Root pile underpinning is used in deep foundations to distribute the weight of a structure to deeper, more stable soils. These piles are especially used in areas where the soil quality is poor, including expansive soils, soft soils, or saturated soils.
Root piles are less expensive, helping to solve subsidence in buildings. They are installed on each side of a wall using the existing foundations for support. This method can prevent costly concrete pads or beams, as well as site preparation expenses.
What are Root Piles?
Root piles are considered one of the most commonly used methods for underpinning, stabilising slopes, and supporting various significant and standard types. These piles are especially used in soils with poor stability, such as soils containing large boulders and rocks
Types of Root Piles
Steel Root Piles
Steel root piles are crafted from robust steel and are specifically used for difficult site conditions.
Concrete Root Piles
Concrete root piles are used in soils with moderate to good soil conditions and are constructed from reinforced concrete.
Hollow Stem Root Piles
Self-drilling piles are installed through hammering or striking, enabling rapid installation. Hollow stem piles can be found in different sizes based on the required weight capacity. They can bear loads of at least (210 to 1900) kN.
Process of Root Pile Underpinning Method
Piles are shaped using special drilling machines that reduce vibrations to nearby structures. They work by drilling a temporary steel casing into the ground with a special tool. This process is virtually vibration-free. Drilling fluid flows through the casing to cool the bit and then flows back outside, carrying away the debris to settlement tanks. To allow drilling rigs to work in tight spaces, short pieces of casing are joined together during boring. These specific drilling machines are designed to fit in restricted areas, and various are electric-powered, making them safe and functional.
Common Uses of Root Pile Underpinning Method
- Underpinning to existing structures:Mainly used in strengthening and providing support to the foundations of buildings that are becoming weak or unstable.
- Strip footing underpinning: Improves strength and stability by reinforcing long, continuous strip foundations.
- Upgrading of existing structural foundations: Helps in improving the load-bearing capacity of existing foundations so they can support higher weight.
- Supplementary support for upward or outward extension of existing structures: Adds foundational strength when a building is expanded with extra floors or extensions.
- Column base underpinning for adding additional storeys to buildings: Reinforces the foundations beneath columns so they can safely support the weight of additional floors.
- Stabilisation of old structures:Offers extra foundational support to the historic or older buildings without any major damage.
- Stabilisation of bridges and retaining walls: Helps in reinforcing bridges and retaining walls to avoid any movement or structural failure.
Advantages of Root Piles Underpinning Method
- The drilling machines are flexible and can be installed in different soil layers or go through underground difficulties in one operation.
- The grout mixture flows into the soil, fills empty space, and creates a strong connection between the pile and the ground.
- Root piles can be installed at any angle, even near existing buildings or industrial facilities.
- Special cutting tools allow piles to be installed through any underground difficulty.
- This piling method produces much less noise than most other piling methods.
- This process is vibration-free because the piles are installed using rotary drilling.
- The drilling machine can enter through regular doorways, and piles can be placed vertically up to 300 mm from an existing wall, measured to the pile’s centre.
Final Thoughts
The root pile underpinning method is an efficient way to strengthen foundations and provide long-term support for buildings on weak or difficult ground. It can be installed in small spaces, produces little noise and vibration, and works in various soils, making it suitable for many foundation repair projects. Whether you need to strengthen your existing building or improve old foundations, root piles offer a practical and cost-effective solution. They increase structural safety, improve the foundation’s load-bearing capacity, and make the structure more durable.