Constitutive Model And Numerical Analysis Of Expansive Soil In Foundation Of Jian-shan-ying Bridge On Guiyang-Guangzhou High Speed Railway

Guiyang-Guangzhou high-speed railway passes through Changming Town,Guiding County,Guizhou Province,where Jianshan Ying Bridge is set up.The field monitoring data show that the piers of the bridge rise in rainy season and subside in dry season.The displacement change of piers(abutments)seriously exceeds the design specifications of high-speed railway,which has a negative impact on the safety of beam-rail structure,and also makes it necessary to limit the speed of high-speed railway passing through Jianshan Ying Bridge.Theoretical analysis and expansibility test show that the main cause of abnormal rise and fall of bridge position is swelling and shrinkage of expansive rock and soil layer under pier.The proposed Guiyang-Nanning High-speed Railway will pass through the vicinity of this area,in order to provide the basis for the investigation,design,construction and later operation of Guiyang-Nanning High-speed Railway,and because most of the studies on constitutive models of expansive rock and soil do not consider or pertinently study the influence of water content on the mechanics and expansive parameters of expansive rock and soil,the selection of constitutive models in numerical simulation of expansive rock and soil is also included.Most of them still use Mohr-Coulomb model or thermo-mechanical coupling model,which can not directly and accurately reflect the mechanical and displacement changes of expansive rock and soil after water absorption.Therefore,it is necessary to customize the constitutive model according to the mechanical properties of expansive rock and soil and the relationship between mechanical expansion parameters and water content in this area.The numerical simulation results based on this model are more accurate and intuitive,and can meet the needs of practical engineering.Under this background,based on the theory of humidity stress field,combined with the mechanical and expansive parameters such as modulus of elasticity,Poisson’s ratio,cohesion and internal friction angle obtained from free expansion rate test,direct shear test,modulus of resilience test and no-load expansion rate test,the elastoplastic properties of expansive soil in Jianshan Ying area are derived based on Mohr-Coulomb criterion.Sexual Constitutive Model.Then the second development of FLAC3 D custom constitutive model is realized in Visual Studio 2005 software.The stress and displacement fields of overburden rock and soil under pier and pile foundation under pile end load and swelling rock and soil after water absorption are obtained by numerical simulation.The correctness of the constitutive model and the factors causing the abnormal rise and fall of piers are verified by numerical simulation and monitoring results of abnormal rise and fall of piers.