Stability and safety criterion of a slope with weak interlayer under blasting vibration
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摘要: 运用FLAC3D软件建立了顺层台阶边坡数值模型，首先分析爆破振动作用下边坡的振速响应规律，然后通过边坡的位移、剪应变增量分析其稳定性，最后根据边坡稳定性判据，制定爆破振速安全阈值。研究表明，随着爆心距的增大，振速传播规律为近处衰减快、远处衰减慢，坡面存在高程放大效应，临空面中由于软弱夹层的阻隔影响，使得坡脚的振速最大；边坡的变形破坏受软弱夹层控制，其上覆岩体为潜在滑体，破裂面可以根据水平位移云图和塑性区分布图综合确定；边坡的破坏是一个渐进性的累积过程，位移和剪应变的累积会导致岩体的力学参数不断弱化，爆破振动劣化作用后仍有较大安全储备的边坡只会累积产生永久位移，而接近极限平衡状态的边坡将会失稳；当岩层倾角为15°~23°时，边坡振速安全阀值为21 cm/s；当软弱夹层剪出口距离坡顶高度为14 m，倾角分别为24°、29°、31°、34°时，安全阀值分别为10、8、6、5 cm/s。Abstract: A numerical model of bedding bench slope was established by using the FLAC3D software. First, the dynamic response law of the slope under the blasting waves was analyzed. Then the stability of the slope was analyzed based on the displacement and the shear strain increment. Finally, according to the judgment of the slope stability, the appropriate velocity safety threshold of blasting vibration was developed. Studies reveal that the attenuation rate of the vibration amplitude decreases with higher blaster center distance value. There is elevation amplification effect on the slope and the main vibration velocity reaches the maximum at the foot of the free surface due to the existence of the weak interlayer. The deformation and failure of the slope is controlled by the weak interlayer. The upper rock mass becomes the potential sliding mass when there is tensile and shear failure in the weak interlayer, and the fracture surface can be determined according to the horizontal displacement map and the plastic zone distribution map. The slope failure is a progressive accumulation, displacement and shear strain accumulation will lead to the mechanical parameters of the rock weakening. There is a permanent displacement after blasting vibration if the slope has a great safety margin, while the slope near the state of limit equilibrium will be instability. The safety threshold of the slope is 21 cm/s if the strata inclination is from 15° to 23°. When the cut out height of the slope with the weak interlayer is 14 m and the strata inclinations are 24°, 29°, 31° and 34°, the corresponding safety threshold will be 10, 8, 6 and 5 cm/s.
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Key words:
- blasting vibration /
- slope stability /
- safety threshold /
- weak interlayer /
- bedding slope
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图 2 边坡动力分析模型和监测点位置分布
Figure 2. Dynamic numerical simulation model of the slope and location distribution of monitoring points
图 3 N1水平和垂直速度曲线与输入波形的比较
Figure 3. Horizontal and vertical velocity curves at N1 compared with input wave curves
图 6 爆破后水平位移云图和塑形区分布
Figure 6. Plastic zones and horizontal displacement of slope after blasting
图 9 监测点水平向位移时程曲线
Figure 9. Time-dependent curves of horizontal displacement of monitoring points
图 10 监测单元剪应变增量时程曲线
Figure 10. Time-dependent curves of shear-strain increment of key elements
图 11 监测点N7的水平向位移时程曲线
Figure 11. Time-dependent curves of horizontal displacement at N7
图 14 软弱夹层倾角与安全阈值的关系
Figure 14. Relationship of weak interlayer inclination and safety threshold
表 1 物理力学参数
Table 1. Physico-mechanical parameters of rock mass
岩体 弹性模量/GPa 泊松比 内聚力/MPa 内摩擦角/(°) 重度/(kN·m-3) 抗拉强度/MPa 灰岩 7 0.2 1.5 35 26.8 1 夹层(天然) 0.68 0.3 0.04 29 20 0.016 夹层(残余) 0.68 0.3 0.01 22 20 0.016 
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