School of Safety Engineering, China University of Mining and Technology
Key Laboratory of Gas and Fire Control for CoalMines Ministry of Education, China University of Mining and Technology

深部煤体多处于三向不等应力状态,为了研究冲击载荷下煤样动力学特性,通过真三轴霍普金森压杆实验系统,开展煤样动态破坏力学实验。利用该系统装置可分别对煤样提供单轴 (σ1≥σ2=σ3=0)、双轴 (σ1≥σ2 > σ3=0) 和真三轴 (σ1 ≥σ2 ≥σ3 ≠ 0) 预应力 (其中,σ1 为轴向预应力;σ2 为竖直预应力;σ3 为水平预应力),从而实现高应变率下煤样力学性能测试。通过对比分析单轴与真三轴静载预应力状态下煤样动态力学特征及差异性,研究了煤样动态峰值强度、峰值应变以及宏观破碎形态与三向静载预应力、应变率的关系。研究结果表明:真三轴冲击载荷下煤样力学曲线基本一致,均包含线弹性阶段、塑性阶段和破坏阶段 3 个阶段。单轴与真三轴冲击载荷下煤样峰值强度、应变具有明显的应变率效应,随着应变率的增加,单轴与真三轴冲击载荷下煤样峰值强度及峰值应变逐渐增大;比较单轴与真三轴冲击,三向静载预应力对煤样动态破坏具有明显的约束性,煤样的力学强度较单轴冲击时增大。保持 σ2 与 σ3 不变,煤样的力学峰值强度、应变随着轴向预应力 σ1 的增加整体呈降低趋势。随着应变率的增加,单轴冲击载荷下的煤样逐渐破碎至颗粒或粉末状,碎块平均粒径随应变率的增加线性降低;而三向静载预应力状态下的煤样呈现宏观断裂,碎块平均粒径随轴向预应力 σ1 的增加线性降低,但破坏程度相对单轴冲击较低。

Deep coal is mostly in a three-dimensional unequal stress state. In order to study the dynamic characteristics ofcoal under impact load, the dynamic failure mechanics experiment of coal was carried out by true triaxial Hopkinson experimental system. This system can be used to provide uniaxial (σ1≥σ2=σ3=0), biaxial (σ1≥σ2 > σ3=0) and true triaxial (σ1≥σ2≥σ3 ≠ 0) pre-stressing for coal samples respectively(where, σ1 is axial prestress; σ2 is vertical prestress; σ3 is horizontalprestress), so as to realize the mechanical property test of coal samples at high strain rates. By analyzing the dynamicmechanical characteristics and differences of coal under uniaxial and true-triaxial static pre-stress, the relationships of dynamic peak strength, peak strain and macroscopic fracture morphology with three-dimensional static pre-stress and strainrate were studied. The results show that the mechanical curves of coal under true triaxial impact load are basically thesame, including three stages: linear elastic stage, plastic stage and failure stage. The peak strength and strain of coalsamples under uniaxial and true triaxial impact loads have obvious strain rate effects .With the increase of strainrate, thepeak strength and peak strain of coal under uniaxial and true triaxial impact loading increase gradually. Compared withuniaxial and true triaxial impact, the three-dimensional static load pre-stress has obvious constraint on the dynamic failureof coal specimen, and the mechanical strength of coal specimen is higher than that of uniaxial impact. The mechanicalpeak strength and strain of the coal sample decrease with the increase of the principal stress σ1 while the stress σ2 and σ3 remain unchanged. With the increase of strain rate, the coal under uniaxial impact load is gradually broken into particles orpowder, and the average particle size of the fragments decreases linearly with the increase of strain rate. However, the coalunder three-dimensional static pre-stress presents soma macroscopic fractures, and the average particle size of fragmentsdecreases linearly with the increase of σ1 while the damage degree is lower than that of uniaxial impact.

国家自然科学基金资助项目(52074276);国家重点研发计划资助项目(2022YFC3004702)

沈荣喜,顾周杰,王恩元,等. 真三轴条件下煤样冲击动力学及破坏特征实验研究[J]. 煤炭学报,2023,48(5):2168−2178.

SHEN Rongxi,GU Zhoujie,WANG Enyuan,et al. Experimental study on impact dynamics and failure charac-teristics of coal specimen under true triaxial conditions[J]. Journal of China Coal Society, 2023, 48(5):2168−2178.