Deformation Law Of Sandstone And Mudstone Interbedded Foundation Pit In Mountain Area And Displacement Back Analysis

In mountain area, sandstone and mudstone interbedded foundation pit often has a large span, medium parameters, complex construction environment and changing characteristics. Because of uncertain parameter values, constitutive model, initial stress and boundary conditions, using conventional analytical methods such as theoretical analysis and model tests to calculate and analyze geotechnical engineering, often lead to less than ideal results. The development of excavation monitoring techniques accelerates the popularization of information technology construction of pit. The improvement the information construction requirements makes obtaining all kinds of measured data information on the construction process become simple. Consequently, the use of survey data and a wealth of measured data information to establish the analysis model and inverse analysis model has important significance both to research the dynamic changes of rock and soil parameters in the construction process and to evaluate the site stability of the construction phase of the project.Based on a comprehensive analysis at home and abroad of deformation law of sandstone and mudstone interbedded foundation pit in mountain area and geotechnical displacement back analysis, at first,this paper researched the change of the foundation sidewall deformation with dynamic layer thickness, slope height and slope angle in sandstone and mudstone interbedded foundation pit. Then combining the simulated annealing algorithm and particle swarm algorithm, wrote MATLAB procedure based on SA-PSO and applied the procedure to engineering example to prove its effectiveness. At last, during the excavation of fourth of Chongqing rail Transit Jinshan station pit, this paper used displacement back analysis method based on simulated annealing-particle swarm algorithm and phased monitoring displacement data to evaluate dynamic rock mechanic parameter, and analyze the pit slope stability with strength reduction finite element method.Displacements of points in the side wall of the foundation pit relate to which layer they are in, and displacement of points in different layer relationship change greatly;The existence of slope on the right of the pit, increases the settlement of the points in the right side wall, and the higher the altitude and the greater the angle(the greater the "volume"), the greater the impact. In foundation pit with slope on one side, the pit sidewall with slope has different deflection to the other side due to different height and angle of the slope: the bigger the "volume" of the slope, the greater the degree of deflection.MATLAB program combined with ABAQUS finite element and SA-PSO can achieve good results meeting the engineering application when used in the back analysis of foundation pit. This phased displacement monitoring data reacts changes of rock parameters during different construction period. Rock mechanics parameters based on dynamic inverse can predict rock deformation to a certain extent.