节理对岩体强度变形特性影响的模型实验

Contrastive model test for joint influence on strength and deformation of rock masses

采用模型试验研究节理对岩体强度变形特性的影响。设计150mm×150mm×150mm尺寸的3组模型试验,在不同的正压力下,分别对完整岩块、贯通节理岩体和断续节理岩体进行中型剪切试验。研究结果表明:岩体以脆性破坏为主,主要有4种典型的破坏方式,破坏形态与节理的排列方式、贯通性以及应力状态等因素密切相关;完整岩块、贯通节理岩体和断续节理岩体变形破坏发展过程具有不同的分段特征:完整岩块曲线主要经历剪缩错动、线弹性增长、破坏和残余强度4个阶段;贯通节理岩体曲线主要经历线弹性增长区、过渡区和滑移破坏区3个阶段;断续节理岩体曲线主要经历线弹性增长、节理面错动、次生裂纹起裂稳态扩展、节理面贯通破坏和残余强度5个阶段。断续节理岩体摩尔库仑曲线分别以完整岩块和贯通节理岩体的破坏包络线为上界和下界,可以通过地质力学分析缩小带宽,估算断续节理岩体的强度。

Model tests were adopted to study the influence of joints on rock masses. Three sets of model tests with the scale of 50 cm× 50 cm× 50 cm were designed to study the strength and deformation properties of intact rock, across jointed rock mass and intermittent jointed rock mass. The evolvement processes of shear stress, shear displacement, normal stress and normal displacement were monitored using rigid servo test machine. The results show that the failure modes quietly depends on the joint distribution, connectivity and stress states. There are four typical failure modes in the test, and brittle failures are the main failure mode, different failure developing stages are found in the intact rock, across jointed rock mass and intermittent jointed rock mass. There are four typical stages in the stress strain curve of intact rock, namely shear contraction stage, linear elastic stage, failure stage and residual strength stage. There are three typical stages in the across jointed rock mass, namely linear elastic stage, transition zone and sliding failure stage. Correspondingly, five typical stages are found in the intermittent jointed rock mass, namely linear elastic stage, sliding of joint, steady growth of post-crack, joint coalescence failure, and residual strength. According to strength analysis, the failure envelopes of intact rock and across jointed rock mass are the upper bound and lower bound, respectively. The strength of intermittent jointed rock mass can be evaluated by reducing the bandwidth of the failure envelope with geo-mechanics analysis.