含水压倾斜裂隙砂岩力学与渗流特性研究

Triaxial Study on Mechanics and Seepage Characteristics of Waterbearing Inclined Fractured Sandstone

为研究带压开采过程中煤层底板断层突水问题,利用三轴应力-渗流耦合试验系统对45°倾斜裂隙砂岩进行0、0.5、1、1.5、2 MPa裂隙水压条件下的三轴压缩渗流试验,研究不同水压条件下裂隙岩体力学特性与渗流特性的变化规律。结果表明:不同水压作用下,裂隙砂岩在三轴压缩下发生的破坏均为剪切滑移破坏,试件经历了裂隙压密、弹性变形、塑性破坏、剪切错动、残余强度等阶段;水压作用更容易造成试样发生剪切滑移,并且水压对岩体强度具有弱化作用,当水压从0增加到2 MPa,试件的三轴抗压强度从32.82 MPa降低为13.54 MPa,降幅58.74%。拟合分析表明,试件的弹性模量、峰值强度以及残余强度均随着水压的增大近似线性减小。裂隙渗流方面,渗透率随着水压的增大而增大;在峰前变形阶段,渗透率随着应变的增加呈指数函数关系递减;应力达到峰值强度后试件逐渐发生剪切错动,渗透率急剧增加;到残余强度阶段,渗透率发生微小波动但基本保持稳定。

In order to study the problem of coal seam floor fault water inrush in the process of mining with pressure, used the triaxial stress-seepage coupling test system to carry out triaxial compression seepage tests on 45° inclined fractured sandstones under the condition of 0,0.5,1,1.5 and 2 MPa fracture water pressure and revealed the variation law of mechanical and seepage characteristics of fractured rock mass under different water pressure conditions. The test shows us that: the failure of 45°inclined fissure sandstones under triaxial compression under different water pressure are shear slip failure;alll specimens have experienced the stages of crack compaction, elastic deformation, plastic failure, shear dislocation, residual strength and so on;and the shear slip is more likely to occur under the action of water pressure and the strength of rock mass is weakened by water pressure, when the water pressure increased from 0 to 2 MPa, the peak triaxial compressive strength of the specimen changed from 32.82 MPa to 13.54 MPa, with a decrease of 58.74%. The fitting analysis found that the elastic modulus, peak strength and residual strength decrease linearly with the increase of water pressure. In the aspect of fracture seepage, the permeability increases with increasing water pressure;in the pre-peak deformation stage the permeability decreases exponentially with the increase of strain;after the stress reaches the peak strength, the specimen shear dislocation occurs gradually and the permeability increases dramatically;until the residual strength stage the permeability fluctuates slightly but basically remains stable.