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The new method:
The new method of measurement was developed to examine all kinds of either surface or subsurface horizontal profiles and their variations on time due to environmental influences. The method is based on the discontinual measurement of the hydrostatic pressure between predefined equidistant points (e.g. every 10 or 25cm) along test-pipes, congruently installed to the profile, and a known external reference level. The specially developed test-pipes with a diameter of ca. 20mm and a longitudinal extension of up to 500m workes as a protecting cover for several inside tubes and cables for signal transmission, which are needed during the measuring process.
The technical and electronic equipment of the measuring unit is housed in a compact and portable alloy case, which is connected to one end of the test-pipe that has to be evaluated. After starting the measurement the tube in the test-pipe is automatically filled with degased water in presetable increments of length. Each time one increment is filled, the hydrostatic pressure in relation to the reference level is measured by a pressure transducer and digitally recorded in a datalogger. The whole process runs automatically until a sensor signals, that the water has reached the end of the test-pipe.
After the measurement the water is automatically pumped out of the tubes. The test-pipe remains in position for further measurements to survey alterations in the profile, that is represented by the test-pipe.
To compensate variations on the specific weight of water, which depend on variens temperatures, this parameter is also measured and taken into account when a quasi continuous level profile is finally evaluated from the results of the pointwise hydrostatic pressure measurement.
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