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Advances in Unstable Slope Instrumentation and Monitoring (2020)

Chapter: Chapter 3 - State of the Practice

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Suggested Citation:"Chapter 3 - State of the Practice." National Academies of Sciences, Engineering, and Medicine. 2020. Advances in Unstable Slope Instrumentation and Monitoring. Washington, DC: The National Academies Press. doi: 10.17226/25897.
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Suggested Citation:"Chapter 3 - State of the Practice." National Academies of Sciences, Engineering, and Medicine. 2020. Advances in Unstable Slope Instrumentation and Monitoring. Washington, DC: The National Academies Press. doi: 10.17226/25897.
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Suggested Citation:"Chapter 3 - State of the Practice." National Academies of Sciences, Engineering, and Medicine. 2020. Advances in Unstable Slope Instrumentation and Monitoring. Washington, DC: The National Academies Press. doi: 10.17226/25897.
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Suggested Citation:"Chapter 3 - State of the Practice." National Academies of Sciences, Engineering, and Medicine. 2020. Advances in Unstable Slope Instrumentation and Monitoring. Washington, DC: The National Academies Press. doi: 10.17226/25897.
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Suggested Citation:"Chapter 3 - State of the Practice." National Academies of Sciences, Engineering, and Medicine. 2020. Advances in Unstable Slope Instrumentation and Monitoring. Washington, DC: The National Academies Press. doi: 10.17226/25897.
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Suggested Citation:"Chapter 3 - State of the Practice." National Academies of Sciences, Engineering, and Medicine. 2020. Advances in Unstable Slope Instrumentation and Monitoring. Washington, DC: The National Academies Press. doi: 10.17226/25897.
×
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Suggested Citation:"Chapter 3 - State of the Practice." National Academies of Sciences, Engineering, and Medicine. 2020. Advances in Unstable Slope Instrumentation and Monitoring. Washington, DC: The National Academies Press. doi: 10.17226/25897.
×
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Suggested Citation:"Chapter 3 - State of the Practice." National Academies of Sciences, Engineering, and Medicine. 2020. Advances in Unstable Slope Instrumentation and Monitoring. Washington, DC: The National Academies Press. doi: 10.17226/25897.
×
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Suggested Citation:"Chapter 3 - State of the Practice." National Academies of Sciences, Engineering, and Medicine. 2020. Advances in Unstable Slope Instrumentation and Monitoring. Washington, DC: The National Academies Press. doi: 10.17226/25897.
×
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Suggested Citation:"Chapter 3 - State of the Practice." National Academies of Sciences, Engineering, and Medicine. 2020. Advances in Unstable Slope Instrumentation and Monitoring. Washington, DC: The National Academies Press. doi: 10.17226/25897.
×
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Suggested Citation:"Chapter 3 - State of the Practice." National Academies of Sciences, Engineering, and Medicine. 2020. Advances in Unstable Slope Instrumentation and Monitoring. Washington, DC: The National Academies Press. doi: 10.17226/25897.
×
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Suggested Citation:"Chapter 3 - State of the Practice." National Academies of Sciences, Engineering, and Medicine. 2020. Advances in Unstable Slope Instrumentation and Monitoring. Washington, DC: The National Academies Press. doi: 10.17226/25897.
×
Page 26

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15 State of the Practice 3.1 Questionnaire Content and Method A web-based survey questionnaire was used to document the state of practice for instrumen- tation and monitoring of unstable slopes within state DOTs. Geotechnical contacts from state DOTs, Puerto Rico, and the District of Columbia were invited to complete the questionnaire. Forty-three states responded to the survey (Figure 3.1). A copy of the questionnaire is provided in Appendix A, respondent information is provided in Appendix B, and survey responses are provided in Appendix C and D of this report. Responses to the survey are synthesized in the following sections to illustrate the state of the practice. 3.2 Adoption of Instrumentation and Monitoring of Unstable Slopes First, survey respondents established whether they use geotechnical instrumentation and monitoring for unstable slopes. About 98% (42/43) of responding states indicated having unstable slopes and using geotechnical instrumentation and monitoring for those slopes. Of the 42 states that monitor unstable slopes, most (36%) currently have between one and five slopes in a regular or planned instrumentation and monitoring program (Figure 3.2). At the tails of the distribution, three states indicated they are not monitoring any slopes and four states are monitoring more than 50 slopes. 3.3 How Slopes Are Selected for Instrumentation and Monitoring Survey information was collected from the states to determine the practices that are used to select slopes for instrumentation and monitoring. The questionnaire was designed to allow selection of multiple methods to determine if there are multiple reasons slopes are selected for instrumentation and monitoring. The responses for selection of slopes in an instrumentation and monitoring program are provided in Figure 3.3. All the responding states indicated using the judgment of geotechnical staff to select slopes for instrumen tation. Most states also consider event history when selecting slopes (86%). About half of respon- dents select slopes based on requests from DOT staff outside of the agency geotechnical program (51%) and as part of a site-specific hazard or risk treatment plan (44%). Other reasons slopes may be selected for instrumentation include responding to public or external agency requests (14%), claim or loss prevention (12%), and following agency guidelines or procedures (12%). C H A P T E R 3

16 Advances in Unstable Slope Instrumentation and Monitoring Responded to Survey Did Not Respond to Survey Figure 3.1. Map of the United States showing the 43 states that responded to the survey in green. 7% 36% 14% 24% 10% 10% 3 15 6 10 4 4 0 5 10 15 20 25 30 35 40 None 1 to 5 5 to 10 10 to 25 25 to 50 Greater than 50 0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100% Number of Responses Percentage of Survey Respondents 42 survey respondents Figure 3.2. Number of unstable slopes currently in a regular or planned instrumentation and monitoring program.

State of the Practice 17 3.4 Use of Instrumentation and Monitoring Technologies A synthesis of survey responses regarding the use of instrumentation and monitoring tech- nologies is presented in this section. A list of instrumentation and monitoring technologies was presented in the survey questionnaire, and respondents were asked whether these technologies have been used by their agency for over 10 years (Established Use), adopted within the last 10 years (New Use), or not used at all (Not Used). The distribution of use of these technologies is shown in Figure 3.4. Not all respondents provided an answer for every technology; therefore, the calculated percentage of use is based on the number of respondents per technology, not the total number of survey respondents. Reasons for not responding to every technology may include an unfamiliarity with the technology or uncertainty about use in the DOT. Established Use There are several instrumentation and monitoring technologies that have been used by state DOTs for more than 10 years (Established Use). Most respondents have established use of inclinometer systems (traversing probe systems) and ground-based surveys. Over half of respondents are monitoring groundwater levels or flow, using aerial photogrammetry/imagery, and using tilt measurement, and indicated these are established use technologies with more than 10 years of implementation experience. There are other technologies that respondents indicated have established use; however, the responses suggest less than a majority of the states have used these technologies for more than 10 years in their organization. The technologies with lesser established use experience include in-place inclinometers, surface water flow or precipitation, surface extensometer systems, GPS, strain gauges, borehole extensometer systems, event warning systems to agency staff, ground-based radar, accelerometers, ground-based photogrammetry, aerial LiDAR, event warning systems to the public or external stakeholders, real-time video streams, event video 2% 12% 12% 14% 44% 51% 86% 100% 1 5 5 6 19 22 37 43 0 5 10 15 20 25 30 35 40 Other Agency guidelines or procedures Claim or loss prevention Public or other external agency requests As part of a site-specific hazard or risk treatment plan Requests from DOT staff outside of agency geotechnical program Event history Judgment of geotechnical staff 0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100% Number of Responses Percentage of Survey Respondents 43 survey respondents Figure 3.3. Methods of selecting unstable slopes for instrumentation and monitoring. The values in the bars indicate the number of states responding to each option.

18 Advances in Unstable Slope Instrumentation and Monitoring or photo capture systems, significant event detection systems, satellite InSAR, and ground- based LiDAR. New Use There are also several instrumentation and monitoring technologies that have been adopted by state DOTs within the last 10 years (New Use). The technologies include implementation of ground-based instrumentation and monitoring systems identified by other states as having established use. Survey responses suggest that in the last 10 years, use of remote-sensing Event warning systems to public or external stakeholders Accelerometers Significant Event detection systems Ground-based radar Satellite InSAR Real-time video streams Event video or photo capture systems Event warning systems to agency staff (e.g., operations, engineering) Surface extensometer/deformation system Borehole extensometer/deformation system Ground-based photogrammetry Strain gauges Aerial LiDAR Surface water flow or precipitation GPS Ground-based LiDAR Inclinometer systems (In-place systems) Tilt measurement Aerial photogrammetry/imagery Groundwater levels or flow Ground-based survey Inclinometer systems (Traversing probe systems) 0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100% Established Use New Use Not Used 42 survey respondents Figure 3.4. Methods of instrumentation and monitoring of unstable slopes. Note that methods are sorted from most used (established use + new use) at the top to least used at the bottom.

State of the Practice 19 technologies has experienced the greatest adoption of use. The summary of survey responses related to new use of all surveyed instrumentation and monitoring technologies within the last 10 years is presented in Figure 3.4. Of the new use technologies, satellite InSAR and significant event detection systems are technologies that responses suggest implementation has begun entirely within the last 10 years. This may be largely the case, but the literature review recognizes early use and implementation guidance published by the FHWA in 2006 (USDOT, 2006) and 2008 (USDOT, 2008). Not Used Another indication of the state of the practice is revealed by examining the technologies not being used by most states. Notice that in Figure 3.4, methods are sorted from most used (established use + new use) at the top to least used at the bottom, that is, the instrumentation and monitoring methods that were reported as “not used” most often have been sorted to the bottom of Figure 3.4. More than half of respondents are not using the following 13 instru- mentation and monitoring techniques: aerial LiDAR, strain gauges, ground-based photo- grammetry, borehole extensometer/deformation systems, surface extensometer/deformation systems, event warning systems to agency staff (e.g., operations, engineering), event video or photo capture systems, real-time video streams, satellite InSAR, ground-based radar, signifi- cant event detection systems, accelerometers, and event warning systems to public or external stakeholders. 3.5 Use of Data Collection, Viewing, and Communication Technologies A list of data collection, viewing, and communication technologies was presented in the questionnaire, and respondents were asked to identify which technologies have been used by their agency for over 10 years (Established Use), adopted within the last 10 years (New Use), or not used at all (Not Used). Not all respondents provided an answer for every technology; therefore, the calculated percentage of use is based on the number of respondents per technology, not the total number of survey respondents. The distribution of use of these technologies is shown in Figure 3.5. Established Use Established use of data collection, viewing, and communication technologies is primarily limited to data collection through manual monitoring and recording on paper, though a quarter of respondents have been using onsite acquisition equipment. New Use Within the last 10 years, there has been a rise in use of remote, real-time, and web-based data collection, viewing, and communication in the areas of: • Web-based access or presentation of data to agency staff • Remote real-time viewing of data • Remote viewing of recorded data • Transmission of data offsite via wireless (radio, cellular, etc.) telemetry • Onsite real-time data acquisition for one to a few instruments of the same type • Manual monitoring and tablet or other electronic recording

20 Advances in Unstable Slope Instrumentation and Monitoring Technologies Not Being Used More than half of respondents are not using the following instrumentation and monitoring techniques: • Onsite real-time data acquisition for several different types of instruments • Onsite data analysis for decision support • Web-based presentation of data to stakeholders outside of agency 3.6 Reported State Practices and Perspectives In response to the survey, about half of the respondents said that they have developed or deployed an innovative instrumentation or monitoring technology within the last 10 years for an agency special case or specific unstable slope problem. It is important to note that the definition Web-based presentation of data to stakeholders outside of agency Onsite data analysis for decision support Onsite real-time data acquisition for several different types of instruments Remote real-time viewing of data Transmission of data offsite via wireless (radio, cellular, etc.) telemetry Web-based access or presentation of data to agency staff Remote viewing of recorded data Onsite real-time data acquisition for 1 to a few instruments of the same type Manual monitoring and paper-based recording Manual monitoring and tablet or other electronic recording 0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100% Established Use New Use Not Used 42 survey respondents Figure 3.5. Methods of instrumentation and monitoring data collection, viewing, and communication.

State of the Practice 21 of “innovative” is subjective to each respondent. Some of the innovations described appear to be use cases that have not been adopted by any other state, while other states reported innovations that have been used by others for over a decade. The instrumentation and monitoring technologies reported in the survey to be innovative by the DOTs generally fit into three groups: ground-based installed instrumentation, remote sensing, and data management. About half of the responses related to ground-based installed instrumentation, which ranged from fiber optic sensors to MEMS in-place inclinometers. About half of the responses related to remote sensing including several uses of UAVs, LiDAR, photogrammetry, and InSAR. A few responses related to implementation of web-based data management. Refer to Questions 7 and 18 in Appendix C for specific responses. 3.7 Funding Sources and Procurement Practices Funding for instrumentation and monitoring of unstable slopes comes from several sources. The distribution of funding sources is shown in Figure 3.6. Most respondents reported that funding comes from agency pre-engineering or engineering design project fund sources, construction project engineering funds, operations or maintenance budgets, and emergency/ contingency funds within the agency. Annual funds allocated to instrumentation and monitoring range from less than $10,000 to greater than $250,000, with the most commonly reported range being $10,000–$50,000 (Figure 3.7). Two state DOTs indicated spending greater than $250,000. Note that the survey questionnaire did not seek to delineate between labor, materials, and overhead, and expenses were estimated by survey respondents. To provide a sense of where money is being spent, respondents offered information on the proportion of instrumentation and monitoring services that are performed in-house by DOTs versus those performed by vendors, contractors, consultants, etc. Respondents estimated which “percentage bin” (e.g., 0–25%, 25–50%, etc.) their agency fit into in terms of services performed in-house for several categories. Results are presented in Figure 3.8. In general, DOTs 5% 19% 26% 36% 52% 55% 62% 71% 2 8 11 15 22 23 26 30 0 5 10 15 20 25 30 35 40 Other From dedicated funds in agency geotechnical budget Emergency/contingency funds external to the agency From discretionary funds in agency geotechnical budget Emergency/contingency funds within agency Operations or maintenance budgets Construction project engineering funds Agency pre-engineering or engineering design project fund sources 0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100% Number of Responses Percentage of Survey Respondents 42 survey respondents Figure 3.6. Funding sources for instrumentation and monitoring of unstable slopes.

5% 17% 38% 24% 17% 2 7 16 10 7 0 5 10 15 20 25 30 35 40 > $250,000 $50,000 to $250,000 $10,000 to $50,000 < $10,000 Unsure of approximate range 0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100% Number of Responses Percentage of Survey Respondents 42 survey respondents Figure 3.7. Annual funds committed to instrumentation and monitoring of unstable slopes. 8, 20% 10 , 24% 11 , 27% 11 , 27% 25 , 61% 28 , 68% 4, 10% 4, 10% 6, 15% 3, 7% 2, 5% 1, 2% 6, 15% 11 , 27% 10 , 24% 4, 10% 6, 15% 1, 2% 23 , 56% 16 , 39% 14 , 34% 19 , 46% 4, 10% 5, 12% 0 5 10 15 20 25 30 35 40 Data management Installation of instrumentation and monitoring equipment Purchase of equipment and material from suppliers Ongoing maintenance and repair of in-situ installed instrumentation Remote Sensing Installation of warning systems 0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100% Number of Responses Percentage of Survey Respondents 75% to 100% 50% to 75% 25% to 50% 0 to 25 % Percentage of sevices performed in-house: 41 survey respondents Figure 3.8. Percentage of instrumentation and monitoring services that are performed in-house by DOTs.

State of the Practice 23 are installing and maintaining instrumentation and monitoring equipment and managing data in-house. Only infrequently are they installing warning systems or performing remote sensing in-house. When asked whether they perceived value from greater instrumentation and monitoring, only 19% indicated the programs were the right size, while others saw value in an expanded program. When asked what would enable an increased use of instrumentation and monitoring for unstable slopes in their agency, most states agree that additional funds, training, and agency geotechnical staff resources would enable increased use of instrumentation and monitoring for unstable slopes (Figure 3.9). 3.8 Data Management in Instrumentation and Monitoring Most states reported that they evaluate or interpret monitoring data for use in reporting or response actions on unstable slopes on a monthly (49%) or seasonal basis (51%). A few states evaluate data less than once every 1 to 2 years (14%), while others evaluate data every day (28%). The distribution of frequency among states is shown in Figure 3.10. Note that the sum of percentages is greater than 100% because agencies could select multiple options to account for varying interpretation frequencies for sites within their portfolio. Data collection frequency may be related to ease of access to the data. Most states reported that they are not using a web-based data acquisition and viewing system for instrumentation and monitoring data from unstable slope sites (71%). The other 29% of respondents who are using acquisition systems have either developed the web-based system internally, externally, or some combination thereof (Figure 3.11). Forty of forty-two states reported that they manage data by site and with site-specific technologies. Eight states also have a program-wide system that incorporates numerous or all sites in one database or system, and four reported some unique combination of site-specific and system-wide management as “other” (Figure 3.12). 12% 19% 21% 21% 40% 60% 60% 74% 5 8 9 9 17 26 26 32 0 5 10 15 20 25 30 35 40 Other None necessary – don’t perceive a need for increased use External contractor availability with specialty experience in instrumentation and monitoring Agency staff resources outside of geotechnical program Agency, FHWA, AASHTO, or other formal guidance and procedures Training Additional agency geotechnical staff resources Additional Funds 0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100% Number of Responses Percentage of Survey Respondents 43 survey respondents Figure 3.9. Suggestions for enabling increased use of instrumentation and monitoring for unstable slopes.

24 Advances in Unstable Slope Instrumentation and Monitoring 28% 37% 49% 51% 28% 14% 12 16 21 22 12 6 0 5 10 15 20 25 30 35 40 Daily Weekly Approximately monthly A few times per year Once every 1 to 2 years Rarely 0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100% Number of Responses Percentage of Survey Respondents 43 survey respondents Figure 3.10. Frequency that data obtained using instrumentation and monitoring technology are evaluated or interpreted for use in reporting or response actions on unstable slopes. Yes – internally developed 2% Yes – procured external services 17% Yes – a combination of internal and external services 10% No 71% 41 survey respondents Figure 3.11. Development of a web-based data acquisition and viewing system for instrumentation and monitoring data from unstable slope sites.

State of the Practice 25 3.9 How DOTs Use Monitoring Data Once Collected and Analyzed State DOTs reported that monitoring data is used for various purposes—the most frequent being tracking of movement or activity to trigger additional treatment actions and to establish the extent and rate of movement for use in design of stabilization solutions. More than half of respondents also use the data for supporting maintenance and operational decisions, improving reliability for site-specific hazard mitigation design decisions, and to establish whether movement is within tolerances for construction activities. Additionally, 40% of respondents use monitoring data for emergency or warning purposes (Figure 3.13). 2% 10% 19% 95% 1 4 8 40 0 5 10 15 20 25 30 35 40 Unsure Other A program-wide system that incorporates numerous or all sites in one database or system By site and the associated site-specific technologies 0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100% Number of Responses Percentage of Survey Respondents 42 survey respondents Figure 3.12. Data management methods. 0% 7% 31% 40% 57% 57% 67% 88% 93% 3 13 17 24 24 28 37 39 0 5 10 15 20 25 30 35 40 Other Public or other external stakeholder communications Research activities Emergency or warning Improve reliability for site-specific hazard mitigation design decisions To establish if movement is within tolerance for construction activities Supporting maintenance and operational decisions Establish extent and rate of movement for use in design of stabilization solution Tracking of movement or activity to trigger additional treatment actions 0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100% Number of Responses Percentage of Survey Respondents 42 survey respondents Figure 3.13. How data from instrumentation and monitoring of unstable slopes are used.

26 Advances in Unstable Slope Instrumentation and Monitoring While instrumentation and monitoring technologies are advancing, visualization and communication of monitoring data is still mostly done through site-specific reports prepared with conventional word processing and spreadsheet software or through instrumentation vendor-developed software and/or web-based systems. In contrast, some states have adopted the use of 3D image viewing software or virtual reality systems (Figure 3.14). 2% 7% 10% 14% 62% 90% 1 3 4 6 26 38 0 5 10 15 20 25 30 35 40 Other Third party (but not an instrumentation vendor) commercial software as a service platform 3D image viewing software or virtual reality systems Custom agency-developed/programed software or web- based systems Instrumentation vendor-developed software and/or web- based systems Site-specific reports prepared with conventional word processing and spreadsheet software 0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100% Number of Responses Percentage of Survey Respondents 42 survey respondents Figure 3.14. Methods used for visualization and communication of instrumentation and monitoring data from unstable slopes.

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Geotechnical instrumentation and monitoring technologies have been used to inform safety, operational, and treatment decisions for unstable slopes.

The TRB National Cooperative Highway Research Program's NCHRP Synthesis 554: Advances in Unstable Slope Instrumentation and Monitoring documents and synthesizes the state of practice for implementation and use of advancements in unstable slope instrumentation and monitoring by state departments of transportation over approximately the last decade.

The types of instrumentation and monitoring technologies range from devices installed on or in slopes to remote-sensing methods from ground, aerial, or satellite-based systems.

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