Gao Xicai, Liu Shuai, Zhao Cheng, Yin Jianhui, Fan Kai
State Key Laboratory of Coal Resources in Western, Xi'an University of Science and Technology, Xi'an 710054, China.
Key Laboratory of Western Mine Exploitation and Hazard Prevention, Ministry of Education, Xi'an University of Science and Technology, Xi'an 710054, China.
Materials (Basel). 2022 Aug 21;15(16):5772. doi: 10.3390/ma15165772.
The back-filling body in the gob-side entry retaining is subject to continuous disturbance due to repeated mining. In this study, uniaxial and cyclical loading tests of back-filling concrete samples were carried out under laboratory conditions to study damage evolution characteristics with respect to microscopic hydration, deformation properties, and energy evolution. The results showed that, due to the difference in the gradation of coarse and fine aggregates, the cemented structure was relatively loose, and the primary failure modes under cyclical loading were tensile and shearing failure, which significantly decreased its strength. With an increasing number of loadings, a hysteresis loop appeared for the axial strain, and the area showed a pattern of decrease-stabilization-increase. This trend, to a certain extent, reflected the evolution of the cracks in the back-filling concrete samples. The axial, radial, and volumetric plastic strain curves of the back-filling concrete samples showed a "U" shape. The plastic strain changed in three stages, i.e., a rapid decrease, stabilization, and a rapid increase. A damage parameter was defined according to the plastic strain increment to accurately characterize the staged failure of the samples. The plastic strain and energy dissipation of the samples were precursors to sample failure. Prior to the failure of the back-filling samples, the amount and speed of change of both the plastic strain and energy parameters increased significantly. Understanding the characteristics of plastic strain, damage evolution, and energy dissipation rate of the back-filling samples are of great reference value for realizing real-time monitoring of back-filling concrete in the gob-side entry retaining and providing early warning of failure.
沿空留巷中的充填体由于反复开采而受到持续扰动。在本研究中，在实验室条件下对充填混凝土试样进行了单轴和循环加载试验，以研究其在微观水化、变形特性和能量演化方面的损伤演化特征。结果表明，由于粗、细骨料级配的差异，胶结结构相对疏松，循环加载下的主要破坏模式为拉伸和剪切破坏，这显著降低了其强度。随着加载次数的增加，轴向应变出现滞后环，其面积呈现减小-稳定-增大的规律。这种趋势在一定程度上反映了充填混凝土试样中裂纹的演化。充填混凝土试样的轴向、径向和体积塑性应变曲线呈“U”形。塑性应变分三个阶段变化，即快速减小、稳定和快速增大。根据塑性应变增量定义损伤参数，以准确表征试样的阶段性破坏。试样的塑性应变和能量耗散是试样破坏的前兆。在充填试样破坏之前，塑性应变和能量参数的变化量和变化速度均显著增加。了解充填试样的塑性应变、损伤演化和能量耗散率特征，对实现沿空留巷中充填混凝土的实时监测和提供破坏预警具有重要参考价值。
