Screw Piles
Screw Pile Capacities and Installation Equipment
Un-factored Load - A Maximum load that the Pile will take before deflection exceeds standard limits.
FOS - Factor of Safety - is the ratio between the un-factored load and the working load
Safe Working Load -The actual load the pile is taking when the building is in place
All machines offer torque read outs, allowing the pile capacity to be calculated instantly.
Screw Pile Specifications
SPECIFICATION | DEFINITION | 60R | 76R | 89R |
---|---|---|---|---|
Shaft Diameter | Diameter of the screw pile shaft excluding helices | 60mm | 76mm | 89mm |
Wall Thickness | Thickness of the screw pile tube wall | 6.35mm | 9.5mm | 9.5mm |
Torque Limit | The ability of the pile to transmit torque is always the limiting factor. This is therefore the ultimate practical pile install torque capacity. | 4kNm | 16kNm | 25kNm |
Ultimate Strength Single Helix | The load which can be supported by a single helix- most piles use multiple helixes, but if a single one has to support more load (although non standard) this can be accommodated. | 90kN | 160kN | 220kN |
Empirical torque factor KtKt m-1 | The “Empirical Torque Factor” expressed in metric units when torque is measured in kNm and force in kN. Its value decreases as pile diameter and helix plate thickness increases. This is due to a combination of skin friction and the energy needed to displace the soil. | 30m-1 | 28m-1 | 25m-1 |
Tube Specification | S355 HFS | DIN1629 ST52 or Equal | S355 HFS | |
Helix Specification | BS4360 43A | BS4360 43A HRMS | BS4360 43A | |
Fasteners Specification | Metric M16 GR8.8 | Metric M20 GR8.8 | Metric M22 GR8.8 |
Pile Life/Corrosion
In most conditions, provided the top 2 metres are galvanised the pile life will be in excess of 100years. Where the soil resistivity is less than 10 Ohm– further steps must be taken. This means salt water, wet peat and where soils are subject to saturation. For more information and literature please contact us.
The estimated life is based on the assumption that a loss of 40% in thickness is acceptable without adverse effect on structural integrity. The atmospheric exposed areas of the piles are coated with high build zinc rich coating system or galvanised. There is a safety factor of x2 included for the anode design to take account of variances in corrosion conditions and ground resistivity.
Ground Resistivity(Ohm-m) | Corrosion rate based on Uhlig data mm/yr | Estimates life with corrosion protection (years) | Corrosion protection methods, required for top 2m section of Pile. (Min 9.35mm wall thickness) | Estimated life with additional corrosion protection* (years) |
---|---|---|---|---|
Less than 5 | 0.1-0.2 | 18-37 | Zinc rich coating 4 x 20kg galvanic zinc bracelet |
100 |
5-10 | 0.033 | 80+ | Zinc rich coating 4 x 20kg galvanic zinc bracelet |
100+ |
10-50 | 0.025 | 100 | Zinc rich coating | 100+ |
50-100 | 0.018 | 100+ | n/a | 100+ |
Greater than 100 | 0.014 | 100+ | n/a | 100+ |