基于离散元技术的软硬互层斜坡动力响应及失稳机理研究

为研究不同岩层倾角陡倾顺层软硬互层斜坡在地震作用下的动力响应及失稳机理,以汶川地震中干磨坊滑坡和水磨沟滑坡为原型,结合三维离散元技术开展两种软硬互层斜坡对比分析。动力响应分析结果表明:在相同地震荷载作用下,陡倾软硬互层60°斜坡模型的PGA(峰值地面加速度)放大系数随着高程的增加表现出非线性增长,在坡顶动力响应最为强烈;陡倾软硬互层80°斜坡模型PGA放大系数随着高程的增加表现出先增大后减小再增大的节律性变化,在坡高1/3处和坡肩部位动力响应最为强烈。失稳机理分析结果显示,在地震荷载作用下:陡倾软硬互层60°斜坡模型发生滑移-弯曲式溃滑,斜坡的破坏流程机制分为四个阶段,即①裂缝扩展-层间错动阶段、②坡脚岩体弯曲隆起阶段、③上部岩体横向滑移阶段、④弯曲剪断-整体失稳阶段;陡倾软硬互层80°斜坡模型发生滑移-下部弯曲-上部倾倒式破坏,斜坡的破坏流程机制分为四个阶段,即①微裂隙扩展阶段、②层间错动-局部裂隙贯通阶段、③下部岩体弯曲阶段、④上部岩体倾倒破坏阶段。

Discrete element technique-based study on dynamic response and instability mechanism of soft and hard interbedded slope

In order to study the dynamic response and instability mechanism of steep dip bedding soft and hard interbedded slope with different dip angles under seismic action，a comparative analysis on two kinds of soft and hard interbedded slopes is carried out in combination with 3-D discrete element technique by taking Ganmofang landslide and Shuimogou landslide in Wenchuan Earthquake as the prototypes． The result of dynamic response analysis shows that under the same seismic load，the PGA ( peak ground acceleration) amplification coefficient of the model of 60° steep dip bedding soft and hard interbedded slope exhibits nonlinear increase along with the increase of elevation with the intensest dynamic response at the slope top，while the PGA amplification coefficient of the model of 80° steep dip bedding soft and hard interbedded slope presents a rhythmic change of increasing at first and then decreasing and again increasing along with the increase of elevation with the intensest dynamic responses at the height of 1 /3 and on the shoulder of the slope． The results of instability mechanism analysis shows that under seismic load effect， slip-bending collapse-slip occurs in the model of 60° steep dip soft and hard interbedded slope，for which the mechanism of failure process of the slope is divided into four phases，namely，① fracture propagation-interlaminar dislocation; ② bending uplift of the rock mass at the toe of slope; ③ transverse slip of upper rock mass; ④bending shear-overall instability，while slip-lower bending and upper tilting failure occurs in the model of 80° steep dip soft and hard interbedded slope，for which the mechanism of failure process of the slope is divided into four phases，namely ①microfracture propagation; ②interlaminar dislocation-local fracture penetration; ③ bending of lower rock mass． ④ toppling failure of upper rock mass.