Effect of Headwater to the Change in Base Length of the Non-Overflow Concrete Gravity Dam Design

Abstract

In order to determine the base length of the non-overflow gravity dam using single step design, several heights such as headwater, sediment depth, height of dam and other dimensions related to the shape of dam have to be specified first by the designer. The base length is then determined by assign the base length as the function of forces such as forces due to hydrostatic pressure, uplift pressure, silt deposition near the heel of dam, weight of dam and foundation, and earthquake. The most important height, which is related to most of the forces, is the headwater. Therefore, this study aims to determine the effect of the headwater to the change in base length. This is done under the condition that the resultant forces have to fall in the middle third of base length and the designed dam is safe against sliding and overturning.   The results found that the safe base length has relation with the headwater in quadratic equation form. Moreover, if the ratio between the base length and the headwater is less than one, the designed dam is safe against sliding and overturning without the need to extend base length.