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ABSTRACT Many high-pressure concrete dams are erected by leaving column cutting joints. After curing of the concrete the cutting joints are filled with cement grout under a certain amount of pressure. After hardening of the grout the dam becomes monolithic.
Before joints grouting hydraulic tests are conducted to determine the joints widening. When grouting the joints, which are separated from the sides of the canyon just by one section of the dam, discharge pressure is passed through this section on the rock massif. By cyclic loading with water pressure, (i.e., using it as a large-scale stamp), and measuring the additional and residual disclosures of the joint, deformation characteristics of the rocky massif in contact with the concrete dam can be determined. Formula for calculating the deformation modulus of the rocks foundation is given in the paper. Such studies, accomplished at the erection of Krasnoyarsk and Chirkej dams (Russia), have shown the ability to not only solve the abovementioned task, but compact the superficial layer of the rocky massif when a sufficiently large discharge water pressure is applied.
1 INTRODUCTION To determine the deformation characteristics of the bedrock, the stamps loading method is sometimes used. However, in the construction of large dams this method has a drawback: the size of the load-applying stamp is disproportionately small compared to the area of the dam foot. In addition, such experiments require a significant amount of work, time and money. But sometimes we can do the work with a new and inexpensive method.
2 THE NEW METHOD Many high concrete dams are erected by leaving temporary column cutting (heat-shrink) joints that are filled afterwards by pumping cement grout via embedded tubes in the concrete. Grouting joints in arch dams are radial, i.e. intersections. For gravity dams intersection joints near the head surface are grouted sometimes. Before grouting the joints are hydraulically tested under a certain amount of water pressure. Knowing the dimensions of the loading platform, the amount of load applied and the opening displacement of the joint under the water pressure, the deformability of the system, including both the concrete and the rocky massif, can be determined.
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