scholarly journals Evaluation of Resilient Modulus of Subgrade and Base Materials in Indiana and Its Implementation in MEPDG

2014 ◽  
Vol 2014 ◽  
pp. 1-14 ◽  
Author(s):  
Richard Ji ◽  
Nayyarzia Siddiki ◽  
Tommy Nantung ◽  
Daehyeon Kim
Keyword(s):  
Resilient Modulus ◽  
Falling Weight Deflectometer ◽  
Statistical Tool ◽  
Material Constants ◽  
Analysis And Evaluation ◽  
Subgrade Soils ◽  
Base Materials ◽  
Subgrade Soil ◽  
Different Seasons ◽  
Falling Weight

In order to implement MEPDG hierarchical inputs for unbound and subgrade soil, a database containing subgradeMR, index properties, standard proctor, and laboratoryMRfor 140 undisturbed roadbed soil samples from six different districts in Indiana was created. TheMRdata were categorized in accordance with the AASHTO soil classifications and divided into several groups. Based on each group, this study develops statistical analysis and evaluation datasets to validate these models. Stress-based regression models were evaluated using a statistical tool (analysis of variance (ANOVA)) andZ-test, and pertinent material constants (k1,k2andk3) were determined for different soil types. The reasonably good correlations of material constants along withMRwith routine soil properties were established. Furthermore, FWD tests were conducted on several Indiana highways in different seasons, and laboratory resilient modulus tests were performed on the subgrade soils that were collected from the falling weight deflectometer (FWD) test sites. A comparison was made of the resilient moduli obtained from the laboratory resilient modulus tests with those from the FWD tests. Correlations between the laboratory resilient modulus and the FWD modulus were developed and are discussed in this paper.

Field Study of In Situ Subgrade Soil Response Under Flexible Pavements

1998 ◽  
Vol 1639 (1) ◽  
pp. 23-35 ◽  
Author(s):  
Shongtao Dai ◽  
Dave Van Deusen
Keyword(s):  
Resilient Modulus ◽  
Soil Pressure ◽  
Vertical Pressure ◽  
Soil Response ◽  
Subgrade Soils ◽  
Linear Elastic ◽  
Subgrade Soil ◽  
In Situ Sensors ◽  
Falling Weight

Falling weight deflectometer (FWD) and truck tests were performed on three instrumented flexible pavement sections at the Minnesota Road Research project. The purposes of the study were (1) to investigate sub-grade soil response under FWD and moving truck loads and (2) to estimate in situ resilient modulus of the subgrade soil. The truck tests were performed at various speeds ranging from 16 to 78 km/h. The subgrade deformations and the vertical pressures on the top of the subgrade soils were measured from in situ displacement and soil pressure gauges. The experimental results showed that the deformations and the vertical pressures, in general, did not show significant dependency of truck speed within the above speed range. However, a slight decrease of the vertical pressure with increase of speed was observed for a thin conventional pavement section, while the vertical pressure in a relatively thick pavement section appeared to be less sensitive to speed. The results from FWD tests indicated that the subgrade deformation was linearly related to the FWD loads up to approximately 40 kN. Furthermore, a method is presented to estimate in situ subgrade modulus using the linear elastic theory and the measurements from the in situ sensors. The estimated modulus is comparable with the laboratory results at a low deviator stress level and is lower than modulus obtained from the backcalculation using FWD deflection basins.

Relating Laboratory and Field Moduli of Texas Base Materials

1998 ◽  
Vol 1639 (1) ◽  
pp. 1-11 ◽  
Author(s):  
S. Nazarian ◽  
J. Rojas ◽  
R. Pezo ◽  
D. Yuan ◽  
I. Abdallah ◽  
...  
Keyword(s):  
Resilient Modulus ◽  
Design Method ◽  
Field Tests ◽  
Pavement Design ◽  
Falling Weight Deflectometer ◽  
Nondestructive Tests ◽  
Second Stage ◽  
Base Materials ◽  
Two Stages ◽  
Falling Weight

Resilient modulus of base is an important parameter in the AASHTO pavement design method. However, the manner to determine this parameter is not well defined. Recent efforts in combining the resilient moduli from laboratory testing with those obtained in the field using nondestructive testing devices are presented. Laboratory tests were carried out in two stages. In the first stage, virgin materials from the quarry compacted to optimum moisture content were tested. In the second stage, similar base materials were retrieved from in-service roads. Specimens were prepared and tested at the corresponding field densities and moisture contents. Nondestructive tests were performed with the Falling Weight Deflectometer and the Seismic Pavement Analyzer. Based on tests on 10 different base materials from different parts of Texas, it was concluded that it may be difficult to directly compare moduli from laboratory and field tests; however, they can be combined for effective pavement design.

Testing Methodology for Resilient Modulus of Base Materials

1996 ◽  
Vol 1547 (1) ◽  
pp. 46-52 ◽  
Author(s):  
S. Nazarian ◽  
R. Pezo ◽  
S. Melarkode ◽  
M. Picornell
Keyword(s):  
Resilient Modulus ◽  
Design Method ◽  
Testing Procedure ◽  
State Agencies ◽  
Technical Literature ◽  
Subgrade Soils ◽  
Base Materials ◽  
Texas Department ◽  
Confining Pressures ◽  
End Restraint

Resilient moduli of base and subgrade materials are important parameters in the new pavement design method adopted by AASHTO and many state agencies. Several testing protocols for determining the resilient moduli of subgrade soils have been proposed and evaluated in the technical literature. Unfortunately, less effort has been focused on developing protocols appropriate for base materials. The main objective was to describe a resilient modulus testing procedure that has been developed for the Texas Department of Transportation. The proposed procedure contains the main steps of the AASHTO T294-92 procedure, with several exceptions. Namely, the loading sequence of the T294-92 procedure was modified to avoid subjecting the specimens to high devi-atoric stresses at low confining pressures. The conditioning cycles were replaced by a procedure in which the specimen was grouted to the platens to minimize disturbance to the specimen during stage testing. The effects of end restraint on the vertical strains were minimized by measuring the deformations of the middle one-third of the specimen. To avoid well-known problems with mounting linear variable differential transformers on the specimen, noncontact probes were used to measure deformations. To maximize the amount of information gained, the lateral deformations were also measured with noncontact probes to determine the Poisson's ratio. On the basis of tests on nine synthetic specimens with known properties and nine different base materials from different parts of Texas, it was concluded that the proposed methodology yields accurate and repeatable results.

Temperature Correction on Falling Weight Deflectometer Measurements

2000 ◽  
Vol 1716 (1) ◽  
pp. 30-39 ◽  
Author(s):  
Dar-Hao Chen ◽  
John Bilyeu ◽  
Huang-Hsiung Lin ◽  
Mike Murphy
Keyword(s):  
Close Agreement ◽  
Temperature Correction ◽  
Falling Weight Deflectometer ◽  
Temperature Dependent ◽  
Different Seasons ◽  
Falling Weight ◽  
Correction Equations

Repeated falling weight deflectometer (FWD) tests were conducted at three sites. The tests were conducted at regular intervals for 2 to 3 consecutive days per location, and also done during different seasons in order that the widest possible range of temperatures could be obtained. The influence of cracks on temperature correction was also investigated. Temperature correction equations for deflection and moduli were developed so that users could be allowed to input their own reference temperatures. For all test pads, only the W1 and W2 deflections were found to be significantly affected by temperature. Comparisons with other reported temperature correction equations showed close agreement for deflection, but not for moduli. Tests were also run on cracked locations. Temperature did not affect the response of the cracked pavement as much as it did the intact pavement. Due to the different temperature-dependent characteristics of intact and cracked locations, the equations developed from the intact locations may not be used on cracked locations.

Dynamic Interpretation for Impulsive Deflection Test on Flexible Pavements

1998 ◽  
Vol 14 (2) ◽  
pp. 91-100
Author(s):  
Der-Wen Chang ◽  
Chia-Ling Chang
Keyword(s):  
Iterative Scheme ◽  
Flexible Pavements ◽  
Falling Weight Deflectometer ◽  
Correction Procedure ◽  
Subgrade Soils ◽  
Forward Analysis ◽  
Dynamic Interpretation ◽  
Equivalent Number ◽  
Deflection Test ◽  
Falling Weight

AbstractIn this study, a computer program DBFWD is developed for data analysis of Falling Weight Deflectometer (FWD) test on flexible pavements. To backcalculate the layer moduli of the pavement, a number of iterative backcalculation schemes were employed with the forward analysis of the Green's flexibility influence functions. The temperature and the moisture influences on material moduli of the asphalt surface and the subgrade soils were considered in the analysis. As the result, the iterative scheme based on the peak deflection ratios was selected to backcalculate the layer moduli of local pavements. Owing to the correction procedure used in the program, interpretations with four original deflections were found more accurate than those with equivalent number of modified deflections. Comparisons of program DBFWD with other static backcalculation programs on theoretical and experimental deflections indicated that dynamic interpretation is more effective in providing the layer modulus information. Despite of the requirements of accurate inputs of the layer thickness and the testing load for the analysis, a generalized application of the program needs to be clarified with model road test in demand.

Assessment of Falling Weight Deflectometer Data for Stabilized Flexible Pavements

2000 ◽  
Vol 1709 (1) ◽  
pp. 19-25 ◽  
Author(s):  
Alexander K. Appea ◽  
Imad L. Al-Qadi
Keyword(s):  
Resilient Modulus ◽  
Ground Truth ◽  
Monitoring And Evaluation ◽  
Structural Condition ◽  
Base Layer ◽  
Falling Weight Deflectometer ◽  
Structural Capacity ◽  
Pavement Monitoring ◽  
Aggregate Base ◽  
Falling Weight

Backcalculation of pavement moduli through the utilization of the falling weight deflectometer (FWD) is used for pavement monitoring and evaluation. The performance and structural condition of nine flexible pavement test sections built in Bedford County, Virginia, have been monitored over the past 5 years using FWD. The nine sections include three groups with aggregate base layer thicknesses of 100, 150, and 200 mm, respectively. Sections 1, 4, and 7 are control, whereas Sections 2, 5, 8 and 3, 6, 9 are stabilized with geotextiles and geogrids, respectively. The FWD testing used five double-load drops ranging from 26.5 to 58.9 kN. The deflection basins obtained from the testing have been analyzed using the ELMOD backcalculation program to find the pavement structural capacity and to detect changes in the aggregate resilient modulus. The analysis shows a reduction in the backcalculated resilient modulus of the 100-mmthick base layer. The reduction was 33 percent over 5 years for the nonstabilized section compared with the geosynthetically stabilized section. The reduction in base layer resilient modulus may have resulted from subgrade fine migration into this layer as confirmed by excavation. The study confirms the effectiveness of using woven geotextile as a separator in a pavement system built over weak subgrade. This supports the continuous rutting measurements and ground truth excavation conducted in late 1997.

Relationship Between Backcalculated and Laboratory-Measured Resilient Moduli of Unbound Materials

2003 ◽  
Vol 1849 (1) ◽  
pp. 177-182 ◽  
Author(s):  
Gerardo W. Flintsch ◽  
Imad L. Al-Qadi ◽  
Youngjin Park ◽  
Thomas L. Brandon ◽  
Alexander Appea
Keyword(s):  
Resilient Modulus ◽  
Shift Factor ◽  
Falling Weight Deflectometer ◽  
Test Results ◽  
Structural Capacity ◽  
Bulk Stress ◽  
Stress Dependent ◽  
Falling Weight ◽  
Virginia Smart Road

The resilient moduli of an unbound granular subbase (used at the Virginia Smart Road) obtained from laboratory testing were compared with those backcalculated from in situ falling weight deflectometer deflection measurements. Testing was performed on the surface of the finished subgrade and granular subbase layer shortly after construction. The structural capacity of the constructed subgrade and the depth to a stiff layer were computed for 12 experimental sections. The in situ resilient modulus of the granular subbase layer (21-B) was then back-calculated from the deflections measured on top of that layer. The back-calculated layer moduli were clearly stress-dependent, showing an exponential behavior with the bulk stress in the center of the layer. Resilient modulus test results of laboratory-compacted specimens confirmed the stress dependence of the subbase material modulus. Three resilient modulus models were fitted to the data. Although all three models showed good coefficients of determination ( R2 > 90%), the K-θ model was selected because of its simplicity. The correlation between field-backcalculated and laboratory-measured resilient moduli was found to be strong. However, when the stress in the middle of the layer was used in the K-θ model, a shift in the resilient modulus, θ, was observed. This finding suggests that a simple shift factor could be used for the range of stress values considered.

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