Note: Descriptions are shown in the official language in which they were submitted.
CA 02447157 2003-11-17
WO 01/88529 PCT/USO1/15638
Monitoring Fill Soil via Compactor Rolling Resistance
TECHNICAL FIELD
This invention encompasses new methods for and in earthen fill engineering
and construction and includes application to treated and amended soils for
subgrades
and base courses. More specifically this invention involves new and different
methods to determine, use, and model in the laboratory, actual field
compaction
energy generated by all combinations of compactors, soil types, lift
thickness',
moisture contents, and soil amendments; and the application of these methods
in
engineering design, specification, and construction control methods, based on
methods to derive and correlate rolling resistance energy, cumulative
compaction
energy, soil moisture, density, and geotechnical engineering properties.
BACKGROUND OF THE INVENTION
In current engineering practice (involving applicable soils), the
specification
and control of density and moisture of earthen fill is typically based on the
results of
the Standard Proctor compaction test (American Society for Testing Materials
[ASTM] D698) or the Modified Proctor compaction test (ASTM D1557), or other
similar test standards derived from the Proctor tests and established by other
institutes
and governments (i.e. AASHTO, etc.). All standard tests used in current
practice
utilize fixed soil compaction energies. The compaction energy used in the
standard
proctor compaction test is 600 kilonewton-meter per cubic meter Kn-m/m3 or
12,400
foot pounds per cubic foot (ft-lbs/cf). The other standard tests based on the
Standard
Proctor Test use the same or comparable fixed energy levels. These standard
tests are
based on work by R. R. Proctor, who estimated field compaction energies of
towed
CA 02447157 2003-11-17
WO 01/88529 PCT/USO1/15638
2
compactors (or rollers) used in the early 1930's. These fixed compaction
energy
levels were based on drawbar pull values measured with towed compactors, and
considered to be somewhat representative of field compaction energies.
Subsequently, it was found that high fills constructed by using the standard
proctor
energy experienced substantial compression under their own weight. This fill
compression combined with the development of aircraft and truck traffic with
heavier
wheel loading led to the development of the Modified Proctor compaction test
by R.R.
Proctor (ASTM D1557). Hunt, R. E. (1986) Geotechnical Engineering Analysis and
Evaluation, McGraw-Hill Book Co., p.211. The compaction energy used in ASTM
D1557 (2,700 Kn-m/m3, or 56,000 ft-lbs/cf) is about 4.5 times higher than the
compaction energy used in ASTM D698.
Even in the 1930's and 1940's it was recognized that the laboratory
compaction tests produced energies that were inconsistent with field
compaction
energies. Numerous attempts were made to develop test procedures that produced
laboratory compaction (moisture-density) curves that would be more comparable
to
actual field curves. The present inventors have published a very basic
approach to
improved procedures: 1.) "Practice Improvements for the Design and
Construction of
Clay Barriers", Proceedings of the Eighth Annual Conference on Contaminated
Soils", University of Massachusetts at Amherst, 1994; and Geoenvironment 2000
Conference, New Orleans, Louisiana, 1995; and 2.) "Practice Improvements for
the
Design and Construction of Earth Fills", Proceedings of the Texas Section Fall
Meeting, 1995, American Society of Civil Engineers, El Paso, Texas. There has
not
previously been available in practice test methods or standards that are based
on a
compactor energy parameter other than the drawbar pull parameter. There has
not
previously been available in the art practicable methods to derive actual
cumulative
field compaction energies unique to each site based on soil/compactor/lift
thickness/moisture/soil amendment combinations, a data matrix developed to
provide
actual field combination-specific compaction energy levels and engineering
property
correlations based on variable soil/compactor/moisture/lift thickness
combinations, or
to allow extrapolation for intermediate combinations or compaction conditions,
with
or without field data, or to select field-specific compaction energy levels to
be applied
CA 02447157 2003-11-17
WO 01/88529 PCT/US01/15638
3
in laboratory tests or utilized in engineering methods, rather than the fixed
energies of
the standard test methods described above. All engineering methods and
standards in
current practice are based on laboratory test methods or standards that
utilize fixed
compaction energy levels. The new improvements provide a different method for
modeling of actual, combination-specific field compaction energies in the
laboratory
that are not fixed, and provide for design applications and specifications,
and
construction, for all types of compactors combined with all classes of earthen
fills
(having a suitable fines fraction) moisture states, lift thickness', and soil
amendments.
The new improvements are based on rimpull energy, a different compactor energy
parameter than drawbar pull, which is the parameter used in current practice.
SUMMARY OF THE INVENTION
The invention is based on rimpull compactor energy instead of drawbar pull
energy in current practice. The invention is based on cumulative compaction
energy
levels that vary with site conditions and/or engineering needs, instead of
fixed
cumulative compaction energy levels that do not vary with site conditions or
engineering needs. The invention provides for a different method for
determining
compaction energy and associated moisture-density/engineering property
relations for
any given combination of soil type, compactor, moisture state, lift thickness,
and soil
amendment, by tracking energy distribution, determining field-specific rolling
resistance and correlating such determinations to cumulative compactive energy
loss
and engineering properties of the compacted lift, under practical and
controlled
construction conditions. The invention establishes these different methods by
factoring lift thickness, soil moisture content, and soil amendments with the
soil/compactor combinations, and the variations thereof, as opposed to any
methods
based solely on soil/compactor combinations, and by including other methods
that
differ from prior art. The different methods include determining the unit
cumulative
compactive energy per unit volume at the asymptotic energy-density approach
for
3o each rolling resistance field trial by using the cumulative average rolling
resistance
according to each parabolic data curve, in contrast to the prior published
method
CA 02447157 2008-10-02
4
(Tritico/Langston, 1994,1995) of using the cumulative linear average rolling
resistance. The different methods further include determining the "design
energy
level" for (/-Ulaboratory modeling based on establishing a specific percentage
density
sector of the derived moisture-density curves at or within the asymptotic
energy-
density approach, which is projected onto a corresponding roller compaction
energy
curve, in contrast to the prior art of selecting a random energy value based
on visual
observation of energy-density-moisture graphs. The specific density sector
method
involves a specific percentage value selected within the range of 85 to 100 %
of the
maximum density values on the derived moisture-density curves at or within the
asymptotic energy-density approach projected onto corresponding roller
compaction
energy curves. The selected percentage density sector is projected onto a
corresponding roller energy curve selected from the group of curves at or
within the
asymptotic energy-density approach. The new method further includes
determination
of the asymptotic energy-density approach based on combination-specific
results of
full-scale field trials including all combinations of lift thickness, soil
type, soil
amendments, moisture content, and compactor type, as opposed to the prior art
of a
generalized asymptotic energy-density approach of an 8-10 or 8-12 pass range
based
solely on the soil/compactor combination, and conventional expectations of
roller
"walls-out". The different, specific methods operate together to define the
new
method. The method may be applied to specific compactors such as determining
the
actual, cumulative field compaction energy for a compactor that is known under
the
commercial name of a Cat 815B compactor for a given soil, such as type CH,
with a
certain moisture state, lift thickness, and soil amendment type, and
correlation, use and
control of resultant engineering properties for new engineering and
construction methods.
In another embodiment the invention provides a data matrix of field
combination-
specific compaction energy correlation factors for various combinations of
soil type,
soil amendment, moisture content, lift thickness, and compaction rollers,
developed
with the new methods, and uses of the established data matrix to determine
field-
specific compaction energy correlations for untested field combinations. The
data
matrix may be used in conjunction with other improvements to extrapolate from
known values to untested field combinations based on extrapolation of data for
tested
CA 02447157 2008-10-02
soils or equipment. The invention may also be viewed as a data matrix
comprising a
set of actual field compaction energy correlation factors for various soil
densities,
moisture contents, and other engineering properties for a plurality of soil
types, a
plurality of soil compactors, a plurality of lift thickness', a plurality of
soil
5 amendments, or a plurality of all the above. The invention includes new
engineering
and construction methods which utilize a data matrix to provide an alternate
method
for computing design compaction energy and extrapolations and/or interpolation
of
correlating engineering data established in the data matrix, for laboratory
modeling,
engineering design and specifications, and/or construction testing and
controls. The
new methods include generation of the data matrix based on the new methods
outlined
above and novel methods for 'determining specific asymptotic energy-density
approach ranges from data sets of rolling resistance trials based on field-
specific
combinations of soil types, compactors, moisture contents, lift thickness',
and soil
amendments. The new method includes utilization of asymptotic energy-density
approach ranges, constituting ranges of 2 to 5 passes, from within the group
of 6 to 20
passes, as opposed to a sole soil/compactor combination basis, or
generalization of an
8-12 or 8-10 pass range. The invention may also be viewed as a data matrix,
based on
and utilized as and a part of, the new and different methods outlined herein,
comprising a set of field combination-specific rolling resistance energy
correlations
for a plurality of soil types, compactors, lift thickness', moisture contents,
and soil
amendments, and relating associated maximum soil densities, optimum moisture
contents, and other engineering properties, and the data is displayed or used
for new
engineering and construction control methods, and in a manner that permits
determining values for additional field combinations by extrapolation, or
actual field
trial.
BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 is a plot of the change in rolling resistance and density with roller
passes
based on rimpull energy of a compactor that is known under the commercial name
of
Caterpillar Model 815B compactor combined with a "CH" soil, for a typical
field trial
developed by the Inventors.
CA 02447157 2003-11-17
WO 01/88529 PCT/USO1/15638
6
DETAILED DESCRIPTION OF THE INVENTION
Definitions
"ASTM" means American Society for Testing Materials.
AASHTO means American Association of State Highway and Transportation
Officials
Compaction Energy means the energy component that is transferred by a
compaction
roller into the ground over which it is travelling, and represents the energy
that causes
soil densification.
"Asymptotic Energy-Density Approach" means a segment of. a data set of rolling
resistance-density curves, as a function of specific combinations of soil
type, lift
thickness, moisture content, compactor type, and soil amendment, wherein the
incremental change in rolling resistance and corresponding soil densification
begins to
be insignificant with successive roller passes.
"Best fit curve" means the curve plotted through a set of data points that
best fits the
data trends and variations by methods of bilinear or curvilinear approximation
or
averaging, and educated visual extrapolations.
"Cumulative avera eg rolling resistance" means the rolling resistance measured
by the
method of example 2 below.
"Design energy level" means a cumulative compaction energy level considered to
be
representative of actual field energies produced by compactor-soil-moisture-
lift
thickness-soil amendment combinations, at a select point within the novel
asymptotic
energy-density approach, computed by the method of example 3 below. The Design
Energy Level is used for laboratory compaction testing and other engineering
applications. In laboratory compaction testing, the design energy level is
utilized in
procedures of a Standard or Modified Proctor test (and standard variations
thereof) by
varying the fixed energy specified in the standard test procedures to utilize
the design
energy.
CA 02447157 2003-11-17
WO 01/88529 PCT/US01/15638
7
"Rolling resistance" is defined as the fraction of rimpull energy needed to
overcome
energy loss into the earthen lift being compacted, as determined using
compactor
rimpull curves provided by the equipment manufacturer.
General description of the Invention
Figure 1 represents a basic, prior art (Tritico/Langston) illustration of
rolling
resistance vs. soil densification with roller passes, produced by a given soil-
compactor
combination. As reflected in the figure, rolling resistance reduces, as the
soil
densifies with each roller pass. Both rolling resistance and soil density
reach
asymptotic states at the same rate. This effect is the result of decreasing
soil
deformation with increasing compaction.
The inventors published that compaction energy transferred from a wheel-
ground system is a function of rolling resistance and that rolling resistance
is a
function of the compactor's rimpull energy as opposed to drawbar pull energy.
Current practice is based on drawbar pull energy as authored by R.R. Proctor
in the
development of standard methods.
The invention encompasses new and different methods for determining
actual, cumulative field compaction energy based on rolling resistance
measurements
as a function of rimpull. energy, and by relating rolling resistance to
compactor type,
dry density, moisture content, lift thickness, soil type, and soil amendments,
with each
roller pass; as opposed to measuring rolling resistance or estimating
compaction
energy based on just a soil/compactor combination with each roller pass. The
invention includes the correlation of engineering properties of compacted
soils to the
actual cumulative compaction energy levels, as opposed to fixed energy levels
and
standard practices. The invention also includes methods for and of the
development
and utilization of data matrices of these correlations in and for different
engineering
design, construction, and construction testing and control methods, as opposed
to
standard practices.
Example 1
CA 02447157 2003-11-17
WO 01/88529 PCT/US01/15638
8
In a field test program the rolling resistance of a wheel/ground system
suitable
for earthen fill construction is measured relative to soil type, compactor
type, soil lift
thickness, moisture content, dry density, soil amendments, and roller passes.
A
specific test pad design is built with a certain soil type at different loose
lift thickness',
moisture contents, and soil amendments. Various earthwork compactors are used
for
the test and the compactor's performance parameters and specifications are
recorded.
The field test program consists of a series of at least three test trials. For
each lift
thickness, initial moisture content, soil type, soil amendment, and compactor
type,
each trial involves the determination of rolling resistance, soil dry density,
and soil
moisture content with each roller pass, and other engineering properties at
and within
the asymptotic energy-density approach range. Each trial is conducted with a
different
initial moisture content in order to test a range that encompasses the true
optimal
moisture content for the energy being applied, and to test for specific
moisture
contents for correlation with certain engineering properties based on soil
type and for
purposes of engineering design requirements and the new engineering methods.
Each
trial is continued until changes in field measurements are clearly extended
through the
full asymptotic energy-density approach range and the full range is clearly
defined.
Rolling resistance is measured based on test pad configuration and rimpull
performance using rimpull performance curves for the test compactors. The data
from each trial are plotted in a manner similar to that shown in figure 1. The
asymptotic energy-density range is determined from the plots for the range
needed
depending on the application of the novel engineering methods. Rolling
resistance is
based on measurement of rimpull energy performance in each test trial. Best
fit
curves of dry density vs. rolling resistance with each roller pass are
developed in
graphical and tabular form. Based on the combination-specific results in the
plots,
for each trial, novel asymptotic energy-density approaches are determined as a
range
composite of 2 to 5 passes, within a pass range of 6 to 20 passes; as opposed
to
generalization of an 8-10 or 8-12 pass range based solely on a soil/compactor
combination. The methods include selecting a pass interval in the novel
asymptotic
3o energy-density approach, to determine cumulative average compaction energy
levels
in order to determine a "design compaction energy" (or a select unit
cumulative
CA 02447157 2003-11-17
WO 01/88529 PCT/US01/15638
9
compaction energy per unit volume) from combination-specific moisture-density,
and
moisture-energy curves, based on and for use in novel methods. Selection of
the pass
interval in the novel asymptotic range is based on the project-specific needs,
criticality, and factor of safety intents in practical application of the
methods. The
prior art (published by the current inventors) for determination of the
"design energy
level" was based on selecting a random, generalized energy value based on
visual
observation and averaging of energy-density-moisture graphs, based solely on a
soil-
compactor combination, at a generalized asymptotic energy-density approach of
8-10
passes. The novel "design energy levels" are determined based on the multitude
of
field combinations and resultant asymptotic approach intervals and used for
modeling
in laboratory compaction testing, and correlation with engineering properties
of
corresponding compacted lifts. These data are correlated for the development
and
utilization of a data matrix of field combinations, and to provide new
engineering and
construction control methods based on using the data matrix to derive
engineering
specifications and laboratory test procedures that will better control
engineering
requirements, and more nearly match actual field conditions than do prior art
methods. The method correlates observed field combinations that include soil
type,
compactor type, lift thickness, moisture content, and soil amendments; as
opposed to
measurements based only on soil type and compactor type as suggested in the
prior art
(developed by Inventors).
Example 2
The invention includes a method for computation of cumulative average
rolling resistance for each field trial from the best fit parabolic data curve
formed by
the trials. This is accomplished as follows:
For each rolling resistance vs. dry density curve produced by plotting the
measured results for several data points in each pass of each field trial, new
compaction data is drawn directly from the best fit, parabolic curve formed by
plotting
the rolling resistance variance with roller passes. Along the line of the
curve, rolling
resistance values for each wheel pass are drawn directly from the curve, for
cumulative averaging. The cumulative averages are made with values taken from
the
first wheel pass up to the select pass at or within the novel asymptotic
energy-density
CA 02447157 2003-11-17
WO 01/88529 PCT/US01/15638
approach. The cumulative averages representing values at the novel asymptotic
energy approach are then used for computing unit cumulative compaction energy
per
unit volume or "design compaction energy" values. This method contrasts with
the
prior art method of linear averaging of cumulative rolling resistance from the
curve
5 and the, generalized asymptotic energy-density approach of 8-10 passes.
Example 3
The invention includes a method to determine the novel "design energy level"
based on selection of a specific percentage density sector of the derived
moisture-
density curves at or within the novel asymptotic energy-density approach,
which is
10 projected onto a corresponding roller compaction energy curve. This is
accomplished
as follows:
Using novel curves of roller compaction energy vs. moisture content,
superimposed with dry density vs. moisture content, covering the novel
asymptotic
energy-density approach, a specific percentage density sector is selected or
"notched"
out of the select or corresponding density curve(s) in order to define a
"design range"
of moisture contents. The specific percentage value is selected within the
range of 75
to 100% of the maximum density values on the derived moisture density curves,
preferably 80 to 100% more preferably 85 to 100%, based on engineering needs
with
the new engineering methods. These needs include project-specific criticality
and
factor of safety requirements in practical application of the new methods.
This
"design range" per novel selection methods is then projected onto the
corresponding
roller compaction energy curve(s) on the same chart. The intercept sector
formed by
the design range projection onto the roller energy curves is then used to
derive a
"design energy level" by direct reading from the chart, and is used for
laboratory
simulation of field compaction energy and the other novel methods described
herein.
Example 4
A data matrix that cross-matches some or all combinations of compactor and
soil types or amended soils, for each and any combination of lift thickness
and
moisture content, including combination interpolations is developed and used
in the
methods of the invention. A data set within each cross-match within each
matrix
CA 02447157 2003-11-17
WO 01/88529 PCT/US01/15638
11
includes the following corresponding data values: "design energy levels" or
actual
cumulative field compaction energy levels covering the percentage range of
selected
density sectors, the asymptotic energy-density approach ranges, maximum dry
density
values, optimum moisture content values, energy correlation factors for
laboratory
testing, factor of safety values for engineering uses, and any and all
engineering
properties for the corresponding compacted lift product. Examples of other
engineering properties are shear strength, modulus, consolidation, CBR,
permeability,
index properties, etc.
Using novel methods described herein, novel design energy levels and
correlation factors for all said field combinations and interpolations are
tabulated in
cross-matrices. The factors are used as multiplying factors for modeling field
compaction energy whereby the factor is used to adjust standard laboratory
compaction testing to model actual, combination-specific compaction energy of
earthen fill materials. Also included in the matrix are the novel asymptotic
energy-
density approach ranges and all other said engineering properties which
correspond to
the compacted lift product. The novel matrix is also used as a part of the new
methods to interpolate or extrapolate between cross-matrix values for untested
field
combinations.
Example 5
The novel data matrix of example 4 is also used as a part of the new method to
model
actual, cumulative field compaction energy (or "design energy levels") in the
laboratory for production of field-representative moisture-density compaction
curves,
or to assess compaction energies for other engineering uses. The novel
compaction
energy values drawn from the novel matrix are based on the novel asymptotic
energy-
density approach ranges and percentage density sectors, for any combination of
the
novel field parameters (soil type, compactor type, lift thickness, moisture
content, and
soil amendment). For utilization or modeling of novel design energy levels in
laboratory compaction testing, the novel energy correlation values or
multiplying
factors are applied to the height or number of hammer drops in the Standard or
Modified Proctor Test procedures, or other standard test procedures derived
from the
CA 02447157 2003-11-17
WO 01/88529 PCT/US01/15638
12
Proctor Test standards, to model the novel compaction energy in the procedure
instead
of the specific fixed energy levels produced by the standard test procedures.
With the
modified laboratory compaction testing based on novel compaction energy values
and
associated methods to determine and use the energy values, field combination-
specific
moisture-density compaction curves are produced for practical application.
