01. Application of slab-beam member reinforcement

The spillway tunnel of Nianzigou Reservoir in Yongji County, Jilin Province was built in the 1950s. The length of the spillway tunnel is 32.2 m and there are 3 holes. The cross-section size of each hole is 3.55 m × 3.4 m (B × H). The side walls and floor of the tunnel are reinforced concrete U-groove structure, and the top is reinforced concrete T-shaped beam cover. In 2003, the reservoir was reinforced by danger. As the earth dam roof was raised by 0.38 m, the T-beam reinforcement at the roof of the spillway tunnel did not meet the strength requirements after review. Through calculation, the design uses 300 g / m2 carbon fiber cloth adhered to the bottom of the full beam. Carbon fiber paste uses carbon fiber supporting resin (epoxy resin), the specific construction method is as follows:

Concrete surface treatment, that is, sanding the concrete surface, removing surface mortar and loose parts, and using a blower to blow away the floating ash. Prepare and apply the primer. Mix the primer with the main agent: curing agent, 2: 1 (mass ratio), stir for 3 to 5 minutes, and use until fully uniform. Formulate leveling glue and repair unevenness. Prepare and paint the dipping glue, brush the mixed dipping glue at the reinforcement position, and stick the carbon fiber cloth.

Carbon fiber reinforcement has an excellent effect on strengthening structures. It can retain the structural characteristics of the original building to the maximum, without increasing the weight of the structure, and without changing the appearance of the original building structure. The construction speed is fast and the engineering cost is low. Reinforcement of Nianzigou Reservoir's spillway tunnel took only 4 days, and investment of more than 40,000 yuan solved the potential safety hazard. At present, the spillway tunnel is operating well.

02. Application in Engineering Corbel Reinforcement

The Sanhe Sluice is located at the southeast corner of Hongze Lake and is the control gate of the Huaihe River channel. The design flow is 12 000 m3 / s. When reinforced in 1968, 127 bull-legs were added to the service door of the reinforced concrete structure upstream of the gate. The working leg of the corbel is 0.625 m, and the cross-section of the end of the corbel is 0.2 m × 0.24 m. Due to the unreasonable structural design of the corbel structure and the poor construction quality, the corbel concrete was damaged, spalled, and exposed from 1998. The traditional cement mortar method has been used for repairs many times, but the above phenomenon still occurs. In July 2004, the Sanhezha Management Office introduced carbon fiber to strengthen the corbels.

    The inspection door lifts the bull's leg and has both shear and bending effects. The original structure's failure mode is mainly shear failure, and part of it is damaged by insufficient reinforcement. According to the actual situation of the project, a combination of horizontal and vertical carbon fiber cloth is adopted during the reinforcement to improve the shear and bending resistance of the thigh. That is to say, the vertical corbel is axially pasted with a fully enclosed 300 g / m2 carbon fiber hoop to improve the shear performance of the corbel. A layer of carbon fiber cloth of the same type is glued on the top of the thigh in the axial direction, which acts as a tensile and hoop joint bead.

    The Sanhe Gate repair door reinforced with this technology has greatly improved the shear and bending resistance of the bull's leg. The shear capacity has been increased from 43.6 kN to 140.80 kN, and the bending strength has been increased from 42.9 kN · m. To 51 kN · m.

03. Application of hydraulic tunnel reinforcement

Hydraulic tunnels are subject to erosion, abrasion, and cavitation by water flow. With the increase of operating time, problems such as cracks, leakage, and aging will occur, which seriously affect the safety and durability of the structure. The traditional hydraulic tunnel reinforcement technology such as sprayed concrete or hanging concrete is equivalent to secondary lining of the tunnel. The construction is difficult, the cycle is long, the economic benefits are poor, and the cross section of the tunnel is changed. In addition, it will face new reinforcement problems, which will form a vicious circle again and again.

The irrigation and power generation channel of the Taohua River in Hunan is composed of pipes inside the dam, pressure tunnels and reinforced concrete pressure pipes. The reinforced concrete pressure pipe is an open-air pipe, the diameter of the irrigation pipe is 2.4 m, the wall thickness is 0.4 m, and the pipe length is 11.5 m. The diameter of the power generation tube is 1.75 m, the wall thickness is 0.3 m, and the tube length is 5.4 m. The water pipeline has been in operation for more than 30 years. The concrete of the reinforced concrete pressure pipeline is severely carbonized, the wall of the pipe is cracked and the water leakage is serious.

    The specific method of repairing and strengthening is to paste carbon fiber cloth and glass fiber cloth along the full length and full section of the reinforced concrete power generation pipe and irrigation pipe. The project started on December 15, 2002 and was basically completed on January 25, 2003. After more than a year of operation and inspection, the reinforcement effect is good, and the construction cost is reduced by 30% to 40% compared with the steel lining reinforcement.

The advantages of carbon fiber materials in tunnel reinforcement are very prominent, mainly as follows:

(1) Can be arbitrarily cut and reinforced various shapes (round or complex curved surface) structure.

(2) There is no need to use large-scale reinforcement tools for reinforcement and reinforcement, high engineering efficiency and fast construction speed.

(3) Corrosion resistance, impermeability and erosion resistance.

(4) The roughness of the carbon fiber cloth (0.007) is lower than the roughness of the concrete surface (0.014). The flow coefficient can be increased in the reinforcement section to improve the flow capacity of the pipeline.

(5) It can effectively close concrete cracks, thereby delaying or eliminating the appearance and expansion of cracks.

(6) The size and shape of the original section will not be changed after reinforcement.

(7) The reinforcement effect is good, and no subsequent maintenance is required, which is more economical.