SDS水溶液作用下低煤阶煤体物理力学特性及损伤实验研究

Experimental study of physical and mechanical characteristics and damage evolution of low-rank coal subjected to action of SDS aqueous solution

为了探究SDS水溶液对低阶煤煤体物理力学特性的影响及损伤程度,采用十二烷基硫酸钠(SDS)水溶液为有机溶液,以低煤阶煤体(阜新长焰煤)为研究对象,通过电镜扫描、压汞实验、纵波波速实验和单轴压缩实验,对SDS水溶液浸泡前后煤样的微观孔隙结构、孔隙率、纵波波速、峰值强度及弹性模量进行表征,分析煤样在SDS水溶液作用下物理力学特性随浸泡温度的变化规律,并建立了SDS水溶液作用下受荷载煤样的损伤演化模型,探讨煤样损伤机制。结果表明:(1)经SDS水溶液作用后,煤样微观孔隙分布不均匀,孔隙率随浸泡温度增加而增加,在55℃时,孔隙率为57%,比原煤样孔隙率增加了46%;煤样纵波波速、峰值强度和弹性模量均随浸泡温度增加而降低,在55℃时,纵波波速、峰值强度和弹性模量分别为571m/s、6.73MPa、356MPa,比原煤样分别降低了416m/s、5.12MPa、1129MPa;(2)SDS水溶液与荷载的共同作用加剧了煤样的总损伤程度,表现出明显的非线性特征,煤样损伤在微观上表现为矿物质组成与结构的改变过程,宏观上表现为煤样力学强度的降低及抵抗破坏的能力减弱;(3)运用新的浸泡实验结果验证所提出的损伤演化模型,实验结果与损伤演化模型十分吻合,相关系数R^2=0.999,由此可见,该损伤演化模型具有良好的可靠性。

In order to investigate the effect of SDS aqueous solution on the physical and mechanical characteristics and the damage degree of low-rank coal,adopting sodium dodecyl sulfate(SDS) aqueous solution as organic solution, and low rank coal body(Fuxin long flame coal) as study object, through scanning electron microscope(SEM), mercury injection experiment, longitudinal wave velocity experiment and uni-axial compression experiment, the microscopic pore structure, porosity, longitudinal wave velocity, peak strength and elastic modulus of coal samples were characterized before and after soaking in SDS aqueous solution;the variation pattern of physical and mechanical properties of coal samples subjected to action of SDS aqueous solution was analyzed with the variation of immersion temperature;the damage evolution model of loaded coal sample subjected to action of SDS aqueous solution was established, and the damage mechanism of coal sample was discussed. Results show that(1) After immersion in SDS aqueous solution, the micro pore distribution is not uniform, the total porosity of coal samples increases with the increase of soaking temperature;when temperature is 55℃, the total porosity of coal samples is 57%, which is increased by 46% compared with the total porosity of raw coal sample;the longitudinal wave velocity, peak intensity and elastic modulus of coal samples decline with the increase of soaking temperature, the longitudinal wave velocity, peak intensity and elastic modulus are 571 m/s, 6.73 MPa, 356 MPa, respectively, compared with the raw coal sample were reduced by 416 m/s, 5.12 MPa, 1129 MPa;(2) The combination of SDS aqueous solution and load that intensification the total damage degree of coal samples,showing a distinct non-linear characteristic,the damage of coal samples is microscopic manifestation of the change process of mineral composition and structure, and the macroscopic manifestation is the decrease of the mechanical strength of coal samples and the weakening of resistance to damage.(3) Using the results of new immersion experimental to verify the damage evolution model,the experimental results are in good agreement with the damage evolution model,correlation coefficient is 0.9999. It can be seen that the damage evolution model has good reliability.