WATER JET CONFERENCE - Waterjet Technology Association

LABORATORY INVESTIGATION OF
SOIL CUTTING WITH A WATER JET
121
by
Dimitrios K. Atmatzidis
Professor, Department of Civil Enqineerinq,
University of Patras, Greece
and
Frederick R. Ferrin
Captain. U.S. Army Corps of Engineers
ABSTRACT
Limited information is available regarding the effect that soil properties have on
the penetration or excavation efficiency of high speed water jets. It may be inferred from
research on materials such as coal and rock that material properties which could have an
effect on the cutting of soils should include grain size, density, degree of saturation,
permeability, and strength.
A continuous water jet with a driving pressure range up to 8,000 psi and a nozzle
diameter of 1 mm was used to conduct a total of seventy six cutting tests on soil samples
which were compacted in the laboratory. Four soils, ranging from a clean sand to a
predominantly clayey soil, were used to provide an adequate variation of soil properties.
The depth of penetration of the jet into the soil target was measured as a function of the
time of exposure, the degree of saturation of the soils, the dry density of the soils, and the
traversing velocity of the jet over the soil target
It is observed that the depth of penetration in a given soil is related exponentially
to the corresponding time from initial impact and to the corresponding traversing velocity
of the jet, and varies linearly with the coefficient of permeability of the soil. The degree of
saturation and the dry density of the soil affect the depth of jet penetration in a soil since
they affect the strength and the permeability of the soil. Increasing soil strength and
decreasing permeability result in decreasing depth of penetration, Finally, the volume of
soil affected by the action of the water let is larger than the actual hole or slot excavated
and increases with increasing soil grain size.
INTRODUCTION
Liquid jets have been used for more than a century to excavate and remove large
quantities of soil, utilizing rather low pressures and large volumes of water. It was not
until recently that soil cutting with a water jet received more attention and was considered
for application in specific field projects (Yahiro, Yoshida, and Nishi, 1974; Summers and
Zakin, 1975; Shibazaki and Ohta, 1982). A wealth of information is available in the
literature with respect to the design of a water jet nozzle, the factors affecting the
structure, coherence, and impact pressure of a jet, and the methods to improve the
efficiency of a jet. In contrast, extremely limited information is available with respect to
soil properties which may have an effect on the soil cutting efficiency of water jets.
However, research on the depth of jet penetration in permeable targets indicates that
penetration is primarily affected by the strength and permeability characteristics of the