REAL-TIME MONITORING FOR GEOSYNTHETIC REINFORCED SYSTEMS

Real-time monitoring of civil infrastructure provides valuable information to assess the health and condition of geotechnical systems. This paper presents the recently developed Shape Acceleration Array (SAA), which constitutes a major step toward long-term effective health monitoring and analysis of soil and soil-structure systems. The sensor array is based on triaxial MEMS (Micro-Electro-Mechanical System) sensors to measure in situ deformation (angles relative to gravity) and dynamic accelerations up to a depth of one hundred meters. This paper provides an assessment of this array’s performance in two field installations; within a plantable geosynthetic reinforced (PGR) retaining wall and a bridge replacement site. The PGR wall, with a 6V:1H battered wall face, is about 2.4 km (1.5 mile) long. The wall height varies from 7 m (23 ft) to about 21.8 m (71.5 ft), with an average wall height of about 16 m (52.5 ft). This wall is the first of its kind, with a state-of-the-art concrete facing design. Thus, in order to fully capture the response of this design to seismic activity and other vibrations, the wall was heavily instrumented with accelerometers, piezometers, and in-place inclinometers. The instrumentation plan for the bridge replacement site included the use of two SAA systems, oriented vertically and horizontally, to monitor the lateral deformation and consolidation settlement, respectively, of a 30 m (98 ft) soft soil deposit beneath geosynthetic embankment surcharge. The comprehensive site instrumentation included traditional inclinometers, piezometers, and settlement gages. The geosynthetic embankment surcharge fill is used as an applied vertical stress (preload), prior to completion of the final permanent construction load. The paper will present data recorded with the developed in-place inclinometer-accelerometer system (SAA) and compared data measured with state-of-the-practice instrumentation. These comparisons were extremely favorable and justified the future use of this instrumentation for many geotechnical applications.