地震作用下边坡动力响应的数值模拟研究

Numerical simulation of earthquake effects on rock slope

汶川地震中在硬岩、次硬岩区域出现的一些大规模斜坡破坏现象超出了以往对地震作用下边坡稳定性问题的认识。本文使用FEPG有限元程序分析了水平和垂直2种不同加载方式作用下,经过不同的震动持续时间,不含裂隙岩质坡体内部的应力场和位移场的变化规律。得出的结论认为,在输入震动振幅为0.1m的加载作用下,岩质边坡内部的应力和位移均出现极值:在边坡的顶部及坡面上最大拉伸应力值大于100MPa,超过了花岗岩、灰岩等硬岩、次硬岩的抗拉强度,可能使岩体产生破裂发生崩塌、滑坡灾害。研究结果还表明,与水平方向振动加载相比,垂直方向振动加载产生的响应结果要大,边坡顶端一点的在垂直方向位移的峰值达到0.43m,远远超过了输入的震动振幅,垂直方向的震动是引起边坡的不稳定的主要因素。此外,震动持续时间越长,造成的变形和破坏就越大。

During 5.12 Wenchuan Earthquake,there were lots of huge landslides and collapses occurred in hard rock areas.This uncommon phenomenon is beyond our knowledge.This paper discussed the different patterns of stress and displacement distributions within a perfect slope when it is subject to horizontal and vertical vibrational loads with various loading time.The analyses were performed using FEPG software.It is found that,both the stress and the displacement appear to reach their peak values when the amplitude of vibration load is 0.1m.The maximum tensile stress at the top of a slope is bigger than around 100MPa which exceeds the anti-tensile limit of typical hard rocks such as granite,and so on.As a result,the hard rock mass breaks and landslide occurs.The study results also show that vertical vibrational loads would cause bigger stress and displacement peaks than horizontal vibrational loads. Under vertical vibrational load,maximum vertical displacement reached 0.43m which is much bigger than the amplitude of the original load.Consequently vertical vibration might become the main factor that causes slope failures.Moreover,longer loading time will cause more serious deformation and damage.