地震作用下节理岩质边坡稳定性影响因素研究

A Study on the Influencing Factors of Joint Rock Slope Stability under Earthquake Activity

摘要:

汶川地震灾害调查表明,在基岩山区地震滑塌主要发育在局部强度相对较大、节理较发育的厚层或块状岩体中。以岩石中含两组节理的岩质边坡为例,输入实际的地震记录,采用离散单元法进行数值模拟,分别探讨坡高、地震烈度、坡角及节理倾角组合对节理岩质边坡稳定性的影响。结果表明:地震作用下坡体中质点的加速度、速度具有高程放大效应;节理岩质边坡稳定性随着坡高、坡角和地震烈度的增加而降低;两组节理不同组合的岩质边坡,其稳定性变化较为复杂,受节理倾角与坡角的关系、节理的倾向、两组节理之间夹角等因素的影响。节理岩质边坡在地震作用下是受拉区逐渐向受剪区扩展而最终导致边坡失稳破坏,是受拉和受剪的复合破坏。上述初步结论为评价山区节理较发育的岩质边坡在地震作用下的稳定性提供一定的依据。

Abstract:

Disaster survey results of the Wenchuan earthquake show that seismic landslides mainly develop within thick-bedded or massive rock,in which local intensity is relatively large and joints are obvious.Although seismic landslides differ markedly from those induced by rainfall and other factors,this topic has not drawn sufficient attention.Moreover,numerical analysis methods of finite element and finite difference,both based on the assumption of continuous media and small deformation,are used in previous studies of slope stability.However,some limitations exist in dynamic analysis of large deformations of rock slope due to a large number of interfaces of discontinuity. To overcome those problems,the dynamic response of joint rock slope in this thesis is simulated by means of the discrete element numerical simulation,particularly deformation characteristics,failure mechanism,and influencing factors of slope stability.Here,a rock slope containing two groups of joints is used as the research object.In addition,discrete element numerical simulation is conducted,and actual earthquake records are input to simulate a large number of cases.The influencing factors of the joint rock slope stability are respectively explored under various conditions of slope height,seismic intensity,slope angle,and joint angle.Topographic amplification effects are observed from both acceleration and velocity of the monitoring points of the slope.Joint rock slope stability is reduced with slope height,slope angle,and seismic intensity.In addition,the stability of the rock slope that contains two groups of joints is complex and is influenced by other factors including joint inclination,slope angle,the tendency of joints,and the angle between two group joints.The regions of tension failure are gradually extended to the shear zone and eventually lead to slope instability and failure,compounded by tensile and shear failure.This study provides a reference for evaluation of the rock slope and joints stability under seismic loading in mountainous areas.