Study Instability Mechanism And Optimal Design Of Supporting Scheme For Loess Deep Foundation

In this paper,study the instability mechanism and corresponding failure modes of loess deep foundation pit under different geological conditions.According to the failure mode,given two or more preliminary design schemes,and choose a kind of scheme which not only economy but also to meet the safety requirements of the program.China's research on deep foundation pit is still lacking,the research on loess deep foundation pit is relatively less,the article about the loess deep foundation pit research is still very meaningful.Through the study of loess in Xi'an,selecting single layer and more double layers formation structure to analyze.Using of finite element software can study them failure modes,analyze of loess foundation pit slope instability mechanism and guide how to select design scheme about the loess deep foundation pit.To cite the actual engineering of Xi'an and analyze the composite structure of soil and loess foundation,it designed the three schemes for the this pit.Through the finite element studying the three schemes,taking into account the multi-factor,the final selection of composite soil nailing wall is the best scheme.After selecting the best scheme,its further optimization can reduce the project cost and save resources under the safety conditions.Finally,the feasibility of the optimization scheme is verified by comparing the monitoring data with the results of the finite element simulation.The main results are as follows:1)It selected reasonable parameters about different groups of loess foundation pit combined with relatively wide distribution in Xi'an and combined with some practical project.It analyzed the failure modes of using finite element,which are divided into slice?type and partial collapse.2)It selected an engineering example of loess and fill composite structure foundation pit in Xi'an,and designed three kinds of supporting structures scheme,there were anchor single row pile,anchor double row pile and composite soil nailing wall;The soil nailing wall was the best scheme,which determined by the influence of the size of the support scheme,the safety factor,the project cost,the difficulty of the construction and the influence on the surrounding environment with using the finite element of analyzing.3)With further optimized the soil nailing wall support structure scheme It is mainly to reduce the slope ratio,increase the composite soil nail spacing,reduce the diameter of steel bars,and reduce the length of soil nails and anchor,it saved about 615600 yuan than original scheme;and it verified the feasibility of the best scheme compared with the site monitoring data.