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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 5

Sampling probes

Wastap water and gas sampler

General principle
The Wastap sampling system (Figure 45) is used for obtaining samples of both water and gas at certain depths, without the problems of crosscontamination.
The Wastap is pushed to the desired test level using standard 36 mm diameter CPT rods or 55 mm diameter casing rods. At the test level the Wastap is pulled back enabling the filter to be opened. Then sampling can commence.
Groundwater sampling
The Wastap system provides two methods for
water sampling. One where the sample is pumped up to the surface; the other where the sample is collected in a container within the sampler. 
  • In the first method an electrical or hand-operated vacuum pump is used to pump the water up to the surface from the test depth through a silicone hose. The maximum test depth is restricted to about 8 m below groundwater level
  • In the second method a 0.5 litre container is used. At the desired test depth the container is lowered into the Wastap and locked into position. Then the filter is opened and sampling can commence. There is no restriction for the test depth.

Gas sampling
In unsaturated soils, gas can be sampled, either by pumping it up the same way as water, or by letting it escape under natural pressure. The samples are recovered in membrane-sealed containers for subsequent laboratory testing.

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