Monitoring changes in the stress-strain state of the Sayano-Shushenskoe hydroelectric station dam in the zone of grouting seeping cracks

Abstract

The experience of carrying out grouting works during construction of high concrete dams attests to a substantial change in the stress state of adjacent columns under the effect of a comparatively small pressure on the surface of the joint between the columns [1]. In this connection the authors as early as the stage of working out the specifications for suppressing seepage through the stretched zone of concrete of the Sayano-Shushenskoe hydrostation dam gave special attention to possible consequences (positive and negative) of injecting grouts into seeping cracks at pressures considerably greater than those observed during grouting of the joints between columns and sections of the same Sayano-Shushenskoe dam during its construction. The firm approved to carry out the grouting works was supposed to inject comparatively viscous grouts of the "Rodur" type, as on other objects in past years, at a pressure exceeding 40 MPa at the pump outlet, which rapidly dropped on advancing along the injection path with a length of 15-20 m and at the mouth of the crack varied within 6-8 MPa with a 3 x 3-m arrangement of the holes and delivery of the polymer material through two holes. Only such a pressure made it possible to provide high-quality and continuous filling of the cracks with grout even with a small opening.During approval of the specifications specialists of the firm asserted that the effect of the grout pressure was limited to a small zone near the hole and additional opening of the cracks would not exceed the compressive strains from the unique press plate, which in cross sections with through cracks usually did not exceed 1 mm.Different regularities of additional opening of cracks that partially disturbed continuity of a cross section about 80 m high to a depth of 15-17 m ought to be expected in the particular case of grouting. The more so as grouting was to be done at upper pool levels (UPLs) close to the normal pool level (NPL), when the cracks without additional interference were in an equilibrium state.In the first years of normal operation it was established during drilling of exploratory holes and inspecting the walls by means of TV cameras that cracks were prevalent in the mass in the form of numerous small disturbance of the solidity of the concrete in zones 1.5-5.6 m high. Exploratory drilling before the start of grouting in 1996 showed the presence in each section of one to three zones with several cracks with a comparatively small opening. According to the readings of long-base deformometers, the openings of the cracks immediately before the start of industrial grouting at an UPL close to elevation 540 m were from 0.33 to 0.98 mm. At the dead storage level all cracks were practically closed. A plan was drawn up for grouting 40 zones in 24 sections to fill the main and small, intensely seeping cracks with grout into the depths of the mass. During grouting one could not assume penetration of cracks into the depths of the mass of the dam in connection with the fact that calculations established a zone of tensi...

Condition of the thrust front of the Sayano-Shushenskaya HPP after completion of repairs to reduce its perviousness

“…During the 16-year period of normal service, it has been repeatedly subjected to large-scale technogenic effects. The most significant of these has been repair work performed to eliminate seepage within a zone of cracking of the first column of the dam between elevations 344 and 359 m. This work was conducted in 1996 in the concrete of the thrust face in sections 19, and 21 -46 at high upper-pool levels (UPL) using "Rodur" twocomponent epoxy resins [1,2]. Injection of the loosened rock bed of the channel dam with a material of similar composition was carried out during the period from 1998 through 2003 [3].…”