三向应力下岩石的强度和变形特性研究

Research on Strength and Deformation Behavior of Rock under Triaxial Compression

为探讨岩石在三向应力作用下的强度和变形破坏规律及影响因素,采用MTS815电液伺服岩石力学试验系统,分别对砂岩和灰岩进行了三轴压缩试验。基于岩石的应力应变曲线与莫尔-库伦准则,对其残余强度、抗剪强度参数和弹性模量等力学变形特性进行了研究,并分析了孔隙率对岩石各类参数的影响。结果表明:围压对岩石的破坏特征有显著影响,岩石由低围压控制下的脆性破坏逐渐转变为高围压控制下的塑性破坏;横向应变的变化规律与侧向压力作用关系不明显,岩石在峰值应力处的横向应变几乎为定值,应力刚降至残余强度时的横向应变也近似为定值;与砂岩相比,灰岩的孔隙率较低,因而内摩擦角较大,峰值强度也越高,峰值后的残余强度降低得越明显;围压对低孔隙率岩石的弹性模量影响较小,而高孔隙率岩石的弹性模量随围压增加而增大。

In order to research the strength and deformation failure rule of rock and their influence factor, thetriaxial compression tests on sandstone and limestone were carried out by making use of the MTSS15 rock mechanicsservo-controlled test system. Based on the stress-strain curve and Mohr - Coulomb criterion, the rock＇ s mechanicaldeformation parameters, such as residual strength, shear strength parameters and elastic modulus were studied. Andthe influence of porosity on rock＇ s parameters was analyzed. The results showed that confining pressure had a sig-nificant influence on thedamagecharacteristics of rock, which the rockdamage gradually transformed from brittlefailure under low confining pressure to plastic failure under high confining pressure; the relationship between trans-verse strain and lateral pressure was not obvious, and the transverse strain corresponding to the peak stress wasnearly a constant, when stress has just dropped to residual strength, the transverse strain was also nearly a con-stant; compared with the sandstone, limestone had the lower porosity, so it＇ s internal friction angle was bigger,then the peak strength was higher, and residual strength after peak strength reduced more significantly; confiningpressure had less influence on the elastic modulus of rock which was low porosity, and high porosity rock＇ s elasticmodulus increased with an increase on confining pressure.