黄土高边坡土钉-预加固桩复合支护体系性状分析

Behavior of a high steep loess slope strengthened by combination system of soil nails and stabilization piles

土钉-预加固桩复合支护技术已在基坑及边坡工程中取得了大量应用,但在黄土高边坡开挖中的应用相对较少。基于详细的现场监测数据并辅以有限元数值计算,分析了边坡开挖过程中支护体系受力及变形随时间和空间的变化规律。结果表明:预加固桩的水平位移随着时间的推移与开挖深度的增加呈增大趋势,并最终趋于稳定,同时,桩身剪力及弯矩亦随开挖的进行而不断增大;剪力最大值的位置不断下移,说明边坡的潜在滑动面有不断向下扩展的趋势。与深基坑支护桩的土压力分布相比,土钉-预加固桩复合支护体系中桩后土压力随开挖呈不断减小的趋势,但桩前土压力随着开挖深度的增加,有增有减。随着施工开挖深度的增加,土钉所测得的应力有着明显的增大,说明土钉对抑制坡体变形起到了一定作用。在预加固桩的影响下,桩上方坡体的最危险破裂面为圆弧状,其剪出口位于预加固桩桩顶处。开挖深度较浅时,土钉对整体稳定性的贡献较大,而随着开挖深度的变大,预加固桩的加固效果开始占主导地位。

The combination of soil nails and stabilization piles （CSNSP） has been widely used as a reinforcing technique to retain excavations and stabilize slopes, but few relevant applications are found for high loess slope. Based on a high steep loess slope strengthened by CSNSP, the behavior of the strengthening system is investigated by field monitoring and finite element method. The results show that the lateral displacement, shear force and bending moment of piles increase gradually with the increment of excavation depth;and the displacement tends to be steady gradually. The location of the maximum shear force in the pile body shows a declining trend which indicates that the potential failure surface develops downwards. The distribution of soil pressure around piles in CSNSP system is compared with which appeared in deep foundation pit. The soil pressure on the back side of piles shows a trend of decrease with excavation while the soil pressure on the front side appears to be fluctuant. With the growth of excavation depth, the measured stress of the reinforced soil nails increases significantly, which indicates that the slope deformation is limited by the soil nails. The most dangerous rupture surface of the slope above piles appears to be a circular arc and the shear opening locates at the head of the piles. In addition, the proportion of soil nails to stability for the overall system is larger than the stabilization piles when the excavation depth is shallow, but the situation changes with the increment of the excavation depth.