【摘要】 针对汶川地震Ⅹ度和Ⅺ度烈度区崩塌滑坡面积与累计频率统计关系呈现不同分布规律的现象,开展了地震峰值加速度从0.075~0.450g的6组振动台沙堆模型实验.实验重现了随振动强度增加,落沙量与累计频率从幂律分布-对数正态分布-正态分布依次转变的现象.数学分析表明,变异系数的减小,是这3种概型依次转变的原因.根据实验观察,随扰动递增沙堆表面颗粒行为呈现不同响应模式:微振动时颗粒活动性消失的概率与活动性分叉的概率在总体上平衡,当颗粒间近邻的相互作用导致连锁反应时才能发生大规模落沙事件,具有最大的不确定性.强振动时大部分颗粒就能独立启动,大规模落沙成为必然事件.据此提出,落沙规模由自组织控制的颗粒链式反应过程,向外力控制的颗粒独立下落过程的转化是导致变异系数减小的物理机制.根据以上认识,随地震烈度增加,汶川地震触发的崩塌滑坡规模与累计频率依次服从幂律分布-对数正态分布的现象,可能是具有普适性意义的规律.更多还原

【Abstract】 According to the phenomenon of statistical relationships showing different distributions,between the area and cumulative frequency of landslides in Ⅹ,Ⅺ seismic intensity of Ms 8.0 Wenchuan earthquake,6sandpile model tests under seismic were conducted with the increase of seismic peak ground acceleration ranging from 0.075 g to 0.450 g.The phenomenon of statistical relationships was reproduced by the tests between the amount and cumulative frequency of sand changing from power-law distribution to lognormal distribution,then to normal distribution,with increase of seismic loading.By mathematical analysis,the decrease of the coefficient of variation is the cause of probability distribution shift between power-law,lognormal distribution and normal distribution.Observed through experiments,the performance of grains on the surface of sandpile will show different models with the increase of seismic loading.Under weak vibration,the probability that the activity will die is overall balanced with the probability that the activity will branch.A large-scale collapse occurs when there is a chain interaction between neighboring grains.It has the greatest uncertainty.Under strong vibration,most grains start independently.A large-scale collapse becomes a certain event.Therefore,the scale of collapse is transformed from the chain reaction of unstable grains triggered by self-organized effect to the independent falling of unstable grains triggered by vibrating force effect,which is the physical mechanism of the reducing of Cv.According to the above realization,the phenomenon of the relation between area and cumulative frequency changing from power-law distribution to lognormal distribution with the increase of seismic intensity of Ms 8.0Wenchuan earthquake may be universal.更多还原