Large-scale model test studies on a double-layer rubber dam

A new rubber dam with two layers of dam bodies anchored together into a rigid concrete base was proposed to improve the water-retaining capacity of a traditional rubber dam. A series of large-scale model tests was conducted to evaluate the static behaviour of a double-layer rubber dam under conditions of different internal and external water heads, anchoring distances and cross-sectional perimeters. It was found that the maximum tensile force of the Layer-1 dam is located at the anchoring point but that of the Layer-2 dam is located at the extruded free section. The optimal cross-sectional perimeter ratio was concluded as 0.8 with an optimal anchoring distance of 0.06 L₁ and an internal water head in the upstream dam and in the downstream dam of 0.40 L₁ and 0.36 L₁, respectively, where L₁ is the cross-sectional perimeter of the upstream dam.