Institute for Transportation

About the research

The Iowa Department of Transportation Roller-Integrated Compaction Monitoring (RICM) Research and Implementation project was initiated in summer 2009. The project was conducted in two phases:

Phase I:  Three field demonstration projects were conducted in Iowa as part of the Phase I to evaluate three different RICM measurement technologies: (1) machine drive power (MDP) measurement technology on Caterpillar CP56 padfoot roller, (2) continuous compaction value (CCV) technology on Sakai SW880 dual vibratory smooth drum asphalt roller, and (3) compaction meter value (CMV) technology on Volvo SD116DX smooth drum vibratory roller. The main objectives of the Phase I include:

1. evaluating the effectiveness of the RICM measurement values (IC-MVs) in assessing the compaction quality of cohesive subgrade materials, granular base/subbase materials, and HMA materials,
2. developing project specific correlations between IC-MVs and various conventionally used in-situ point measurements in earthwork quality control (QC) and quality assurance (QA) practice and HMA construction,
3. evaluating the advantages of using the RICM technology for production compaction operations,
4. obtaining data to evaluate future RICM specifications, and
5. developing content for future educational and training materials for Iowa DOT and contractor personnel for effective implementation of the technology in to earthwork and HMA construction practice.

Phase II: As part of the Phase II of this project, special provisions (SPs) were developed that required RICM technologies on three hot mix asphalt (HMA) overlay pilot projects in Iowa. The SP on US30 Harrison County project required RICM roller coverage including temperature, pass count, and compaction measurements on one break down roller. The SP on US20 Ida County project required RICM roller coverage including temperature and pass count on one break down roller. The SP on IA9 Kossuth County project required roller pass count coverage for all compaction equipment. In situ testing was conducted on each project by the Iowa State University research team beyond the requirements of the project specifications to analyze asphalt density, RICM values, and asphalt surface temperature changes with pass count and time. Correlations between RICM values and asphalt density/percent compaction and falling weight deflectometer modulus values are developed. Pass count information was analyzed using geostatistical analysis to evaluate spatial uniformity in pass coverage.

About the research

Constructing long-lasting roadway infrastructure requires careful process control. It is well known in industry that an in situ manufacturing process governed solely by human operators introduces inefficiencies, variable quality results, and site safety risks. Autonomous and robotic controls of the road building process have great potential to reduce these problems. Unfortunately, roadway construction has virtually no theory established for process control. What is called for is an academic-industry partnership to study and analyze the impacts of productivity, quality, and safety for roadway construction that can quantify and prioritize the formulation of a process control theory to address this need.This project funds three important efforts:

1. A nationwide stakeholder conference to identify gaps and opportunities for autonomous and robotics roadway construction technologies
2. Selected field studies focused on earthwork and excavation technologies
3. A technology transfer program to improve understanding and beneficial implementation

The results of this study are directly related to the State of Good Repair, a key program under MAP-21, and the Midwest Transportation Center (MTC) focus area of project construction, because autonomous and robotic systems impact productivity, quality, and safety of roadway infrastructure.

Funding Sources:
Caterpillar ($60,000.00)
Iowa State University ($15,000.00)
USDOT/OST-R ($75,000.00)
Total: $150,000.00

Contract Number: DTRT13-G-UTC37

About the research

Caterpillar has developed proprietary software technology – Compaction Forecasting Expert Database (CFED) – to predict compaction performance for site specific applications. This report (Phase IV) presents laboratory test results of five soil samples collected from field project sites in Utah, Texas, North Dakota, and Iowa and the corresponding CFED analysis. Recommendations for presentation of in-situ test results and soil mineralogy information in CFED, and a database of volumetric factors for earthwork quantity estimation from literature review are also reported herein.

Shrinkage and swell factors of a total of 154 soils were collected from the literature and grouped into seven material groups: (1) rocks, (2) gravels, (2) sands, (4) silts, (5) clays, (6) minerals, and (7) other soils. The swell factors statistics showed a narrow range for gravel soils (minimum value – maximum value = 0.11) compared to other soils (with minimum value – maximum value = 0.22 to 0.44). The shrinkage factors varied more than the swell factors as the shrinkage factor values are likely influenced by the percent compaction achieved in the field. Future research is warranted emphasizing field studies that focus on developing a database of shrinkage/swell factors for various material types and relative compaction. The database should link shrinkage and swell factors to soil classification, gradation, Atterberg limits (for non-granular soils) parameters, equipment, and laboratory compaction measurements.

Step-by-step procedures are also described to estimate moisture-conditioning (i.e., wetting or drying) of soil for compaction using bank and compacted soil three phase diagram and weight-volume relationships. These calculations should add value to the contractor’s moisture control and conditioning operations.

About the research

The NCHRP Project 21-09, “Intelligent Soil Compaction Systems,” was undertaken to investigate intelligent soil compaction (IC) systems and to develop generic specifications for the application of IC in quality assurance (QA) of soil and aggregate base material compaction. The term intelligent soil compaction systems was defined to include (1) continuous assessment of mechanistic soil properties (e.g., stiffness, modulus) through roller vibration monitoring; (2) automatic feedback control of vibration amplitude and frequency; and (3) an integrated global positioning system to provide a complete geographic information system-based record of the earthwork site. An equally important term is roller-integrated continuous compaction control—defined by IC components (1) and (3).

Roller-integrated continuous compaction control (CCC) technology was initiated in Europe in the 1970s and has been used in European practice for nearly 20 years. The first European specification for roller integrated CCC was developed in Austria in 1990. Today, four European countries have soil compaction QA specifications using roller-integrated CCC (Austria, Germany, Sweden, and Switzerland) and U.S. states are beginning to implement pilot specifications (e.g., Minnesota). In European specifications the use of automatic feedback control IC rollers is permitted during compaction but not during QA because the roller measurement values (MVs) can be strongly influenced by varying amplitude and frequency. The dependence of roller MVs on frequency and amplitude in particular was verified in this study and further determined to be quite complex and difficult to predict. Accordingly, the recommended specifications developed here allow IC during compaction but do not permit the use of automatic feedback control IC during roller-based QA.

The following are the key items covered in this project:

• Recommended Specifications for Roller Integrated CCC in Earthwork QA
• Fundamentals of Roller Measurement Systems
• Relationship Between Roller-Measured Stiffness and In Situ Stress-Strain-Modulus Behavior
• Evaluation of Automatic Feedback Control-Based Intelligent Compaction
• Correlation of Roller Measurement Values to Spot-Test Measurements
• Case Study Implementations of Recommended Specifications

About the research

This study documents relationships between intelligent compaction measurement values (IC-MVs) and various insitu point measurement techniques for monitoring compaction of non-granular and granular materials. Factors affecting correlations are discussed (e.g., soil type, moisture contents, stress level, etc.). Measurements from earth pressure cells document the relationship between in-ground stresses for rollers and various in-situ test methods. Comparisons were made between test roller rut depth measurements and IC-MVs and various point measurements as a quality assurance (QA) check for the subgrade pavement foundation layer. It was concluded that IC-MVs and in-situ point measurements can serve as reliable alternatives to test rolling. Site specific target values were calculated for IC-MVs, dynamic cone penetrometer (DCP), light weight deflectometer, (LWD), and shear strength. Measurement error and protocols for field testing were evaluated for LWDs. Laboratory compacted samples were used to assess an approach for determining LWD field target values.

Future research is recommended to evaluate this approach for materials on a state-wide basis. Results from field studies were used to develop four IC specification options. Three specifications do not require on-site roller calibration. One specification option requires on-site calibration of IC-MVs and in-situ point measurements. This specification option has the advantages of quantifying risk, establishing a framework for a performance specification, providing information for incentive-based pay, and better linking as-built quality to long-term performance. An IC training/certification program, new IC field data analysis tools, and additional pilot projects will assist with greater implementation of these technologies.

About the research

CS-563 and CS-683 smooth drum vibratory machines and a CP-563 padfoot machine were used to construct controlled soil test beds to evaluate the repeatability of CMV and MDP roller-integrated measurements, compare integrated CMV and MDP measurements, and evaluate and document CMV and MDP for a given machine as it relates to measurement influence depth.

The repeatability study involved conducting about 15 passes of each machine over relatively uniform and hard ground at two speeds and two amplitudes.  A statistically sound approach to evaluating and presenting the raw data to the end user (e.g. compute average values for selected interval, etc.) was developed as part of this study.  Results show that there is a machine specific and unique relationship between CMV and RMV and that speed, amplitude, travel direction, and drum-ground behavior mode can be statistically significant parameters in repeatability analysis.

Test beds constructed to evaluate two different subsurface conditions – hard and soft – demonstrated that roller and in-situ compaction measurements are influenced by the stiffness and heterogeneity of the supporting layer conditions.  Further, although the compaction layer properties are relatively uniform, the roller measurements tend to capture the variability of the underlying layers, which is important for proper results during field calibration.  Post-construction tests of the multi-lift test beds clearly demonstrated that compaction layers stiffness increases due to deep densification of underlying layers during compaction.

About the research

In this research, the Compaction Forecasting Expert Database (CFED) analysis tool developed by Caterpillar Inc. was analyzed and compared to traditional approaches for predicting a family of laboratory soil compaction curves for a given soil. Classification, laboratory compaction, and field compaction data for 42 soils collected from 7 states (Iowa, Illinois, Minnesota, North Carolina, Colorado, Maryland, and Florida) and China were input into CFED to evaluate its performance. Five other methods for prediction of all or part of the laboratory compaction curve were determined from a literature review. The performance of CFED was determined both absolutely and relative to these five prediction techniques. Soil samples were compacted in the laboratory using impact compaction at standard, modified, and intermediate compaction energies. Lab compaction curves were interpreted by hand and by the six other methods of prediction (i.e., the CFED and the five methods determined by the literature review). In total, 763 compaction tests were completed as part of this study. The deviation of predicted values to interpreted values was analyzed to compare the performance of CFED to the other five prediction models found in the literature. Additionally, this research linked relationships between laboratory compaction energy and machine pass. Field compaction data were available for some soils input into CFED. These field data included density, dynamic cone penetration index (DCPI), Clegg impact value (CIV), light-weight deflectometer (LWD), and plate load testing (PLT) data versus machine pass for various machine configurations.

About the research

Caterpillar Inc. has developed proprietary technology to predict compaction performance for site-specific applications. The output of the technology is the prediction of (a) the capability of compaction machines to meet compaction specifications, (b) predicted productivity for specific machines, (c) sensitivity of compaction and productivity to soil moisture, and (d) recommended soil lift thickness with anticipated number of machine passes to meet compaction specifications. The technology is site and soil specific. It requires standard and specialized testing of the actual earthworks construction soils. Results from the soil testing are then input to unique software that converts the input data to the four predictions for capability, productivity, sensitivity, and process. This output has been defined as the recipe for successful cost effective earthworks construction. The forecasting technology is developed and has been shown successful in limited trial applications. General application of the technology needs a broader database of soils and machine performance results and coincidental upgrades to the prediction algorithms with an expanded database.

About the research

The lack of control over the uniformity of moisture content is a leading cause of problems experienced by industry in effective compaction control of earth fill materials. Current measurement techniques for determination of moisture content generally involve spot tests that can be time consuming, unreliable and do not provide adequate coverage. Recent advances in nondestructive evaluation technologies, especially near infrared reflectance spectroscopy (NIRS), and data analysis techniques (e.g., multivariate analysis and Bayesian statistics) show significant promise in obtaining necessary information that could significantly advance field moisture control for earthwork construction by increasing the coverage area in lieu of spot tests, providing measurements that are accurate, and speeding up the inspection process and providing real-time results in computer format. Research is needed to identify suitable technologies, evaluate them for robustness and accuracy in a wide range of soil types, develop data analysis and output algorithms and create onboard machine equipment, and launch the technologies.

About the research

A field study comprised of experimental testing and statistical analyses was conducted to evaluate the Caterpillar machine drive power (MDP) and Geodynamik compaction meter value (CMV) compaction monitoring technologies applied to Caterpillar rollers. The study was comprised of three projects, all of which were conducted at the Caterpillar Edwards Demonstration facility near Peoria, IL.

The first project investigated the feasibility of using MDP applied to a Caterpillar self-propelled non-vibratory 825G roller. A test strip was constructed, compacted using the prototype 825G roller, and tested with in situ test devices.

The second project also consisted of experimental testing on one-dimensional test strips. This project, however, used five cohesionless base materials, which were compacted using a CS-533E vibratory smooth drum roller with both MDP and CMV measurement capabilities. The independent roller measurements were compared and described in terms of soil engineering properties.

The final project was conducted with only one cohesionless material. Four test strips (three uniform strips at different moisture contents and one with variable lift thickness) were constructed and tested to develop relationships between roller measurements and soil engineering properties.

Using the material of the test strips, two-dimensional test areas with variable lift thickness and moisture content were then tested. Spatial analyses of the in situ measurements were performed to identify the spatial distribution of soil properties. The interpretation of the ground condition was then compared to machine output for evaluating the roller measurement systems and the proposed roller calibration procedure.