: new embankment through a swamp. • Project site: wooded and undeveloped. • Subsurface conditions 44 Wet and weak clayey soils from surface to depth of 70 ft; and 44 Dense sand below 70 ft. • Experience, availability of materials, and schedule allow DOT personnel to select geosynthetic reinforced embankment. Problem Identify up-to-date information for design, cost estimate, specifications, and quality control and quality assurance (QC/QA). Discussion The Technology Information page for geosynthetic rein- forced embankments can be accessed through the Catalog of Technologies and is shown in Figure A.7. The circled area in Figure A.6 highlights the downloadable products that can be used to provide the technical information for the technology. The design guidance and QC/QA documents provide a sum- mary of recommended procedures for the technology. Cost information provides an explanation of the cost item specific to the technology, generally emanating from the pay methods contained in specifications. Available regional and cost num- bers, generally from DOT bid tabs or national data bases, are compiled for each technology. A second cost document con- sists of an Excel spreadsheet developed to estimate costs for the use of the technology and can only be accessed as a link through the cost information document. The user can mod- ify the spreadsheet to estimate specific project cost based on either a preliminary or final design. The spreadsheet identi- fies pay items by line and serves to assist an estimator for overlooking a particular pay item for a technology. A specifi- cations document is provided for each technology and offers a summary of example specifications identified during the project. Guide specifications are provided for each technol- ogy as a PDF file, if available. Example 3: Densification of Liquefiable Granular Soil Example Intent Illustrate options in the system to assist a user in identifying potential technologies to mitigate liquefiable granular soils. Project Information • Application: bridge approach embankment. • Project site 44 Open and undeveloped; and 44 Total area = 30,000 ft2. • Subsurface conditions 44 Saturated, loose sand from surface to depth of 25 ft; and 44 Dense sand below 25 ft. • Factors of safety adequate under static loading. • Potential liquefaction of loose sand is a concern. Problem Identify potential technologies to mitigate liquefiable granu- lar soils. Discussion Two options exist to identify potential technologies for this example. A listing of potential technologies can be found in Technologies by Classification, as depicted in Figure A.8. A more refined listing of potential technologies can be devel- oped with the interactive selection system and user-input project-specific information, shown in Figure A.9. In Fig- ure A.9, the lower right illustration is the result of a new win- dow being opened after selecting Go to Selection Summary at the end of the Interactive Selection System. From this new window, a PDF can be generated with a user name, organiza- tion, and project name to provide documentation of the system results. Additionally, in Figure A.9, the lower right illustration shows the Project-Specific Technology Selection for Construc- tion over Unstable Soils. This project-specific selection system is intended for experienced users and was developed only for the fine-grained and granular soil conditions within the con- struction over unstable soils application. Example 4: Embankment on Soft Clay Example Intent Illustrate comparison of technologies for a project.

48 Figure A.7. Technology Information web page for geosynthetic reinforced embankments.

49 Figure A.8. Technologies by Classification for mitigating liquefiable granular soils.

50 Figure A.9. Interactive Selection System for mitigating liquefiable granular soils.

51 Project Information • Application: bridge approach embankment. • Embankment requirements 44 Length = 1,000 ft; 44 Height = 20 ft; 44 Width at crest = 50 ft; and 44 Width at base = 130 ft (2H:1V side slopes). • Subsurface conditions 44 Soft clay layer from subgrade to depth of 45 ft; and 44 Dense sand at depth 45 ft. • Global stability and settlement are concerns. Problem Compare potential technologies identified through the selec- tion system. Discussion Through completion of the interactive selection system, the selection summary presented in Figure A.10 was developed. The project-specific selection system could also have been used for further refinement. From the list of potential tech- nologies, the following four technologies were selected for further evaluation: aggregate columns, column-supported embankments, geosynthetic reinforced embankments, and prefabricated vertical drains and fill preloading. After com- pleting a preliminary design for each technology, a cost esti- mate can be prepared to compare the technologies, or SHRP 2 Renewal ratings can be compared, as applicable. The process of getting to the cost estimate tool is presented in Figure A.11. The tool can only be accessed through the cost information document available on the Technology Informa- tion web page. The cost information document contains criti- cal information required to complete a representative cost estimate for a technology. A preliminary design must be com- pleted to develop a preliminary cost estimate. For this example and not included with this guide, a pre- liminary cost estimate was completed for each of the four technologies selected for further evaluation. The results of the cost analysis and other information gathered from the available documents enabled the development of Table A.1. The comparison shown in Table A.1 is provided as an exam- ple only; the system does not produce this table. A project- specific design and comparison of technologies is required to complete a comparison, and other factors can be incorpo- rated into the comparison as appropriate. The cost information produced as a part of this project is intended to provide the user with a means for understanding what variables may impact the cost of a given geotechnical solution, as well as for developing a preliminary cost estimate for a given technology on a project-specific basis. There are many factors that can affect cost for a specific project (i.e., soil type, labor rates, utility conflicts); identifying and under- standing how these variables impact cost can be beneficial when evaluating the applicability of a geotechnical solution. It is important to note that while initial cost is a consideration when selecting a solution, it should not be the driving force; performance, construction time, life-cycle costs, and safety should be factored into the evaluation of alternative geo- construction technologies. Comments on Selection of Final Technology The selection system guides a user to a short list of unranked, candidate technologies. Guidance for the completion of a comparable, quantifiable analysis to aid the user in the final selection remains to be developed. However, the information provided for each technology will allow the user to complete a preliminary design and subsequently compare technolo- gies. The final selection of the geoconstruction technology to use is the responsibility of the user. Holtz (1989) indicated that each of the following elements must be carefully examined when selecting a geoconstruction technology: • Construction cost • Maintenance cost • Performance and safety (pavement smoothness; hazards caused by maintenance operations; potential failures) • Inconvenience (a tangible factor, especially for heavily traveled roadways or long detours) • Environmental aspects • Aesthetic aspects (appearance of completed work with respect to its surrounding) References Douglas, S. C., V. R. Schaefer, and R. R. Berg. 2012. SHRP 2 Report R02: Web-Based Information and Guidance System Development Report, prepared for The Strategic Highway Research Program 2, Transpor- tation Research Board of the National Academies, Washington, D.C. Holtz, R. D. 1989. NCHRP Synthesis of Highway Practice 147: Treatment of Problem Foundations for Highway Embankments. TRB, National Research Council, Washington, D.C. Marr, W. A. 2006. Geotechnical Engineering and Judgment in the Infor- mation Age. In Proc. GeoCongress 2006: Geotechnical Engineering in the Information Technology Age, Feb. 26–March 1, ASCE, Reston, Va., pp. 1–17.

52 Figure A.10. Interactive selection system summary for Example 4.

53 Figure A.11. Process of getting to conceptual estimating tool. Table A.1. Example Comparison of Geoconstruction Technologies Technology Cost Estimate Time Delay Total Settlement Other Considerations Aggregate columns (stone columns) $5.0M Less than 0.5 yr 30% to 40% of total settlement for unimproved case Risk of insufficient lateral confinement if soil is too soft, instrumentation and monitoring may be required. Column-supported embankments $3.5M None Less than 3 in. Instrumentation and monitoring may be useful, minimizes damage to adjacent facilities, higher performance achievable. Geosynthetic reinforced embankments $286K Years without PVDs No reduction in total settlement over unimproved case Instrumentation required, risk of additional settlement if soil is softer than expected, staged construction possibly required. Prefabricated vertical drains (PVDs) and fill preloading $294K 0.5 to 1 yr Low settlements after 0.5 to 1 yr Secondary compression settlements.