Soil Mechanical Parameters Back-analysis Based On BP Neural-Network And Its Engineering Applications

Technology of pile foundation is usually used in the modern construction of large civil engineering. As one of the foundation forms, pile foundation is widely adopted not only in the general soil region, especially in the construction of buildings which are built in poor soil(especially in high-rise buildings, heavy workshop, and have special requirements of structures),but foundation settlement, to the geotechnical engineering worker,is always one of the most concerned problems.This paper is based on the background of a pile foundation project, in this paper FLAC3 D is used to establish numerical analysis model(single pile static load test) on the basic of single pile static load test on site and stratigraphic data, then different plans are designed by orthogonal test, then been calculated and we will get the deformation data under different working conditions. The BP neural network toolbox of MATLAB is used to get the inversion of field soil geotechnical parameters on the basis of calculated data. Make comparison between the inversion of data and the data in survey report and analyze the different. According to the data of the inversion of the soil parameters and the other data gave by the units of survey and design, this paper uses FLAC3 D to establish a group of three dimensional numerical model of pile caps and calculates deformation and stress distribution of the whole project.By contrasting the calculated data and the measured deformation data, this paper gets the following conclusions:(1) Using FLAC3 D to set up single pile model, and using the Simulation with different schemes of geotechnical parameters for single pile settlement under different load data and its corresponding geotechnical parameter for the training sample database, on this basic this paper make to train the BP neural network, then to measure single pile with the trained network simulation, this method is feasible to obtain geotechnical parameters.(2) For the engineering project of geotechnical parameters which needs inversion, when calculating of different soil we can only make the inversion of needed deformation modulus because of the poisson’s ratio range is limited and the influence of displacement field is also limited.(3) For the geotechnical engineering projects which have no condition for inversion but need numerical calculation, we can obtain satisfactory results under normal circumstances by making a proper correction of modulus of deformation, The scope of Suggestions this paper has given is E0=3~10Es,different areas and different soil layer may be different, need to debug for many times.