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Clayey silt (Ut3)
Site: Groß-Gleidingen near Braunschweig; soil type: clayey silt (S: 1%, U: 82%, T:17%); measurements: Prak-
tikum Bodenphysik at TU Braunschweig, 2010. Evaporation: 14 mm/d using a fan. Temperature: 20°C
Description of the measuring process
The measurement process is typical of a very fine grained substrate.
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The water tensions rise spontaneously immediately after the start of mea-
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surement, steeply and continuously. This reflects a very small proportion of
coarse pores. pF 2.0 is reached (under the given conditions with fan) after
a few hours. The loss of water to pF 2 is only about 4%.
The "spikes" at the beginning of the measurements shows the discontinuous
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access of air penetrating into the soil.
From 100 hPa (pF 2.0), the first parallel tensio shafts are far enough away to
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allow for the determination of hydraulic conductivities.
Both tensio shafts rise unabated with the passage of time and failed relatively
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soon. The clayey silt has few large middle pore, the finer middle pore region is
in the time of failure still filled with water, the water content is therefore high.
The spread of the tension values is moderate over the entire measuring
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process, which indicates a relatively high unsaturated conductivity.
The measurement is completed due to the failure of the upper tensio shaft
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after less than one day. At this time the sample has lost about 20% water.
85 | Addendum
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