Analysis Of Influence Of Termite Nest On Seepage And Stability Of Earth-rock Dam

Earth-rock dam has been widely used in water conservancy project construction because of its advantages such as low construction cost,simple structure and easy construction."The dike of a thousand miles is destroyed by the termite nest".The influence of termite nest on the stability of earth-rock dams has always been a key research problem in dam engineering.In the earth-rock dam,termites build nests and reproduce by eroding the soil,and form a nest system with the main nest,the secondary nest and the termite passage as the main parts.When the water level keeps rising,the water flows into the termite passage and termite nest hidden inside the earth-rock dam to form seepage,which reduces the material strength of the earth-rock dam and easily causes engineering accidents such as scattered flooding,pipe gushing and nest falling,which seriously affects the stability of the earth-rock dam.Therefore,it is of theoretical and practical significance to study the influence of termite nest on seepage and stability of earth-rock dam.In this paper,finite element software is used to simulate the evolution of seepage field of earth-rock dam in the presence of termite nest and termite passage.Then,based on the coupling theory of seepage and stress,the influence of the nest size,depth(the distance between the center of the nest and the top of the dam),slope distance(the distance between the center of the nest and the downstream slope)and the auxiliary nest on the overall stability of the earth-rock dam was analyzed by strength reduction method.Finally,the rationality of the simulation results is verified by the calculation and analysis of Baiguishan Reservoir,which provides theoretical reference and practical guidance for the reinforcement of earth-rock dam.The main research contents and conclusions of this paper are as follows:(1)Finite element software was used to simulate the seepage pore pressure and velocity around the termite nest in the saturated and unsaturated regions,and the influence of different ant passages(siphon,straight-through and series)on the seepage pore pressure and velocity around the termite nest was analyzed.The results show that the influence of the termite nest on the percolation pore pressure around the nest is small,and the percolation pore pressure around the nest changes obviously when there are siphon,straight and series passageways around the termite nest.When there are siphon passageways,straight passageways and serial passageways around the termite nest,the serial passageways have the greatest influence on the surrounding seepage velocity.(2)Based on the theory of seepage-stress coupling and strength reduction method,the influence of termite nest size,depth,slope distance and secondary nest on the stability of the downstream slope of earth-rock dam was analyzed by finite element software.The results show that the stability safety factor of earth-rock dam decreases with the increase of nest radius,depth and slope distance.The change rate of safety factor increases with the increase of radius,but decreases with the increase of depth and slope distance.When there are secondary nests around the main nest,the secondary nest on the left side of the main nest has the greatest effect on the safety factor.(3)Taking Baiguishan reservoir project as the research object,the finite element software is used to simulate the influence of termite nest on the seepage and stability of Baiguishan reservoir,and the correctness of the simulation results is verified by combining the monitoring data of the earth-rock dam of Baiguishan reservoir.The results show that the influence of termite nest on the seepage and stability of the earth-rock dam of Baiguishan reservoir is consistent with the monitoring data,which verifies the correctness of the simulation results.