Study On The Seismic Response Law Of Subway Station Under The Condition Of Weak Interlayer Site

With the rapid development of China’s economy and the expansion of urban scale,urban underground construction has gradually risen.Past experience and lessons have proven that underground structures may be severely damaged under strong earthquakes,and site characteristics are closely related to it.Studies have shown that structures are more prone to failure in some more complex environments with non-uniform and soft soil interlayer,and some studies have shown that sites with less stiffness can absorb more energy and reduce the site’s seismic response.Sites containing soft soils are widely distributed in China,but there are relatively few studies on the seismic response of soft soil interlayer to underground structures.Therefore,it is of great significance to study such problems in practical engineering.In this paper,for the special foundation medium of weak interlayers,the shaking table model test of the double-layer three-span subway station with sand layer was first carried out,and the ground motion response of the structure and site was analyzed with the full clay site as the reference.Then,the finite element software ABAQUS was used for 3D modeling to simulate and restore the typical working conditions of the shaking table test.In combination with the comparative analysis of the tests,the seismic response results of the soil-metro station interaction model under the site containing weak interlayers of soil were verified,which proved the applicability and operability of the finite element software model.Finally,the numerical software are used to simulate the response of several weak intercalations such as muddy clay,silty clay,sandy clay and medium-fine sand during earthquakes.And by changing the thickness of the interlayer and the positional relationship with the structure,comparative analysis of the impact of changes in site conditions on the structure.The main conclusions and results are as follows:1.With the increase of the amplitude of the loading conditions in the shaking table test,the natural frequency of the sandy site decreased greatly,the site liquefaction occurred,the soil surface subsided,and the site stiffness decreased.The pore water pressure and earth pressure increase with the input amplitude of acceleration.As the pore pressure and earth pressure under two-way loading are both greater than that under one-way loading,the vertical seismic action cannot be ignored.The response of the vibrational excitation to the pore water pressure is more obvious,indicating that the pore pressure change is also affected by the seismic wave spectrum characteristics.2.According to the experimental and simulation results,the acceleration peak value of the two-way input seismic wave is greater than the one-way input case.Weak interlayers have a damping effect on vertical and horizontal earthquakes.The horizontal influence is greater than the vertical influence,and the weak interlayer has different damping effects under different ground motions.3.The site has a certain filtering effect on seismic waves.In a weak interlayer site,the greater the input acceleration value,the greater the filtering effect on the high frequency band,and the more obvious the amplification effect on the low frequency band.That is,the smaller the stiffness of the soil layer of the site,the greater the filtering effect and the better the shock absorption effect.4.Under different types of weak interlayers,the acceleration peaks and stresses of the model in ground motion are also different.The analysis results of the article show that the stiffness has little effect on the results,while the muddy clay and medium-fine sand with lowcohesion show a stronger influence,indicating that the cohesive force value is the important factor affecting the structure and site seismic response of the weak interlayer.5.When the weak interlayer is located in the structural layer,the weaker soil layer with less stiffness directly contacts the structural side wall,and the structural stress and strain increase significantly.With the increase of layer thickness,plastic damage appears in the lower column.When the structure is located below the structure,the structure’s response to the earthquake weakens,the time for the peak to appear is delayed,and the stress conditions of the structural members change.When the thickness of the soft sandwich is large,the side wall is more stressed than the lower column,which increases the structural stability.