Nearly Horizontal Red Sandstone Tunnel Drilling And Blasting Method Of Construction Over And Under The Dig Control Technology

The effort of smooth blasting is bad when blasting in nearly horizontal layered rockmass with interlayer. It is difficult to formulate arch outline and big block rate is high while excessive and deficient excavate are universal. Using the combined research method of theory analysis, numerical simulation and field measurement, this paper have made a comprehensive study of the control technology of overbreak-underbreak in nearly horizontal layered rockmass. So it could reach the goal of controlling the overbreak, reducing the trial cost improving the eficient of underground excavation and so on. The contents of main research work include:(1) Based on three kinds of typical joints of layered rock masses, geologic features and structure effect on layered rock masses engineering are analyzed. Then failure types and failure mechanism of layered rock masses are further discussed.(2) This paper has analysis the reason of excessive and deficient excavate from the mechanism of rock blasting and the law of stress wave spreading through joint and interlayer. Research has proved that joint and weak interlayer has influenced the function of blasting on rock to a great extent which is caused by blasting stress wave and gas. The direction of resist ling of smooth blasting and rock crack expanding has changed. Therefore the unsmoothed outline is produced.(3) Based on the basic principle of smooth blasting design, according to the main problems in control of overbreak-underbreak for drilling and blasting in nearly horizontal layered rockmass, combined with on-site blasting test, then the parameters are optimized, and gradually adjust and eventually put forword blasting borehole layout and design parameters for different surrounding rocks, therefore, the overbreak-underbreak can be controlled reasonably.(4) The dynamic stability of surrounding rock and ground motion effects were analyzed and compared between original and improved blasting program, studies have shown improved program reduces shock effect and yield region in tunnel surrounding rock, can control overbreak-underbreak to a certain extent, so with great superiority and scientific.(5) This paper summed up the harm and the impact of overbreak-underbreak. In view of the the convenience and operability of field construction, we proposed four aspects to control the overbreak-underbreak of nearly horizontal layered red sandstone as follows:improve the accuracy of drilling, control charge parameters, standard charge structure and strengthen the construction management.