Influence of the Soil/Rock Conditions at Wall Toe on the Behavior of the Diaphragm Wall

Diaphragm walls are commonly used for supporting deep excavation when there are restricted setback conditions. The behavior of wall is influenced by variation of ground water table, surcharges, type and stiffness of supports, and encountered soil types. In this paper, diaphragm wall with two level of anchors supporting a 12.5 m deep basement excavation in mixed soil conditions has been discussed. There is considerable variation in the level of weathered rock within the project site, i.e., between 15 and 21 m. Panels of varying depth are identified based on the soil/rock conditions at wall toe. The performance of wall for different soil/rock conditions at wall toe has been analyzed by subgrade reaction approach. Design assumptions and results of the subgrade reaction analysis is validated by examining “no rock condition at wall toe” using Finite Element Approach. This paper compares theoretical deflections calculated with subgrade reaction approach with recorded wall deflections and discussed about the performance of retention system for various toe termination levels.