降雨条件下土工袋加固土质边坡三维稳定性极限分析上限法研究

Rainfall is one of the most important inducements for slope instability; infiltration water can be discharged through ‘Natural Corridor’ between bags for soil slope reinforced by soilbags. Soil slope reinforced by soilbags can get a good effect to slope protection for it can greatly reducing external water infiltration into bags and slope-body behind the bags, thus effectively accelerate drainage consolidation. Besides, this method of soil slope reinforcement has been widely used for its merits of convenience making, environmental protection and low price. Based on physical scale model tests to simulate rainfall infiltration conditions to verify the reinforcement effect of soilbags. To explore failure mode and infiltrating regulation of soil slope reinforced by soilbags, investigate the change and distribution of pore water pressure in the slope and earth pressure posterior the slope. According to failure process and failure mode of the reinforced slope measured from physical scale model tests, translational and rotational velocities of slice into account at the same time, an allowable 3D failure mode and velocity field will be supposed, and the ultimate failure heights of the 3D soil slope reinforced by soilbags will be obtained using the upper-bound solution theory. Using upper bound stability method to analysis soil slope reinforced by soilbags under typical conditions, induction and sensitivity analysis on influencing factors of soilbag reinforcement effects, and provides theory basis for optimum design of soil slope reinforced by soilbags.

降雨是诱发边坡失稳的重要原因，用土工袋加固土质边坡时，入渗雨水可通过土工袋之间的“天然廊道”排出，从而大大减少渗入到土工袋及袋后坡体内部的外界水，加速土体的排水固结，达到良好的护坡效果。此外，土工袋还因具有制作便利、低廉环保等优点而被广泛应用。通过物理缩尺模型试验，模拟降雨入渗条件，验证土工袋的边坡加固效果，探求土工袋加固土质边坡时坡体破坏形态与雨水入渗规律，研究坡体内部孔隙水压力及坡后土压力变化与分布规律；利用极限分析上限法，根据物理缩尺模型试验所量测的土工袋加固边坡破坏过程与形态等数据，考虑土工袋加固边坡的平移和旋转破坏作用，建立土工袋加固边坡的三维许可破坏模式及速度场，求解其极限高度的上限解；针对典型条件下的土工袋加固土质边坡，进行极限分析上限解计算，归纳分析土工袋加固效果的影响因素并对其敏感性进行分析，为土工袋加固土质边坡的优化设计提供理论依据。

土工袋具有良好的边坡加固效果，兼有原位挡墙和表面压重的作用，此外，土工袋还因具有制作便利、低廉环保等优点而被广泛应用。随着土工袋加固边坡技术应用愈来愈广，土工袋粗放式布置的弊端逐渐凸显，其优化应用研究势在必行。通过物理缩尺模型试验，进行土工袋排列方式及不同加筋长度对砂性土质边坡加固效果影响试验研究，得出土工袋加筋对加固性能的提升尤其明显，在保证经济成本不变的条件下，并不是土工袋加筋长度越长越好，加筋（尾翼、侧翼相结合）是一种高效、环保、廉价的土工袋处理方式，值得推广应用。考虑降雨是诱发边坡失稳的重要原因，用土工袋加固土质边坡时，入渗雨水可通过土工袋之间的“天然廊道”排出，从而大大减少渗入到土工袋及袋后坡体内部的外界水，加速土体的排水固结，达到良好的护坡效果，通过降雨条件下土工袋对膨胀土边坡加固效果影响试验研究，得出降雨条件下，用土工袋加固膨胀土边坡后其裂缝前期主要为表层裂缝，并可有效抑制裂缝的开展；土工袋加固边坡后边坡破坏时间明显延长；袋装膨胀土组合体具有良好的渗透性，用其进行边坡加固时，有效抑制了水分进入土工袋下层膨胀土边坡内部,对膨胀土边坡起到良好的加固效果；利用极限分析上限法，根据物理缩尺模型试验所量测的土工袋加固边坡破坏过程与形态等数据，考虑土工袋加固边坡的平移和旋转破坏作用，建立土工袋加固边坡的许可破坏模式及速度场，求解其极限高度的上限解；针对典型条件下的土工袋加固土质边坡，进行极限分析上限解计算，归纳分析土工袋加固效果的影响因素并对其敏感性进行分析。试验及计算结果均表明：坡体极限高度随着土工袋加固宽度的增加而增大；在一定范围内，筋长越长土工袋加固边坡效果越好，但当筋长超出一定范围后，筋长的增加并未对边坡起到更好的加固效果。因此，在保证经济成本不变的条件下，并不是土工袋加筋长度越长越好。从而为土工袋加固边坡优化设计提供理论依据。