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Published By Lankelma

Lankelma is the foremost contractor for onshore in-situ soil testing in the UK. An acknowledged specialist in CPT, Lankelma also offers a worldwide consultancy and training service.

A.P. van den Berg develops, designs and manufactures geotechnical and environmental soil investigation equipment for onshore and offshore applications. Specialists in CPT systems and equipment.


Gardline Geosciences offers worldwide marine geotechnics, in-house consutancy and services with marine investigations ranging from nearshore to full ocean depth (down to 3000m).

About the Author

Hans Brouwer studied civil engineering at Delft University in The Netherlands. He has worked as a part-time lecturer at Amsterdam Polytechnic and was senior partner in a structural engineering consultancy. He has written a standard textbook in Dutch about the design of building foundations. He now lives in England where he writes technical textbooks in English, hopefully to reach a bigger readership.

Chapter 4

Part 3: Special cones: other cones

Video Cone

The video cone (Figure 37) – in appearance, identical to the hydrocarbon cone described in Section 4.11 on page 37 – is a new and innovative soil investigation technique to provide images of subsoil. The cone is pushed into the ground with standard cone
penetration equipment. The video cone,
developed by GeoDelft in 1998, consists of a stainless steel cone, measuring 60 mm in diameter and 1 m in length.
The camera window of sapphire glass is located some 30 cm behind the cone tip. The viewing glass is small, measuring 5 x 7 mm. A lamp, mirror and video camera are fitted behind the glass. The camera is connected via an electronic signal cable to a video recorder and monitor in the test truck.
Video recording
The video cone is pushed through the soil, ideally at a speed of
5 mm/sec, using extension tubes with a diameter of 55 mm.
Continuous, and simultaneous video recordings of the subsoil are
made. Online viewing is also possible on a monitor.
A microphone can be connected to the sound channel of the video to
provide a commentary. During soil penetration, a light beam shines
through the viewing glass directly onto the adjacent soil, enabling the
camera to record an image.
The images (exemplified by Figures 38, 39 and 40, on the opposite
page, of clay, sand and chalk) show the soil with a resolution of 752 x
582 pixels. Presentation of the images from the surface of the viewing
glass to the monitor substantially magnifies the soil grains and
particles. Magnification can be up to 100-fold, depending on the type of
This method provides information which is not directly visible to the
naked eye. For example, mineral particles such as shells can be easily
distinguished from other mineral particles. Small voids, gas bubbles
and contaminants are also readily visible. 


If used in combination with other soil penetration techniques, the video
cone has the potential to further optimise the subsoil model. In the case
of soil contamination, material transport models can be established
with greater reliability.
Possible uses for the video cone which are presently envisaged are:

  • detailed description of subsoil (subsoil modelling)
  • mapping of floating layers (eg petrol or diesel oil)
  • mapping of sinking layers (eg creosote oil)
  • mapping of contamination (eg by using PAHs). 
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