Do you know double-layer core barrel?

On the bauma China exhibition in last month, our double-layer core barrel attracted much attention and many customers were very interested in it. Then do you know what a double-layer core barrel is?

The double-layer core barrel consists of two layers of inner and outer barrels. This unique design structure gives it significant advantages in pile foundation rotary excavation. The inner barrel is responsible for drilling, sampling and breaking rocks. Its material and design are usually more refined to ensure the stability and efficiency of the drilling process. The outer barrel plays a protective and guiding role, preventing the inner barrel from being interfered and damaged by external debris during the drilling process, while ensuring the accuracy of the drilling direction.

Working principal

1. Drilling process:

Driven by the rotary drilling rig, the double-layer core barrel starts to rotate and exert downward pressure.

The drill teeth of the inner barrel first contact the rock or soil layer, and crush the rock or cut the soil by rotating and applying pressure.

The crushed rock or soil is collected by the inner barrel and carried to the hole through the gap between the inner and outer barrels.

2. Deslagging process:

When the inner barrel is full of drill cuttings, the rotary drilling rig lifts the drill rod, and the double-layer core barrel continues to rotate.

During the rotation process, due to the centrifugal force, the drill cuttings are thrown to the inner wall of the outer barrel and brought to the hole as the drill rod is lifted.

At the hole, the drill cuttings are discharged through a specific deslagging device, thus completing a complete drilling cycle.

3. Protection and guidance:

The outer barrel plays a role of protection and guidance during the drilling process. It can prevent the inner barrel from being disturbed and damaged by external debris, while ensuring the accuracy and stability of the drilling direction.

When encountering complex geological conditions, such as uneven soil layers or rock layers containing a large amount of debris, the outer drill tube can provide better protection and support.

Advantages

1) Efficient drilling: The design of the double-layer drill makes the drilling process more efficient. The inner barrel is responsible for drilling sampling and breaking rocks, while the outer barrel plays a role of protection and guidance. This design helps to reduce energy loss during drilling and increase drilling speed.

2) High core recovery rate: Due to the special structure of the double-layer drill, it can collect cores and drill cuttings more effectively. The inner barrel can tightly wrap the core during the drilling process, reducing the loss of cores and thus improving the core recovery rate.

3) Strong adaptability: The double-layer drill is suitable for a variety of geological conditions, including soft soil, sand, gravel layer and medium weathered rock layer. This wide applicability makes the double-layer drill more flexible in pile foundation rotary drilling and can cope with drilling needs under different geological conditions.

4) Good stability: The outer barrel plays a role of protection and guidance during the drilling process, which can prevent the inner barrel from being disturbed and damaged by external debris. This design helps maintain the accuracy and stability of the drilling direction and reduce drilling deviations and failures caused by changes in geological conditions.

5) Strong slag discharge capacity:

The gap between the inner and outer layers of the double-layer core barrel can carry and discharge the drill cuttings more effectively. During the drilling process, the drill cuttings are collected by the inner layer of the barrel, carried to the hole mouth through the gap between the inner and outer layers of the barrel, and discharged through a specific slag discharge device. This strong slag discharge capacity helps to keep the hole clean and unobstructed, and improve drilling efficiency.

6) Long service life:

Due to the structural design and material selection of the double-layer core barrel, it usually has a long service life. The drill teeth of the inner layer of the barrel are made of wear-resistant materials, which can resist wear and corrosion during drilling, thereby extending the overall service life of the drill bit.

Of course, it also has some disadvantages

1) Weight and size: Due to its special design and structure, double-layer core barrels are usually heavier and larger than ordinary core barrels. This may result in more time and resources being required during transportation, installation and use. The larger weight and size may also limit its use in certain narrow or complex construction environments.

2) Higher cost: The manufacturing materials and processes of double-layer core barrels are relatively complex, so their cost is usually higher than that of ordinary core barrels.

3) High requirements for operating technology: Due to the relatively complex structure and working principle of double-layer core barrels, operators need a higher level of technology and experience to ensure their correct and efficient operation.

4) Maintenance difficulty and cost: The maintenance of double-layer core barrels is relatively complex and requires regular inspection, cleaning and repair.

This may increase maintenance costs and time and may affect construction efficiency.

5) Applicable conditions restrictions: Although double-layer core barrels are suitable for a variety of geological conditions, their performance may be limited in certain extreme or special geological environments.

For example, in very hard rock layers or highly viscous soft soils, the drilling efficiency of double-layer core barrels may not be as good as other types of drill bits.

6) High site requirements:

Due to its weight and size, double-layer barrels have higher requirements for ground bearing capacity and space at the construction site.

In construction environments with insufficient ground bearing capacity or limited space, additional reinforcement measures or adjustments to the construction plan may be required.

Application

1. Application geological conditions

1) Broken soil and gravel layers:

Double-layer core barrel is suitable for geological conditions of broken soil and gravel layers. The design of the inner and outer layers of the barrel enables the drill cuttings to be carried and discharged more effectively, while protecting the inner layer of the barrel from interference and damage from external debris.

2) Moderately weathered rock formations:

Double-layer core barrels also show good drilling performance in moderately weathered rock formations. Its drill teeth can break rocks in steps and release the rock confining pressure through ring cutting, thereby achieving the purpose of breaking and coring.

2. Application scenarios

1) Bridge pile foundation construction:

Double-layer core barrels are often used for drilling and coring operations in bridge pile foundation construction. Its efficient drilling ability and high core recovery rate help ensure the quality and stability of the pile foundation.

2) High-rise building pile foundation construction:

Double-layer core barrels are also widely used for high-rise building pile foundation construction. Under complex geological conditions, it can maintain a high drilling speed and stability to meet construction requirements.

3) Other pile foundation projects: In addition to bridges and high-rise buildings, double-layer core barrels are also suitable for other types of pile foundation projects, such as ports, docks, tunnels, etc. In these projects, double-layer core barrels can play their unique advantages to ensure construction quality and progress.

Compare with general core barrel, double-layer barrel is better in what ways?

1. It consists of two layers of barrels: the inner barrel is responsible for drilling, sampling and breaking rocks, while the outer barrel plays a role in protection and guidance. This design enables the double-layer core barrel to carry and discharge drilling residue more effectively during the drilling process, while protecting the inner barrel from interference and damage from external debris.

2. Adopt the "squeezing" drilling idea, that is, crush the broken and pebbles of different sizes in the barrel and bring them out of the hole. This drilling method greatly improves drilling efficiency and the service life of drill teeth.

Due to the synergistic effect of the inner and outer layers of barrels, the double-layer core barrel can maintain high stability and accuracy during the drilling process.

3. Suitable for a variety of geological conditions, including soft soil, sand, pebbles and weathered rock formations. It has the advantages of efficient drilling, high core recovery rate, strong adaptability and good stability. In pile foundation rotary excavation, the drilling speed and quality can be significantly improved, and the construction cost can be reduced.