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

As shown in Figure 9, with a failure wedge going underneath the potential building footprint with a FOS of about 1.0, the yield acceleration was estimated as 0.259. The corresponding earthquake -induced lateral ground deformation was estimated as 2.1 inches, which is within the allowable lateral displacement criterion (18 inches per Table 12.13.2 of ASCE 7-16). Note that since the ground improvement zone is approximately 30 feet away from the bulkhead, the current ground improvement plan is mainly for mitigating the lateral deformations of the foundations for the new building at Parcel A17; and is unlikely to reduce the kinematic soil loads on the sheet pile. Therefore, the current ground improvement plan will have small improvement on the lateral deformations of the sheet pile due to earthquakes. 5.3. Construction Considerations Rigid inclusion installation should be completed in general accordance with the best practices per the industry as detailed In the specifications that will be included In a separate design drawing submittal for Parcel A17. The anticipated construction sequencing is presented below: Excavate to the bottom of building foundation elevation as appropriate. iii Install rigid inclusions according to plans and specifications to the depth required to achieve 3-foot embedment Into the non -liquefiable layer. Top of the rigid Inclusions should be 2 feet below the bottom of foundations. • Overexcavate by 2 feet and replace with CSBC. The rigid inclusions should be installed using continuous -flight hollowetem auger. As is standard practice, the rigid inclusion concrete must be pumped under pressure through the hollow stem as the auger Is withdrawn. Maintenance of adequate concrete pressure at the auger tip is critical to reduce the potential for encroachment of adjacent native soils Into the concrete column. The rate of withdrawal of the auger must remain constant throughout the installation of the rigid inclusions in order to reduce the potential for necking of the rigid inclusions. Failure to maintain a constant rate of withdrawal of the auger should result in immediate rejection of that rigid inclusion element The contractor should adhere to a waiting period of at least 12 hours between the Installation of rigid inclusion elements spaced closer than 6 feet, center -to -center. This waibng period is necessary to avoid disturbing the curing concrete in previously cast elements. Concrete pumps must be fitted with a volume measuring device and pressure gauge so that the volume of concrete placed In each rigid inclusion and the pressure head maintained during pumping can be observed. A minimum line pressure of 100 psi should be maintained. And the rate of auger withdrawal should be controlled during concrete placement such that the volume of concrete pumped Is equal to 100 percent of the theoretical rigid inclusion volume per 60-inch segments. A minimum head of 5 feet of concrete should be maintained above the auger tip during wthdrawal of the auger to maintain a full column of concrete and to prevent hole collapse. A qualified geotechnical engineer should observe the drilling operations and instrumentation output; monitor concrete injection procedures; record the volume of concrete placed in each rigid inclusion element relative to the calculated volume of the hole; and evaluate the adequacy of individual rigid Inclusion installations to ensure that embedment requirements are met and that they are installed in accordance with the ground improvement plans and specrfications. GEGENGINEEkS 67 gclaCer3q 20211 osogn