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Determination of the Soil Failure Zone around a Cone Penetrometer
Published by the American Society of Agricultural and Biological Engineers, St. Joseph, Michigan www.asabe.org
Citation: Paper number 051158, 2005 ASAE Annual Meeting . (doi: 10.13031/2013.19796) @2005
Authors: Leroy Ortega Garciano, Shrinivasa K. Upadhyaya, Randolph A. Jones, Sarah R. Jersey
Keywords: Cone penetrometer, pressure sensing mat sensor, soil failure zone or zone of influence
The objective of this paper is to investigate the soil failure zone (zone of influence) around
a cone penetrometer using a pressure sensing mat under laboratory conditions. The investigation
was conducted under (1) constrained conditions using cylindrical split pipe molds and (2)
unconstrained conditions using a soil box. These tests used two types of soils Capay clay and
Yolo loam under two moisture conditions and two compaction levels. These soils were ground and sieved using a #20 sieve. Thus five factors were considered in the study test conditions
(constrained versus unconstrained), cylinder diameter, type of soil, soil moisture content and level of
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In the constrained test, maximum radial pressure of 111 kPa was observed in Capay clay of 3.4 to
4.3% moisture content with 3 blows of compaction (cone index value of 2040 kPa) when using the 51
mm diameter split pipe mold and decreased to 82 and 22 kPa when using the 76 and 104 mm
diameter molds respectively. These maximum radial pressures that developed on the wall of the soil
column are associated with the soil failure zone (zone of influence) around a cone penetrometer.
The higher the radial pressure the greater the soil failure. The result of these tests suggests that the
soil failure zone (zone of influence) of a cone penetrometer has a radius of 51 mm from the center of
the cone penetrometer shaft.
In the unconstrained tests, maximum pressure of 9.01 kPa was observed in the Capay clay of 4.5%
moisture content with 3 blows of compaction (cone index value of 550 kPa) and then decreases as
the distance of the cone shaft is further from the wall of the soil column. The zone of influence of the
cone penetrometer was observed at a distance of 76.2 mm from the center of the cone penetrometer
shaft with pressure readings in the range of 0.07 to 0.36 kPa. The pressure levels from these tests
are much smaller than in the constrained tests and may suggest that the soil failure zone under field
conditions is small.
The over-all results of the constrained and unconstrained tests suggest that the soil failure zone
(zone of influence) of the cone penetrometer has a radius of about 76.2 mm from the center of the
cone penetrometer shaft. In both tests soil behavior showed similar tendencies that is, increase
number of blows (higher density of soil) led to higher pressure. On the other hand, increasing soil
moisture content tended to decrease the maximum pressure.