| As the rock and soil mass is the natural product formed by geological processes,its discrete physical and mechanical properties are very large,coupled with the vast territory and complex geological conditions,so that the fixed value design method characterized by a single safety factor is often used in the geotechnical engineering design.However,the mainstream reliability design formula,which is represented by failure probability,develops slowly.Considering that strata with similar geological environment and history have roughly the same properties of rock and soil bodies,the random variation is more likely to obey the same statistical law,so establishing the reliability design theory of regional geotechnical engineering is a beneficial exploration to improve the design method.Based on the Copula reliability theory,this paper takes the typical soil layer in Zhengzhou area as the object,analyzes the statistical characteristics of the distribution of physical and mechanical property parameters of soil mass,and then studies the reliability theory of foundation pit engineering design,aiming at providing academic reference for establishing regional geotechnical engineering reliability design standards and specifications.The main contents of the paper are as follows:(1)A mathematical statistical analysis of the main physical and mechanical property indexes of more than 2000 groups of silty soil and 1100 groups of silty clay was carried out to obtain the characteristic statistics of soil property parameters in Zhengzhou stratum.The K-S hypothesis tests of the normal,lognormal and extreme distributions of the main parameters were analyzed,and the function fitting images of the three distributions were drawn to obtain the empirical distribution model of each parameter.(2)Through the normal information diffusion model,combined with the case analysis,the normal information diffusion model and the classical distribution model were respectively fitted and tested by K-S,and the applicability and superiority of the normal information diffusion method under the limited geotechnical parameter samples were verified by testing the calculation results.(3)The least square method was used for linear fitting,and the unitary linear regression model was used for regression analysis.The correlation coefficient r was used as the criterion for correlation strength to analyze the correlation among soil property parameters,including the correlation among soil weight,plastic limit,liquid limit,cohesion,internal friction Angle,compression coefficient and other parameters.The regression equation between soil property parameters is established,so as to analyze the correlation between each parameter and summarize the regularity.(4)Based on the reliability evaluation method of Copula theory and considering the autocorrelation of shear strength parameters,the correlation modeling of cohesion and internal friction Angle of soil shear strength parameters is carried out.The optimal edge distribution function was obtained by K-S test,and the optimal joint distribution function was identified by AIC,BIC and Euclidean distance criterion.Based on the joint distribution function,Monte Carlo simulation was carried out to study the reliability of foundation pit stability.The limit state equation of anti-uplift stability of deep foundation pit in the form of "pile row + internal support" is established,and the reliability index of anti-uplift stability of deep foundation pit is studied considering the parameter correlation. |
