Evaluation of interaction properties of geosynthetics in cohesive soils : LTRC reinforced-soil test wall.

State Project No. 736-99-0658
This report presents the construction and performance evaluation of the LTRC reinforced-soil test wall. The 20 ft. high, 160 ft. long wall was constructed using low quality backfill. Its vertical front facing was constructed with modular blocks. It consisted of three sections reinforced with various geogrid reinforcement types and spacing. The backside of the wall was a one-to-one slope reinforced with woven and non-woven geotextiles.
The test wall was constructed to evaluate the design procedure and performance of geosynthetic-reinforced structures constructed with marginal silty-clay backfill over soft clay foundation. The instrumentation program consisted of monitoring wall deformation, foundation settlement, strains in the reinforcement, vertical and horizontal stresses in the soil, and pore water pressure under the wall. Results of the monitoring program from construction through four months after completion of the wall are detailed in this report.
The results of the instrumentation program showed relatively high deformations due to both the design of the wall with low factors of safety and to the high settlement of the foundation soil. These deformations, however, occurred mostly during construction. The results of strain measurements in the reinforcement were used to evaluate the effect of reinforcement stiffness and spacing on the shape of the failure surface and on the distribution and magnitude of stresses in reinforcement layers.
The results show promising performance of silty-clay soils as a backfill material in reinforced-soil walls providing proper design and control of soil compaction and moisture. However, long-term performance of the wall needs to be monitored for a complete evaluation of these types of walls.