扰动强度递增斜坡动力学演变规律的振动台试验

Shaking table experiments for simulating the dynamical evolution of slopes under increasing disturbance

"5.12"汶川大地震和"4.20"芦山地震均触发了大量的崩塌、滑坡。实震资料显示,不同地震烈度区地震触发崩塌滑坡规模的整体分布规律会发生变化。这一统计层面的认知亟待得到物理试验的验证。在自组织临界状态理论的概念框架下,开展了振动台砂堆模型试验。试验表明:输入地震波峰值加速度(PGA)为0.075g^0.125g时,落砂量与发生频率的关系可用幂律描述;PGA增加到0.15g^0.25g时,该关系服从对数正态分布;PGA增加到0.35g^0.45g时,该关系具有正态分布特征。元胞自动机模拟试验结果表明,随扰动强度增加,砂堆模型的动力学特性也经历了幂律—幂律弱化—正态分布的演变过程。按照物理学中的普适性原理,汶川、芦山地震Ⅸ度区崩塌滑坡规模与出现频率之间所呈现负幂律分布的现象,以及汶川地震Ⅺ度区所呈现的对数正态分布,可能是具有普适性意义的规律。这些认识可望为不同烈度区地震触发崩塌滑坡灾势预测提供科学依据。

A large number of landslides were triggered by the 5.12 Wenchuan earthquake and the 4.20 Lushan earthquake. The statistical results of field surveys indicate that the overall distribution pattern of the scale of earthquake-induced rockmass collapse and landslide changes with the earthquake intensity. This statistics-based result needs to be confirmed by performing laboratory physical experiments. Based on the framework of self-organized criticality（SOC） theory, shaking table tests of sandpile model under seismic excitations was conducted. The results show that for peak ground acceleration（PGA） in the range of 0.075g-0.125 g, the relation between the amount and cumulative frequency of sand follows a negative power law; for PGA between 0.15 g and 0.25 g, the relation obeys a lognormal distribution; for PGA between 0.35 g and 0.45 g, the relation turns to obey a normal distribution. Data from the cellular automata numerical simulation demonstrate that, as the earthquake intensity increases, the dynamic behaviors of sandpile model exhibit a strong power-law first, then a weak power-law, and finally a normal distribution. It is suggested here that the above-revealed distribution laws may also apply to other areas. The new recognition will provide a scientific basis for the prediction of landslides triggered by earthquake.