Common quality problems in water conservancy projects and their treatment?

1. Appearance quality of concrete engineering: Common quality defects include honeycomb, pockmarked surface, staggered platform, skirt, mold running, etc.

The common quality problems mentioned above are caused by the imperfect quality management system of construction enterprises, few technicians, many workers and farmers, the contractor's reluctance to work and spend money, poor formwork deformation, inadequate support, soft supporting surface, unqualified formwork technology, no release agent, irregular vibration, inadequate pouring height, premature formwork removal and incomplete scraping when the formwork is reused.

Treatment method:

1. Demolition and re-pouring (after repair, it still affects and changes the stress state of the project, which is not conducive to structural stability and safe operation. For example, the repaired stress component size is smaller than the design size, the stress reinforcement cannot be straightened, the concrete protection does not meet the specification requirements, and the project position is prominent, which affects the image of water conservancy personnel. );

2. Finishing: manually chisel away the parts with appearance defects and see the aggregate. If the broken part exceeds 2cm, cement mortar (1: 1 ingredients) shall be used as the base first, and the slurry shall not be collected. A week later, plaster with pure cement slurry, and the color should be consistent with the original concrete as far as possible. Pure cement slurry should be mixed with 107 glue, and the proportion is generally not less than 10%. The side wall of spillway, stilling basin, pressure tunnel and other high-speed water flow parts should be trimmed with epoxy mortar or acrylic mortar. (The design compressive strength of acrylic mortar is R≥R≥35 MPa, flexural strength R≥8 MPa, and bond strength of old concrete is R≥R≥2.5 MPa). The reinforcement ratio of chemical steel bars is selected by the design unit. The above methods have been used to repair the projects under construction in our province, such as the spillway of Tian Bin Reservoir in Bai Yang, the gravity dam and workshop of Liao Fang Reservoir, the urban flood control project of Jingdezhen, Qinglianwei, etc., with good results. Among them, * * * The top of the external column of the spillway gate of Qinglianwei Drainage Station is 5cm, and the upper working bridge has been completed. Re-pouring after demolition will affect flood control and drainage. Finally, it is agreed that the lateral side of the column should be widened by 5cm, and the repair method is ① to cut the hair to see the aggregate, ② to hang steel wire mesh to connect with the column reinforcement, and ③ to set thin plates on both sides.

Second, the concrete slope protection project

1. Hexahedral precast block slope protection: Hexahedral slope protection is generally used for reservoirs in our province, which has the advantages of convenient manufacture, easy installation, good coincidence and easy repair. However, hexahedron slope protection is not suitable for the parts with long blowing range and heavy wind and waves in the lake area, and its continuous impact resistance is poor. The slope protection of William hexahedron in Jishan, duchang county has collapsed for years and once, covering a large area. The general quality defects of hexahedral precast slope protection are as follows: ① The precast site is uneven and not hardened. The bottom is uneven, condensed with mud, sand, grass and other impurities; (2) The steel formwork is not standardized, which leads to the inconsistency of precast size and seam width during laying, and affects the overall beauty and image; (3) No release agent is needed, and the corners of the precast slab are exposed and loose; (4) The tamping is not firm or the vibration is uneven, the top surface is not plastered, and the compressive strength of precast blocks can not meet the requirements; ⑤ Premature handling and random overturning lead to serious damage to the corners of precast blocks. (5) Slope regulation is not in place, excavation and filling are not in place, and there is no rolling along the slope. Where the paving is completed, the thickness of sand and gravel cushion varies, and the overall slope is ugly, so it is difficult for Wan Ru wave to rework.

Three, the reservoir culvert steel lining reinforcement

Large and medium-sized reservoirs in Jiangxi Province were generally built in 1950s and 1960s, and their design standards were not high. After decades of operation, most culvert pipes under the dam have been damaged, fractured, leaked and corroded. Almost all dam safety assessments determine that culvert pipes need to be rebuilt or strengthened. In central Jiangxi, the central government or the provincial government invested 50% in the reinforcement project, and the local self-raised funds were basically not in place, so the funds directly used for the project were very tight, so the design was optimized again and again. The following focuses on the quality problems and countermeasures of steel plate lining in the construction process.

① The design steel plate thickness is not enough; (2) the steel lining is artificially provided with split joints, which makes it difficult to stop water; ④ The anchorage welding between the steel plate and the original concrete reinforcement is not in place; ⑤ There is slag in the weld during construction; ⑤ Use backfill grouting instead of contact grouting; ⑦ Grouting pressure is not controlled; The grouting hole of the lining steel plate is not blocked or blocked; Pet-name ruby leakage area exceeds the specification requirements. Here are two examples of steel lining quality accidents. (Leping * * * Warehouse and Jiujiang Wharf) In order to avoid the quality accident of steel lining, the following points should be done in the design and construction: ① The thickness of steel plate should be selected according to the diameter of culvert, with the minimum thickness of 8 mm (d = less than 2 m) and the minimum thickness of 10mm (reference value) of 2 ~ 2.5 m; (2) the gradual transition section is generally not reinforced with steel lining; (3) steel lining generally does not have joints; ④. ⑤ Anchor bars should be added to the part where the original concrete circular tube size is not standard. ⑤ Grouting shall be carried out at different levels according to the design requirements (consolidation, backfill and contact). ⑦ Strictly control the grouting pressure. ⑧ Knock the steel pipe wall with a hammer, and check the gap area (less than 0.5m2, which is not concentrated, and re-grouting). Pet-name ruby after commissioning, close the gate and enter the hole for inspection.

Four. Vertical cutoff wall of dam

The common quality problems of dam vertical cutoff wall are as follows: ① The preliminary design work is not in place, the quality of dam filler and dam foundation has not been demonstrated, and the seepage prevention technology and model selected in construction design are relatively random, often the construction unit equipment comes first, so it is difficult to continue construction after drilling. The main phenomena are: a, the hole collapse is serious and it is difficult to form a groove; B, there are many stones in the original dam filler, so the water jet wall-building and thin-wall sawing technology can not form grooves; C, dam packing sticky, bit and grab shrinkage stuck. D, the cutoff wall is difficult to enter the bedrock, and there is still leakage in the dam foundation after reinforcement. To solve the above problems, it is often difficult to find out the geological conditions before choosing the wall-building technology. After the second equipment comes up, first drill the test slot and select the relevant parameters. If the dam body is loose and the hole collapse is serious, refer to the loess reservoir in Pingxiang City, first pour mud on both sides of the cutoff wall and rebuild the hole. For the third local landslide, the clay can be backfilled and compacted for seven days, and then the trench can be continued; For the fourth pair of shrinkage cavity sections, the catheter should be poured as soon as possible after the hole is formed, and individual blocked sections should be treated separately.

(2) The hole inclination exceeds the specified value, and the main reasons for the hole inclination are that the large-scale mechanical support is not in place, the dam surface is full of water, the high position is uneven, the machine is not concentric when installed, and the workers do not correct it when operating. To avoid eccentric holes, we must first level the ground and drain the water in the dam area; Secondly, it is necessary to reinforce the walking track of the drilling machine. Generally, sleepers are not needed, and concrete with a certain depth should be used for rigid support. Construction personnel should repair and correct the equipment in time and deal with the problems in time. ③ The treatment method of slurry leakage of high-pressure jet cutoff wall can refer to the method that curtain grouting is difficult to form holes. ④ The permeability of curtain grouting in dam foundation is greater than the design value, and there is only one treatment method, that is, intensive re-grouting. Until the requirements are met, the key to ensure smooth groove formation and no hole collapse is to stop the mud wall There is water in the tank and the water has lateral pressure, which can ensure that it will not collapse (except in special circumstances). Water is easily lost, so mud is used to protect it. In the construction process, the original dam body automatically produces mud during the slotting process, and it is not necessary to replenish mud with good viscosity. However, many construction enterprises are lucky. In order to ensure the smooth construction of cutoff wall and meet the quality standards, construction enterprises should do the following:

A, inspect the yard, select clay, do experiments and select parameters;

B, completes the mud pool;

C, installing a mud pump pipeline;

D, pay close attention to the change of water level in the tank and replenish mud in time;

E, regularly detect mud physical indicators.

Five, mechanical and electrical equipment installation

1, common quality problems: ① Civil design comes first, construction comes first, and electromechanical equipment orders comes later, so the embedded parts are not asked about the manufacturer's size and parameters, resulting in the frame elevation being either high or low; (2) The construction size of cast iron gate groove is inaccurate, so the gate cannot be pulled up and put down; (3) The bolts of the motor water pump are seriously eccentric, and some of them are only 2 ~ 3 cm away from the beam edge, which is easy to split; (4) The reserved hole size of the pump pipe on the pressure water tank, the second-stage concrete cannot be vibrated and compacted, and the steel pipe enters the pressure water tank to shoot water; ⑤ The faucet door in the pressure water tank has no embedded bolts, so it is drilled temporarily during installation. When the emergency stop, the faucet door falls off, the lake water flows backwards, and the motor rotates reversely, which is dangerous; ⑥ If the forebay is not carefully cleaned after the completion of the hydropower station, steel pipes, steel bars and iron parts will enter the guide vanes during the trial operation, and major accidents will be caused if they are not stopped urgently; All landowners main transformer installation height is not enough (especially the construction electricity), isolation range is not enough, resulting in personal injury; Today, the water-stop copper sheet and water-stop tape intersect with the steel bar, which leads to the steel bar passing through the water-stop body and reduces the water-stop effect.

2. Treatment method: ① Before civil construction, especially before pouring the pump beam, motor layer and formwork, be sure to ask the manufacturer about the length of the transmission shaft and the installation control elevation; (2) Before pouring the door slot, the portal frame must be installed vertically, and the lateral bolt holes must be reserved accurately. It is better to pour the second stage concrete than to leave a wider chute. Strictly control the deformation of portal frame. Strictly control the verticality of the winch screw to ensure that the winch is not suspended, rectified or opened; (3) all embedded parts should be corrected in time. If the hole has deviated, it must be reinforced with steel bars; (4) The second-stage concrete of the reserved hole of the pump pipe of the pressure water tank can't be vibrated, only steel bars can be drilled and the impervious body similar to the pier can be poured; ⑤ Special attention should be paid to the reinforcement of the temporary punching installation flap door in the pressure water tank. Generally, one more bolt is added to weld the two bolts into a whole.

For more information about project/service/procurement bidding, and to improve the winning rate, please click on the bottom of official website Customer Service for free consultation:/#/? source=bdzd