Precautions and common problems when using segmented casings

When using segmented casing in pile foundation rotary drilling, the following matters need to be noted:

1. Preparation before casing burial

- Geological survey:

Before burying the casing, the geological conditions of the construction area should be surveyed in detail to understand the soil layer distribution, groundwater level, soil bearing capacity and other information in order to select the appropriate casing type and burial method.

- Casing selection:

According to the geological survey results, select casing materials that meet the requirements to ensure that their strength, rigidity and sealing meet the construction requirements.

The casing length should be adapted to the construction depth and have sufficient guiding performance to prevent eccentric holes.

- Casing inspection:

Before using the casing, carefully check the quality of the casing, including wall thickness, surface finish and whether the connection parts are intact. At the same time, check whether the positioning pins and spiral lock fasteners between the casings are firm to ensure the stability and sealing of the casing during rotary drilling.

- Equipment inspection:

Before construction, the rotary drilling rig and its supporting equipment should be fully inspected to ensure that they are in good working condition.

Check whether the connection of equipment such as casing driver, pipe twister or full-rotation drilling rig is firm and the operation is flexible.

2. Precautions during casing burial

- Accurate layout:

Use positioning control piles for layout to ensure accurate casing burial position.

After the casing is hoisted into the hole, the center of the casing should be found and marked with a crosshair at the top or bottom of the casing to adjust the casing position.

- Verticality control:

When burying the casing, the verticality of the casing should be checked with tools such as a level ruler or plumb ball to ensure that it is perpendicular to the ground.

If the casing is found to be deflected, it should be adjusted and re-fixed in time.

- Layered backfilling and compaction:

Backfill clay or cement mortar symmetrically and evenly around the casing, and compact it in layers to achieve the purpose of fixing the casing position.

During the compaction process, avoid hitting the casing to prevent its deformation or displacement.

- Water level control:

If the groundwater level in the construction area is high, effective measures should be taken to lower the groundwater level to prevent water from entering the casing.

During the casing burial process, the water level in the casing should be checked regularly. If the water level rises, it should be drained in time.

- Prevent collision:

When the drill bit of the rotary drilling rig rises and falls, it should be prevented from colliding with the casing to avoid damaging the casing or affecting the construction quality.

If the drill bit collides with the casing, the machine should be stopped immediately for inspection and adjustment.

- Clean up debris: Clean up debris such as soil, sand, etc. on the inner and outer walls of the casing frequently to keep the casing clean and smooth.

- Check the sealing: Check the sealing of the casing regularly. If the seal is damaged or loose, it should be replaced or tightened in time.

- Check the position and verticality of the casing:

After the casing is buried, the position and verticality of the casing should be checked again to see if they meet the requirements.

If the casing position is found to be offset or the verticality does not meet the requirements, it should be adjusted in time.

3. Post-maintenance and care

- Lubrication and maintenance: Regularly lubricate and maintain the casing to reduce wear and friction resistance. Special lubricants or greases can be used to apply to the connection and sliding parts of the casing.

- Anti-corrosion treatment: Apply anti-corrosion agent or other anti-corrosion treatment on the surface of the casing to extend the service life of the casing.

- Storage management: After the construction is completed, the casing should be properly stored to avoid long-term exposure to harsh environments. At the same time, the casing should be regularly inspected and maintained to ensure that it is in good standby condition.

4. Response to special situations

- Encountering hard formations: When encountering hard formations, the drilling parameters of the rotary drilling rig should be appropriately adjusted to avoid forced drilling and damage to the casing.

- Encountering quicksand layers: When drilling in quicksand layers, the water level in the casing should be kept higher than the groundwater level to prevent quicksand from flowing into the casing and affecting construction.

- Encountering abnormal situations: If abnormal conditions such as deformation, fracture or loose connection of the casing are found, the machine should be stopped immediately for inspection and corresponding treatment measures should be taken.

In the process of using segmented casing, some problems may be encountered. The following is an analysis of these problems and corresponding solutions:

- Casing tilt or displacement:

When burying the casing, if the soil is not dense or the water level difference is too large, the casing may tilt or shift.

A loose connection between the casings or loose bolts may also cause the casing to shift.

Prevent casing tilt or shift:

Before burying the casing, the bottom of the pit and the surrounding soil should be compacted in layers to ensure that the soil is dense.

During the burial process, the position and verticality of the casing should be checked regularly, and corrected with tools such as a level ruler or a plumb ball.

Ensure that the connection between the casings is tight and the bolts are firmly installed.

- Casing damage:

When the drill bit of the rotary drilling rig rises and falls, if the operation is improper, it may collide with the casing, causing casing damage.

During use, if the casing is hit or hit by hard objects, it may also be deformed or damaged.

Prevent casing damage:

When the drill bit of the rotary drilling rig rises and falls, it should be operated slowly to avoid collision with the casing.

During the use of the casing, it should be prohibited to use hard objects to knock or hit the casing.

If the casing is found to be damaged, it should be replaced or repaired in time.

- Poor casing sealing:

The failure to form an effective sealing space between the casing and the soil may cause groundwater infiltration and affect the construction quality.

Poor sealing at the casing joint may also lead to poor sealing.

Improve casing sealing:

When burying the casing, ensure that an effective sealing space is formed between the casing and the soil.

Use sealing materials at the casing joints to ensure that the joints are tightly sealed.

If the casing is found to have poor sealing, measures should be taken in time to repair it.

- Poor hole quality:

During the casing burial process, if the verticality and position of the casing are not effectively controlled, the hole quality may be poor.

The rough inner wall of the casing or the presence of impurities may also affect the hole quality.

Improve the quality of drilling:

During the process of casing burial, the verticality and position of the casing should be strictly controlled.

Before drilling, the inner wall of the casing should be cleaned and inspected to ensure that the inner wall is smooth and free of impurities.

If the drilling quality is found to be poor, timely measures should be taken to remedy it.

Then how is the good-quality Unimate casings produced? There are 8 processing procedures:

- Raw material selection: Select suitable steel, usually high-strength, wear-resistant alloy steel.

- Cutting and blanking: Cut the raw steel into the required length according to the design requirements.

- Rolling: Roll the cut steel plate into a tube through a roll machine.

- Welding: Weld the joints of the roll to ensure that the welds are firm and sealed.

- Joint processing: Process the casing joints according to the drawings, and perform heat treatment after machine processing.

- Welding: Butt weld the welded barrel and joint

- Straightening: Straighten the welded casing to ensure its straightness.

- Quality inspection: Perform dimensional inspection to ensure that the quality of the casing meets the requirements.

- Pack the qualified rotary drilling casing for storage and transportation.