含弱层岩质边坡自振周期反演试验及数值验证

Inversion test and numerical verification on natural period of rock slope with weak layers

为了避免爆破所产生的振动波振动周期与含弱层岩质边坡自振周期产生共振效应,只有对含弱层边坡自振周期的准确估算才能够采取有效措施减小爆破振动对边坡的破坏程度。通过采用多次振动台模型试验,对边坡模型分别输入不同频率的简谐波进行激振,应用数字散斑方法对测点进行监测,根据试验结果反演含弱层岩质边坡自振周期。试验结果表明:同一边坡受不同频率振动波作用时,边坡破坏响应并不相同;当振动频率为35 Hz时,含弱层边坡发生共振,在边坡内形成拉剪破裂面并严重破坏并出现突然崩塌现象。而当振动频率为其他频率时,边坡坡顶产生一些细小的裂隙,在断层和软弱夹层附近出现较大的错动,但边坡整体稳定。由此反演该现场边坡的固有频率约为7 Hz。然后采用有限元软件模拟边坡振动台试验过程及对现场监测数据分析,也证实当振动频率为7 Hz时弱层边坡产生共振效应。振动台试验和数值计算及现场监测在边坡动力破坏特征上较好吻合。研究结果可为确定复杂结构边坡或建筑物的自振周期提供方法。

In order to avoid resonance effects between the vibration period of blasting vibration wave produced and natural period of rock slope with weak layers,a correct estimation of natural period of rock slope with weak layers enables to take effective measures to reduce the damage of blasting vibration on slope. A large-scale shaking table model test was conducted by inputting different frequencies simple harmonic waves,and monitoring the observation posts through digital speckle method. Based on the results from the test,the natural period of rock slope with weak layers was inversely calculated. The results show that the dynamical response characteristics of the slope are not the same when different frequency vibration waves applied on the same slope. The slope with weak layers resonance breakage occurs when the vibration frequency is 35 Hz. When the vibration frequency is different,small cracks occur on the top of a slope,at the same time,large movement occurs near the faults and weak layers,but the slope shows its integrity. Therefore,the first order natural frequency of the slope is about 7 Hz. In addition,the shaking table test process of slope was simulated by an finite element software with monitoring data,which also confirmed that the slope has resonances as thevibration frequency is 7 Hz. As to the characteristics of the slope dynamic failure,the shaking table model tests are well consistent with the numerical simulations,which provides a feasible method for determining the natural period of the complex structure slopes or buildings.