Study On The Law Of Crack Propagation And Stress Distribution In Eccentric Charge Of Blasthole Under The Action Of In-situ Stress

The smooth blasting theory is based on the concentric uncoupled charge structure.In actual construction,the drilling rig often drills horizontally or obliquely downwards.When the walls are in contact,the two have an eccentric effect,forming an eccentric uncoupled charge structure.As the depth of excavation increases,the effect of in-situ stress becomes prominent and cannot be ignored.Therefore,the eccentric non-coupling charge in this case is studied,the specific contents are as follows:(1)Due to the particularity of this type of charge structure,the concentric uncoupled charge theory is used to redefine the uncoupling coefficient K_E at various positions of the blasthole wall when the blasthole is eccentrically charged,and to derive the calculation on the blasthole wall The theoretical formula of the uncoupling coefficient at one point shows that as the deflection angle increases,the uncoupling coefficient decreases;when the aperture difference increases,the uncoupling coefficient also increases.On this basis,according to the theory of explosion stress wave and detonation gas,considering the effect of in-situ stress,following the law of conservation of momentum and the propagation law of shock wave,the radius of the crushing area is determined,and then the radius of the crushing area is used as the equivalent hole radius The calculation formula of the initial crack under the action of stress wave is deduced;combined with the fracture mechanics and the maximum circumferential stress theory as the criterion,the calculation formula of the expansion crack under the action of explosive gas is derived.(2)Select No.2 rock emulsified explosives and 3 types of common rocks to obtain the initial crack range under the eccentric uncoupled charge.The analysis found that the existence of in-situ stress is an important factor restricting the propagation of cracks,and the length of the initial crack is determined by both the uncoupling coefficient and the in-situ stress;as the in-situ stress continues to increase,the distribution of cracks on the uncoupling side and the coupling side is quite different The range of fissures continues to shrink,and the range of fissures on the uncoupled side gradually approaches the radius of the crushing zone.(3)Using the method of numerical simulation to simulate the whole process of eccentric charge blasting under the action of in-situ stress,it is found that the eccentric charge has obvious eccentric effect under various working conditions,and it is well verified that the eccentric uncoupled charge Eccentric effect,and found that the expansion of the crushing area is also affected by in-situ stress.(4)The blast stress field generated by eccentric blasting with air and water as the filling medium is studied,and it is found that the peak stresses of the coupling test are larger than the stress peaks of the uncoupled side,and the time of the stress peaks of the uncoupled side lags behind the coupled side;Comparison found that the ability of water medium to transfer blasting energy is much higher than that of air medium.Therefore,blasting using water as the filling medium is superior to air.The paper has 33 pictures,19 tables and 74 references.