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M-1 APPENDIX M. COMPARISON OF FINITE ELEMENT SIMULATIONS WITH LARGE- SCALE TANK MEASUREMENTS The finite element simulation results of the developed geosynthetic-reinforced and unreinforced pavement models were validated by comparing them to the Large-Scale Tank test measurements in terms of the surface deflection, the tensile strain at the bottom of the asphalt concrete, and the vertical pressures within the base and subgrade layers. Figure M-1 illustrates the location of the instruments, such as the linear variable deflection transducers (LVDTs), the tensile strain gauge, and the pressure sensors in the flexible pavement structures. Four LVDTs were mounted on the surface of asphalt concrete (i.e., L1âL4). LVDT 5 was used to examine the movement of the Large-Scale Tank boundary. The pressure sensors P1, P2, P3, P4, P5, P6, and P7 were used to measure the vertical compressive pressure in the base course or subgrade. The pressure sensors P21 and P22 were installed to record the horizontal pressure in the base course.
M-2 (a) Flexible pavement with a 6-inch base course (b) Flexible pavement with a 10-inch base course Figure M-1. Location of Instruments in Flexible Pavement Structures Figures M-2 to M-4 show the comparison of the surface deflections predicted by the finite element models and the Large-Scale Tank test measurements when the pavement structures were subjected to a 9-kip, 12-kip, and 16-kip load, respectively. The model-predicted surface deflections were in agreement with the Large-Scale Tank measurements from LVDTs 1, 2, and 3. The deviation between the measured surface deflection by LVDT 4 and that predicted by the finite element model existed because the surface deflection at this location was too small to be accurately captured by the LVDT. This indicates that the developed geosynthetic-reinforced and
M-3 unreinforced pavement models have high accuracy to predict the pavement surface deflections. The comparison of the tensile strain at the bottom of the asphalt concrete are plotted in Figures M-5 to M-7. The developed finite element models accurately predicted the tensile strain in the geogrid-reinforced and unreinforced pavement structures but slightly overestimated the tensile strain in the geotextile-reinforced pavement structures. Figures M-8 to M-10 present the comparison between the predicted vertical pressures within the base and subgrade layer and the measured results. Most of the measured pressure values were captured by the developed finite element models, except the measurement of pressure cells P1 and P7. There are a number of possible explanations for these discrepancies. For example, for sensor P1, the stress-dependent behavior of the subgrade was not taken into account (see Figures M-8a and M-8b). For sensor P7 shown in Figure M-8b, the fact that the measured pressure was lower than the predicted may be due to arching over the sensor. In summary, the finite element simulation results were in good agreement with the Large- Scale Tank test measurements for both the reinforced and unreinforced pavement structures. Considering the paving material characterization, the geosynthetic-aggregate/soil interface characterization, and the reinforcement influence zone is important to develop accurate numerical models of geosynthetic-reinforced pavement structures.
M-4 (a) Pavement Structures with 6-inch Base Course (b) Pavement Structures with 10-inch Base Course Figure M-2. Comparison of Measured and Predicted Surface Deflections for Pavement Structures with and without Geosynthetic Subjected to a 9-kip Load LVDT 1 LVDT 2 LVDT 3 LVDT 4 0.00 0.01 0.02 0.03 0.04 0.05 0.00 0.01 0.02 0.03 0.04 0.05 La rg e-S ca le Ta nk M ea su rem en ts (in ch ) FE Simulations (inch) Control Geogrid Geotextile Line of Equality ± 10 % Equality ± 20 % Equality LVDT 1 LVDT 2 LVDT 3 LVDT 4 0.00 0.01 0.02 0.03 0.04 0.05 0.00 0.01 0.02 0.03 0.04 0.05 La rg e-S ca le Ta nk M ea su re me nts (in ch ) FE Simulations (inch) Control Geogrid Geotextile Line of Equality ± 10 % Equality ± 20 % Equality
M-5 (a) Pavement Structures with 6-inch Base Course (b) Pavement Structures with 10-inch Base Course Figure M-3. Comparison of Measured and Predicted Surface Deflections for Pavement Structures with and without Geosynthetic Subjected to a 12-kip Load LVDT 1 LVDT 2 LVDT 3 LVDT 4 0.00 0.01 0.02 0.03 0.04 0.05 0.00 0.01 0.02 0.03 0.04 0.05 La rg e-S ca le Ta nk M ea su re me nts (in ch ) FE Simulations (inch) Control Geogrid Geotextile Line of Equality ± 10 % Equality ± 20 % Equality LVDT 1 LVDT 2 LVDT 3 LVDT 4 0.00 0.01 0.02 0.03 0.04 0.05 0.00 0.01 0.02 0.03 0.04 0.05 La rg e-S ca le Ta nk M ea su re me nts (in ch ) FE Simulations (inch) Control Geogrid Geotextile Line of Equality ± 10 % Equality ± 20 % Equality
M-6 (a) Pavement Structures with 6-inch Base Course (b) Pavement Structures with 10-inch Base Course Figure M-4. Comparison of Measured and Predicted Surface Deflections for Pavement Structures with and without Geosynthetic Subjected to a 16-kip Load LVDT 1 LVDT 2 LVDT 3 LVDT 4 0.00 0.01 0.02 0.03 0.04 0.05 0.00 0.01 0.02 0.03 0.04 0.05 La rg e-S ca le Ta nk M ea su re me nts (in ch ) FE Simulations (inch) Control Geogrid Geotextile Line of Equality ± 10 % Equality ± 20 % Equality LVDT 1 LVDT 2 LVDT 3 LVDT 4 0.00 0.01 0.02 0.03 0.04 0.05 0.00 0.01 0.02 0.03 0.04 0.05 La rg e-S ca le Ta nk M ea su re me nts (in ch ) FE Simulations (inch) Control Geogrid Geotextile Line of Equality ± 10 % Equality ± 20 % Equality
M-7 (a) Pavement Structures with 6-inch Base Course (b) Pavement Structures with 10-inch Base Course M-5. Comparison of Measured and Predicted Tensile Strains at the Bottom of Asphalt Concrete for Pavement Structures with and without Geosynthetic Subjected to a 9-kip Load 0 100 200 300 400 0 100 200 300 400 La reg e-S ca le Ta nk M ea su rem en ts (μ ε) FE Simulations (με) Control Geogrid Geotextile Line of Equality + 10 % Equality + 20 % Equality 0 100 200 300 400 0 100 200 300 400 La rg e-S ca le Ta nk M ea su rem en ts (μ ε) FE Simulations (με) Control Geogrid Geotextile Line of Equality + 10 % Equality + 20 % Equality
M-8 (a) Pavement Structures with 6-inch Base Course (b) Pavement Structures with 10-inch Base Course M-6. Comparison of Measured and Predicted Tensile Strains at the Bottom of Asphalt Concrete for Pavement Structures with and without Geosynthetic Subjected to a 12-kip Load 0 100 200 300 400 0 100 200 300 400 La rg e-S ca le Ta nk M ea su re me nts (μ ε) FE Simulations (με) Control Geogrid Geotextile Line of Equality + 10 % Equality + 20 % Equality 0 100 200 300 400 0 100 200 300 400 La rg e-S ca le Ta nk M ea su rem en ts (μ ε) FE Simulations (με) Control Geogrid Geotextile Line of Equality + 10 % Equality + 20 % Equality
M-9 (a) Pavement Structures with 6-inch Base Course (b) Pavement Structures with 10-inch Base Course M-7. Comparison of Measured and Predicted Tensile Strains at the Bottom of Asphalt Concrete for Pavement Structures with and without Geosynthetic Subjected to a 16-kip Load 0 100 200 300 400 0 100 200 300 400 La rg e-S ca le Ta nk M ea su re me nts (μ ε) FE Simulations (με) Control Geogrid Geotextile Line of Equality + 10 % Equality + 20 % Equality 0 100 200 300 400 0 100 200 300 400 La rg e-S ca le Ta nk M ea su rem en ts (μ ε) FE Simulations (με) Control Geogrid Geotextile Line of Equality + 10 % Equality + 20 % Equality
M-10 (a) Pavement Structures with 6-inch Base Course (b) Pavement Structures with 10-inch Base Course M-8. Comparison of Measured and Predicted Vertical Stresses within the Base and Subgrade for Pavement Structures with and without Geosynthetic Subjected to a 9-kip Load P5 P3 P2 P1 P4 0 5 10 15 20 25 30 35 0 5 10 15 20 25 30 35La rg e-S ca le Ta nk M ea su rem en ts (ps i) FE Simulations (psi) Control Geogrid Geotextile Line of Equality ± 10 % Equality ± 20 % Equality P7 P4 P6 P3 P2P5 P1 P7 0 5 10 15 20 25 30 35 0 5 10 15 20 25 30 35La rg e-S ca le Ta nk M ea su re me nts (ps i) FE Simulations (psi) Control Geogrid Geotextile Line of Equality ± 10 % Equality ± 20 % Equality
M-11 (a) Pavement Structures with 6-inch Base Course (b) Pavement Structures with 10-inch Base Course M-9. Comparison of Measured and Predicted Vertical Stresses within the Base and Subgrade for Pavement Structures with and without Geosynthetic Subjected to a 12-kip Load P5 P3 P2 P1 P4 0 5 10 15 20 25 30 35 0 5 10 15 20 25 30 35 La rg e-S ca le Ta nk M ea su re me nts (μ ε) FE Simulations (με) Control Geogrid Geotextile Line of Equality ± 10 % Equality ± 20 % Equality P7 P4 P6 P3 P2 P5 P1 P7 0 5 10 15 20 25 30 35 0 5 10 15 20 25 30 35 La rg e-S ca le Ta nk M ea su rem en ts (μ ε) FE Simulations (με) Control Geogrid Geotextile Line of Equality ± 10 % Equality ± 20 % Equality
M-12 (a) Pavement Structures with 6-inch Base Course (b) Pavement Structures with 10-inch Base Course M-10. Comparison of Measured and Predicted Vertical Stresses within the Base and Subgrade for Pavement Structures with and without Geosynthetic Subjected to a 16-kip Load P5 P3 P2 P1 P4 0 5 10 15 20 25 30 35 0 5 10 15 20 25 30 35 La rg e-S ca le Ta nk M ea su re me nts (μ ε) FE Simulations (με) Control Geogrid Geotextile Line of Equality ± 10 % Equality ± 20 % Equality P7 P4 P6 P3 P2 P5 P1 P7 0 5 10 15 20 25 30 35 0 5 10 15 20 25 30 35 La rg e-S ca le Ta nk M ea su rem en ts (μ ε) FE Simulations (με) Control Geogrid Geotextile Line of Equality ± 10 % Equality ± 20 % Equality
