Research On Reliability Design Method Of Spiral Pile Composite Foundation

Based on the reliability theory of geotechnical engineering,this paper makes an in-depth study on the reliability analysis of the bearing capacity of spiral pile composite foundation based on the limit state design method,which provides a calculation for the bearing capacity calculation of the design and construction of the spiral pile composite foundation.Firstly,according to the bearing capacity formula of single pile and the bearing capacity formula of composite foundation,the limit state equation is obtained.Then,according to the JC method,the MATLAB program is used to calculate the reliable index under the conditions of cohesive soil,silt soil and fine sand.The general separation method is used to calculate the partial coefficients of each function calibrate.Finally,the sensitivity analysis method is used to analyze the coefficient of variation of each variable and the influence of various parameters in the function on the reliable index.(1)Reading the literature data,determining the function function according to the calculation formula of the bearing capacity of the single pile of the spiral pile and the bearing capacity formula of the composite foundation,performing statistical statistics on the random variables in the function and determining the distribution type and parameter range of the random variables.(2)According to the JC method,the MATLAB is used to calculate the reliability index of the composite foundation of the screw pile under the condition of cohesive soil,silt soil and fine sand,and the results with reference value are obtained.(3)Using the general separation method,the resistance and load of the bearing capacity of the spiral pile composite foundation under three conditions are separated and calculated,and the corresponding resistance partial coefficient and load partial coefficient are obtained respectively.Finally,the obtained partial coefficients are calibrated to determine the rationality of the results.(4)Considering the coefficient of variation of random variables and the influence of various parameters in the functional function on the reliability index,the sensitivity analysis method is used to analyze and analyze the coefficient of variation of the end resistance and the reduction factor of the natural foundation bearing capacity to the reliable index.It is greater impact.