| The northwest region of China is on the edge of the Eurasian seismic belt and has been seriously affected by earthquakes.Gobi soil is widely used in engineering construction in northwest China,but it also has many characteristics,such as complex properties,poor seismic performance,excessive deformation and strong water permeability.According to the application status of polymer in engineering,it can effectively improve the mechanical and seismic properties of gobi soil by mixing it with natural graded gobi soil in a certain proportion.In this paper,by means of experimental research,theoretical analysis and numerical simulation,medium triaxial tests of polymer reinforced gobi soil under single and double vibration conditions are carried out to study the dynamic modulus,damping ratio and residual deformation of polymer reinforced gobi soil.The seismic response analysis of earth-rock dam reinforced with high polymer gelled gobi soil is also carried out.The main conclusions are as follows:（1）Based on the dynamic triaxial test,the dynamic modulus and damping ratio of polymer cementing gobi soil under different polymer mass ratio,confining pressure,consolidation ratio and vibration frequency were obtained.Based on the Shen Zhujiang dynamic model,a modified Shen Zhujiang dynamic model was established considering the polymer mass ratio.The polymer can effectively bond the gobi soil particles together and increase their integrity.When the polymer mass ratio is 3%,the dynamic modulus is significantly increased and the damping ratio is decreased.The elasticity of the gobi soil doped with high polymer is significantly improved,the deformation recovery ability is enhanced,the strain hysteresis phenomenon under cyclic load is reduced,the hysteresis curve symmetry is improved,and the area is reduced.（2）The dynamic residual deformation of the gobi soil can be effectively reduced by the polymer gelled material.The residual shear strain of the gelled gobi soil is 15.0%-18.8%of that of the natural gobi soil and 12.1%-22.2%of that of the natural gobi soil after 30 times of vibration cyclic loading.The larger the mass ratio of the polymer is,the greater the reduction is.According to projection pursuit regression analysis,the order of influence weight of dynamic residual shear strain and residual strain of polymer cementing gobi soil is polymer mass ratio>confining pressure>dynamic stress ratio>consolidation ratio.Based on the shenzhujiang dynamic residual deformation model,the modified residual deformation model of polymer cemented gobi soil was established by using exponential function to fit the relationship between the residual deformation and vibration number.（3）Under the condition of bidirectional vibration,the dynamic triaxial test of polymer cementing gobi soil was carried out.Under the bidirectional vibration,the shaft curve of polymer cemented gobi soil becomes steeper due to the action of radial dynamic stress.The dynamic shear modulus increases first and then decreases with the increase of shear strain,and the shaft curve becomes steeper with the increase of phase difference.The dynamic residual shear strain and residual bulk strain are smaller than those under unidirectional vibration.The errors of dynamic modulus and damping ratio are larger when shenzhujiang model is used,and the results of dynamic residual deformation are better when shenzhujiang residual deformation model is used.Under the condition of unidirectional vibration,the dynamic modulus parameters of high polymer cemented Gobi soil are smaller than those under bidirectional vibration,and the damping ratio has little difference.The parameters c1 and c4 of residual volume strain and residual shear strain under unidirectional vibration are greater than those under bidirectional vibration,and the parameters c2 and c5 have little difference.（4）Through finite element analysis,it is concluded that the reinforcement of polymer cementing material can obviously slow down the seismic amplification effect,reduce the permanent deformation,and improve the ability of earth-rock dam to resist earthquake action.The static and dynamic response analysis of an asphalt concrete core dam without reinforcement and reinforced by polymer cementing material is carried out.The results show that:The maximum acceleration of the earth-rock dam reinforced by polymer cementing material is smaller than that of the dam reinforced by polymer cementing material.The permanent deformation of earth-rock dam reinforced by polymer cementing material can be effectively reduced by 23%. |
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