| At present,with the massive construction of underground spaces and roads in our country,more and more shallow buried tunnels have emerged.Such projects are generally characterized by shallow buried depth and poor surrounding rock grades.Seismic observations found that the actual earthquakes have a "gradual increase" in magnitude from small to large,that is,they are generated in the form of "seismic sequence".A large number of academic studies and engineering earthquake damage examples show that the seismic performance of the shallow buried soft rock tunnel project is relatively poor,and its seismic dynamic response is closely related to the spectral characteristics of the input seismic waves.Starting from the economic cost of the test and the ease of implementation,the shaking table model test is still the main tool for studying the seismic performance of tunnels and other underground projects.In the shaking table model test of the tunnel,the sensor can be used to obtain the acceleration signal of the surrounding rock vibration of the tunnel under earthquake.This signal is an important parameter that directly reflects the severity of the seismic response of the tunnel and evaluates its seismic performance.However,at present,the processing and analysis methods for the acceleration signals of the surrounding rocks of the tunnel are relatively simple,and the signal processing related technologies can realize the functions of signal noise filtering,time-frequency characteristic analysis,and peak finding.Therefore,it will be of great theoretical significance and practical application value to realize the comprehensive analysis of the surrounding rock acceleration signal for the system to reveal the tunnel seismic dynamic response,if we put signal processing related technologies into the shaking table model test of tunnel.In this paper,based on the operation of the distribution tunnel project at the cluster line station of Chengdu Metro Line 10,we carried out the shaking table test of the shallow buried soft rock tunnel model.The collected model stratum’s vibration acceleration signal was used as the analysis object,and the related technology of signal processing was used as a means of analysis,to study the propagation characteristics of ground motions in shallow soft rock tunnel sites and the dynamic response characteristics of model strata under the conditions of multiple successive loadings of different types of seismic waves.The main research contents and results are as follows:(1)Relying on the wiring tunnel of the Tujin Station of the Chengdu Metro Line 10,a shaking table test of a shallow buried soil tunnel model under progressive earthquake loads was carried out to describe and analyze the phenomena and causes of tunnel damage,respectively.At the same time,the acceleration response signal of the surrounding rock of the tunnel during the vibration process was obtained by using the acceleration sensor.(2)With reference to other research results,a wavelet threshold filtering method was selected,and a specific filtering scheme was clarified.Filtering operations were performed on the collected original surrounding rock acceleration signals,and the differences in time-frequency characteristics between the two before and after signal filtering were compared.(3)The wavelet packet frequency domain multi-level decomposition technique is used to perform three-level and eight-band decomposition of the filtered acceleration signal.The frequency bands of the acceleration signals under different types of input seismic waves,different surrounding rock positions,and different input seismic wave amplitude conditions are compared and analyzed.The change of energy reflects the seismic dynamic response of the surrounding rock of the tunnel.(4)Using the Fourier spectrum frequency domain integral value of the signal under the sine wave sweep frequency before and after the input seismic wave is loaded,in the Fourier spectrum frequency domain globally(0-50Hz)and in the frequency domain local frequency bands(0-i Hz,i is 1-10)within the scope,the dynamic impacts of different types and acceleration amplitude input seismic waves on the surrounding rock of tunnels at different locations are analyzed,and the dynamic impacts are quantified.(5)Define a new parameter of "improved acceleration amplification factor",that is,MAAF(Modified Acceleration Amplification Factor),based on this parameter,from four angles of different types of input seismic waves,different locations of tunnel surrounding rocks,different input seismic wave acceleration amplitudes and signal filtering.The seismic dynamic response characteristics of the surrounding rock of the tunnel are studied.The relevant research results can reflect the "multi-peak" characteristics of the vibration signal itself and the actual situation of the "cyclic peak load" of the surrounding rock and soil under seismic loads to a certain extent.The dynamic response characteristics of shallow buried soft rock tunnel under different types of seismic waves is studied and analyzed by using signal processing related technologies in this paper,and related research results are hoped to provide useful reference for the same type of research. |
PDF Full Text Request