EFFECTIVE DEPTH OF SOIL COMPACTION UNDER A CONTROLLED COMPACTIVE EFFORT AT LABORATORY SCALE
Date
2011-08-26Author
Tascon, Andres
Department
Civil and Environmental Engineering
Advisor(s)
Fratta, Dante
Metadata
Show full item recordAbstract
Embankment construction specifications in the State of Wisconsin indicate that compaction
lifts cannot be thicker than 20 cm. This specification was established several years ago based
on field experience when compactors were lighter and smaller than the equipment used today.
Lift thickness may be increased to save construction time and cost when heavier and larger
compaction equipment is used. In this research effort, the possibility of increasing lift
thickness specifications in the construction industry without compromising the embankment
stability is explored by developing a methodology to evaluate engineering properties of
compacted soils.
A laboratory soil compaction test was designed to compact soil under controlled compactive
efforts while monitoring mechanical soil properties before, during and after compaction. The
soil underwent eight compaction passes. The soil properties were monitored using techniques
including nuclear density gauge (NDG), soil stiffness gauge (SSG), dynamic cone
penetrometer (DCP), P-wave velocity tests, and MEMS-accelerometers rotations. Soil
density, stiffness, shear strength, and deformation profiles were thus measured as a function
of the compactive effort, soil type, water content, and lift thickness.
Thicker lifts results in greater soil surface displacement but less volume change and less
uniform compaction than thin lifts. Furthermore, thin lifts undergo larger strains and yield
greater stiffnesses than thick lifts. A comparison of the laboratory tests performed in this
study with a real soil compaction monitoring experiment shows that, despite the differences
in scale, density in thick lifts decreases with depth, and shows regions of low density at the
bottom of the lift. Soils with larger shear strength results when are compacted closer of the
optimum water content. Analysis of the stiffness measurements shows that the use of the
SSG in embankment construction using thin lift should consider the influence of the stiffness
ratio between the lift and the underlying layer. The effective depth of influence of the
compactor used in this laboratory study reached about 15 cm; where, as for field operations
using a compactive force that is 22 times larger, the influence reaches 30 to 40 cm.
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http://digital.library.wisc.edu/1793/54509Type
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