Use of mems accelerometers/inclinometers as a geotechnical monitoring method for ground subsidence

Abstract

Accelerometer and inclinometer are inertial sensors capable of measuring corresponding magnitude of Earth gravitational field along the direction of each axis. By means of rotation matrices related to inertial navigation methods, the output values of a three-dimensional accelerometer or a two-dimensional inclinometer can be transformed and processed into the azimuth and dip angle of the monitored target. With the rapid growth in development and cost reduction of Micro Electro Mechanical Systems (MEMS) and Wireless Sensor Network (WSN) in recent years, the engineers are able to carry out real-time wireless geotechnical monitoring during construction. In this paper, we set up a one-day measurement implemented by a self-developed wireless MEMS monitoring system on the surface in the construction site of South Hongmei Road super high way tunnel in Shanghai, by making use of rotation matrices in specific ways, the raw data are processed to expressions of three-dimensional normal vectors that represent the change of the ground. After unifying the vectors in the same coordinate system, we conduct a brief ground settlement analysis by means of an evaluation of the dip angles in the cross section and the azimuths of the sensor nodes.