Proceedings of the 43rd Annual Conference on Deep Foundations, 2018, Anaheim, CA, USA, (DFI)
Supported Excavation Movement Causing Lateral Displacement and Cracks in Drilled Shafts - Lessons Learned from a Case Study in Chicago
Amaneh E. Kenarsari, Ph.D., Project Engineer, M. ASCE, Eric R. Borys, P.E., Senior Project Engineer, M. ASCE, Brett Gitskin, P.E., Senior Principal Engineer and M. ASCE
This case study discusses impacts of excessive Earth Retention System (ERS) lateral movement at a project in city of Chicago. The ERS (cantilevered sheeting) moved inward towards the excavation and caused lateral displacement and cracks in six drilled shafts located about 1 to 2 lateral feet (0.3 to 0.6 m) from the face of the sheet pile wall. Up to 9 inches (23 cm) of horizontal movement was observed on top of the supporting sheet-pile. Similarly, survey measurements showed the top of the drilled shafts moved laterally up to 8 inches (20.3 cm). To evaluate the cause of failure and determine a remediation solution, the soil, shaft and site conditions were investigated. Pile Integrity Tests (PIT) were conducted at the affected drilled shafts. The shafts with identified anomalies were cored and video-recorded. The cause of the failure was determined to be related to variable soil conditions across the site, deeper excavation (i.e., increased effective ERS wall height), and other differences between design and as-built conditions. Internal bracing, in the form of walers and rakers, was installed to limit further movement of the sheet pile as a short-term solution, with additional grade beams framed into the basement slab-on-grade as a long-term solution. Five of the six cracked shafts were spliced with reinforcing bars and high strength grout and one shaft was replaced.
|article #3111; publication #1045 (AM-2018)|