| Popis: |
In an effort to quantify the contribution of geotextile separators to the long -term performance of pavement sections, falling weight deflectometer (FWD) testing was carried out over a 12-year period at a test section in southwest Washington State. Five different geotextile separators as well as a soil -only control section were installed in the test sec tion with a different base course thickness in the two lanes of a low volume but heavily loaded rural state highway. The performance of the separators was evaluated during construction and 5 and 12 years after construction. Field and laboratory tests wer e conducted on the subgrade, granular base materials, and the geotextiles as part of the effort to correlate the performance of the pavement section to the presence of the geotextile separators. As part of the most recent evaluation, the FWD results were analyzed using two recently developed interpretation methods, the FWD Area Program (version 2.0) and Evercalc Pavement Backcalculation Program (version 5.20). The results from the FWD Area Program generally showed a decrease in the adjusted deflections, and increases in the area parameter and subgrade modulus along the test section over the 12-year period. The greatest increase in subgrade modulus occurred in the six months following construction. The control sections exhibited behavior similar to the sections with geotextiles, suggesting that for relatively thick pavements, geotextiles separators may not provide a significant contribution to the long -term performance of the pavement. The Evercalc backcalculations indicated an increase in the adjusted pa vement and subgrade moduli over the 12-year period. The sections that contained geotextiles generally showed an increase in the base course modulus, however, some of the analyses showed little to no increase in the base modulus in the control (soil only) sections. The results suggest that geotextiles might contribute to an increase in the base course modulus over time. These findings were also correlated with the results of the field and laboratory investigations. |
