Study On Calculation Method Of Deep Foundation Pit Regarding Soil Pressure With The Influence Of Deformation

The following two issues in deep foundation pit are comprehensively studied in the paper. One is the calculation model of soil pressure considering the deformation. The other is the interaction of top beam, brace and ring beam. On the basis of the theory of the pile-soil consistent deformation, a new method of calculating deep foundation pit structures is presented, which can consider the effect of deformation. With the effects of top beam and brace on the retaining structures, a finite element program is designed in Matlab language.The main contents are as follows:1) The calculation model of soil pressure considering the deformation is presented. The results of model experiments from literatures[15,19] verify that the model can simulate the performance of rigid retaining structures under the non-linear condition. The determination of parameters in the model is discussed in details. For stress path in the passive zone of pit excavation, a modified coefficient of passive soil pressure is presented under the current research results. Based on the finite element method of elastical beam element, the new calculation of soil pressure of viscous soil with equivalent internal friction angle is presented, which can consider the layered soil.2) Based on the theory of the pile-soil consistent deformation, the principium of calculation method of retaining structure in deep foundation pit is fully explained. A finite element program considering the deformation of retaining structures (piles) is designed. Through the typical example to analysis the soil pressure and deformation of retaining structures, the effects of the cohesion C_cu, internal friction angle φ _cu , the pile stiffness EI and the value of Sa in the limited state of active soil pressure are discussed.3) The influenced mechanisms of top beam and brace on the retaining structures are analyzed respectively.4) A finite element program considering the influence of deformation, top beam and brace on retaining structures (piles) is designed. Ring beam is regarded as a horizontal pile, then an approach that can consider the integrated effects of top beam and brace is presented.5) Correctness and suitability are proved by the comparisons between the calculated and observed results through 2 typical practical foundation pit projects with different retaining structures.