CHANCE® Helical Underpinning
Foundation subsidence issues in the UK requiring underpinning technology continue to be prevalent and an important expenditure for insurance companies and loss adjusters. Given the age of the building stock, varying geology, proximity to tree roots and extreme summer droughts, more and more structures are shifting causing cracks to appear and walls to buckle. CHANCE Helical Piles are renowned the world over for their ability to permanently fix subsidence issues on residential and commercial buildings and also to increase load capacities of existing structures.
CHANCE Underpinning & Helical pull-down micropile systems are used to transfer the building weight to bearing plates installed deep below ground in stable soil. For exterior remediation, underpinning brackets fixed to the foundation support the load of the structure and transfer that to the helical screw pile. When interior remediation is required, CHANCE interior slab bracket is the preferred solution. This patented system brings an economical solution to underpinning systems. Fast, predictable, and measurable are just some of the advantages of this Uk building control evaluated and pre-approved system (LABC).
Engineered for dependability and long-term stability, CHANCE® Helical Underpinning systems provide high-capacity piles to permanently stop settling and cracking of residential, commercial and industrial structures.
In a Chance underpinning foundation, piles are installed independent of the structure to depths beyond problematic soils. The required load capacity is achieved through the measurement of the installation torque applied to the drive motor. The piles are attached to the existing foundation with an appropriately sized pre-engineered bracket.
Advantages to repairing foundations with CHANCE® Helical Underpinning systems above alternative methods:
- Fast affordable installation
- No vibrations or noise
- No vibration during Helical Pile installation
- No excavation spoils to remove
- Low mobilisation costs due to Installation with handheld equipment or standard onsite mini digger
- Ability to be installed in close proximity to underground services
- Built-in quality control – The capacity of each helical pile is accurately measured each and every revolution by recording the installation torque resulting in a tested pile
- Pile can be loaded immediately after installation or, in the case of a Helical Pulldown Micropile, when the grout has set
- End-bearing pile or in the case of the helical pulldown micropiles an end bearing and friction composite pile
- Transfers load through weak soils to the high capacity end bearing helical plates
- 100mm to 255mm diameter grout columns
- 38mm solid steel square shaft to ensure penetration in ground conditions up to N value of 40
How It Works
Our Chance certified and trained installers offer this technically superior and cost-effective Chance underpinning system throughout the UK as an alternative to more disruptive, expensive and time-consuming methods of stabilisation that require extensive excavations. The Chance installers use an engineered design backed by PI insurance which is tailored to the exact repair requirements and ground conditions onsite.
The Chance underpinning method takes a matter of days as opposed to weeks with historic methods. Once the design is produced by a chartered structural engineer, minimal excavations down to the foundation is carried out, a notch is cut to support the pile bracket which will connect the helical pile to the foundation. The unique helical pile is then ‘screwed’ into the ground by a 2 person team either with handheld equipment or on a small mini digger.
The helical pile is installed until the torque measurements confirm that the helical plates have reached competent load-bearing stratum. Adjustable ‘L’ shaped brackets are fitted to the installed helical pile fitting under and bolting onto the side of the foundation. the bracket is then jacked up to achieve the correct loading and or to revelvel the foudation preventing further settlement and transferring the weight of the building to the piles.
Underpinning Bracket Performance
|Bracket Catalog No||C150-0121||C150-0298||C150-0299|
|Anchor Shaft Size||38mm Square Shaft||38mm Square Shaft||46mm Square Shaft|
|SS Anchor Series||Tensile Strength SS5||High tensile Strength SS150||Tensile Strength SS175|
|Minimum Bracket Ultimate Strength||178 kN||178 kN||356 kN|
|With 2.0 Safety Factor||89 kN||89 kN||178 kN|
|Typical Achievable Installed Capacity*||89 kN||111 kN||133 kN|
*The exact capacity of CHANCE Helical Pile Foundations is a function of many individual elements, including the capacity of the foundation, bracket, anchor shaft, helix plate and bearing ground conditions, as well as the strength of the foundation-to-bracket connection and the quality of anchor installation. The last row of the table shows typical capacities of the CHANCE Helical Pier Foundation Systems that are achievable under normal conditions. Achievable capacities could be higher or lower depending on the above factors.