Study On Bearing Characteristics Of Pile Foundation Considering Spatial Variability Of Soil

Pile foundation is a kind of foundation form with high bearing capacity,wide application conditions and long history,which is widely used in geotechnical engineering.At present,the deterministic design method is basically adopted in its design.However,rock and soil are the products of nature,with strong spatial variability.Therefore,it is necessary to study the influence of spatial variability of soil properties on pile foundation.In this paper,considering the variation coefficient of undrained shear strength c_u,vertical and horizontal correlation distance,distribution form and nonstationarity,the influence of spatial variation of soil parameters on the bearing capacity of single pile is studied by stochastic finite element method.The main work and achievements are as follows:(1)The deterministic analysis and stochastic simulation analysis of vertical and horizontal loading of single pile are carried out respectively,and the results of deterministic analysis and stochastic simulation are compared.The results show that the load displacement curve of single pile is the same whether considering the spatial variability of soil property or not,but compared with the results of deterministic analysis,the mean value of bearing capacity of single pile decreases significantly after considering the spatial variability of soil property.With the increase of coefficient of variation of undrained strength of soil,the mean value of vertical bearing capacity and horizontal bearing capacity of single pile decreases,while the standard deviation increases.With the increase of vertical correlation distance,the mean value of vertical bearing capacity of single pile will significantly reduce while the standard deviation increases.The mean value of horizontal bearing capacity of single pile will significantly increase with the increase of horizontal correlation distance,and the standard deviation of horizontal bearing capacity of single pile will significantly increase with the increase of vertical and horizontal correlation distance.For the vertical and horizontal single pile obtained by numerical simulation,the bearing capacity can be described by lognormal distribution.(2)The bearing capacity of single pile under the condition that the undrained strength c_u of soil obeys lognormal distribution,beta distribution and gamma distribution respectively is analyzed.The results show that the bearing capacity calculated by lognormal distribution random field is the largest,and the bearing capacity obtained by beta distribution is the smallest.(3)Considering the varying law of the undrained strength of soil along the depth,the influence of the non-stationary of random field on the bearing capacity of single pile is studied.The results show that the vertical bearing capacity of single pile increases first and then decreases with the increasing of the non-stationary of random field,but the numerical range of bearing capacity is limited;while the horizontal bearing pile is significantly affected by this property,and the horizontal bearing capacity of single pile varies with the non-stationary of random field The stability increases and decreases.