Study On Mechanical Properties Of Rubber-Sand Cemented Materials And Its Interaction With Pile Foundation Under Freeze-Thaw Cycles

Seasonal frozen soil is widely distributed in the north of the Yangtze River in China.With seasonal changes,seasonal frozen soil is bound to undergo freeze-thaw cycles,which affects the characteristics of pile-soil interaction.After soil freezing in winter,the strength of soil around the pile will be significantly improved,and the lateral deformation performance of the pile foundation will be reduced.It is easy to cause brittle failure such as broken pile under horizontal loads such as earthquakes.In order to eliminate or reduce the adverse effects of freeze-thaw cycles on the bearing capacity of pile foundation in seasonal frozen soil area,the waste tire rubber particle materials with seismic resistance,thermal insulation and low-temperatures stability is proposed to replace the soil around the pile within a certain freezing depth,and the interaction mechanism between it and the pile foundation are analyzed.In this paper,rubber particles,quartz sand and polyurethane glue were first used to prepare rubber-sand cementing material samples according to a certain mass ratio.Then the physical and mechanical properties and microstructure were tested by indoor geotechnical test and scanning electron microscope.Then,the influence of rubber-sand cementing material replacement on the stress and deformation of pile foundation is analyzed by numerical simulation.Finally,the p-y curve model of pile foundation after rubber-sand cemented material replacement is established by analyzing the influencing factors,and the corresponding parameter value method is given.The main work of this paper is as follows:(1)Unconsolidated undrained triaxial compression tests were carried out to obtain the stress-strain curves of rubber-sand cemented materials under different conditions.The stress-strain constitutive relation of rubber-sand cemented material was obtained by nonlinear fitting and regression analysis,and the fitting relationship between tangent Poisson’ s ratio and axial and radial strains was established.The results show that the stress-strain curve of rubber-sand cementing material specimen has no peak point,which is a typical strain hardening material.Temperature has a great influence on the failure strength and elastic modulus of the specimen,while freeze-thaw cycles and low confining pressures have little influence on the failure strength and elastic modulus of the specimen.Scanning electron microscope shows that the main stress skeleton of rubber-sand cementing material is rubber particles.(2)The finite element model of pile foundation in seasonal frozen soil area was established by ABAQUS.Before replacement,the strength and stiffness of shallow soil increased significantly after soil freezing in winter.Under horizontal load,the plastic hinge region decreased,and the bending moment profile became narrow,resulting in the weakening of plastic deformation capacity of pile foundation,and the maximum bending moment of pile body was close to the ground(about 0.15m).After replacement,under horizontal load,the plastic hinge area expands,and the maximum bending moment is about 1.1m away from the ground.The lateral displacement capacity is much larger than that of frozen soil pile foundation.(3)By analyzing the p-y curve of pile foundation after replacement,it is found that the relationship between soil resistance and displacement is basically linear,which is related to the fact that rubber-sand cementing materials is approximately elastic material.Therefore,the ideal elastic-plastic model is modified to obtain the p-y curve model suitable for rubber-sand cementing materials.Finally,the p-y curve of pile foundation obtained by numerical simulation was compared with the p-y curve of pile foundation proposed in this paper,and the rationality of the p-y curve of rubber-sand cemented materials pile foundation was verified.