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| Description of the experiment |
During a project on preferential flow paths at the Department of Geophysics
at the University of Kiel, Germany, a time-lapse infiltration experiment
has been carried out in a full scale model.
The aim of the experiment was to map water movements in the shallow
subsurface in high spatial and temporal resolution under controlled circumstances.
A comparable experiment was conducted in 1991 in Borden,
Canada.
Our experiment differs from the "Borden" - experiment in a higher
sampling interval (1 cm instead of 5 cm inline and 4 cm instead of 100
cm crossline), the use of water instead of trichloroethylene as infiltration
fluid, a dry sand body instead of a water saturated one, a smaller amount
of spilled fluid (65 litres instead of 770), a faster repetition rate of
the measuring cycles (30 minutes instead of 8 hours) and a smaller length
of total measuring cycles (30 minutes instead of 8 hours) and a smaller
length of total measuring time (7 instead of 914 hours).
The experiment was conducted at the field laboratory of the Institute of Geophysics and the Institute for Water Management and Landscape Ecology of the University of Kiel. The test site consisted of a sand box (surface: 7 m x 5 m; base: 5 m x 3 m; depth: 2.0 m) filled homogeneously with sand. To protect the site against effects of the weather it was isolated with a plastic foil and sheltered with a tent. At the base of the box a layer of 40 cm of gravel was included to collect the outflow. Immediately above this layer of gravel in a depth of 2 m a horizontal lying electrode lattice with 220 electrodes was situated for geoelectric measurements.
Tap water was pumped with an electrical pump from a water reservoir
via a small plastic tube (diameter 1.1 cm) into the centre of the survey
area. The tube was buried in the sand 5 cm below the surface. On an area
3 m x 1.2 m wide 30 GPR profiles were measured with 500 and 900 MHz GSSI
antennas. Both antennas were mounted on a motor driven sledge and pulled
with constant speed. Positioning took place with a punctured tape measure
and a photoelectric barrier. The sampling grid was 1 cm inline, 4 cm crossline
and 470 samples in time with a sampling rate of 0.119 ns.In the beginning
a complete data volume consisting of 30 parallel profiles was recorded
over the dry sand volumeer the dry sand volume. Afterwards 11 further data
sets were measured continuously in time with a steadily increasing amount
of infiltrated water. The registration of one data set required in average
23 minutes. Within 5 hours approximately 65 litres of water were infiltrated.
| Visualisation |
To visualise the 3D data volumes of the 500 MHz antenna animations were
created:
- 12 timesteps of the infiltration taken at the centre profile. See the waterfront spreading downward. (0.7 MB) ("Zeitschritt" is german and means "timestep" ;-)
| Download |
Please contact me if interested in the following files:
Diploma thesis in German (Abstract in English)
PowerPoint Presentation given on the International Conference on GPR
in Archaeology in Nara, Japan (February 17th 2001)
| Contact |
Bullard Laboratories
Madingley Road
Cambridge CB3 0EZ
United Kingdom
phone: +44 (0)1223 337098
eMail: MY_LASTNAME@esc.cam.ac.uk
MY_LASTNAME is trinks