With residential remedial foundation repair becoming a more significant concern in the global subsidence market, the CHANCE® helical screw pile was developed in the mid-1980s and obtained a helical screw underpinning methods patent in 1992. Sounds good? But the question remains: Why are helical screw piles so useful for remedial foundation repair and foundation underpinning in the UK?
What is a helical screw pile?
It is a modular foundation system with helical bearing plates (known as screw helices) attached to a central shaft. The load of the building s primarily transferred through the pile to the ground and onto these helices.
The plates don’t auger the soil but rather screw into it with minimal disruption. The helical plates are located on the piles’ first section, referred to as the “lead” or “starter” section. The lead can consist of one to four helices, but additional helices can be added with helical extensions. Modular extensions allow the lead section to penetrate the soil bearing strata and until the required torque is met.
So that’s the “what,” now what’s the “why.” When studying the foundation repair options on the market.
Why should engineers and contractors choose helical screw piles?
The foundation repair market has many options; drilled shafts, grouted tendons, auger-cast piles, driven piles and others. However, screw piles offer several key advantages over those choices:
- Convenience – they are installed with standard construction equipment, manly with hand-held equipment around domestic houses or with standard 1,3 & 5ton excavators
- Immediate loading – no waiting for concrete to cure
- Ease of use – install in limited access sites 2m headroom, high water tables, and weak surface soils, root protected area and TPO tree preservation orders which means screw piles are a tree-friendly piling solution
- No excavation or spoil removal, nothing comes out of the ground which also gives significant savings when piling in contaminated ground
- Year-round installation – even in rain and mucky wet soils
- No vibration – won’t disturb neighbouring structures, underground sewers, services or electrical cables the piles can be installed within 150mm to these services
- Smaller installation teams are needed – reduced labour costs
- Removable and reusable, and 100% recycled material is used to manufacture the screw piles, which makes them a sustainable method of piling
- Pre-engineered – consistent and predictable results, no matter what the soil reports and ground conditions are
CHANCE developed its first helical screw anchors more than a century ago and have since consistently dedicated resources to research and improvement. Soil and pile studies have resulted in the compilation and documentation of a wealth of knowledge that enables us to predict helical screw pile performance in most soils accurately. All of this knowledge and engineering support are available for each underpinning and piling foundation project.
Supported and sold by an expert distribution team across Northern Europe and the UK, CHANCE helical screw piles are the clear choice for effective foundation repair and underpinning.