Analysis of sliding mechanism of the cut slopes with multi-weak interlayers under rainfall
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摘要: 本文基于抚顺西露天矿南帮滑坡工程实例，分析地下水及降雨入渗作用下顺倾软弱夹层边坡失稳的水力学模式，采用FLAC3D软件对抚顺西露天矿南帮边坡在地下水及降雨入渗作用下边坡变形的演化过程进行数值模拟分析，总结地下水及降雨入渗作用下顺倾多软弱夹层边坡的滑动规律。结果表明：降雨入渗和地下水的流动对坡体产生渗透压力，坡体破裂面大量发育，最大合位移约为1.27 m，形成多阶段滑坡，整体呈现混合式滑坡；边坡变形破坏期间，坡顶附近易沿弱层产生拉涨破坏，为地表水渗透和地下水的运移提供通道，并呈现多滑面的特点，形成贯通的剪切破坏面，进一步导致边坡的多段变形；地下水及降雨入渗影响下，边坡弱层含水率累积增加，损伤破裂，体积应变增量降低，有效应力降低，孔压累积上升，抗剪强度减低，从而诱发滑坡。相比降雨工况下，采用不同坡高高度回填压脚防护的边坡具有较高的安全系数，考虑工程实际综合比较不同防治方案，在降雨影响下，回填压脚至1/2坡高高度防治效果更好，边坡较稳定。Abstract: This paper presents an analysis of the hydraulic model of the slope instability of a down-dipping soft sandwich slope, focusing on the southern slope landslide project of Fushun West open Pit Mine. The study investigates the effects of groundwater and rainfall infiltration on the slope deformation evolution process using numerical simulation analysis with FLAC3D software. The sliding law of the slope with soft interlayer under the action of groundwater and rainfall infiltration is summarized. The results show that rainfall infiltration and groundwater flow produce osmotic pressure on the slope, causing the development of a large number of rupture surfaces on the slope. The maximum cumulative displacement is about 1.27 meters, resulting in a multi-stage landslide with a mixed landslide type. During the deformation and failure of the slope, tension failure is prone to occur along the weak layer near the slope top, providing a channel for surface water infiltration and groundwater migration, and showing the characteristics of multiple sliding surface, forming a continuous shear failure surface, which further leads to the multi-stage deformation of the slope. Under the influence of groundwater and rainfall infiltration, the water content in the weak layer of slope accumulates, resulting in damage and rupture, reducing the volume strain increment, lowering the effective stress, increasing the pore pressure, and reduing the shear strength, thereby inducing landslide. To improve the stability of the slope, the study compares different prevention and control schemes, including backfilling presser foot with different slope heights. The study finds that compared with the rainfall condition, the slope protected by backfilling presser foot with different slope heights has a higher safety factor. Considering the engineering practice, the backfilling and pressure protection up to half of the slope height has a better effect on preventing and controlling the slope, and the slope is more stable.
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Key words:
- groundwater and rainfall infiltration /
- weak interlayer /
- FLAC3D /
- numerical simulation /
- stress
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图 1 抚顺西露天矿南帮工程地质剖面图
Figure 1. Geological cross-section of the southern slope of Fushun West open Pit Mine
图 2 抚顺西露天矿南帮地裂缝
Figure 2. Site photo of ground cracks on the southern slope of Fushun West open Pit Mine
图 3 南帮滑坡形成机制模型
Figure 3. Model of formation mechanism of the southern slope of Fushun West open Pit Mine
图 5 坡体随循环步长增加的合位移变化情况（单位：m）
Figure 5. The variation of the cumulative displacement of the slope with increasing cycle steps （unit: m）
图 6 坡体随循环步长增加发展的塑性区变化情况
Figure 6. Changes in the plastic zone developed by the slope with increasing cycle step
图 8 监测点体积应变增量随时间的发展演化情况
Figure 8. Evolution of the development of volumetric strain increments over time at monitoring points
图 9 监测点x向有效应力随时间的发展演化情况
Figure 9. Evolution of the development of the effective stress in the x-direction over time at monitoring points
地层岩性 密度/（kg/m3） 弹性模量/（GPa） 泊松比 粘聚力/（MPa） 抗拉强度/（MPa） 内摩擦角/° 渗透系数/（m2/Pa/s） 凝灰岩 2590 10 0.24 3 2 45 9e-10 凝灰岩（弱化） 2590 1 0.24 0.3 0.2 40 9e-10 玄武岩 2800 25 0.23 3 2 40 9e-10 玄武岩（弱化） 2800 2.5 0.23 0.3 0.2 35 9e-10 煤 1400 1.2 0.24 0.45 0.15 30 9e-10 煤（弱化） 1400 1.2 0.24 0.45 0.24 35 3e-9 弱层 2100 15 0.24 2.5 1.75 48 9e-10 弱层（弱化） 2100 0.018 0.4 0.003 0.01 10 9e-10 花岗片麻岩 2800 35 0.22 4 3 45 8e-9 回填土 1860 0.27 0.3 0.2 0.1 25 9e-10 回填土（弱化） 1860 0.027 0.3 0.02 0.01 20 9e-10 断层泥 1800 0.01 0.4 0.18 0.2 7 3e-9 油页岩 2550 5 0.22 0.15 0.35 35 9e-10 
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表 2 边坡防治方案稳定性评价结果
Table 2. Stability evaluation results of slope control scheme
工况 防治方案剖面图 边坡合位移变化云图 安全系数 稳定性分析 现状 
1.22 稳定 降雨 
0.71 不稳定 回填1/10
坡高
0.89 不稳定 回填1/5
坡高
0.96 不稳定 回填1/4
坡高
1.02 欠稳定 回填1/3
坡高
1.08 欠稳定 回填1/2
坡高
1.15 稳定 回填3/5
坡高
1.21 稳定 回填2/3
坡高
1.42 稳定 回填3/4
坡高
1.36 稳定
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