Research On Subgrade Settlement Control And Srtucture Optimization In The Regin Of Red-bed Soft Rock Mass

With the continuous improvement of industrialization and urbanization,the demand for passenger and freight transportation is increasing,a large number of high-speed railway and other infrastructure has been build in China.However,in Southeast China,the annual rainfall is large,and red-bed soft rock mass is widely distributed.Most of the projects are faced with the problems of insufficient foundation bearing capacity and excessive settlement and deformation.How to better deal with the soft soil foundation is of great significance to the development of high-speed railway and other infrastructure.In this paper,the corresponding dimensional equation is obtained by dimensional analysis method.The model test is designed based on this method.By analyzing the test data,the influence of different construction parameters of dynamic compaction method and CFG pile composite foundation on the reinforcement effect is obtained.Then,the response surface model of two kinds of foundation reinforcement methods is built and the parameters are optimized by response surface software based on the results of test and finite element simulation.The main conclusions are as follows:(1)The grain size distribution,dry density,compression modulus and shear strength of soil samples were measured.The results show that with the increase of soil compaction,the compression index and shear index of soil are significantly improved.(2)According to the similarity principle,the similar proportion coefficient of each physical quantity in the model test is calculated by dimension analysis method,and the dynamic compaction model test and the CFG pile composite foundation model test are designed.In the dynamic compaction model test,the influence of dynamic compaction energy level,falling distance and other factors on the foundation reinforcement effect was analyzed.Among them,the ramming energy level has the greatest impact on the ram depth,the displacement of the soil below the ramming point,and the compactness of the soil sample.The propagation law of dynamic stress of each soil layer under the dynamic compaction and the influence law of each factor on the dynamic earth pressure are studied.In the model test of CFG pile composite foundation,the influence of cushion thickness and other factors on the effect of foundation reinforcement is analyzed.The results show that the pile length has the greatest impact on the settlement of composite foundation when it reaches the bearing layer.(3)The response surface models of dynamic compaction and CFG pile composite foundation are built respectively by design expert software.The influence of each factor on the system response and the interaction between the factors are analyzed.The dynamic compaction construction technology and the structural parameters of CFG composite foundation are optimized by combining with economic factors,which can provide some references for similar projects.