State Key Laboratory for Geomechanics and Deep Underground Engineering, China University of Mining and Technology
School of CML Engineering Architecture, Zhejiang Guangsha Vocational and Technical University of Construction

近水平露天煤矿开采时在端帮边坡上通常布置运输平盘,大型重载卡车的往复运输作业会对边坡覆岩产生显著的循环加卸载效应,导致煤岩体产生一定的初始损伤。同时,露天开采时大规模爆破产生的强冲击动载荷使煤岩体的力学性能进一步劣化,极易诱发边坡大面积失稳。因此,开展循环加卸载损伤条件的煤岩动态力学特性试验研究,对露天煤矿边坡稳定及安全开采具有重要意义。利用分离式霍普金森压杆试验系统及扫描电镜测试系统,对循环加卸载初始损伤状态下煤样的动态力学特性及其损伤断裂机理进行了系统分析。研究结果表明:① 随着加载应变率的增大,煤样动态抗压强度与弹性模量快速增加,应变率对试样动力学特性的强化效应显著;固定应变率条件下,随着初始损伤的增大,动态抗压强度与弹性模量则呈线性快速降低,表明初始损伤对煤样动力学性能具有弱化效应;② 煤样自然状态下存在尺度较小的原生裂纹及孔洞缺陷,损伤的产生导致其内部萌生出新的裂隙及孔洞,并且随着损伤程度的提高,缺陷尺度及数量逐渐增大并快速扩展,这是导致其力学性能弱化的根本原因;③ 随着初始损伤及应变率的增大,煤样破坏方式从张拉破坏向剪切破坏转变,同时其破坏程度、破坏过程中的耗散能及耗能能力呈快速增加的趋势;④ 损伤煤样动态破坏主要以脆性破坏为主,但在初始损伤较高的条件下,其局部能够观测到显著地滑移分离及韧性断口形貌,这也是初始损伤较大状态下煤样耗能较高的主要原因。

In the mining of nearly horizontal open-pit coal mines, transportation flat plates are usually arranged on the endslope. Reciprocating transport operations of large heavy-duty trucks cause significant cyclic loading and unloading effectson the overburden rock, leading to initial damage to the coal rock body. At the same time, the strong impact load generated by large-scale blasting during open-pit mining further deteriorates the mechanical properties of the coal rock body,thereby inducing large area instability of the end-slope. Therefore, it is crucial to conduct experimental research on the dynamic mechanical properties of coal rock under cyclic loading and unloading damage conditions for the stability of the endslopes and safe mining in open-pit coal mines. The dynamic mechanical properties of coal samples under the initial damage condition of cyclic loading and unloading and their damage and fracture mechanism were sys-tematically analyzed byusing the split Hopkinson pressure bar test system and scanning electron mi-croscope test system. The results show that:① With the increase of the loading strain rate, the dynamic compressive strength and elastic modulus of the coal sampleincrease rapidly, and the strengthening effect of the strain rate on the mechanical properties of the sample is significant.The dynamic compressive strength and elastic modulus decrease linearly and rapidly as the initial damage increases underthe condition of fixed strain rate, indicating that the initial damage weakens the mechanical properties of the coal sample;② There exist small-scale primary cracks and pore defects in the natural state of the coal samples, and the occurrence ofdamage leads to the emergence of new cracks and pores inside the coal sample. With the increase of the damage intensity,the defect scale and number gradually increase and expand rapidly, which is the fundamental reason for the weakening ofits mechanical properties; ③ The failure mode of the coal sample changes from tension failure to shear failure with the increase of the initial damage and strain rate, and at the same time, its degree of damage, dissipation energy during the failure process, and energy dissipation capacity show a rapid increasing trend; ④The dynamic failure of the damaged coalsample is mainly brittle failure, but under the condition of high initial damage, significant sliding separation and toughness fracture morphology can be observed locally, which is also the main reason for the high energy dissipation capacity ofthe coal sample under the condition of high initial damage.

国家自然科学基金面上资助项目(51974295,52174090)

陈彦龙,李明,浦海,等. 考虑循环载荷初始损伤效应的煤样动态力学特性试验研究[J]. 煤炭学报,2023,48(5):2123−2137.

CHEN Yanlong, LI Ming, PU Hai, et al. Experimental study on dynamic mechanical characteristics of coalspecimens considering initial damage effect of cyclic loading[J]. Journal of China Coal Society,2023,48(5):2123−2137.