Jet Grouting for the Mitigation of Excavation Wall Movements in Glacial Silts

This paper describes the innovative application of jet grouting to improve the stability of a bottom-up construction in sensitive glacial silts. The construction involved a 51- to 69.5-ft-deep excavation supported by internally-braced secant pile walls adjacent to existing fragile buildings which needed to be protected. The excavation design was complicated by the large difference in subgrade levels within the excavation. An integrated grout slab and gravity wall was pre-formed in situ prior to excavation using jet grouting to enhance excavation support. Numerical modeling was used to study the behavior of the jet grout elements for controlling deep-seated inward wall movement. The results of quality control testing on cored samples taken through the grouted glacial silts are discussed. Inclinometers installed in the secant pile walls confirmed that wall deflections achieved during excavation were less than 1.2 in. (or 0.15% of excavation depth).