锁固段边坡模型破坏前兆特征

为探究花岗岩锁固段边坡模型损伤破坏过程中的微震信号能量、频率分布特征及临界慢化现象，开展了花岗岩锁固段边坡模型的破坏试验研究，利用单轴加载系统对不同岩桥角度的花岗岩锁固段边坡模型进行加载，采用应变片、微震（microseismic，MS）监测系统对其加载全过程进行同步观测.试验结果表明:（1）岩桥角对边坡模型的破坏形式产生影响，当岩桥角为70°和90°时破坏形式以拉张破坏为主；当岩桥角为110°时为拉压混合破坏；当岩桥角为130°时为压剪破坏，前缘蠕滑段为锁固型边坡变形最大的部位.（2）在加载过程中，当存在微小损伤破裂时，主要以高频、低能的微震信号为主，当产生大尺度损伤破裂时会伴随着低频、高能的微震信号.（3）在锁固段边坡模型处于临界破坏状态时会出现明显的临界慢化现象，表现为微震信号的方差、自相关系数产生突增现象，且突增点所对应的时间均达到失稳时间的80%，具有较好的时效性，可将微震信号的方差、自相关系数的突增作为边坡模型的失稳破坏前兆信息.（4）能量比方法与临界慢化理论形成联合预测判据，可克服单一判据的缺点，提高预测的准确性.该研究可为突发型的岩质边坡监测预警提供可用的参考价值. 

Failure Precursory Characteristics of Slope Model with Locked Section

In order to research the energy and frequency distribution characteristics of microseismic signals and the critical slowdown phenomenon in the damage and destruction process of granite locked section slope model, the damage test study of granite locked section slope model was carried out, and the granite locked section slope model with different rock bridge angles was loaded by uniaxial loading system, simultaneous observation was carried out by strain gauges and microseismic (MS) monitoring system. The test results manifest follows: (1) the rock bridge angle affects the damage form of the slope model, when the rock bridge angle is 70° and 90°, the damage form is mainly tension damage. When the rock bridge angle is 110°, it is mixed tension and compression damage. When the rock bridge angle is 130°, it is compression-shear damage, and the leading edge creep-slip section is the largest part of the locked slope deformation. (2) In the loading process, when there is a small damage rupture, mainly high-frequency, low-energy microseismic signals are dominant, and when a large-scale damage rupture is generated, it will be accompanied by low-frequency, high-energy microseismic signals. (3) The critical slowdown phenomenon occurs when the slope model in the locked section is in the critical damage state, which is manifested by the sudden increase of the variance and autocorrelation of the microseismic signal, and the time corresponding to the sudden increase reaches 80% of the destabilization time, so it has good timeliness, and the sudden increase of the variance and autocorrelation coefficient of the microseismic signal can be taken as the precursor information of the destabilization damage of the slope model. (4) The energy ratio method and critical slowing theory form a joint prediction criterion, which can overcome the shortcomings of single criterion and improve the accuracy of prediction. This study can provide usable reference values for monitoring and early warning of rocky slopes of sudden occurrence type.