920 MILLWRIGHT LOOP S BASE FILE Geotech Report 2023-12-29

Cad.& Bulkhead 34uMurea The bulkhead structures that were modeled in the slope stability analyses include sheet pile and deadman anchorage system. Based on our discussion with the project team on July 22, 2021, we understand that the current tleadman anchorage system consists of a relatively newly constructed continuous concrete tleadman with an old concrete tleadman sitting in front of R. The two rows of tleadman are located about 50 feet behind the sheet pile wall, functioning as a whole, with regularly spaced tiebacks connecting the sheet pile wall face to the concrete deatlman. Per the design drawing, the tip of the sheet pile is at Elevation -35.00 feet, therefore, embedded in the liquefiable layer (recent deposits). When liquefaction occurs in seismic and postearthquakeconditions, the bulkhead structures (sheet pile and tiebacks) will deform with the liquefiable soils and Is unable to provide lateral resistance. Hence, in our slope stability analyses, the sheet pile and tiebacks were only modeled in static condition. The tieback tensile capacity was obtained from the design drawing as 82 kips with a spacing of 8.25 feet. The sheet pile shear strength was estimated as 354.5 kips per linear foot correspondingto an AZISsection according to the design drawing. CIIA.CSurcharge Loam Based on the collaboration with PND, the surcharge load within the building footprint is 185 psf In static condition and 100 per in seismic and postearthquake conditions. C3A.S.Slope Stablllb Result Figures 6 and T present the slope stability analysis results for Cross Section A -A'. In static condition, the factor of safety (FOS) was evaluated as 2.04 corresponding to a critical failure surface going beneath the Up of the sheet pile, which indicates a stable condition. In postearthquake condition, the FOS was estimated less Nan 1.0 within the building footprint (Figure T), which indicates that unstable slope condition would result in excessive slope movement; therefore, there is no need to check the seismic condition. 4.3.2. kinematic Loads and Inertial Loads The effect of earthquake -Induced lateral ground deformation on the below -water structures (i.e., sheet pile, pile foundations) is represented by the kinematic load that should be included in the structural analysis. Based on the back analysis of case histories (Finn and Fuji s 2004) and our past project experience, the average lateral spreading induced kinematic soil pressure Is estimated to be about 30 percent of the total overburden pressure, which in this case is triangularly distributed with a magnitude of 36H, where H is the lateral spreading depth, estimated as the depth from ground surface to the failure surface in post - earthquake condition. And the triangular kinematic soil pressure of 36H was estimated based on the 30 percent of the total overburden pressure with a total unit weight of 120 pd. 5.0 GROUND IMPROVEMENT RECOMMENDATIONS Based on the collaboration with FIND, we understand that due to the potential liquefaction issue at the site, ground improvement with rigid inclusion was selected as the foundation support for the buildings at Parcel AST to mitigate the ground deformations, including static and seismic (liquefactioninduced)settlements, GWENGINEEaS 67 BcfaCer3p 111,W 0 Ni1 Rules