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Safely uncovering deep foundations and services with magnetometer cone (2010)

A recurring issue for drillers, building contractors, water board districts, service and energy companies is the lost or lacking knowledge on the dimensions or positions of existing underground structures and obstacles such as unexploded ordnance (UXO).

01 May 2010
S. N. Elgun, C.A.H.M. van Isselt & R. Jansch


There are problems with old barriers and reinforced dams, where the length of old sheet-pile walls are often unknown. To build safely close to a water-retaining structure, the position of ground anchors need to be known to avoid problems during pile driving. When adding more power lines to existing suspension towers, the position and length of the reinforced foundation piles needs to be known.
A CPT penetrometer with built-in tri-axial magnetometer has been developed. With this combi-cone, ferromagnetic materials in the underground can be detected. Together with the earth’s magnetic field strength in 3D, the normal CPT parameters such as point resistance, sleeve friction, slope and pore pressure can be measured.


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