Study On Principles And Parameters Of Destress Blasting In High Geo-stress Tunnel

The study start from the history of destressing, summed up the development process, current situation and existing problems of destress blast. The basic content of the study is to study the dynamics destressing, on this basis, a reasonable blasting parameters, using numerical simulation to verify the analysis. Describes the main types of destress blast, the propagation regulation of rock shock waves and stress wave, including wave's superposition, reflection and transmission effects. Static and dynamic loading are introduced in the rock explosion within the role and mechanism of rock failure mechanics, the stress wave propagation of the destress blast and the pressure release process are explored, and describes the single extent of blast hole pressure release calculation process.The deep tunnel destressing design principles and parameters influencing factors is introduced, according to energy balance theory of Livingston, get the the critical depth of destressing, considering the premise of a certain bearing circle, a reasonable calculation of hole depth is designed. Calculate a reasonable range of blasting explosives consumption. For the destress blast without control hole, it is best for the fissures to be transfixed between adjacent hole and reasonable distance between two holes and row spacing b is equal to the diameter of the rupture zone. From the view of fracture mechanics, and considered rock coefficient of Platts, available holes spacing also can be calculated. On the basis of the stress wave theory and the theory of elasticity, discuss the effect of control hole blasting discussed and the holes spacing. Choose different charge way for different roadway, and using different initiations. The block length of the charge are discussed under coupling and decoupling.ANSYS and LS-DYNA software were used to simulation the static stress field of and high stress tunnel before and after the destressing, discussed static stress of the tunnel on the one-way stress in 10MPa load and load triaxial stress conditions. The one-way stress load is generally greater than the stress loading of triaxial state, but in the triaxial loading condition, tunnel prone to deformation, so in this case, not suitable for destressing. The study also simulated the rock mass by destress blast lin the tunnel and the size of the cavity after blasted, discussed the stress state of surrounding rock in the tunnel under the destress blast, during blasting there is no damage on the surface of the tunnel. In order to study the stress state of the tunnel after blasting, consider the blasted cavity as a cylindrical cavity, and establish the tunnel model, add static loading, calculated results show that, stress concentration zone near the tunnel disappeared after destress blast, and moved to the vicinity of the blasted cavity, the stress value decreased by 20%. Assuming the formation of cracks cavity as rectangular strip after the blast, after simulation, you can see the stress of tunnel floor was further reduce, reduced from the original 20 MPa to 12 MPa. However, there is a new stress concentration on the top two sides of tunnel. If both the roof and the two side of the tunnel have formed a crack area, which is an ideal state, in this state, there is no obvious stress concentration, stress get the maximum relased.