1400 W MARINE VIEW DR WATERFRONT PLACE APARTMENTS 2022-04-04

Table 3-2 Summary of Soil Layers and Properties Material Name Typical USCS c Liquefied Mt' E' v, (pcf) (deg.) (psf) Su,r (ksf) (ksf) FILL 0-SP-SM SP-SM, SM 125 35 0 na na 1000 0.3 0.08*a'vo>_ FILL 1 -SM SM,SP-SM 115 30 0 190 psf na 145 0.3 FILL 2-ML ML 115 na 1100 Na 20 15 0.3 0.08*6'„o>_ FILL 3 -SM SM,SP-SM 115 30 0 190 psf na 145 0.3 0.22*(5'vo Recent Deposits SP-SM 120 33 0 540 psf na 784 0.3 TILL 1-SP-SM SP-SM 130 39 0 na na 2000 0.3 3.2 Liquefaction Lateral Spreading Liquefaction lateral spreading displacement estimates were calculated using a Newmark approach. The horizontal yield acceleration3 was calculated using the limit equilibrium slope stability analysis program SLIDE V2018 by Rocscience. Spencer's method of slices was used in the SLIDE program. Then the Bray and Travasarou(2007) method was used to estimate the median displacement associated with the yield calculation. A representative cross section drawn in the east-west direction through the middle of the south building was analyzed for stability. The cross section is generally aligned with CPT-6 -14 and-19, and boring B-3 and the stratigraphy was established based on these explorations. The cross section extends to the west beyond the bulkhead into the water. The configuration and condition of the bulkhead is unknown and thus our analysis assumed that it does not provide resistance to lateral spreading. In our analyses only a nominal building surcharge of 75 psf was included. This was considered conservative and reasonable since: 1)the failure surfaces are relatively flat in the building footprint and thus the building weight does not translate to a driving force; 2)the strength of the liquefiable soils increase with vertical stress so including the surcharge would lead to higher liquefied soil strengths which is unconservative; and 3)support by the DSM would tend to transfer the building loads to deeper layers that don't contribute to the slope stability. 3.2.1 Existing Conditions In the existing site condition without ground improvement a seismic yield acceleration of 0.033g was calculated. The displacement associated with this yield acceleration is about 3 feet, which is consistent with GeoEngineer's assessment that lateral spreading hazard is significant at this site. The slope stability and displacement calculations for this case are presented in Appendix A.2. 3.2.2 Ground Improvement Condition A zone of CDSM ground improvement encompassing the building footprint was considered for design. The yield acceleration of 0.198g was found to correspond to a median displacement of 2 inches using the Bray and Travasarou(2007)method. An undrained shear strength was used to characterize the shear strength of the composite CDSM and native soil. The composite strength was varied until the yield 3 The horizontal yield acceleration is that which generates a factor of safety of 1.0. In is indicative of the level horizontal shaking required to initiated horizontal displacement on a slide surface. 6I