Six steps to remove the residue at the bottom of the pile during the construction of rotary drilling rig

1. The pile cleaning method is flexibly applied according to the different drilling rigs used. The hole cleaning method should be selected according to the pile hole specifications, design requirements, geological conditions and hole forming process. There are mainly positive circulation hole cleaning, pump suction reverse circulation hole cleaning and air lift reverse circulation hole cleaning. Among them, the use of suction mud machine to clean the hole requires few equipment, is easy to operate, and cleans the hole more thoroughly, but it should be used with caution in unstable soil layers. The principle is to use the high-pressure air generated by the compressor to blow out the mud residue by blowing into the suction mud machine pipe.

2. The hole can also be cleaned by mud replacement method, that is, after the drilling is completed, lift the drill bit to about 100~300mm from the bottom of the hole, continue to rotate, maintain the normal circulation of mud to absorb the sediment at the bottom of the hole, and gradually replace the suspended drilling debris in the hole. When cleaning the hole and discharging the residue, the water head height in the hole should be maintained to prevent the hole from collapsing.

3. The construction unit shall clean the hole twice. The first cleaning shall be carried out after the hole is formed; the second cleaning shall be carried out after the installation of the steel cage and the conduit is completed. The time of each cleaning should not be too long to prevent the hole from collapsing.

4. After the hole is formed, it should be checked whether the construction unit uses the hole forming drill to directly carry out the first positive circulation cleaning. When cleaning the hole, the construction unit first lifts the drill bit to 0.2~0.3m from the bottom of the hole, inputs mud to circulate and clean the hole, and the drill rod slowly rotates and moves up and down.

5. The first cleaning of the hole by pump suction reverse circulation is carried out by the construction unit using the pump suction reverse circulation system of the hole forming construction. When cleaning the hole, the construction unit first lifts the drill bit to 0.5~0.8m from the bottom of the hole, inputs mud to clean the hole, and the amount of mud input into the hole should not be less than the displacement of the sand and gravel pump to ensure sufficient mud replenishment. At the same time, supervise the construction unit to reasonably control the pump volume to avoid excessive suction and collapse of the hole wall.

6. After the hole is formed and cleaned, the quality of the hole is tested. During the first hole cleaning process, the mud viscosity, specific gravity and other indicators should be checked and measured; after the first hole cleaning, the hole depth and bottom sedimentation should be checked and measured. The hole depth shall not be less than the designed depth, and the sediment thickness shall be ≤100mm, and corresponding inspection records shall be formed. After meeting the requirements, the contractor is allowed to hang the steel cage and conduit.