软岩力学参数对薄基岩顶板隧道爆破围岩振动的影响

Influence of Soft Rock Mechanics Parameters on Surrounding Rock Vibration during the Tunnel Blasting with Thin Bedrock Roof

针对薄基岩顶板条件下隧道的爆破施工过程中围岩稳定性差等特点,采用数值模拟计算方法分析了上覆软岩的各项物理力学参数的变化对围岩振动的影响.结果表明:空洞效应显著系数最大值出现在掌子面后方2~4m范围内,施工期间应重点监测该范围内的拱顶沉降等数据;环向上,最大峰值振动速度矢量和出现在岩层界面与隧道壁面的切点处;掌子面附近的围岩峰值振动速度与上覆软岩的容重及泊松比呈正相关关系,与上覆软岩的弹性模量及内摩擦角呈负相关关系.在类似工程背景下,最大峰值振动速度与上覆软岩4项力学参数的拟合关系式分别为:f1(γ)=21.96e0.87γ,f2(E)=-9.85lnE+15.61,f3(μ)=13.98e0.62μ,f4(φ)=0.071φ2-22.98φ+48.18.

In view of the poor stability of surrounding rock during tunnel blasting construction under the condition of thin bedrock roof,the effects of various physical mechanical parameters of overlying soft rock on surrounding rock vibration were analyzed with the numerical simulation method.The results show that:the maximum value of the significant coefficient of cavity effect appears in the range of 2~4 m behind the tunnel face,and the data such as vault settlement within this range should be monitored emphatically during the construction.In the circumferential direction,the maximum vibration velocity appears at the contact point between the rock layer interface and the tunnel wall.The peak vibration velocity of surrounding rock near the tunnel face is positively correlated with the unit weight and poisson’s ratio of overlying soft rock,and negatively correlated with its elastic modulus and internal friction angle.Under similar engineering background,the fitting formulas of the maximum peak vibration velocity and the four mechanical parameters of overlying soft rock are f1(γ)=21.96 e0.87γ,f2(E)=-9.85 ln E+15.61,f3(μ)=13.98 e0.62μand f4(φ)=0.071φ2-22.98φ+48.18,respectively.