The project is located in Zhangmutou Town, Dongguan City, entrusted by Dongguan Shenzhen Energy Zhangyang Power Co., Ltd, our company undertakes the pile foundation construction of this project. The pile foundation is constructed by punched piles, a total of 622 piles, including 542 piles of Φ800mm and 80 piles of Φ1000mm. The pile is a friction end-bearing pile with medium-weathering bearing layer and the pile end is 1.0D into medium-weathering bearing layer. The work includes surveying and setting out, placement of casings, slurry preparation, drilling, steel cage production and placement, hole cleaning, concrete pouring, pile foundation completion data collection and finishing.
The project officially started from Feb. 15, 2019, and the construction task of existing working face was finished on Mar. 18, 2020.
The difficulty of this project is the control of sediment thickness, because individual piles have about 0.5m sediment at the bottom of the hole after placing the reinforcement cage, which leads to long time for secondary hole cleaning and seriously affects the construction quality and progress requirements. The reasons for the pile sedimentation are that the slurry index does not meet the requirements, the silt stratum contains silt and flow plastic state, the hole is not fully cleaned, and the placement of cages scratches the hole wall. According to the above characteristics, targeted measures were taken during the construction process: (1) timely digging out the slurry pool after drilling into the medium-weathering layer to reduce the slurry sand content, and the slurry index was controlled at 2% to 4% in the final hole. (2) Idle the drill at the bottom of the hole for 10-20 minutes before lifting the drill to prevent sedimentation at the bottom of the drill and the rock level. (3) Accurately align the center of the steel cage in the process of placing, and place the cage at a uniform speed to avoid cutting the hole wall by open welding. (4) Reasonable arrangement of work procedures, shortening construction time, compressing drilling stagnation time and timely concrete filling.
With the joint efforts of all the staff in the project department, we overcame all the technical and construction difficulties encountered in the project, organized and constructed with great care, and successfully completed the construction task, which has accumulated valuable experience for us in the future work.
