The Initial Geo-stress Field Inversion Method Research On Lanzhou Water Source Project

With the development of engineering construction,more and more major engineering have been built in deep and intensive tectonic active regions which challenge the safety of engineering seriously.Because of the distributions of initial geo-stress are the prerequisites of analyzing the stability of surrounding rock,designing the excavation of rock engineering,and making decisions scientific.Therefore,accurate measurement and inversion of the initial geo-stress are the premise and key points for carrying out the risk assessment of construction accidents,disaster warning and reliable prevention and control.About the inversion precision of the current stress inversion method,This paper based on the engineering background of the project of Lanzhou water source and according to the measured data of geo-stress in the project,this paper presents a new method: numerical simulation analysis of the initial geo-stress field that is combined with multiple linear regression method and PSO-BP neural network method.The main part of this paper is as follows:(1)This paper introduce the research background of initial geo-stress and summarize the geo-stress measurement methods at home and abroad and their applicability and developing trend.a variety of geo-stress field inversion analysis methods and their advantages and disadvantages are introduced,Meanwhile,introducing the basic principle of the geo-stress inversion.(2)The paper introduced the engineering and geological conditions of Lanzhou water source project,Based on the data of initial geo-stress field that was measured in the construction site,the paper have carried out initial geo-stress field inversion analysis by using the multiple linear regression and nonlinear regression analysis method in Lanzhou water source project.(3)A new method of inversion that is combination with multiple linear regression and the PSO-BP neural network method is proposed.,which is based on multiple linear regression geo-stress inversion results,reconstruct the sample data,to carry out geo-stress inversion based on PSO and BP neural network model,using the method of the initial geo-stress field of engineering for the inversion analysis of the Lanzhou water source construction project.At the same time,to verify the rationality of the new method,using the experience in engineering analogy method to construct the experience in sample data,and the neural network inversion of initial ground stress.(4)By comparing the calculated values of the initial geostress of the engineering area with the above four in-situ stress field inversion methods,which are compared with themeasured values: Comparing to other methods,the proposed new method in both geo-stress magnitude and direction can both match well with the measured geo-stress data,especially in the area of geo-stress direction method has better accuracy than others.This paper proposed a new method of initial geo-stress field inversion that combine with multiple linear regression method and PSO-BP neural network method,which can consider a variety of geological tectonic movement of the load,displacement fields of model and the influence of gravity.It can also avoid the mistakes caused by the lack of experience when constructing the samples,In addition,Through the regression and back substitution,it can avoid the disadvantages that algorithm is affected by man-made factors and other random faults and effectively guarantee the accuracy of initial geo-stress field inversion.The results of this paper can provide a valuable reference for geo-stress field inversion of similar geotechnical engineering.