Doctor of Philosophy (PhD)


Civil and Environmental Engineering

Document Type



Weak soil is a common problem in road construction. Whether it is a temporary access road or a permanent road built over a weak subgrade, a large deformation of the subgrade can lead to deterioration of the paved or unpaved surface. Geosynthetics offer a potentially economical solution for stabilizing roads built over weak soil. Three sets of testing programs were be conducted in this study.The first testing program includes conducting accelerated load testing of full-scale geosynthetic reinforced test lanes using rolling wheel load facility; the second program included conducting laboratory cyclic plate loading test on geosynthetic reinforced test sections constructed inside a steel box facility, and the third program included cyclic plate loading test on full-scale test lane sections. An extensive in-situ and laboratory testing was performed before the construction of the test sections and after each stage of pavement construction to assess the strength, stiffness of the pavement layers. Both the full-scale pavement test lane sections and in-box laboratory pavement test sections were instrumented with several sensors to measure the load associated and associated environmental responses. The experimental test results demonstrated that the inclusion of geosynthetics in pavement to reinforce the base and or stabilize the subgrade can significantly enhance the pavement performance in terms of reducing the permanent deformation of pavement layers. The inclusion of geosynthetics in pavement can help redistribute the load and change the stress concentration on top of subgrade layer. The benefits of geosynthetic reinforcement were quantified, within the context of the AASHTOWare Pavement ME Design guide and AASHTO 1993, in terms of increasing the resilient modulus of base course layer and/or reducing the thickness of base aggregate layer in pavement structure.The results for three test experiments showed an increase in traffic benefit ratio when including geosynthetic in pavement.Also, include geosynthetic showed appreciable benefit on reducing the permanent deformation of base layer subgrade in this study. Four empirical models were developed by using nonlinear regression to evaluate and quantify the benefits of using geosynthetics in pavement built over weak subgrade. The first model was developed to quantify the traffic benefit ratio (TBR). The second model was developed to quantify the base course reduction(BCR). The third model was developed to quantify the resilient modulus increase by using the geosynthetics to reinforce the base layer. The fourth model was developed to quantify the increase in resilient modulus by using the geosynthetics to stabilize the subgrade.Furthermore, The developed models were verified with experimental data to predict the amount of each model.



Document Availability at the Time of Submission

Secure the entire work for patent and/or proprietary purposes for a period of one year. Student has submitted appropriate documentation which states: During this period the copyright owner also agrees not to exercise her/his ownership rights, including public use in works, without prior authorization from LSU. At the end of the one year period, either we or LSU may request an automatic extension for one additional year. At the end of the one year secure period (or its extension, if such is requested), the work will be released for access worldwide.

Committee Chair

Abu-Farsakh, Murad