Study On Ground Motion And Rayleigh Wave Propagation Characteristics In Frozen Soil Area

With the promotion of the western development strategy of the country,the infrastructure in the west is constantly improved and a large number of engineering projects are steadily promoted.However,due to the high altitude of the western region,the soil is mostly permafrost,including permafrost and seasonal permafrost.Permafrost is different from unsaturated and saturated soils.The appearance of ice phase in the pores of permafrost changes the constitutive relationship and general mechanical properties of soil,so the wave propagation is obviously different.The use of non-permafrost data in seismic recording,geological exploration and engineering construction will affect the detection results and even the engineering safety in serious cases.Therefore,it is necessary to study the propagation characteristics of waves in the permafrost.This paper will study the seismic response and Rayleigh wave propagation in the frozen soil on the basis of previous studies.Firstly,according to the theory of LCA/LCAM freezing saturated porous media,a simplified model of one-dimensional vertical seismic response of permafrost considering freezing is established,and then the analytical solution of one-dimensional vertical seismic response of permafrost is obtained by using the Laplace transform method and the separation of variables method.The results show that the one-dimensional vertical seismic response solution of permafrost can be reduced to the one-dimensional vertical seismic response solution of saturated soil.Freezing temperature,pore ratio and shear modulus of unfrozen soil have important effects on the vertical seismic response of permafrost.Rayleigh wave is mainly used in exploration engineering,using the properties of Rayleigh wave inversion to get the information of underground medium,this method in the evaluation of soil,the geological exploration has been widely used in such aspects,according to the LCA/LCAM frozen saturated porous media theory,set up to consider freezing effect of permafrost simplified model of Rayleigh wave propagation,using the Helmholtz decomposition and differential operator method of the characteristics of permafrost Rayleigh wave equations are obtained.The results show that freezing temperature and porosity have important effects on Rayleigh wave propagation in permafrost.The results of this study have important theoretical and applied value for earthquake monitoring and engineering construction in permafrost region.In practical engineering,artificial source surface wave method and fretting method are often used for exploration.The results show that the two methods have their own advantages and limitations,among which the artificial source surface wave method is of low depth,but high precision,the fretting method can be adjusted according to the needs of the detection depth,but the shallow information is missing,the detection accuracy will decrease with the increase of the depth.Therefore,which exploration technology should be selected in the actual project should be determined in combination with the specific engineering situation.