沉管隧道下穿防波堤基础设计及沉降控制

Foundation design and settlement control of immersed tunnel undercrossing breakwater

大连湾海底隧道工程沉管隧道基础大部分段落位于强、中风化硬岩层,仅E9—E12管节基底位于含砾石粉质黏土、粉质黏土层,且E12管节上方存在1个防波堤。考虑沉管基础纵向软硬地层差异及防波堤处荷载变化,为防止下穿防波堤沉管基础沉降差异及刚度变化过大,对管节接头剪力键和结构内力造成影响,运用理论计算和数值模拟等方法,进行管底荷载、结构内力、沉降以及地基刚度计算。对不满足设计要求的软弱地层区段基础,采用2 m块石换填及局部地基块石夯填处理等思路进行沉管基础设计。为控制防波堤突变荷载的差异沉降,对下穿防波堤区段管节上部复建结构进行减载设计,并给出管节预抬量合理值,实现管节纵向沉降协调及刚度过渡。为后续沉管下穿码头、岸堤、防波堤等地基基础设计和沉降控制提供技术参考和借鉴。

Most sections of immersed tube tunnel foundation of Dalian Bay Subsea Tunnel project are located in strongly and moderately weathered hard rock strata,only the base of E9 to E12 elements is located in silty clay and silty clay layer containing gravel,and there is a breakwater above the E12 element.Considering the difference between the longitudinal soft and hard strata of the immersed tube foundation and the load change at the breakwater,in order to prevent the settlement difference and stiffness of immersed tube foundation undercrossing breakwater from being too large,it will affect the shear key of the joint and the internal force of the structure,theoretical calculation and numerical simulation were used to calculate the tube bottom load,structural internal force,settlement and foundation stiffness.For the foundation of weak stratum section that does not meet the design requirements,the ideas of 2 m block stone replacement and local foundation block stone tamping were adopted to carry out the design of immersed tube foundation.In order to control the differential settlement of breakwater under sudden load,the load reduction design was carried out for the upper reconstruction structure of the joint in the section that undercrossing the breakwater,and the reasonable value of the element preload was given to realize the coordination of longitudinal settlement and stiffness transition of elements.It provides technical reference for the design and settlement control of foundation such as immersed tube undercrossing wharf,bank embankment and breakwater.