Harm of long concrete pouring period of mechanical bored pile

How to prevent broken piles when pouring underwater concrete. 1, quality problems and phenomena 1) In the process of pouring concrete, the mud in the hole suddenly drops rapidly because the conduit is pulled out. 2) Due to poor sealing at the joint of the conduit, mud enters the conduit. If grouting is continued, mud interlayer will appear in the concrete. 3) Because the conduit is buried too deep, it takes too long for the concrete to block the conduit, or the concrete poured in advance takes too long to set, so the conduit cannot be lifted. 4) In nondestructive testing, there is mud layer in a certain part of the pile. 2. Cause analysis 1) When the slump of concrete is small, segregation or gravel size is small, the conduit is blocked during concrete pouring, and it cannot be dredged before the initial setting of concrete, so the conduit has to be lifted to form a broken pile. (Probably what you said. Because the concrete is mixed on site and no retarder is added, the setting time of concrete may be short, the mixing capacity may be insufficient, or the construction organization is not in place, resulting in insufficient concrete supply and discontinuous concrete pouring. 2) Due to the calculation error, the distance between the bottom of the conduit and the bottom of the hole is large, which makes the first batch of concrete unable to bury the conduit, thus forming a broken pile. 3) When the conduit is lifted, the bottom of the conduit is pulled out of the concrete surface due to measurement or calculation errors or blindly lifting the conduit, or the conduit mouth is in the mud layer or mud-concrete mixed layer, resulting in broken piles. 4) When lifting the conduit, the reinforcing cage is stuck in the conduit and cannot be lifted before the initial setting of concrete, which causes the concrete pouring to be interrupted and the pile is broken. 5) The leakage of conduit interface causes mud to enter the conduit, forming an interlayer in the concrete, resulting in broken piles. 6) The buried depth of the conduit is too deep, so it is impossible to lift or pull out the conduit, resulting in broken pile. 7) Due to other unexpected reasons, the concrete cannot be poured continuously, and the interruption time exceeds the initial setting time of the concrete, resulting in the failure to lift the conduit and the broken pile. 3. Precautions 1) Before the catheter is used, leak detection and tensile test shall be conducted to prevent the catheter from leaking. For the assembly number of each conduit, a review and inspection system shall be established after the conduit is installed. The diameter of conduit should be determined according to the pile diameter and the maximum particle size of stone, and large-diameter conduit should be adopted as far as possible. 2) When the conduit is lowered, the distance between the bottom opening and the bottom of the hole should not be greater than 40- 1250px, and the conduit should be buried at least 1m after the first batch of concrete pouring. In the subsequent perfusion process, the buried depth of the catheter is generally controlled within the range of 2-4m. 3) The slump of concrete should be controlled at 18-550px, and the workability should be good. If the pouring time is long, retarder can be added to the concrete to prevent the early pouring of concrete from initial setting and blocking the conduit. 4) When making reinforcing cages, butt welding is generally used to ensure smooth joints. When lap welding is used, it must be ensured that the weld will not form a staggered platform in the reinforcement to prevent the reinforcement cage from blocking the conduit. 5) When lifting the conduit, carefully calculate the length of the lifting conduit by measuring the pouring depth of concrete and the length of the removed conduit. Without measurement and calculation, it is forbidden to lift the catheter blindly. In general, only one catheter can be removed at a time. 6) Reserve key equipment and prepare sufficient materials to ensure continuous concrete pouring. 7) When the concrete blocks the conduit, the conduit can be pulled and shaken. When the blocked conduit is short, steel bars can also be inserted into the conduit to impact and dredge the conduit, or a vibrator fixedly attached to the conduit can vibrate and dredge the concrete in the conduit. 8) When the reinforcing cage is stuck in the conduit, try to rotate the conduit to make it separate from the reinforcing cage.