The Delft Sand, Clay & Rock Cutting Model, 2019a

12.8. Experiments.
A Wedge in Saturated Sand Cutting.
Sand cutting tests have been carried out in the Laboratory of Dredging Engineering at the Delft University.
The cutting tank is a concrete tank with a length of 35 m, a width of 3 m and a depth of 1.5 m. The bottom of the
tank is covered with a drainage system. Above the drainage system is a layer of about 0.7 m sand (0.110 mm). On
top of the sand is a layer of 0.5 m water. Other soils than the 0.110 mm sand can be used in the tank. On top of the
tank rails are mounted on which a carriage can ride with speeds of up to 1.25 m/s with a pulling force of up to 15
kN, or 2.5 m/s with a pulling force of 7.5 kN. On the carriage an auxiliary carriage is mounted that can be moved
transverse to the velocity of the main carriage. On this carriage a hydraulic swell simulating system is mounted,
thus enabling the cutting tools to be subjected to specific oscillations. Under the carriage dredging equipment such
as cutter heads and drag heads can be mounted. The dredging equipment can be instrumented with different types
of transducers such as force, speed and density transducers. The signals from these transducers will be conditioned
before they go to a computer via an A/D converter. On the carriage a hydraulic system is available, including
velocity and density transducers. A 25 kW hydraulic drive is available for cutter heads and dredging wheels. The
dredge pump is driven by a 15 kW electric drive with speed control. With the drainage system the pore water
pressures can be controlled. Dredged material is dumped in an adjacent hopper tank to keep the water clean for
under water video recordings. In the cutting tank research is carried out on cutting processes, mixture forming,
offshore dredging, but also jet-cutting, the removal of contaminated silt, etc.
Figure 12-29: Cross section of the cutting tank.
The tests carried out in the Dredging Engineering Laboratory had the objective to find the failure mechanisms of
a sand package under large cutting angles of 60, 75 and 90. Main goal of the tests was to visualize the total
process in a 2-dimensional view. Besides, the behaviour of sand in front of the blade was to be investigated. As
mentioned before, some wedge exists in front of the blade, but it was not clear until now whether this was a
kinematic wedge or a dynamic wedge. Visualising the cutting process and visualising the velocity of the sand on
the blade has to improve the understanding of the processes involved.
The existing testing facilities have been used to carry out the cutting tests. With these facilities cutting depths from
3 till 7 cm are tested, resulting in an (effective blade height)/(cutting depth) ratio of 2.5 to 6, for the various angles.
Cutting velocities of the tests were from 0.1 m/s to 0.4 m/s for smaller and 0.2 m/s for the larger cutting depths.
These maximum velocities are limited by the maximum electrical power of the testing facility. In the first series
of tests the 2-dimensional cutting process is made visual by doing tests near the window in the cutting tank. The
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