【摘要】 深埋地下工程的开挖导致隧洞径向方向围岩内部存在梯度应力。基于此,本文研究了梯度应力条件下围岩在不同轴向应力作用下的力学响应和断裂特征,并且在试验过程中,采用声发射(AE)系统采集了岩石破裂声发射信号。结果表明:梯度应力作用下,轴向应力对砂岩力学响应的影响与经典真三轴压缩试验结果相似。当轴向应力小于临界强度时,随着轴向应力的增大,砂岩特征应力逐渐增大,显著提高了砂岩承载能力。但是当轴向应力超过临界强度时,高轴向应力的加载过程会导致砂岩产生局部破坏,引起砂岩特征应力的降低,此时,砂岩内部仅有部分裂纹合并贯通,形成斜向宏观裂隙,但并未贯穿整个砂岩试样。声发射特征信号分析结果表明,随着轴向应力的增大,砂岩在破坏过程中产生的剪切裂纹比例逐渐减小,拉伸裂纹在整个新生裂纹中占据主导地位,并控制着砂岩的破坏。这反映了在梯度应力条件下,随着轴向应力的增大,围岩内部因微观拉伸裂纹合并而形成宏观剪切裂纹的活动会受到明显的抑制作用。更多还原

【Abstract】 The excavation of deep underground engineering leads to a gradient stress within surrounding rocks in the radial direction of the tunnel. In this study, we investigated the mechanical response and fracture characteristics of rocks subjected to gradient stress under different axis stresses. During the experimental process, an acoustic emission(AE) system was used to capture the AE signals. The obtained results showed that the influence of axis stress on mechanical response of rock subjected to gradient stress is similar to the test results obtained by classical true triaxial compression tests. When the axis stress is below the critical strength, as the axis stress increases, the characteristic stress increases, resulting in an increase in rock strength. However, once the axis stress exceeds the critical strength, localized failure occurs during the application of the axis stress, leading to a decrease in rock strength. In this case, only part of the cracks coalesces to form oblique macro cracks that do not penetrate the entire rock specimen. The AE signals indicate that the proportion of shear cracks decreases as the axis stress increases. The axis stress significantly suppresses the formation of macro shear cracks resulting from the coalescence of micro tensile cracks.更多还原