不同围压下茅口灰岩渐进性破坏的试验研究

利用MTS815电液伺服控制刚性试验机进行不同围压下茅口灰岩三轴压缩试验,通过计算绘得相应裂隙体积应变图,分析得出裂纹起始应力、裂纹破坏应力。结果表明:随着围压的增大,应力门槛值均呈非线性增长态势,当围压超过17 MPa时,裂纹起始应力、裂纹破坏应力分别增加48.5%和20.1%,茅口灰岩延性开始增强;裂纹破坏应力为峰值强度的64%~75%,三轴压缩下茅口灰岩裂隙不稳定发展阶段较长;环向应变值随围压增大而增大,当轴力超过裂纹破坏应力进入裂隙不稳定发展阶段,环向应变增大2.7~3.2倍,用环向-轴向应力应变曲线图能较好的反映岩石应力门槛值。

Experimental study on progressive failure process of Maokou limestone under different confining pressure

Under different confining pressure,triaxial compressive strength of Maokou limestone is tested by MTS 815 test system.By calculating data,the fracture strain figure is painted and crack initiation stress and crack failure stress are obtained,it shows that: with the increase of confining pressure,three stress thresholds increase,the period of unstable crack growth is longer than uniaxial compressive strength,crack propagation is limited under confining pressure.Under the same confining pressure,circ strain is larger than axial strain,circ strain grows quickly when axial force over crack initiation stress,a sharp increase in circ strain when axial force over crack failure stress,the circ-axial stress strain curve can reflect three stress thresholds.