岗岭隧道穿越破碎带的衬砌结构性能研究

Research on Performance of Liners in Gangling Neighborhood Tunnels Crossing Broken Rock Mass

小净距隧道穿越破碎带时引发的围岩大变形给衬砌等支护结构的性能带来了严峻的挑战,亟需开展施工过程中的衬砌性能评价研究。基于此,采用基于收敛-约束法的纵向位移剖面(LDP)法和强度校核法等理论分析方法,并结合数值模拟技术研究了岗岭小净距隧道穿越破碎带时围岩稳定与衬砌支护性能。结果表明:采用基于收敛-约束的LDP方法,可有效确定围岩衬砌合理支护时机对应的破碎带和完整岩体的不同反力系数,使得破碎带围岩的开挖变形量值从24 mm降低至7 mm,且避免了小净距隧道中夹岩塑性区贯通破坏;针对破碎带和完整岩体分界处出现的衬砌拉弯和压弯破坏现象,提出了临时素混凝土仰拱的施工支护优化方案,使得衬砌混凝土弯矩从0.1 MN·m减低到0.06 MN·m,约减少了40%,有效改善了衬砌的受力状态,提高了衬砌混凝土的安全性能,安全系数从1.0增加到1.25;提出了岗岭隧道安全施工的衬砌初凝强度阈值为60%的最终强度,此时衬砌混凝土的安全系数约为1.03。相关研究成果可为小净距隧道的施工工艺和支护设计提供参考。

The large deformation of neighborhood tunnels crossing broken rock mass has brought serious challenges to the performance of liners and other support structures,therefore it is urgent to carry out performance evaluation of liners in the construction process of tunnels.Based on this,theoretical analysis methods such as the longitudinal displacement profile(LDP)method based on the convergence-constraint method and the strength check method are used,combining with numerical simulation technology,the stability of the surrounding rock and the lining support performance of the Gangling Tunnel crossing broken rock mass are studied.Results show that:Using the convergence-constraint-based LDP method can effectively determine the different reaction coefficients of the broken zone and the intact rock mass corresponding to the reasonable support time of the surrounding rock lining,so that the excavation deformation value of the surrounding rock of the broken zone is reduced from 24 mm to 7 mm.In addition,the penetrating failure of the plastic zone of the intercalated rock in the tunnel with a small clear distance is avoided;in view of the tension and compression failure of the lining at the boundary between the broken zone and the intact rock mass,an optimization plan for the construction and support of the temporary plain concrete inverted arch is proposed,which makes the bending moment of the lining concrete is reduced from 0.1 MN·m to 0.06 MN·m,a reduction of about 40%,which effectively improves the stress state of the lining and improves the safety performance of the lining concrete,and the safety factor is increased from 1.0 to 1.25.The threshold of the initial setting strength of the lining for safe construction of the Gangling Tunnel is 60%of the final strength,and the safety factor of the lining concrete is about 1.03 at this time.The research results can provide reference for the construction technology and support design of neighborhood tunnels.