CENTRIFUGE MODEL TEST OF SLOPE EXCAVATION AND SUPPORT UNDER RAINFALL
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摘要: 为研究降雨下高速公路高边坡在开挖及运营过程中的变形规律及稳定性,以柳南公路改扩建工程某处典型高边坡为原型,利用大型土工离心机及自主研发降雨装置,开展12组不同开挖-支护时序边坡模型试验,通过对边坡从变形至破坏全过程监测,分析不同支护时序条件对边坡稳定性的影响。结果表明:实时支护能有效抑制边坡在水平和竖向的变形,在边坡开挖至第1级和第6级后,坡顶水平变形分别降低33.9%和30.4%,竖向变形降低54%和11.6%;实时支护对维持降雨下边坡稳定状态非常有利,边坡开挖至第2、4、6级后遭遇降雨,其稳定系数降低了10.1%、5.4%、6.5%;相同降雨量下,无实时支护边坡的稳定系数要比实时支护至少降低50%,说明了实时支护对降雨下边坡稳定性的意义巨大。Abstract: In order to study the slope stability and deformation characteristics under rainfall during excavation and operation process, the typical high slope of Liu-Nan highway extension project is chosen as the prototype. Using the geotechnical centrifuge of Chang'an University and independently developed rainfall device, 12 groups of centrifuge model tests of different excavation-support sequence were carried out. Through monitoring the whole process of slope from deformation to failure, the effect of different support sequence on the stability of slope was analyzed. The following results are obtained:the horizontal deformation and the vertical deformation of the slope are well restricted by the timely-support method, the horizontal deformations of the 1th and 6th grade excavation are reduced by 33.9% and 30.4%, and vertical deformations are reduced by about 54% and 11.6%; It is extremely favorable to use the timely-support excavation method for the stability of the slope under rainfall condition. The rainfall stability coefficient have a very small drop at 2th, 4th and 6th grade excavation after rainfall and reduce by 10.1%, 5.4% and 6.5% respectively. Under the same rainfall, the stability coefficient of slope without timely-support is at least 50% lower than that of timely-support excavation method, which shows that it is of great significance to slope stability under rainfall.
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Key words:
- highway /
- slope excavation /
- reconstruction project /
- timely-support /
- model test
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表 1 离心机技术指标
Table 1. Technical indexes of geotechnical centrifuge
离心模型箱参数 规格 离心机容量/(g·t) 60 离心加速度/g 1~200 有效半径/m 2.0 启动历时/min ≤20 (从静止到200 g) 模型箱外部尺寸/(m×m×m) 0.7×0.36×0.5/0.5×0.4×0.5 表 2 边坡岩土体工程参数
Table 2. The mechanical parameters of the rock masses
土层 重度/
(kN/m3)粘聚力
c/kPa内摩擦角
$φ$/(°)坡高 平均
倾角边坡
分级砾质粘性土 19.1 28.9 21.3 17 39.6 3 砂质粘性土 20.2 30.8 24.2 34 34.9 2 泥质砂岩 24.6 40.2 27.1 6 33.8 1 表 3 离心模型试验相似比
Table 3. Similitude ratios used in centrifuge model tests
类型 物理量 相似比 线位移L/m 1:100 几何尺寸 面积S/m2 1:104 体积V/m3 1:106 弹性模量E/(kN·m-2) 1:1 变形模量E0/(kN·m-2) 1:1 容重γ/(kN·m-3) 100:1 材料特性 应变τ 1:1 泊松比υ 1:1 内摩擦角$φ$/(°) 1:1 黏聚力c/(kN·m-2) 1:1 动力特性 固结时间T/h 1:104 表 4 砂岩模拟材料力学参数
Table 4. Mechanical parameters of sandstone simulation material
重晶石:水泥:石膏 重度/(kN/m3) 弹性模量 单轴抗压强度 1:1.21:1.28 23.1~26.3 2.7 16.3 表 5 模型支护与降雨情况
Table 5. Supporting conditions of models and rainfall situation
编号 开挖-支护时序 降雨时间 降雨条件 ES-1 实时支护(边开挖边支护) 第2级边坡开挖结束 ES-2 第4级边坡开挖结束 暴雨(30 mm/h持续7 h) ES-3 第6级边坡开挖结束 ES-4 暴雨(24 h总降雨量50~100 mm) ES-5 全部边坡开挖结束 大暴雨(24 h总降雨量100~200 mm) ES-6 特大暴雨(24 h总降雨量>200 mm) E-1 6级边坡全部开挖完后才支护 第2级边坡开挖结束 E-2 第4级边坡开挖结束 暴雨(30 mm/h持续7 h) E-3 第6级边坡开挖结束 E-4 暴雨(24 h总降雨量50~100 mm) E-5 全部边坡开挖结束 大暴雨(24 h总降雨量100~200 mm) E-6 特大暴雨(24 h总降雨量>200 mm) -
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