The construction of CFG pile drivers should be selected based on design requirements and site conditions, and implemented in accordance with relevant domestic regulations.
(1) Suitable for cohesive soil, silt, and artificially filled foundations above groundwater level;
(2) Suitable for foundations with clay, silt, sand, artificial fillers, gravel (gravel) soil, and weathered rock distribution;
(3) Suitable for cohesive soil, silt, sandy soil and other foundations, as well as places with strict requirements for noise and mud pollution;
(4) Suitable for manually filling cohesive soil, silt, silt and foundation, without dense thick sand layers.
2. In addition to current national regulations, the pile structure using pump pressure mixture in long spiral drilling pipes and the pile structure using sinking pipe grouting should also meet the following requirements:
(1) During the construction process, the mixture should be prepared according to the design ratio and the amount of water added to the mixer should be controlled based on the slump of the mixture. The slump of the pile body structure of the pump pressure mixture in the long spiral drilling pipe should be 180-200mm, and the slump of the pile body structure of the sinking pipe should be 30-50mm, with the thickness of the floating slurry on it. The top of the pile after completion shall not exceed 200mm;
(2) After drilling to the design depth, the time for pulling out the drill rod should be precisely controlled. The pumping capacity of the mixture should match the traction speed to ensure a certain height of the mixture in the pipeline. When encountering saturated sand or silty soil layers, do not stop the pump and wait for the material. The pulling speed of pile sinking construction should be controlled based on a uniform linear speed, and the pulling speed of pipelines should be controlled around 1.2-1.5m/min. If it is muddy or muddy soil, the traction speed can be appropriately reduced;
(3) During the construction process of the CFG pile driver, the pile top elevation should be higher than the design pile top elevation, and its length should be determined based on the pile distance, pile layout, on-site geological conditions, and pile formation sequence, generally not less than 0.5m;
(4) During the piling process, a set of (3) test blocks (cubes with a side length of 150 mm) should be made for each machine within one day, and the compressive strength should be measured 28 days after standard curing;
(5) During the process of pile sinking and grouting, the impact of new construction piles on the construction piles should be observed. When it is found that the pile has broken and fallen off, static pressure must be applied one by one to the engineering piles. The static pressure time is generally 3 minutes and should withstand the static pressure load to ensure the connection of the broken pile.
3. The foundation pit of composite foundation can be excavated manually, mechanically, or manually. In the process of mechanical and manual joint excavation, the retained thickness of manual excavation should be determined based on on-site excavation to ensure that the fractured part of the pile caused by mechanical excavation is not lower than the elevation of the foundation bottom, and the piles between the soil are not disturbed.
4. The static fastening method is used for laying the cushion layer, but dynamic fastening method can also be used when the soil moisture between the piles at the bottom of the foundation is low.