Analysis Of Reliability For Bearing Capacity Of Composite Ground Of Gravel Piles

Reliability theory and probabilistic analysis have been widely used in geotechnical engineering. At present, composite ground is one of the most important problems in the field of geotechnical engineering and has seldom been studied with reliability theory, especially gravel pile composite ground. Gravel pile composite ground is very complex, so it is necessary to take into account many uncertain factors in gravel pile composite ground. In the present study,some problems of reliability calculation in geotechnical engineering and the reliability analysis of the bearing capacity of gravel pile composite ground are carried out. Soil properties data afforded in engineering exploration is discrete. The soil stratum has spatial variability and auto-correlation. For the purpose of estimation the value of soil property at a given depth,two statistical models which consider spatial variability and auto-correlation are discussed. Nonlinear Least Square Method (NLSM) is used in the calculation. The results show that regression variance obtained by the model, which introduce the dummy variable is the least among the literature can be seen. The random field theory of soil properties is discussed in the thesis. Through an example,auto-correlation distance of soil is given,and the probabilistic properties of spatial expectation of soil index,including the estimation of the trend and the calculation of the variance of the residuals off the trend,are studied. The theory of structural reliability used in the field of geotechnical engineering is briefly introduced. However,original variables are most likely to be correlated in the reliability analysis of geotechnical engineering and several methods of reliability index calculating are proposed . According to Non-dimensional Model (NDM),the 34-group bearing capacity test data of gravel pile composite ground from all over the country is collected and processed statistically and analyzed by the theory of structural reliability. The factors which affect the reliability index and the relationship between reliability index and safety factor are also studied,and some significant conclusions are drawn. The reliability of bearing capacity of gravel piles composite ground is analyzed by using the method of Random Field Model (RFM) which can take into account the spatial expectation peculiarity of soil index. In this model,the variance reduction of soil index and the uncertain factor of the area ratio formula of composite ground are considered. The factor of correlation of soil properties which affect the reliability index is also analyzed.