Experimental Study on Damage and Failure of Coal-Pillar Dams in Coal Mine Underground Reservoir under Dynamic Load

Abstract

The stability of coal-pillar dams in underground hydraulic engineering works is affected not only by long-term water erosion but also by dynamic loading induced, for example, by roof breaking or fault slipping. In this paper, the water absorption characteristics of coal samples from western China were studied by nondestructive immersion tests, and a high-speed camera was used to monitor SHPB tests on samples of varying water content and subjected to various strain rates. Besides, the coal-pillar dam is numerically simulated based on the experimental data and the actual engineering conditions. The results show that, given low strain rate and high water content, the compaction stage accounts for most of the stress-strain curve, whereas the elastic stage accounts for only a relatively small fraction of the stress-strain curve. The dynamic compressive strength and elastic modulus follow exponential and logarithmic functions of strain rate, respectively, exhibiting a significant positive correlation. As the water content increases, the dynamic elastic modulus increases almost linearly, and the compressive strength decreases gradually. Under the same impact load, samples with greater water content fail more rapidly, and the failure is exacerbated by the propagation of parallel cracks to staggered cracks. The average size of coal fragments decreases linearly with increasing strain rate and water content. Simulations indicate that dynamic loading increases the stress concentration on both sides of the dam and expands the high-stress area and plastic zone. The results provide guidance for designing waterproof coal pillars and underground reservoir dams.

Characteristics of waterproof failure and optimal width of narrow coal pillars under the coupled effects of mining, excavation and seepage

“…Experimental research is an important method for studying waterproof coal pillars (Chen et al 2022b). Currently, experimental investigations on waterproof coal pillars primarily focus on the weakening effects of water content on the mechanical parameters of coal samples (Yao et al 2021b). Yao et al (2020) conducted tests involving variable-angle shear on coal samples with different water contents, while (Lu et al 2016;Wang et al 2018;Zhang and Nie 2020) performed uniaxial and triaxial tests on coal samples with varying water contents.…”

Failure Characteristics of the Water-Resisting Coal Pillar under Stress-Seepage Coupling and Determination of Reasonable Coal Pillar Width

“…Based on field experience and numerical model studies, Mathey et al [24] proposed another South African squat coal pillar strength formula. Combined with numerical simulation research, Yao et al [25] monitored coal samples with different water contents and strain rates through a non-destructive immersion test, which is significant for the design of the water-resisting coal pillar.…”

Mechanical properties and damage constitutive model of coal specimen with different moisture under uniaxial loading

“…Recent years has witnessed extensive researches on the mechanical properties of coal rock under water interaction. For varying-MC coal rock samples (i.e., coal rock samples that contain varying contents of moisture), the quantitative relation between MC and macroscopic mechanical parameters (such as cohesion, elastic modulus, internal friction angle and uniaxial compressive strength) was obtained in uniaxial compression tests (Erguler and Ulusay, 2009; Hawkins and McConnell, 1992; Song et al., 2022; Yang et al., 2018; Yao et al., 2016) and shear tests (Li et al., 2020; Yao et al., 2020, 2021). It was found that the peak stress, internal friction angle, cohesion and elastic modulus decrease with the rise of MC; meanwhile, the tensile failure mode alters to the shear failure mode (Tang, 2018; Tang et al., 2021).…”