American Engineering Testing has enhanced its ability to test and characterize the subsurface by adding a piezocone penetration rig to our array of in-situ testing capabilities. The full complement of in-situ test devices also includes the standard penetration test, pressuremeter, vane shear, and Iowa Borehole Shear.
Piezocone penetration testing (PCPT) is an in-situ test that involves pushing an instrumented cylindrical cone into the ground with a static pressure. During penetration, continuous measurements of tip resistance, sleeve friction, and porewater pressure are made. The equipment is electronic and measurements are automatically collected on a field computer.
The primary purpose of the test is to get detailed information on the stratigraphy of the soil layers and variations in soil properties with depth. An output plot is pictured (lower right). The plot shows tip resistance, sleeve friction, pore pressure, and friction ratio variations with depth. Soil classification is interpreted from the tip resistance and friction ratio values.
In fine-grained soils, the probe penetration can be stopped and the pore pressure dissipation rate measured (to determine drainage properties of the soils). In free-draining soils, the in-situ pore pressures can be measured. The test is much faster than traditional standard penetration testing (SPT) and sampling. Daily drilling footage increases of five times over conventional SPT borings are common.
Our equipment consists of a ten ton electronic subtraction cone manufactured by Vertek. The equipment also has seismic capabilities, where p-wave and s-wave velocities can be measured throughout the soil profile. These values can be used to evaluate deformation moduli of the various soil deposits.
The new device has been used on many sites so far. On each site, we have correlated PCPT data with conventional soil boring data and found the interpreted soil classifications from the PCPT data is consistent with actual soil sampling classifications. |
