Abstract: A Larson steel sheet pile system was used in a deep excavation supporting project. Due to the large difference between the actual excavation condition and the conditions assumed in the design, the partial deep excavation support system was observed to have an excessive lateral displacement and the deformation did not converge, which exceeds the deformation threshold value and even the control value of the design limit. After the field survey, factors that might induce the excessive deformation in the support system were analyzed. Mitigation measures of soil removal unloading at the outside of the support system, as well as the constructing soil berm inside the excavation side, were implemented so that the horizontal displacement of the deep excavation supporting system was effectively controlled. As a result, the overall excavation and foundation construction could be proceeded smoothly.

Key words: Larsen Steel Sheet Pile, Foundation pit engineering, Support type, Emergency disposal