Seismic stability of a concrete gravity dam having a lightweight profile

Abstract

In 1976-1977 the Moscow Land Recl-m~tion Institute carried out model investigations of the seismic stability of a dam having a lightweight profile (Fig. i) developed with respect to the conditions at the Kurpsa hydrostatlon [1]. The height of the dam is 126 m and the ratio of base width to height is 0.514. The design of the dam allows tensile stresses inward from the upstream face and opening of horizontal construction joints even under the design static loads. In this case it is assumed that the bearing capacity of the dam is determined by the strength of the concrete in the compressed zone and loss of bearing capacity occurs as a result of shear along one horizontal section (probably in the plane of the construction joint), which is accompanied by failure of the compressed zone of the downstream face of the dam.The investigations consisted in determining the maximum seismic load leading to loss of bearing capacity of the dam and the form of its failure. It was assumed that the presens wldely used linear elastic setup of model investigations with reproduction of only the elastic characteristics of the concrete in conformity with the Cauchy criterion is insufficient. It was necessary to maintain slmilarlty of both the elastic and inertial seismic forces and of the stress state in the dam under the effect of the main static loads --the dam's own weight and the hydrostatic pressure. The problem was complicated further by the fact that in the experiments the model had to be brought to failure, i.e., it was necessary to reproduce similarity of the strength characteristics of concrete and the model material and the shear characteristics of the construction joints in the dam.This problem can be solved with the use of known brittle materials with sufficiently high moduli of elasticity and a relationship of the compressive and tensile strengths close to that for concrete [2] in a fleld of centrifugal forces (on a centrifuge) or in the natural gravitational field. In the latter case the problem of modeling seismic effects and recording the parameters of the model during experiments is greatly simplified, but it is necessary to develop special materials with very low strength characteristics.Taking into account the virtues of the latter method, we decided to investigate the seismic stability of the Kurpsa dam in a natural gravitational field. The experiments were conducted on a model made of special material [3] at a scale of 1:200 with reproduction of seven horlzontal constructlon joints and the Joint along the concrete--rock contact, and also on four monolithic models.The physical and mechanical characteristics of the model material are presented in Table i. The material was made from a plaster binder (P) with fillers in the form of limestone powder (L) and rubber crumbs (R). Lead powder (Pb) was used as the weighting substance. Mineral oil AK-10 (M) was used for neutralizing the binding properties of the lead powder [&] for the purpose of reducing the modulus of elasticity and tensile strength of the model material. Th...

Dynamic Model Rupture Tests of Concrete Dams on Shaking Table

“…Lyatkher et al [8] used gypsum, rubber powder, bentonite and lead powder etc to make Toktogul gravity dam models, and performed the centrifuge experiment to study magnitude of acceleration when the dam occurred failure. Bakhtin and Dumenko [9] used gypsum, water, rubber powder, lead powder, mineral oil to produce a gravity dam profile model, powder of rubber and lead are used to adjust the density. Mineral oil is used to fix lead powder, reduce the material elastic modulus and tensile strength.…”