Numerical Simulation Study On Rock Breaking Mechanism Of Compound Triangle Cut Blasting Under Confining Pressure Stress

Coal is an important basic energy.With the continuous development of national economy,our demand for coal and other mineral resources is growing.Shallow resources are becoming increasingly depleted and the mining depth is increasing.The in-situ stress environment and the occurrence characteristics of rock faced by deep mining projects will be more complicated.Under the action of initial in-situ stress field.the basic physical and mechanical properties of deep rock and the dynamic response characteristics of blasting excavation disturbance will also change.Under the combined action of in-situ stress field,blasting stress field and explosive gas,the mechanism of cut blasting becomes more complicated.Therefore,at this stage,it is very urgent to study the rock breaking mechanism of cut blasting under the action of initial in-situ stress field combined with the existing blasting theory.In order to solve the problem of deep rock cut blasting,this paper uses ANSYS/LS-DYNA software to simulate the rock breaking process of compound triangle cut blasting under the action of confining pressure stress.Based on the relevant theory of rock blasting,the factors such as the design of constitutive model of numerical simulation,the selection of blasting parameters,the layout of cut blast holes,the spacing of blast holes,the effect of empty holes,the stress value of confining pressure and the coefficient of lateral pressure are studied.The effects and infulences of the above factors on the damage evolution in the compound triangle cut blasting and the damage penetration characteristics between the blast holes are analyzed from various angles.The main study work is as follows:(1)Based on the relevant theory of blasting engineering,the process of rock blasting and rock breaking are analyzed.According to the difference of occurrence conditions of rock,the propagation and attenuation law of blasting stress wave in common rock mass,the incident and reflection characteristics of blasting stress wave in free surface,and the stress evolution distribution of rock around blast hole under the action of in-situ stress field are studied.(2)Based on the RHT constitutive model and H-J-C constitutive model of rock,the layout design of cut blast holes and the selection of reasonable blast holes spacing are studied by numerical simulation.The results show that:The blasting effect and damage evolution of compound triangular cut blasting are more suitable to study the rock breaking mechanism of cut blasting under confining pressure stress in the form of corner pillar cutting.Under the 0.3 m-0.5 m blast holes spacing,the 0.3 m blast holes spacing can better adapt to the complex conditions of deep rock blasting and make up for the defects of parallel cut blasting,which is the most reasonable blast holes spacing for compound triangular cut blasting.(3)Based on the fact that the in-situ stress gradually increases with the burial depth in the deep rock blasting project,the numerical simulation study of compound triangular cut blasting under no confining pressure and equal confining pressure stress.The effect and influence of the existence of confining pressure stress field and the change of the confining pressure stress value on the damage evolution in the compound triangle cut blasting and the damage penetration characteristics between the blast holes.The results show that:On the whole,the existence of confining pressure stress will restrain the development and penetration of blasting damage.The effect of the change of confining pressure value on the blasting damage of rock at different positions of compound triangle cut blasting is different.(4)Considering the complex and changeable horizontal in-situ stress in deep rock blasting engineering,the numerical simulation study on the process of rock breaking by compound triangular cut blasting under different lateral pressure coefficients was carried out.The results show that:The change of lateral pressure coefficient has a great influence on the direction and effect of damage expansion,and it also presents different regular characteristics in different positions of the compound triangle cutting area.