开挖黄土高边坡的应力路径及变形破坏机制分析

Analysis of stress path and deformation-failure mechanism of high cutting loess slope

采用室内试验与数值计算相结合的方法研究开挖形成的黄土高边坡的稳定性及破坏机制。以甘肃环县华能电厂人工高边坡为例,采用线弹性有限元模拟分级开挖过程中潜在破坏面上的应力路径,在边坡上取代表性土样,参考此应力路径做天然含水率和饱和含水率下的三轴试验。依据试验所得强度参数,建立不同开挖坡比下的弹塑性有限元模型,计算各开挖阶段潜在滑动面上土体的应力状态,揭示边坡的破坏机制。结果表明,开挖过程中边坡潜在破坏面上土体应力路径为平均应力减小,剪应力先减小、后增大;开挖过程对潜在破坏面作用为先卸载、后加载,当开挖坡比较大时,高边坡坡肩处先发生屈服破坏,屈服范围随着开挖深度的增大逐渐向下扩展,直至形成连通的屈服面,为典型的推移式破坏模式。

This paper adopts laboratory experiments and numerical calculation to analyze the stability of high cutting loess slope.Taking the cutting slope in the site of Huanneng electrical plant,which islocated in Huanxian county, Gansu province, as an example,the linear elastic finite element method is utilized to attain the stress path of soil mass on the potential failure surface under multistage excavation. Then based on this stress path, triaxial shear tests are conducted on specimens with two moisture contents.With the strength parameters obtained from these tests, elastic-plastic finite element models against different excavation ratios are made to figure out its stress field. Afterwards comparison between the shear strength and shear stress on the slide surface reveals the mechanism of slope failure. Results show that the stress path(in p-q space) of soil on the prospective failure surface displays a trend that the mean stress p decreases with excavation while the shear stress q decreases at first then increases slowly. The effect of excavation on the potential surface changes from unloading at the beginning to loading. Failure firstly occurs at the shoulder of the high slope and then expands to lower area with the excavation process until a connecting yield surface in the slope develops. This mechanism is typical of top-driving landslide mechanism.