高速公路路堑边坡顺层滑坡分析与治理

ANALYSIS OF BEDDING LANDSLIDE OF CUTTING SLOPE IN AN EXPRESSWAY AND ITS TREATMENT

潭邵高速公路K90+900～K91+080段路堑边坡中有2条次一级断层与公路斜交,山体上部的岩体中存在大量的相互切割的近似垂直的节理,山体内存在顺坡向的劣质煤层和泥岩层,构成了山体滑坡的内因。该段路堑开挖深度最大约30m,边坡开挖后,地表水沿节理裂隙入渗到软弱岩层,使软岩的抗剪强度下降,诱发了该路堑边坡滑动。滑坡计算采用简化Bishop法,通过反分析计算与工程经验类比法,确定滑动带的抗剪强度指标为?=11.5°,c=8.2kPa。经计算分析,如果仅采用抗滑桩或锚杆进行加固,其工程量大、成本高,因此提出以削坡减载为主的初步治理方案。由于在施工过程中坡顶的裂缝未及时封堵,坡面未形成有效的排水系统,以及滑动带的水不能及时有效排出,导致滑动带的抗剪强度指标进一步下滑,使削坡减载治理措施未产生明显功效。经进一步的计算分析,提出在原削坡基础上,增加长锚杆与其他防护和防水补充治理措施,有效地阻止了滑坡的进一步下滑,使滑坡保持长期稳定状态。

In segment of K90＋900 - K910＋080 at Xiangtan--Shaoyang Expressway, there are two sub-first grade faults which intersect obliquely with roadbed. A plentiful intersectant joints which are about vertical, along-slope clay shale, and bad coal seams exist in the rock mass in the upper mountain, which are intrinsic factors that induce landslide. The maximum depth of cutting slope is about 30 m. After the cutting slope is excavated, the shear resistance of soft rock seam falls because the surface water infiltrates through the top rock joints into it, and therefore, landslides take place probably. Simplified Bishop method is adopted in landslide calculation. The shear strength parameters of slide seam are drawn out that the internal friction angle φ9 =11.5° and the cohesion c= 8.2 kPa by back analysis and experience analogy. If the rock bolts or anti-slide piles are just adopted without cutting-slope unloading in the treatment, the treatment will be very expensive. Therefore, the main measures adopted for cutting-slope unloading are put forward in the first landslide treatment scheme. In construction, top cracks are not blocked and drainage system is not set up in time, the shear resistance of slide seam constantly falls because the water in the slide seam is not easily drained away; and lead the slope to slide constantly. Based on further calculation and analysis, long rock bolts and other waterproof drainage facilities are presented in additional treatment scheme. The landslide has kept stabilization for three years since the treatment measures were taken.