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危岩体在经历地震和强降雨之后其抗滑力下降,从而导致重力作用失稳,是一种常见的破坏形式。危岩块体的失稳破坏取决于岩体结构面的状况,随着结构面的张开及黏结程度下降,危岩块体会发生失稳而崩塌,基于常规位移监测方法难以达到危岩块体监测预警的目的。而固有振动频率可以有效反映岩体的物理力学参数的变化,进而可以对其安全性做出预判。基于模型试验,在保持下滑力不变的情况下,通过固有振动频率来对滑坡内部的黏结力和摩擦力等力学指标进行分析。通过实际静摩擦力是否达到最大静摩擦力的方法来科学判识岩体的稳定情况。试验结果得出:计算的摩擦力可以有效分析岩体的安全性,并证明固有振动频率在降低至6 Hz以下,岩体开始趋于破坏。同时,得出由于摩擦力破坏后期占据抗滑力的比重逐渐升高,最高达到抗滑力的80%,从而造成破坏末期摩擦力不降反升的情况。基于固有振动频率的监测,可对岩体的损伤做出定量判断,也可评估岩体静摩擦力指标,从而实现扰动后岩体的安全评价。这种基于振动模态的岩体安全监测与损伤评价新的技术思路,将在实际工程中发挥重大作用。
Dangerous rock body after the earthquake and heavy rainfall decreased its sliding resistance, resulting in the instability of gravity, is a common form of damage. The failure of rock block depends on the condition of the rock mass. When the structural plane is open and the degree of bonding declines, the rock mass will collapse and collapses. It is difficult to reach the rock mass based on the conventional displacement monitoring method Monitoring the purpose of early warning. However, the natural vibration frequency can effectively reflect the change of physical and mechanical parameters of the rock mass, and then the safety of the rock mass can be predicted. Based on the model test, the mechanical indexes such as adhesion and friction force of the landslide are analyzed by the natural vibration frequency while keeping the sliding force constant. The stability of rock mass can be scientifically identified by whether the actual static friction reaches the maximum static friction force. The experimental results show that the calculated friction force can effectively analyze the rock mass safety and prove that the natural rock mass begins to destructive when the natural vibration frequency is reduced below 6 Hz. At the same time, it is concluded that the proportion of frictional force occupying anti-skid force gradually increases up to 80% of the anti-skid force, resulting in the situation that the frictional force at the end of destroying does not fall or rise. Based on the monitoring of the natural frequency, the damage of the rock mass can be quantitatively evaluated, and the static friction index of the rock mass can also be evaluated, so as to realize the safety evaluation of the rock mass after the disturbance. This new vibration mode-based rock mass safety monitoring and damage evaluation of new technical ideas, will play a significant role in the actual project.