Three-dimensional seepage in the cores of rock-and-earth-fill dams

Abstract

1. Consideration of the three-dimensional character of seepage flow in the region of shore abutments in rock-and-earth-fill dams exerts a major influence on the basic seepage parameters required for the design of the core profile, the gradation of soils in reciprocal filters of transitional layers, etc. 2. The three-dimensional character of the flow exerts the most significant influence on the value of Jdis, especially along the line of contact between the lower face of the core and the shore slope Jdis.S. In that case, the steeper the slope, the greater amount the values of the discharge gradients are lowered. 3. With three-dimensional seepage, increased Jdis values arise in the core primarily along the water line of the lower pool and the line of contact between the lower face and horizontal underflooded sections; it is precisely in this connection that special protection should be specified. 4. In evaluating the seepage resistance of the core soil for contact overflow, it is recommended to use the component of the gradient Jdis normal to the plane of the downstream face Jn.n as the computed discharge pressure gradient. 5. Computational relationships for determination of parameters of three-dimensional seepage, which are required for engineering calculations of the cores of rock-and-earth-fill dams are proposed in the paper. Computational methods based on plane seepage yield significant errors in a number of cases, and should therefore be used with certain caution, even in preliminary stages of design.