Theoretical study on the water-induced weakening of rock based on microstructural mechanics approach

Abstract

For rock structures exposed in the natural condition, water-induced weakening (including water softening and chemical weathering) is thought to be the main reason for its’ stiffness and strength degradation, thus it is of great significance to study the mechanical properties of rocks under the influence of water. In this study, a hexagonal close-packed particle assembly (2D) composed of bonded circular particles with same diameter is considered to approximate a typical soft rock, where the composite contact model for rock materials considering the water-induced wakening is adopted to define the microscopic mechanical reactions between particles. Based on homogenisation theory and lattice model, the stress-strain relationship and strength criteria for rock considering water-induced weakening, as well as the quantitative correlation between macroscopic elastic and strength parameters with microscopic parameters are obtained. The effects of water softening and chemical weathering respectively characterised by saturation and mass loss ratio on macroscopic mechanical behaviours of rock are analysed in detail. The long-term ageing effects of water-induced weakening are also analysed. All results are in good agreement with the laboratory test results, verifying the applicability of the theoretical solution for analysing the effect of water-induced weakening on mechanical behaviours of rock.

Keywords:

• Rock
• macro-micro quantitative correlation
• water softening
• chemical weathering
• ageing effect

Disclosure statement

No potential conflict of interest was reported by the author(s).

Data availability statement

The data that support the findings of this study are available in the supplementary material of this article.

Additional information

Funding

This study was supported by Major Program of National Natural Science Foundation of China (Grant No. 51890911), the National Natural Science Foundation of China (Grant Nos. 12272274, 11872281), the National Natural Science Foundation of China Grant Nos. 52331010, Hainan Province Science and Technology Special Fund (Grant No. ZDYF2021SHFZ264), the Fundamental Research Funds for the Central Universities (Grant No. 22120230302) and the State Key Laboratory of Disaster Reduction in Civil Engineering (Grant No. SLDRCE19-A-06). This support was greatly appreciated.