The grain size distribution curve was produced by, first sieving out the coarse material and then
finding the finer particle fractions using a laser diffractor. Before the analysis, the samples were
prepared. There was no dividing of the samples in the lab, as the field samples were small enough to
be processed in their entirety. The samples were placed in marked and pre weighed containers and
dried overnight in an 80◦C oven. After drying, any visible organic material such as leaves and roots
were removed.

All the samples were distributed according to the NS ES ISO 14688-1 standard. Sieving gives a grain size distribution based on weight percentage. The samples were sieved following
The Norwegian road authority’s handbook on laboratory investigations. The dried
soil samples were sieved using 16000, 8000, 4000 and 2000μ m square mesh sieves. All four sieves were
staked on top of a bottom pan and thoroughly shaken. Each sieve was then, individually, shaken above
an A3 paper and any material slipping through were added to the sieve beneath. Each size fraction
where weighed. A brush and a putty knife were used to remove smaller particles from larger clasts.
The fraction of soil smaller than 2000 μ m was then analyzed using a Coulter laser diffraction analysis.

A Coulter test gives grain size distribution of particles between 0.4 and 2000 μ m. This test gives a
grain size distribution based on volume. The volumetric representation will only be comparable to the
weight-based distribution if the sample material has the same density in all fraction sizes. The method
also assumes all grains to be spherical.

The laser works by suspending the particles from the soil sample in water and shining a light
through the stream. The suspended particles scatter the light and the scatter pattern is picked up
by the machine. The scatter pattern represents the intensity of scattered light as a function of the scatter angle. The resulting pattern is a cumulative pattern representing all the particles in the sample.
The laser used in this thesis was a Beckman Coulter LS 13 320 Laser Diffraction Particle Size
Analyzer provided by the sedimentology lab at the University of Oslo. Before each test, the laser was
thoroughly cleaned and the background level of particles in the water was measured. If the level was
too high, another cleaning cycle was initiated. The soil sample was mixed well, and a small sample
was extracted for each test. The laser needs an obscuration between 8 and 12 % and this was obtained
by adding between 0.3 - 0.8 g of the sample. Before the sample was added to the laser, it was placed
in a small beaker with 5-10 ml of 5 % Calgon (Natriumpyrophosphate). The beaker was then placed in
a ultrasonic bath for about 5 min to ensure than no particles were stuck together.
There were performed at least two tests on each soil sample. If the two tests varied from each other
by more than 5 %, a third test was performed. Once the grain size distributions varied less than 5 %,
the tests where averaged and the result used to make cumulative grain size distribution.

In order to get a complete grain size distribution, the results from the sieving and Coulter test
were combined. The volume percent from the Coulter test was multiplied by the weight percent of
the fraction below 2000 μ m. The real volume percent and cumulative percent after
correction could then be found.

The angle of repose was measured using the method outlined in Miura et al. (1997). The soil
samples were thoroughly mixed and placed in a funnel. The funnel was consequently lifted vertically
ensuring constant contact with the top of the forming cone of soil. A picture at a perpendicular angle
to the cone was taken with a scale in mm. The height and width of the cone was then read from the
picture. The experiment was done three times for all samples and the results were averaged.