Abstract: The soil arch effect has important implications for the seismic stability of underground structures,but there have been few studies on the effect of seismic action on the soil arch effect.By repeating the classical Trapdoor test with a modified test apparatus and applying seismic effect to the soil arching model,the development stages and the influence range of the soil arch effect,the soil pressure distribution and the soil displacement under the influence of the soil arch effect,the change of the soil arch effect under the seismic effect are studied,the mechanism of the seismic effect on the soil arch effect is analyzed,the effect of the change of the soil arch effect on the seismic stability of underground structures is discussed.The results show that the development process of soil arch effect can be divided into initial stage,transition stage and stabilization stage.The influence range of the soil arch effect is symmetrically distributed along the Trapdoor center with a width of 2B(B is the width of Trapdoor).The soil pressure distribution within the influence range of the soil arch effect is non-uniform.The soil pressure on the Trapdoor gradually increases from the edge to the center,and the soil pressure on the fixed area gradually decreases from the edge to the center.The soil under the influence of the soil arch effect can be divided into collapse zone,soil arch zone and stability zone.The destruction of the soil arch zone leads to a recession of the soil arch effect under the seismic action.The smaller the buried depth and the larger the Trapdoor displacement,the greater the destruction of the soil arch zone and the more severe the recession of soil arch effect.The critical depth of the soil is 3B and the ideal range for the average height of ground loss is 1.3%B~4.2%B.When the buried depth is greater than the critical depth and the average height of ground loss is within the ideal range,the development of the soil arch effect above the underground structure is the greatest,and the seismic action on the soil arch effect is the least,which is most beneficial to the seismic stability of the underground structure.