Soil Investigation Services

Frequently Asked Questions

What are the Ground Investigation Techniques?

Every soil investigation begins with desk study where any prior maps and data gathered on-site or from previous site investigations is analysed. This research helps our geologists, engineers and environmental scientists to build a basic understanding of the geotechnical aspects of the site, before conducting their own geotechnical investigation.

Once our specialists have assessed the data from previous tests and site investigations, our team will conduct their own site visit. This is known as a walk-over survey and helps our geotechnical engineers to understand the ground conditions in the context of the landscape and terrain.

Once these steps are complete, the intrusive ground investigation techniques will be carried out to gather environmental data. Boreholes and trial pits are dug around the site to gather two different soil samples; disturbed and undisturbed samples.

Disturbed samples are taken with less care to simply determine the types of soils, while undisturbed samples are carefully extracted to keep its structure and water content intact. Sampling undisturbed soil during a soil investigation helps to accurately assess the properties of the soil, including soil density, permeability and strength. These will be kept aside to process in laboratory tests later.

The next series of tests are known as in-situ testing. This is where various tests are carried out in areas of the site intended for construction to understand the engineering properties off the ground. Site investigations of this kind are used to acquire factual data to inform foundation construction and planning any remediation works to prepare the site.

The first of these soil investigation techniques is a standard penetration test, which uses a uniform sampler driven into the soil by a hammer. This measures the soil’s resistance to penetration, which is useful to plan the future foundations of the property. Cone penetration testing is used to assess the resistance of the soil to continuous penetration, providing data on a range of surface layers. Finally, if the soils are clay soils, vane shear in-situ testing is employed to test the clay soil’s shear strength.

Once all the ground investigations are complete, the samples can be taken back to our lab for laboratory testing. We will carry out a series of tests on the soils to understand their physical properties; these include grain size analysis, compaction, permeability and Atterberg limits tests. These tests will provide valuable data on the geotechnical aspects of the soil, which we will include in our soil investigation report.

The results of the soil investigation report from our team will indicate key soil properties from our geotechnical investigations, such as: load bearing capacity, soil strength, density and permeability. This information helps to inform your risk assessments, development of foundations and remediation works to prepare the site for your project.

What Other Site Investigation Services Are There?

At Site Testing Services, we offer a range of ground investigation services to assist construction companies and civil engineering projects. These include CBR (California Bearing Ratio) Testing, Plate Load Bearing capacity tests, and our chemical analysis and testing service.

Whatever you may need to carry out thorough geotechnical investigations of your proposed development site, our specialist team has the equipment, facilities and expertise to deliver the full range of site investigation and testing services.

What Happens After the Ground Investigation?

After sampling the soils on the proposed development site and collecting data through in-situ testing, it’s time for the soils to be returned to the laboratory for further testing. We test the soil using a number of methods, including grain size analysis, Atterberg limits testing, compaction testing and a permeability test.

As implied, grain size analysis is an investigation into the size of the soil grains, which has an effect on its load bearing capacity. The Atterberg limits test is more complex, and involves monitoring at what level of water content the soil changes state from solid to semi-solid, to plastic then liquid. This investigation also helps understand the characteristics of the sub-surface soil.

A compaction test helps to identify the maximum strength of the ground under surface weight, which is vitally important in a geotechnical soil investigation report. Before a property development can go ahead, planners need to be certain that the soil conditions are suitable to hold the weight of the project. The final step in the ground investigation laboratory testing; permeability testing. This is carried out to measure the drainage properties of the ground soil and aids in designing methods of drainage and retaining walls.