Introduces the reinforcement treatment of the thin-walled pier of the flood discharge gate of Jinweizhou Hydropower Station. The reinforcement project uses a combination of externally bonded steel plates and carbon fiber structural reinforcement to strengthen and repair the thin-walled piers of the spillway.

1 Project overview

In 2010, during the first regular inspection of the dam, it was found that there were cracks in the vicinity of the hydraulic cylinder support of the flood discharge gate pier. After inspection, there were cracks on 23 piers. Some piers have ten, and some piers have more than 20, a total of more than 300. Most of the cracks are vertical and perpendicular to the plane of the pier. A few are inclined cracks with an inclination angle of 30°-45°. The length and shape of some cracks on both sides of the same pier are suspected to be penetrating cracks. If allowed to develop, it will have a greater impact on the pier structure, so the pier must be reinforced.

Since there is no bearing structure around the Qianzha Pier, the load on the pier cannot be transferred. If the old gate piers are demolished and rebuilt, not only the gate piers must be rebuilt, but the overflow gates and opening and closing systems must also be redesigned and constructed, which will have a long impact time and high engineering costs and large losses. If the cross-section of the gate pier is enlarged to increase the bearing capacity, the flood discharge capacity will be reduced. Only the hoist can be used continuously, and the gate needs to be re-manufactured. This scheme is complicated to construct, takes a long time, and has high engineering costs and is difficult to implement.

Taking into account the safe and stable operation of the Jinweizhou Hydropower Station in the future, and will not affect the project benefits, the reinforcement and reinforcement of the flood discharge gate piers should follow the following basic principles.

(1) The plan must be economical, reasonable and convenient for construction

Full consideration should be given to the current situation of the pier and the force characteristics after reinforcement, and the overall analysis of the pier should be carried out to ensure that the pier has a clear force transmission line and reliable structure after reinforcement. Comprehensive economic indicators should be considered, and effective measures should be taken in plan design and construction organization to shorten the construction period and reduce the impact on the environment and adjacent facilities.

(2) Make best use of the bearing capacity of the original pier

During reinforcement and reinforcement, the shape of the pier should be kept as much as possible to reduce damage

2 Reinforcement technical solution

Based on the above analysis, the reinforcement treatment of the thin-walled gate pier of the flood discharge gate of Jinweizhou Hydropower Station can be implemented by sticking steel and carbon cloth. That is, the shallow groove is reinforced by a combination of sticking strip steel plate and sticking carbon fiber cloth.

The specific implementation plan is: sealing the cracks of the gate piers with a grouting glue. For the gate piers with insufficient fan-shaped steel bars, the shallow grooves are bonded with strip-shaped steel plates to strengthen and reinforce the tensile strength. For pier concrete cracking, use carbon fiber cloth to reinforce it. The surface of the gate pier is reinforced with polymer cement mortar for protection.

1) Surface treatment of the gate pier

2) Unloading of gate piers: In order to ensure the coordinated force, the gate piers should be fully unloaded before reinforcement.

3) Externally glued strip steel plates: stick strip steel plates on one side of the gate pier, about 15 pieces of the stilling pool and apron sections, and about 21 pieces of the flat-bottom gate section

4) Paste carbon fiber cloth: Paste carbon fiber cloth on the surface of the pier

5) Surface protection: After the carbon fiber cloth is pasted, paint a certain thickness of polymer cement mortar on the surface of the pier to protect the inside of the pier

Project summary

The stress analysis is carried out according to the material mechanics method, and the calculation results show that the pier structure can meet the requirements after the reinforcement of the thin-walled pier of the flood discharge gate of Jinweizhou Hydropower Station. Sticking steel plate and carbon cloth on the outside can effectively solve the problems of insufficient bearing capacity of thin-walled gate piers and concrete cracking