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Abstract: The underwater concrete cast in the event of an accident, should take appropriate measures to prevent accidents as much as possible to expand or to loss of control to a minimum. This paper, a number of potential accidents analysis and the corresponding approach.
Key words: underwater concrete Accident
At present, the Construction of the Bridge over the pouring underwater concrete, although the underwater concrete has been many years of experience and lessons, but the man did not predict the course of construction accidents or frequent, large broken piles, and other small floating cage , to the construction impact and cause economic losses.
First, cut the ball card management
Underwater concrete is poured, the ball often produce cutting tube in the case, this occurs for two reasons.
1, cut the ball making unreasonable
Seven ball diameter and vessel diameter difference is too small, cut the ball or small stone mortar ago because of infiltration of the wall the ball between the catheter and cause blockage. If this is the case, the parties do not waste the amount of concrete under the premise of contingency approach are two:
with a certain length (usually longer than the funnel around 2m) diameter 20mm ~ 25mm steel and poke the ball plug, the whereabouts of concrete.
mechanical vibration of the concrete drop, this approach requires skilled operators to ensure that the whereabouts of concrete pipe buried in the place returned to normal.
2, concrete failure
If after opening is too small or mixing concrete slump uneven, with the cumulative process of coarse aggregate concrete sink and may lead to funnel mouth squeezed between dense and coarse aggregate to plug the funnel mouth, causing the ball after the concrete is difficult to cut whereabouts.
Remedy ibid, also should be noted: first, the general fighting to control the slump of concrete underwater slump of concrete specifications in the high limit is appropriate, to ensure a smooth cut the ball, the amount of stone can be properly controlled, such as cutting the ball to complete then carried out by mixing the normal mix. If not taken concrete measures whereabouts, time and length, only to give up this fight concrete, proper hole cleaning or air compressor to the bottom of the hole after the re-perfusion disturbance of concrete.
Second, infusion tube in middle
Due to mechanical failure (eg power failure) of the concrete stays too long in the catheter, or infusion time is too long, part of the initial setting of concrete has been the fate of resistance to the increase of blocking the conduit. This accident should adopt a prevention-oriented. Overhaul of equipment before perfusion. The extent possible, a continuous rapid perfusion, the hot season, mixing concrete in the amount of the initial infusion moderator, in order to avoid premature initial setting of concrete.
If the thickness of 3m within the pouring of concrete pipe and can not remedy appears cards to further treatment, it is recommended to stop pouring, pull out the catheter, suction machine with suction concrete, and re-clean hole reperfusion, or bring reinforcement cage, under heavy drill, Canada Large concentrations of drilling mud to the design elevation and discharge is poured concrete, then conventional methods Chiang Khong, re-perfusion, a small loss in exchange for high-quality works.
If the concrete is poured thick, heavy drill hole cleaning is not possible to replace the catheter only way to re-perfusion, but how to ensure continued after catheter replacement pile is worth studying.
3, pipe
Catheter can not pull the casting process, there are two possibilities:
1, reinforcement cage made of poor quality, some steel rings from inside the catheter was inserted after the longitudinal bars (which are usually floating cage). At this time should be positive and negative rotation catheter, catheter and reinforcement cage to separate and Habitat drilling center, then continue pouring.
2, duct depth is too large or the initial setting of concrete so that increased friction within and outside the duct, should be strictly controlled underwater concrete buried deep, not more than 6m, and not less than 1m. To prevent the initial setting of concrete, in addition to appropriate additional retarder should also be vibration outside the catheter.
Once buried place, which should identify the causes of what is possible, increase the pulling power roots catheter (but to prevent leakage of catheter pull), out this process should be positive and negative shake tube to make it easy to pull out.
4, floating cage
Floating in an accident in the process of pouring underwater concrete is not uncommon, for only half of the cage (ie, less than the length of reinforcement cage into the hole depth) of the bored piles is likely to occur. The reasons for this phenomenon and the concrete roof thrust related, but prevention is a factor in weak, so the cage should be taken under the measures is relatively fixed, as many welding rig several longitudinal bars at the base, increasing consolidation of power.
In the infusion process when approaching or entering reinforced concrete cage should be aware of. Close to the concrete surface and into the steel cage should be permitted to keep buried deep within the scope of, and continuously poured into the concrete to minimize the end I came out of concrete from the catheter after the impact of reinforcement cage; when the concrete surface into the steel cage a certain depth, the appropriate upgrade catheter to increase the depth of reinforcement cage, making concrete and steel reinforcement cage to ensure the bond strength steel cage not to float.
If a floating cage, should be as soon as possible, curb to go up, preferably more than 6cm in diameter around the reinforcement, steel reinforcement cage trap and then welded on the casing, and with steel or wood into a square mesh welded steel, and to suppress the protective tube This would also ensure that steel cage to float without excessive deviation.
Construction accidents occur, in order to ensure quality, should insist on prevention as a preventive measure principle. |
