陕西省引汉济渭二期工程引水叉洞施工变形特性研究

Study on Construction Deformation Characteristics of Diversion Branch at PhaseⅡHanjiang-to-Weihe River Valley Water Diversion Project in Shaanxi Province

在已建引水隧洞旁新建叉洞会引起交叉段围岩和支护结构的应力释放与重分配,使得交叉段附近岩体与支护结构力学行为发生变化,影响已建引水隧洞的安全可靠性。基于引汉济渭二期工程,通过建立黑河引水隧洞与连接洞交叉段三维有限元模型,采用摩尔库伦屈服准则,研究在Ⅲ类围岩条件下,连接洞开挖、引水隧洞正常运行、预留岩塞段开挖及引水隧洞交叉段衬砌拆除等施工过程对引水隧洞位移、应力等影响。结果表明:连接洞前段开挖对引水隧洞的影响变形在0.02 mm以下,影响较小;引水隧洞正常运行时,在距交叉口20 m内范围内,岩塞体最大变形在0.08 mm内,因此预留20 m岩塞可以保证安全;预留岩塞段开挖,交叉口附近15 m范围内衬砌最大下沉变形为0.6 mm,衬砌未出现拉应力,引水隧洞结构安全;交叉段衬砌拆除后,剩余衬砌最大变形小于1.0 mm,引水隧洞衬砌受压,最大压应力在4.0 MPa以内,衬砌结构安全。

The construction of a branch tunnel next to the existing diversion tunnel will cause the stress release and redistribution at the surrounding rock and the supporting structure of the intersection part and it will change the mechanical behavior of the rock mass and the supporting structure near the intersection part,and affect the safety and reliability of the existing diversion tunnel.Based on the phaseⅡHanjiang-to-Weihe River Valley Water Diversion Project,and the influence of the construction process of the connection tunnel excavation,the normal operation of the diversion tunnel,the excavation of the reserved rock plug section and the removal of the lining of the diversion tunnel crossing section on the displacement and stress of the diversion tunnel is studied by establishing a three-dimensional finite element model of the intersection section of the Heihe diversion tunnel and using the Moore Coulomb yield criterion under the condition of classⅢsurrounding rock.The results show that the impact deformation of the front section excavation of the connecting tunnel is less than 0.02 mm,and the influence is insignificant.During the normal operation of the diversion tunnel,the maximum deformation of the rock plug body is within 0.08 mm within 20 m from the intersection,so the safety can be guaranteed by reserving a 20 m rock plug.The maximum subsidence deformation of the lining within 15 m near the intersection is 0.6 mm,the lining does not bear tensile stress,and the diversion tunnel structure is safe.After the intersection lining is removed,the maximum deformation of the remaining lining is less than 1.0 mm,the lining of the diversion tunnel bears compressive stress,and the maximum compressive stress is within 4.0 MPa,and the lining structure is safe.