Field installation details of a wireless shape-acceleration array system for geotechnical applications

The evaluation, health monitoring and response prediction of soil and soil-structure systems during construction and due to extreme hazard conditions are on the verge of a significant paradigm shift. New and less expensive sensing technologies have enabled the development of innovative instrumentation and advanced interactive modeling tools. These tools, combined with recent advances in information technology including wireless sensor networking, data mining, visualization and system identification, promise significant improvements in real time monitoring during construction, sensor-assisted design and early warning of impending failure. This paper presents the newly developed Wireless Shape-Acceleration Array (WSAA) sensor that measures multi-dimensional acceleration and deformation profiles and constitutes a major step toward autonomous monitoring technology for soil and soil-structure systems. The Wireless Shape-Acceleration Array (WSAA) sensor employs micro-machined electromechanical sensors (MEMS), which have enabled gravity-based shape calculation along a sensorized substrate. The method is an extension of technologies that use fiber optic orientation sensing to calculate 3D polylines representing the shape of a sensor array. WSAA uses MEMS accelerometers in a pre-calibrated, geometrically constrained array to provide long-term stability previously unattainable with fiber optic methods. This sensor array is capable of measuring 2D soil acceleration and 3D permanent ground deformations to a depth of one hundred meters. Each sensor array is connected to a wireless earth station to enable real time monitoring of a wide range of soil and soil-structure systems as well as remote sensor configuration. This paper presents the evolving design of this new sensor array as well as lessons learned from two field installations of this sensor.