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Hindawi Publishing Corporation Advances in Civil Engineering Volume 2011, Article ID 783836, 15 pages doi:10.1155/2011/783836 Research Article Field Assessment and Specification Review for Roller-Integrated Compaction Monitoring Technologies David J. White, Pavana K. R. Vennapusa, and Heath H. Gieselman Department of Civil, Construction, and Environmental Engineering, Center for Earthworks Engineering Research, Iowa State University of Science and Technology, Ames, IA 50011-8664, USA Correspondence should be addressed to Pavana K. R. Vennapusa, [email protected] Received 1 May 2011; Accepted 31 July 2011 Academic Editor: Sai K. Vanapalli Copyright © 2011 David J. White et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Roller-integrated compaction monitoring (RICM) technologies provide virtually 100-percent coverage of compacted areas with real-time display of the compaction measurement values. Although a few countries have developed quality control (QC) and quality assurance (QA) specifications, broader implementation of these technologies into earthwork construction operations still requires a thorough understanding of relationships between RICM values and traditional in situ point test measurements. The purpose of this paper is to provide: (a) an overview of two technologies, namely, compaction meter value (CMV) and machine drive power (MDP); (b) a comprehensive review of field assessment studies, (c) an overview of factors influencing statistical correlations, (d) modeling for visualization and characterization of spatial nonuniformity; and (e) a brief review of the current specifications. 1. Introduction Roller-integrated compaction monitoring (RICM) technolo- gies refer to sensor measurements integrated into com- paction machines. Work in this area was initiated over 30 years ago in Europe for smooth drum rollers compacting granular soils and involved instrumenting the roller with an accelerometer and calculating the ratio of the fundamental frequency to the first harmonic [1, 2]. Modern sensor tech- nologies, computers, and global positioning system (GPS) technologies now make it possible to collect, transmit, and visualize a variety of RICM measurements in real time. As a quality assessment tool for compaction of earth materials, these technologies oer tremendous potential for field controlling the construction process to meet performance quality standards. Recent eorts in the United States (US) have focused attention on how RICM technologies can be used in road building [35] and relating selected RICM parameters to mechanistic pavement design values. Several manufactures currently oer RICM technologies on smooth drum vibratory roller configurations for com- paction of granular materials and asphalt, and nonvibratory roller configurations for compaction of cohesive materials. The current technologies calculate: (1) an index value based on a ratio of selected frequency harmonics for a set time interval for vibratory compaction [1, 2], (2) ground stiness or dynamic elastic modulus based on a drum- ground interaction model for vibratory compaction [68], or (3) a measurement of rolling resistance calculated from machine drive power (MDP) for vibratory and nonvibratory compaction [9]. When the accelerometer-based measure- ment system provides automatic feedback control for roller vibration amplitude and/or frequency and/or roller speed control, it is referred to as “intelligent” compaction and oers the advantage of reducing the potential for drum “bouncing”. The MDP approach has the advantage of working in both vibratory and static modes [9] and has its origin in the discipline of terramechanics. Recent finding from the Mars Exploratory Rover (MER) mission demonstrated that the MDP approach can be applied to determine Martian regolith cohesion and friction angle by monitoring the electrome- chanical work expended [10]. Future RICM technologies may provide information on soil mineralogy and moisture content but are currently only a subject of research. Regardless of the technology, by making the compaction machine a measuring device and insuring that compaction

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  • Hindawi Publishing CorporationAdvances in Civil EngineeringVolume 2011, Article ID 783836, 15 pagesdoi:10.1155/2011/783836

    Research Article

    Field Assessment and Specification Review for Roller-IntegratedCompaction Monitoring Technologies

    David J. White, Pavana K. R. Vennapusa, and Heath H. Gieselman

    Department of Civil, Construction, and Environmental Engineering, Center for Earthworks Engineering Research,Iowa State University of Science and Technology, Ames, IA 50011-8664, USA

    Correspondence should be addressed to Pavana K. R. Vennapusa, [email protected]

    Received 1 May 2011; Accepted 31 July 2011

    Academic Editor: Sai K. Vanapalli

    Copyright © 2011 David J. White et al. This is an open access article distributed under the Creative Commons Attribution License,which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

    Roller-integrated compaction monitoring (RICM) technologies provide virtually 100-percent coverage of compacted areas withreal-time display of the compaction measurement values. Although a few countries have developed quality control (QC) andquality assurance (QA) specifications, broader implementation of these technologies into earthwork construction operations stillrequires a thorough understanding of relationships between RICM values and traditional in situ point test measurements. Thepurpose of this paper is to provide: (a) an overview of two technologies, namely, compaction meter value (CMV) and machinedrive power (MDP); (b) a comprehensive review of field assessment studies, (c) an overview of factors influencing statisticalcorrelations, (d) modeling for visualization and characterization of spatial nonuniformity; and (e) a brief review of the currentspecifications.

    1. Introduction

    Roller-integrated compaction monitoring (RICM) technolo-gies refer to sensor measurements integrated into com-paction machines. Work in this area was initiated over 30years ago in Europe for smooth drum rollers compactinggranular soils and involved instrumenting the roller with anaccelerometer and calculating the ratio of the fundamentalfrequency to the first harmonic [1, 2]. Modern sensor tech-nologies, computers, and global positioning system (GPS)technologies now make it possible to collect, transmit, andvisualize a variety of RICM measurements in real time. Asa quality assessment tool for compaction of earth materials,these technologies offer tremendous potential for fieldcontrolling the construction process to meet performancequality standards. Recent efforts in the United States (US)have focused attention on how RICM technologies can beused in road building [3–5] and relating selected RICMparameters to mechanistic pavement design values.

    Several manufactures currently offer RICM technologieson smooth drum vibratory roller configurations for com-paction of granular materials and asphalt, and nonvibratoryroller configurations for compaction of cohesive materials.

    The current technologies calculate: (1) an index valuebased on a ratio of selected frequency harmonics for a settime interval for vibratory compaction [1, 2], (2) groundstiffness or dynamic elastic modulus based on a drum-ground interaction model for vibratory compaction [6–8],or (3) a measurement of rolling resistance calculated frommachine drive power (MDP) for vibratory and nonvibratorycompaction [9]. When the accelerometer-based measure-ment system provides automatic feedback control for rollervibration amplitude and/or frequency and/or roller speedcontrol, it is referred to as “intelligent” compaction and offersthe advantage of reducing the potential for drum “bouncing”.The MDP approach has the advantage of working in bothvibratory and static modes [9] and has its origin in thediscipline of terramechanics. Recent finding from the MarsExploratory Rover (MER) mission demonstrated that theMDP approach can be applied to determine Martian regolithcohesion and friction angle by monitoring the electrome-chanical work expended [10]. Future RICM technologiesmay provide information on soil mineralogy and moisturecontent but are currently only a subject of research.

    Regardless of the technology, by making the compactionmachine a measuring device and insuring that compaction

  • 2 Advances in Civil Engineering

    requirements are met during construction, the compactionprocess can be better controlled to improve quality, reducerework, maximize productivity, and minimize costs [11].Recent advancements with global positioning systems (GPS)add a significant benefit with real time spatial viewing of theRICM values. Some of these technologies have recently beenimplemented on full-scale pilot earthwork and asphalt con-struction projects in the US [12–18], and its use is anticipatedto increase in the upcoming years. Effective implementationof this technology needs proper understanding of the rela-tionships between RICM values and traditional in situ pointtest compaction measurements (e.g., static or dynamic plateload test modulus, density, etc.). This builds confidence inthe technology and provides insight into the key parametersaffecting the machine measurement values.

    The purpose of this paper is to provide: (a) an overviewof two technologies—compaction meter value (CMV) andmachine drive power (MDP); (b) a summary of fieldevaluation studies, (c) an overview of factors influencing thestatistical correlations, (d) modeling for visualization andcharacterization of spatial nonuniformity, and (e) a briefreview of the current specifications.

    2. Overview of CMV and MDP Technologies

    Compaction meter value (CMV) is a dimensionless com-paction parameter developed by Geodynamik that dependson roller dimensions, (i.e., drum diameter and weight)and roller operation parameters (e.g., frequency, amplitude,speed) and is determined using the dynamic roller response[19, 20]. CMV is calculated using (1), where C is a constant(used as 300 for the results presented in this paper), andA2Ω = the acceleration of the first harmonic componentof the vibration, AΩ = the acceleration of the fundamentalcomponent of the vibration [8]:

    CMV = C · A2ΩAΩ

    . (1)

    According to Geodynamik [21], CMV at a given pointindicates an average value over an area whose width equalsthe width of the drum and length equal to the distance theroller travels in 0.5 seconds. At least two manufactures haveused the CMV technology as part of their RICM systems(Figure 1). The Geodynamik system also measures theresonant meter value (RMV) which provides an indicationof the drum behavior (continuous contact, partial uplift,double jump, rocking motion, and chaotic motion). RMVis not discussed in detail here, but it is important to notethat the drum behavior affects the CMV measurements [6]and therefore CMV must be interpreted in conjunction withRMV [22].

    Machine drive power (MDP) technology relates themechanical performance of the roller during compaction tothe properties of the compacted soil. The use of MDP asa measure of soil compaction is a concept originated fromstudy of vehicle-terrain interaction [23]. The basic premiseof determining soil compaction from changes in equipmentresponse is that the efficiency of mechanical motion pertainsnot only to the mechanical system but also to the physical

    properties of the material being compacted. More detailedbackground information on the MDP system is provided in[9]. The basic formula for MDP is

    MDP = Pg −WV(

    sinα +a

    g

    )− (mV + b), (2)

    where Pg = gross power needed to move the machine (kJ/s),W = roller weight (kN), a = machine acceleration (m/s2),g = acceleration of gravity (m/s2), α = slope angle (rollerpitch from a sensor), V = roller velocity (m/s), and m (kJ/m)and b (kJ/s) = machine internal loss coefficients specific toa particular machine [9]. The second and third terms of (2)account for the machine power associated with sloping gradeand internal machine loss, respectively. MDP is a relativevalue referencing the material properties of the calibrationsurface, which is generally a hard compacted surface (MDP =0 kJ/s). Positive MDP values therefore indicate material thatis less compact than the calibration surface, while negativeMDP values would indicate material that is more compactedthan the calibration surface (i.e., less roller drum sinkage).In some recent field studies [13], the MDP output value hasbeen scaled to MDP80 or MDP40 depending on the modifiedsettings which are recalculated to range between 1 and 150using (3) and (4), respectively,

    MDP80 = 150− 1.37 (MDP), (3)MDP40 = 150− 2.75 (MDP). (4)

    For the MDP80 calculation, the calibration surface withMDP = 0 kJ/s is scaled to MDP80 = 150, and a soft surfacewith MDP = 108.47 kJ/s (80000 lb-ft/s) is scaled to MDP80 =1. For the MDP40 calculation, the calibration surface withMDP = 0 kJ/s is scaled to MDP40 = 150 and a soft surfacewith MDP = 54.23 kJ/s (40000 lb-ft/s) is scaled to MDP40 =1.

    Effective use of RICM technologies is aided by theintegration of GPS position information and an on-boardcomputer monitor (Figure 1) which displays the rollerlocation, machine measurement values (i.e., CMV or MDP),vibration amplitude and frequency, and roller speed. Thus,the technology enables a roller operator to make judgmentsregarding the condition of the compacted fill material in realtime. If real-time kinematic (RTK) GPS systems are used,those systems reportedly have position accuracies of about±10 mm in the horizontal plane and ±20 mm in the verticalplane [24].

    3. Field Evaluation of CMVand MDP Technologies

    Field evaluation studies beginning in about 1980 havedocumented correlations between RICM measurements andvarious traditionally used point measurements. A summaryof key findings from these different studies, types of rollersused, and materials tested is provided in Table 1. A varietyof QC/QA measurements have been used in the documentedcorrelation studies, which include:

  • Advances in Civil Engineering 3

    (a) (b)

    Figure 1: Photographs of on-board display units by Caterpillar (a) and Dynapac (b).

    (a) nuclear gauge (NG), electrical soil density gauge(SDG), water balloon method, sand cone replace-ment method, radio isotope method, “undisturbed”shelby tube sampling, and drive core samples todetermine moisture content and dry unit weight,

    (b) light weight deflectometer (LWD), soil stiffness gauge(SSG), static plate load test (PLT), falling weightdeflectometer (FWD), Briaud compaction (BCD),dynamic seismic pavement analyzer (D-SPA), andClegg hammer to determine stiffness or modulus,

    (c) dynamic cone penetrometer (DCP), cone pene-tration testing (CPT), “undisturbed” shelby tubesampling, and rut depth measurements under heavytest rolling to determine shear strength or Californiabearing ratio (CBR).

    Most of the field studies involved constructing andtesting controlled field test sections for research purposes andcorrelation development, while a few studies were conductedon full-scale earthwork construction projects where RICMwas implemented as part of the project specifications [12,13].

    Based on the findings from a comprehensive correlationstudy conducted on 17 different soil types from multipleproject sites as part of the National Cooperative HighwayResearch Program (NCHRP) 21-09 project [25], the factorsthat commonly affect the correlations are as follows:

    (1) heterogeneity in underlying layer support conditions,

    (2) high moisture content variation,

    (3) narrow range of measurements,

    (4) machine operation setting variation (e.g., amplitude,frequency, speed, and roller “jumping”),

    (5) nonuniform drum/soil contact conditions,

    (6) uncertainty in spatial pairing of point measurementsand roller MVs,

    (7) limited number of measurements,

    (8) not enough information to interpret the results,

    (9) intrinsic measurement errors associated with theRICM and in situ point measurements.

    In general, results from controlled field studies indicatethat statistically valid simple linear or simple nonlinearcorrelations between RICM values and compaction layerpoint-MVs (e.g., modulus or density) are possible when thecompaction layer is underlain by a relatively homogenousand stiff/stable supporting layer. For example, Figure 2presents simple linear regression relationships between CMVand in situ LWD modulus and dry density point-MVsobtained from a calibration test strip with plan dimensionsof 30 m × 2 m. The test strip consisted of silty sand withgravel base material underlain by a very stiff fly ash stabilizedsubgrade layer. For this case, correlations between CMV andboth LWD modulus and dry density measurements showedR2 > 0.8.

    On the contrary, many field studies summarized inTable 1 indicate that modulus- or stiffness-based measure-ments (i.e., determined by FWD, LWD, PLT, etc.) generallycorrelate better with the RICM measurements than com-paction layer dry unit weight or CBR measurements. Thisis illustrated in Figures 3 and 4. Data presented in Figure 3was obtained from several calibration and production testareas with lean clay subgrade, recycled asphalt subbase,recycled concrete base, and crushed limestone base materialscompacted with a vibratory smooth drum roller. Datapresented in Figure 4 was obtained from several calibrationand production test areas with lean clay subgrade compactedusing a nonvibratory padfoot roller. CBR measurementspresented herein are obtained from DCP tests using empir-ical correlations between DCP index values and CBR [38].Figures 3 and 4 clearly indicate that CMV correlates betterwith LWD modulus point-MVs compared to dry unitweight or CBR point-MVs. One of the primary reasons forthis is that modulus measurements represent a compositelayered soil response under an applied load which simulatesvibratory drum-ground interaction. The density and CBRmeasurements are average measurements of the compactionlayer and do not directly represent a composite layered soilresponse under loading. Although DCP-CBR measurementsdid not correlate well in the two cases presented in Figures3 and 4, many field studies [13, 25, 34] have indicated thatDCP tests are effective in detecting deeper “weak” areas(at depths > 300 mm) that are commonly identified by

  • 4 Advances in Civil Engineering

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  • Advances in Civil Engineering 5

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    ngs

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    ts

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    omps

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    dW

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    mer

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    ysis

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    ion

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    Wh

    ite

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    rela

    tion

    sw

    ith

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    edpo

    orco

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    atio

    ns

    due

    toth

    eeff

    ect

    oflo

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    eria

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    surf

    ace.

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    riab

    ility

    obse

    rved

    inth

    eC

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    data

    was

    sim

    ilar

    toD

    CP

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    LWD

    mea

    sure

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    tsbu

    tn

    otto

    den

    sity

    mea

    sure

    men

    ts

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    ite

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    20m

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    lati

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  • 6 Advances in Civil Engineering

    Ta

    ble

    1:C

    onti

    nu

    ed.

    Ref

    eren

    ce;p

    roje

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  • Advances in Civil Engineering 7

    Ta

    ble

    1:C

    onti

    nu

    ed.

    Ref

    eren

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  • 8 Advances in Civil Engineering

    40 60 80 100 120 1400

    20

    40

    60

    80C

    MV

    CMV = 1.2 (LWD modulus) − 70.4n = 30R2 = 0.83

    300 mm dia. plate LWD modulus (MPa)

    (a)

    0

    20

    40

    60

    80

    CM

    V

    Dry unit weight (kN/m3)

    15.6 16.2 16.8 17.4 18

    n = 30R2 = 0.81

    CMV = 31.55 (dry unit weight) − 490.8

    (b)

    Figure 2: Simple linear regressions between CMV (amplitude = 1.00 mm) and in situ point measurements (LWD modulus and dry unitweight)—silty sand with gravel underlain by fly ash stabilized subgrade.

    RICM measurements and not by point-MVs obtained onthe surface. This is primarily because of the differences inmeasurement influence depths. Accelerometer based rollermeasurements have measurement influence depths rangingfrom 0.8 m to 1.5 m depending on soil layering, drum mass,and excitation force [25, 39–41], while machine drive powerbased measurements range from 0.3 to 1.3 m depending onthe heterogeneity in subsurface conditions [33]. On the otherhand, most point-MVs have influence depths

  • Advances in Civil Engineering 9

    0 10 20 30 40 50 60

    CM

    V

    0

    5

    10

    15

    20

    25

    30CMV = 1.62 exp0.05 (LWD modulus)R2 = 0.86n = 104

    300 mm dia. plate LWD modulus (MPa)

    (a)

    CM

    V

    0

    5

    10

    15

    20

    25

    30

    Dry unit weight (kN/m3)

    10 12 14 16 18 20 22

    R2 = 0n = 85

    (b)

    CM

    V

    0

    5

    10

    15

    20

    25

    30

    R2 = 0.18

    0 5 10 15 20 25 30

    Lean clay subgrade

    Recycled asphalt subbase

    Recycled concrete base

    Crushed limestone subbase

    CMV = 0.4 CBR + 4.5

    n = 50

    DCP-CBR of compaction layer (%)

    (c)

    Figure 3: Relationships between CMV (theoretical amplitude = 1.50 mm) and in situ point measurements (LWD modulus, dry unit weight,and CBR determined from DCP).

    construction where the backfill may not be as compactas the neighboring unexcavated materials. After subgradepreparation, the area was mapped using a smooth drummachine in seven lanes using a vibration amplitude = 2.1 mmand frequency = 29 Hz. DCP tests were performed at 144locations in the upper 200 mm (shown in gray circles onFigure 6) following roller mapping passes. The DCP testlocations were strategically spaced such that the boundariesof compacted and uncompacted areas were captured duringKriging interpolation.

    CMV and MDP spatial data along with experimentaland theoretical variogram models are shown in Figure 6.Log transformation of CMV was required to detrend theexperimental variogram (details on detrending is explained

    in detail in Vennapusa et al. [22]). Kriged surface map andvariogram model generated for the DCP index values are alsopresented in Figure 6. The univariate statistics (mean (μ),standard deviation (σ), and coefficient of variation (COV))of the measurement values are also provided on the figurefor reference. The compacted and uncompacted areas weregenerally well captured by the CMV/MDP and DCP indexmeasurements; however, they were more clearly delineatedby the DCP Index measurements.

    Univariate statistics show that the COV of the MDP(89%) and DCP index (86%) measurements are comparableand are also significantly higher compared to that of CMV(39%). Similarly, the exponential variogram models of MDPand DCP index exhibit significantly lower range values than

  • 10 Advances in Civil Engineering

    MD

    P40

    60

    80

    100

    120

    140

    160

    0 2 4 6 8 10 12 14

    MDP40 = 68.3 (LWD modulus)0.25R2 = 0.63n = 76

    300 mm dia. plate LWD modulus (MPa)

    (a)

    MD

    P40

    60

    80

    100

    120

    140

    160

    Dry unit weight (kN/m3)

    13 14 15 16 17 18 19 20

    R2 = 0n = 76

    (b)

    MD

    P40

    60

    80

    100

    120

    140

    160

    Moisture content, w (%)

    12 14 16 18 20 22 24 26 28 30

    R2 = 0.15n = 76

    MDP40 = −1.8 (w) + 134.6

    (c)

    MD

    P40

    60

    80

    100

    120

    140

    160

    DCP-CBR of compaction layer (%)

    0 1 2 3 4 5 6 7

    R2 = 0.51n = 76

    MDP40 = 100.7 (CBR)0.08

    (d)

    Figure 4: Example 3: Relationships between MDP40 (obtained in static mode) and in situ point measurements (LWD modulus, dry unitweight, moisture content, and CBR determined from DCP)—Sandy clay to silty clay subgrade.

    CMV. This suggests that the MDP and DCP index mea-surements have less spatial continuity and higher variabilitycompared to CMV measurements. This high variability islikely due to differences in the measurement influence depthsof these measurements as discussed earlier in this paper. DCPindex values presented in Figure 6 are based on average valuesin the top 300 mm of the surface.

    In addition to using spatial analysis for visualizationpurposes, analysis from some field studies by the authors [36]has indicated that experimental semivariograms of RICMvalues sometimes show nested structures with distinctivelydifferent long- and short-range components. The nestedstructures are very likely linked to spatial variation in theunderlying layer support conditions. These observationsare new, have not been fully evaluated, and warrant moreresearch. Further, a field study by White et al. [35] reported

    that variograms developed for two different spatial areaswith similar univariate statistics (i.e., mean and standarddeviation) showed distinctly different shapes of variogramswith different spatial statistics, which illustrate the impor-tance of spatial modeling to obtain better characterizationof “nonuniformity” compared to using univariate statistics.This emphasizes the importance of dealing with “nonuni-formity” in a spatial perspective rather than in a univariatestatistics perspective.

    5. Implementation of RICM Technology

    A few countries and governmental agencies have devel-oped specifications to facilitate implementation of RICMtechnologies into earthwork and hot mix asphalt (HMA)construction practices [44]. The international society of soil

  • Advances in Civil Engineering 11

    MD

    P40

    60

    80

    100

    120

    140

    160

    0 2 4 6 8 10 12 14

    ELWD-Z3 (MPa)

    R2 = 0.71n = 76

    MDP40 = 82.3 (LWD modulus)0.25 − 0.8 (w)

    (a)

    MD

    P40

    60

    80

    100

    120

    140

    160

    R2 = 0.51

    DCP-CBR of compaction layer (%)

    0 1 2 3 4 5 6 7

    n = 76

    MDP40 = 103.8 (CBR)0.08 − 0.2 (w)

    (b)

    Figure 5: Example 4: Multivariate non-linear regression analysis between MDP40 and in situ point measurements (LWD modulus and CBRdetermined from DCP) using moisture content—Sandy clay to silty clay subgrade.

    mechanics and geotechnical engineering (ISSMGE) [39],Minnesota department of transportation (DOT) [45, 46],Austrian [47], German [48], and Sweden [49] specificationsrequire performing either static or dynamic plate load testson calibration strips to determine average target values(typically based on 3 to 5 measurements) and use the samefor QA in production areas. The ISSMGE, Austrian, andGerman specifications suggest performing at least three staticplate load tests in locations of low, medium, and highdegree of compaction during calibration process. Further,it is specified that linear regression relationships betweenroller compaction measurement values and plate load testresults should achieve a regression coefficient, R ≥ 0.7.Although it is not clear yet what the right number of testmeasurements is to develop a field calibration, the experienceof the authors shows that by increasing the number ofmeasurements to 10–15 points, this substantially increasesthe statistical significance of the predictions.

    One of the major limitations of the existing RICMspecifications is that the acceptance requirements (i.e.,percent target value limits, acceptable variability, etc.) aretechnology specific and somewhat based on local experience.This limitation hinders widespread acceptance of thesespecifications into practice as there are currently at leastten different RICM technologies. Significant efforts arebeing made in the US in developing widely acceptableand technology-independent specifications [3–5]. Based onfeedback obtained from various state and federal agencypersonnel in recent national level workshops conductedon this topic, White and Vennapusa [4] documented thefollowing as the key attributes of RICM specification:

    (1) descriptions of the rollers and configurations,

    (2) guidelines for operations (speed, vibration frequencyand amplitude, and track overlap),

    (3) records to be reported (time stamp, operations/mode, soil type, moisture content, layer thickness,etc.),

    (4) repeatability and reproducibility measurements forRICM values,

    (5) ground conditions (smoothness, levelness, isolatedsoft/wet spots),

    (6) calibration procedures for rollers and selection ofcalibration areas,

    (7) regression analysis between RICM values and pointmeasurements,

    (8) number and location of quality control (QC) andquality assurance (QA) tests,

    (9) operator training/certification, and

    (10) acceptance procedures/corrective actions based onachievement of minimum RICM target values andassociated variability.

    Several new and innovative specification concepts havebeen proposed by researchers in the past few years [4, 13,25]. These concepts primarily vary in the way the itemnumber 10 listed above is dealt in the specification, thatis, in the required level of upfront calibration work anddata analysis which consequently leads to differences inthe level of confidence in the quality of the completedwork. A few of those concepts have been beta tested ondemonstration level projects [25] but have never been fullyevaluated on full scale projects to explore their limitationsand advantages. More coordination between researchersand practitioners is needed to carefully evaluate theseconcepts and is a high-priority step forward to successfullyimplement the RICM technologies in practice. Further,integrating advanced analytical methods discussed in this

  • 12 Advances in Civil Engineering

    10203040

    Transverse length (m)

    0 4 8 12 16

    Lon

    gitu

    din

    alle

    ngt

    h(m

    )

    4

    8

    12

    16

    20

    24

    28

    32

    CMV

    μ = 20.4σ = 7.9COV = 39%

    (a)

    Transverse length (m)0 4 8 12 16

    4

    8

    12

    16

    20

    24

    28

    32

    −50510

    μ = 3.7σ = 3.3COV = 89%

    MDP(kJ/s)

    (b)

    Transverse length (m)

    0 4 8 12 16

    4

    8

    12

    16

    20

    24

    28

    32

    Scarifiedzone

    Compactedzone

    Spottests

    20

    406080

    DCP index(mm/blow)

    μ = 43σ = 37COV = 86%

    (c)

    Lag distance (m)

    Var

    iogr

    am(C

    MV

    )2

    0

    0.02

    0.04

    0.06

    0.08Parameter log CMV

    0 5 10 15 20

    Experimental

    Exponential

    Nugget—0Sill—0.038Range—2.8Cressie “goodness”—0.02

    (d)

    Lag distance (m)

    0 5 10 15 20

    Var

    iogr

    am(k

    J/s)

    2

    Experimental

    Exponential

    0

    4

    8

    12

    16

    20Parameter MDP

    Nugget—0Sill—11.2Range—0.8Cressie “goodness”—0.002

    (e)

    Lag distance (m)

    0 5 10 15 20

    Var

    iogr

    am(m

    m/b

    low

    )2

    Parameter DCP index

    0

    500

    1000

    1500

    2000

    2500

    Experimental

    Exponential

    Nugget—450

    Sill—1000Range—1.2Cressie “goodness”—0.006

    (f)

    Figure 6: Spatial comparison of dynamic cone penetration (DCP) index and roller-integrated CMV and MDP measurements on compactedand scarified Edwards glacial till subgrade soil.

    paper (such as simple and multiple regression analysis todevelop correlations and target values and spatial analysisto address nonuniformity) into a specification along withdevelopment of simple and ready-to-use software tools ismuch necessary to help advance the technology.

    6. Concluding Remarks

    RICM technologies with real-time display capabilities and100% coverage of compaction data offer significant advan-tages to the earthwork construction industry. Integration ofthese technologies into practice requires proper understand-ing of the correlations between RICM values and compactionmeasurements (e.g., density, modulus) and factors that influ-ence these correlations. This paper provided an overviewof two technologies (i.e., CMV and MDP) and a review of

    field correlation studies documented in the literature. Reviewof the literature revealed correlations between the RICMmeasurements and various in situ tests used to measuredensity, modulus or stiffness, shear strength, and CBR.Results from field studies indicated that simple linear ornonlinear correlations between any of these measurementsare possible if the compaction layer is placed over a “stable”and “homogenous” underlying layer. If the underlying layeris not stable or homogenous, correlations are adverselyaffected. For those cases, in general, relationships betweenRICM and modulus based measurements (e.g., LWD orFWD or PLT modulus) are better compared to RICM and drydensity or CBR measurements. Multiple regression analysiscan be performed incorporating properties of the underlyinglayers and moisture content to improve correlations. Otherimportant factors that affect the correlations include narrow

  • Advances in Civil Engineering 13

    range of measurements, variations in machine settings,nonuniform conditions across the drum width, limited num-ber of measurements, and measurement error associatedwith both RICM and in situ point measurements.

    Geostatistical spatial modeling techniques can be utilizedfor data visualization and characterization of spatial nonuni-formity using spatially referenced RICM data. To demon-strate the application of spatial analysis for visualization,an example CMV and MDP data set over a spatial areawas used in comparison with DCP index measurements.Analysis results indicated that the compacted and uncom-pacted areas over the spatial area were well captured byall the measurements. Some field studies documented inthe literature indicate that geostatistical semivariograms ofRICM measurements can be used for construction processcontrol and also to analyze variations in the underlyingsupport conditions. These observations are new, have notbeen fully evaluated, and warrant more research.

    Review of current RICM specifications revealed a poten-tial limitation with the acceptance requirements (i.e., percenttarget value limits, acceptable variability, etc.) being technol-ogy specific and somewhat based on local experience. Thislimitation hinders widespread acceptance of these specifica-tions into practice as there are currently at least ten differentRICM technologies. Several new specification concepts havebeen recently documented in the literature with variationsin the way calibration work is performed and acceptancerequirements are established. These concepts require detailedfield evaluation to explore their limitations and advantages.Integration of advanced analytical methods discussed in thispaper (such as simple and multiple regression analysis todevelop correlations and target values, and spatial analysisto address nonuniformity) into a specification along withdevelopment of simple and ready-to-use software tools aremuch necessary to help advance the technology.

    Acknowledgments

    The results presented in this paper are from several researchprojects sponsored by the Highway Division of the IowaDepartment of Transportation (DOT), Minnesota DOT,Federal Highway Administration, NCHRP, Caterpillar, Inc.,and Iowa State University. The findings and opinionsexpressed in this paper are those of the authors and do notnecessarily reflect the views of the sponsor and administra-tors. Several research associates, graduate, and undergradu-ate students at Iowa State University provided assistance withfield testing.

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  • 14 Advances in Civil Engineering

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  • Advances in Civil Engineering 15

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