Cone penetration test

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The result of a Cone Penetration Test

The (Dutch) Cone Penetration Test (CPT) is a test to measure the strength or bearing capacity of soils and soft rocks. It was initially developed in the 1950s at the Dutch Laboratory for Soil Mechanics in Delft to investigate soft soils. Today it is the most used method for soil investigation worldwide.

The early applications of CPT mainly determined the soil geotechnical property of bearing capacity. The original cone penetrometers involved simple mechanical measurements of the penetration resistance to pushing a tool with a conical tip into the soil. Electronic measurements began in 1948 and improved further in the early 1970s (de Reister, 1971). A friction sleeve was added in the 1960s (Begemann, 1965) to measure soil cohesive strength. Modern CPT testing apparatus generally utilize a heavy vehicle and hydraulic rams to advance electronic cones into the earth.

The CPT is widely accepted for determining engineering geotechnical properties of soil and delineating soil stratigraphy. CPT can typically resolve stratigraphic layering in unconsolidated soils to a spatial fidelity on the order of 10 cm.

CPT for geotechnical applications was standardized in 1986 by ASTM Standard D 3441 (ASTM, 2004). Later ASTM Standards have addressed the use of CPT for various environmental site characterization and groundwater monitoring activities. In addition to the mechanical and electronic cones, a variety of other CPT-deployed tools have been developed over the years to provide additional valuable subsurface information, including the capture of video imagery through a sapphire window in the CPT probe.

[edit] References

De Reister, J., 1971, Electric Penetrometer for Site Investigations; Journal of SMFE Division, ASCE, Vol. 97, SM-2, pp. 457-472.
Begemann, H. K. S, 1965, The Friction Jacket Cone as an Aid in Determining the Soil Profile; Proceedings, 6th ICSMFE, Montreal, Quebec, Canada, Vol I, pp.17-20.
ASTM, 2004, Standard Method of Deep Quasi-Static Cone and Friction-Cone Penetration Tests of Soil; ASTM Standard D 3441, ASTM International, West Conshohocken, PA, 7 pp.
Meigh, A.C., 1987 "Cone Penetration Testing - Methods and Interpretation", CIRIA, Butterworths.
Cone Penetration Testing in Geotechnical Practice. T. Lunne, P.K. Robertson and J.J.M. Powell. Blackie Academic & Professional. London.