Study On Deformation And Bearing Characteristics Of Cement Mixing Pile Composite Foundation Under Flexible Load

With the rapid development of highways in coastal soft soil areas in China,cement mixing pile as a soft soil foundation reinforcement technology has been widely used.Cement mixing pile has the advantages of fast construction speed and low cost,which can effectively improve the bearing capacity of composite foundation,reduce the settlement of foundation and accelerate the consolidation of foundation soil.At present,there are many researches on the settlement,consolidation and bearing capacity of cement mixing pile composite foundation under rigid load,while there are few researches on the related problems of cement mixing pile composite foundation under flexible load,among which there are still some problems that need to be solved.Based on the gaoming-enping expressway,based on the field test and long-term monitoring data,and combined with theoretical analysis,this paper discusses the calculation of the settlement,consolidation and bearing capacity of the composite foundation of cement mixing pile under the action of flexible load,and puts forward an improved calculation method.The main research results of this paper are as follows:(1)Aiming at the difference between flexible load and rigid load,the form of pile-soil interaction under flexible load is analyzed,and the formula for calculating the total settlement of cement mixed pile composite foundation under flexible load considering pilesoil interaction is deduced.The calculation method of the total settlement of the composite foundation of the cement mixing pile under the action was verified by an engineering example.(2)Simplify the soil around the pile and the cement mixing pile into an isotropic elastic body.Under the condition that only vertical deformation is considered,the equal strain assumption is used to derive the consolidation control equation of the composite foundation of the cement mixing pile under flexible load With reference to the one-dimensional consolidation theory of double-layer foundation under variable loads,the analytical solution of the consolidation control equation is obtained and verified by engineering examples.(3)The influence of cement mixing pile construction on the bearing capacity of soil around the pile is studied,and the value of the bearing capacity correction coefficient of soil around the pile is determined through an engineering example,and the necessity of calculating the bearing capacity of composite foundation of cement mixing pile is verified.(4)The influence of cement content and curing age on unconfined compressive strength of soil-cement was analyzed through the mixing ratio test in the soil-cement chamber,and the optimal cement content of cement mixing pile was determined to be 18% through the unconfined compressive strength test of cement mixing pile in the field.(5)Deformation(including total settlement,layered settlement,deep horizontal displacement)and stress(including pile-soil stress ratio,load sharing ratio,vertical stress of cement mixing pile,super static pore water pressure)of composite foundation of cement mixing pile under flexible load)After long-term monitoring and analysis,the deformation and stress of the composite foundation of the cement mixing pile during the filling process were obtained.(6)The effect of pile spacing,pile body elastic modulus and pile body Poisson's ratio on the composite foundation of cement-mixed piles is studied using numerical simulation.The results show that pile spacing and pile body elastic modulus affect the composite foundation of cement-mixed piles Force and deformation have a greater impact,while the Poisson's ratio of the pile is smaller.The amount of deformation of the composite foundation of the cement mixing pile under different flexible loads obtained by numerical simulation is compared with the results obtained by the total settlement calculation method deduced in this paper.The deviation between the two is within 6.5%,thereby further verifying the settlement proposed in this paper The calculation method is suitable for the calculation of the settlement of the composite foundation of cement mixing piles under the action of flexible loads.