Available online at ScienceDirect. Procedia Engineering 111 (2015 )

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1 Available online at ScienceDirect Procedia Engineering 111 (015 ) XXIV R-S-P seminar, Theoretical Foundation of Civil Engineering (4RSP) (TFoCE 015) The investigation of soils in the Zhiguli Hydroelectric Station foundation contact area Sergey V. Evdokimov a *, Aleksey A. Romanov b a Samara State University of Architecture and Civil Engineering (SSUACE), Molodogvardeyskaya St 194, Samara, , Russia b OAO RusGidro Zhigulevskaya Hydroelectric Power Station, Molodogvardeyskaya St. 194, Samara, , Russia Abstract The foundation of the Zhiguli Hydroelectric Station consists mostly of poli-mineral clays, with montmorillonite prevailing. Montmorillonite composition of clay bond and its base exchange capacity have become the subject of the Zhiguli Hydroelectric Station foundation special analysis. The paper presents the results of the foundation soil investigation conducted during the whole period of the Zhiguli Hydroelectric Station operating life. The change in hydrochemical conditions in foundation contact area of the station is taken into account. The authors analyze two main streams of research: that of physical and mechanical properties of soils conducted according the traditional methodology and that of mineralogical properties of soils carried out according new special methods. According to the obtained data the authors estimate the existing soils condition and make a forecast of soils further behaviour in the Zhiguli Hydroelectric Station foundation contact area. 015 The Authors. Published by Elsevier B.V. 015 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license Peer-review under responsibility of organizing committee of the XXIV R-S-P seminar, Theoretical Foundation of Civil ( Peer-review Engineering under (4RSP) responsibility of organizing committee of the XXIV R-S-P seminar, Theoretical Foundation of Civil Engineering (4RSP) Keywords: Zhiguli Hydroelectric Station; Zhigulyovskaya GES; Foundation soil; Contact area; Physical and mechanical properties of soils; Mineralogical properties of soils; Montmorillonite composition; Cannel clays. 1. Introduction There are many unique powerful hydraulic engineering structures operating in Russia nowadays. These complex structures help to obtain considerable economic benefits in various fields of national economy, yet they strongly influence natural environment [1-8]. Scholars and scientists working at Samara state university of architecture and * Corresponding author. Tel.: address: sali5@mail.ru, sgasu@samgasu.ru The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license ( Peer-review under responsibility of organizing committee of the XXIV R-S-P seminar, Theoretical Foundation of Civil Engineering (4RSP) doi: /j.proeng

2 184 Sergey V. Evdokimov and Aleksey A. Romanov / Procedia Engineering 111 ( 015 ) civil engineering pay great attention at such structures reliability growth, at working out conditions of these structures safe use [9-15], and at decreasing their negative effects in urban areas [16-19]. The Zhiguli Hydroelectric Station with a capacity of 300 MV has been operating in the Central region if Russia for 60 years. It was the first powerful hydraulic engineering structure in the country with a soil foundation. It has always been the matter of great importance to thoroughly control water-retaining structures and foundation soils [0-3]. The foundation of the Zhiguli Hydroelectric Station consists mostly of poli-mineral clays, with montmorillonite prevailing [4]. Montmorillonite composition of clay bond and its base exchange capacity have become the subject of the Zhiguli Hydroelectric Station foundation special analysis conducted during the whole period of the Zhiguli Hydroelectric Station operating life. The change in hydrochemical conditions in foundation contact area of the station has also been taken into account. Besides, semisolid fine-dispersed clays are characterized by specific rheological properties, which means they can decrease reliability when being under constant stress. This fact caused the start of the new research of these clays long-time strength in the Zhiguli Hydroelectric Station foundation contact area. The undertaken research is aimed at evaluating the up-to-date condition of foundation soils and concrete in the Zhiguli Hydroelectric Station foundation contact area as structural reliability of all hydraulic engineering structures of Zhigulyovskaya GES depend on it.. Research The undertaken research is aimed at evaluating the up-to-date condition of foundation soils and concrete in the Zhiguli Hydroelectric Station foundation contact area and at estimating foundation soils behaviour while Zhigulyovskaya GES further operating. The problems to be solved are as follows: firstly, to estimate foundation soils long-time strength in the Zhiguli Hydroelectric Station foundation contact area; secondly, to visually check the up-to-date condition of foundation soils and concrete in the Zhiguli Hydroelectric Station foundation contact area. Cannel clays of Stratum 7 and Stratum 9 were chosen for analysis as these strata are considered to be the most important for the Zhiguli Hydroelectric Station foundation. These clays had to undergo long-time strength tests. Long-time strength of the clays was tested with soil monolith taken as sample from test holes 3i, 4i, 5i, 1i and 1i. Direct shear devices and triaxial compression machines (stabilometers) were used during the experiment. Before the experiment the samples moisture content, specific gravity and plastic properties were compared with those in the technical project. Before the final testing began the researchers had also used the scheme of unconsolidated shift to calculate the so-called conventional strength on design stage. At the initial stage of the research the investigators carried out a number of methodological experiments to elicit and eliminate drawback of the usual research methods. The results of static processing of the foundation clays mechanical properties demonstrated that cannel clays conventional strength (6 kg/sm ) has the following middleminimum characteristics: Stratum 7.8 kg/sm (15 tests); Stratum 9.36 kg/sm (0 tests). These conventional strength results were compared with those obtained at design stage. This comparison showed that the clays strength has not changed during the whole Zhiguli Hydroelectric Station operating life. The clays long-time strength tests demonstrated the following results: Under step impact of shear force (6 kg/sm ) cannel clays long-time strength is approximately 0.75 (compared with conventional); Under instantaneous impact of shear force the coefficient of strength reduction in the course of operating time is (compared with conventional); Tests in the triaxial compression machine showed that the coefficient of long-strength reduction is (compared with conventional); Check tests of clays strength which is less than long-strength is approximately 0.63 (compared with conventional);

3 Sergey V. Evdokimov and Aleksey A. Romanov / Procedia Engineering 111 ( 015 ) Tests in direct shear devices showed that the coefficient of strength reduction in the course of operating time is approximately 0.7 (compared with conventional). The experiments showed that in general the coefficient of cannel clays strength reduction in the course of operating time is approximately 0.7 (compared with conventional and calculated by different methods). The cannel clays (which form the Zhiguli Hydroelectric Station foundation) long-strength has the following minimum characteristics: Stratum kg/sm ; Stratum kg/sm. According to the experiment conducted on the design stage middle-minimum characteristics of shearing resistance (long-strength had not been taken into account) were as follows: Stratum 7.05 kg/sm ; Stratum kg/sm. If we take these results and use the coefficient of cannel clays strength reduction in the course of operating time ( К 0,7) we obtain the following characteristics of foundation soils long-strength: Stratum kg/sm ; Stratum kg/sm. The comparison of the clays long-strength on the design stage and the results obtained now we see that the clays strength has not changed during the whole Zhiguli Hydroelectric Station operating life. Some slight differences in shear resistance index can be explained by different number of experiments conducted on different stages. On the stage of the project appraisal some calculations of the hydraulic engineering structure resistance to in-plane shear and to radial surface shear (in case the soils loose cohesion). Calculated characteristics for such cases were taken as follows: Middle-minimum rate of shear tg ; Strength 1.0 kg/sm. So, this proves that the long-strength index fulfil operation requirements. Middle-minimum shear resistance calculations for foundation cannel clays of Stratum 7 and Stratum 9 taken from test holes are shown in Table 1. To evaluate the up-to-date condition of foundation soils and concrete in foundation contact area the researchers visually checked the test holes in the Zhiguli Hydroelectric Station. The foundation of the hydraulic engineering concrete structures was created with particular care. All possible means of protecting foundation clays from destructive external effects and pressure waters were taken. Table 1. Middle-minimum shear resistance calculations. Strata tg 0 C kg/sm tg Stage St design St test hole St design St test hole According to the foundation pit documents and its final inspection, more than 90% of the pit was built without destructing natural properties of the foundation soils. There was minimal soils freezing, excessive moistening and predrying on some segments of no vital importance. These violations have not influenced the quality of the hydraulic engineering structure concrete foundation. The most frequent in the Zhiguli Hydroelectric Station foundation contact area strata: 1 d Q, 3Q 1, 1N kn, 6N kn (1) were heavy flexible or semisolid. The foundation soils bulk density varied within.0.1 (and down to 1.9 as min). Their saturation coefficient fluctuated from 0.96 to 1.0, airspace ratio fluctuated from 0.6 to 0.9, and the consistency index from 0.0 to 0.15.

4 186 Sergey V. Evdokimov and Aleksey A. Romanov / Procedia Engineering 111 ( 015 ) After the Zhiguli Hydroelectric Station had been built and put into operation and the water basin had been filled the hydrochemical conditions in the foundation contact area became completely different. The influence of hydrochemical conditions on foundation soils and concrete can also be determined by visual checking. The check was performed while taking soil monolith samples from test holes. Undisturbed concrete core was extracted from seven different test holes and checked visually for leaching, especially its near-contact zone. Foundation soil monolith samples were also thoroughly checked and examined. The investigators also had a possibility to compare the foundation soils condition and characteristics with those recorded on the design stage before the foundation pit was filled with concrete. The check showed no visual changes in either foundation soils or concrete condition. The evidence of the influence of concrete on the Zhiguli Hydroelectric Station foundation was not revealed either. The estimation of concrete leaching in its near-contact zone was performed by immediate determination of concrete drainage properties. No zones with high drainage properties were found in the concrete foundation soils contact area in all test holes. The calculations of leaking coefficient obtained while dewatering are within concrete natural drainage properties. The near-contact zone is also characterized by low leaking coefficient typical for water-resisting rock. The obtained data confirms that the Zhiguli Hydroelectric Station foundation is safe and reliable. 3. Conclusion The research yielded the following conclusions: Scientific drilling of test holes in the Zhiguli Hydroelectric Station foundation area made possible to observe and register concrete close contact with foundation clays. Quaternary and cannel clays in the penetrated section of the hydraulic station foundation area (up to 60 m deep) are semi-solid or solid; Specially performed experiments showed that cannel clays long-strength ability is approximately 0.7 (compared with conventional strength and calculated by different methods). The comparison of the clays long-strength on the design stage and the results obtained now we see that the clays strength has not changed during the whole Zhiguli Hydroelectric Station operating life. The obtained cannel clays long-strength characteristics are 1.5 times higher than those taken into account on the design stage; Investigations of the hydraulic station foundation deformations, soils settlements, sections decline and horizontal displacements testify that consolidation deformations are quite normal; there is no destruction of natural properties of foundation soils in the Zhiguli Hydroelectric Station contact area. All that verifies the reliable service of the structure. References [1] A.A. Romanov. Zhigulyovskaya GES. Hydroelectric structures operation. Technical publication. Book I. Samara, 010, 360 p. [] M.I. Balzannikov, V.V. Elistratov, Renewable energy sources. Aspects of complex use. Samara: SGASU p. (in [3] M.I. Balzannikov, Solving the problems of power generation based on renewable energy sources in the Middle Volga Region. Academician Yu.S. Vasiliev s school of Science in the field of energy and environmental protection: Proceedings of the SPb: SPbSPU pp (in [4] M.I. Balzannikov, V.V. Elistratov, Energy production and environment. Samara region Ecology, Samara regional department proceedings, Part I, Samara, SGASU pp (in [5] M.I. Balzannikov, Basis for installed capacity of HPP in hydroelectric system. Higher education news. Construction. 014, 8. pp (in [6] M.I. Balzannikov, M.V. Rodionov, V.A. Seliverstov, Increasing the environmental safety of earth hydrotechnical structures. Vestnik of SSUACE. Town Planning and Architecture, 011, 1. pp doi: /vestnik (in [7] M.I. Balzannikov, Yu.M. Galitskova, The Causes of Large Plains River Shore and Collapse Research and Measures to Prevent It, Eastern European Scientific Journal (Gesellschaftswissenschaften): Düsseldorf (Germany): Auris Verlag pp [8]. M.I. Balzannikov, E.G. Vyshkin Hydroelectric power plants reservoirs and their impact on the environment, Environment. Technology. Resources. Proceedings of the 8-th International Scientific and Practical Conference. Vol. 1. Rezeknes Augstskova, Rezekne, RA Izdevnieciba pp (in [9] S.V Evdokimov, T.V. Dormidontova, Assessment of reliability of hydraulic structures. Vestnik of SSUACE. Town Planning and Architecture, 1. pp doi: /vestnik (in

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