Rockfill Structures Subject to Water Flow

Field and laboratory experience in Australia on flow through rockfill dams is summarized. This experience has resulted from the building of Laughlin Jack Dam, an inbuilt spillway structure, and from several other projects in which provision has been made to pass floodwaters over partly-completed structures on an emergency basis. Associated laboratory work has examined the law of head loss in flow through rockfill, and a nomogram is presented for the designer's convenience. The application to particular flow problems is examined and the interesting result of a linear head-discharge law for inbuilt spillway dams is noted. Current methods of stability analysis are shown to be inadequate and an alternative means of assessing structural performance is presented in the form of a stability design chart. A digest of experience on mesh reinforcement for flood overflow is included and a design basis is suggested.