625kN Pile Test – Restricted Access London Site

When configuring suitable screw piles for a project, our Engineers rely heavily on soil properties determined from geotechnical investigation. Often undertaking soil testing using the ABC Anchors soil test probe, or commissioning a full soil investigation (SI) report from a geotechnical engineering firm provides us with sufficient design information. On small projects, use of our soil test probe instead can significantly reduce the cost compared to an SI report and provide similar results for specification purposes.

There are occasions however when pile testing is necessary to confirm our pile specifications.

ABC Anchors was recently contacted by a Client looking to install screw piles for a residential project in close proximity to the Thames in London. From an initial review of the SI it was understood that the site was underlain by a thin layer of dense gravels, however the soil properties below this were not described in the report. Being London based, an area known for weak Clays, and with a site in such close proximity to a river; it was decided that the soil report could not be relied upon alone. As the project required over 50 piles to be installed with design safe working loads of 20 tonnes per pile, it was critical to test the pile under load to confirm that any settlement was within acceptable limits.

ABC Anchors installed an 89R test pile to an installation torque of 25kNm using our Autoguide 2500X torque head mounted on a 3 tonne excavator. Typically excavators between 5-10 tonnes are used to install piles of this size, however as the site access was restricted to a small alleyway only 1.5m wide, a 3 tonne excavator was the only option. It was a testament to our Engineering team’s ingenuity and the skill of our installers that installation torques of this magnitude were achieved using such a low powered machine.

The pile was tested using our recently redesigned ABC Anchors testing equipment and experienced only 2mm of settlement when loaded to the pile’s ultimate load capacity of 62.5 tonnes. The Federation of Piling Specialists suggest that allowable settlement should be no more than 10mm under working loads.

The testing was a complete success and confirmed the suitability of our 89R rock tip pile for the project.

Installation Packages

Package Choices

We can offer several packages for the supply and installation of our screw piles.

We can supply the piles and recommend an installer who will offer a full installation pile log with guarantee of work.

We can supply the piles and hire out the installation equipment for you to install.

Training courses at our premises or onsite (How to correctly use our equipment to install screw piles).

Onsite guidance.


Torque Heads

400H
400H

500X / XG
500X / XG

650H
650H

1600X
1600X

2500X / XG
2500X / XG

All our torque heads are manufactured by our sister company Autoguide Equipment and can be either purchased or hired from us. This can be on a daily or weekly basis.

Downloads

ABC Torque Heads

New Build – 89R Screw Piles Henley on Thames

89R piles were installed for foundations on this site in Henley on Thames. The site was particularly sensitive as it contained roman artefacts which if exposed would have halted the build. The installation of the piles also included a load test on a single pile which is sometimes asked for by the structural engineer to verify installation torque against pile capacity.

Screw Piles

Screw Pile Capacities and Installation Equipment

  60Rrangeb 76RRangeb 89R-39336b
Screw Pile Range 60R 76R 89R
Torque Head Model 400H 500X 650H 1600X 2500X
  400H 500X_XG 650H 1800X 2500XGb
Max Torque 4kNm 5kNm 6.5kNm 16kNm 25kNm
Machine Type Hand-held Excavator Hand-held Excavator Excavator
Ultimate Pile capacity
(un-factored) torque
120kN 150kN 180kN 450kN 625kN
Safe Working Load
(2.5 FOS)
48kN 60kN 73kN 180kN 250kN
Specification Sheet
(PDF)

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+

Equipment Hire

Screw Pile Installation Equipment Hire

ABC Anchors offer a range of Autoguide’s screw pile specific torque heads for hire. All torque heads come equipped with torque gauge for driving screw piles to the required installation torque.

Installers for 60R Piles

400H Hand-held Anchor Drive

Our 400H portable anchor installer is available with or without the hydraulic power pack and is ideal for use in confined spaces or areas of limited access. We hire this machine for installing our 60R screw piles, to accommodate loads up to 48kN.

500X / XG Torque Head

We have a range of mounting brackets to attach the 500X to excavators from 1.5 to 6 tonnes. This allows anchor installation at a wide range of angles. When access is not an issue, installation using the 500X instead of our handheld equipment allows our 60R screw piles to accept loads up to 60kN.

400H
400H

500X / XG
500X / XG

Installers for 76R Piles

650H Hand-held Anchor Drive

The 650H portable anchor installer is available with or without the hydraulic power pack and is ideal for use in areas of limited access much like the 400H. This larger handheld machine can accommodate loads up to 73kN with our 76R screw piles.

1600X

The 1600X is the torque head of choice for installing our 76R screw piles, accepting loads up to 180kN. It can be mounted using a range of brackets to excavators from 4 to 7 tonnes.

650H
650H

1600X
1600X

Installers for 89R Piles

2500X

The 2500X is an excavator mounted torque head for use with 89R screw piles. Our largest pile can accept loads up to 250kN and must be installed using an excavator from 4 to 10 tonnes. The torque head is shown here with the Gimbal bracket, which allows installation when head room or the excavator boom arm length is an issue; mounting on the side of the head rather than the top.

2500X / XG
2500X / XG

Soil Test Probe

The soil test probe is used to determine the soil conditions on site where no soil investigation information is available. Torque readings are recorded at 250mm intervals to provide an indication of the properties of the soil. These readings can be easily correlated against SPT value charts to determine the soil type and it’s suitability for accepting screw piles.

As a general rule, screw piles are not designed to penetrate solid bedrock, nor are they able to penetrate through obstructions such as boulders or buried concrete. However most other soil types are acceptable.

Being hand driven or with a high torque battery drill, the data produced allows the engineer to design the most suitable pile configuration for the calculated loads.

On many small projects use of this equipment can result in overall price reduction (especially compared to a full ground investigation), with a high level of confidence in the finished result.

Soil Test Probe
Soil Test Probe