Underpinning is a delicate construction process use to reinforce an existing foundation. To place a new foundation beneath an existing foundation to a greater depth. Underpinning foundation is a critical process and requires proper technique. Understanding and assessing the layers of the soil, the present state of the existing foundation, difficulties involving the complete foundation. The need depth, and the extent of the new foundation are all essential for the procedure to be execute successfully.
What are the Various Methods of Underpinning?
There are various methods of underpinning foundation which include:
Mass Pour Method
Due to its inexpensive cost and ability to withstand enormous foundation loads, the mass pour technique is one of the most commonly use methods. While this approach consumes a lot of material, it is advantageous because:
- It is the easiest to engineer,
- Does not require heavy gear, and
- Can allow for continuity of usage while building.
A strong, continuous concrete foundation is pour beneath the existing foundation in parts, using this technology.
Beam and Base Method
The beam and base underpinning foundation technique is technically a more sophisticate approach in which a reinforce concrete beam is built beneath, above, or in place of the current footing. The new beam in this system transfers the load to mass concrete bases, which distributes the load equally throughout the earth. While this system is more advance in design, its success is primarily dependent on the structural configuration of the building above the foundation.
Mini-Pile Method
When ground conditions are vary or access to the foundation area is restrict, the mini-pile method of underpinning foundation is employee. ‘Piles,’ or deep vertical structural components, are driven into the earth in drill holes deep enough to allow the piles to rest on stable soil in this way. The piles normally extend at least 15 feet below the earth but can reach depths of more than 50 feet, depending on soil conditions.
While this technology can overcome even the most difficult soil conditions, the engineering is more complex. The process may be fairly costly owing to the technical skills and specialize equipment require.
Jack Pile Method
When conventional underpinning foundation is expensive due to the availability of suitable bearing capacity subsoil at very deep levels, jack pile underpinning is employe. The main advantage of this technology is that it is flexible and vibration-free. This is because the pile’s depth may be simply adjust base on the subsoil condition. As it spans over the head of the pile cap, the existing foundation must be in good shape. After the hydraulic jacks have been remove, this pile cap is cast onto the head of the jack pile.
Pit Method
This needle-supporting structure consists of timber blocks or crib supports on both sides of the masonry wall, as well as screw jacks. The foundation pit is then excavate to the necessary depth for the new foundation, and the new foundation is erect inside the pit.
Once this step is complete, the process is repeat for the next alternate pit. During the construction, several crucial safeguards should be taken, such as raking shores or supports provide for strengthening weak walls. Cantilever needle beams are employe when there is a strong internal column, and the existing foundation is to be extende on only one side.
If you intend to perform structural work on your existing property, either as part of repair or renovation. It is critical that you hire a firm that has extensive experience and works closely with geotechnical engineers, structural engineers, and the Department of Buildings. This can go a long way to reduce the risk of the negative impact of underpinning foundation construction. Work on your property as well as the area that are adjacent to you.