| In this paper,the effect of multi-arch tunnel on the middle partition wall during blasting construction is studied.The multi-arch tunnel in Wufeng mountain,Enshi city,Hubei Province is taken as the engineering background.The data are analyzed and sorted out based on theoretical analysis and field monitoring and measurement combined with numerical simulation.The dynamic response of multi-arch tunnel blasting construction to the middle partition wall under different excavation methods,different excavation footage and different surrounding rock grades was studied.The main work contents are as follows:(1)According to the monitoring data of blasting vibration at the waist of the middle partition wall in wufengshan multi-arch tunnel,the formula of vibration velocity attenuation of the particle at the waist of the middle partition wall in the tunnel is obtained through linear regression analysis,which provides reference for the subsequent blasting construction and guarantees the safety of the middle partition wall during blasting construction.(2)MIDAS/GTS NX was used to establish the finite element model of Wufengshan tunnel to study the impact of blasting construction on the middle partition wall and obtain the vibration velocity at the waist of the middle partition wall.Linear regression analysis was conducted on the data to obtain the vibration velocity attenuation law,which was compared with the vibration velocity attenuation law of field measured data to verify the reliability of numerical simulation.(3)The dynamic response of multi-arch tunnel blasting construction to the middle partition wall under different excavation footage is analyzed by numerical simulation method.In the blasting construction of upper and lower steps method and full section method,the excavation footage should be controlled within 2m and 1m respectively.When the footage is exceeded,the partition wall in the tunnel will be damaged.Considering the construction progress,safety and economy of the actual project,the method of up and down stairs should be used for the construction of multi-arch tunnel.(4)The dynamic response of multi-arch tunnel blasting construction to the middle partition wall under different rock levels is analyzed by numerical simulation method.The same node with the improvement of level of surrounding rock,middle wallvibration velocity and the bigger the peak value of tensile stress,and peak need longer and ?,? class surrounding rock in construction of tunnel middle wall under the maximum speed and maximum tensile stress are not higher than the corresponding safety control standards,the middle wall in the security state. |
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