Study on the effect of tower foundation landslide protection measures based on a physical model test
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摘要: 大量穿越山地丘陵区的高压输电线路杆塔基础常位于滑坡灾害高易发斜坡地段, 施加适当防护措施提高其稳定性, 是保障输电线路持续安全运行的关键。为研究不同防护措施对杆塔基础滑坡的防护效果, 以湖北省巴东县燕子滑坡为地质原型, 设计制作物理试验模型, 分别开展了极端降雨条件下滑坡在无防护、施加抗滑桩与格构护坡时的物理模型试验, 从试验角度揭示了滑坡变形破坏特征与不同防护措施的防护效果。试验结果表明: 在2种极端降雨工况(50, 100 mm/h)下, 无防护的滑坡体历经了坡表冲刷、裂缝扩展、局部垮塌变形与整体滑动的演化过程; 抗滑桩措施对滑坡整体的防护效果显著, 滑坡整体处于稳定状态, 杆塔基础变形较小, 杆塔倾斜率满足规范, 但坡表会出现冲刷垮塌现象; 格构护坡措施能有效减少坡面冲刷和坡脚垮塌风险, 但在持续强降雨条件下对杆塔基础的整体稳固作用稍弱。物理模型试验结果与滑坡历史变形和实际治理效果吻合, 试验结论可为类似杆塔基础滑坡的破坏机理研究与防护工程设计提供借鉴。Abstract: A large number of high voltage transmission tower foundations crossing mountainous and hilly areas are often located in high-prone slope areas of landslide disasters. Applying appropriate protective measures to improve their stability is the key to ensuring the continuous and safe operation of transmission lines. To study the protection effect of different protection measures on the tower foundation landslide, this paper takes the Yanzi landslide in Badong County, Hubei Province as a geological prototype, designs and produces a physical test model, and carries out physical model tests of the landslide under extreme rainfall conditions(50, 100 mm/h) without protection, applying anti-slide piles and lattice protection. The deformation and failure characteristics of the landslide and the protective effect of different protective measures are revealed from the experimental point of view. The results show that under two extreme conditions, the unprotected landslide experienced the evolution process of slope surface erosion, crack propagation, local collapse and deformation, and overall sliding. The anti-slide pile measures have a significant effect on the overall protection of the landslide. The landslide is in a stable state, the deformation of the tower foundation is small, and the inclination rate of the tower meets the specification, but the slope surface will be scoured and collapsed. Lattice slope protection measures can effectively reduce the risk of slope erosion and slope toe collapse, but the overall stabilization of the tower foundation under continuous heavy rainfall is slightly weaker. The model test results are consistent with the historical deformation of the landslide and the actual treatment effect. The test conclusions can provide a reference for the failure mechanism research and protection engineering design of similar tower foundation landslides.
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图 14 杆塔倾斜率变化曲线(上角标2,3表示工况2和工况3,同表 2)
Figure 14. Variation curve of tower inclination rate
表 1 滑坡原型及相似材料物理力学参数
Table 1. Physical and mechanical parameters of the landslide prototype and similar materials
模型部位 材料组成及质量配比 天然密度ρ/(g·cm-3) 相似比1∶1 渗透系数k/(cm·s) 相似比 $1:\sqrt {300} $ 黏聚力c/kPa相似比1∶300 内摩擦角φ/(°) 相似比1∶1 滑体(原型) 粉质黏土夹碎石 1.76 3.66×10-4 25.80 23.8 滑体(相似材料) 滑体土(含碎石):河砂∶膨润土∶水= 10∶10∶3∶4 1.77 2.15×10-5 6.80 23.7 滑带(原型) 粉质黏土 1.95 — 4.67 21.3 滑带(相似材料) 玻璃珠∶膨润土∶水=15∶5∶2 1.96 — 0.20 21.0 表 2 试验工况设计
Table 2. Design of test conditions
工况 防护措施 降雨情况 1 无防护 50 mm/h降雨4 h静置2 h;100 mm/h降雨4 h,静置2 h 2 抗滑桩 50 mm/h降雨4 h静置2 h;100 mm/h降雨4 h,静置2 h 3 格构护坡加排水沟 50 mm/h降雨4 h静置2 h;100 mm/h降雨4 h,静置2 h 表 3 杆塔地基变形允许值
Table 3. Allowable values of pole tower foundation deformation
杆塔总高度/m [0, 50) [50, 100) [100, 150) [150, 200) [200, 250) [250, 300] 最大倾斜率 0.006 0.005 0.004 0.003 0.002 0.0015 注:倾斜率值为基础倾斜方向两端点的沉降差与其距离的比值 -
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