What Is The Purpose Of A Trial Pit?

by | Jun 5, 2020

Before any construction project takes place, the ground conditions and soil composition must be worked out to determine whether the proposed construction is feasible or not. This is often done by excavating a trial pit. It’s a simple and cost-effective means of geotechnical site investigation that drilling companies offer.

The team here at Borehole Solutions have dug out countless trial pits between them over the years. We wanted to take a look at why they’ve been so commonplace for so long, and continue to be now.

Trial pits are amongst the most cost-effective site investigation methods available to drilling companies.

What Is A Trial Pit?

Simply put, they’re pits of between 1 and 4 metres depth, and are most usually dug by hand. Sometimes, for larger pits a small digger may be used. For pits deeper than 1.2 metres, structural measures must be put in place. This helps to shore up the pit if someone is to enter it. If there’s known to be any underground features (gas pipelines, electricity cabling etc.) then the means of excavation must be by hand and not by machine.


What Are The Benefits Of Trial Pits?

The following are all benefits of this site investigation methodology:



Trial pits are amongst the simplest and most practical site investigation methods available to a geotechnical drilling company. In terms of the equipment used, the lack of machinery needed (in most cases) saves on fuel and transport costs. Moreover, because the pit is so simple to dig, the work can easily be carried out in one working day, again saving on potential transport costs. It’s certainly a much quicker method when compared with cable percussive drilling, sonic drilling and window sampling.


Solid Results And Flexibility

Trial pitting enables many different samples (both disturbed and undisturbed) to be taken, and various different sampling methods to be facilitated (including Vane Shear tests, Infiltration tests and Contamination tests). The pits allow an initial (yet still fairly comprehensive) soil strata profiling which is crucial for potential contractors. Another benefit is that the subsurface samples taken can be both vertical and lateral, again showcasing the versatility of what at first seems simply like a hole in the ground. Real-time changes to sampling strategy can be conducted with a trial pit without too much effort and without the need for a drastic overhaul of the overall site plan. Hand-dug pits are usually reinstated (if requested) after the sampling has been carried out.

Carrying out site investigation services like trial pitting should be the bread and butter of any geotechnical company. It’s the basis on which further, more complex drilling methods may be carried out, if necessary, and helps provide clients with the information they’re looking for in a quick and efficient manner.


Contact Borehole Solutions Ltd

So, if you’d like to find out more about our trial pit services, then get in touch! Contact Borehole Solutions today on 01733 200 501. We’ve become recognised as one of the UK’s leading geotechnical drilling companies over the past few years. We’re trusted for our work on both small and huge projects alike. So whatever you need doing, you can give us a call.