Geotechnology’s Cone Penetrometer Testing (CPT) provides a detailed, in-situ testing method used to map soil stratigraphy and estimate many fundamental geotechnical engineering properties of softer, sensitive soils. Three major advantages of using CPT that add value on your project are:
CPT provides a continuous record of soil stratigraphy, revealing thin layers of dissimilar materials; for example, a half-inch thick sand seam within a thick clay stratum. Such thin layers of material with dissimilar properties, which may be missed when using conventional drilling and interval sampling, can have a significant impact on geotechnical engineering aspects of a project.
The daily production rate for CPT is often 1.5 to 3 times faster than conventional drilling and sampling. The CPT process does not produce cuttings and eliminates cutting disposal as a drilling task.
Compared to standard penetration testing, CPT offers increased accuracy, speed of deployment and advanced in-situ testing that results in a more continuous profile and reduced cost.
The CPT equipment includes an instrumented cone tip that measures resistance to penetration on the tip and sides of the cone as the cone is pushed into the ground at a controlled rate. The resistance force values are transmitted sonically from the cone to the top of the CPT push rods. The sonic data is converted through a special microphone into electrical signals and digitally recorded. Soil stratigraphy is interpreted from the signature combinations and patterns of tip and side resistance. CPT for geotechnical applications is described in ASTM Standard D 3441.
Geotechnical Data from CPT
- Standard Penetration Test (SPT) blow count correlation
- Soil types
- Undrained shear strength
- Relative density
- Effective Friction angle
- Coefficient of lateral stress
- Water table elevation