循环冲击下风化花岗岩渗透性演化规律

针对低渗透离子型稀土矿体回采效率低的缺点,提出利用爆炸应力波改变岩体内部孔隙结构进而提高渗透性的设想,并通过试验进行验证。选取赣南某离子型稀土矿弱风化层花岗岩为研究对象,利用改进的SHPB装置进行等速循环冲击,结合GDS-VIS三轴渗流试验,分析风化花岗岩循环冲击后的破坏模式,并研究有效孔隙度对循环动荷载前后岩石渗透性变化规律的影响。研究结果表明:随着冲击次数的增加,风化花岗岩抗冲能力逐渐减弱,其破碎程度与冲击速度呈正相关;冲击速度为4 m/s和5 m/s的等速循环冲击会使风化花岗岩渗透性呈现先减后增的趋势,而冲击速度为6 m/s的等速循环冲击会使风化花岗岩渗透性持续增大至岩样损坏;岩体渗透性受其有效孔隙度的影响,随有效孔隙度的增大整体呈现上升趋势,同时风化花岗岩初始有效孔隙度越大,冲击后其内部孔隙结构更易发生改变,后续循环冲击荷载下增渗效果更明显。

Evolution law of permeability of weathered granite under cyclic impact

Aiming at the shortcomings of low permeability ionic rare earth mine,the idea of using explosive stress waves to change the internal pore structure of rock mass and improve permeability is proposed.The weak weathered layer granite of an ionic rare earth mine in southern Jiangxi was selected as the research object The improved SHPB device was used for constant-speed cyclic impact Combined with the GDS-VIS triaxial seepage test,the failure mode of weathered granite after cyclic impact was analyzed,and effective pores were studied The influence of degree on the change of rock permeability before and after cyclic dynamic loading.The results show that with the increase of the number of impacts,the impact resistance of weathered granite is gradually weakened,and the degree of fracture is positively correlated with the impact velocity.The impact velocity are 4 m/s and 5 m/s constant velocity cyclic impact will cause the permeability of weathered granite to decrease first,the trend of post-increasing;and the impact velocity is 6 m/s constant-speed cyclic shock will increase the permeability of weathered granite to the damage of rock sample.The permeability of rock mass is affected by its effective porosity and it will increase with the increase of effective porosity.At the same time,the initial effective porosity of weathered granite is larger,and the internal pore structure is more likely to change after impact.The effect of subsequent seepage impact load is more obvious.