摘要
针对220kV盐津变电所开挖边坡,通过调查地质条件、分析变形迹象、查明岩土体的应力–应变特性及数值模拟求证等方法,发现影响边坡稳定的不利因素主要是凹状地形地貌、不良地质结构和地下水,指出该边坡整体上为开挖造成的坡体中前部牵引变形破坏,易软化泥岩控制着边坡的整体稳定性。边坡具体变形机制为:(1)场地开挖形成临空面,坡脚因应力集中在重力作用下发生小规模坍塌;(2)开挖后阻滑力降低、剪应力增大,发生剪切变形,原已被地下水软化的泥岩因剪切变形的发展导致抗剪强度再次降低,同时受重力牵引,坡体前缘出现裂缝;(3)受不利动、静水压力作用、坡面临空效应及软化泥岩的控制作用,覆盖层中部拉剪破坏,然后覆盖层中前部随下伏全～强风化泥岩滑动而协同变形。研究变形机制的方法给今后类似研究提供了借鉴意义,并且该实例表明在工程中应重视泥岩的软化特性。
Focused on a cutting slope on 220 kV Yanjin Transformer Substation,the study is carried out to find its movement characters. Through site investigation,deformation investigation and analysis,laboratory test,stress-strain behavior analysis and numerical modelling,three factors are suggested as follows:(1) excavation provides enough opportunity movement;(2) the strength of intensely and completely decomposed mudstone decreases evidently for slaking,softening and argillation in water,and the completely decomposed mudstone is strain softening;(3) V-shaped topography could provide channel for the ground water,and induce adverse hydrodynamic and hydrostatic water pressure. The deformation of cutting slope is retrogressively trigged by excavation,and the weak mudstone controls the slope stability. Slope deformation can be classified into four stages over time:(1) at the first stage,the elastic deformation adjacent to the cutting surface is released due to unloading during excavation;(2) at the second stage,when excavation is almost completed,the slope toe fails because of gravity and concentrated stress induced by excavation;(3) at the third stage,when excavation is completed,cracks appear at crown,and the shear strength of mudstone,which is reduced by groundwater,decreases further due to the increase of shear strain triggered by excavation;and (4) finally,the mid part of the over-layer is tensilely cracked,and the over-laver moves accompanying the slide of underlain mudstone induced by hydrodynamic and hydrostatic pressure,gravity,and dominating action of the softened mudstone. This study suggests that more attention should be paid to the mudstone in the future engineering for its softening characters,and the way of deformation mechanism investigation provides some suggestions for the similar studies.
出处
《岩石力学与工程学报》
EI
CAS
CSCD
北大核心
2008年第S1期2807-2813,共7页
Chinese Journal of Rock Mechanics and Engineering
关键词
边坡工程
开挖边坡
变形机制
控制作用
牵引变形
泥岩
应变软化
slope engineering
cutting slope
deformation mechanism
dominating action
retrogressive deformation
mudstone
strain softening
