1.The construction of cement fly ash crushed stone should follow the design requirements and site conditions, and comply with current national standards: (1) Long spiral drilling and grouting piles are suitable for cohesive soils, silty soils, and artificial fill foundations above the groundwater level; (2) Slurry wall drilling and grouting piles are suitable for cohesive soils, silty soils, sandy soils, artificial fill soils, gravelly soils, and weathered rock layers; (3) Long spiral drilling and pipe pump-pressing mixed material piles are suitable for cohesive soils, silty soils, sandy soils, and other foundations, as well as sites with strict noise and slurry pollution control requirements; (4) Pipe sinking and grouting piles are suitable for cohesive soils, silty soils, artificial fill soils, and non-compacted thick sand layers.
2. In addition to complying with the current national standards, the construction of long spiral drilling and pipe internal pump pressure mixed material piles, as well as pipe sinking and grouting piles, should also meet the following requirements: (1) During construction, the mixed material should be prepared according to the design ratio. The amount of water added to the mixer is controlled by the slump of the mixed material. For long spiral drilling and pipe internal pump pressure mixed material pile construction, the slump should be 180-200mm, while for pipe sinking and grouting pile construction, it should preferably be 30-50mm. After pile formation, the thickness of the floating slurry at the top of the pile should not exceed 200mm; (2) After drilling to the designed depth, for long spiral drilling and pipe internal pump pressure mixed material pile construction, the timing for lifting the drill rod must be accurately controlled. The volume of mixed material pumped should match the pipe pulling speed to ensure that a certain height of mixed material remains in the pipe. If encountering saturated sand or saturated silt layers, the pump should not be stopped to wait for more material. For pipe sinking and grouting pile construction, the pipe pulling speed should be controlled at an average linear speed, with the pipe pulling line speed controlled at about 1.2-1.5m/min. If encountering mud or silty soil, the pipe pulling speed can be appropriately slowed down; (3) During construction, the pile top elevation should be higher than the designed pile top elevation. The height above the designed pile top elevation should be determined based on the pile spacing, pile layout form, site geological conditions, and pile formation sequence, generally not less than 0.5m; (4) During pile formation, samples of the mixed material should be taken to make test blocks. Each machine should produce one set (3 blocks) of test blocks (cubes with a side length of 150mm) per day, which should be standard-cured for 28d, and their compressive strength should be measured; (5) During the construction of pipe pouring pile, the influence of newly constructed piles on already constructed piles should be observed. When the pile is found to break and disengage, the engineering piles must be static pressure one by one. The static pressure time is generally 3min, and the static pressure load is required to ensure that the broken piles are connected.
3.The foundation pit of composite foundation can be excavated by manual or mechanical means, or a combination of manual and mechanical means. When the mechanical and manual excavation is combined, the thickness of manual excavation reserved should be determined by on-site excavation to ensure that the fracture part caused by mechanical excavation is not lower than the elevation of the bottom of the foundation, and the soil between piles is not disturbed.
4.The static compaction method should be used for the laying of cushion layer. When the water content of the soil between piles under the bottom surface of the foundation is small, the dynamic compaction method can also be used.
5. During construction, the allowable deviation for pile length is 100mm, for pile diameter is 20mm, and for verticality is 1%. For a full foundation with piles laid out in a single row, the allowable deviation for pile positions is 0.5 times the pile diameter; for a strip foundation, the allowable deviation for pile positions perpendicular to the axis is 0.25 times the pile diameter, and for the direction along the axis, it is 0.3 times the pile diameter. The allowable deviation for pile positions in a single row of piles must not exceed 60mm.
Post time: Jun-04-2025