Case Study: Drilled Shaft Installation in Difficult Site Conditions-Loose Sand and High Groundwater Table

Selecting the most effective construction method for drilled shafts under the high groundwater table can be a challenging task that requires effective communication between the design and construction teams. Drilled shafts were designed to support a firewall for an electrical substation in central Texas. The subsurface consisted of interlayers of loose sands and soft clays under high groundwater table. The design recommended to install the shafts with temporary casing or slurry displacement due to the anticipated groundwater seepage through granular soils. During the foundation construction, it was very difficult to maintain the stability of the hole and the contractor requested to install the shafts using permanent casings. Therefore, the foundation design was modified to address the construction challenges and ensure that the shafts with permanent casing achieve the required load resistance. Effective and continuous communication among the owner, contractor, and design team during field shaft installation was key to mitigate the unforeseen challenges and successfully complete the project.