Study On The Control Technology Of Blasting Damage In Neighborhood Tunnel Of Expressway

Neighborhood tunnel because of its advantages of less damage to the environment, less land occupation, convenient in route investigation and planning and other unique advantages had been more and more widely being used in the expressway mountain tunnels of our country. The section area of expressway tunnel is up to 90m2, and the widened lane will be more than 100 m2, the plastic zone of surrounding rock will very great after the tunnel excavation, a large number of stress will concentrate around the tunnel contour, if the self bearing capacity of surrounding rock can not be well protected, the cost of tunnel support will greatly increase in order to ensure the quality and safety of tunnel construction. The middle rock pillar have a little thickness,and its stress conditions is more complex, so it is necessary to strengthen the monitoring and controlling the blasting damage to it.In this paper, choosing the Shisanjian Tunnel of Yichang-Zhangjiajie Expressway as the project background, the study was divided into the active control technology and passive control technology two aspects to be proceeded. By combining theoretical, experimental analysis, numerical simulation calculation with field monitoring, the control technology of blasting damage to the neighborhood tunnel was studied. Through those studies we got some solutions which can solve the troubles come from the construction process of Shisanjian Tunnel, the results of the study can provide some reference for similar projects.1. According to the design parameters of rock bolt in Shisanjian Tunnel, through the numerical calculation to four kinds of operating conditions for surrounding rock of III and three kinds of operating conditions for surrounding rock of V by FLAC 3D, we obtained a reasonable rock bolt parameter for each surrounding class which can make the dynamic response most reasonable of the tunnel to blasting vibration.2.To special region with broken surrounding rock and a lot of groundwater, in order to reinforce the surrounding rock and reducing the strength loss of limestone in the case of water softening, the grouting method and grouting parameters were studied. We obtained a ratio parameters of cement and sodium silicate grout more suitable for Shisanjian Tunnel from the study. Through detection and analysis on grouted surrounding rock by geological radar, we got reasonable grouting methods and parameters in different parts of the tunnel, it provided the basis for the accurate grouting of the tunnel.3.To special region with a great peak vibration velocity at its surrounding rock(especially middle rock pillar) when blasting and soft and broken surrounding rock,where is very sensitive to the blasting damage, the damping technology of the tunnel blasting hole design is studied and applied. By placing the cut holes far from the middle rock pillar, and combining with monitoring and analysis to field test blasting, we draw a design scheme of blasting holes which can effectively reduce the peak vibration velocity of the middle rock pillar.