Evolution mechanism of deformation parameters of strongly weathered granite on the bank slope during the operation period of pumped storage power stations

Abstract

[Objective] The periodic fluctuation of reservoir water level will lead to the strength deterioration and deformation exacerbation of the rock and soil on the reservoir bank slope, which affect the stability of the reservoir bank slope. [Methods] The uniaxial compression tests and CT scanning techniques were employed to study the evolution law of elastic modulus(E),Poisson's ratio(v), and microstructural parameters of strongly weathered granite after multiple cycles of soaking-non soaking in Jiangxi Yanshan Pumped Storage Power Station. The correlation between deformation parameters and microstructure parameters of strongly weathered granite was obtained. Observing The microstructural changes of strongly weathered granite were observed after multiple soaking-non soaking cycles using a polarizing microscope, the structural change characteristics of strongly weathered granite were obtained, and its evolution mechanism was explored by combining the evolution laws of deformation parameters and microstructural parameters. [Results] The result showed that after the 8th soaking-non soaking cycle, the elastic modulus of strongly weathered granite decreased by 50. 34%, and the Poisson's ratio increased by 41. 85%; The projected porosity of the three cross-sections increased by 20. 34%, 19. 18%, and 16. 29% respectively, and the number of pores increased by 52. 99%,42. 24%, and 30. 59% respectively. [Conclusion] The research result indicate that:( 1) The elastic modulus of strongly weathered granite gradually decreases and the Poisson' s ratio gradually increases with the increase of soaking-non soaking cycles. The deformation parameters deteriorate significantly during the first 8 cycles of soaking-non soaking, and deteriorate slowly after 8 cycles.(2) The projected porosity and void number increase gradually with the increase of soaking non soaking cycles, while the average porosity and void area and porosity and void distribution dimension decrease gradually. After 8 cycles of soaking-non soaking, the amplitude of changes in microstructural parameters significantly decreased.(3) Multiple soaking-non soaking cycles caused the development and expansion of internal pores and cracks in strongly weathered granite, resulting in an increase in the number of pores and cracks. Changes in the microstructure of the rock interior lead to deterioration of deformation parameters, reducing the rock's ability to resist deformation.

Keywords

cycles of soaking-non soaking / strongly weathered granite / deformation parameters / microstructure / pumped storage power station / slope / elastic modulus / mechanical properties