Application Of Smooth Blasting Technique To Excavation Of Soft Rock Foundation Plane

Because of the characteristics of agility, convenience, speediness and economic of blasting technique, it have been widely used to in available foundation of main dam foundation, nuclear power station foundation and large bridge anchorage foundation. However, because of the intensive action of conventional blasting, the soft rock mass under the bottom of the foundation is usually damaged or fragmentized. Bed rock may not meet the engineering requirement, so how to weaken even eliminate the bedrock damage or fragmentized become a key issue in construction quality control. Therefore, the research of the coating of reserved shape once Smooth blasting technology which had succeed in use at medium hardness and more rock is put forward. However, soft Foundation Surface which difficult to mechanical method excavation is feasible or not, how to select blasting parameters. These problems need to be resolved urgently.Through the combination of theoretical analysis, numerical simulation, and field test, Smooth blasting principles and compaction effects are explored in this thesis. First, based on the relevant knowledge of explosion dynamics, Aerodynamics and soil mechanics, explosive model of weak rock is established. In addition, surrounding rock damage range is derived theoretically. Second, by using software ANSYS/LS-DYNA, rock fracture process is built. Through numerical simulation results and the theoretical calculation result are comparative analyze, which confirms the feasibility of the application of numerical analysis to practical engineering. Finally, through the combination the result of field test of NaXi Changjiang River Bridge, which confirms the feasibility of theoretical formula and numerical simulation results, blasting design parameter is given.Because of cavity expansion, surrounding rock damage range may oversize. According to this problem, applied on the theory that blasting gas is isentropic adiabatic expansion in the lamination cracks and charge hole, the quasi-static mechanical model for Soft Rock Foundation Plane was established during the Smooth blasting. The explicit expressions of the quasi-static pressure in the blast hole and the blasting cavity radius of Blast hole cavity expansion. Through the study on tensile stress at the crack effect in rock caused by blasting, the quantitative relationship between surrounding rock damage range and linear charge density was obtained. Further analysis study found, surrounding rock damage range along with the linear charge density increases, When Linear charge density smaller, blast hole is not occur cavity expansion, increase rate of surrounding rock damage range is more. Combined the theoretical formula and actual rock parameters, blasting parameters such as blast hole parameters, hole-space, cover thickness (minimum resistance line), the charge of borehole will be design.By using software ANSYS/LS-DYNA, rock fracture process is built. This thesis get through simulation in Smooth blasting which changing linear charge density and spacing in drilling, analysis the influence law of surrounding rock damage range. Through the results shown, a change the size of linear charge density after gets that numerical simulation and theory of the same basic law is derived. Surrounding rock damage range along with the linear charge density increases, When linear charge density smaller, blast hole is not occur cavity expansion, increase rate of surrounding rock damage range is more. When linear charge density invariant, a change the size of spacing in drilling after get that surrounding rock damage range along with spacing in drilling increase, if spacing in drilling is lesser, surrounding rock damage range to spacing in drilling with decreases, and if spacing in drilling increases to certain value, surrounding rock damage range unchanged.The foundation surface smooth blasting test is proceeding at Foundation Surface of NaXi Yangtze river bridge anchorage foundation pit. Through the combination of Smooth blasting theory and blasting test effect, blasting parameters are optimized adjustment, is give reasonable parameters. Through the combination of theoretical analysis, numerical simulation, and field test, Smooth blasting principles and compaction effects comparative analysis, the results shown that the value of theory formula of surrounding rock damage range bigger than the actual value, relative error along with the linear charge density increases. In this thesis, the accuracy of Damage range of surrounding rock after the explosion was higher and the relative error was less than10%.so that these formulas can be applied to engineering practice.