Research On Rehabilitation Scheme With Floating Arch Cofferdam

At present, there are lots of hydraulic and hydropower projects established in China, which have produced huge social benefit and economic benefit in the national economy construction. But, some are suffered from aging and disaster for running for a long time; and some are unable to meet the requirements in present specification for the design degree of safety is on the low side. Therefore, it becomes a urgent matter to find a feasible rehabilitation scheme for the aged dams. However, at present, the two schemes, emptying reservoir and underwater construction, which are adopted in general, both could be done at huge costs. So, it is urgent to find a new rehabilitation scheme, which can create partial dry construction site to carry out thorough rehabilitation and keep the water in the reservoir meanwhile.Aiming at the rehabilitation of Fengman dam and based on several structures with extensive use in architectural and highway bridge engineering, for example, box beam structure and prestressing cable-arch structure, the paper put forward a sort of new rehabilitation scheme, with floating arch cofferdam.(1) Floating arch cofferdam is a shell structure. On the one hand, with the theory of arch, it transfer its water pressure to the upstream face of dam; on the other hand, it adopts basket type structure, resulting in that it is able to adjust the ups and downs of arch cofferdam by filling or draining water. What's more, it can be dragged to appointed site by tugboat to create another "dry construction site" again.(2) With ANSYS software, establish 3-D finite element model to carry out numerical analysis on the floating arch cofferdams in different line styles and work out the stress-strain situations of structures in different line styles and working conditions. And then carry out structure optimization based on the results. In the end, four sorts of feasible floating arch cofferdam structural shapes aiming at different working conditions are put forward.(3) Through analyzing the facing problems in the construction process of floating arch cofferdam, design a set of practical construction scheme, including prefabrication, transportation of box beam, assembling of arch cofferdam, dredge,skewback installation, emplacement of arch cofferdam, pump drainage, transfer of arch cofferdam, and the arch cofferdam construction in winter.Compared to emptying reservoir and underwater construction, if the rehabilitation scheme can be carried out, it can cut relative construction cost in large amounts in the precondition of ensuring the rehabilitation effect, which can supply a new approach for lots of hydraulic and hydropower rehabilitation projects in China. Therefore, the analytical studies on the new style of structure and the design of construction scheme have great reference value and practical significance.