水平厚层状岩质边坡地震动力破坏过程颗粒流模拟

Simulation of dynamic failure process of horizontal thick-layered rock slopes using particle flow code

基于二维颗粒流软件(PFC2D)的人工合成岩体技术,研究岩桥长度和节理间距不同组合形式下的含水平断续节理厚层状岩质边坡在地震作用下的破坏模式、动力响应规律以及岩桥段应力演化特征。研究结果显示:地震动作用下,含水平断续节理厚层状岩质边坡主要发生溃散型破坏、拉裂–滑移–块体倾倒混合破坏和拉裂–水平滑移混合破坏;水平断续节理是控制边坡动力稳定性的关键因素。节理间距对边坡破坏模式起控制性作用:当节理间距较小时,易发生溃散型破坏;当节理间距较大时,易发生拉裂–滑移–块体倾倒破坏和拉裂–水平滑移混合破坏。岩桥长度和节理间距共同控制着边坡岩体破碎程度,从而控制着边坡失稳破坏时滑动面的个数,当节理间距很小或者节理间距较大、岩桥长度较小时,发生单滑动面破坏;当节理间距和岩桥长度均较大时,发生双滑动面破坏。在地震动力作用下,岩桥段首先发生破坏,随后各节理间也产生破坏并贯通。岩桥长度和节理间距对边坡动力响应均产生一定影响,随着节理间距减小、岩桥长度增大,峰值位移、峰值速度增大,对加速度PGA放大系数的影响区域集中在边坡坡表、坡脚等部位。地震作用下,含水平断续节理厚层状岩质边坡岩桥段应力演化、裂纹萌生与输入的地震波加速度具有良好的一致性。

The failure modes,dynamic response and stress evolution characteristics of the thick-layered rock slopes with the non-persistent joints in different combinations of rock-bridge lengths and joint spacing were studied based on the two-dimensional particle flow code PFC2 D. The results show that the main failure modes of the horizontal thick-layered rock slopes with non-persistent joint under the action of earthquake are collapse failure,tensile-sliding-block toppling failure and tensile-horizontal sliding failure. The horizontal non-persistent joint is the key factor to control the dynamic stability of the slope. The joint spacing plays a controlling role in the failure mode of the slope. When the joint spacing is small,the collapse failure is easy to occur. When the joint spacing is large,the tensile-sliding-topping failure and tensile-horizontal sliding failure occur normally. The length of rock bridge and joint spacing control the degree of rock fragmentation of slope and the number of sliding surfaces when slope fails. When the joint spacing is narrow or when the joint spacing is wide and the length of rock bridge is short,the single sliding failure occurs. When the spacing of the joint is wide and the rock bridge length is long,the double sliding surface damage occurs. Under the action of earthquake,the rock bridge section breaks down at first,and then the joints also produce damage and coalescence. The length of rock bridge and the width of joint spacing have a certain influence on dynamic response of slope. The peak displacement and peak velocity increase as the decrease of joint spacing and the increase of the length of rock bridge. The area with the PGA magnification factor influenced is concentrated at the slope toe and on the slope surface. The stress evolution in the rock-bridge of the slope has a good agreement with the acceleration of the input seismic wave.