Study On The Calculation Of Bearing Capacity Of Composite Foundation With Cement-soil Mixing Piles

Currently,the calculation and design of bearing capacity of composite foundation with cement-soil mixing piles mainly depend on the engineering experiences on the stage of engineering design,meanwhile,the calculation formulas of bearing capacity of composite foundation are imperfection because of the complexity of strengthening techniques of composite foundation and many factors that influence the bearing performance of composite foundation,so the further investigation and research are needed.The strengthening mechanism,bearing mechanism and several general failure modes of composite foundation with cement-soil mixing piles are firstly analyzed in this paper,and several main factors such as the thickness of mattress layer,the displacement rate of area,the length of pile and the length of pile that influence the bearing performance of composite foundation with cement-soil mixing piles are analyzed. Two methods that can identify the bearing capacity of composite foundation with cement-soil mixing piles are introduced:static loading test method and formula method.After analyzing the experimental data of various static loading tests about single pile and composite foundation in the real engineering,it can be found that the actual values of single pile’s bearing capacity are lower than the eigenvalues of single’s bearing capacity obtained by theoretical calculation,meanwhile,the actual bearing capacity of soil between piles is higher than the bearing capacity obtained by obtained by theoretical calculation,so the reduction coefficient λ of single pile’s bearing capacity and the amended reduction coefficient βS of bearing capacity of soil between piles are proposed,and the reasonable regulation about the value range of the correction coefficient λ and βS are made to get the correction calculation formula of the bearing capacity of composite foundation with cement-soil mixing piles finally. Through several engineering reckoning example,it can be obtained that the correction formulas are much accurate than the general formulas after the comparative analysis of error.The ground treatment engineering of cement-soil mixing piles of 1# warehouse area in the first phase of logistics center in a certain city located in the Yangtse River Delta is taken for example,the bearing capacities of composite foundation are calculated by the general calculation formula and the correction calculation formula respectively,and ANSYS finite element software is used to simulate and compute the bearing capacity value of the composite foundation with cement-soil mixing piles in the actual loading process,and this value is as the standard capacity to calculate errors between the value calculated by general calculation formula,the value calculated by correction formula and this standard value respectively to check the accuracy and rationality of correction formulas further.