Behavior of Isotropic and Anisotropic Diaphragm Walls in Finite Element Analysis Model of Deep Excavation

The diaphragm wall of the deep excavation pit is the Barrette pile connected, standing side by side in a row to create a diaphragm wall system, so that the flexural stiffness of the diaphragm wall in the vertical and the horizontal direction is different. That is, the horizontal stiffness (axis 2) will be less than the vertical stiffness (axis 1) E2I2 << E1I1. In this study, the author analyzes and simulates the Barrette pile diaphragm wall system working according to the 3D model of the Song-San excavation project located in the K1 area of ​​the Taipei basin, Taiwan. The results are checked and compared with the actual measurement results. Through the process of analyzing and observing the obtained results, the author draws a few conclusions as follows: Firstly, the influence of the corner effect and the stiffness of the diaphragm wall in the horizontal direction is realistic and needs to be considered. In consideration, it is necessary to simulate the deep excavation according to the 3D model to analyze and properly evaluate this problem. Secondly, the simulation of the deep excavation according to the 2D model only properly evaluates the behavior of the diaphragm wall in the middle of the long edge segment (L) of the excavation, on the middle L/2 segment and when considering the behavior of the diaphragm wall on the L/4 segment from the corner of the diaphragm wall, it should be considered on the 3D model. Third, in order to quickly model and save time for discrete analysis of many elements, in preliminary calculations, it is possible to accept the diaphragm wall simulation as a continuous wall (W-IP) combined with correction the stiffness of the diaphragm wall in the horizontal direction through the ratio n = I2/I1 = 0.76.