Understanding Soil Investigation (SI) and Pile Testing

When planning a project that involves screw piles, having the right ground information is key to success. Here’s a quick guide to the essentials of Soil Investigation (SI), and how you can test our screw piles on your site using our hire kit.

Standard Penetration Test (SPT) – What It Means for Your Project

The Standard Penetration Test (SPT) is a common method used in ground investigations to measure the strength of the soil. A mini drop-weight hammer rig is used to drive rods into the ground, and the number of blows required to reach certain depths is recorded. This tells us how dense or strong the soil is at different levels.

For our screwpiles, the ideal SPT value is between 17 and 38 N – with the higher end being most favourable. If the SPT value is lower than this, it may mean using larger pile diameters or bigger flights to ensure enough surface area contact. This helps to achieve the required torque and load capacity.

Soil Reports – What to Expect

Soil reports are usually provided by the project manager or the end customer, and are created by independent site investigation companies. These reports pull together data from tests like the SPT and compile it into a clear summary – often in the form of a Soil Investigation Table or Geotechnical Survey.

These reports typically include:

SPT values (soil strength)
Soil types and layers (e.g. chalk, clay, peat)
Testing depths and results
Images and diagrams of the site and test locations

Independent firms like Socotec and various drilling companies offer these services, and they can also carry out pile load testing if needed.

Hire Our Pile Test Kit

Want to test our screw piles on your site before committing?

No problem – our Pile Test Kit Hire service is designed just for that.

We’ll work with you to understand your project requirements and send the appropriate machinery and screw pile size to provide a like-for-like test on-site.

This setup allows you to trial installation in real ground conditions and assess the achievable torque and depth before a full install.

A few tips when testing:

Know your required torque and estimated pile depth.
Test close to (but not directly on) the planned pile locations—1.5m to 2m away is ideal.

If it turns out that a larger pile is needed, we can supply alternative equipment and piles to suit.

Our team is here to support you in finding the right solution for your ground conditions and project needs.

Please contact us if you have any questions or would like further information on hiring our Test Pile Kit.