The basic tasks of rubber dam control

The basic task of control application is to make reasonable arrangements to give full play to the comprehensive utilization benefits of the rubber dam project under the premise of ensuring the safety of the rubber dam project. The management unit shall formulate control and operation plans and operating procedures according to the characteristics of the project and the operating conditions. After approval by the higher-level competent authority, the management personnel must strictly implement them.
(1) It is forbidden to run the rubber dam bag at super-high and over-pressure. That is, the water (or gas) filling must not exceed the design internal pressure. In general, water-filled dams are mainly controlled by the design dam height; while inflatable dams often use the design internal pressure of the dam bag as the main control index.
(2) One-way water-retaining rubber dams are strictly prohibited to be used for two-way water-retaining.
(3) The operation must be carried out according to the design and operation requirements, and attention should be paid to observation during operation.
(4) Dam bag inflation should be carried out in accordance with the following terms:
1) For the water-filled rubber dam anchored at the end, the vent hole should be opened when the dam bag is filled with water. When the dam bag is inflated to the specified height, if there is gas in the bag, the air can be driven manually, and then The vent is closed.
2) Water-filled pillow-type rubber dam, close the exhaust valve before filling with water. When the dam bag is inflated to 1/2~2/3 of the height of the dam, open the exhaust valve to exhaust, and wait until the gas in the bag is exhausted. Then close the exhaust valve.
3) Inflatable rubber dams, the condensed water and oil in the air compressor are removed before inflation. For inflatable dams used in winter in northern China, the condensed water in the bag should also be removed.
4) For higher rubber dams, when inflating the dam bag, it should be inflated in stages, and the residence time of each stage should not be less than 0.5ho. 80%. There must be a dedicated person to control the site so that necessary measures can be taken when abnormal phenomena are found.
5) For multi-span rubber dams, the sequence of inflating vertical dams or venting and collapsed dams, feasible operating methods should be worked out according to the specific conditions of the project. Generally, the collapsed dam bag should be filled symmetrically and slowly to adjust the flow pattern of the downstream stilling pool and river flow, so that no concentrated water flow or deflected water flow will occur.
6) The rubber dam project built on the sediment-laden river should be based on the principle of storing and discharging sand, grasp the law of sediment movement, and timely use the flood discharge opportunity to flush away the sediment. When the dam bag collapses and is covered by sediment to fill the dam again, depending on the degree of coverage, it can be gradually filled to the design height in multiple stages. If the covering layer is too thick, manual treatment is required.
7) During the overflow process of the rubber dam, the dam body is prone to vibration due to the influence of the fluctuating pressure of the water flow. Vibration intensity is mainly related to factors such as overflow water depth, downstream water level, flow pattern of water passing through the dam, and inflation height when the dam body overflows. Therefore, in addition to considering the smooth flow of the dam in the hydraulic structure layout design, attention should be paid to observation during operation to avoid the combined factors of overflow water depth, dam height, and downstream water level that cause dam bag vibration. When the dam body is found to vibrate during operation, measures such as adjusting the height of the dam and controlling the overflow depth of the dam crest can be adopted to reduce or eliminate the vibration of the dam bag. When the downstream water level increases, the collapse of the dam bag will easily cause floating, flapping and other phenomena. For this reason, water can be filled into the dam to increase the stability of the dam bag.
(5) In cold areas, rubber dams should be protected from freezing. For dams that do not operate in winter, empty the dam bag and the water in the pipe before winter to keep the rubber dam in a natural collapse state, and it is strictly forbidden for humans and animals to step on the dam bag. In winter, the frozen ice layer or snow layer can be used to keep the dam bag overwintering. The dam bag is frozen under the ice layer or covered with snow 0.3-0.5m thick, which is beneficial to the protection of the rubber dam, because the material of the rubber dam can not be brittle at -38-45°C. In winter, the rubber dam that keeps the water running can be used to break the ice in front of the dam during the freezing period! The method is to dig a small groove in front of the dam bag to prevent ice pressure from acting on the dam body. If the frozen layer is not deep, the icy layer in front of the dam pocket is not easy to freeze with the dam pocket due to the black heat absorption of the dam body and the smooth and curved surface of the dam. It should be pointed out that the height of the dam cannot be adjusted during the freezing period, and the dam can be erected or collapsed after the ice in the dam bag is dissolved. Under normal circumstances, the ice inside the dam melts first, and the ice layer outside the dam thaws later, so the dam height can be adjusted appropriately to overflow the ice.
(6) For the rubber dam anchored by wedges, the wedge is pulled up and loosened due to the frost heaving force generated by freezing. Therefore, when thawing every year, the anchoring structure of the dam bag must be comprehensively inspected, the wedges must be compacted again and the water filling test must be carried out to ensure the safety and reliability of the anchoring.

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