Research On Seismic Mitigation Effect Of Gravity Retaining Wall Inverted Filter Under Earthquake

As an important part of the retaining structure,the inverted filter plays an important role in eliminating the water accumulated in the back of the wall to maintain the stability of the retaining wall and to prevent the soil from escaping.However,the design of the existing inverted filter is still lack of systemic and pertinent.Under earthquake conditions,how to use the shock absorption and energy dissipation function of the inverted filter remains to be developed.And in the high-intensity seismic zone,it is also necessary to consider the influence of seismic action on the retaining structure.If the shock absorption function of the inverted filter can be given,the safety and long-term service performance of the retaining structure can be effectively ensured.Therefore,research on the inverted filter with both filtration,drainage and shock absorption and energy dissipation functions has practical engineering significance.The vibration table test and ABAQUS finite element calculation are used as research methods to study the energy dissipation and damping effect of gravity retaining wall filter cushion.Three sets of vibration table tests with pure gravity type,padding thickness of 4cm and 2cm elastic modulus of 0.1MPa anti-filter mat were carried out.The energy dissipation and shock absorption effect of the filter mat is analyzed from the maximum response of the earth pressure under the action of the earthquake and the maximum response of the earth pressure when the wall and the soil move toward the free surface and the displacement of the soil is larger than the wall.The finite element work is a sensitivity analysis of the energy dissipation and shock absorption effects of the two parameters of the thickness and elastic modulus of the inverted filter.The main achievements are as follows:(1)Due to the energy consumption of the inverted filter,the acceleration and displacement response are greater than the pure gravity mode.The acceleration of the fill has an amplification effect with respect to the vibration of the table top,and it increases with the increase of the height from the bottom of the wall,and decreases with the increase of the seismic peak ground acceleration(PGA).The dynamic displacement response of the fill shows that the farther away from the wall back,the smaller the response value,and increases as the PGA increases.(2)Under the action of the inverted filter,the static earth pressure distribution is more uniform,and the static earth pressure distribution is more uniform,showing a significant "parabolic" nonlinear distribution law.However,the filter mat has no load shedding effect on the static earth pressure.(3)The vibration table test shows that the inverted filter has a significant load shedding effect on the dynamic earth pressure,which also plays a role in reducing the seismic earth pressure.The de-loading rate of the dynamic earth pressure and the de-loading rate of the seismic earth pressure all show an increase with the increase of PGA and the effect of the 5 cm thickness filter mat is better than the 2 cm filter mat.When PGA = 0.4g(large earthquake),the effect of the inverted filter is remarkable.Under the condition of adding 4cm and 2cm inverted filter,the de-loading rate of dynamic earth pressure is 50%~70% and 45%~65%,respectively.The decommissioning rate of seismic earth pressure is 38%~43% and 31%~41%.Considering the unfavorable working conditions of wall soil displacement: under the condition of adding 4cm and 2cm inverted filter,the dynamic soil de-loading rate is 45%~65%,25%~35%,and the seismic earth pressure de-loading rate is 18%~40%,11%~23%.The finite element calculation shows that the load shedding rate increases with the increase of the thickness of the inverted filter and the decrease of the elastic modulus.At the same time,the amount of displacement of the fill is increasing,and the shape variable generated by the inverted filter for energy consumption is also increased.Considering the load shedding rate,soil displacement and economy,in actual engineering,it is recommended to use a inverted filter with a thickness of 4cm~20cm and an elastic modulus of 0.1~0.5MPa.