Cone Penetration Test (CPT)
Definition
A continuous in-situ test pushing an instrumented cone through the soil and measuring tip resistance and sleeve friction. Provides a nearly continuous soil profile and is more reproducible than SPT.
- Method
- Instrumented cone pushed continuously through soil
- Measures
- Tip resistance and sleeve friction
- Output
- Nearly continuous soil profile
- Comparison
- More reproducible than SPT
Common questions
Why is CPT considered more reproducible than the Standard Penetration Test (SPT) in a geotechnical failure investigation?+
CPT pushes a standardised instrumented cone at a controlled rate and records resistance continuously and electronically, removing the operator-dependent variability of the SPT's hammer-drop blow-count method, which is affected by hammer energy delivery, rod friction and operator technique.
What is the main limitation of CPT that would lead an investigator to still use SPT or borehole sampling instead?+
CPT does not recover a physical soil sample, so it cannot directly support laboratory index or strength testing, and it can be difficult or impossible to advance through dense gravel, cobbles, or very stiff cemented layers where a bored sample with SPT blow counts remains necessary.
Related terms
- Bearing Capacity
- The maximum stress a soil or rock can sustain beneath a foundation without shear failure. Expressed as ultimate bearing capacity (at failure)...
- Differential Settlement
- Non-uniform vertical movement of different parts of a foundation, distorting the structure it supports. More damaging than uniform settlement because it induces...
- Liquefaction
- Loss of shear strength in saturated granular soil when earthquake-induced cyclic loading causes pore water pressure to equal the total stress, reducing...
- Piping
- Internal erosion in an embankment or foundation in which seepage flow progressively removes fine particles along a concentrated flow path until a...
- Standard Penetration Test (SPT)
- An in-situ test measuring the number of blows to drive a split-spoon sampler 300 mm into the soil at a given depth....