ISSN 1003-8035 CN 11-2852/P

    不同冻融条件下岩石损伤力学特性及能量演化机制研究

    Study on damage mechanical properties and energy evolution mechanism of rock under different freeze-thaw conditions

    • 摘要: 为探究不同冻融条件下砂岩损伤力学特性及其能量演化规律,明确冻融周期与循环次数对岩石力学性能劣化及能量损伤机制的协同作用,以新疆塔什店煤矿8号煤层顶板砂岩为研究对象,开展不同冻融周期(6 h、12 h、18 h、24 h)和不同冻融循环次数(5次、10次、15次、20次)的冻融试验,通过采用单轴压缩实验获取其峰值应力、峰值应变及弹性模量变化规律,并基于能量计算原理及最小耗能原理,揭示不同冻融条件下能量损伤演化机制。结果表明:冻融损伤会随着冻融周期-循环次数的增加而增加,岩石峰值应力、弹性模量与冻融周期-循环次数呈负相关,而岩石应变与冻融周期-循环次数呈正相关;基于能量原理,在OA-压密阶段能量存储与能量耗散呈微小变化特征,在AB-线弹性变形阶段所存储的弹性应变能随着冻融周期-循环次数的增加而逐渐减弱,在BC-塑性变形阶段弹性应变能占总应变能的比重逐渐减小,而耗散能占总应变能比重逐渐增加,在CD-峰后破坏阶段所储存的弹性应变能快速转化为耗散能并伴随能量释放;此外,在岩石应力峰值前,由于受到冻融周期-循环次数的影响,会削弱岩石的弹性应变能累积速率,在应力峰值处,岩石的弹性应变能累积速率达到最小。研究表明,冻融周期对岩石力学劣化的影响大于循环次数,二者协同作用会进一步加剧损伤,研究成果对可为寒区工程建设、岩石损伤评估和冻融损伤防控提供理论依据。

       

      Abstract: This study aims to investigate the damage mechanical properties of sandstone and its energy evolution behaviour under various freeze-thaw conditions, clarifying the synergistic effects of freeze-thaw cycle duration and the number of cycles on the rock mechanical deterioration and energy damage mechanism. Sandstone from the roof of No.8 coal seam at Tashidian Coal Mine in Xinjiang was selected as the research subject. Freeze-thaw experiments were conducted with different freeze-thaw cycle durations (6 h, 12 h, 18 h, 24 h) and different freeze-thaw cycles (5 times, 10 times, 15 times, 20 times). Uniaxial compression tests were performed to obtain peak stress, peak strain, and elastic modulus variations. Based on energy calculation principles and the principle of minimum energy dissipation, the evolution mechanism of energy damage under different freeze-thaw conditions was revealed. The results indicate that freeze-thaw damage increases with longer cycle durations and more freeze-thaw cycles. Peak stress and elastic modulus of the rock are negatively correlated with freeze-thaw periods cycle duration and number, while strain shows a positive correlation. According to energy principles, during the OA-compaction stage, energy storage and dissipation exhibit minor changes. In the AB-linear elastic deformation stage, stored elastic strain energy gradually decreases with increasing freeze-thaw duration and cycles. During the BC-plastic deformation stage, the proportion of elastic strain energy to total strain energy gradually decreases, whereas the dissipated energy proportion increases, indicating accelerated internal damage with increased freeze-thaw duration and cycles. In the CD-post-peak failure stage, stored elastic strain energy rapidly converts to dissipated energy accompanied by energy release. Furthermore, prior to peak stress, the rate of elastic strain energy accumulation is weakened due to freeze-thaw effects, reaching its minimum at peak stress. The study demonstrates that freeze-thaw cycle duration has a greater impact on mechanical degradation than the number of cycles, and their synergistic effect exacerbates rock damage. These findings provide a theoretical basis for cold region engineering construction, rock damage assessment, and freeze-thaw damage prevention and control.

       

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