(5) improper operation, colliding with the hole wall when lifting the drill bit or lifting the reinforcement cage.
4.
(2) When the deviation of the borehole exceeds the limit, the clay shall be backfilled and the borehole shall be drilled again after the deposit is dense.
(4) there is no continuous operation during drilling, the drilling stoppage time is long, and the water head in the hole cannot be maintained at 2m above the water level outside the hole or the groundwater level, reducing the pressure of the water head on the hole wall.
When shrinkage occurs, the drill bit can be used to sweep the hole repeatedly until the design pile diameter is met.
Treatment measures.
2.
Understanding the common quality problems of pile foundation is very important for engineering quality control.
After the hole cleaning is qualified, the concrete shall be poured in time.
(2) Check the drill bit frequently.
1.
Treatment measures (1) when encountering boulders and other obstacles, the percussion drill can be used to impact the hole forming.
During the drilling process, the drilling rig frame is unevenly deformed.
(2) The base seat of the water drilling platform is unstable and not in a horizontal state.
Repair welding shall be carried out in time in case of wear.
Quality problems and phenomena.
The pile casing shall be backfilled evenly to ensure the stability of the pile casing and prevent the infiltration of surface water.
Before the drilling rig is in place, the installation acceptance of the offshore drilling rig platform must be carried out, and the platform shall be firm, horizontal and stable.
(3) the drill pipe is bent and the joint is loose, resulting in a large shaking range of the drill bit.
Hole collapse 1.
(3) When drilling in the soft sand layer, the footage is too fast, the formation of mud retaining wall is slow, and the well wall seeps water.
The drill bit is stuck during drilling.
Preventive measures (1) do not set temporary access roads near the borehole, and large equipment operations are prohibited.
(4) when encountering obstacles near the old building, the drill head is squeezed to one side.
(3) When vibrating in water and sinking into the pile casing, the pile casing shall be sunk through the mud and permeable layer according to the geological data, and the joints between the pile casings shall be sealed to prevent water leakage.
(6) There are large equipment operations or temporary access roads near the borehole, which will cause vibration when vehicles pass.
(2) The lifting pulley groove on the top of the drilling rig, the chuck of the drill pipe and the center of the pile position of the casing shall be on the same vertical line, and the drilling rig shall be prevented from shifting or excessive swing during drilling.
(5) Uneven soft and hard soil layer, resulting in uneven stress on the bit, or encountering boulders, probe stones, etc.
(2) the reinforcement cage cannot enter the hole smoothly.
(9) During water supply, the water pipe shall not be directly flushed into the perforation wall, and surface water shall not accumulate near the orifice.
(7) when lifting the drill bit and lowering the reinforcement cage, it shall remain vertical and try not to collide with the hole wall.
When the hole detector is used to check the completion of the hole, the hole detector is blocked when it is lowered to a certain part, so it is unable to check the hole bottom smoothly.
Cause analysis (1) plum blossom hole, probe stone or shrinkage hole appear in the hole.
(2) the relative density of the mud is too small, resulting in low pressure of the water head on the hole wall.
(4) The drill pipe shall be inspected frequently, and the bent drill pipe shall be adjusted or discarded in time.
The diameter of a certain part of the borehole is less than the design requirements, or the hole diameter gradually shrinks from a certain part.
3.
(7) concrete is not poured in time after hole cleaning, and the placement time is too long.
Preventive measures (1) According to the geological drilling data and soil changes during drilling, if it is found that there is weak layer or plastic soil, pay attention to frequent hole cleaning.
2 Cause analysis (1) there is a weak layer in the geological structure.
(2) the plastic soil layer in the geological structure expands with water to form shrinkage cavity.
(4) After shrinkage occurs, the size of the drill bit after repair welding increases, the impact is too fierce, and the punch cone is absorbed..
Preventive measures (1) Before the drilling rig is in place, the construction site shall be leveled and compacted, and the drilling rig shall be adjusted to the horizontal state.
After repairing the drill bit with more wear, ream the hole to the design pile diameter.
Cause analysis (1) the drilling rig is not in the horizontal position, or the construction site is not leveled and compacted, resulting in uneven settlement during drilling.
(2) the drill bit is too fierce when lowering the drill bit, or the loose rope of steel wire rope is too long, so that the drill bit is dumped and stuck on the well wall.
Shrinkage occurs during the drilling process.
2.
(4) According to the geological exploration data provided by the design department and different geological conditions, appropriate mud specific gravity and mud viscosity shall be selected, with different drilling speeds.
3.
4.
(3) the drill bit is worn too fast and is not repaired in time to form shrinkage cavity.
3.
(3) during construction near the old building, detection shall be made in advance.
Quality problems and phenomena.
(5) When the water level changes greatly in flood season or tidal area, measures such as raising the pile casing, increasing the water head or using siphons shall be taken to ensure the relative stability of the water head pressure.
(2) When the pile casing is buried on land, 50cm thick clay shall be tamped at the bottom and around the pile casing, and attention shall be paid to tamping.
When the borehole passes through this layer, the weak layer compresses into the hole under the action of earth pressure to form shrinkage cavity.
(3) the falling stones or large tools during hole collapse block the drill bit.
At present, bored pile has become a common construction method for pile foundation in engineering.
During the drilling process, the drilling rig shall be checked frequently to ensure that the drilling rig is always in the horizontal state.
If obstacles are found during detection, percussion drilling shall be used for construction.
1.
Cause analysis (1) Water leakage occurs due to low mud consistency and poor wall protection effect; or water leakage occurs due to Shallow Embedment of the pile casing or loose sealing around; or insufficient thickness of the clay layer at the bottom of the pile casing and water leakage at the bottom of the pile casing, resulting in insufficient height of the mud head and reduced pressure on the hole wall.
Borehole wall collapse during drilling or after hole formation.
(6) continuous operation shall be carried out during drilling, and drilling shall not be stopped halfway without special circumstances.
Prevention and control of deflection of bored cast-in-place pile Quality problems and phenomena: (1) the hole is not vertical after completion, and the deviation value is greater than the specified L / 100.
(8) if the pouring preparation is insufficient, The hole cleaning shall not be carried out temporarily.
For example, when drilling in the sand layer, the mud consistency shall be increased, better slurry making materials shall be selected, the mud viscosity shall be increased to strengthen the wall protection, and the footage speed shall be appropriately reduced.
1.
(5) when using the percussion drill for construction, the stroke shall not be too large, and the secondary hole forming shall be used as far as possible to ensure the weight and straightness of the hole forming.
