Positive circulation bored pile foundation construction technology
Content introduction 2. Leveling of the drilling rig working site: 1) Prepare the mud pit, and build a mud pit according to the volume of one pile to produce three times the mud volume. It is proposed to build a mud pit outside the dam, with a volume of 300~500m3, and a mud circulating tank of 40m3, and the sedimentation tank and mud pit must be connected in series...... 3 The pile casing shall be buried ② After the pile position is determined, the external pile casing shall be allowed to sink slowly into the mud by its own gravity. After it is stabilized, the channel steel shall be placed on the top of the pile casing, and then the excavator shall be used to press it into the solid soil layer at the bottom of the river bed for no less than 2m...... 3. The role of drilling construction mud in drilling is as follows: a. A large suspension pressure shall be generated in the hole to prevent hole collapse; b、 The mud leaks into the soil layer outside the hole. During drilling, due to the activity of the drill bit, a layer of cement is formed on the surface of the hole wall, which can protect the wall and cut off the water flow inside and outside the hole...... 4. The elevation of the fabrication of the reinforcement cage and the placement of the lifting reinforcement cage can be calculated from the elevation at the top of the mouth guard pipe. When placing, the design elevation of the pile top must be ensured, The allowable error is ± 100mm............ 5. After the concrete pouring starts, it shall be carried out continuously and the interval time for removing the tremie shall be as short as possible. When the concrete in the tremie is not enough, it should be poured slowly to prevent high-pressure air bags in the tremie. During the pouring process, special personnel shall be arranged to frequently detect the position of the concrete surface in the well bore...... 6. Pile hole quality detection: hole depth: determine the elevation of the pile casing before drilling, and use this as the base point to determine the hole depth according to the elevation of the hole bottom as required by the design. With the mark on the drill pipe as the benchmark, measure the hole depth with a measuring line and a steel ruler...... Prepared in 2012, 10 pages in total
