渗透水压下孔洞裂隙砂岩断裂破坏试验研究

Experimental study of the fracture failure of sandstone containing hole and fissure under seepage water pressure

为研究渗透水压作用下裂隙岩石断裂破坏的力学机理,制作了含不同裂隙倾角的中心孔洞裂隙砂岩试件,研制了渗透水压加压装置,并结合声发射系统进行有渗透水压作用和无渗透水压作用的单轴压缩试验.研究结果表明:声发射特性揭示了试件加载过程中微裂隙压密、起裂、扩展和贯通破坏的4个阶段;渗透水压对试件的力学特性影响显著,试件的峰值强度明显低于无渗透水压作用的试件,降低程度最大超过20%,同时对应的峰值应变显著增加;渗透水压作用下的试件典型破坏特征随裂隙倾角的变化规律表现为:较小裂隙倾角[0°,30°)的试件破坏模式主要以拉伸破坏为主;裂隙倾角[30°,60°)的试件发生剪刀破坏;较大裂隙倾角[60°,75°]的试件更容易发生拉剪混合破坏.

In order to investigate the failure mechanism of fractured rock under seepage water pressure,sandstone specimens which contain center holes and fissures with different crack dip angles were made,and the seepage pressure loading device was also developed.Combining acoustic emission system,uniaxial compression experiments with seepage water pressure and without seepage water pressure were also carried out respectively.The results reveal that acoustic emission characteristics show the four stages of microfissure:compaction,crack initiation,crack propagation and transfixion failure.Moreover,seepage water pressure has a significant effect on rock mechanical properties.Obviously,the peak strengths of sandstone specimens with seepage water pressure is lower than those of the specimens without seepage water pressure,and the maximum degree of reduction is more than 20%.Meanwhile,the peak strains of sandstone specimens with seepage water pressure increase significantly.In addition,the typical failure characteristics of sandstone specimens under seepage water pressure are found that the main failure modes of sandstone specimens with fissure angle interval varing from [0°,30°)to[30°,60°)and to[60°,75°]are tensile failure,shear failure and tensile-shear mixed failure,respectively.