LABORATORY INVESTIGATION ON THE EFFECT OF HORIZONTAL DRAIN LENGTH AND THICKNESS ON STEADY SEEPAGE FLOW THROUGH HOMOGENEOUS EARTH DAM

Homogeneous earth dam is constructed with the optimized use of local materials, to control and store runoffs. One of the most important destructive factors, in this structure, is the seepage through dam body and below its foundation. There are some methods to prevent the internal erosion, among which the horizontal toe drain is the most common alternative. In this research, the effect of applying various thicknesses of horizontal drain in laboratory model and within the proposed range of lengths derived from the analytical relationships was investigated. Results showed that the increase in thickness and length led to significant increase in downstream slope cover while the effect of thickness has not been considered in similar analytical relationships. In addition, the seepage rate would increase dramatically with the increase in drain thickness but the rate of this increase would decline if the thickness exceeded the proposed maximum limit of this research.