三轴应力对单裂隙砂岩渗流特性的影响试验研究

Experimental investigation on the influence of triaxial stress on seepage characteristics of sandstone with single fissure

针对渗流作用下裂隙岩体的失稳机制复杂、难以完全揭示的问题,文章开展了不同裂隙倾角单裂隙砂岩的渗流试验,从力学特性、能量耗散规律和渗透特性三个方面分析砂岩破坏特性,并探讨能量耗散过程对渗流特性的影响规律。结果表明:不同裂隙倾角砂岩的偏应力、应变能、渗透率随应变的演化过程基本一致,而不同加载阶段的变化规律差异性明显。在裂隙非水平和竖直情况下,裂隙倾角越大,脆性特征越弱,越难破坏;而对于水平和竖直裂隙而言,水平裂隙尖端的应力集中强于竖直裂隙,脆性特征更显著。此外,单裂隙砂岩的渗透率与应力的关系同样符合Louis负指数方程。不同裂隙倾角砂岩的能量耗散过程对渗流特性的影响规律大致相同,耗散能的增加均可增大渗透率,但在加载初期和末期,能量耗散反而会降低渗透率。

The failure mechanism of fissured rock under seepage is complex and difficult to be fully revealed.Hence,the seepage tests of single-fissured sandstone with different inclination angles of fissure were carried out,and the failure characteristics were analyzed from three aspects,namely mechanical properties,energy dissipation and permeability features.Finally,the influence of energy dissipation on seepage characteristics was discussed.The results show that the evolution processes of deviatoric stress,strain energy and permeability with strain in sandstone are basically consistent,while the variation processes at different loading stages are significantly different.In the case of non-horizontal or nonvertical fissure,the larger the inclination angle of fissure is,the weaker the brittle characteristics are,and the more difficult the failure shall be.Additionally,for the horizontal and vertical fissures,the stress concentration at the tip of horizontal fissure is larger than that of vertical fissure,and the brittle characteristics are more obvious.Moreover,the relationship between permeability and stress of single-fissured sandstone also conforms to the Louis negative exponential equation.The influences of energy dissipation on seepage characteristics for sandstone with different inclination angles of fissure are roughly the same(that is,the increase of dissipation energy can increase the permeability),but at the early and late stages of loading,the energy dissipation will reduce the permeability.