Ground conditions represent the greatest hazard to any construction project. Building and construction case records show that ground conditions are often the cause of large cost and time overruns. However, a ground investigation tailored to the specific needs of the site can reduce these geotechnical risks. A suitable ground investigation can save costs by enabling contractors to foresee an issue before it becomes a costly problem.
Structural Soils is a leading and award-winning ground investigation contractor. For over 50 years, we have provided in-house rigs and resources capable of performing a wide variety of investigative techniques through soft superficial deposits to hard underlying bedrock to suit any size of project. The investigation usually includes both geotechnical and geoenvironmental aspects.
Our multidisciplined teams include engineers, geologists, environmental scientists, drillers and technicians who can undertake all aspects of ground investigation and remediation works. The team, many holding chartered status, can advise on suitable methods for individual projects ranging from small-scale domestic investigations, such as house extensions, to larger major civil engineering works.
Desk study/preliminary risk assessments
The first phase of any ground investigation is a desk study, which enables development of an initial ground model known as a conceptual site model. A desk study considers the risks posed to a development by current or previous potentially contaminative uses and the geotechnical or environmental hazards of the site and its surrounding area. The information sources we typically review during this process are:
- Historic map review
- Previous land use
- Historical archive search
- Geological and hydrological setting
- Mining activity
- Radon category
- Land stability
- Pollution incidents
- Groundwater designations
- Walkover survey
- Unexploded ordnance
- Conceptual site model
- Ground investigation recommendations
Developing a site-specific conceptual site model and outlining the anticipated physical and geoenvironmental setting enables us to specify a precise and targeted ground investigation.
We use the findings of the desk-based studies and the outline development proposals to design an appropriate intrusive ground investigation, employing techniques that will depend upon site-specific circumstances such as the anticipated geology, previous land use, topography and available access. We can design the intrusive investigation to cover geotechnical aspects and design or geoenvironmental assessment, or both.
Fieldwork involves drilling both shallow and deep exploratory holes to establish ground conditions. Structural Soils operates 26 varied boring and drilling rigs with direct access to more than 50 additional drilling rigs through sister companies. In addition, we are able to provide a full ground investigation service to many sectors, such as rail, utilities, power and nuclear, which require dedicated personnel and equipment for these unique working environments.
Our services include:
- Trial pitting and trenching
- Window sampling and dynamic probe testing
- Cable percussive boreholes
- Rotary drilled and cored boreholes
- Dedicated rail sector, including RAIL SI and RAIL SI+PLUS
- Probeholes for legacy coal-mining issues
- In-situ testing
- Geotechnical and geoenvironmental sampling
- Instrumentation and monitoring
Building on more than 25 years’ experience of undertaking ground investigations for the rail industry, Structural Soils has launched two new integrated services for the rail sector: RAIL SI and RAIL SI+PLUS. These combine our comprehensive ground investigation services with support from the wider RSK group, including ecology surveying and clearances, asbestos and geospatial surveying, and many more.
Structural Soils carries out a range of in-situ testing techniques to supplement ground investigation data and substantiate geotechnical laboratory results. In-situ testing can add value, as these methods are usually cheaper and a larger number of tests may be carried out in the same time as an average borehole.
Our services include
- California bearing ratio testing
- Plate load testing
- TRL dynamic cone penetrometer testing
- In-situ density tests
- Sand replacement density testing
- Nuclear density gauge testing
- Light weight deflectometer testing
- Soakaways/infiltration rate
- Variable head permeability testing
For more information, please see in-situ testing.
Instrumentation and monitoring
Where required, our specialist monitoring teams can provide longer-term monitoring using varied instrumentation. This may involve routine monitoring of groundwater or ground gas or using more specialised instruments to measure movements in slopes, settlement or pore-water pressures. We can also sample groundwater or gas during monitoring visits.
- Groundwater and ground gases
- Continuous groundwater level datalogging
- Photo-ionisation detection
- Oil–water interfaces
- Well purging and in-situ water and gas sampling
- In-situ groundwater quality testing
- Standpipes and piezometers
- Pneumatic and vibrating wire piezometers
For more information, please see monitoring.
Laboratory testing (soil, rock and materials testing)
Geotechnical and geoenvironmental testing is usually carried out after a ground investigation, as many of the geotechnical parameters required for design are determined from laboratory testing. We perform geotechnical testing in our in-house UKAS-accredited laboratories; Envirolab, our sister company, undertakes geoenvironmental testing.
For more details, please see soil, rock and materials testing.
Reporting and advice
We can present the ground investigation results as factual data or in reports offering advice. These reports can provide geotechnical and geoenvironmental recommendations. Exploratory hole and other test data are presented in accordance with the latest British Standards and Eurocode 7. We produce high-quality reports, with ground investigation data presented electronically in the latest AGS format for inclusion in BIM.
Coal mining risk assessments
Structural Soils can check the Coal Authority’s database of past and present coal-mining areas to see if your site is classified as a high-risk area. The Coal Authority is a statutory consultee for any planning application, and a coal-mining risk assessment is required for any proposed development within a designated high-risk area.
A coal mining risk assessment report is similar in nature to a desk study, i.e., reviewing all the available data that would identify any risks to potential development. If the report finds potential risks to the development, the team would design a suitable intrusive investigation to mitigate these risks.
Structural Soils is an experienced principal contractor and can assume the relevant duties under the Construction, Design and Management (CDM) Regulations 2015. We have various construction and other industry-related accreditations and provide services to a wide range of clients, including many major companies under framework agreements. Structural Soils is certified to an integrated management system comprising the ISO 9001, ISO 14001 and OHSAS 18001 standards for quality, environmental, and health and safety management.