Re-Evaluation of the Stability of Large Concrete Structures on Rock with Emphasis on European Experience

摘要

The sliding stability of a rock mass forming the foundation or the abutments of concrete dams, of a natural slope, or of a cut cannot be measured directly but merely conjectured. One knows, however, conversely, remedial measures which may enhance the existing stability. Attention must be paid to sliding hazard if the presence of adversely oriented discontinuities with considerable persistence is evident, if movements take place in the rock mass, if high water pressures are measured in faults, and/or if wet spots are critical areas of a slope or downstream of the dam foundation are known to occur. A change in the flow rate of the drains can also be an indication of an unsafe condition. The most effective way and in many insstances the only practical solution to increase stability against sliding is to prevent or to eliminate the occurrence to excessive water pressure below the foundation or in faults. The second possibility involves reinforcements by anchoring and shear keys, and the third is removal or placement of rock masses and concrete in critical areas. The problem which arises in practice is to weigh correctly the different pieces of information relating to the assessment of the degree of stability. Foundation failure due to sliding is one of the predominant causes of failure to concrete dams. Sliding can occur along the contact between concrete and rock or along planes of weakness deep in the rock foundation or abutments. A particular problem arises from reservoir slopes instabilities which may generate reservoir waves overtopping the dam. (sdw)