Centrifugal Shaking Table Model Tests Of Earth-Rock Dam And Its Saturated Sand Ground

Earth-rock dam is one of the most widely used dam types at home and abroad due to its advantages of being able to obtain local materials during construction and low cost.Among them small reservoirs play an important role in ensuring rural economic development,social stability and food security.According to statistics,about 90%of China’s small reservoirs were built in the 1950s-1970s,and nearly 95%of them used earth-rock dams.These small earth-rock dams generally have some problems,such as low construction standards,difficult to evaluate the engineering quality and so on.At the same time,China is located between the Pacific seismic belt and the Eurasian seismic belt,with an average of one major earthquake every ten years.Earth-rock dams were often damaged in the past earthquakes,which seriously threatened the safety of people’s lives and property.Therefore,earthquake resistance of earth rockfill dams is one of the key problems in the long-term service of earth-rock dams.In this paper,centrifugal shaking table was used to study the seismic response and seismic reinforcement of earth-rock dam.The damage mechanism of earth-rock dam and the dynamic response law of ground under main and aftershocks were revealed,and the effectiveness of anti-liquefaction measures of dam toe weight and dam shell compaction was verified.The main work and research results are as follows:1.Tests were carried out on small earth-rock dam and saturated sand soil ground under the dam.For untreated earth-rock dam and earth-rock dams strengthened by dam toe weight and dam shell compaction,centrifugal shaking table tests were designed to study the effectiveness of anti liquefaction treatments of dam toe weight and dam shell compaction,and to compare the seismic dynamic response.For the saturated sand ground under the dam,the self weight of the dam was equivalent to the self weight of a steel plate,and the centrifugal shaking table test was designed to study the influence of the overlying load(self weight of the dam)and the main and aftershocks on the dynamic response of the dam ground.2.The results of centrifugal shaking table tests of earth-rock dam showed that due to the increased in pore pressure at the bottom of the dam slope soil under the action of earthquakes,the acceleration amplification factor of the untreated dam slope first decreased and then increased along the elevation,while the acceleration amplification factor of the anti-liquefaction treatment dam slope gradually increased along the elevation,and the acceleration at the surface of the dam slope had surface amplification.The dam toe weight and dam shell compaction increased the effective stress of the dam body,reduced the excess pore pressure ratio caused by the earthquakes,and can effectively prevent the liquefaction of the soil.The dam toe liquefaction occurred in the untreated dam slope under the peak acceleration of 0.24 g,while the anti-liquefaction treatment dam slope did not liquefy under the peak acceleration of 0.24 g and 0.45 g.The overall lateral displacement of the untreated dam slope was large,and the anti-liquefaction treatment dam slope showed a vertical settlement under the peak acceleration of 0.24 g earthquake.The horizontal displacement of the dam toe area was significantly reduced and the settlement of the dam crest in the dam shell compaction area was reduced by about 50%compared with the untreated dam slope.The test results verify the seismic effect of the dam toe weight and dam shell compaction,and provide a basis for the seismic reinforcement of small earth-rock dams.3.Comparing the centrifugal shaking table test results of saturated sand groud with or without overlaying load(dam body),it was found that the pore pressure of the lower layer soil in the ground without overlaying load(free site)rised and softened during vibration,the seismic acceleration magnification factor of the soil first decreased and then increased with the elevation,and the acceleration magnification factor of the overlaying load ground gradually decreased with the elevation.During the earthquake,the upper soil with better permeability in the without overlying load ground was liquefied,and the excess pore pressure ratio of the soil first decreased and then increased with the elevation.The overlying load groud liquefied at the edge of the steel plate.With the increase of vibration times,the compactness and stiffness of the soil increased,the peak value of the excess pore pressure ratio decreased,and the anti liquefaction ability of soil improved.Through the centrifugal shaking table model tests,this paper reveals the seismic dynamic response law of small earth-rock dam,verifies the effectiveness of anti liquefaction measures of dam toe weight and dam shell compaction,and obtains the development law of soil pore pressure,acceleration,displacement,stress and strain of small earth-rock dam and saturated sand ground during earthquakes.This study is helpful to improve the understanding of the earthquake damage law of small earth-rock dam,and provides a certain scientific basis for exploring the earthquake resistance of earth-rock dam.