穿越城区组合衬砌隧洞外水内渗问题研究

External water seepage into water conveyance tunnel across urban areas with composite lining structure

近年来我国兴建的穿越城区引水隧洞工程中采用了一种新型组合衬砌结构,由外层管片、内层不透水钢管和两者之间的回填混凝土、排水板组成。运行期内水压力经回填混凝土向外传递,外层管片朝外变形,管片间接缝会张开,进而引发外水内渗问题。结合深圳市罗田水库-铁岗水库输水隧洞工程,建立某典型洞段渗流分析的三维有限元计算模型,分析了多种外部条件下衬砌的外水内渗流量和外水压力。分析表明:完建期管片渗透系数每减小一个量级,隧洞渗流量降低约90%,回填混凝土使隧洞渗流量降低30%~40%,注浆圈对隧洞渗流量影响较小。运行期接缝为主要渗漏通道,占总渗流量的90%以上,此时注浆圈可以明显降低隧洞渗流量。隧洞渗流量的峰值出现在运行期,应作为隧洞外水内渗流量的控制条件。隧洞外水压力取值应以自密实混凝土回填后的完建期最大。

In recent years,a new type of composite lining has been adopted in the construction of diversion tunnels across urban areas in China.The joint of its outer segments may open under the internal water pressure transmitted by the back-filled self-compacting concrete,thereby causing a problem of external water seepage.In this paper,a three-dimensional finite element model for the seepage in a typical tunnel section is developed;the amount of seepage flow and the external water pressure of the lining under various external conditions are examined in a case study of the Luotian Reservoir to Tiegang Reservoir water conveyance tunnel project in Shenzhen.The results show that for the tunnel in the completion stage,its seepage flow decreases by about 90%if the seepage coefficient of the outer segments is decreased by one order of magnitude.Concrete backfilling reduces the seepage by 30%~40%,and the grouting ring has little effect on the seepage.During operation,the lining joint is the main leakage channel,accounting for more than 90%of the total seepage;the grouting ring in this stage can reduce the seepage significantly.The peak seepage occurs in the operation stage,and it is thought to be a control condition of the tunnel seepage.The external water pressure determination should be based on the completion stage subsequent to the self-compacting concrete backfilling.