Research On Foundation Treatment Of Dredger Fill In Coastal Areas Of TangCao Railway

There are several problems which commonly meet to the mass traffic construction such us the large settlement of foundation,insufficient bearing capacity,residual pore water and sand liquefaction etc.The bidirectional cement mixing pile has been frequently applied in treatment of soft soil foundation for its advantages in fully utilizing foundation raw soil and preventing mud from rising.Besides,small perturbance,low pollution,less cost,various reinforcement forms and small additional subsidence to the underlying stratum have also been considered choosing bidirectional cement mixing pile-net composite foundation in TCSG-3 section of Tangshan-Caofeidian newly-built railway as research object,the paper combing theory analysis,field investigation and detection as well as numerical simulation aims to research the load-bearing deformation characteristics of cement mixing pile-net composite foundation in the course of roadbed filling process.Main works are as follows:(1)Summarizing the mechanism of effects of piles and cushion in composite foundation,failure modes and formula of bearing capacity and sedimentation.Providing theoretical basis for subsequent resrarch on the load-bearing deformation characteristics of cement mixing pile-net composite foundation.(2)During the field investigation,the distinguishing features and status of work in dredger fill,s forming process include high water content and void ratio,poor permeability,high compressibility,low natural gravity and shear strength as well as long consolidation time etc.The conventional treatment methods of dredger fill foundation are divided into replacement,drainage consolidation and physical and chemical strengthening methods like vibration compaction.The paper is going to summarize the construction technology of bidirectional cement mixing pile in the treatment of dredger fill foundation of Tangshan-Caofeidian new railway.(3)Based on the test section of cement mixing pile in Tangshan-Caofeidian newly-built railway,the paper which monitors the surface settlement of composite foundation,lateral displacement of slope foot,pile-soil pressure and pore water pressure in situ induces test data and analyzes the characteristics of deformation and weight bearing of pile-net composite foundation.(4)By using finite element software PLAXIS,the paper will comparatively analyze the change of foundation settlement,side dispalcement of slope foot,force of pile and soil and force of grid on different foundation,reinforced soil foundation,cement mixing pile composite foundation and cement mixing pile-net composite foundation when filling roadbed layer by layer.It will also analyzes the effect of pile-reinforcement-soil interaction on controlling settlement and deformation of composite foundation.(5)The paper uses the finite element software PLAXIS to simulate the effects of cushion elastic modulus,pile elastic modulus,pile spacing,pile length,elastic modulus of underlying layer,soil elastic modulus between piles and elastic modulus of subgrade filling on the mechanical properties and deformation characteristics of pile-net composite foundation.The paper researches the bearing and deformation characteristics of bidirectional cement mixing pile applied in soft foundation of dredger fill in Tangshan-Caofeidian railway,which provides a reference in the practical engineering construction.