含顺层断续节理岩质边坡地震作用下的破坏模式与动力响应研究

Study on failure mode and dynamic response of rock slope with non-persistent joint under earthquake

基于二维颗粒流软件PFC^(2D)的人工合成岩体技术(SRM),研究了岩桥倾角和节理间距不同组合形式的含顺层断续节理岩质边坡在地震作用下的破坏模式与动力响应规律。研究结果显示:在地震动力作用下,含单潜在滑动面的顺层断续节理岩质边坡呈现出滑移-倾倒的混合破坏特征,含多潜在滑动面的顺层断续节理岩质边坡则主要发生倾倒破坏;由顺层断续节理以及岩桥交替连接所组成的潜在滑动面是控制边坡动力稳定性的关键因素。在地震动力作用下,最靠近坡脚的岩桥段首先萌生翼裂纹,使得拉应力得到释放,随后各节理相继萌生裂纹并扩展、贯通,最终导致坡体发生阶梯状整体失稳。裂纹扩展受顺层断续节理控制,萌生裂纹中以张拉裂纹为主,且裂纹数量与输入地震波的加速度曲线具有同步性。另一方面,节理面的存在对边坡动力响应产生明显影响,沿坡表以及沿水平方向上的峰值速度、峰值位移随着岩桥倾角的增大、节理间距的减小而增大,同时节理间距和岩桥倾角对于峰值加速度(PGA)放大系数的影响范围主要集中在坡表、坡肩;沿竖直方向上,峰值位移随着岩桥倾角、节理间距的增大而减小,PGA放大系数曲线随高程变化总体呈现U型分布特征。

Based on the two-dimensional particle flow software（PFC2 D）, this paper studied the failure modes and dynamic response laws of rock slope with non-persistent joints by the combination of different dip angles of rock bridge and joint spacing under earthquake. The results showed that the bedding non-persistent jointed rock slope with single potential sliding surface present the sliding-block toppling mixed failure under the action of seismic dynamics. While the bedding non-persistent jointed rock slope with multi-potential sliding surfaces mainly present the block toppling failure. The dynamic stability of the slope was mainly controlled by the potential sliding surface composed of non-persistent joints and alternate connections of rock. Under the action of seismic dynamics, the wing crack at the rock section closest to the foot of the slope was first generated, resulting in the released tensile stress. Successively, each joint started to crack and expand, which eventually led to the step-like instability. Crack propagation was controlled by bedding non-persistent joints. Cracks are dominated by tensile cracks, and the number of cracks was synchronous with the acceleration of the input seismic waves. The existence of the joint surface had a significant impact on the dynamic response of the slope. The peak velocity and displacement along the slope surface and the horizontal direction increased with the increase of the inclination angle of the rock bridge and the decrease of the joint spacing. Meanwhile, the effects of joint spacing and rock bridge inclination on the PGA amplification factor were mainly on the slope surface and shoulder. Along the vertical direction, the peak displacement decreased with the inclination of the rock bridge and the joint spacing, and the curve of the PGA amplification factor exhibited U-shaped distribution with the elevation change.