Laserfiche WebLink
AFS Response to DRMS Geotech Review#3 September 30, 2021 <br /> DRMS Geotech Review#3 September 26, 2021 Comments: <br /> With confirmation of the slope angle error for the low strength rock(Xb)discussed in the Exhibit,the <br /> Division reconstructed the slope profile for 10-ft-thick Xb at a 35 degree angle under seismic conditions <br /> (Sensitivity Analysis)in the slope stability software,GALENA. However,the factor of safety result of the <br /> Division's slope stability analysis is still below the Division's requirement under Section 30 of the <br /> Policies of the Mined Land Reclamation Board. <br /> Additionally,the Division performed an additional slope stability analysis for the same slope profile but <br /> under static conditions. The resulting factors of safety is summarized below in comparison to the results <br /> provided by Walstrum and the requirements of the Division for the updated GALENA model. <br /> Factors of Safe -Walstrum S ur Amendment <br /> Section Seismic Galena Walstrum DRMS <br /> Coefficient Requirements <br /> *2 0 1.15 N/A N/A <br /> *2 0.12 0.92 1.15 1.15 <br /> *Hypothectical Model-10 ft.thick low strength rock @ 35 degrees <br /> As shown in the above table,the Division model for the slope profile of 10-ft-thick Xb at a 35 degree <br /> angle under static conditions resulted in a factor of safety of 1.15. The results summarized above leads the <br /> Division to believe the difference in results is either from 1) differing modeling software and <br /> methodology and/or 2) seismic conditions were potentially not included in the Walstrum sensitivity <br /> analysis. When reviewing Walstrum's resulting slope stability profile visual for the Sensitivity Analysis <br /> found in Appendix I,there is no indication a seismic coefficient of 0.12 was applied to the model outside <br /> of the associated title.At the moment,there is no way for the Division to confirm the application of a <br /> seismic condition to the Sensitivity Analysis. <br /> Based on the following discussion,please have Walstrum discuss and/or provide the following: <br /> • Please have Walstrum confirm that the appropriate seismic condition was applied to the <br /> Sensitivity Analysis provided in the Exhibit. <br /> • If the appropriate seismic condition was applied to the Sensitivity Analysis provided in the <br /> Exhibit, please have Walstrum provide the numerical results that outline all parameters, <br /> variables and results for the Sensitivity Analysis for the Division's review. <br /> AFS Response September 30. 2021: <br /> We reviewed the inputs for the sensitivity analysis in the Geotechnical Stability Exhibit and <br /> confirm that the appropriate seismic condition was applied. Regarding your request for the <br /> numerical results that outline all parameters, variables, and results for the sensitivity analysis, the <br /> SLOPE/W program requires data entry of parameters via input screens. Therefore, Attachment I <br /> presents screenshots as follows: 1 page of definitions of input screen data; 1 page of definitions <br /> of output screen data; and 2 pages each of input/output for 10 ft static, 10 ft dynamic, 20 ft static, <br /> and 20 ft dynamic sensitivity analysis. Attachment 2 provides an updated Table 5 (page 31 of 35) <br /> and Attachment 3 provides an updated Appendix I (page 4 of 8)to more accurately indicate the <br /> hypothetical nature of the sensitivity analysis as explained further below; the revised pages also <br /> show an updated result (FoS of 0.98, previously 0.95) for the 20 ft dynamic sensitivity analysis <br /> hypothetical condition due to a difference in number of iterations during the model run. <br /> Page 2 of 3 <br />