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NCHRP 21-09 [Completed]

Intelligent Soil Compaction Systems

  Project Data
Funds: $599,879
Research Agency: Colorado School of Mines
Principal Investigator: Michael A. Mooney, Ph.D., P.E.
Effective Date: 8/30/2006
Completion Date: 2/28/2010
Comments: NCHRP Report 676 Intelligent Soil Compaction Systems

BACKGROUND

Compaction of embankment, subgrade, and base materials is a significant portion of state highway construction budgets and is critical to the performance of highway pavements. Heterogeneity of earth materials, variability in equipment and operators, and difficulty in maintaining uniform lift thickness and prescribed moisture content combine to make desired earthwork compaction difficult to achieve. Current quality-control and quality-assurance testing devices--such as the nuclear gage, the dynamic cone penetrometer, the stiffness gauge, and the lightweight falling weight deflectometer--are typically used to assess less than one percent of the actual compacted area. In addition each of these testing devices measures values unique to the device.

Intelligent soil compaction has the potential to improve infrastructure performance, reduce costs, reduce construction duration, and improve safety. Intelligent soil compaction involves: (a) continuous assessment of mechanistic soil properties (e.g., stiffness, modulus) through compaction-roller vibration monitoring; (b) continuous modification of roller vibration amplitude and frequency, and (c) an integrated global positioning system to provide a complete GIS-based record of the earthwork site.

Research findings in Europe and in the United States have shown that soil stiffness and modulus can be assessed through vibration of the compaction roller drum and that continuous monitoring, feedback, and automatic adjustment of the compaction equipment can significantly improve the quality of the compaction process. Standard specifications for the application of intelligent compaction systems in the United States are needed. Such specifications should build on existing specifications and experience gained in Germany, Switzerland, Finland, Sweden, Japan, and other countries.


OBJECTIVES

The objectives of this research are to determine the reliability of intelligent compaction systems and to develop recommended construction specifications for the application of intelligent compaction systems in soils and aggregate base materials. (See Special Note B.)


Accomplishment of the project objective will require at least the following tasks.

TASKS

Task descriptions are intended to provide a framework for conducting the research. The NCHRP is seeking the insights of proposers on how best to achieve the research objectives. Proposers are expected to describe research plans that can realistically be accomplished within the constraints of available funds and contract time. Proposals must present the proposers' current thinking in sufficient detail to demonstrate their understanding of the issues and the soundness of their approach to meeting the research objectives.

PHASE I (1.) Conduct a review of domestic and international literature and determine the current state of practice of intelligent compaction of soils and aggregate base materials. Identify and translate foreign language specifications and literature deemed to be applicable and especially useful in achieving the project objective. (2.) Query compaction equipment manufacturers and collect pertinent intelligent compaction roller data to determine equipment capabilities and the current state of practice. The data should include modulus, acceleration, amplitude, frequency, speed, contact area, compactive effort, efficiency, global position, and displacement. (3.) Coordinate with state departments of transportation (DOTs) and construction contractors and identify active construction projects for the purpose of scheduling field operations for the collection and comparison of intelligent and traditional compaction data. Coordinate with at least five state DOTs and give special attention to selecting construction projects that provide a wide variety of soil types. (4.) Visit one of the construction projects identified in Task 3. Formulate a data collection plan and collect roller data, instrumentation data, and in-situ testing data. The roller data should be continuously recorded and include modulus, acceleration, amplitude, frequency, speed, contact area, compactive effort, efficiency, global position, and displacement. Instrumentation data should include measurements from buried in ground sensors such as strain gauges, accelerometers, and bender elements for verifying the reliability of the intelligent compaction roller data. In-situ tests should include plate load, dynamic cone penetrometer, light weight deflectometer, nuclear density gage, stiffness gage, falling weight deflectometer, sand-cone, and other appropriate tests. In-situ data should include moisture content. (5.) Analyze the Task 4 data and validate the roller data with the instrumentation data. Correlate the roller data with the in-situ data. Determine the importance of moisture, layer depth, and the foundation layer on the accuracy of intelligent compaction systems. (6.) Based on the Task 5 analysis, provide acceptability criteria for establishing target values for modulus. Develop preliminary specifications for the intelligent compaction of soils and aggregate base materials. (7.) Submit an interim report documenting the work completed in Tasks 1 through 6. The interim report should include the preliminary specifications for review by the NCHRP panel. Include an updated, detailed work plan for completing Phase II of the research as a separate appendix to the interim report. Meet with the NCHRP panel to discuss the interim report and Phase II work plan. Work on Phase II will not begin without approval of the NCHRP panel.

PHASE II (8.) For the construction projects identified in Task 3 and not yet visited, formulate a data collection plan and collect roller, instrumentation, and in-situ testing data. The roller data should be collected from a minimum of three different intelligent compaction roller manufacturers. The roller data should be continuously recorded and include modulus, acceleration, amplitude, frequency, speed, contact area, compactive effort, efficiency, global position, and displacement. Instrumentation data should include measurements from buried in ground sensors such as strain gauges, accelerometers, and bender elements for verifying the reliability of the intelligent compaction roller data. In-situ testing devices should include, plate load tests, dynamic cone penetrometer, light weight deflectometer, nuclear density gage, stiffness gage, falling weight deflectometer, sand-cone test, and other appropriate tests. In-situ data should include moisture content. (9.) Analyze all the collected data and validate the roller data with the instrumentation data. Correlate the roller data with the in-situ data. Determine the importance of moisture, layer depth, and the foundation layer on the accuracy of intelligent compaction systems. Based on the analysis of the acquired data, provide target values for the modulus of different soil types. (10.) Develop recommended construction specifications for the application of intelligent compaction systems in soils and aggregate base materials. (11.) Submit a final report documenting the entire research effort. The final report should address the reliability and effectiveness of intelligent compaction technology in different soil types. The Task 10 construction specifications should be included as a separate appendix.

SPECIAL NOTES

 

A. No more than 10 months should be spent in the completion of Phase I. (The 10 months includes 2 months for review and approval of the interim report and the Phase II work plan).

B. For the purposes of this project, intelligent compaction is defined as continuous calculation of modulus with a real-time feedback mechanism and automatic adjustment. Intelligent compaction involves the use of rollers that are equipped with a control system that can automatically adjust compactive effort in response to a materials modulus during the compaction process. The roller must also be equipped with a documentation system that allows continuous recordation such as the number of roller passes and roller-generated material modulus. The output must (1) enhance the ability of the roller operator and/or project inspection personnel to make real-time corrections in the compaction process; (2) be available for inspector review on demand; (3) allow for a plan-view, color-coded plot of roller stiffness and/or roller pass number measurements throughout a designated section of roadway.

C. The state Departments of Transportation for Minnesota, Florida, North Carolina, Colorado, and Maryland have volunteered to assist in the identification of active construction projects for the on-site data collection and in-situ testing efforts. Points of contact for each state are available from NCHRP after contract award.

D. The research team should include technical expertise to assist in the incorporation of international state of the art technology and translation of foreign language specifications and literature.

E. The Intelligent Compaction Specification developed under this project should:
    1. Address real time documentation. The real time documentation for acceptance should be a simple graphical and text presentation recording the modulus value in relation to a specified value. The presentation should be in 10 cm by one drum width blocks. Position identification should be recorded at both ends of the roller using GPS technology.
    2. Be generic. The specification should be generic with respect to the type of compaction equipment (i.e., vibratory, static, smooth, sheep's foot, and pneumatic rollers).
    3. Address minimum equipment size and required compactive effort.
    4. Discuss the calibration of intelligent compaction equipment.
    5. Include Quality Control and Quality Assurance requirements.

F. NCHRP Project 10-65, Nondestructive Testing Technology for Quality Control and Acceptance of Flexible Pavement Construction, is currently underway, but scheduled to be completed before the start of this research. The research team should use the test protocols recommended in NCHRP Project 10-65 as much as possible in the data collection effort for this project. An interim report for Project 10-65 is available from NCHRP upon request by emailing Ms. Megan Chamberlain at mchamberlain@nas.edu.


G. Proposals should include a task-by-task breakdown of labor hours for each staff member as shown in Figure 5 in the brochure, "Information and Instructions for Preparing Proposals" (http://trb.org/nchrp under "Current RFPs [Requests for Proposals]"). Proposals also should include a breakdown of all costs (e.g., wages, indirect costs, travel, materials, and total) for each task.

H. NCHRP projects are intended to produce results that will be applied in practice, and proposals and the project final report must contain implementation plans for moving the results of the research into practice. Item 4(c), "Anticipated Research Results," in each proposal must include an Implementation Plan that describes activities to promote application of the product of this research. It is expected that the implementation plan will evolve during the project; however, proposals must describe, as a minimum, the following: (a) the "product" expected from the research, (b) the audience or "market" for this product, (c) a realistic assessment of impediments to successful implementation, (d) the institutions and individuals who might take leadership in applying the research product, (e) the activities necessary for successful implementation, and (f) the criteria for judging the progress and consequences of implementation.

I. Item 5 in the proposal, "Qualifications of the Research Team," must include a section labeled "Disclosure." Information relevant to the NCHRP's need to ensure objectivity and to be aware of possible sources of significant financial or organizational conflict of interest in conducting the research must be presented in this section of the proposal. For example, under certain conditions, ownership of the proposing agency, other organizational relationships, or proprietary rights and interests could be perceived as jeopardizing an objective approach to the research effort, and proposers are asked to disclose any such circumstances and to explain how they will be accounted for in this study. If there are no issues related to objectivity, this should be stated.

Funds Available: $600,000

Contract Time: 30 months (includes 2 months for NCHRP review and approval of the interim report, and 3 months for NCHRP review and for contractor revision of the final report)

Staff Responsibility: Mr. David Reynaud, 202/334-1695 (E-mail: dreynaud@nas.edu)

Authorization to Begin Work: June 2006--estimated

Status: This research has been published as NCHRP Report 676: Intelligent Soil Compaction Systems

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