Measure,Simulation And Annoyance Degree Evaluation Of Vibration Effects Of Underground Space Adjoining Subway Station

In recent years,as a result of the rapid development of the urban rail transit,the subway train-induced ambient vibration is being gradually concerned.In this paper,a specific wireless sensor network system is developed for fast assessment of subway train-induced vibrations.Then the system was applied to the field test at an underground space adjoing Xinghai Square subway station of Suzhou.Based on the finit element method,the numerical simulation and analysis is also implemented for the vibration reponses of the underground space.The combined annoyance degree model is developed to quantitatively evaluate the comfort of the people in the vibration environment.The main results and conclusions are as follows(1)The specific wireless sensor network system is developed for the fast quantitative assessment of subway train induced ambient acceleration;the system is based on Intel Imote2 wireless sensor network platform,combining the high-precision acceleration sensor board SHM-H with the embedded software platform ISHMP Services Toolsuite.Based on the open-source operation system TinyOS,we use component structural programming language nesC to program the embedded application for vibration signal preprocessing,so as to embeddedly compute the ambient vibration level,which may greatly improving the work efficiency.(2)By analyzing the measured data,it is discovered that the peak values of the vibration acceleration gradually decrease with the increase of the distance.The maximum acceleration of the measure point nearby the testing area is about 120 mm/s2;while the minimum acceleration reduces to 20 mm/s2 or less at the distance of 40m on the farthest end of the measured line.The vibration of the frequency band below 40 Hz is weak,and the change of vibration amplitude is unconspicuous.The peak value at 1.64 Hz can be inferred to be the fundamental frequency of the floor slab.Within the frequency band from 40Hz to 80 Hz,the vibration amplitude varies intricately,and the dominant frequency mainly focuses on the band from 60 to 70 Hz,in which the vibration amplitudes decrease obviously with the distance extension,namely form 50 mm/s2 down to less than 10 mm/s2.Moreover,the vibration levels on the central frequency of 63 Hz approach to 70 dB at some measure points near subway tracks,which may cause annoyance and other negative influence on human body.Using the second-order Fourier functions,the trends of the vibration levels with the distance variation of all the measure lines are fitted.Basically,the trend is that the high frequency compents attenuate rapidly and the low frequency compents attenuate slowly,with the peaks shifting from the high frequency to the low frequency.Comparing with the limits in the environmental vibration evaluation standards,it is implied that the structural safety is influence little by the the subway train-induced vibration,but the human comfort may be affected obviously.(3)Using PLAXIS 2D finite element software and combining two dynamic load simulation methods,the structural dynamic reponses of the practical scenario are calculated.The simulation results agree well with test ones,suggesting the soundness of the numerical models.The orthogonal experiment method is used for the parameter analysis of the vibration reponses of the underground structure.The investigation results show that the structural reponses are positive correlate to the train load.But the reponse does not simply enhance with the train speed increase.Initially,the reponse increases rapidly with the increase of the speed until the maixal reponse occur at the speed of 12 m/s.Then,the reponse drops slowly with the increase of the train speed As for the reponse with the distance,it attenuates sharply with the 20 m distance to the train track,then tend to be flat with the increase of the distance.Response amplification occurs at the distance of 20 m when the damping ratio of the underlying soil layer is greater than 0.2.Besides,structural vibration intensity does not show correlation with the unit weight,cohesive force,internal frictional angle and the poission’s ratio of the underlying soil layer.(4)A fuzzy membership function and normal distribution function were coupled to describe the fuzziness and randomness of human annoyance responses;a combined annoyance degree model was proposed to assess the building vibration and its secondary structure-borne noise;and the human annoyance was classified into six grades.Subsequently,using field test data,we calculated and analyzed the combined annoyance degree of an underground structure adjacent Xinghai Square subway station.The results of combined annoyance degree were compared with the JGJ/T170-2009 standard,in which the rationality and superiority of the proposed model was verified.The results also show that the proposed models can serve as a reference for spatial planning and development in the region researched.