Method for estimating three-dimensional effects on braced excavation in clay

Abstract

The maximum lateral wall movements are usually estimated by two-dimensional finite element analysis. However, three-dimensional effects due to the higher stiffness at the corner will result in smaller wall movements than that under plane strain conditions. This paper proposed a method to quantize the three-dimensional effects. The limitations of quantifying the three-dimensional effects by the current method were presented by analyzing an excavation case. A comprehensive parametric study was carried out to explore the effects of soil condition, support system stiffness, and the excavation geometry on the three-dimensional effects of excavation. The finite-element simulation results were represented by the plane strain ratio (PSR), and an empirical equation for PSR prediction was proposed considering soil condition, support system stiffness, excavation geometry, and distance from the excavation corner. The proposed equation was verified against case data reported in the literature, and the overall agreement was satisfactory. This equation offers a more reliable way to quantify the three-dimensional effects of rectangular excavation with internal struts in clay.