Earthworks play a crucial role in construction projects, providing the foundation for buildings, highways, and infrastructure. Various tests are conducted during the earthworks phase to ensure the stability and safety of these structures.
In the UK, strict regulations and standards govern earthworks testing to ensure compliance with industry best practices.
This blog will explore some of the common tests associated with earthworks testing in the UK, shedding light on their significance and methodologies.
What Is Earthworks Testing?
Earthworks testing is the analysis of soil to determine its composition, strength, stability, moisture content, and load-bearing capacity. These factors influence everything from foundation design to drainage planning and long-term structural integrity.
Earthworks soil testing is typically conducted during the early stages of a project, before or during excavation, and may continue throughout the earthworks phase to monitor changes as the site evolves.
Earthworks testing generally falls into two categories: on-site testing and laboratory-based testing. Each method plays a unique role in evaluating soil properties and composition, and together, they provide a comprehensive view of ground conditions.
How to Test Soil Composition & & Why It Matters
Earthworks testing is a critical phase in construction projects, ensuring the stability and performance of structures. Tests provide valuable insights into soil behaviour and aid in making informed engineering decisions. By conducting these tests, engineers can mitigate potential risks, optimise design parameters, and ensure the successful completion of earthwork projects across the UK.
Testing soil composition is the first step in classifying soil and understanding how it will behave under load, with water, and over time. Soil composition refers to the mix of mineral particles (sand, silt, clay), organic material, air, and water in the soil. Different combinations can result in vastly different performance – which is why earthworks testing is so important in construction and engineering.
There are two primary ways to test soil composition:
- On-Site Soil Classification: Simple field methods like manual texture tests, visual inspections, and basic in-situ tools (like the dynamic cone penetrometer) can give a quick indication of soil type. For example, sticky, fine-grained soils often indicate a high clay content, while loose gritty soils suggest sand.
- Laboratory Soil Analysis: More detailed classification can be completed in the lab using tests such as particle size distribution, Atterberg limits, and moisture content, giving insights into soil composition and what this means for its performance.
Beyond classification, engineers also test how soil performs under stress, load, and environmental changes. Together, these tests offer a complete view – from what the soil is made of, to how it will behave during and after construction.
Earthworks Testing Solutions: On-Site Methods
On-site (or field) testing involves evaluating soil directly at the construction location. These tests are usually faster and less expensive than lab tests and provide real-time data that informs immediate decisions. They are also essential for real-time compaction control.
Common on-site test methods include:
- Dynamic Cone Penetrometer (DCP) Test: Measures the strength and compaction of soil layers by driving a cone into the ground. It's useful for checking soil consistency and bearing capacity.
- Standard Penetration Test (SPT): Performed inside boreholes, this test gauges soil resistance to penetration under impact, helping determine density and relative strength.
- Plate Load Test: Measures the settlement of soil under a known load to determine bearing capacity for shallow foundations.
- Nuclear Density Test: Evaluates in-situ soil density and moisture content, useful for monitoring compaction during fill placement.
- Visual & Manual Classification: Observations of colour, texture, moisture, and layering to make preliminary assessments of soil types.
Earthworks Testing Solutions: Laboratory Methods
Lab testing offers a higher degree of accuracy and control. Soil samples taken from the site are brought to a lab where environmental conditions are tightly managed to ensure precision. These tests are highly repeatable and are essential for geotechnical engineering calculations and design.
Common laboratory test methods include:
- Particle Size Distribution: Determines soil particle sizes, which is key to understanding permeability and classification.
- Atterberg Limits (Liquid, Plastic, Shrinkage Limits): Defines the behaviour of fine-grained soils under varying moisture contents.
- Proctor Compaction Test: Identifies the optimum moisture content for achieving maximum soil density through compaction.
- California Bearing Ratio (CBR) Test: Assesses the strength of subgrade soil and its ability to support roadways and pavements.
- Triaxial Shear Strength Test: Measures shear strength parameters, critical for slope stability and retaining wall design.
- Permeability Test: Evaluates how quickly water can pass through soil, which is important for drainage and foundation planning.
How to Test Soil Bearing Capacity
One of the most important characteristics of soil is its bearing capacity. There are several on-site and laboratory-based testing methods to assess the bearing capacity of soil, including the Dynamic Cone Penetrometer (DCP) test, the plate load test, and the California Bearing Ratio (CBR) test.
Field Test for Bearing Capacity of Soil
Dynamic Cone Penetrometer (DCP) Test
The DCP test is a well-recognised field method for assessing soil strength and estimating bearing capacity. It involves driving a standardised metal cone into the ground by repeatedly dropping a fixed-weight hammer from a consistent height.
The depth of penetration per blow is measured to evaluate the soil’s resistance. This data enables engineers to estimate bearing capacity and assess variations in soil stiffness with depth. This is particularly useful for granular soils and compacted subgrades.
Plate Load Test
Plate Load Testing is a widely used method to determine the bearing capacity and settlement characteristics of soil. It involves applying a known load onto a steel plate placed on the ground and measuring the corresponding settlement.
This test helps engineers understand how the soil will respond to the loadings expected during construction. The results help determine the appropriate design parameters and identify any potential issues that may arise.
Lab Test for Bearing Capacity of Soil
California Bearing Ratio (CBR) Test
The California Bearing Ratio (CBR) test measures the strength and stiffness of a soil sample. It is commonly used to assess the suitability of subgrade soils for road construction. The test involves applying a load to a soil sample and measuring the penetration resistance.
The ratio of the penetration resistance to that of a standard material provides the CBR value. This value helps engineers evaluate the load-bearing capacity of the soil and determine appropriate pavement thickness and design.
How On-Site & Lab Testing Complement Each Other
On-site and lab testing are not mutually exclusive; they are complementary. On-site testing provides quick feedback and helps guide construction decisions in real time, while lab testing offers detailed insights for engineering design and regulatory compliance.
For example:
- Field compaction results might indicate insufficient density—lab Proctor tests help identify the ideal compaction method.
- On-site penetrometer readings might show variability in soil strength—lab triaxial testing can confirm whether deeper foundations are necessary.
- Visual field classifications are validated by lab-based grain size and Atterberg limit tests.
Together, they provide a robust understanding of the site’s geotechnical profile, ensuring that earthworks are performed efficiently, safely, and to spec.
The Broadest Earthworks Testing Capacity with CTS
Proper earthworks testing is fundamental to the success of any construction project. By combining the speed of on-site testing with the accuracy of laboratory analysis, project teams can make informed decisions, reduce risk, and build with confidence. Whether you’re dealing with sandy soils, clay-rich subgrades, or engineered fill, a thorough testing strategy is the first step toward a stable and long-lasting structure.
At CTS, we pride ourselves on consistently delivering high-quality on-site and laboratory earthworks UKAS accredited testing that enables our clients to meet their compliance obligations and continue with projects safely and without delay.
To find out more about our earthworks testing services, please get in touch with a member of the CTS team today, and we’ll be more than happy to answer any questions you may have regarding our services and how we can help you.