Impact of concrete hardness of rockfill dam seepage-control face on its stress-strain state

Гидротехническое строительство

Introduction. It is known that at durable loads accommodation the concrete deformation modulus becomes 2÷3 times as less due to creep. The study fulfilled by the author permitted assessing the impact of stress relaxation in concrete of rockfill dam seepage-control face on its stress-strain state (SSS). Materials and methods. SSS was studied with the aid of numerical modeling by the finite element method. There was considered a 100 m high dam. Calculations were conducted for a wide range of variations of rockfill linear deformation values (from 60 to 480 МPа) and two values of its Poisson’s ratio (0.2 and 0.3). Various alternatives of under-face zone structural designs were considered. Modeling was made of shear characteristics decrease in the contact between the face and concrete bedding due to the arrangement of a bitumen mastic layer. Results. It was established that concrete linear deformation value Eb differently affects bending moments and longitudinal forces in the face. Decrease of Eb predominantly decreases bending moments from the face cross bending deformations but has a small impact on the longitudinal forces in it and bending moments from longitudinal bending deformations. Bending moments of cross bending are nearly in direct proportion with value Eb. Conclusions. The processes of creep and stress relaxation in concrete has a favorable effect on the face crack resistance because they decrease stresses in concrete. However, the value of stresses in the face concrete is not in direct proportion with concrete linear deformation modulus value Eb. It was established that the decrease of Eb by 60% decreases tensile stresses in the face concrete by approximately 30%. To decrease the risk of cracking in the face the quick reservoir impoundment is not recommended. In the analysis of concrete face rockfill dam structural design it is quite justified to analyze SSS at modulus Eb corresponding to its initial value without consideration of concrete creep because this case is more dangerous.