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What Is A Concrete Casing? How Is It Used?

28/05/2021

Steel and concrete casing and liners play a crucial role in the construction of drilled shafts. Casings are tubes that are usually made of steel and that are joined by welding, or, in some cases, bolting. Liners are most often made from rolled metal plate, but are sometimes made from plastic or pressed fibers. Casings are used more often than liners, but both are incredibly important to maintaining the structural integrity of drilled shafts.

Installation of Casings

Casing is often placed into a large drilled hole and then seated into the underlying foundation to provide stability. Casing can be placed through a pre-drilled hole which may be constructed by drilling slurry or advanced without drilling if the soil will stand for a short time. Sometimes casings are used to further hole advancement. Telescoping casing is often used to perform this job when soil or rock friction is low.

Temporary Casing

Temporary casing is used to stabilize a drilled shaft excavation and is removed after or during the placement of fluid concrete in a shaft. Temporary casing is used to retain the sides of a borehole long enough for the fluid concrete to be placed. When the concrete has been filled to a level sufficient to withstand ground and groundwater pressures, the temporary casing is removed. Additional concrete is placed as the casing is removed to maintain the pressure balance. In some cases, temporary casing may be left in place.

The Size of Casings

If a casing size is not specified, most engineers will simply employ a casing that has an outside diameter (OD) of six inches larger than the drill shaft diameter. This is done to allow the passage of a drilling tool of proper diameter during final excavation of the borehole.

As mentioned, casings are sometimes employed as drilling tools themselves when rock excavation must be advanced below the casing in the dry rock. In such cases the end of the casing may have cutting teeth attached before a twisting or driving force is applied through the casing.

Casing Safety

Casing must be cleaned thoroughly following use to ensure resistance due to the motion of fluid concrete is as low as possible. When temporary casings are lifted, the drag on the column of concrete may cause the concrete to lift which can manifest a void in the concrete. Therefore, casings must be free from soil, lubricants and other detritus before they are used.

Contact Tebco

If you are looking for a casings or liners for use in your construction, mining, civil or infrastructure project, just call Tebco today to place an order. We have a vast selection of casings and liners available for sale. Check out our online store or call us on (02) 4677 2649 or reach out via our contact page to ask any questions or to make an order for our casings and liners today.