Aseismic Stability Analysis Of Earth-rock Dam And Safety Research Of The Post-earthquake Dam Slope

Earth-rock dam is most widely used in water conservancy engineering. Most of the earth-rock dams which have been built and are to build in China are located in the seismic risk region. Although the earth-rock dam has good seismic capacity, there is a variety of destruction form under strong shock. This article evaluated seismic performance of the earth-rock dam using the finite element method(FEM) from the following there aspects: the seismic performance was analyzed with the finite element dynamic time history analysis method; the degree of damage caused by earthquakes was determined according to the size of permanent deformation and the running stability of the earth-rock dam after earthquakes based on permanent deformation; finally the dam foundation liquefaction was conducted and the liquefied range was evaluated.(1) The finite element dynamic time history analysis method can effectively simulate the dynamic stability coefficient and analyze the possibility of instant instability failure of the earth-rock dam during the earthquake. This article studied the influence of two special load combinations on the dam when earthquakes attacked the empty and the reservoir containing normal water respectively. The result shows: the dynamic stability coefficient changed significantly under the effect of earthquakes; different initial stress conditions had great impact on both the dynamic stability coefficient and the maximum difference of changes of the coefficient.(2) The adopted dam and dam foundation finite element-infinite element coupling model eliminated the error caused by reflection of the seismic wave on the general finite element boundaries. The dam was stimulated and the seismic permanent deformation was calculated using the equivalent viscoelastic dynamic model and the plastic accumulative strain model based on tests. For the dam that did not instantaneously collapsed under the effect of earthquakes, slope stability after the quake was analyzed on normal operating conditions. That is a new method to evaluate the stability of the earth-rock dam after earthquakes, avoiding limitations of evaluation based on the engineering experience of the researchers. The results showed that: the upstream and downstream maximum permanent deformation were 8.66 cm and 8.89 cm respectively; the along river direction permanent deformation reduced in turn along both sides of the dam slope to the center line of the dam body; the permanent deformation of downstream was slightly larger than that of upstream. The permanent deformation reduced the dam slope safety factor significantly. And the shallow landslide wad prone to happen operating after earthquakes.(3) This article embedded the pore pressure model which better reflect the expansion process of the powder soil pore pressure in the viscoelastic model. The finite element method was used to study the dynamic properties of saturated dam base. Some measures to prevent foundation liquefaction were proposed. The results showed that: excess pore water pressure occurs mainly in the upper dam, and the liquefaction of dam foundation occurs in shallow depth. Analysis of potential range of liquefaction can reduce the blindness and the cost of engineering reinforcement.