Analysis Of Inner-brace Supporting System Of Asymmetric Foundation Pit

In recent years, with the increasingly multilevel and bigger-scale exploitation and utilization of underground space, there are more and more intensive underground structures. Accordingly, the foundation pit engineering is increasing in scale and depth, and the condition of the surroundings becomes more intricate. Therefore, more emphasis is put on strength and deformation control instead of strength control in the design of foundation pit. The growing complexity of the foundation pit engineering makes asymmetric foundation pits a common problem. The asymmetry of foundation pit mainly refers to the differences of support structure, excavation depths, ground overloads and stratum conditions on the both sides of foundation pit, which cause asymmetric deformation and stress of foundation pit. There are more factors to be considered in the design, construction and monitoring of asymmetric foundation pits. Currently, the theoretical research on asymmetric foundation pit is very limited and mostly empirical.This paper mainly focuses on inner-brace supporting structure of asymmetric foundation pit. Theoretical analyses on lateral resistance coefficient of soil and the deformation and stress of supporting structure have been carried on, and then concrete examples are used to illustrate the deduced results. Finally, with the aid of finite element software, the deformation and stress of internal bracing type of asymmetric foundation pit has been studied combined with engineering examples. The main research content of this paper includes:(1) The analysis of stress-strain state of active and passive soil of foundation pit produced the respective lateral resistance coefficient of active and passive soil, and gave an explanation of the influence factors: the lateral resistance coefficient, the horizontal displacement of the supporting structure and the calculation point depth.(2) Based on lateral resistance coefficient of soil and principle of minimum potential energy, elastic overall structural method and improved overall structural method for asymmetric foundation pit are been derived. According to the theoretical results, the MATLAB program is programmed to solve two kinds of typical asymmetric foundation pit, and further make comparison with the monitoring data. The applicability of the two methods for asymmetric foundation pit is finally certified.(3) With the establishment of three dimensional finite element models of the internal-bracing type of asymmetric foundation pit, two kinds of asymmetric foundation pit, the difference of excavation depth and ground overload on both sides of the foundation pit, are analysised. On the one hand, the deformation calculation results of the foundation pit supporting structure of finite element method and common deformation overall structure method are compared and analyzed with monitoring data. On the other hand, the paper also studied on related factors, such as the equivalent axial stiffness of strut, earth pressure, the bending moment of supporting structure.