椭圆形桩井护壁爆破振动安全判据

Blasting vibration safety criterion for semi-ellipse-shaped shaft wall

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8cm/s,现场测试验证了预设判据的合理性。

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-DYNA3 Dand 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.