老滑坡路段路堑开挖与超前支护效果

为防止老滑坡路段路堑开挖过程中出现路堑边坡失稳的问题，以在建某高速公路老滑坡段路堑失稳边坡为例，借助数值分析，进行了老滑坡路段路堑开挖与超前支护效果研究。结果表明：1）一般宽平台开挖模式能提高边坡的整体稳定性；然而，对于存在具有膨胀性质滑带土的牵引式老滑坡，坡脚采用宽平台刷坡减重不利于路堑边坡的稳定，必须要采取超前支护，如锚索、抗滑桩等，必要时要紧急采取清方卸载措施。2）锚索超前支护能够有效抑制边坡变形，需采用有效措施提高设置在坡脚处锚索的抗拉强度，如施加预应力等。3）抗滑桩超前支护应注意桩位、桩长、桩距的优化设计。建议抗滑桩采用锚拉，对桩前坡体中的滑带进行超前注浆，有必要沿老滑坡主滑方向布置多排抗滑桩，或采用h型桩体设计。

Excavation and Advance Support Effect of Old Landslide

In order to solve the problem of cutting slope instability caused by reactivation of old landslides,taking a instable cutting slope along with expressway as an example, the cutting excavation and the effect of advance support was studied with the help of numerical analysis. The main conclusions and suggestions are as follows:1) The overall stability of the slope can be improved by the wide platform excavation mode. However, the wide platform excavation mode is not conducive to the stability of the old traction landslide with the existence of weak structural plane, weak interlayer and sliding zone with expansion properties. Advance support must be adopted, such as anchor rope, anti-slide pile and so on, and unloading measures also should be taken urgently when necessary. 2) Anchor cable pre support can effectively restrain the cutting deformation, so effective measures should be taken to improve the tensile strength of anchor, which is arranged at slope toe or to apply pre-stressing force. 3) In advance anti-slide pile supporting, attention should be paid to the design optimization of pile position, pile length and pile spacing. Anti-slide pile should be anchored by bolts, and the sliding zone in front of the pile should be used for pre grouting; and it is necessary to arrange multi row anti-slide piles along the main sliding direction of the old landslide, or to adopt the h-type pile design.