Pavement Failure Publications

Design Life

Accelerated Pavement Testing of Geocell-Reinforced Bases Over Weak Subgrade

Han, J., Pokharel, S.K., Manandhar, C., Yang, X.M., Leshchinsky, D., Halahmi, I., Parsons, R.L.

Journal of the Transportation Research Board

To evaluate the effect of geocell reinforcement on base courses for low-volume unpaved roads over weak subgrade, full-scale trafficking tests were conduced using the accelerated pavement testing facility at Kansas State University. Three different types of infill materials including AB3 aggregate, quarry waste (QW), and Recycled Asphalt Pavement (RAP) were used for the base courses and A-7-6 clay was used as the subgrade. Four unpaved sections that included one unreinforced control section of 30 cm thick AB3 aggregate and other three 15 cm polymeric alloy geocell-reinforced sections with 2cm cover were tested under the single-axle dual tire wheel loading. The benefits of alloy geocell reinforcement are evaluated in terms of rut depths at a number of passes of the wheel load and the angle of stress distribution from the surface to the base course-subgrade interface. The test results demonstrated that the alloy geocell reinforcement improved the performance of unpaved AB3 and RAP sections in terms of rut depth and angle of stress distribution compared to the unreinforced section. The QW section also showed better performance in terms of stress distribution angle. The road sections were exhumed and evaluated after the moving wheel test. 

A Summary of Research on Geocell-Reinforced Basecourses

Han, J., Thakur, J.K., Poharel, S.K., Yang, X.,
Parsons, R.L.
Geosynthetics-Reinforced Soil Structures

Geosynthetics have been widely used as construction materials for soil reinforcement since 1970s. In the past, most of the research on subgrade improvement and base reinforcement has been focused on planar geosynthtics, such as geogrid and woven geotextile. However, limited research has been done on three-dimensional geocell reinforcement of base courses. A series of static and cyclic plate loading tests, full-scale moving wheel tests, and numerical modeling were conducted by the research team at the University of Kansas on geocellreinforced base courses with different infill materials (Kansas River sand, quarry waste, well-graded aggregate, and recycled asphalt pavement). This paper summarizes the main research findings from these studies addressing permanent, elastic, and creep deformations, stiffness, bearing capacity, and stress distribution, development of design methods for geocell-reinforced bases. These studies showed that geocell-reinforced base courses reduced the vertical stresses at the interface between subgrade and base course, reduced permanent and creep deformations, increased elastic deformation, stiffness, and bearing capacity of base courses.

Determination of Resilient Modulus of Subgrade using a Cyclic Plate Loading Test

Qian, Y., Han, J., Poharel, S.K.,
Parsons, R.L.
Proceedings of GeoFrontiers

Resilient modulus of subgrade is often necessary for pavement design and determined by cyclic triaxial tests or correlation with other laboratory or insitu test results (such as CBR and DCP data). Cyclic plate loading tests were conducted in this study to determine the resilient modulus of a weak subgrade. The weak subgrade was made of 75% Kansas River sand and 25% kaolin and compacted at wet of optimum in a large geotechnical testing box (2m x 2.2m x 2m). This subgrade was first evaluated by DCP tests and then tested under a 30-cm diameter rigid plate at four different magnitudes of cyclic loading. During the tests, the deformations of the plate and the subgrade surface were monitored. The test results showed that the plate deformation increased with the number of cycles. An elastic solution was used based on the rebound deformation of the plate to calculate the resilient modulus of the subgrade. The calculated resilient modulus of the subgrade decreased and approached a stable value with the number of cycles under different magnitudes of cyclic loading. The calculated resilient modulus from the cyclic plate loading tests was compared with that determined based on the correlation with the CBR value of the subgrade.

Accelerated Pavement Testing of Unpaved Roads with Geocell-Reinforced Sand Bases

Yang, X., Han, J., Poharel, S.K., Manandhar, C.,
Parsons, R.L., Leshchinsky, D., Halahmi, I.
TRB 90th Annual Meeting

Accelerated pavement testing (APT) is an effective method in evaluating pavement performances by applying controlled wheel loading under environmental conditions. This note presents the findings from an accelerated pavement test on unpaved road sections involving geocell reinforcement of sand bases. A total of four unpaved road sections were constructed. Sections 1 and 4 were unreinforced sections first with sand bases and then replaced with aggregate bases after failure. Sections 2 and 3 were sand sections reinforced with novel polymeric alloy (NPA) geocell under an aggregate cover layer. Rut depths developed in each section were measured after a certain number of wheel passes. Horizontal strains at different locations in the NPA geocell were monitored by strain gages. Test results demonstrated that the NPA geocell had a significant effect in improving the stability of unpaved roads and reducing the permanent deformation. Under the particular test condition, the NPA geocell-reinforced sand layer behaved equivalently to the A-1-a aggregate of the same thickness. The deformations of the geocell-reinforced road sections were analyzed. The test also revealed the importance of keeping the geocell structure intact to ensure the adequate performance of NPA geocell-reinforced bases. Strain gage measurements showed that the NPA geocell beneath the wheel path experienced tensile stresses whereas the geocell outside the wheel path experienced compressive stresses.

Effect of Infill Material on the Performance of Geocell-Reinforced Bases

Han, J., Pokharel, S.K.,
Parsons, R.L., Leshchinsky, D., Halahmi, I.
Proceedings of the 9th International Conference on Geosynthetics

Geocell, due to its three-dimensional structure, can effectively provide lateral confinement to
infill material to increase the stiffness and bearing capacity of base courses and to reduce their permanent deformations under repeated loading. However, limited studies have so far been done to investigate the effect
of infill material on the performance of geocell-reinforced bases. In this study, three different infill materials,
poorly-graded Kansas River sand, quarry waste (QW), and well-graded AB-3 aggregate, were used. The performance of different infill materials in terms of bearing capacity, stiffness, permanent deformation, and percentage elastic deformation of the geocell-reinforced bases was studied in the experiment study. The test results show that the benefit of the geocell in the bearing capacity and stiffness of the reinforced base under
static loading was more evident when a weaker infill material was used. However, the benefit of stronger infill materials became more evident under repeated loading. Under the same magnitude of repeated loading,
permanent deformations of reinforced bases were significantly reduced and the percent of elastic deformations were significantly increased for all infill materials as compared with those of unreinforced bases