Results of the conducted research aiming to demonstrate the methodology of optimization of dam monolith length (distance between contraction joints), through monitoring the thermal tensile stresses during construction and service life of a concrete gravity dam that is built using the block method, are presented in this paper. A 3D space–time numerical model for phased thermal stress analysis is employed in a large concrete gravity dam case study. For the adopted block dimensions, schedule, and dynamics of construction and material parameters, the thermal stress analysis is conducted, taking into account the following: thermal physical properties of the material, the cement hydration process, heat exchange with the external environment and the reservoir, and self-weight of the structure. The main advantage of the proposed methodology is the possibility of controlling the cracks resulting from thermal tensile stresses in the monolith of a concrete gravity dam, by optimizing the monolith’s length to minimize the zones in which the tensile capacity of concrete is exceeded. The results obtained from the temperature field analysis show that the maximum temperature increase in the dam’s body results from the cement hydration process in combination with summer air temperatures in the construction phase. The aforementioned factors account for the increase in temperature of up to 45.0 °C, while during winter cooling of the structure occurs due to lower temperatures, especially in the surface zones. The results of the stress field analysis show that the extreme values of thermal tensile stresses are present in the process of a sudden or gradual cooling of the concrete when shrinkage occurs. Finally, it is shown that the reduction of the monolith length by 5.0 m (from 20.0 m to 15.0 m) results in a decrease in the extreme thermal tensile stress values by an average of 0.70 MPa (up to 12.0%) in winter and an average of 1.10 MPa (up to 20.0%) in summer; while for the entirety of the analyzed time period, results in a decrease in the extreme thermal tensile stress values by an average of 16.0% (0.93 MPa).
In this research paper, measurement data of air and water temperatures and water levels for "Bileca" reservoir for a period between 1967. and 2017. are presented. Based on the averaged measurement data values, an analytical expressions for amplitude of periodic temperature variation of "Bileca" reservoir are derived and an average annual temperature, as a function of the observed depth, is obtained, based on Bofang model. The obtained results allow thermal stress analysis, which represents an important factor for stability and safety monitoring of dams.
As a part of geotechnical research at several locations in Republika Srpska and Federation of Bosnia and Herzegovina, detailed geotechnical investigations of rock masses were carried out. On the abovementioned exploration sites, terrain is composed of different rock masses (Cretaceous limestone, Palaeozoic gneiss, Mesozoic peridotite and serpentinite). This paper presents an overview of correlation between uniaxial strength, elastic wave velocity and rock mass quality, on one side and in situ obtained results of rock mass deformability, on the other side. Modification of the correlation between deformation modulus and rock mass quality in a form of correctives for each of the equations by Galera, Alvarez and Bieniawski, was also presented. All deformability tests were carried out by the Institute for the Development of Water Resources "Jaroslav Černi" Belgrade.
This paper presents a development of statistical predictive model for relative horizontal displacements of "Vrutci" dam in function of air temperature and reservoir water level, as reversible effects and in function of time passed since the beginning of dam exploitation, which takes irreversible effects into account. Some parts of technical monitoring system, which are important for the model development, are described, with special attention paid to their behaviour. Measurements of horizontal radial displacements of the dam, air temperature and reservoir water levels, which all present data series suitable for regression analysis, are presented. For statistical analysis and coefficient defining in predictor functions, software "Expert Tool" developed by Water Institute "Jaroslav Černi" was employed. A data series with expected measurement values is formed and its level of agreement with actual measured data is determined. The effects of input variables on the predictive model formulation are discussed.
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