Finite Element Simulation Of And Inversion Analysis On The Loess Deep Foundation Pit Bracing

With the development of foundation pit engineering, the traditional design concept and calculation theory of foundation pit are already beyond the need. Based on practical engineering, the paper studies the effects of various parameters alteration on the stability of foundation pit and supporting system deformation by combining FEM simulation with on-site monitoring data. It is hopeful that this paper will afford benefit for the design and construction of similar foundation pits. The following are some work done in the paper:Comparing the FEM simulated results of common soil model with practical monitoring values, the paper finds that the soil body of the HS model is harder than that of MC model in unloading, and the simulated excavation of foundation pit of HS model has a better simulation result compared with that of MC model.The internal friction angle of soil, cohesive strength, volume weight, embedded depth of continuous wall, and the inner support prestress are key factors which have effects on the displacement of continuous wall. Among them, the internal friction angle has an obvious effect on horizontal displacement of soil retaining structure. The horizontal displacement value of retaining structure reduces significantly with the increase of friction angle value. When the embedded depth of continuous wall is rather small, the soil pressure is mainly undertaken by internal stay; when the embedded depth is quite great, the soil pressure is jointly undertaken by internal stay and soil in passive area. The increase of inner support prestress will decrease the horizontal displacement of vertical excavation surface or even result in partial reverse displacement.The elasticity modulus and severe of soil are important factors which affect the up-warping deformation of excavation basement. The embedded depth of continuous wall has little effect on basement up-warping deformation, which however shows a reduced tendency with the increase of the depth of embedded solid. And the change in inner support prestress has no influence on displacement value.The axial force of inner support is mainly affected by the internal friction angle, soil severe, thickness of continuous wall and the embedded depth. The axial force of inner support decreases with the increase of frictional angle value and increases with the increase of soil severe.Along with the increase of over-breakage of foundation pit, the horizontal level of continuous wall increases significantly and has a ascend trend as a whole tough different over-breakages of different excavation works have different effects on horizontal displacement of continuous wall. When the third layer of soil is over-broken, the first axial force will have an increase of 20.38 kN and the second axial force will have an increase of 41.47 kN. It can be seen that engineering accidents resulted by the over-breakage of foundation pit comprise a significant proportion.Based on detective values of practical engineering, the paper draws up inverse analysis program by making use of Matlab and makes the quadratic sum of the difference of inverse analysis value and detective value the standard to the inverse analysis of soil foundation coefficient. The calculated soil foundation coefficient agrees with on-site monitoring data and is also able to forecast the supporting structure displacement of foundation pit's subsequent condition. Therefore, it is operable to apply this method to forecast the displacement of foundation pit excavation.