Cone Penetration Testing (CPT) is an efficient way to collect geotechnical data with a single test. It is a good alternative to SPT testing and it reduces study duration and cost.
CPT measures point bearing resistance (qc), sleeve friction and penetration pore pressure. These measurements can be correlated to provide information about engineering properties with depth.
CPT offers a more cost-effective alternative to conventional drilling and interval sampling. It also produces more detailed data in a shorter time frame. The results can be analyzed on-site, saving significant engineering design time. The results can be interpreted in a standard computer format, which reduces QA/QC and reporting costs.
The typical electrically-powered CPT probe measures cone penetration resistance (CPR), sleeve friction, and pore pressure (CPTU). Some equiped CPT probes can also measure medium density, shear wave velocity, and temperature. The data can be used for strength profiling, material creep parameters, and pile design loads.
In addition, CPT can be conducted in environmentally contaminated soils. This is because it does not produce cuttings, which makes decontamination much easier. Moreover, it is an effective technique for permafrost investigations. Reference LadanyiLadanyi studied the performance of CPT in frozen geomaterials and concluded that the test is an efficient tool for stratigraphic profiling and creep/strength parameter determination. It can also be useful in determining the degree of ice bonding and identifying shear strengths within a given layer.
The AMA’s CPT Editorial Panel will manage the expedited process of a new code to meet the emergent demand for accurate reporting of novel coronavirus testing offered by hospitals, health systems and laboratories. The panel will review the proposed test description and the corresponding CPT code for approval this week.
While there is extensive literature on the physical properties of frozen geomaterials, CPT remains the only penetrative technique that has been demonstrated to penetrate in alpine snow. The results indicate that mean snow strength derived from CPT tip resistance and local sleeve friction is not significantly different from strength derived from unconfined uniaxial compression testing.
Moreover, CPT allows for high-resolution in situ digital data. This allows engineers to make geotechnical site characterization decisions immediately – saving project cost. Similarly, CPT provides instantaneous shear wave velocity and sediment pore pressure dissipation. This information is used to better estimate design parameters in the field, thus reducing the need for laboratory testing and improving the reliability of projects.
CPT can be conducted in frozen geomaterials, although few studies have been published. However, a few studies have demonstrated that CPT can be used for deriving material creep parameters and stratigraphy in permafrost soil conditions (Reference Buteau, Fortier, and Allard). These findings suggest that the use of rate-controlled CPT can provide important geotechnical information in this difficult and challenging environment.
In addition to measuring tip resistance, sleeve friction and pore pressures, some equipped CPT probes are also capable of capturing shear wave velocity and temperature. These data are useful for interpreting and correlating CPT results to shear strength parameters, and can be used in multiple modelling tools.
WSP provides CPT rigs that can be quickly and easily deployed to supply high quality information vital to making cost effective foundation and environmental decisions. Our rigs utilize truck mounted tanks that are lighter than traditional stationary rigs, resulting in less surface damage and quicker test completion. The truck mounted tanks also allow for the insertion of torsional anchors, which can be utilized in cases of limited penetration capacity due to obstructions such as cobble or boulders.
The CPT method of soil exploration is incredibly versatile. It can provide a wide range of data, including the shear wave velocity and pore water pressure. It also can help determine the shear strength of your soil. It is also fast, allowing you to get more results in less time. This can save you money and reduce the amount of underived waste generated from drilling and sampling.
In addition to cone resistance, sleeve friction, and pore pressure, the typical CPT probe measures shear wave velocity at regular depth intervals. This data can be used to correlate the tip and sleeve resistance to shear strength parameters using proposed empirical curves. The friction ratio (R f = q c/f s) is also recorded by most CPT instruments.
The ability to log the CPT testing sequence on-site is a significant advantage of the system. It allows the user to interpret the test results in real time and make on-site geotechnical design decisions.