引水隧洞突涌段变形特征及控制关键技术研究

深埋引水隧洞突泥突水洞段注浆固结圈与初期支护结构作为协同承载结构,其荷载分担与变形控制对结构和施工安全有重要作用。为研究深埋引水隧洞突涌洞段围岩与支护体系稳定性,以滇中引水狮子山隧洞为工程依托,通过现场对围岩-支护监控量测与第二层型钢拱架受力监测,结合施工工况动态分析围岩-支护体系受力与变形,研究总结突涌段施工变形控制关键技术。研究结论:(1)深埋隧洞突涌洞段拱顶累计沉降17.4 mm,达预留值的17%左右;拱肩、拱腰累计收敛106.6 mm、98.1 mm,达预留值100%左右。(2)突涌洞段理论预测极限位移150 mm;现场监测评价设定阈值uo=100 mm,当达到2/3时,应采取加强措施。(3)最佳开挖方法为微台阶法。各级台阶长度控制在3 m左右,按“快挖、快支、快封闭”原则组织施工。(4)超前预支护管棚结构起到提高固结体刚度作用,较固结体提高约13倍。(5)双层支护结构强度、刚度增加,承载能力明显提高,施工安全性也得以提高。

Deformation Characteristics and Key Control Techniques of Diversion Tunnel Inrush Section

The grouting consolidation ring and the primary support in the water inrush mud tunnel section of the deep-buried water diversion tunnel are served as the cooperative bearing structure,the load sharing and deformation control play an important role in structure and construction safety.In order to research the stability of surrounding rock and support system in inrush section of deep-buried diversion tunnel,this paper is based on Shizishan Tunnel of central Yunnan water diversion project to analyze the stress and deformation of surrounding rock-support system by on-site monitoring measurement of surrounding rock-support and the stress monitoring of the second steel arch and combining with the dynamic construction conditions,and summarize and discuss the construction deformation control key technology of inrush section.Research conclusions:(1)the cumulative settlement of the vault in the inrush section of the deep-buried tunnel is 17.4 mm,which is about 17%of the reserved value,and the cumulative convergence of arch shoulder and arch waist is 106.6 mm and 98.1 mm,reaching about 100%of the reserved value.(2)The theoretical prediction of the ultimate displacement of gushing tunnel section is 150 mm,and the threshold of field monitoring evaluation is set at u;=100 mm,when it reaches 2/3,strengthening measures should be taken.(3)The best excavation method is micro-step method.The length of each step shall be controlled at about 3 m,and construction shall be organized according to the principle of“quick digging,quick support and quick closure”.(4)The advanced and pre-supported pipe roof structure can improve the stiffness of the consolidated body by about 13 times.(5)The strength and stiffness of double-layer supporting structure are improved,the bearing capacity and the construction safety is also improved.