The Influence Of D&B Method To Construction Stability Of Shallow Buried Tunnel Under Highway

With Chinese rapid development of high-speed railway and the constant improvement of the infrastructure of basic transport facilities, the situation is inevitably intertwined lines. In this paper, based on the Shen Dan high-speed section wearing Shen Dan passenger line under the Da Dingshan tunnel, By means of field monitoring and numerical simulation, the D&B method is used when the excavation blasting vibration effect of wave on the surface, the influence of blasting vibration on the surrounding rock and lining, and the attenuation law of vibration wave is studied.The area surrounding rock is V grade, mostly shale rock, strongly weathered, rock crushing, joint development, poor rock conditions. The normal operation of ground highway was under bigger threat of blasting. So, the surface effect of vibration test on site and Tunnel surrounding rock deformation monitoring were carried out firstly, monitoring data were analyzed on this basis, through the establishment of numerical model of the excavation process in different directions attenuation of surface velocity and surface displacement field effects were analyzed and predicted and measured results were compared with the final. Finally, for the situation in this region with multi-level rock joints, the influence of the contact behavior of joints and the parameters of joints on the propagation of blasting stress wave and settlement rule were analyzed.The results of monitoring and analysis show that Shen Dan Passenger Line Dadingshan highway tunnel wearing surface subsidence and shock speed are within the allowable range, the disturbance of rock.caused by blasting construction was small. The analysis of each component of the vibrates velocity showed that Porgy cut holes, auxiliary and peripheral hole blasting holes formed in the overlay was not superimposed, so it could effectively determine the charge blasting each segment corresponding to the amplitude of the surface vibration velocity. Before and after each working face along the tunnel axis surface vibration velocity measuring point found the measuring point has been excavated surface vibration velocity greater than the front of face. The Sa Rodolfo J Ki formula with front and rear surface velocity data were fitted found that this formula is available in front of the tunnel boring prediction (K=384.5,α=1.16), while the rear errors. The relationship between the normal stiffness of joint and the transmission coefficient were an exponential increase in; equivalent stiffness under the same circumstances, the transmitted wave velocity decreases with the increase in the coefficient of friction. Tips:The special attention should been paid to the next junction monitoring and protection against bursting due to stress concentration and excessive construction disturbance and displacement in blasting.