1. BY:
ARYA RENDI FIRMANA
J1B 008 032

2. The properties of a soil which govern or dictate its resistance to
water erosion are numerous and difficult to understand. Many physical,
chemycal and mineralogical properties combine to give a soil its
individual characteristics of erosion resistance.
The objective of the study reported in this paper were to
determine the effect of campaction and other soil properties on the
erosion resistance of the soil.
First, the individual effect of various physical, chemycal, and
mineralogical soil properties on the erosion resistance of soil
was studied
Secondly, the combined effect of compaction and the various soil
properties on the erosive behaviour of soil was investigated.

3. Seven Texas soil were chosen for testing. They were select to
show various properties cohesion with which the physical, chemycal,
and mineralogical properties could be related.
The following soil were use :
 Amarillo fine sandy loam
 Houston black clay
 Reagen silty clay loam
 Lufkin fine sandy loam
 San saba clay
 Lufkin clay ( B-Horizon ) and
 Lake charles clay

4. EQUIPMENT
Hydraulic flume, the erosion
resistance of the soil was
determine in a 72-ft hydraulic
flume which was 2.5-ft wide and
1.33 ft deep. The flume was held
at a constant slope of 0.2 percent.
Clear plexiglass sides iun the
centre 24-ft section of the flume
permitted visual observation of
the soil during the test.
Sediment sampler,
sediment sampler were
taken to indicated when
soil erosion had begun. A
suspended sediment
sampler was located at the
downstream end of the test
section and consisted of
nine vertically spaced
sampling tubes. Samples
were wihtdrawn by a
siphon arrangement and
gave the vertical sediment
distribution in the flume.

5. To obtain comparative values of the erosion resistance of the siol, it was
necessary to measure the erosive force acting on the soil when they began to
erode. To do this, the tractive force acting on the soil for each flow rate was
determine. The tractive force is simply the shear force exerted on the soil by
the following water. It is expressed by the product of the slope of the energy
gradient and the unit weight of water.
PROCEDURES
Preparation of soil
samples
Physical soil testHydraulic test

6. Preparation of soil samples
Before the soils were tested in the hydraulic flume
they were passed trough a 0.2 in, screen. They were
then loosely places in the 18-ft test section where
they were leveled to a depth slightly higher then
the concrete slabs ubstream and downstream from
the tes section . This was to allow for settling after
wetting. No attempt was made to compact the soil
for the first test. The soil was then wetted and
allowed to drain for approximately 20 to 24 hr
before the hydraulic tests were begun.

7. Hydraulic tests
The actual hydraulic test procedure consisted of
increasing the flow rate by small increments until
the soil began to erode at a visable high rate.
After each increase and when the flow had
stabilized, sediment samples were taken and the
instrument reading recorded to determine the
tractive force. After the soil began erodin, the flow
was increased and additional three to four times
to make certaint complette bed failure had
occurred. The actual point at which the bed failed
was determine letter by analyzing the sediment
samples obtained during the tests. At the end of
the test, replicated soil samples were taken from
the bed to determine the void ratio, which
indicated the degree of soil compaction exiting.

8. Physical soil tests
The physical tests of the soil were ferformed in
accordance with the procedures of the American
Society of Testing Materials and with procedures
outlined in the Texas A&M University Soil Physics
Laboratory Procedures. The following physical
properties were obtained: the percent clay, the mean
particle size, the disperation ratio, the vane shear
streangth, and the plasticity index.

9. The rate at which the channel was eroding during each test was
calculated from the concentration of the sediment samples and the rate of
flow. The erosion rates were expressed as pound of soil eroded per
minute per foot of flume width. The critical tractive force for each test
was determined by plotting the channel erosion or degradation rate
indicated by both sediment samplers versus the corresponding tractive
force. The degradation rate was observed to increase linearly at a very
slow rate up to a point. Above this point it increased rapidly with
increasing value of tractive force.
1. Effect of compaction on erosion resistance of soil.
2. Effect of various soil properties on erosion resistance of soil.
3. Combined effect of compaction with various soil properties on erosion
resistance of soil

10. If we are to protect our soil against water erosion, it is essensial
to find the soil propertise which can most accuratly be use in
determining the erosion resistance of a soil for any given soil
condition. One important condition of a soil which is always
subject to change is the degree of compaction. In this study the
erosion resistence of Seven Texas soil was determined in a
hydraulic flume and was related to various soil properties.
Each soil was tested at three degrees of compaction, at three
values of void ratio.