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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 6

Instrumentation

BAT piezometer

 


BAT PIEZOMETER   6.3
 
With the BAT system the water pressure in the soil can be measured accurately and efficiently. With an additional set of attachments the BAT system also offers the possibility of determining the permeability of the soil surrounding the piezometer tip and collecting accurate groundwater samples. Typically the BAT piezometer (Figure 49) consists of a filter tip and a sensor, both installed via a steel gas pipe.
 
The BAT system measures the absolute pressure which guarantees stability, especially during continuous monitoring. The sensor can also be disconnected at any time to check its proper function and to determine the exact depth of the filter tip.
 
Applications
Typical applications for the BAT piezometer are for monitoring:

  • porewater pressures to determine safe rates of fill or excavation
  • porewater pressures to determine slope stability
    the effects of ground improvement systems (eg vertical drains and sand drains)
  • pore pressures to check the performance of earth-fill dams and embankments
  • pore pressures to check containment systems at landfills and tailingsdams
  • contamination 
  
   
  
 
  
Installation
The BAT system consists of a filter tip and a sensor. The filter tip is pushed to the desired depth using a standard gas pipe and a CPT unit. The sensor component then is simply lowered into position through the gas pipe. As soon as the BAT sensor has contacted the filter tip, the pore pressure measurement will start. After finishing the measurement, the sensor can be easily retrieved and used again on another project (Figures 50 and 51).
 
Operation
The instrument is an intelligent sensor and, as such, the measurement results are digitally stored in the internal memory of the BAT sensor and later on downloaded to a PC for further analysis. 		 

    
 


   

 Plots
Figure 52 shows the data recorded from a BAT piezometer installed
using a mobile CPT rig. This data demonstrates the high degree of
accuracy and resolution achievable using these sensors. The data
clearly shows the tidal effect of a nearby river on the porewater
pressure. The term ‘mH2O’ on the vertical scale stands for the
porewater pressure in metres head of water. 
 

 
 
 

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