DESIGN OF EARTH DAMS ALLOWING TEMPORARY OVERTOPPING BASED ON HYDRAULIC FAILURE EXPERIMENTS AND FLOOD ANALYSIS

摘要

Every year a great number of small earth dams for agricultural irrigation are seriously damaged or totally fail because of flood overflow exceeding the drainage capacity of a spillway. To stabilize downstream slopes of earth fill dams against overflow, a new stabilization technology using geosynthetic soil bags with extended tails (GSET)was developed. GSET functions as a spillway for temporary flooding while it is designed to have a high seismic stability. A series of hydraulic failure experiments were performed on a 3.5 m-high and 2.3 m-wide full-scale GSET model with a downstream slope of 1:1.2 (V: H). The overflow was stepwise increased. Based on the test results, a flood stability design for GSET spillways allowing temporary overflow is developed. A design working example is presented based on an actual flood record. It is shown that the remedy work of an existing earth dam by means of a GSET-spillway is effective in particular with small earth dams with short-peak flooding.