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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 3

Piezocone

Saturation of the cone penetrometer

   
SATURATION OF THE CONE PENETROMETER   3.2
   
The pore pressure meter is normally a pressure transducer of the
membrane type. The sensor shows insignificant deformation during
loading. It communicates with a porous filter on the surface of the cone
penetrometer via a liquid chamber. The filter element and other parts of
the pore pressure system are saturated with a liquid before field use.
This saturation should be maintained until the cone penetrometer
reaches the groundwater surface or saturated soil.
 
De-aired, distilled water can be used in saturated soils. When
performing dissipation tests in unsaturated soils, dry crust and dilative
soils (eg dense sands), the filter should be saturated with de-aired
glycerine, silicone oil or similar which makes it easier to maintain
saturation throughout the test. It is good practice to cover the filter
element with a rubber membrane, which will burst when the
penetrometer comes into contact with the soil.
 
Porous filters should have a pore size between 2 and 20 μm
corresponding to permeability between 10–4 and 10–5 m/sec. The
following types of material have been used with good performance in
soft, normally consolidated clay, sintered stainless steel or bronze,
carborundum, ceramics, porous PVC and HDPE.
 
The cone penetrometer is designed in such a way that it is easy to
replace the filter and that the liquid chamber is easy to saturate. 
 
In general, filter elements are saturated in the laboratory and kept
saturated in airtight containers until assembly in the field. One
commonly used procedure to assemble and saturate the piezocone in
the field, when using glycerine or silicone oil, is to use a plastic funnel
(Figure 13).
   
 The cone penetrometer is turned upside down and the
cone removed. The funnel is mounted and slowly filled with glycerine or silicone oil. Using a plastic syringe and hypodermic needle, the cavities in the penetrometer are saturated. The filter is carefully transferred from its container to the funnel and all parts are assembled while submerged in the liquid.		 
 
 
   
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