Shear deformation patterns of basalt joint surfaces under dry-wet cycles and improved shear strength calculation model

Abstract

[Objective] The rock mass within the slope hydro-fluctuation zone of large reservoirs often deteriorates due to dry-wet cycles. The aim is to investigate the deterioration patterns of the shear characteristics of basalt joint surfaces in the hydro-fluctuation zone under dry-wet cycles. [Methods] Basalt from the slope hydro-fluctuation zone of the Baihetan Reservoir was selected as the research object. Joint surface samples with roughness coefficients similar to those of natural joint surfaces were prepared using the splitting method. Direct shear tests and three-dimensional morphological scanning tests were performed on the basalt joint surfaces under different dry-wet cycles. The shear mechanical properties and the deterioration patterns of mesoscopic morphological parameters of the joint surfaces were analyzed, and a JRC-JCS model considering the dry-wet cycles was established. [Results] The result showed that with an increasing number of dry-wet cycles, the shear strength showed a deterioration trend of “rapid at first and then slowing down”. During the 12 dry-wet cycles, the deterioration in shear strength in the first five cycles accounted for 82.2% of the total deterioration, and the mesoscopic parameters of the joint surfaces also decreased accordingly. The shear strength calculated by the JRC-JCS model considering dry-wet cycles fitted well with the laboratory test values. [Conclusion] The findings reveal that the deterioration patterns of the mesoscopic morphological parameters and the roughness coefficient JRC of the joint surfaces are consistent with those of the macroscopic shear strength, indicating a good correlation between morphological parameters and shear strength. Based on the JRC-JCS model considering dry-wet cycles, the changes in mesoscopic morphological parameters of the joint surfaces can be used to predict the shear strength deterioration patterns of jointed rock masses.

Keywords

water-rock interaction / shear characteristics / morphology scanning / joint surface roughness coefficient / dry-wet cycles / mechanical properties / influencing factors / deterioration