Experimental investigation on nonlinear dynamic response of concrete gravity dam-reservoir system

Abstract

The nonlinear response of concrete gravity dam-reservoir system has been investigated by conducting experiments on small scale model of Koyna dam on a horizontal shake table using sinusoidal chirp motions. Two dimensional models of non-overflow section of Koyna dam have been prepared in the laboratory with a scale ratio of 1:150. To satisfy the laws of similitude, an appropriate ratio of cement, sand, bentonite and water has been mixed to find the target properties of model dam. Dam models have been casted over a wooden base plate using a wooden mould. After setting and drying process the wooden mould has been removed and each dam model has been assembled with a reservoir model after placing them over a horizontal shake table. The interaction between dam and reservoir model has been made in such a manner, so that it can transmit the hydro dynamic force of reservoir water to the dam model without allowing any seepage of water across it. Experiments have been performed on the dam-reservoir system with empty and full reservoir water by applying horizontal sinusoidal chirp excitations to the shake table to observe the basic behaviour, crack formation, crack opening, sliding along crack planes and stability after crack formation of the dam model. The numerical analysis of the system has been carried out using ABAQUS 6.10 considering damage plasticity model. The effect of foundation has been neglected assuming a rigid dam foundation as the dam is placed on a rigid plate. The eigen frequencies of the dam model have been calculated and compared with experimental values to calibrate the analysis model. The crack propagation due to tensile damages is computed and the results are compared with the experimental results. The outcome of the response results shows the correctness of the developed experimental model of dam-reservoir system.