The Research And Application On Fluctuating Response Properties Of Microseism For The Site Around Structures

Microtremor is transmitted through the site soil to structures and causes the structures continuous microseism.Meanwhile,the microseism of the structures acts as a new microtremor source transmitted into the surrounding site in turn,and affects the wave motion of the free field.Due to the complexity,intensity and height of city structures,the structures are likely to produce more intense microseism to affect the wave motion of the free field with greater range and intensity.When microseism tests for the site around structures are carried out,the records of test are likely to contain the microseism information,and this will be showed in the processed spectrum diagram to affect the engineers and scholars making accurate evaluations for the free field.Moreover,the accuracy of test results applied to the foundation soil classification,seismic performances evaluation of the structures,the seismic microzonation,and so on,will be decreased.Therefore,it is necessary to carry out the researches on fluctuating response properties of microseism for the site around the structures.In this dissertation,the formation parameters of the sites and the dynamic properties of the structures are studied.On the basis,a response model of the surrounding site is established that the source is from the microseism of the structures,and the reliability of the model is verified by practice.The main research contents including:On the basis of previous researches,this dissertation discusses the basic principle of the microseism observation and data processing,and analyzes the mechanism of observed signals.According to the distribution of strata in engineering exploration,different geological parameters models are established,and the influences regularity of H/V spectrum characteristics for the different formation parameters density,shear wave velocity,compressional wave velocity and thickness is studied by using Model HVSR simulation software.And the optimization process of formation parameters is discussed in detail so as to provide reliable geological model parameters for the mechanism researches and practical applications of microseism.The principle of dynamic characteristic tests and data processing methods for the structures are discussed.Single-storey and multi-storey structures on the soft soil foundation is selected as the research object,and the pulsating method is applied to test.The methods of FFT,SSR,HVSR and NonPaDAn are used to process and interpret the data.The reliability of different analytical methods is analyzed,and the natural vibration period and damping of structures are studied in order to provide reliable dynamic characteristics parameters for the mechanism research and practical application of microseism.A piece of software used to simulate the excitation of vibration source is developed to obtain the excitation function by the Matlab software,and then the excitation function will be applied to the two-dimensional microseism propagation model which is established by Fortran software.Then,the software is used to get the final analytical results of microseism for the site around the structures.Finally,the structures on weak clays and hard clays are selected as research objects,and a large number of microseism data of the structures and free field is collected to analyze and verify the response model.Some reasonable suggestions are put forward for microseism testing in the site around the structures through the comparison between simulation results and measured results.