The Damage Identification Method Of Shield Tunnel Based On Wavelet Packet Energy Spectrum

As an important part of urban rail transit,the construction and operation of the tunnel become particularly important.The environment of underground tunnel is complex.With the growth of service time,local damage will inevitably occur.It will leave behind different kinds of security threat and finally lead to paralysis of the urban traffic system without daily regulation.Thus health monitoring and damage detection of metro shield tunnel also became an important issue.A damage location method of shield tunnel is proposed based on distributed identification strategy.It is suitable to adopt this method as the shield tunnel is an overlong and liner civil engineering structure.And it is subjected to stable metro train load,thus the acceleration response will be stable.The method is verified by a scaled shield tunnel model and a full-scale tunnel numerical simulation analysis.The specific research work is shown as follows:1.Simulated and experimental studies are used to verify the damage of a scaled shield tunnel.A damage detection method based wavelet packet energy is used to analysis the dynamic response signals.The results demonstrate that the proposed method have a good performance on damage identification.2.A full-scale finite element analysis model of shield tunnel is built by ABAQUS software.Damage is simulated by changing the elasticity modulus of the shield model and then the acceleration corresponding signal of shield tunnel finite element model bearing the train moving load is collected.The influence of the parameters of the wavelet packet and the change of the moving load on the damage index is also studied.The results show that the proposed damage index is valid and very sensitive to detect different damage conditions.And the results are less affected by different wavelet packet parameters and load changes.Only the increase of wavelet packet decomposition level will largely affect computing efficiency.3.A distributed recognition strategy based on mutual information for super long shield tunnel structure is proposed.The shield tunnel is first divided into linear substructure,then the proposed method is demonstrated on damage detection test cases.The results show that this strategy can identify damage successfully,and decrease the number of measurement points at the same time.Compared to normal recognition method,the proposed method is more efficient.