COMPACTION CONTROL OF MARGINAL SOILS IN FILLS
Balasingam Muhunthan, Ph.D., P.E.
Professor
Department of Civil & Environmental Engineering
Washington State University (WSU)
Transportation Research Center (TRAC)
November 15, 2004
TABLE OF CONTENTS
Section
Page
Problem Statement
2
Background
2
Objectives
4
Benefits
4
Products
4
Implementation
5
Work Plan
5

Task 1
5

Task 2
5

Task 3
6

Task 4
6

Task 5
6

Task 6
7
Staffing Plan
7
Level of Effort
7
Facilities Available
7
Supporting Data
8
Work/Time Schedule
8
References
9
Budget Estimate
11
1
COMPACTION CONTROL OF MARGINAL SOILS IN FILLS
PROBLEM STATEMENT
One of the most pressing needs for research in the geotechnical area is on the issue of the use of
marginal soils (e.g. silts, soft rock, etc.) for fills and as backfill material for walls and bridge
abutments. The lack of availability of higher quality materials and the added costs for these
materials will eventually force engineers to use marginal soils when in the past these marginal
soils were replaced with materials of better quality. The two major issues with using marginal
soils are finding a suitable compaction control method for such materials and the use and
performance of these marginal soils.
BACKGROUND
Soil compaction is the cheapest and simplest method of ground improvement. It is the process of
increasing the soil unit weight by forcing particles into a tighter state reducing air voids by the
use of either static or dynamic forces. Compaction generally leads to better engineering
properties. Most of the engineering properties correlate well with dry density and moisture
content. Therefore, compaction control is achieved by using maximum density tests for
“granular” soils and the standard proctor tests for silts and clay backfills. These tests have not
yielded consistent results as criteria for constructing fills to obtain the desired level of
performance, especially when the fill quality gets marginal. Consequently, it is necessary to
develop additional criteria for the compaction control of these materials.
A recent study of the failure of Teton dam (Pillai et al. 2004) has brought forth the importance of
placement water content with respect to the plastic limit of soils. It was found that although the
uniform clayey silt used for the Teton core had a relatively high value for the liquid limit (LL 
23) and plastic limit (PL  19), the plastic index was relatively small (PI  4 or less).
Consequently, the liquidity index was very sensitive to the initial placement water content and its
subsequent changes in mechanical properties due to varying confining stress. This was found to
be a significant contributor to the cracking of the dam. Therefore, for clay-silt cores, it is more
prudent to have the construction specification refer to the placement water content with respect
to the plastic limit (PL), than of the optimum water content. Similar control parameters need to
be developed for marginal soils. In addition, since marginal soils contain a mixture of coarse as
well as fine particles, it is necessary to select other appropriate variables such as the silt or coarse
fraction that best control compaction properties.
Field compaction is hampered due to poor workability when the moisture content of the in situ
soil is wet of optimum and when weather conditions are not conducive. This is typically the case
in many wet weather regions of western Washington. Information on workability is highly
valuable for engineers to decide on the compaction process as well as guidance on when aeration
is feasible, and how to estimate what needs to be done and how long it will take to do that in the
various climatic conditions encountered in wet regions of the state of Washington and other parts
of the world.
2
The research on the feasibility for aeration and an estimate of the amount for reduction in
moisture content for soil compaction can benefit from the recent advances registered in the
biotechnology field. These studies have used both passive and active aeration. Some studies
have shown that temperatures above 45°C were attained in composite piles and peat within the
first 2 days using passive aeration (Fernandes et al. 1994). Studies have also shown passive
aeration to be just as effective as the active one with the proper design of aeration ducts, and
thus, the proper prediction of the convective airflow rates created by the temperature differential
between the compost and the ambient air (Barrington et al. 2003; Fernandes et al. 1994). The
relationship between the Grasholf number (Gr - ratio of buoyancy to viscous forces) and the
convective airflow rates has been used to size the aeration ducts for passive aeration in composts
(Barrington et al. 2003).
Research on identifying the workable range of soils for tillage has also advanced in the past few
years (Hoogmoed et al. 2003; Cadena-Zapata et al. 2002; Dexter and Bird 2001) and the
proposed research on soil compaction will make use of some of them. The assessment of
workability of soil is usually linked to consistency based on Atterberg Limits (Casagrande,
1930). Dexter and Bird (2001) using the shape of the water retention curve as a basis have
proposed an alternative approach for the determination of workability limits. The limitation of
this approach is the need for a detailed soil water potential or pF curve. Hoogmoed et al. (2003)
have proposed simpler laboratory tests to determine the wet workability limit using air
permeability tests (Perdok and Hendrikse 1982) and the interpretation of the moisture pressure
volume diagram (Lerink 1994). A comparison of methods for estimating maximum moisture
content for optimum workability has been presented by Mueller et al. (2003). The number of
workable days can be calculated by combining a simple water balance derived from daily
climatic data applied to soils (Rounsevell, 1993: Cadena Zapata et al. 2002; Hoogmoed et al.
2003). The PLs and SLs of the different soils or other workability limits can be used as
thresholds in such calculations of workable periods.
One of the methods with potential for rapidly and economically improving the properties of wet
soils is the stabilization using additives such as quick lime or calcium oxide (CaO) (Sherwood
1993; Bergado et al. 1996) and cement (Bergado et al. 1996). Quicklime has a dual effect when
added to wet clay (Rogers et al. 1997):
(a) It reacts exothermically with water in the clay, causing drying both by chemical reaction
and by the production of steam. This occurs almost simultaneously.
(b) It changes the fundamental properties of the soil, so rendering it less susceptible to future
changes in water content. These changes occur within 24-72 h. Further changes occur
with time, given the application of sufficient lime and compaction.
For economic design an engineer must know how much lime is required and how long it will
react. The initial consumption of lime (ICL) test is conventionally used to assess the minimum
quantity of lime required to cause long-term changes (Eades and Grim, 1966). The ICL test,
however, has been shown to produce results that can be inconsistent and excessively
conservative (Rodgers et al. 1997; Rogers and Glendinning, 2000). Alternatively, it has been
suggested to use the full pH against lime addition curve in order to get better estimates of lime
requirement (Rodgers et al. 1997).
3
While lime technology has been used with success for pavement subgrades, very little
information is available for use in fills of significant size. The stress, strain, and pore pressure
response under large fills is critically dependent on the drainage conditions and stress paths.
Therefore, it is necessary to study in detail the compressibility and strength behavior of marginal
soils as well as lime treated soils in order to predict their behavior with confidence in large fill
applications.
OBJECTIVES
The overall objective of the proposed research is to develop effective compaction methods and
control measures to ensure sound engineering performance of fills constructed using marginal
soils. The specific objectives are to:
i)
Develop laboratory control test parameters that can better quantify field compaction
performance of marginal soils.
ii)
Develop methods that can identify the feasibility of the use of passive and active
aeration to facilitate compaction in wet zones.
iii)
Investigate the workability limits of soil compaction based on climatic data.
iv)
Investigate methods to quantify the effectiveness of the use of lime addition in fill
applications
BENEFITS
The proposed research will provide suitable compaction control measures and guidelines for
state and federal highway engineers and technicians towards the use of marginal soils in the
construction of fills. It will contribute to improved public safety and effective use of fiscal
resources for management/maintenance of our nation’s highway infrastructure.
PRODUCTS
The following products will be provided to the research sponsor:
 Quarterly progress reports
 Draft and final (camera-ready) project report
 One-page project summary
 Two conference papers or refereed journal articles
4
IMPLEMENTATION
The results of the proposed research will enable state and federal technical personnel to use
better compaction methods and control measures for using marginal soils in constructing fills.
Research results will be disseminated through presentations at national conferences, publication
in journals and/or conference proceedings, and delivery of final reports to FHWA and WSDOT.
WORK PLAN
The overall work plan would encompass (1) a comprehensive literature review of the current
technology on aeration and workability that can be transferred for compaction of marginal soils,
(2) the performance of laboratory tests on marginal soils selected from the different regions in
the state of Washington, (3) the development of control measures, and workability parameters
for marginal soils, (4) a comparison of field performance wherever possible, and (5) the
development of final reports and publications detailing recommended procedures and control
parameters for use in the field.
Task 1 – Literature review of appropriate technology
A literature review will be made to identify additional compaction control measures that can
better predict field performance of marginal soils. These will focus on the placement water
content with respect to the plastic limit (PL) and the changes in plasticity characteristics of soils
with or without the addition of lime. In the case of marginal soils containing a mixture of coarse
as well as fine particles, studies have shown their compaction characteristics to be controlled by
the coarse or fine fraction in addition to overall dry density.
The literature review will also focus on technology transfer of aeration and workability from
biotechnology and agricultural tillage research. This task will be completed with a review of the
performance of fills constructed using lime technology. The conclusions reached from this task
will be used to refine the proposed laboratory testing procedures.
Task 2 – Laboratory Tests for compaction control
This task will involve the performance of tests towards the characterization of marginal soils
from the state of Washington. These include soil classification tests and identification of coarse
or fine fraction. The specimens will be compacted using standard Proctor tests in the laboratory
and compaction curves will be developed for various conditions. Strength and permeability tests
will be performed on as compacted and soaked specimens. Their performance will be correlated
with current maximum density and optimum moisture content. In addition, the performance will
also be correlated with measures such as the placement water content with respect to the
plasticity index and coarser or finer fractions. The new additional measures will be used to
compare field performance on existing fills wherever possible.
5
Task 3 – Determination of feasibility of aeration
The biotechnology field has made significant advances in determining the efficiency of passive
and active aeration on composts (Barrington et al. 2003; Fernandes et al. 1994). It has been
found that convective airflow results from cold air coming in contact with a warm surface. The
resulting heating process lowers the density of the air and creates an air pressure drop according
to perfect gas law. Against the warm surface, the lighter warm air rises while creating a natural
convective airflow. The same process occurs within the airflow channels of a compost pile. The
air within the airflow channels of the compost material is heated becomes lighter and rises
through the air flow channels, while drawing cold air from under the pile. Barrington et al.
(2003) have proposed the use of the Grashof number (Gr) to predict airflow rate through
composite piles assuming a desired temperature profile over time. The Gr number is expressed
as (Barrington et al. 2003):


1  hA 2 g (Tw  Ta ) 
Gr  2 
(Eq. 1)

Tw  Ta
 

2


where Gr is the Grashof number, dimensionless; h is the height of the pile in m; A is a unit crosssectional area of the pile expressed as m2;  is the porosity of the compost;  is the density of the
air at ambient temperatures in kgm-3; g is the gravitational constant in m2s-1; Tw and Ta are the
compost and ambient air temperatures in K; a  is the viscosity of the ambient air in kgm-1s-1.
The Gr number can provide some means of establishing the relationship between air velocity and
temperature distribution.
This task will involve the investigation of the applicability of the above model verified for
compost for soil aeration for compaction applications. It will include the performing of some
aeration tests on model tanks with soils in the laboratory and temperature measurements. Some
studies have also used piles of compost to verify and design aeration ducts (Fernandes et al.
1994). This will also explored.
Task 4 – Determination of the workability limit of soils
The Atterberg and Proctor test data along with measured water retention will be utilized to
compare the methods for optimum workability of the soils. Following the approach by CadenaZapata et al. (2002), daily rainfall and evaporation data for the different regions will be used to
estimate the moisture distribution in the soil profile using a water balance model (Belmans et al.
1983). This information along with the workability ranges will provide the necessary
information to find the optimum days for compaction.
Task 5 – Determination of the effectiveness of lime treatment for fill applications
This task will involve detailed triaxial compression tests and 1-D compression tests on lime
treated as compacted specimens as well soaked specimens. Triaxial tests will involve undrained
as well as drained conditions at various confining pressures. The pore pressure, volume change
6
and strength measurements will be made and the results correlated with the compaction control
parameters developed in Task 2. The parameters will be used to perform stability and settlement
analysis of model fills constructed of these soils and their performance quantified.
Task 6 – Project Report and Publications
Draft and final project reports will be developed documenting the new compaction control
parameters, methods of evaluating aeration feasibility, and recommendations on workability
criteria. Conference presentations and/or journal papers will also be written to disseminate the
major findings of this research project.
STAFFING PLAN
The principal investigator for this project is Balasingam Muhunthan, Professor of Civil
Engineering. His expertise is in geotechnical engineering. He has conducted research in a
number of geotechnical areas including soil stress and strain behavior, compaction, and the
plasticity characteristics of soils. He regularly teaches courses on undergraduate course in soil
mechanics and foundation engineering and graduate courses on soil and site improvement and
numerical modeling of geomaterials. One Ph.D. student will participate in all phases of this
research project.
LEVEL OF EFFORT
Personnel
Dr. Muhunthan
Graduate student
Total
Task 1 Task 2 Task 3 Task 4 Task 5 Task 6
60
70
150
72
80
90
80
400
360
224
800
224
140
470
510
296
880
314
Total
522
2088
2610
FACILITIES AVAILABLE
The Engineering laboratories at Washington State University have well equipped laboratory
facilities. The geotechnical engineering laboratories contain standard soil testing equipment
including soil classification, compaction, consolidation, direct shear, permeability, unconfined
compression, and stress and strain controlled monotonic triaxial devices. Specialized research
equipment include two CKC cyclic triaxial testing devices capable of testing 7.1 cm and 15.2 cm
diameter samples, a SBEL (Stokoe) hybrid resonant column/torsional shear device for obtaining
dynamic soil parameters, cyclic simple shear, back pressure saturated consolidometer, and
direct-residual shear devices. A flexible wall permeability testing apparatus offers the capability
of handling toxic permeants for geo-environmental studies. All devices are equipped with
computer data acquisition systems. Equipment for extracting field samples are also available. A
humidity room is available for storage of field samples. Geotechnical faculty and graduate
students have ready access to other on-campus facilities such as the electron microscopy and
digital image analysis processing centers. The Department also owns a fully equipped drill rig
with 6 in (152 mm) hollow stem augers with a Shelby tube sampler, split spoon sampler, and
7
piston sampler. A licensed drill operator is part of the permanent staff of the department. The
university also has two geophysical trucks equipped with borehole logging equipment.
The Department maintains a well-equipped and networked microcomputer laboratory
with more than 20 microcomputers and an HP 9000 network server. Workstation laboratories
with five HP9000/730 workstations, several auxiliary x-terminals, a Silicon Graphics
workstation, and various peripherals are available for instruction and research. In addition,
access plus free CPU time on the WSU mainframe IBM 3090 are available to all students, staff,
and faculty. Excellent instrumentation shops and support staff is also available in the department
and college. The Owen Science and Engineering Library is located two blocks from the
Department. The library system at WSU maintains a completely computerized reference system
for easy access to all library acquisitions from any terminal on campus. As repository to more
than 3.5 million items, the WSU library system is an integral part of the educational resources at
WSU. Other facilities within and outside of the department are also accessible, such as the
facilities of structural engineering and wood materials laboratory, geology, geophysics, and the
Washington State Water Resources Center.
SUPPORTING DATA
The experience and capabilities of the principal investigators are summarized in the STAFFING
PLAN section of this proposal. An academic resume for the investigator is on file with WSDOT.
WORK TIME SCHEDULE
Calendar Year (months are designated by first letter)
Task 1
Task 2
Task 3
Task 4
Task 5
Task 6
2005
J F MA MJ J A S O N D J F
x x x x
x x x x x x x
x x x x x x x x x x
x x
x x
2006
MA MJ J A S O N D
x x x x x x
x x x x x x x x x
x x x x x x x x x x
x x x x x
REFERENCES
Barrington, S., Choiniere, D., Trigui, M., and Knight, W. (2003). Compost convective airflow
under passive aeration, Bioresource Technology, 86(3): 259-266.
Belmans, C., Wesseling, J. G., and Feddes, R. A. (1983). Simulation model of the water balance
of a cropped soils:SWATRE. J. Hydrology. 63:271-286.
8
Bergado, D. T., Anderson, L.R., Miura, N., and Balsubramaniam, A.S. (1996). Chapter 6, Soft
Ground Improvement in Lowland and other Environments, ASCE Press, NY.
Cadena-Zapata, M., Hoogmoed, W. B., and Perdock, U. D. (2002). Field studies to asses the
workable range of soils in the tropical zone of Veracruz, Mexico, Soil & Tillage Research 68:
83-92.
Dexter, A. R., and Bird, N. R. A. (2001). Methods for predicting the optimum and the range of
soil water contents for tillage based on the water retention curve, Soil & Tillage Research 57:
203-212.
Eades, J. L., and Grim, R.E. (1966). A quick test to determine lime requirements for lime
stabilization, Highway Research Record No. 139. Behavior Characteristics of Lime Soil
Mixtures, Highway Research Board, Washington, D.C: 61-75.
Fernandes, L., Zhan, W., Patni, N.K., and Jui, P.Y. (1994). Temperature distribution and
variation in passively aerated static compost piles, Bioresource Technology, 48 (3): 257-263
Hoogmoed, W. B., Cadena-Zapata, M., and Perdock, U. D. (2003). Laboratory assessment of
the workable range of soils in the tropical zone of Veracruz, Mexico, Soil & Tillage Research 74:
169-178.
Lerink, P. (1994). Prediction of the immediate effect of traffic on field soil qualities. Ph.D.
Thesis. Wageningen Agricultural University, Wageningen, The Netherlands, 127 pp.
Mueller, L., Schindler U., Fausey, N. R., and Lal, R. (2003). Comparison of methods for
estimating maximum soil water content for optimum workability, Soil & Tillage Research 72: 920.
Perdock, U. D., and Hendrikse, L. M. (1982). Workability test procedure for arable land. In.
Proceedings of the Ninth International Conference on ISTRO, Osijek, Yugoslavia, June 21-25:
511-519.
Pillai, V. S. and Muhunthan, B. (2004). Failure of the Teton Dam: A new theory based on state
based soil mechanics, Paper No. OSP 17, Proceedings Fifth International Conference on Case
Histories in Geotechnical Engineering, New York, NY.
Rogers, C. D. F., Glendinning, S., and Roff, T.E.F. (1997). Lime modification of clay soils for
construction expediency, Proceedings of the Institution of Civil Engineers, Geotechnical
Engineering 125( 4): 242-249.
Rogers, C. D. F., Glendinning, S.(1997). Lime requirement for stabilization, Transportation
Research Record, 1721: 9-18.
9
Rounswell, M. D. A. (1993). A review of soil workability models and their limitations in
temperate regions, Soil Use Manage, 9: 15-21.
Sherwood, P. (1993). Soil stabilization with cement and lime: State of the art review, HMSO,
London.
10
BUDGET ESTIMATE
The proposed budget is summarized on the following page. Brief justifications for each category
are provided below.
Salaries and Wages
Support for the 3-year project is provides to the Principal Investigator (total of 1.5 months) and
one Ph.D. student. All pay rates are standard and include projected increases of four percent per
year. Benefits are charged at 34% for the Principal Investigator, 1.5% for the undergraduate
student, and include tuition remission, health, and medical benefits for the graduate student.
Non-Capital Equipment
Funding is requested for a computer to be used for storing laboratory test results, data collection,
data analysis, and documentation.
Goods and Services
Goods and services will include supplies of materials, field data collection, field trips to selected
sites, laboratory testing ($23,954); publication charges ($600), and long distance charges ($400).
Travel
The following trips are anticipated for this project:
1. Field work
Indirect Costs
Indirect costs are computed at 46.8% of all project charges except the tuition for graduate
students.
Budget detail attached.
11