Blasting vibration safety criterion for semi-ellipse-shaped shaft wall
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摘要: 钻爆法作为桩基开挖的主要破岩手段,所产生的爆破振动引起桩井护壁结构发生动态响应,进而影响桩井结构的稳定性。利用有限元分析软件ANSYS/LS-DYNA3D,以峰值质点振动速度和有效拉应力作为指标,模拟了椭圆形桩井护壁结构对爆破振动的动态响应。计算结果表明:不同掘井深度的椭圆形桩井护壁对不同段药量爆破振动的动态响应呈相似规律,最大质点峰值振速及峰值拉应力分布一致,均位于护壁井口端的弧形壁部分,响应强度随段药量的减小而减小;护壁结构的峰值拉应力与峰值振速呈线性关系,基于抗拉强度准则,确定了该工程条件下护壁的安全振动速度阈值为8 cm/s,现场测试验证了预设判据的合理性。Abstract: As a major technique for rock breakage, the drill and blast method brings about serious blasting vibration that poses hazards for the structural stability of the shaft wall. In this paper, we simulated the interactive process of the blasting seismic wave and the semi-ellipse-shaped shaft wall using the finite-element numerical software ANSYS/LS-DYNA3D and taking the peak particle velocity (PPV) and the effective tensile stress as the evaluation indexes of the dynamic response. The calculated results indicate that for the shaft walls with different excavation depths there exist similar patterns governing the dynamic response to different maximum charges, and both the peak effective tensile stress and PPV are located at the top arch, whose intensities decrease along with the decrease of the maximum charge. Based on the tensile strength principle and the linear relationship between the peak effective tensile stress and PPV, we established the critical blasting vibration safety criterion as 8 cm/s under the present engineering conditions for this project, and conducted on-site tests which verified the validity of the pre-set criterion.
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Key words:
- safety vibration velocity /
- shaft wall /
- peak particle velocity
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表 1 爆破参数
Table 1. Blasting parameters
孔距/mm 排距/mm 炮孔深度/m 药卷直径/mm 单耗/(kg·m-3) 单孔药量/kg 50~80 50~80 1.0(掏槽),0.8(周边) 32 2.6 1.2(掏槽),0.8(周边) 表 2 炸药的材料及状态方程参数
Table 2. Material and EOS parameters of explosive
ρ/(g·cm-3) D/(km·s-1) pCJ/GPa A/GPa B/GPa R1 R2 ω E0/GPa 1.2 4.8 9.7 214.4 18.2 4.2 0.9 0.15 4.192 表 3 岩石材料参数
Table 3. Material parameters of rock
ρ/(g·cm-3) E1/GPa ν σY/GPa E2/GPa β εf 2.7 40 0.22 46 0.04 0.5 0.05 表 4 混凝土材料参数
Table 4. Material parameters of concrete
ρ/(g·cm-3) G/GPa AHJC BHJC CHJC N fc/MPa Tmax/MPa εfmin Smax 2.44 14.86 0.79 1.6 0.007 0.61 48 40 0.01 7 pcr/MPa plock/MPa μcr μlock D1 D2 K1/GPa K2/GPa K3/GPa 160 800 0.001 0.1 0.04 1 85 -171 208 表 5 空气材料参数
Table 5. Material parameters of air
ρ/(kg·m-3) C0 C1 C2 C3 C4 C5 C6 e0/MPa V0 1.25 0 0 0 0 0.4 0.4 0 0.256 1 表 6 测点处峰值振速的模拟与实测结果
Table 6. Simulation and experimental results of peak particle velocity at measuring points
工况 S=15.5 m的圆弧壁中间单元节点的峰值振速/(cm·s-1) S=8.5 m的圆弧与直段连接处单元节点的峰值振速/(cm·s-1) 模拟 实测 模拟 实测 1 4.7 8.0 4.7 4.5 2 6.3 6.1 3.4 3.1 3 4.6 4.4 2.3 2.0 4 3.2 2.9 1.1 1.0 表 7 数值计算结果
Table 7. Numerical calculation results
工况 h/m wmax/kg στ/MPa vmax/(cm·s-1) 1 4 8.0 17.02 74.0 2 4 4.8 14.10 64.1 3 4 4.0 11.14 48.4 4 4 3.6 7.48 33.1 1 8 8.0 5.34 23.4 2 8 4.8 4.67 20.2 3 8 4.0 3.52 15.3 4 8 3.6 2.41 10.4 1 12 8.0 2.73 11.9 2 12 4.8 2.35 10.3 3 12 4.0 1.83 7.8 4 12 3.6 1.22 5.3 1 16 8.0 1.75 7.4 2 16 4.8 1.44 6.4 3 16 4.0 1.12 4.8 4 16 3.6 0.76 3.3 表 8 实测峰值振速
Table 8. Measured peak particle velocities
工况 水平向峰值振速/(cm·s-1) 垂直向峰值振速/(cm·s-1) 测点1 测点2 测点3 测点4 测点1 测点2 测点3 测点4 1 5.9 5.8 6.0 5.9 7.1 7.1 7.1 7.0 2 4.8 4.9 4.8 4.9 6.1 6.2 6.2 6.1 3 3.7 3.5 3.6 3.7 4.5 4.5 4.6 4.5 4 2.6 2.7 2.7 2.7 3.1 3.0 3.1 3.1 -
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