Comparison of impact hammer and maximum length sequence method to measure vibration transfer functions in soils

摘要

Before construction of new train, subway, tramway lines near existing buildings or in case of new buildings construction near existing lines, operators and local authorities have to predict vibration levels generated in buildings. Therefore, vibrations levels have to be evaluated at every step of propagation path. For evaluation of soil vibration transfer functions, different methods based on impulsive sources or on electrodynamics shakers can be used. The goal of this paper is to test the validity of Maximum Length Sequence (MLS) method to evaluate vibration level differences between different accelerometers by comparison with impact hammer method, and identify key parameters that improves results. Main aspects of signal processing associated with both MLS and impact hammer method, type of device used to produce vibration and main characteristics of Impulse Response (IR) are presented. A comparison of mitigation measured by MLS method (for fixed parameters) and impact hammer method is given. After that, a parametric study is performed on each MLS key parameter. Finally, a variation of soil properties after twenty days is given.