Flowthrough and overtopped rockfill dams.

Abstract

The emphasis of this thesis is on the derivation of original results or improvement to the available results in order to obtain a practical design methodology for overtopped rockfill dams. The work comprised of experiments in a large hydraulic flume, and extensive theoretical development of design aspects. A non-linear finite element analysis for non-Darcy flow in dams has also been formulated. The important contributions of the thesis are listed as follows: I. Non-Darcy seepage flow. (1) Development of a general relationship between the Reynolds number and the friction coefficient for seepage in rockfill; (2) Development of a general relationship between the hydraulic gradient and the velocity of seepage flow in rockfill; (3) Investigation of the difference between all the available formulae for non-Darcy flow by the computer simulation with wide range of porosity and size of rockfill. Comparisons between the simulated results of available formulae and the available prototype data have also been undertaken. (4) Determination of the hydraulics mean radius of rockfill material by empirical relationship; (5) Estimation of the seepage discharge through a rockfill dam without numerical modelling. II. Numerical modelling of non-Darcy seepage flow. (1) Development of a high-accuracy finite element method to model the non-Darcy seepage field within a flowthrough and overtopped rockfill dam. III. Stability analysis and design methodology for flowthrough and overtopped rockfill dams. (1) Development of a formula for the design of the external layer comprising of large-size particles at the downstream slope of a flowthrough and overtopped flow rockfill dam; (2) Development of a formula for the design of mesh protection at the downstream slope of a flowthrough and overtopped rockfill dam; (3) Development of a formula for the design of steel bars protected at the downstream slope of a flowthrough and overtopped rockfill dam; (4) Development of a practical design methodology which applies to small flowthrough and overtopped rockfill dams. IV. Behaviour of forces acting on the downstream slope. (1) Investigation of the stochastic and statistical behaviour of the forces acting on the force panels installed at the downstream slope in a model flowthrough and overtopped rockfill dam. V. Theoretical solution of 1-D seepage flow in overtopped rockfill. (1) Development of a theoretical solution for the seepage flow at the transition zone in an overtopped rockfill dam.