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| Real contact area of rock discontinuities: lithological variations and offset displacements |
| LI Yuzong1, 2, ZHANG Ou2, CUI Haoxiang2, LI Yanqing3 |
(1. State Key Laboratory for Safe Mining of Deep Coal Resources and Environment Protection, Anhui University of Science and Technology, Huainan, Anhui 232000, China; 2. School of Civil Engineering and Architecture, Anhui University of Science and Technology, Huainan, Anhui 232000, China; 3. State Key Laboratory for Safe Mining of Deep Coal Resources and
Environment Protection, Huainan Mining (Group) Co., Ltd., Huainan, Anhui 232001, China)
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Abstract The real contact area of red sandstone, green sandstone, limestone, and granite was measured under various offset displacements using pressure-sensitive films. The structural surfaces of all specimens were standardized through high-precision sculpting technology to ensure morphological consistency. This study systematically investigated the effects of lithology, offset displacement, and normal stress on the contact area of the structural surfaces. The experimental results indicate that lithology significantly impacts the contact area, and this effect becomes more pronounced as offset displacement increases. Rocks with higher uniaxial compressive strength are more influenced by offset displacement, exhibiting a more pronounced reduction in contact area in response to offset displacement. A distinct exponential relationship was observed between offset displacement and structural surface contact area: as offset displacement increases, the rate of contact area reduction gradually diminishes. Furthermore, larger normal stress results in greater contact areas, with the influence of normal stress being more pronounced at lower offset displacements. The structural surfaces were divided into nine regions to analyze the characteristics of contact area distribution after offset displacement. The results demonstrate that, following offset displacement, the contact area tends to concentrate in regions with higher joint roughness coefficient (JRC), and this tendency becomes more evident as offset displacement increases. Analysis of the normal stress applied to the specimen surface and the actual stress within the specimen revealed that the actual stress is typically several times greater than the normal stress. During offset displacement, the actual stress can exceed the normal stress by hundreds of times in some instances. This study provides critical insights into the evolution of contact area under dynamic offset displacement in multi-lithology rocks.
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2025, Vol. 44 
