On the one hand, in order to meet the requirements of dam settlement caused by uneven dam foundation and temperature control during construction pouring, horizontal and vertical joints should be set at the dam body to divide the dam body into independent blocks; In addition, due to the long-term scouring, freezing and dissolution of the dam, local cracks or fractures appear in the dam. The above phenomenon has a great obstacle to the daily operation of the dam, but the consequences are very serious. Such as dam leakage, dam weathering and dam strength reduction. Therefore, people's property safety needs to be guaranteed, and the safety of dam body needs to be paid attention to. Therefore, we have discussed the crack repair technology of gravity dam.
1 Main application of grouting technology
1. 1 Curtain grouting technology for dam foundation grouting reinforcement is mainly used for dam seepage control and reinforcement. We designed two rows of curtain grouting holes, in which the row spacing and hole spacing should be designed according to the actual situation, and the depth of grouting holes should be more than 4 meters into the impermeable bedrock. In order to facilitate the implementation of the project, a special platform must be built downstream of the dam face for curtain grouting. At the same time, the joint between the dam surface and the platform must be provided with anchor rods, which can effectively ensure that the gravity dam and the grouting platform are connected into a main body.
1.2 Dam filling and reinforcement construction
For the anti-seepage reinforcement project of gravity dam, it is necessary to use steel mesh in the upstream of dam surface to engage in the use of concrete in order to build a practical anti-seepage structure. In this project, the shotcrete thickness must reach 0. 1 m, the spacing of each main reinforcement of steel mesh 1 m, the length of anchor rod must reach 0.8 m, and the synchronization must be arranged according to the quincunx spacing of one meter.
1.3 grouting reinforcement construction of overflow dam surface
When the overflow dam surface of gravity dam is strengthened, it must be supplemented by shotcrete with steel mesh. First, the mortar with cracks on the overflow dam surface must be chiseled and cleaned, and then the cracked reinforced concrete part should be removed and filled with acrylic mortar. At the same time, it is necessary to roughen the original reinforced concrete surface, install the anchor rod for fixing the steel wire mesh, and finally spray pebbles evenly on it, with the required thickness of 0.1m.
2 gravity dam grouting technology construction technology
2. 1 Construction preparation before irrigation and water storage of gravity dam
2. 1. 1 Determination of equipment parameters and grouting requirements
At the beginning, we should observe the state of the dam foundation. If we find water leakage, we should drill holes in this part. At the same time, we should be familiar with the structure and materials of the dam, and provide the basis for dam grouting according to the above observation results, so as to ensure the implementation of the dam project.
2. 1.2 Carry out the necessary hydrostatic test operation.
It is necessary to deeply understand the bedrock structure and the water permeability of the dam body, and carry out the necessary water pressure test, which also prepares an accurate basis for future construction and provides data for determining the density of magma and the amount of slurry entering the dam body in the future.
2. 1.3 Test before grouting
Grouting test is to test the distance radius, slurry density and some construction data of grouting before grouting. In order to prepare for the arrangement of holes and grouting in grouting construction. In order to have a clear understanding of the compressibility, permeability and grouting gravity of dam foundation and dam body, it can be tested according to the vibration test of grouting gravity. This can not only ensure that the original structure of the dam body is not destroyed, but also effectively ensure good grouting effect in the problem structures such as the inside of the dam body, gravel layer and bedrock cracks.
2.2 Introduction of grouting construction equipment for gravity dam
In the grouting process, the construction facilities mainly include three parts. Namely drilling equipment, grouting equipment and materials needed for grouting.
One of the important equipment is drilling equipment. Rotary hydraulic brick machine is necessary for grouting drilling. If the required drilling depth is relatively shallow, pneumatic drill can also be used for drilling.
Mixing machine, multi-cylinder grouting machine, grouting pipe, pressure grouting hose, rubber plug, hydrometer and pressure gauge constitute the grouting facilities of gravity dam. Here, the grouting machine must use the lifting facilities of the drilling rig itself, at the same time, the drilled hole should adopt the structure of circulating double pipes, and at the same time, the hole should be blocked with rubber plugs to form the grouting section. Finally, BW- 150 mud pump is used to transport the grouting section. Grouting materials mainly include ordinary portland cement, fly ash, sand, water, quartz powder and additives. The water-cement ratio of the slurry should be configured according to the actual situation of the dam body, and the water-cement ratio should change from dilute to thick with the change of water absorption per unit bedrock. The specific mud concentration shall be implemented in strict accordance with the specification requirements.
2.3 Introduction of Grouting Construction Technology for Gravity Dam
There must be strict standards for grouting steps. At the beginning, the water level of the dam is lowered below the standard water level, and then the dam is grouted. Grouting technology can only be carried out after the wall of the hole and the cracked part of the dam body are washed with clean water. We can use the method of combining geomantic omen to clean up, and pay attention to that the water pressure is less than the grouting pressure, that is, 3T4, until there are no stolen goods.
It is assumed that the grouting amount of a certain water-cement ratio reaches 400 liters under the condition that the grouting gravity and the slurry suction amount change little. It is necessary to use a more compact water-cement ratio grade; Assuming that the gravity of grouting suddenly increases or the amount of slurry absorbed suddenly decreases after changing the water-ash density of magma, we should immediately return to the original water-cement ratio example. Assuming that the original water-cement ratio still can't restore the original absorbed slurry, it is necessary to use the initial water-cement ratio sample for grouting or clean the grouting hole with clean water before grouting.
In the process of grouting, it is necessary to adjust the pressure according to the mud dosage, which is generally controlled at 0.0.2.0.3-0.5.0.6MPa, and the grouting pressure also needs to be intensified.
Methods: First, use 50% design pressure, and then gradually increase it according to the pulp suction situation until the end. If the pulp consumption is too large, the pressure should be reduced appropriately, and vice versa. After the pressure reaches the design pressure. The pressure can only be gradually increased to 0.05 MPa. At the same time, we should carefully observe the surrounding environment of multi-dams, corridors and dams.
2.4 Make records and quality inspection.
During the grouting step, the process should be recorded and analyzed regularly, and the quality of the implemented project should also be supervised. We will analyze the recorded data, carry out water pressure detection and grouting, and analyze the vibration detection and analysis instruments before grouting. After comparison, we will comprehensively evaluate the grouting quality.
label
Grouting technology is a key technology in the implementation of gravity dam protection, and it is also a necessary technology to ensure dam safety. In the process of grouting technology, the construction unit shall strictly implement various rules and regulations, at the same time ensure that the construction team is equipped with perfect working equipment, and regularly carry out professional skills training for the implementation personnel to ensure the accuracy of grouting for the construction personnel. Moreover, during this period, it is necessary to change and optimize the construction grouting according to the actual situation of the dam. During and after the construction, the project supervisor should conduct strict and meticulous inspection and have a sense of responsibility. The test shows that grouting technology is the most effective and feasible method to reinforce gravity dams. Strengthening the research and innovation of grouting technology of national gravity dam has great influence on the normal use of national gravity dam and the life, society and property safety of people around gravity dam.
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