不同倾角下双平行节理岩体力学性能及裂纹演化规律的试验研究

    Experimental study on mechanical properties and crack evolution of rock masses with double parallel joints under different inclination angles

    • 摘要: 为揭示节理倾角对双平行节理岩体力学性能与裂纹演化规律的影响,制备30°、45°、60°、75°的双平行节理试样,通过开展单轴压缩试验,结合CCD相机、声发射仪对试样破坏全过程进行监测,研究不同平行节理倾角对试样力学性能、最大主应变演化过程、裂纹演化规律及声发射响应的影响。研究结果表明:随着节理倾角增大,试样平均峰值强度逐渐提高,75°试样较30°试样提升37.7%;各试样应力下降均呈现“先波动式、后台阶式”特征;试样应变集中区域率先出现在节理尖端并向外扩展,随着倾角增大,试样最终破坏时下部节理高应变区域比上部节理的发育更充分;各试样裂纹均以张拉裂纹为主,随着倾角的增大,裂纹率先起裂位置从下部节理转向上部节理,裂纹最终显著破裂区域从上部节理转向下部节理;在破坏阶段,试样的声发射事件率随应力跌落突增;RA-AF表现为低RA值、高AF值特征,进一步证实试样以张拉破坏为主,与试样宏观裂纹一致。研究成果揭示了双平行节理岩石单轴压缩破坏应力及应变演化规律,并为类似研究提供实验参考。

       

      Abstract: To investigate the influence of joint dip angle on the mechanical properties and crack evolution of rock masses with double parallel joints, samples with joint dip angles of 30°, 45°, 60°, and 75° are prepared. Uniaxial compression tests are conducted, and the entire failure process is monitored using a CCD camera and an acoustic emission (AE) system. The effects of varying dip angles on mechanical performance, maximum principal strain evolution, crack propagation patterns, and AE response were analyzed. The results indicate that the average peak strength of the samples increases with the dip angle, showing a 37.7% enhancement in the 75° sample compared to the 30° sample. The post-peak stress drop exhibits a characteristic pattern of “initial fluctuation followed by stepwise decline”. Strain concentration initiates at the joint tips and propagates outward; at failure, the high-strain zone is more fully developed around the lower joint than the upper one as the dip angle increases. Failure is dominated by tensile cracks. With increasing dip angle, the initial crack initiation site shifts from the lower to the upper joint, while the primary region of final significant rupture shifts conversely from the upper to the lower joint. During the failure stage, the AE event rate surges coincident with the stress drop. The RA-AF analysis reveals low RA and high AF values, further confirming a tensile failure mechanism consistent with macroscopic observations. These findings reveal the stress and strain evolution laws of double parallel jointed rocks under uniaxial compression and provide experimental references for similar studies.

       

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