The Cone Penetration Test (CPT) is undertaken by pushing an instrumented cone into the ground at a continuous rate. A cable from the cone that runs through the push rods sends information to a computer at the surface giving near-continuous data on the strength of the ground as it is pushed in. The cone records cone resistance, qc, sleeve friction, fs and pore water pressure, u2 at 10 mm depth intervals.
Ground Investigation operates a large range of CPT cones from different manufacturers and of different sizes and sensitivities to ensure that the right cone is used for the particular ground conditions at any site. They range from sensitive cones (20 MPa) for soft clay applications to 100 MPa cones for dense sands and gravels. We have both compression and subtraction cones. All of our cones are electronic piezocones that measure pwp at the u2 position. We have over 30 cones, including:
- Geomil: both 10 cm2 and 15 cm2, 20 MPa, 50 MPa and 100 MPa
- Pagani: 10 cm2, 50 MPa
- A.P. van den Berg: 10 cm2 and 15 cm2: 75 MPa and 100 MPa
- Gouda: 15 cm2, 100 MPa
- Geopoint: 15 cm2, 100 MPa
Our heavy ballasted rigs (Truck-mounted and Morooka rigs) have large push capacities that allow us to undertake CPT testing through dense sands, gravels and weak rock.
At Ground Investigation we undertake our CPT testing in general accordance with internationally recognised procedures as outlined in ASTM D5778-12 and ISO 22476-1.
Our cones are regularly calibrated in-house in our own calibration laboratory.