We use the most reliable, worldwide test, the cone penetration test (CPT). The CPT is an in-situ testing method used to determine the geotechnical engineering properties and delineate the lithology of your soil.
The CPT test method consists of using a hydraulic rig to push an instrumented cone tip into the ground through several rods. It continuously measures the resistance needed to penetrate the soil at a constant rate of two centimeters per second. The total force acting on the cone is called the cone resistance and qualifies the strength of your soil. The force acting on the sounding rods provides the total friction. Measurements with an electric cone, equipped with a friction sleeve, provide the local sleeve friction (CPT-E).
When the exact groundwater level has to be monitored, a piezometer is quickly installed to gather water pressure data. The thrust capacity of the sounding equipment is supplied by the truck’s ballast or by screw anchors to achieve extra reaction.
The information gathered is used to calculate the following geotechnical parameters:
- Effective friction angle
- Coefficient of consolidation
- Bearing capacity
- Settlement behavior of a foundation
This detailed set of calculations allows us to provide a comprehensive report with the right advice to ensure the suitability of your foundation plans.
We use only the very latest CPT techniques, including:
- Mechanical cone penetrometer – provides the calculations for building foundations by measuring the cone resistance at regular 20 centimeter intervals. We use the Dutch cone with a conical mantle and the Begemann cone with local sleeve friction.
- Electric cone penetrometer – gathers more complete information, enabling a better classification of soil layers (for example, detecting a thin peat layer in clay soils). The cone resistance and local friction is measured continuously every two centimeters, allowing the friction ratio to be calculated. A computer registers the measurements which are transmitted through the electric cone to the surface through cables inside the penetrometer rods.
- Piezocone (CPT-U) – gathers additional pore water pressure data.
- SoniCPT – based on the ‘sonic samp drill’, the SoniCPT is a unique system that we developed using vibrations to make soil more fluid. Vibrations are used to make the soil more fluid and reduce friction, allowing the sonic system to pass through hard surface layers or lose sediments. When the CPT is blocked, the sonic can pass through and continue measuring, saving valuable time.
For every investigation we provide a comprehensive report, clearly illustrating the measurements and calculated parameters in tables and graphs. We provide you with a description and interpretation of the test locations, stratigraphy and groundwater findings. You will receive a clear site plan with advice on adapting your foundations where necessary for maximum support strength.