Back Analysis Of Soil Parameter Of Foundation Pit Based On The B-spline Function

Soil parameters of foundation pit are significant parameters in foundation engineering design process, which are obtained generally through indoor test. Due to the reasons such as variability of the soils, test condition, test method and so on, test results always be discreteness and be difference with the real value. Back analysis method based on monitor data is another effective way to determined soil parameters of foundation pit. Because of the complexity of the soil characteristics, backing analysis of the soil parameters of foundation pit is still in exploring stage. This paper according to monitor data, a back analysis method which combined back calculation using spline function and positive calculation using elastic support method is used to determine the soil parameters of foundation pit. The main research works in this paper are as follows:(1) Based on spline function, using monitor data to back calculate the inner force of retain pile. Using smoothing spline function based on some smooth rule and approximation rule to smooth monitor data, then, obtained the displacement spline function of retain pile by using B-spline function to interpolate the smoothing data. Derivate to displacement spline function to back calculate the inner force of retain pile.(2) Based on elastic support method positive calculate the deformation and inner force of retain pile. According the plane truss elastic support method, build the mechanical calculation model of foundation pit and use matrix displacement method to calculate the inner force of retain pile.(3) Back analysis the soil parameters of foundation pit. Within the scope of the soil parameters of foundation pit, enumerate large number of combination of soil parameters sample. Then taking them into the mechanical model one by one to calculate the deformation and inner force of retain pile. Screening out the soil parameters samples which its positive calculation value within the allowable tolerance of back calculate. At last, the soil parameters of foundation pit are obtained by doing statistical analysis to paramerters which screened out.(3) Applied the back analysis method to a typically engineering case and verified feasible of the method. Selecting an engineering case, using the back analysis method researched in this paper to determine its soil parameters of foundation pit, and take the inversion parameters into mechanical model of foundation pit to positive calculate the next stage deformation and inner force of retain pile. Compared the calculate deformation and inner force with monitor deformation data and back analysis inner force, the reliability of inversion result and feasible of back analysis method is verified.