特大断面硬岩隧道爆破开挖技术研究——以丰宁隧道Ⅱ级围岩段为例

为验证特大断面硬岩隧道爆破空孔布置形式及爆破参数选取的合理性,并解决现场试爆造成的危险系数增加和费用增高等问题。对丰宁隧道Ⅱ级围岩段采用ANSYS/LS-DYNA有限元模拟软件,模拟了中间空孔和四周空孔2种布置形式的直眼掏槽方案,分析爆破应力波传播规律及岩石破坏情况,确定前者为优选方案;利用光面爆破技术,确定周边眼合理参数;结合现场观测数据,评价爆破效果。证明"中间空孔布置的直眼掏槽+合理的爆破参数"设计是合理的,且数值模拟技术可有效降低成本,其研究成果可为类似工程提供参考。

Study on Blasting Technology for Large Cross-section Hard Rock Tunnels: Case Study on Fengning Tunnel

With 120 m2 cross section area, Fengning tunnel has 4 063 m long section located in Grade Ⅱ surrounding rock. In the paper, two parallel cut hole schemes, i.e., scheme with the central holes being empty and scheme with the surrounding holes being empty, for the Grade Ⅱ surrounding rock section of Fengning tunnel are simulated by means of ANSYS/LS DYNA finite element program, and the transmission rules of the blasting stress waves and the rock destruction conditions are analyzed, which concludes that the scheme with the central holes being empty is the favorable scheme; appropriate parameters are determined for the contour holes on basis of the smooth blasting technology; the blasting effect is assessed on basis of the field observation data. Conclusions drawn are as follows: 1) The design of "parallel cut hole with the central holes being empty+appropriate blasting parameters" is rational; 2) The numerical simulation technology can reduce the cost effectively. The study result can provide reference for similar projects in the future.