MEMS accelerometers for measuring dynamic penetration events in geotechnical centrifuge tests

Abstract

Micro-electro mechanical system (MEMS) accelerometers are small, inexpensive sensors that have only recently been used in geotechnical centrifuge tests. This is unlike piezoelectric accelerometers, which are by comparison large and expensive but have been used extensively in geotechnical centrifuge tests over the past couple of decades. This paper examines the response of a single-axis ±500g MEMS accelerometer under both static and dynamic conditions in a centrifuge environment. The potential for MEMS accelerometers to be used to measure the depth of objects buried in soil is examined and the achievable resolution is discussed. Unlike piezoelectric accelerometers, which only measure changes in acceleration, MEMS accelerometers can measure both constant and changing accelerations. The merit of this feature is demonstrated through tests in which MEMS and piezoelectric accelerometers are embedded within a dynamically installed model anchor. The MEMS accelerometer is capable of measuring accelerations during both the free-fall phase and the soil embedment phase, whereas the piezoelectric accelerometer is only able to measure the changing accelerations that dominate during the soil embedment phase. Velocity profiles derived from numerical integration of the MEMS accelerations give mudline anchor velocities that agree with independent measurements and anchor embedment depths that agree with direct measurements.