The development of technogenic and natural processes in foundations of hydraulic structures is largely due to a change in their hydraulic stress--strain state. Here the most important component is the natural stress state of the masses, which is almost never taken into account in designs [1]. However, numerous and diverse investigations of the state and properties of the rock masses as well as an analysis of the experience of constructing and operating surface and underground hydropower structures located within their limits have revealed the considerable effect of this factor both on the behavior and stability of rock foundations and on design calculations for substantiating the reliability and required safety of operating the structures themselves. The latest data show that the structure of the stress fields and their dependence on natural and technogenic factors are more complicated than was thought earlier. A study of the regularities of the spatial and temporal variability of stress fields at various scale levels both for the natural state of the mass (i.e., before the start of constructing the structures) and for the mass during mining and construction works as well as during operation of the structures and reservoirs can have both a qualitative and quantitative character. In the first case the general characteristics and regularities of a change in the stress field in time and space are investigated, in the second a quantitative determination of the components of the stress vector is carried out.The complex structure and incompletely clear processes of formation of the stress fields hinder their evaluation and require the combined used of methods most suitable for particular geologic conditions [1]. At present rather considerable practical experience has been gained in studying the stress--strain state of rock masses, which are the environment and foundation of hydraulic structures. A comparison of the results of comprehensive studies gives grounds to speak about the existence of certain regularities in the manifestation of current stresses through certain fixed or dynamic characteristics both of the natural geologic environment and of the natural--technogenic system. Such characteristics, called indicators, make it possible at any stage of surveys, construction, or operation of the structure to obtain an idea about the general or particular character of existing stresses in the mass as a whole or in its individual structural elements.It is obvious that quantitative measurements of stresses existing in the mass are top-priority for design studies; however, a qualitative characterization of its stress--strain state obtained on the basis of indirect investigations and analysis of indirect indicators also has great practical significance. This is important at the survey and construction stages for optimal selection of the sites of taking expensive quantitative measurements and correcting design decisions, and in the operating stage it is an essential supplement to geodynamic monitoring [7], especially when in...
Limestones and dolomites of the Barremian stage of the Lower Cretaceous occur in the foundation of the arch dam of the Inguri hydroelectric station. Here and there the llmestones are nonuniformly dolomitized and calcitized. Weak karstification of the rocks on the left bank in the region of development of ancient terraces is observed. The rocks at the site of the dam are divided into six members according to the degree of Jointlng, flaggy character, and composition [1][2][3].Rocks of the Vl member were uncovered in the central part of the construction pit below the river channel. For the most part the pit was excavated in rocks of the IV-V members and only in the region of the left-bank abutment does it encompass rocks of the Ill member.The region of the site is characterized by general monoclinal folding of the rocks with a trend of the beds normal to the river and with a dip at angle 55-60" toward the lower pool. In the river channel is a small anticlinal fold.The site of the dam is located 1 km below the Inglrish fault, and its displacement of the strike-slip type (called a "fault" in the in the design) intersects the right-bank abutment of the dam and has a strike parallel to the river and a 70 ~ dip into the slope.Six Joint systems are developed in the rocks in the region of the dam site. Bedding joints have the greatest dlstribution, length, and width (Fig. I).Permeability of the rocks was studied mainly by the water intake test. Pumping tests were carried out on a small scale.These investigations showed that low values of specific water absorption q = 0.i-0.01 liter/min predominate in the rock foundation of the dam; against the background of the low values there are individual zones with q > 1 liter/min associated with large Joints or due to more frequent Jointlng; the permeability of the right-bank rocks is considerably greater than that of the left-bank rocks, which is explained by the proximity of the right-hank fault.The arithmetic mean values of the specific water absorptions calculated from the data of experimental injections are given in Table 1 [I].The values of the specific water absorptions given in Table 1 indicate a clear tendency toward a decrease of permeability of the mass with depth, but an aquiclude was not found to a depth of 200 m.A further study of the permeability of the dam foundation was carried out on the basis of the data of experimental and actual grouting, during which each 5-m-deep hole of the grout curtain was subjected to hydraulic testing before the start of grouting. As a result of
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