Dingee Reservoir Final Seismic Report - East Bay Municipal Utility ...

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Based on our above evaluations of the Dam fill and native materials, we do not anticipate that the onsite materials will undergo liquefaction or significant strength loss during seismic loading. 6.4 Shear Strength To estimate the shear strength of fill, native, and sandstone bedrock materials, three types of testing were conducted: 1. Isotropically consolidated undrained (ICU) triaxial compression test with pore pressure measurement. 2. Unconsolidated consolidated (UU) triaxial compression test. 3. Direct Shear Test (DS). In general, the results of the ICU tests provided the most appropriate results and were most suitable for use in the analysis. UU and DS tests were also considered; however, due to the larger scatter in the results, these were not used. Direct shear test results were conducted mostly on the fill materials. Results from the ICU tests were used in developing shear strength parameters for the fill, native materials, and sandstone bedrock. 6.4.1 Effective Shear Strength Failure Envelope The static shear strengths of the dam fill and foundation materials were estimated using Isotropically Consolidated Undrained (ICU) Triaxial Compression tests with pore water pressure measurements. Plates 12, 13, and 14 show the effective strength failure envelope for the dam fill, native material, and sandstone bedrock, respectively. The effective material strength parameters used in the analysis are shown in Table 4A. Material Table 4A: Effective Shear Strength Parameters Moist Unit Weight m (pcf) Cohesion Intercept c’ (psf) Friction Angle’ (degree) Ref. Plate No. Dam Fill 126.8 172 29.0 12 Native Materials 127.3 616 13.0 13 Sandstone Bedrock 132.2 1223 19.9 14 6.4.2 Total Shear Strength Failure Envelope For the seismic (pseudo-dynamic) analysis, undrained shear strength was used. For this study, we used the static total strength parameters from the ICU tests. Plates 15, 16, and 17 show the total strength failure envelope for the dam fills materials, native materials, and weathered bedrock, respectively. The total material strength parameters used in the analysis are shown in Table 4B. Results of the ICU triaxial tests are summarized in Table B-3 in Appendix B. Seismic Stability Evaluation Report Dingee Reservoir Dam 14 August 2008
For slope stability analyses, both the effective and total strength parameters derived from the “best fit” line were used. Table 4B summarizes the “best fit” material total strength parameters. Clayey soils exhibit an increase in shear strength during rapid or seismic loading cases. The phenomenon of increase in strength for clayey materials has been well-documented by previous studies and is a generally accepted standard of practice (Duncan and Wright, 2005). Typically, a shear strength increase of 20 percent or greater can be used for earthquake loading conditions for clayey soils. In this report, we took a more conservative approach, and did not apply any shear strength increase due to the size of the embankment and the anticipated embankment deformations. Stability analyses were performed using no strength increase and are presented in Section 7. Material Table 4B: Total Shear Strength Parameters Moist Unit Weight m (pcf) Cohesion Intercept c (psf) Friction Angle (degree) Ref. Plate No. Dam Fill 126.8 416 16.0 15 Native Materials 127.3 806 6.9 16 Sandstone Bedrock 132.2 851 19.9 17 Seismic Stability Evaluation Report Dingee Reservoir Dam 15 August 2008
Page 1 and 2: Seismic Stability Evaluation Report
Page 7 and 8: 1.0 Introduction 1.1 Background Thi
Page 9 and 10: 2.0 Project Description 2.1 Site Se
Page 11 and 12: 3.0 Geotechnical Exploration and La
Page 13 and 14: advanced using a hollow stem auger.
Page 15 and 16: 3.3 Laboratory Testing Soil and roc
Page 17 and 18: 5.0 Subsurface Conditions Based on
Page 19: Native Material The in-situ moistur
Page 23 and 24: We have tabulated the results for b
Page 25 and 26: Table 8 Seismic Slope Stability Ana
Page 27 and 28: 8.0 Conclusions and Summary of Dam
Page 29 and 30: Mitigating Liquefaction Hazards in
Page 31 and 32: Reservoir Roof B A A’ XV-11 (Sta.
Page 33 and 34: DINGEE RESERVOIR DAM SEISMIC STABIL
Page 35 and 36: Elevation (Feet) 780 770 760 750 Re
Page 37 and 38: U-Line: PI =0.9*(LL-8) 60 50 40 30
Page 39 and 40: Total Density (PCF) 775.0 770.0 765
Page 41 and 42: 0.200 0.300 0.400 0.500 0.600 0.700
Page 43 and 44: 5000.0 4500.0 4000.0 3500.0 3000.0
Page 45 and 46: 5000.0 4500.0 4000.0 3500.0 3000.0
Page 47 and 48: 5000.0 4500.0 4000.0 3500.0 3000.0
Page 49 and 50: Material m (pcf) Dam Fill 126.8 Na
Page 51 and 52: Material m (pcf) sat (pcf) c (psf
Page 53 and 54: Material m (pcf) sat (pcf) C T (p
Page 55 and 56: 1.5 Displacement (ft) 1.0 0.5 Kobe
Page 67 and 68: Appendix B Laboratory Test Results
Page 69 and 70: 2 62 63 64 65 66 67 68 69 70 71 72
Page 71 and 72:
TABLE B-1 SUMMARY OF LABORATORY TES
Page 73 and 74:
TABLE B-3 SUMMARY OF CONSOLIDATED U
Page 75 and 76:
TABLE B-4 UNCONFINED COMRESSION TES
Page 109:
Appendix C Reference Drawings: LIST
Page 125 and 126:
Appendix E Ground Motion Studies Pa
Page 127:
The next Generation Attenuation rel
Page 130 and 131:
Table 1 Target Response Spectrum: A
Page 132 and 133:
Figure 1. Median plus 1-sigma respo
Page 134 and 135:
Figure Set 2 (cont.) PACIFIC ENGINE
Page 136 and 137:
Page 138 and 139:
Page 140 and 141:
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