Numerical analysis of seismic performance of deep strutted excavation-structure interaction in sandy soil

Abstract

This research investigates numerically the seismic performance of deep-braced excavation in adjacent to 10-stories building in sandy soil. Non-linear time-history analysis using hardening soil model with small strain stiffness (HS-small) is performed using PLAXIS 2D. Numerical validation of a real case study of deep-braced excavation in Taiwan is implemented emphasis the accuracy and efficiency of the HS-small model in predicting lateral deformation of the diaphragm wall and settlement trough besides the shoring system. Beyond model validation, a calibration of mesh element dimensions, dynamic boundary conditions, and damping effect are implemented before a comprehensive parametric study is performed. The parametric study focusses on the effect of diaphragm wall stiffness and embedment depth as a key parameter in any design of shoring system on the seismic behavior of the shoring system and adjacent structure under Loma-Prieta (1989) earthquake record. Results show that for optimal seismic performance, wall embedment depth and thickness are at approximately 100% and (6–8%) of the ultimate excavation level, respectively. Results of dynamic lateral and vertical displacement of the diaphragm wall and surrounding area indicated that noticeable damage related to the supporting system of to the shoring system is expected and structural damage of the bearing elements of the adjacent structure is expected, as well. Results of dynamic straining actions along the diaphragm wall indicate a large increase in bending moments, shear forces and axial forces in struts by more than four times the static ones. The storey drift ratio of the structure in vicinity of deep excavation indicating a brittle failure to the non-structural elements is expected.