Deep Hole Column Blasting Model Test And Numerical Simulation Research

With the depletion of shallow resource exploitation,more and more coal mines are in deep mining.Borehole blasting is widely used in coal mining,such as roadway blasting,thick hard roof forced caving,gas permeability,etc..Among them,the thick and hard roof forced caving is in the thick layer of hard rock in deep hole cylindrical charge blasting,there is no free surface,the design of its construction is mainly based on experience.However,many literatures have shown that in the deep strata,the strata are affected by high ground stress,and the range of explosive explosion is different from that of shallow strata.In this paper,the failure mode and mechanism of high stress rock mass under impact load are studied by the combination of model experiment and numerical simulation.Through access to a large number of domestic and foreign literature,and combined with the theory of stress wave,high stress field in rock blasting impact load will produce an unloading wave,and with the increase of stress is increasingly obvious;the stress field of rock blasting in the Highlands,in addition to the direct action of explosion shock wave and explosive gas the unloading wave also contains in cavity around the formation of crack reflection.Based on this model,a blasting model test is carried out to simulate the damage of high stress rock mass under the action of unloading wave.The experimental model of steel tube with the compressive strength of 30MPa cement mortar material to simulate rock mass,the diameter of 400mm to simulate the rock mass in the deep clamping effect,with the diameter of 5mm,length of 1000mm aluminum fiber detonating simulation of column charge generated by shock wave,reflected wave in steel-cement mortar interface simulation of unloading wave in rock mass.The measuring points,the ultra dynamic strain instrument strain wave in the hole arranged around the strain gauge,to analysis the stress distribution around the hole;at the same time,with the help of the embedded electrode parallel electrical blasting damage model body test.At the same time,using LS-DYNA finite element software,the constraint conditions of deep hole column blasting rock breaking process are analyzed,and the crack propagation process of propagation process of shock wave model in research on constraint conditions,in order to explorethe high stress field of rock deep hole explosive column crack and damage mechanism.The main conclusions are as follows:1)The crack initiation and propagation in cement mortar have obvious hysteresis effect on the propagation of stress wave.2.Through the deep hole blasting model test of cement mortar under the constraint of steel casing,the possibility of the formation of cracks and damage in the deep high stress rock mass is verified.3)According to the resistivity distribution before and after blasting,and combined with the numerical simulation results show the crack formed by the unloading wave and not blasting through,its formation mechanism and the crack is obviously different,the damage around the hole is crushed and the axial tensile radial crack formation and crack,unloading wave is mainly axial crack formation due to the radial tensile,and the two is through.4)On the basis of the formula of SA,combined with the distribution law of blasting vibration peak value in numerical simulation,the empirical formula of blasting vibration attenuation of deep hole blasting model is obtained.5)Based on the strain rate effect of concrete,rock and other materials,combined with the numerical simulation of the stress wave attenuation law of deep hole blasting model,this paper puts forward a method to evaluate the damage range of blasting engineering.