卵石淤泥复合地层围堰稳定及防渗控制技术

Cofferdam Stability and Seepage Control Technique in Cobble-Peaty Mixture Soils

围堰明挖法是水下隧道常用施工方法,围堰的稳定及防渗控制关系着工程建设安全。水域地层中广泛分布的深厚卵石淤泥复合地层对围堰稳定性及防渗性提出了极大考验。为解决卵石淤泥复合地层上筑土石围堰的稳定性及防渗控制,以杭州市青山湖湖底隧道围堰为依托,提出了抛石与TRD结合的土石围堰结构,解决土石围堰施工过程中卵石层防水性与淤泥层围堰稳定性关键技术难题。实践表明:采用抛石与TRD结合的土石围堰结构30 d地表累计沉降小于4.5 mm,最大水平位移变化量小于7 mm,水泥土平均渗透系数为4.30×10^(-7) cm·s^(-1)。围堰的稳定性以及防渗性均能满足实际工程需求。

The cofferdam cut-and-cover method is a common underwater tunnel construction method.The seepage control and the stability of the cofferdam are critical to the safety of the entire tunnel construction.The deep embedded and thick cobble and peaty soils which are widely deposited underneath the project site impose a significant challenge for the stability and seepage control of the cofferdam.To overcome these difficulties,the riprap plus Trench cutting Re-mixing Deep Wall(TRD)method was used in the excavation of the tunnel underneath the Qingshan Lake project.The result shows that the 30-day cumulative surface settlement of the earth-rock cofferdam structure combined with riprap and TRD was less than 4.5 mm,the maximum horizontal displacement change was less than 7 mm,and the average permeability coefficient of cement and soil was 4.30×10^(-7) cm·s^(-1).The stability and the seepage resistance of the cofferdam could meet the design needs.