煤柱坝体作为矿井采空区水库的主要承载结构,在多场耦合影响下的损伤失稳机制直接制约采空区水库的长期安全稳定运行。本文借助核磁共振(NMR)研究了“单侧”浸水条件下不同次数循环浸水下煤样T2谱图、孔喉、孔隙率变化和核磁图像演化规律,分析了单侧循环浸水次数不断增加下煤样内部孔隙演化规律以及单轴压缩破坏形态特征,揭示了煤样水浸损伤破坏机制,结果表明,随循环浸水次数的增加,煤样孔隙数、孔喉占比、孔隙率均保持增长的态势,分别增长了67.18%、3.48%、3.49%。煤样单轴抗压强度与残余强度逐渐减小,煤样的平均峰值强度由15.74MPa依次下降到11.76、9.65、8.41MPa,循环浸水9次煤样相较于初始状态煤样的平均单轴抗压强度下降46.56%,平均残余强度从未循环浸水的5.55MPa依次下降到3.08、2.44、0MPa。煤样单侧循环浸水水分子由浸水侧逐渐向煤样内部渗流,最后扩展至整个煤样,进一步造成孔隙率增加。长期的循环浸水对煤样的软化作用十分显著。研究结果为采空区水库空间结构稳定性控制提供了科学依据。

As the main bearing structure of the reservoir in the goaf of the mine,the damage instability mechanism under the influence of multi-field coupling of water immersion directly restricts the long-term OF MINING SCIENCE AND TECHNOLOGY safe and stable operation of the reservoir in the goaf. In this paper,nuclear magnetic resonance (NMR ) was used to study the T2 spectrum,pore throat,porosity change and nuclear magnetic image evolution of coal samples under different times of cyclic immersion under‘ unilateral’ immersion conditions. With the increase of cyclic immersion times,the number of pores,pore throat ratio and porosity of coal sam- ples maintained an increasing trend,which increased by 67. 18 % ,3. 48 % and 3. 49 % respective- ly. The nuclear magnetic resonance imaging further obtained the permeability and pore change law of water molecules in different times of unilateral cyclic immersion of coal samples:the water molecules in unilateral cyclic immersion of coal samples gradually flow from the immersion side to the internal of coal samples,and finally expand to the whole coal samples,further resulting in an increase in porosity. With the increase of cyclic soaking times,the uniaxial compressive strength and residual strength of coal sam- ples decreased gradually. The average peak strength of coal samples decreased from 15. 74 MPa to 11. 76 MPa,9. 65 MPa and 8. 41 MPa,respectively. The average uniaxial compressive strength of coal samples decreased by 46. 56 % compared with that of initial coal samples. The average residual strength decreased from 5. 55 MPa to 3. 08,2. 44 and MPa,respectively. Long-term cyclic immersion has a sig- nificant softening effect on coal samples. Based on the experimental results,the evolution law of internal pores and the morphological characteristics of uniaxial compression failure of coal samples under the in- creasing number of unilateral cyclic immersion were analyzed,and the mechanism of water immersion damage and failure of coal samples was revealed. The experimental results provide a scientific basis for the stability control of reservoir spatial structure in goaf.