Research On Design Method Of Limit State Of Single Row Pile Support Structure Of High Cutting Slope

Based on the construction of the cutting slope retaining structure of the Lhasa-Linzhi section of the Sichuan-Tibet Railway,the two finite element models based on the m method and the p-y curve method are used to analyze the internal force of the working conditions.Based on the static analysis model and the random field theory,the random analysis of the field condition model is carried out to investigate the influence of the spatial variability of soil strength parameters on the variability of the maximum bending moment and shear force of the pile,which is verified by 2D simulation of Optum G2.Finally,the design value of pile resistance under different working conditions is solved according to the target reliability,and the corresponding safety factor is calculated.The safety factor of cantilever single-row pile structure under different variability geotechnical conditions is given.The main results of this paper are as follows:(1)According to the comparison between the measured data and the calculation results,the stress state of the cantilever single-row pile under the stable condition of slope is similar to that of the deep foundation pit.The static earth pressure is suitable to be taken as the initial forced state of the pile body.The applicability of the finite element model combined with the 8)method and the - curve method to solve the internal force of the cantilever pile is verified.(2)Random analysis shows that the variability of the strength parameters does not affect the mean value of the load values under the condition that the mean value of the soil strength parameters is constant.The mean value is basically the same as the calculation results of the deterministic analysis.The variability of the load value is positively correlated with the coefficient of variation and the correlation distance of the intensity parameter.The variability of the load value is more sensitive to the coefficient of variation of the strength parameter than the correlation distance.The variability of load values is more sensitive to friction angle variability than gravity under the condition of the same correlation distance.Under the same conditions of the same coefficient of variation of the strength parameters,the variability of the load value is more sensitive to the vertical correlation distance than the horizontal correlation distance.(3)Compared with the allowable stress method,the limit state method can consider the uncertain factors of the geotechnical environment,and can evaluate the structure in combination with the specific conditions of the working conditions scientifically and reasonably.According to the variability of geotechnical strength parameters,the rock and soil are divided into three categories: general variability soil,medium variability soil,and high variability soil.According to the safety factor which is calculated by limit state method,the recommended value of the safety factor of the single-row pile retaining structure of the cutting slope is given.Under the premise of the target reliability of 3.7,safety factor of the general variability soil takes 1.32;the medium variability soil is 1.48;the high variability soil is 1.63.