Study on failure mechanical characteristics and damage constitutive model of sandstone with different numbers of holes

Abstract The existence of holes in rock is one of the key factors for the instability of underground rock mass engineering. Combined with acoustic emission equipment, uniaxial compression tests of rock specimens with different numbers of holes in the rock were carried out. The results show that with the number of holes increases, the value of peak strength and elastic modulus of the rock decrease. The acoustic emission (AE) counts gone through stable, slow increase, a sudden increase and towards zero four stages and there are corresponding to the initial compaction stage, elastic stages, strain hardening stage and post-peak strain softening stage of the stress-strain curves approximately. Based on the AE events, damage variables of rocks were obtained. The damage evolution process of rock can also be divided into three parts, including stable damage stage, slowly increasing damage stage and sharply increasing damage stage. According to Duncan model, the damage variable is introduced to obtain the rock damage constitutive model. No matter it is the pre-peak initial compaction stage, the linear elasticity stage, the strain hardening stage or the post-peak strain softening stage, the fitting curves are in good agreement with the test curves. It also illustrates the rationality of the damage constitutive model.

摘要 岩石内部孔洞的存在是地下岩体工程失稳的关键影响因素之一。结合声发射（Acoustic Emission，AE）设备，开展了含不同孔洞数量的岩石试样单轴压缩试验。试验结果表明，随着孔洞数量增加，岩石的峰值强度与弹性模量均呈下降趋势。声发射计数依次经历稳定、缓慢增长、急剧增长并趋近于零四个阶段，该过程大致对应应力-应变曲线的初始压密阶段、弹性阶段、应变硬化阶段以及峰后应变软化阶段。基于声发射事件，得到了岩石的损伤变量；岩石的损伤演化过程同样可划分为三个阶段，分别为稳定损伤阶段、缓慢增长损伤阶段与急剧增长损伤阶段。基于邓肯模型（Duncan model），引入损伤变量构建岩石损伤本构模型。无论是峰前初始压密阶段、线弹性阶段、应变硬化阶段还是峰后应变软化阶段，拟合曲线均与试验曲线吻合良好，这也验证了该损伤本构模型的合理性。