Research on New Dam Structure for High Earth Core Rockfill Dam on Thick Overburden

Abstract

For high earth core rockfill dam constructed on thick overburden, traditional anti-seepage system design and construction is to construct the foundation seepage cut-off wall first, and then build a rigid or soft-connected grouting gallery on top of seepage cut-off wall, and then cover the gallery with high plastic clay. Therefore, after the construction, the high dam body transmits great pressure to the seepage cut-off wall through the gallery. For this reason, a new type of structure for high earth core rockfill dam constructed on thick overburden is proposed, namely constructing a “concrete slab” with a large dimension gallery on the overburden, so that the seepage cut-off wall can be constructed from the inside of the large dimension gallery during or after construction of the dam body to reduce the stresses in the cut-off wall. The cut-off wall and the concrete slab on the overburden, together with the upper dam body, form a complete anti-seepage system, but it has not been used in actual dam construction. In this paper, two-dimensional finite element stress and deformation analyses were carried out to assess the effects of the proposed concrete slab and cut-off wall construction sequence on a 223-meter high earth core rockfill dam constructed on thick overburden. The stresses and deformations of the concrete slab are obtained, and its structural safety and suitability for use in earth core rockfill dam are also evaluated. According to research results, by rationally adjusting the construction order of the dam body and the cut-off wall, the compressive stresses on the cut-off wall can be controlled, which has been a big problem for traditional structures. It reflects the advantage of the new structure.