| For construction needs of the Longyanjing tunnel, the thesis discusses numerical simulation in tunnel blasting and design of smooth blasting on soft rock, resolving effectively some problem in the soft rock tunnel excavation by NATM, such as tunnel stability, construction interference and work period etc, and obtaining the obvious economic benefit. By the theories analysis and numerical simulation to vibration velocity field and stress field in rock caused by explosion, the disturbed area in surround rock is defined clearly, and then the smooth blasting design of soft rock is carried out. The blasting parameters are adjusted in accordance with the site experience and test, to ensure that the blasting design in soft rock is up to the actual situation, so that the purpose of rock protection and tunnel stability is reached. Practice proves that there is a direct relation between the blasting affected on surround rock and blasting method, parameters. It will reduce zone of surround rock damage at least to select suitable blasting method, parameters and excavation method. Rock vibration or explosion load lead to the instantaneous load, under these circumstances, stress is at dynamic or quasi-static. Tunnel stability, especially in soft rock tunnel, will be affected to certain degree for the enormous over-break or under-break of excavation. It should be point out that the over-break or under-break caused by tunnel excavation is unavoidable, but these may be controlled. The advance blasting techniques can limit them to certain scope, the rock damage zone in blasting can be limited within certain range too. The smooth blasting with half-section and smaller bench is very effective to solve a problem of NATM, to reduce rock damage zone and speed up construction progress. In this blasting, the bench with 3-5m length is always left at work face, simultaneously, the smooth blasting is implemented to reduce strength of explosion vibration and surround rock instability.
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