Study On Seismic Dynamic Response Characteristics Of Seasonal Frozen Soil Site

Seasonal frost areas are widely distributed in China,and many earthquakes occur in seasonal frost areas.At present,most researches on site seismic response in seasonally frozen areas are in the stage of qualitative cognition,and most of the conclusions drawn from related studies are that frozen soil layers will weaken the ground motion response of the soil.In fact,there are great regional differences in the dynamic characteristics of frozen soil,and there will be different seismic responses under the action of earthquakes.Therefore,in this paper,the typical silty clay in Changchun area is taken as the research object.The static and dynamic triaxial tests of the silty clay in the frozen state and the unfrozen state are carried out to obtain the static and dynamic parameters of the soil at different temperatures,and Based on this,the numerical simulation analysis of the seismic response of the site in the seasonally frozen area is carried out.The main work and results of this article are as follows:1.Summarize the research status of frozen soil dynamics and seismic response analysis of frozen soil sites at home and abroad in detail.The static and dynamic characteristics of saturated soil and Seed equivalent conversion method are theoretically analyzed.2.The consolidation and undrained triaxial compression test of typical silty clay in Changchun area at different temperatures was conducted.The test results showed that as the temperature decreased,the ice content in the soil increased and the shear strength of the soil was greatly improved.The cohesion of the soil gradually increases when the temperature decreases.At-10 ?,the cohesion of the soil is 47 times that of15 ?.The internal friction angle of the soil gradually decreases with decreasing temperature.3.The dynamic stress of the same stress amplitude,frequency and period is applied to the soil under different temperature and confining pressure conditions,and the dynamic shear modulus and dynamic damping ratio of the soil under different test conditions are obtained.By comparing the test results,it can be seen that when confining pressure remains unchanged,as the temperature decreases,the dynamic shear modulus of the soil gradually increases,and the dynamic damping ratio gradually decreases.When the temperature remains unchanged,the dynamic shear modulus and dynamic damping ratio will increase with the increase of confining pressure,but the increase is not large.4.Using the soil parameters obtained by the test as a basis for numerical simulation analysis of the seismic response of the site in the seasonally frozen area.The comparative analysis of the different response results of the normal temperature site and the site with a frozen soil layer under earthquake action has shown that for typical silty clay sites in Changchun,the presence of the frozen soil layer weakens the seismic response of the site to a certain extent,but there are The site where the frozen soil layer exists is larger than the normal temperature site under the earthquake,the surface will produce greater horizontal and vertical displacements,and it needs to be paid attention to when designing the structure for earthquake resistance.