CONSTRUCTION OF EARTHEN FILLS

Abstract

A method for construction of earthen fills that comprises use of actual, cumulative field compaction energy generated by soil compactors as a function of rolling resistance with soil densification, to determine the asymptotic energy-density approach range.

Description

RELATED APPLICATIONS

This application is a continuation in part of co-pending application Ser. No. 12/930,391 filed Jan. 4, 2011, which is a continuation in part of co-pending application Ser. No. 11/522,701 filed Sep. 18, 2006, which is a continuation in part of application Ser. No. 10/924,132 filed Aug. 23, 2004, now U.S. Pat. No. 7,110,884; which is a continuation of Ser. No. 10/244,998 filed Sep. 16, 2002, now U.S. Pat. No. 6,859,732 which is a section 371 national phase application from PCT International application Number PCT/US01/15638 Filed 15 May 2001.

TECHNICAL FIELD

This invention encompasses new methods for and in earthen fill engineering and construction and includes application to all soils, treated and amended soils, and earthen base and sub-base materials. The prior related applications listed above were focused on the engineering aspects of the invention—in this application we turn to the construction applications of the invention. More specifically this invention involves new methods to use actual, cumulative field compaction energy generated by soil compactors as a function of rolling resistance with soil densification, to determine the asymptotic energy-density approach range and associated compaction performance, and tie or correlate the asymptotic compaction performance to compacted engineering properties, moisture-density relations and the end point of lift compaction.

BACKGROUND OF THE INVENTION

In current engineering practice, 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 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 the field compaction energies of two predominant, towed compactors (or rollers) used in the early 1930's. These fixed compaction energy levels were based on drawbar pull values measured on the towed compactors, and considered to be somewhat representative of field compaction energies. Subsequently, it was found that many structural fills constructed by using the standard proctor energy were failing over time. These circumstances led to the development of a larger towed roller which led to the development of the Modified Proctor compaction test (ASTM D 1557) by R. R. Proctor to simulate the compaction energy of the larger roller. 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 field and laboratory compaction (moisture-density) curves that would be more comparable. The present inventors have published a very basic approach to improved procedures: 1.) “Practice Improvements for the Design and Construction of Earth Fills”, Proceedings of the Eighth Annual Conference on Contaminated Soils”, University of Massechusetts at Amherst, 1994; and Geoenvironment 2000 Conference, New Orleans, La., 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, Tex. There has not previously been available in the art practicable methods to derive actual cumulative field compaction energies unique to each site construction lift based on soil/compactor/lift thickness/moisture/soil amendment combinations, actual compaction performance including moisture-density relations and engineering properties based on the same unique 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 in laboratory tests or utilized in engineering methods, rather than the fixed energies of the standard test methods described above. 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 moisture states, lift thickness,' and soil amendments.

SUMMARY OF THE INVENTION

The invention provides a method for construction of earthen fills that comprises use of actual, cumulative field compaction energy generated by soil compactors as a function of rolling resistance with soil densification, to determine the asymptotic energy-density approach range and associated asymptotic compaction performance. Another preferred embodiment correlates the asymptotic compaction performance to one or more values selected from the group consisting of moisture-density relations, optimum moisture-density, percentages of maximum dry-density compaction, the compactor make and model, soil properties, compactor performance, compactor-soil interface, and the end point of lift compaction. In another preferred embodiment any drive train step or component of compactor performance resulting in rimpull drive performance or drive power, including compactor horsepower is isolated or measured to establish change in rimpull performance with rolling resistance. For example rimpull rolling resistance is measured by rimpull power performance which is the drive power of the compactor at the wheel where the compactor is mobilized. For a particular lift, compaction is deemed complete when the change in rimpull rolling resistance falls below a value considered insignificant. One measure of insignificant change where compaction is deemed complete is when the measured change in rolling resistance is less than the measured error for determining rolling resistance. In an especially preferred embodiment a drive train step or component of engine power performance is tracked or measured and transmitted to a computation means to track variation of power performance for each pass over a given area to be compacted, and the compactor operator receives an instruction when the desired magnitude of the change in engine power is achieved. The method may include a real time computation of change in rolling resistance used to identify the asymptotic energy-density approach range. The method may also include providing means for drive train power or energy data as a measure of rimpull energy to be transmitted to a receiving station and the transmitted data is used to compute the asymptotic energy density approach range. Alternatively the invention can be defined as a method for construction of earthen fills that comprises determining field specific rolling resistance at the asymptotic energy-density approach and associated asymptotic compaction performance and correlating the determined rolling resistance to engineering properties of the compacted lift. In a preferred embodiment the engineering properties of the compacted lift is the end point for compaction. An alternative method of the invention provides a method for compaction of earthen fills that comprises determining field measured, site specific rimpull rolling resistance changes until the magnitude of change in rimpull rolling resistance indicates the asymptotic energy-density approach range has been reached for the area being compacted. A preferred method uses changes in rimpull rolling resistance measured by changes in compactor power performance.

The invention defined in this application provides for a different method for determining compaction energy and associated moisture-density/engineering property relations in the asymptotic energy-density approach range with compactor passes for any given combination of soil type, soil properties, compactor, moisture content, lift thickness, and soil amendment, based on energy from the compactors power source and drive train—including a vibratory or impact energy component that may be added in the case of dynamic or vibratory compactors, and determining cumulative, field/lift-specific compaction energy as a function of rolling resistance. The invention also includes relating soil lift compaction performance, moisture-density relations and compacted engineering properties, in relation to the properties of the lift soil and the soil/compactor interface. The method includes tracking energy distribution from the compactor and into the soil. The method provides asymptotic compaction performance in the asymptotic energy-density approach range correlated to any stage, measure or component of energy distribution and/or transmission from the compactors power source to the cumulative, field/lift-specific compaction energy in construction. The method provides measuring or monitoring of cumulative rolling resistance, compaction energy, compactive energy loss, compaction performance and engineering properties of the compacted lift at asymptotic compaction performance, under practical and controlled construction conditions. The method includes determining or monitoring the unit cumulative compactive energy per unit volume at asymptotic compaction performance in the asymptotic energy-density approach range for each compactor pass by using the cumulative average rolling resistance. The invention provides a method for establishing engineering quality control and quality assurance in construction and determining actual, cumulative field compaction energy and associated engineering property relationships for a given soil. The improvement in the method includes for a selected compactor, measuring, monitoring or determining the energy transferred to the soil by measuring or monitoring rolling resistance or change in rolling resistance as a function of rimpull or drive energy performance, plotting the variation of rolling resistance for a plurality of roller passes, determining the site-specific, asymptotic energy-density approach range, determining the cumulative average rolling resistance at asymptotic compaction performance within said asymptotic energy-density approach range, and determining when full lift compaction performance, the end point of lift compaction, or design energy levels are met or exceeded. Alternative measurements and relations include correlations with horsepower or any stage, measure or component of the source compactor energy or power train. The method also includes additional forces that may be applied to the soil by vibratory or other dynamic forces from compactors. Optionally the invention may comprise the steps of 1) tracking energy distribution and isolating compaction energy transfer, 2) determining cumulative site lift-specific compaction energy and corresponding engineering properties or monitoring site-lift specific compaction energy variation and corresponding engineering properties for a soil type, a compactor type, and at least one additional variable selected from the group consisting of moisture content, lift thickness, and soil amendments. preferably measuring or monitoring compaction energy or rolling resistance variation for a plurality of roller passes, measuring or monitoring compaction energy or rolling resistance variation with dry density variation for a plurality of roller passes, and more preferably measuring compaction energy changes including dynamic or vibratory energy in variation with dry density for a plurality of roller passes. The method may optionally measure at least one additional variable selected from the group consisting of lift thicknesses, soil moisture contents, soil types, and soil amendment, The method may include field measurements that are used to establish specific and corresponding parabolic curves of compaction energy including dynamic or vibratory energy components versus soil moisture-density relations and optionally further comprises determining the unit cumulative compaction energy per unit volume within the asymptotic energy-density approach range based on moisture-density-energy relationships. The method may include determining the asymptotic energy-density approach range based on two or more of the site-specific results of the following field condition combinations: soil type, soil properties, compactor type, lift thickness, moisture content, and soil amendment; and correlating the data by plotting or equivalent computational means to provide the maximum compaction conditions. All methods may be computerized.

DETAILED DESCRIPTION OF THE INVENTION

Definitions

“ASTM” means American Society for Testing Materials.
“AASHTO” means American Association of State Highway and Transportation Officials
“Asymptotic Energy-Density Approach” means a segment or range of roller passes wherein the incremental change in rolling resistance and corresponding soil densification begins to be insignificant with successive roller passes, thus representing full lift compaction, full lift compaction performance, the end point of lift compaction, or the “design energy level” of lift compaction. Full lift compaction performance is the compacted lift properties at full lift compaction including moisture-density relations and all physical/engineering properties. The term “Asymptotic Compaction Performance” is interchangeable with “Asymptotic Energy-Density Approach.”
“Asymptotic Compaction Performance” means lift compaction performance in the “Asymptotic Energy-Density Approach” range.
“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.
“Compaction Energy” means the energy component that is transferred by a compactor or compaction roller into the ground or soil lift over which it is traveling, and represents the energy that causes soil densification. The term can also be defined as the compaction energy required to overcome rolling resistance. The term “compactive energy” is interchangeable with “compaction energy.”
“Cumulative Compaction Energy” means the cumulation of Compaction Energy with each compactor pass.
“Cumulative Average Rolling Resistance” means the cumulative Rolling Resistance of a compactor rolling or driving over a soil lift that cumulates with each consecutive compactor pass until completion.
“Design Energy Level” means a cumulative compaction energy level representing, equating to or equaling the actual cumulative field energies at asymptotic compaction performance produced by compactor-soil-moisture-lift thickness-soil amendment combinations, at a select point within the asymptotic energy-density approach in construction and at a select percent-density sector on the site lift-specific M-D curve. Design energy level may be used in a controlled environment, in field or lab testing, and in engineering uses including laboratory compaction testing.
“Rolling resistance” is defined as the resistance to the compactor rolling or driving over the soil lift being compacted. The term can also be defined as the rimpull performance, energy or power of the compactor required to overcome resistance to compactor rolling. The term can also be defined as the fraction of rimpull energy or compactor drive energy needed to overcome energy loss into the earthen lift being compacted.
“Soil Type” is defined as an earthen soil material defined or characterized by its physical properties, index properties or engineering properties, and/or classification in engineering classification systems (i.e., Unified Soil Classification System, AASHTO, etc.). The definition also includes soils mixed with amendments, reagents, additives or other materials which are designed to alter or improve its physical properties, index properties or engineering properties for improved or altered compaction efficiencies or compacted properties.

General Description of the Invention

The inventors recognized 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 or drive energy. The rimpull energy of a given roller wheel is considered to be a more suitable parameter for determination of field compaction energy than the compactor's drawbar pull parameter as used by R. R. Proctor in the development of standard methods.

The invention encompasses new and different methods for measuring, monitoring and/or determining actual, cumulative field compaction energy and compaction performance based on rolling resistance measurements. The invention includes a method for construction based on measuring, monitoring and/or determining actual, cumulative field compaction energy and associated engineering property relationships for a given soil type, the improvement that comprises for a selected compactor, determining the energy transferred to the soil by measuring field combination-specific rolling resistance as a function of rimpull energy or drive energy performance, measuring, monitoring and/or plotting the variation of rolling resistance, compaction energy or soil densification or both, for a given soil moisture content for a plurality of roller passes, determining the combination-specific, asymptotic energy-density approach range, and thus determining when the earthwork design requirement is met or exceeded. The invention includes the correlation of engineering properties of compacted soil lifts to the actual cumulative compaction energy levels and lift-specific combinations in construction, as opposed to fixed energy levels and standard practices.

EXAMPLE 1

At a construction site the rolling resistance of a wheel/ground system suitable for earthen fill construction is measured for a site-specific moisture content, dry density, soil amendments, on successive roller passes and the changes in rolling resistance are monitored. Earthwork compactors are used and each compactor's performance parameters and specifications are recorded. Soil compaction is continued until changes in field compaction measurements are clearly in an asymptotic state and the novel asymptotic compaction performance, a design energy level, or specified target compacted density property or set of properties is achieved.

EXAMPLE 2

The invention includes a method for computation of the novel cumulative average rolling resistance or asymptotic compaction performance for each construction lift combination from the novel asymptotic energy-density approach formed by compaction performance measurement or quantification with each compactor pass to and within the novel asymptotic energy-density approach range. This is accomplished as follows:

For each lift-specific pass, compactor rolling resistance and soil densification may be measured by cumulative rimpull energy performance, or drive train energy or power, compactor energy distribution or power transmission, or performance engine horsepower or other means for measuring resulting rimpull energy and compaction energy transfer to the soil; and the rolling resistance variance with roller passes is computed. The cumulative averages are made with values taken from the first compactor pass up to the select pass at or within the novel asymptotic energy-density approach. The cumulative averages representing values at the novel asymptotic energy approach can then be used for computing unit cumulative compaction energy per unit lift volume. The invention provides a novel tool that reduces problems in meeting design requirements and specifications and provides novel quality control during construction.

Claims

1. A method for construction of earthen fills that comprises use of actual, cumulative field compaction energy generated by soil compactors as a function of rolling resistance with soil densification, to determine an asymptotic energy-density approach range and associated asymptotic compaction performance.

2. The method of claim 1 that ties the asymptotic compaction performance to any value selected from the group consisting of moisture-density relations, optimum moisture-density, percentages of maximum dry-density compaction, soil properties, compacted soil properties, compactor performance, compactor-soil interface, and end point of lift compaction.

3. The method of claim 1 wherein any drive train step is measured to establish change in rimpull rolling resistance.

4. The method of claim 1 wherein rimpull rolling resistance is measured by compactor power performance.

5. The method of claim 1 wherein compaction is deemed complete when the change in rolling resistance falls below a value considered insignificant.

6. The method of claim 5 wherein compaction is deemed complete when the measured change in rolling resistance is less than the measured error for determining rolling resistance.

7. The method of claim 1 where change in a component of engine power is measured and transmitted to a computation means to track variation of engine power for each pass over a given area to be compacted, and the compactor operator receives an instruction when the desired magnitude of the change in engine power is achieved.

8. The method of claim 1 wherein a real time computation of change in rimpull rolling resistance is used to identify an asymptotic energy-density approach range.

9. The method of claim 1 wherein drive power data from the compactor is transmitted to a receiving station and the transmitted drive power data is used to compute an asymptotic energy density approach range.

10. A method for construction of earthen fills that comprises determining field specific rolling resistance at the asymptotic energy-density approach and correlating the determined rolling resistance to engineering properties of the compacted lift.

11. The method of claim 10 that correlates the asymptotic compaction performance to one or more values selected from the group consisting of moisture-density relations, optimum moisture-density, percentages of maximum dry-density compaction, soil properties, compactor performance, compactor-soil interface, and the end point of lift compaction.

12. The method of claim 10 wherein compactor engine horsepower is measured to establish change in rolling resistance.

13. The method of claim 10 wherein rimpull rolling resistance is measured by compactor power performance.

14. The method of claim 10 wherein compaction is deemed complete when the change in rolling resistance falls below a value considered insignificant.

15. The method of claim 14 wherein compaction is deemed complete when the measured change in rolling resistance is less than the measured error for determining rolling resistance.

16. The method of claim 10 where change in engine power is measured and transmitted to a computation means to track variation of engine power for each pass over a given area to be compacted, and the compactor operator receives an instruction when the desired magnitude of the change in engine power is achieved.

17. The method of claim 10 wherein a real time computation of change in rolling resistance is used to identify the asymptotic energy-density approach range.

18. The method of claim 10 wherein engine drive train power data from the compactor is transmitted to a receiving station and the transmitted engine drive power data is used to compute the asymptotic energy density approach range.

19. A method for compaction of earthen fills that comprises determining field measured, site specific rimpull rolling resistance changes until the magnitude of change in rimpull rolling resistance indicates the asymptotic energy-density approach range has been reached for the area being compacted.

20. The method of claim 19 wherein changes in rimpull rolling resistance are measured by changes in compactor power performance.