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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

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

Wing cone

  
 WING CONE   4.14		 
   
Lime cement columns
Lime cement columns are being increasingly used in the UK ground improvement industry for stabilising soft soils. The advantages of this method is that it produces no spoil; and installation is relatively quiet and vibration free.
 
Verification
Once the columns have been created there needs to be some kind of verification to prove that the proposed level of ground improvement has been reached. This is done by one of two methods outlined in the Swedish Geotechnical Society report, SGF Report 4:95E[11].
  
   
 
 
  		 
Push-in wing cone
This method uses a wing cone (Figure 35) of varying diameter depending on the diameter of the column. The wing cone is then pushed through the column and the total force required for penetration is measured.
 
Pull-out wing cone
With this method a winged probe is
installed at the base of the column when the column is being constructed. A cable is attached to the probe, which comes up the centre of the column and is attached to the rams of a CPT rig. The force required to pull the winged cone is then recorded.
 
Figure 36 shows the derived shear
strength values, Su, using a wing cone.
The Su values are used to verify that the lime cement column has reached the required design strength. The original output of the test is a total pushing or pulling force (kN) which is then converted into Su values as described in the SGF Report 4:95E. 
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