Suggested deformation control approach for braced excavations incorporating corner and soil arching effects

This paper proposes a deformation control approach for braced excavations by incorporating both corner and soil arching effects into an integrated optimization framework. The corner effect was quantitatively described using the plane strain ratio, which served as the basis for deriving an optimization formula for the retaining pile diameter. In parallel, a governing equation for the horizontal soil arch axis was developed under static equilibrium conditions, and then the ultimate arch span was determined using the twin-shear unified strength theory. A comprehensive effectiveness assessment for the approach was conducted on an actual deep-braced excavation adjacent to a subway tunnel using finite element analysis. The results show that the proposed approach effectively reduced the diameter of retaining piles within the high and medium impact zones of the corner effect, while strategically placed arch foot piles (AFPs) facilitated the formation of soil arching. The deformation pattern of the retaining piles displayed a multi-arch profile, with the maximum lateral displacement reduced by approximately 0.032 % of the excavation depth (H_e). The extent of the sharp decrease zone of soil horizontal displacement decreased from 1.1H_e to 0.9H_e. Among the geometric parameters of the AFPs, the sectional width was found to have the more significant influence on deformation control. Furthermore, the applicability of the proposed approach was assessed in different soil conditions. The results indicate that soil properties affect the effectiveness of deformation control. Among the soils tested, silty sand was the most conducive to soil arching, followed by silt, whereas silty clay exhibited the weakest arching behavior.