Due to the low bearing capacity of silt formations, uneven settlement of the stratum is also prone to occur during construction, and there are rollover accidents of pile drilling machines. In addition, the phenomenon of sucking drills, necking, and hole collapse frequently occurs in silt formations. Therefore, in the construction of silt formations, safety should be given top priority, to ensure that the pile drilling machine can operate in a safe and stable environment, and operators are required to operate with caution.
When constructing silt formations, first treat the ground surface and level it with thick steel plates or backfilled gravel soil to increase the surface bearing capacity and ensure that the rig can be constructed in a stable state.
The drill bit of the pile drilling machine can be a double bottom sand sand bucket; for small diameter holes, a single-door double bottom sand sand bucket can be used, and a body-open drill can be selected for drilling muddy soil with a certain viscosity. Or a straight auger with flowing holes. However, no matter which drilling tool is selected for construction in the silt layer, the flow holes of the drill bit should be increased or enlarged as much as possible to prevent excessive negative pressure at the bottom of the drill due to the non-circulation of the upper and lower liquid levels of the drill bit during the drilling process, which will cause suction Drill.
The operator is required to drill slowly in the operation mode, and the lifting and lowering should be slow and uniform, and the depth of each drilling should not be too large. The principle of "diligent lifting and less footage" should be adhered to each time.
If the method of lengthening the protective cylinder or drilling with the pipe is used to maintain the stability of the hole wall, the construction speed of the subsequent processes (hoisting the reinforced cage and poured concrete) must be accelerated, and the protective cylinder must be pulled out in time to prevent excessive time or pile holes It is difficult to lift the protective cylinder after it is filled with concrete.
For underwater drilling, the viscosity of the retaining mud should be appropriately increased, or an appropriate amount of clay blocks should be thrown directly into the pile hole, and then drill down in the soft soil section, and continue to drill without grinding for a while, so that the clay will be used to The wall of the hole is compacted to increase the thickness of the mud on the wall of the hole.