ISSN 1003-8035 CN 11-2852/P

    孔裂隙组合缺陷砂岩蠕变破坏实验研究

    Experimental investigation of creep failure behavior of sandstone with combined pore–fissure defects

    • 摘要: 岩石内部缺陷是导致其在受载条件下发生变形破坏的重要内因。为揭示孔裂隙组合缺陷对岩石蠕变特性的影响规律,本文开展分级加载蠕变实验,重点分析孔隙位置与尺度对蠕变演化过程的影响。结合声发射与DIC数字散斑相关方法监测破裂过程。研究结果表明:(1)孔隙位置对蠕变时间具有显著影响,位于“z”位置时最短,且随孔隙直径增加呈“V”型变化;(2)岩石长期强度整体随孔隙直径增大而降低,但在“z”位置、直径为3 mm时最小。蠕变过程中累计振铃计数曲线呈阶梯式上升,并在破裂前爆发式增长;(3)破坏阶段声发射b值由波动转为下降,表现出明显的失稳前兆;(4)孔隙空间位置显著影响破裂模式,而孔隙尺度仅引起局部差异,但在直径4 mm时裂纹出现半环绕孔隙扩展。研究表明孔隙的位置与尺度共同影响岩石蠕变破坏的时间演化、强度变化及裂纹扩展模式。该研究结果为含缺陷岩体的长期强度预测、破坏模式分析及失稳前兆预测提供了重要实验依据。

       

      Abstract: Internal defects a primary intrinsic factor governing the deformation and failure of rocks under load. To elucidate the effects of pore–fissure combined defects on the creep behavior of rocks, a series of step-loading creep tests were conducted, with particular emphasis on the effects of pore location and diameter on creep evolution. The fracture process was monitored using acoustic emission (AE) and digital image correlation (DIC) techniques. The results show that: (1) pore position significantly affact creep duration, which is shortest when the pore is located at “z” position; creep duration varies in a “V-shaped” trend with increasing pore diameter. (2) the long-term strength generally decreases with larger pore diameters, reaching its minimum at the “z” position with a 3 mm diameter pore. During creep, the cumulative AE ringing exhibits a stepwise increase and undergoes an abrupt surge immediately before failure. (3) in the failure stage, the AE b-value transitions from fluctuating to a sustained decline, serving as a clear precursor to instability. (4) Pore spatial position exerts a dominant control over the macroscopic fracture pattern, whereas pore size primarily induces local variations. However, when the pore diameter reaches 4 mm, semi-enveloping crack propagation around the pore is observed. These findings demonstrate that pore position and size jointly control the temporal evolution of creep failure, long-term strength degradation, and crack propagation patterns. The results provide important experimental evidence for long-term strength prediction, failure mode analysis, and instability precursor identification in defect-containing rock masses.

       

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