3D FEM Seepage Analysis On Culvert Under Earth Dam

There is a long history of earth rock dam construction in water conservancy project. Compared with other types of dams, earth rock dam costs less, so it is used commonly. The culvert below dam, which is embedded in the earth rock dam, is a kind of important water conveyance structure. The culvert below dam is directly buried in the dam body. It needs to bear the soil pressure coming from the dam top and suffer the influence of the uneven settlement of foundation. On the dam body and the filling contact position it also needs to bear the seepage erosion. It would cause serious losses to the project if the culvert below dam is damaged. When talking about the planning design and parameter analysis of earth rock dam work, it always focuses on seepage analysis and stability calculation, while the study of the culvert lays emphasis on culvert stress, settlement calculation and other structural calculation analysis. But in the stability seepage period of the dam, research on culvert and the dam earth contact seepage is rarely carried out.In order to study the contact seepage under the dam around the culvert, this paper firstly introduces the basic method and development of seepage theory, and then establishes the 3D finite element analysis models of a stable seepage period body dam and a buried culvert under the dam. Through the comparisons of common nonlinear problem analysis model of the earth rock dam, the Mohr-Coulomb model is finally used as the constitutive model in the finite element analysis of earth rock dam in this paper. For the different calculation conditions, buried culvert and dam stress calculation model and seepage analysis model are established respectively.According to the study, here come the following conclusions:(1) The vertical earth pressure and settlement around the culvertWhen calculate of buried culvert pipe vertical earth pressure on the top,it should be considered when the culvert soil on both sides of the uneven settlement "drag friction effect caused in stress increases.The distribution of stress around vertical culvert inhomogeneous. Above the culvert, with the increase of the distance from the center line of the top of the culvert, the vertical stress at the top of the culvert increases. Outside the lateral of the culvert, vertical stress decreased first and then increased, gradually stabilized. Because the soil body above the culvert and that on sides of the culvert is uneven subsided, as the distance to the center axis increases, the vertical displacement of the soil around the culvert increases gradually, and then tends to be stable.(2) Culvert surrounding seepage which has no anti-seep diaphragmThe seepage velocity and the seepage discharge in the soil surrounding the culvert increase as the permeability coefficient increases. When not setting the anti-seep diaphragm, even if the permeability coefficient varies, the seepage gradient along hardly change, but only in seepage exit the seepage gradient decreases slightly with the permeability coefficient around the culvert increasing.(3) The effect of anti-seep diaphragm on soil seepage around the culvertCulvert with anti-seep diaphragm can effectively lower the seepage velocity, seepage flow and greatly reduce the infiltration gradient of the seepage exit around the culvert. It plays an important role in avoiding contact erosion to the soil around the culvert. Water resistance effect of the anti-seep diaphragm is also concerned with the size and quantity. With a certain range, the more and larger size of the ring, the better effect it devotes to preventing seepage failure around the culvert. Outside that range, increasing size and quantity, the waterproof effect is limited.