FAILURE MECHANISM OF WATER-LEVEL FLUCTUATION ZONE WITH UMBRELLA-SHAPED ANCHORS UNDER RAPID DRAWDOWN BASED ON TRANSPARENT SOIL
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摘要: 消落带是关系到库岸滑坡稳定性的敏感地带,尤其在库水下降作用下,消落带应力、渗流及变形发生明显改变。而伞形锚作为一种新型锚固技术,以其结构简单、安装方便、承载力高等优点逐渐运用于工程实践。因此,研究库水位骤降下消落带滑坡-伞型锚固体系破坏机理具有重要意义。本文以新疆TH1水库滑坡水位消落带为原型,采用透明土模型试验,考虑不同坡角和锚固间距,设计了6个消落带滑坡-伞型锚固体系物理试验。采用粒子图像测速(PIV)技术获得了滑坡内部位移、速度和宏观变形数据。结果发现:(1)较未加固模型,减少坡角、植入伞型锚杆可以明显提高消落带滑坡稳定性,减少消落带滑坡滑移速度及破坏程度;(2)不同锚固间距与消落带坡角条件下,消落带滑坡-伞型锚固体系呈现3种典型破坏模式:完全贯穿式,局部滑移式及多级滑移式;(3)坡角越大,滑坡受库水位骤降影响越大,滑动面越深,而伞型锚杆的植入可以改变滑动面的形态、位置,提高滑坡整体稳定性。Abstract: The rapid drawdown of reservoir water can significantly influence the stress,seepage,and deformation of the water-level-fluctuation(WLF)zone,which affects the long-term stability of the reservoir bank slope. The umbrella-shaped anchor has ease of production and installation,and higher load capacity,so it has been gradually used to stabilize the slope. Thus,the deformation and failure mechanism of WLF zones can be reinforced by umbrella-shaped anchors under rapid drawdown conditions. Using transparent soil technology,we designed six physical tests of the WLF zone with umbrella-shaped cables considering different slope angles and anchoring spacings. We obtained the internal displacement,velocity in models using Particle Image Velocimetry(PIV)technology. We found:(1)The stability of the landslide obviously increased with the decrease of slope angle and anchor spacing. (2)There were three failure models of anchor-reinforced systems: total failure,local collapse and multi-sliding. (3)The sliding surfaces had deeper depth with the increase of slope angle because of the effect of the water rapid drawdown,and the umbrella cables obviously changed the shape and location of the sliding surfaces,and increased the landslide stability.
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Key words:
- Transparent soil /
- Reservoir landslide /
- Umbrella-shaped anchors /
- Rapid drawdown /
- Failure mechanism
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表 1 原型与模型参数
Table 1. The parameters of the model and prototype
长度/cm 高度/cm 宽度/cm 重度/kN·m-3 黏聚力/kPa 摩擦角/tan φ 原型 1650 1100 750 20.1 30 0.404 模型 22 15 10 13.3 0.4 0.404 相似比 75 75 75 1.5 75 1 表 2 高纯度熔融石英砂及标准砂物理力学参数
Table 2. Parameters of fused quartz and sand
试样名称 比重Gs 最大干密度/g·cm-3 最小干密度/g·cm-3 最大孔隙比 渗透系数/cm·s-1 内摩擦角/(°) 熔融石英砂 2.18 1.388 1.188 0.835 0.0063 39.5 标准砂 2.63 1.880 1.522 0.740 0.0057 43.0 表 3 相似锚杆与原型参数
Table 3. Parameters and similar ratio of the prototype and model
锚杆 抗拉强度/MPa 弹性模量/GPa 直径/mm 倾角/(°) 张开角/(°) 原型 300~600 200 22 25 120 模型 15 2 4 25 120 相似比 20~40 100 5.5 1 1 表 4 消落带滑坡-伞型锚固体系试验设计方案
Table 4. Parameters of six models of WLF zone-anchor cables system
试验序号 试验因素与水平 坡角/(°) 水位下降速度/cm·min-1 锚固方式 L1 34 5 D=2.5R L2 25 5 D=2.5R L3 30 5 D=2.5R L4 34 5 D=R L5 34 5 D=R & 2.5R L0 34 5 / 表 5 消落带滑坡体系变形破坏特征
Table 5. Deformation characteristics of the WLF zone system
模型 始滑时间/s (变形率≥0.03mm·s-1) 最大平均位移/mm 最大平均速度/cm·s-1 L1 50 12.47 0.216 L2 96 5.10 0.074 L3 93 13.28 0.169 L4 72 5.19 0.114 L5 61.6 10.80 0.214 L0 31 16.23 0.234 -
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