Wireless real time monitoring of soil and soil-structure systems

This paper presents the newly developed Wireless Shape-Acceleration Array (WSAA) sensor that measures 2D acceleration and deformation profiles. This sensor system 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 2D permanent ground deformations, in the horizontal plane, 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 close comparisons between the WSAA system and traditional instrumentation utilized in full scale laboratory tests at the National Research Institute for Earth Science and Disaster Prevention (NIED, Japan). The goal of validating and calibrating the measured accelerations and displacements of the WSAA system was achieved through these full scale tests.