Experimental Study On The Weak Disturbance Drivage Blasting Technology For The Small-Distance Tunnel With Deeply Dipping Laminated And Small Angle Rock Body

Many small-distance tunnel with deeply dipping laminated and small angle rock body distribut throughout the high speed line of Nan-fu line in Chong Qing. During the blasting of small-distance tunnel, blasting vibration load must cause disturbance and damage of the middle wall. Especially for the small-distance tunnel with deeply dipping laminated and small angle rock body, Excessive blasting vibration may destroy the stability of middle wall. So, study on the weak disturbance drivage blasting technology for the small-distance tunnel with deeply dipping laminated and small angle rock body is very meaningful to instruct construction.Taking the Ya-jiang tunnel and watershed tunnel as specific example, the in-situ test, mathematical statistics, theoretical analysis and engineering analogy methods are used in studying excavation blasting seismic effect of the latter hole excavation blasting seismic effect. On the basis of excavation blasting seismic effect research results, weak disturbance drivage blasting technology for the small-distance tunnel with deeply dipping laminated and small angle rock body is raised. Then field test and application for weak disturbance drivage blasting technology was carried out. Research results basically has the following several aspects.Through field test on conventional excavation blasting in the Ya-jiang tunnel,We found that, When the latter tunnel excavation blasting, the vibration distribution is uneven on the middle wall. Face blasting side vibration is greater than the back side, usually around2～10times. In the same point radial vibration is bigger than the vertical, usually around1～3times. The vibrating is unequal in equidistant point of front and back between the tunnel face. The back is1-2times the vibration of the front. At the same time, the attenuation trend of vibration behind the tunnel face is slower than the front. Attenuation law cannot be described by SaDaoFu formula.In the same drivage blasting, the charge mass of the cut hole is not the biggest. Due to free surface condition, the specific consumption of charge and blasting vibration are biggest. The key of control tunnel blasting vibration is control blasting vibration of cut hole. In order to ensure the blasting seismic waves do not stack, the delay time is greater than50ms.The blasting vibration of conventional excavation blasting in the Ya-jiang tunnel is greater than8cm/s. So, the weak disturbance drivage blasting technology is raised. They contain that latter hole and first hole is stagger when building, every tunnel take the method of up and down the steps, the deck charge and delay in-hole is apply in cut hole. Smooth blasting technique is used. Combined with the construction condition of specific example, the weak disturbance drivage blasting design with3.2m footage of up step is made. Then, the demonstration and application for the design is carried in Ya-jiang tunnel and watershed tunnel. It is not only acheieved good blasting effect, but also can control the blasting vibration effectively. At the same time, specific consumption of charge is reduced, so the economic benefit of the project is directly created by this design.Through the demonstration test of weak disturbance drivage blasting in Ya-jiang tunnel, the blasting vibration reduce from11.92cm/s to7.47cm/s, the proportion is about40%. Through the application test of weak disturbance drivage blasting in watershed tunnel, the blasting vibration reduce from18.99cm/s cm/s to7.31cm/s, the proportion is about60%.Due to the charge mass of initiating section in the weak disturbance drivage blasting is decrease,the blasting vibration is weaken in every initiating section.