Challenges of Building the Deepest Basement in Downtown San Jose-PPT Presentation

PPT Presentation

Pdf Summary

The 200 Park Avenue project involved constructing a 19-story tower with four basement levels in downtown San Jose. Excavation extended approximately 54–58 feet below ground, making it one of the deepest basement projects in the area.<br /><br />Investigations identified alluvial clay over upper and lower sand-and-gravel layers, with bedrock at roughly 1,000 feet. Groundwater was shallow, and artesian pressures were measured at different depths. These conditions created risks of wall movement, settlement from dewatering, and excavation-base heave or blowout.<br /><br />The selected temporary shoring system was a soil-cement-mixed (CSM) wall with four levels of tieback anchors. The wall panels were 39 inches thick and 135–140 feet long, designed to provide stiffness, limit groundwater movement, and extend deep enough to help depressurize the lower sand-and-gravel layers.<br /><br />Construction monitoring included piezometers and inclinometers. Results indicated that the wall remained sufficiently stiff during excavation, groundwater levels outside the excavation stayed stable, and perimeter settlements were relatively minor. Overall, the shoring design effectively managed ground movement and groundwater-related risks.

Keywords

200 Park Avenue

San Jose

deep excavation

19-story tower

four basement levels

soil-cement-mixed wall

tieback anchors

groundwater control

piezometers

inclinometers