| dc.description.abstract | The transportation agencies must allocate a significant annual budget to rehabilitate low to high volume roads constructed over expansive subgrades. This type of subgrade soil undergoes substantial changes in volume due to the seasonal fluctuation of moisture levels, which will lead to pavement distress, including rutting, heaving, or/and longitudinal cracking. On the other hand, utilizing the large volume of reclaimed asphalt pavement (RAP) aggregates as a part of the pavement base layer has been a big challenge for researchers due to its poor mechanical properties. The traditional subgrade treatment procedures with full-depth reclamation are cost-intensive and time-consuming. Therefore, the transportation industry looks for an economical and sustainable alternative to address both these issues. This research study aims to assess the potential benefits of a three-dimensional confinement system, commercially known as “geocell,” to improve the performance of RAP materials and provide consistent support to the flexible pavement structure constructed over expansive subgrades.
This dissertation focused on contributing to the field of pavement geotechnics in two ways: first, to evaluate the performance of the geocell reinforced RAP-base (GRRB) layers to improve the performance of the flexible pavement constructed over expansive subgrade soil; and second, to develop a design methodology for such pavements based on field observations, cost and sustainability assessments.
Several test sections were constructed over an existing farm-to-market road, FM 1807, which suffered from distresses induced by the underlying expansive subgrade. These test sections were designed and constructed with different geocell-RAP infill materials, instrumented with sensors including Shape Array Accelerometers (SAAs) and Earth Pressure Cells. The structural capacities of the pavement sections were further evaluated by performing nondestructive field tests, including Falling Weight Deflectometer (FWD) and Automated Plate Load Test (APLT).
In addition to the field testing, numerical modeling analyses were performed to understand the contributions from the geocell bases and determine the future load-carrying capacity based on compressive strain acting on the subgrade soil. The expected design life of the geocell-reinforced pavement was calibrated with the field monitored data, and these results are used to develop flexible pavement design on expansive soils by utilizing a GRRB layer. The economic and sustainability aspects of flexible pavements with GRRBs are further verified with Life-Cycle Cost Analysis (LCCA) and sustainability analysis. It is believed that this research study will provide future practical guidelines for the construction and design of flexible pavements with GRRBs over expansive subgrades. | |
