不同围压作用下煤-岩组合体破坏行为及强度特征

通过MTS815试验机对钱家营矿煤-岩组合体进行常规三轴压缩试验。研究表明:围压作用下煤-岩组合体压密阶段较短,具有明显的线弹性及塑性屈服阶段,且随着围压的增大,峰后延性特征明显;根据峰值应变、弹性模量、破断角、强度的变化规律,10~15 MPa为组合体变形减缓的临界区间;煤样破坏主要以单斜面剪切破坏为主,并且个别岩体部分产生与煤样一致的剪切面,破断角处于14.1°~38.8°,均值为26.84°与理论破断角28.31°相差不大;随着围压的增大,残余强度有增高趋势,岩石强度衰减系数与之相反。围压从0~5 MPa,强度衰减系数降幅最大,体现出对围压的敏感性,随后围压继续升高,强度衰减系数呈线性递减;利用Hoek-Brown和广义HoekBrown准则对煤-岩组合体强度进行分析,讨论了适用于煤-岩组合体的参数m,s值。

Failure behavior and strength characteristics of coal-rock combined body under different confining pressures

A testing system MTS 815 was used to carry out triaxial compression test for Qianjiaying coal-rock combined body.The results show that the consolidation stage is shorter and it apparently has a linear elastic stage and a plastic yield stage under the influence of confining pressure.Ductility of post-peak stage is much more apparent with the increase of confining pressure.Based on the change laws of peak strain,elastic modulus,rupture angle and strength,the threshold confining pressure of deformation is 10-15 MPa.The failure mode of coal body is mainly shear failure,and some rock bodies have the same failure mode with coal body.The rupture angle is within the range of 14.1°-38.8° and its average value is 26.84° which has little difference with 28.31° calculated using Coulomb strength criterion.Residual strength has an increasing trend with the increase of confining pressure while rock Ds has the opposite trend.From 0 to 5 MPa,the decreasing range of Ds is the largest which reflects the sensibility to confining pressure.Then,with the increase of confining pressure,Ds shows a linear decrease.Finally,the values of m,s in Hoek-Brown and generalized Hoek-Brown failure criterion are discussed.