Underpinning is an important process in construction, civil engineering that aims at stabilizing and strengthening the existing foundations for a structure RECTIFY. This technique may be used when a building’s original foundation no longer supports the structure due to structural damage or changes in soil conditions. Understanding the importance of underpinning, and how to do it can help builders and property owners maintain the integrity of their structure.
Why Underpinning Needed
There are several factors that can require the underpinning or a foundation. A common reason for foundation underpinning is subsidence. This can happen due to erosion or natural soil shrinkage. Likewise, construction activity such as heavy machinery operations or excavation nearby can disturb the soil. This will compromise the stability of the foundation. If the building has been altered or added more floors, or heavier materials, it may require additional underpinning.
Methods for Underpinning
There are a number of methods to underpin, each one suited for different soil conditions and circumstances. The most common methods include:
1. **Mass Concrete underpinning**: The traditional method consists of excavating sections below the existing foundation. These sections are then filled with concrete. The process must be repeated several times until the entire structure is supported. This method is ideal for shallow foundations. It provides a solid and continuous support.
2. **Beam & Base Method** In this method, a reinforced-concrete beam is built below or next to the existing foundation. The beam transfers the loads to a series concrete bases or pilings placed at intervals. This method is ideal for deeper foundations as it distributes the load more evenly.
3. **Mini Piled Underpinning** – Mini-piles (small diameter piles) are driven deeply into the earth to support a foundation. This method can be used on sites with limited access, or in areas where soil conditions vary. Underpinnings with mini-piled piles can reach greater depths, and provide a robust support for structures that are heavy.
4. **Resin injection** is a new technique that involves injecting an extremely strong resin beneath the foundation. The resin expands to solidify, stabilizing soil and lifting foundations if necessary. This method requires less time and is less invasive compared to traditional underpinning.
Conclusion
It is essential to secure a foundation in order to maintain the safety and longevity of a structure. Underpinning can provide a solid base for structures that are already in place by addressing soil subsidence issues, increased loads, and structural damage. To determine which underpinning technique is best for their needs, builders and property owners should consult structural engineers. With the proper planning, underpinning will restore and improve any foundation’s stability.