Editing Cone penetration test (section)

== History and development ==
[[Image:sondeerstaat.jpg|right|thumb|250px|The result of a cone penetration test: resistance and friction on the left, friction ratio (%) on the right.]]
The early applications of CPT mainly determined the logistics of soil geotechnical property of [[bearing capacity]]. The original cone penetrometers involved simple mechanical measurements of the total penetration resistance to pushing a tool with a conical tip into the soil. Different methods were employed to separate the total measured resistance into components generated by the conical tip (the "tip friction") and friction generated by the rod string. A [[friction]] sleeve was added to quantify this component of the friction and aid in determining soil cohesive strength in the 1960s.<ref>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.</ref> Electronic measurements began in 1948 and improved further in the early 1970s.<ref>De Reister, J., 1971, "Electric Penetrometer for Site Investigations"; Journal of SMFE Division, ASCE, Vol. 97, SM-2, pp. 457-472.</ref> Most modern electronic CPT cones now also employ a [[pressure transducer]] with a filter to gather [[pore water pressure]] data. The filter is usually located either on the cone tip (the so-called U1 position), immediately behind the cone tip (the most common U2 position) or behind the friction sleeve (U3 position). Pore water pressure data aids determining stratigraphy and is primarily used to correct tip friction values for those effects. CPT testing which also gathers this [[piezometer]] data is called CPTU testing. CPT and CPTU testing equipment generally advances the cone using hydraulic rams mounted on either a heavily ballasted vehicle or using screwed-in anchors as a counter-force. One advantage of CPT over the [[Standard Penetration Test]] (SPT) is a more continuous profile of soil parameters, with data recorded at intervals typically of 20&nbsp;cm but as small as 1&nbsp;cm.
 
Manufacturers of cone penetrometer probes and data acquisition systems include Hogentogler, which has been acquired by the Vertek Division of [[Applied Research Associates]],<ref>{{cite web |archive-url=https://web.archive.org/web/20160304083334/http://www.hogentogler.com/cpt_equipment.asp |archive-date=March 4, 2016 |url=http://www.hogentogler.com/cpt_equipment.asp |title=CPT Equipment |publisher=Hogentogler & Co., Inc. |url-status=dead}}</ref><ref>
{{cite web |url=http://www.vertekcpt.com/cpt-cones-and-data-acquisition-systems |title=CPT Cones and Data Acquisition Systems - Vertek CPT |publisher=Applied Research Associates, Inc. |year=2016}}</ref> GeoPoint Systems BV<ref>{{cite web |url=http://geopoint.nl/en/ |publisher=Geopoint Systems BV |year=2016 |title=Geopoint.nl}}</ref> and Pagani Geotechnical Equipment.<ref>{{cite web |url=http://www.pagani-geotechnical.com/cpt-systems/ |title=CPT - Cones and Acquisition Systems |publisher=Pagani Geotechnical Equipment |year=2015 |access-date=2017-02-04 |archive-date=2021-06-22 |archive-url=https://web.archive.org/web/20210622194433/https://www.pagani-geotechnical.com/cpt-systems/ |url-status=dead }}</ref>