Experimental investigation on the mechanical properties of sandstone with different numbers of fractures before and after grouting
CHEN Juntao1, 2, 3, YU Junjian1, 2, LI Guo1, 3, XU Changlong1, 2, FAN Mingjin1, 3, WANG Yunhao1, 3, JIAO Bin1, 3
(1. College of Energy and Mining Engineering, Shandong University of Science and Technology, Qingdao, Shandong 266590, China; 2. State Key Laboratory of Coal Mining and Clean Utilization, Beijing 100013, China; 3. National Demonstration Center for Experimental Mining Engineering Education, Shandong University of Science and Technology, Qingdao, Shandong 266590, China)
Abstract：To investigate the influence of the number of fractures on the strength of rock before and after grouting, as well as the patterns of crack propagation, an experimental study was conducted on the mechanical properties of sandstone containing varying numbers of fractures under both ungrouted and grouted conditions. The study employed XTDIC (digital image correlation) and acoustic emission systems to analyze crack propagation patterns from both macroscopic and microscopic perspectives. The experimental results revealed the following: (1) As the number of fractures increased, the duration of the compaction stage in the stress-strain curve decreased, leading to an earlier onset of crack development and propagation. The strength weakening coefficient exhibited a power function growth trend in relation to the number of fractures, resulting in an average compressive strength reduction of 15.82% to 53.32%. Under a 1:1 water-cement ratio slurry, the strength recovery coefficient demonstrated an exponential decrease as the number of fractures increased, improving by 6.76% to 29.27% compared to the ungrouted state, achieving 60.34% to 89.88% of the original rock strength. (2) The number of fractures had a significant impact on crack initiation stress, which increased after grouting. The ratio of crack initiation stress to peak stress before and after grouting decreased with an increasing number of fractures, exhibiting a downward-opening quadratic function relationship. (3) Crack propagation patterns under different fracture numbers showed certain similarities before and after grouting. Cracks predominantly originated from the tips of fractures and interconnected pre-existing fissures, leading to rock bridge penetration and primarily resulting in tensile failure. (4) The acoustic emission ringing count and cumulative ringing count significantly increased with the number of fractures. Grouting could only partially enhance the overall integrity of the rock and alleviate stress concentration at the tips, but it failed to effectively suppress crack propagation and interaction. (5) Theoretical analysis indicated that the stress intensity factor after grouting was lower than that before grouting, suggesting a reduction in stress at the tips of the fractures post-grouting, thereby enhancing the rock′s strength. This finding was corroborated through numerical simulations.
陈军涛1，2，3，喻军健1，2，李 果1，3，徐常龙1，2，范铭今1，3，王云昊1，3，焦 斌1，3. 含不同裂隙数量砂岩注浆前后力学特性试验研究[J]. 岩石力学与工程学报, 2025, 44(7): 1767-1781.
CHEN Juntao1, 2, 3, YU Junjian1, 2, LI Guo1, 3, XU Changlong1, 2, FAN Mingjin1, 3, WANG Yunhao1, 3, JIAO Bin1, 3. Experimental investigation on the mechanical properties of sandstone with different numbers of fractures before and after grouting. , 2025, 44(7): 1767-1781.
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2025, Vol. 44 
