Study on Stabilizing Mechanism of Deep Excavation in Soft Clay Groud

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In recent years, the utilization of underground spaces has become a recognized necessity and deep excavations have been carried out extensively in urban areas. In such cases, it is important to elucidate the stabilization mechanism of the excavation. Particularly in the case of ground consisting of a soft clay, some aspects of its mechanical behavior remain to be studied.The purpose of this report is to contribute the design of lateral supporting systems for excavation. The following two subjects were mainly studied.(1) Earth and water pressures acting on braced walls in soft clayThe mechanical behavior of earth and water pressures acting on the back-and excavation-side braced walls in soft clay was investigated based on the results of detailed field measurements. Because mechanical behavior strongly depends on such factors as wall deformation, the groundwater state, and the deformation and strength properties of the soil, this study clarifies the relationship between mechanical behavi … More or and these factors. In particular, passive earth pressure on the excavation-side wall is separated into the two factors as an incremental term related to wall displacement towards the excavation side and a decremental term related to decrease of overburden pressure due to excavation.(2) Stabilizing mechanism of slurry trench excavation in soft clayThe stabilizing mechanism of a slurry trench excavation in soft clay under normal consolidation was investigated. Diaphragm wall construction, using the slurry trench method, is increasingly being applied to soft clay. To ensure the reliability of this method, it is important to clarify the stabilizing mechanism of slurry trench excavation. In this research it was recognized that the mechanism of trench wall stability in soft clay was to be studied. Consequently, normally consolidated soft clay yeilds only a slight trench displacement which achieves a balance between slurry and lateral pressures, thus permitting use of the diaphragm wall employing the slurry trench method. Less