Method for converting temporary diversion tunnels into permanent flood discharge facilities

Abstract

The invention provides a method for reconstructing a temporary diversion tunnel into a permanent flood discharge facility. The method comprises the steps that firstly, an entrance of the original diversion tunnel (1) is blocked; secondly, an entrance curve section of the diversion tunnel and a straight section behind the entrance curve section are reconstructed into an energy dissipation pressure forebay (2), and the wall surface of the tail end of the energy dissipation pressure forebay is provided with a jet flow outlet (3), so that the diversion tunnel section behind the outlet becomes a free flow section (6) of a permanent flood discharge tunnel, wherein the straight section is at least five times longer than the entrance curve section; thirdly, at least one flood discharge tunnel (4) is newly constructed at the position above the entrance of the blocked diversion tunnel, wherein the bottom surfaces of entrances of the newly constructed flood discharge tunnels are at least 2m higher than the highest position which silt silting at the entrances can reach; and fourthly, each newly constructed flood discharge tunnel (4) is connected with the energy dissipation pressure forebay (2) through at least one connecting pipeline (5), and the axes of the newly constructed flood discharge tunnels (4) intersect with the axis of the energy dissipation pressure forebay (2). By means of the method, not only can the diversion tunnel with the planar curve section be smoothly reconstructed and utilized, and investment is saved for a whole water conservancy and water power project, but also the energy dissipation effect can be improved, and the service life of a building is prolonged.

Description

technical field [0001] The invention belongs to the technical field of reconstruction of water conservancy and hydropower facilities, and in particular relates to a method for rebuilding a temporary diversion tunnel in a water conservancy and hydropower project into a permanent flood discharge facility. Background technique [0002] During the construction of water conservancy and hydropower projects, it is often necessary to temporarily block the river to facilitate construction in the original river course. At this time, some temporary buildings need to be built to divert the water in the river to the downstream of the construction area. Diversion tunnels are often built Such a temporary structure. In order to save engineering investment, the shorter the length of the diversion tunnel, the better, which leads to the existence of plane turning sections in the diversion tunnel. For such temporary drainage structures, they are generally abandoned after the construction of th...

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Problems solved by technology

In order to save engineering investment, many projects in recent years have converted such temporary diversion tunnels into permanent open flow flood discharge tunnels (Sun Shuangke et al., Hydraulic problems of diversion tunnels converted into swirling shaft type flood discharge tunnels under the condition of high water level downstream Research, 2000, Journal of Water Conservancy, 10, 22-27; Li Guixin et al., Research on the scheme of converting the diversion tunnel of Gongboxia Hydropower Station into a swirling flood discharge tunnel, 2002, Hydropower, 8, 41-44), but this reconstruction has the following Problems in three aspects: 1) Since the water level in the reservoir area is generally relatively high, the water flow velocity during flood discharge is also very high, and there are great difficulties in high-speed open flow turning, which will cause rapid current shock waves and other phenomena, and the water surface outside the turning section will be damaged. It will rise greatly, but the water surface inside will decrease. In severe cases, the water flow will roll in the cave, causing the water flow to be chaotic, and the air channel on the roof of the cave will be closed, causing damage, making it difficult to rebuild and utilize the diversion tunnel with a flat turning section.

2) Since the entrance of the diversion tunnel must meet the requirement of being able to pass water in dry seasons, the location is relatively low. After the project is completed, the sediment will accumulate in the reservoir. When the entrance of the diversion tunnel is used as the entrance of the permanent flood discharge tunnel, a large number of The sediment will move with the water flow during flood discharge, which will cause serious wear and tear damage to the flow wall

3) If the existing reconstruction method is used in a project with a relatively high standard for flood discharge, the roof of the tunnel will be submerged and unstable during operation, resulting in poor energy dissipation effect of the reconstructed flood discharge tunnel and potential safety hazards in operation

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