Experimental Study On Shaking Table Of Shallow Tunnel Via Digital Image Correlation Technology

In recent years,a large number of shallow-buried tunnels emerge in practical projects,especially in the construction of subway.China has been suffering from the earthquake.The earthquake damage of many tunnels shows that the seismic response of shallow tunnel is remarkable,and it is easy to lose stability and destroy in soft surroundings rock.Therefore,Planned wiring tunnel at Cujin station of metro Line 10 in Chengdu serving as research background,Seismic performance of shallow-buried tunnel has been analyzed with model test,digital image correlation and numerical simulation.It can give full play to the advantages that digital image related technology in the experiment,such as non-interference and large area of measured data,etc.The research contents and conclusion are as follows:(1)Shaking table model test shows that the measured values of acceleration sensors is gradually enlarged as it approaches the surface,where laid along the lining axis in stratum structure.The practical reliability of flexible lining model box with rigid boundary is verified by vault horizontal embedded acceleration measurement data.The hole formed by lining is easy to form stress concentration.The horizontal dynamic earth pressure value of surrounding rock is much greater than foundation and surface.The soil pressure value at the inverted arch of lining structure is the largest,about 55 kpa.(2)Experiment of expansion project's influence on existing building's deformation shows that the dial indicator data are consistent with the displacement with digital camera measurement in the process of loading adjacent to the old building.The total deformation values are less than the critical deformation values according to the code for design of building foundation.Experiment of shallow tunnel seismic model test shows that the results are consistent that comparing the input displacement of shaking table and the displacement field of photogrammetry.The results are in good agreement with each other that the reading of acceleration sensor and the calculated values of image processing.The comparative analysis of displacement field and acceleration field shows that digital photogrammetry technology can be successfully applied in seismic research of shallow tunnels.(3)Numerical calculations show that shallow buried tunnels change the initial stress of the lining structure during an earthquake.The surrounding rock produced a large deformation under the earthquake load.The horizontal displacement relative value of the surrounding rock is affected by the peak acceleration and elevation of the seismic wave in the vertical direction.It increases with the peak of acceleration and close to the surface.After increasing the buried depth of 7.7m to 12.7m,the numerical results show that the acceleration response of surrounding rock decreases.But the deformation of the surrounding rock and the internal force of the lining will increase,but the overall distribution characteristics are basically the same.(4)Under the action of different seismic wave types,comparing the internal force of shallow tunnel lining between model test and numerical calculation show that the axial force and bending moment at the lining arch are the largest in the seismic dynamic response,which is the key part of the tunnel seismic fortification.In order to ensure the seismic stability of tunnels,reinforcement measures should be taken in the seismic design of tunnels.