Instrumentation and Monitoring of an MSE/Soil Nail Hybrid Retaining Wall

MSE/soil nail hybrid earth retaining walls provide a more economical design for applications in cut/fill situations than the traditionally used full height MSE and drilled shaft retaining walls. MSE/soil nail hybrid earth retaining walls use a soil nailed wall in the cut section and an MSE wall in the fill section. In spite of the significant cost savings they offer, hybrid walls have not seen widespread use primarily because of lack of understanding on wall design and performance. This paper describes an instrumentation and monitoring effort that was undertaken with the objective of improving our understanding of hybrid wall design and performance. In this project, two separate panels of a hybrid wall constructed in San Antonio, Texas were selected for instrumentation and monitoring. The first wall panel consisted of a 4.0m soil nail wall and a 5.4m MSE wall while the second wall panel consisted of 5.0m soil nail wall and a 4.4m MSE Wall. The instrumentation scheme for the wall included vibrating wire strain gages, vertical inclinometers, horizontal inclinometers, and tiltmeters. The data collected from these two instrumented wall sections provide valuable insight to the mechanisms controlling the performance of MSE/Soil Nail Hybrid Wall systems.