Guide to Everything About Ground Investigations

Written by Admin | October 27, 2023

There are so many benefits to procuring a ground investigation of your site. Our team of experts can discuss your project to ensure we understand the purpose and the specific details which are important to report on.

If you need a quotation, pricing, or full geotechnical survey, visit our Geotechnical and Ground Investigations Services page to get started.

In this guide, we provide all the information you need to know about the processes of ground investigations, and answer some of the frequently asked questions we receive from our clients regarding ground investigation works.

Why Ground Investigations Now Matter More Than Ever

Ground investigations are no longer just a planning formality. With tighter regulatory scrutiny, increasing foundation failures linked to historic land use, and greater emphasis on sustainability and risk allocation, site investigation now sits at the centre of project viability. Misinterpreting soil conditions, groundwater regimes, or contamination risk can result in any of the following:

Foundation redesign
Unexpected remediation costs
Insurance disputes
Project delays
Planning refusal

A properly scoped ground investigation does not just gather data, it defines commercial risk boundaries before construction begins

Ground Investigation Explained

A ground investigation is used to assess the ground conditions and sub surface structure of a site. Ideally, this should be deployed before the construction on the site starts. They are a vitally important aspect of any development project, as having a detailed understanding of what you are building on is vital to the success of the construction process.

It is imperative to gain an accurate understanding of ground conditions when undertaking a development project. This will determine whether a proposed building design is feasible and safe from a geotechnical perspective.

When is a Ground Investigation Survey Needed?

A ground investigation is essential for gathering factual data for the underlying geology and groundwater levels, that can be interpreted for geotechnical and geo-environmental purposes across a wide range of projects, including residential and commercial developments, as well as infrastructure like highways and bridges.

Ground Investigation is required by but not limited to:

Architects and Engineers.
Construction Contractors.
Environmental Consultants.
Geotechnical and Civil Engineers.
Property Developers.

The Steps Involved in Ground Investigations

To ensure that the outcome of a ground investigation fulfils the objectives of your project, we will follow the steps below and keep you informed throughout the project:

Evaluate the Project specification
Produce Phase 1 Desk Study which includes historical maps, published geology and environmental data
Identify the methodology that fits to purpose and produce a scope of work
Produce Method Statements and Risk Assessments
Undertake Site Works
Undertake Laboratory Testing
Ground Investigation Report

From Desk Study to Intrusive Investigation: The Full Workflow

Most ground investigations begin with a Phase 1 Desk Study, followed by a Phase 2 Intrusive Site Investigation (SI). Understanding the distinction is critical for cost control, planning compliance and risk mitigation.

Phase 1 – Desk Study & Preliminary Risk Assessment

This includes:

Historical mapping review
Published geological mapping
Environmental database checks
Mining and landfill records
Preliminary conceptual site model
UXO Preliminary Risk Assessment

This stage identifies any potential contamination, instability, groundwater risk, or made ground before intrusive works are commissioned.

Phase 2 – Intrusive Investigation

If risks are identified, intrusive works follow, and this can include:

Boreholes
Trial pits
Window sampling
In-situ testing
Ground gas and groundwater monitoring

Laboratory testing is then undertaken to determine engineering parameters or contamination levels. This staggered approach ensures that intrusive works are proportionate, risk-led, and commercially justified.

Find out more about our Phase 1 Desk Study services and reports solutions.

What is the Difference Between a Geotechnical and a Geoenvironmental Survey?

Both surveys use similar site techniques, but the data obtained and how we manage the data make the difference. The difference comes in the type of samples obtained, the scheduled laboratory tests and data interpretation.

More specifically:

Geotechnical surveys typically focus on the engineering properties of the soil and rock, and the main objective is to assess the soil and rock conditions to determine their suitability for construction projects, including foundations, retaining walls, and other structures. Geotechnical surveys as a result provide information about factors such as soil composition, bearing capacity, compaction, and shear strength.
Geoenvironmental surveys, however, are conducted to assess the environmental quality of a site. These surveys aim to identify potential environmental hazards, contamination, and risks associated with soil and groundwater. The focus is on investigating the presence of contaminants, such as hazardous chemicals, heavy metals, and pollutants, as well as their potential impact on the environment and human health.

How Do We Manage and Report the Risks of a Site?

Depending on the site, a range of risks can be recognised, including the potential for unsuitable ground conditions for the intended use of land. Our goal at Technics is to determine the most appropriate ground investigation techniques that align with the site’s characteristics and its current or future land use, and deliver results that fit the purpose of the project.

All results from the report is then provided to our clients as a Factual or Interpretative Report according to the project requirements.

Here are a few examples.

In some instances, the ground conditions may not be suitable for the intended development. A Ground Investigation Report plays a crucial role by providing the civil engineer design values and soil-bearing capacities. This information assists our engineers in then making necessary modifications to ensure the project’s structural integrity.
During a ground investigation, it is possible to come across unforeseen contamination resulting from historical land use, which will need remediation to ensure the safety of the area for future users. This remediation process may involve implementing capping layers for soft landscapes or installing gas membranes and suitable ventilation systems in buildings to cut the pathway of contamination.
Intrusive site investigation methods, like coring, can be effective in uncovering any potential weaknesses in structures, and this technique can be applied across a diverse range of projects, including buildings, retaining walls, bridges, and highways.

Does a Ground Investigation Mitigate these Risks Though?

Ground investigation doesn’t directly mitigate risks, but it does aims to identify the underlying hazards responsible for those risks. This investigation process helps identify these potential hazards, allowing for the further solutions or actions needed to reduce these hazards occurring. These hazards can be either poor ground conditions for future site development or ground and groundwater contamination.

Are There Any Limiting Factors With Ground Investigation Works?

Like any survey, ground investigation has its limitations. When we investigate the ground we can never achieve complete certainty about the challenges we may encounter on a site, even in simple projects, and that’s why we need to treat each project uniquely.

Limiting factors can be irrelevant to the ground conditions, such as limited access, safety hazards, buried services, overhead cables, working on highways or near rails, or in some cases there is the need for temporary works design to be undertaken to enable ground investigation works such as the building of a platform to allow access to the drilling locations.

Our work is to identify these limiting factors, evaluate them, and devise a detailed plan to overcome them.

What Methods and Techniques Will Be Used On-site for the Survey?

Depending on site requirements we can use a variety of ground investigation techniques, which are explained below.

Rotary Drilling

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This method involves the use of a rotating drilling which is capable of core through and sampling various types of rock and soil and giving us Class A samples. We can get disturbed, bulk, SPT’s samples and core samples.

Percussion Drilling

This is a dynamic sampling technique where a drill bit is repeatedly lifted and dropped to sample any type of soil. This technique is relatively cheap and gives us samples to great depths. We can get disturbed, bulk, SPT’s and undisturbed samples.