拉裂-滑移式黄土崩塌的形成机制及其稳定性研究

拉裂-滑移式黄土崩塌是黄土地区高速公路建设过程中常见的一种崩塌灾害。根据土体极限平衡方程,得到黄土斜坡后缘最大竖直拉张裂隙深度。引进水致弱化函数,分别建立了竖直裂隙面介质及潜在滑移面介质的本构方程。根据崩塌体能量守恒原理及尖点突变理论,建立了拉裂-滑移式黄土崩塌隐患的尖点突变模型。根据该模型,探讨了拉裂-滑移式黄土崩塌的形成机制。认为黄土斜坡开挖后,后缘形成拉张裂隙,在裂隙充水的作用下,竖直拉张裂隙的剪切模量增大,潜在滑移面的剪切模量减小,当黄土含水饱和度达到一定程度时候,系统发生突变,滑裂面形成,土体重心不断向临空面移动。其重心一旦滑出陡坡,就会产生崩塌。根据极限平衡方程,结合摩尔-库仑定律,建立了拉裂-滑移式黄土崩塌隐患体的稳定性计算公式。研究结果对黄土崩塌治理的设计与施工具有重要参考价值。

Research on formation mechanism and stability of tensile cracking-sliding loess collapse

Tensile cracking-sliding loess collapse is the most recurrent disaster in the expressway construction in loess area. The maximum vertical tension cracking depth in trailing edge of loess slope is obtained from the limiting equilibrium equation of soil; the constitutive relation between vertical fissure mass and the potential sliding surface mass is established by the water weakening function; the equation of balanced camber and cusp is formulated from the expression of total potential energy of the collapse, then the catastrophic model of cusp for tensile cracking-sliding loess collapse is established. The formation mechanism for tensile cracking-sliding loess collapse is explored based on the mode. After excavation, the tension crack in trailing edge of loess slope is formed, and then the fissure is filled with water. The water filling increases the shear modulus of vertical tension and decreases the shear modulus on the potential sliding surfaces. When the saturation degree of loess mass reaches a certain value, the slope system undergoes mutation and the sliding surface is formed; then the core of the soil body moves unceasingly to the free surface. Once the core of soil body sliding out of steep slope, collapse will be happen. Based on the limiting equilibrium equation and the Mohr- Coulomb's law, computing formula of the stability for cracking-sliding loess collapse is established. The research results will be of valuable reference for the design and construction of loess collapse control.