Analysis Of Three-Dimensional Effect And Earth Pressure Of Foundation Pit

Foundation pit and retaining system are spatial structure. In recent years, the research on three-dimensional effect of foundation pit was paid much attention to in engineering and academic field. In this paper, the three-dimensional numerical modeling of the foundation pit was established by the finite element software ANSYS. The excavation processes of the pit with non-supporting structure and with cantilever piles retaining structure were modeled. The spatial distribution of the pit lateral displacement and earth pressure were comprehensively analyzed.Firstly, the excavation process of the foundation pit with non-supporting structure was numerically simulated. The distribution of the pit lateral displacement with every step of excavation was analyzed. The influence of the pit-corner angle (900, 1200, 1500, 1800 and external corner 900) on the displacement was studied. The area affected by the pit three-dimensional effect was analyzed when the pit corner varied from negative angle to positive angle. In addition, the lateral displacement distribution of the pit with non-supporting structure was computed by the complementary error function, and the calculated values of function and results of finite element were compared and analyzed.Secondly, the cantilever pile retaining structure of a rectangle pit was researched using numerical simulation. The excavation process of the pit, the spatial distribution of lateral movements, the bending moment of piles, the settlement of earth surface around the pit and its scope was analyzed. The rationality of computing lateral displacement of the pit by complementary error function was discussed.Additional, according to Ranking's theory of earth pressure considering displacement, the earth pressure of the piles in cantilever pile retaining structure was computed by the results of horizontal displacement from the finite element analysis. For the corner pile and the middle pile, the above results of earth pressure, the active and the rest earth pressure by Ranking's theory, were compared. Furthermore, the distribution and the state of earth pressure in the practical situation were studied.Finally, a deep foundation pit with double-row piles example in Handan, Hebei province, was computed by ANSYS. The changing laws of displacement field and internal force of piles in the excavating process were analyzed. These results were compared with the test data in site, which verifies the rationality and applicability of the calculating model.