Experimental Research On Non-undercutting Coal Mine Tunnel Excavation

Roadway excavation is an important part of coal production. Our countryis has still mainly adopting the method of drilling and blasting in roadway excavation at present and for a long period in the future. The function of coal mine roadway excavation by drilling and blasting is restricted by various conditions, such as rock conditions, construction space, gas safety conditions, blasting conditions and so on. In such cases, improving the blasting efficiency by using optimizing processes and blasting parameters in the current equipment would be in an important position, and a long-term experimental study has been conducted. The results show that the "three little light burst’tunneling technology and smooth blasting technology in deep hole are the most typical way."Three little light burst’tunneling technology whose disadvantage is the practices applicable to shallow eyes small cycles and inefficient in large TBM, has been widely used. Various kinds of deep hole smooth blasting technology has been in test marketing. The main problem is difficult to produce a more general program of long-term because of lithology changes. Whether using "three little light burst" or "burst of light in deep hole", the light burst effects in actual construction of the optical burst are difficult to properly reflected.By constructing roadway model, designing hole net parameter, establishing ultra dynamic strain measurement system, and analyzing comparatively the blasting effects and the differences of strain waveform inside the rock of three blasting methods, which are the middle of an empty hole parallel cut, tapered and undercut segments without undercutting, studying the rock breaking mechanism of more columnar charge without undercutting blasting, determining the key technical parameters, the section hole layout and the instructions of no undercutting blasting, as well as determining the construction process and blasting operations organization of it, the test drives the following conclusions:(1) The volumes of blasted rock of the three roadway model are the same. The consumption amount of cycled explosives of empty hole in the middle parallel cut and tapered undercut are13.3g/m, and no cut blasting explosives is12.5g/m. From Figure19and Figure21, we can see that the tank chamber of non-cut blasting is bigger than that of cut blasting and the utilization is higher.(2) The explosion peak strain are0.1996、0.1923、0.1990respectively at the face of100mm from the strain gauges at the peak strain ε. The explosion peak strain are0.1379、0.1908、0.1489respectively at the face of250mm from the strain gauges at the peak strain ε, and the three numbers are near.(3)Through high-speed camera images, we can clearly see that there are differences in the free s urface fomation directions and numbers between non-blasting and blasting. The blasting one forms a groove to groove centre blasting chamber and have only one free surface. When the surrounding bl asting, there are two free surfaces. While in the non-blasting, there is one free surface from the begin ning to the end, which is facing up.