Estimating and Contracting Rock Slope Scaling Adjacent to Highways (2020) / Chapter Skim
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From page 11... ...
11 The state of the practice detailed in this synthesis was gauged with a questionnaire designed for completion in about 30 minutes. The questionnaire was administered with an Internet- based survey tool and disseminated to lead geotechnical personnel in all 50 states; Puerto Rico; Washington, D.C.; and the Western, Central, and Eastern divisions of the Office of Federal Lands Highway.
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From page 12... ...
12 Estimating and Contracting Rock Slope Scaling Adjacent to Highways Two other noteworthy departures from this approach are two states that, either statewide or regionally, treated scaling mainly as a maintenance activity; those two jurisdictions (California and Idaho's District 6) are highlighted in the case examples section.
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From page 13... ...
State of the Practice 13 Design Efforts for Scaling Current publications regarding scaling did not have design criteria outlining how to estimate scaling efforts, debris quantities, or the types of efforts recommended for designing scaling plans and specifications (Andrew et al., 2011; Andrew and Pierson, 2012; Pierson and Vierling, 2012)
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14 Estimating and Contracting Rock Slope Scaling Adjacent to Highways For estimation of scaling debris such as loose rock, soil, and vegetation, there were no published guidelines or data to help DOTs estimate the volume of debris, or the data set was too narrow to apply nationally (Andrew et al., 2011; Andrew and Pierson, 2012; Duffy, 2018; Pierson and Vierling, 2012)
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State of the Practice 15 The questionnaire requested production rates that were considered "reasonable" by experienced design personnel. For consistency between geologic materials and project purposes, the respondents were asked to presume a non-presplit rock slope; a rock quality designation (RQD)
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16 Estimating and Contracting Rock Slope Scaling Adjacent to Highways rockfall mitigation duties, and as such may change roles midday. Questionnaire results indicated a wide range of common practices when paying hourly (Figure 12)
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State of the Practice 17 Figure 13. Tasks that are measured and paid as scaling.
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18 Estimating and Contracting Rock Slope Scaling Adjacent to Highways A few DOTs indicated that unit volume was measured by lidar scanner or photogrammetry by UAVs. Five DOTs indicated that they typically used a combination of measures depending on availability of survey equipment, truck scales, or urgent work necessitating the use of time and materials for measurement and payment.
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From page 19... ...
State of the Practice 19 Half of scaling states did not specify performance criteria, while the other half either indicated that they did have performance criteria or that scaling was performed to the satisfaction of the engineer or through site inspection. Specifying Temporary Protection Scaling dislodges large rocks that fall largely uncontrolled to the ground below.
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20 Estimating and Contracting Rock Slope Scaling Adjacent to Highways for temporary rockfall protection (Figure 21) , with a greater number of DOTs responding that the road was always completely closed, eliminating the need for protection.
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From page 21... ...
State of the Practice 21 Administering Scaling Activities During Construction Administering scaling during construction can require full-time technical specialists to direct scaling efforts, either from the ground or via rope access. This scaling-specific approach is often out of the ordinary compared with other highway construction activities, where construction inspectors or engineers supervise construction with occasional input from technical specialists.
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22 Estimating and Contracting Rock Slope Scaling Adjacent to Highways 1. Experienced designer with on-slope verification 2.
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State of the Practice 23 1. Yes, we plan to use advanced techniques to measure scaling completion and area coverage 2.
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24 Estimating and Contracting Rock Slope Scaling Adjacent to Highways Lessons Learned At the end of the questionnaire, 18 of 24 scaling states provided input on the lessons learned regarding scaling over the previous 10 to 20 years. The responses covered a wide range of topics, many of which were touched upon in the survey questionnaire and complemented by open-ended responses.
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From page 25... ...
State of the Practice 25 [Problems have occurred when] extensive vegetation has obscured some areas of the rock cut, making it difficult to predict actual rock slope conditions, leading to change in design once the vegetation is cleared [or]
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