Influence of excitations originating from moving subway onto transferring vibrations from ground to structure

Abstract

In the majority of these influences parameters describing them are known. Nevertheless, in case of vibration it is not always simple to determine their parameters, especially when the source is located outside. The paper presents problems associated with the building loads generating by the subway passages. Subway train moving in a tunnel, through the layout of the track, transfers energy to the housing tunnel, then to the ground which then propagates in the ground layers to the building. This causes movement of foundations generating kinematic excitation for the entire facility. Generally way of propagation of vibration is complex. During designing new facility, it is possible - at its future location – to measure vibration level of existing sources on the ground. Soil movements in the vicinity of the foundation of the house are not the same - they are quite often very different from each other. This is related to wave transitions through the border between the different soil layers. Therefore there is a need to determine the transfer function between the vibrations registered on the soil and potential real construction loadings. Such analysis were made for an existing building with six floors loaded with excitations caused by movement of the subway in a nearby tunnel. According to Polish Standard [1] PN-85/B-02170 (“Hazard rating of vibrations transmitted through the ground to the buildings”) only vibrations with frequency up to 100Hz in terce octave bands (1/3 octave) were considered. As is apparent from the analysis the global amplitude value of vibrations registered on the ground is several times less than on the foundation of the building. However, in particular one-third octave bands (up to several Hz) it may happen that the accelerationv ibration of the foundation is higher than on the surrounding terrain. Increased amplitudes may be important in the effort analysis of structure cross-sections as well as the effects of vibrations on people staying inside. The issue of loading building with vibrations caused by the movement of subway should take into account an analysis of the nature of amplitude-frequency at the interface soil-foundation.