Influence Of Soft Soil Interlayer On Seismic Analysis Of Underground Structures

The development of urbanization has gradually shifted the focus of human construction to the underground.Underground structural engineering is in full swing.At the same time,earthquakes in China are frequent,and good seismic performance of underground structures is indispensable.The dynamic response of underground structures in earthquake damage is largely related to the soil conditions of the site.There are relatively few studies on the heterogeneous soil layer at home and abroad.This paper focuses on the study of heterogeneous soil layers-weak soil interlayers.Based on the influence of structural seismic response,the shaking table test of two-story three-span subway station was designed,and the three-dimensional model of the metro station was constructed based on ADINA finite element software.The seismic depth of the soft soil interlayer and the seismic response of the metro station were analyzed.The specific work and conclusions are as follows:(1)This paper introduces the practical significance and value of this topic,and investigates the current research methods and research contents in this field,then provides specific theoretical basis for subsequent research.This paper summarizes the related theories of dynamic finite element,including the basic elements involved in the soil-underground structure system and the model based on the calculation process.It also introduces the establishment process of the dynamic finite element equation and the method of solving,howto pass the modal.The analysis determines the Rayleigh damping of the model.Various artificial boundaries are introduced(2)Large-scale shaking table test for uneven soil layer--with soft soil interlayer is conducted.In the test,saturated sand was used to simulate soft soil,and a two-story,three-span subway station model was established.The whole test contained two different conditions—the conditions of the whole clay site and the site conditions containing the soft soil interlayer.By comparing the seismic response of metro stations under two working conditions,the following conclusions are obtained: the acceleration peak of the underground structure in the whole clay site is larger than the acceleration peak in the soft sand sandwich site,and the sand interlayer may reduce the effect of the earthquake.The two site conditions have a filtering effect on the seismic wave,but the roles of the two are not the same.The site with weak soil has a lower amplification frequency,and the weak soil may absorb high-frequency waves.The strain of the structure in the whole clay field is larger than the site containing soft soil as well.(3)Using the finite element software ADINA to establish a soil-based three-dimensional model of the subway station to simulate the entire test.The test and simulation results are reliable.By changing the conditions of the site,the seismic response of the underground structure under different working conditions is obtained.The comparison shows that the seismic response of the soft soil interlayer to the underground structure will be weakened,which is consistent with the experimental conclusion.This weakening effect increases with the increase of the thickness of the interlayer soil,and also has a certain relationship with the position of the interlayer soil.