| Taking the roadway along the goaf of 3412 hard roof working face in Xinyuan Coal Mine as the research background,the weakening mechanism of hard roof,the mechanism of energy accumulation blasting and the technology of energy accumulation blasting roof cutting are analyzed by numerical calculation and theoretical analysis,and the hard roof weakening technology of energy accumulation blasting along goaf is put forward,and the rationality of the scheme is verified by industrial test.The main research results are as follows:(1)the principle of energy accumulation blasting is studied,the stress distribution characteristics and fracture development law of roof strata under different charge structure of energy accumulation blasting are analyzed,and the influence of energy accumulation cover structure on energy accumulation effect is discussed.The results show that the conical energy accumulation cover is more beneficial to erode the surrounding rock to induce fracture development and expansion,destroy roof integrity and reduce rock strength,so as to achieve the purpose of roof pressure relief.When the angle is 60 °conical energy accumulation cover,the peak stress of rock unit reaches the maximum,that is to say,the effect of energy accumulation is the best,which is more beneficial to the generation,development and expansion of rock cracks.(2)the numerical model is established by LS-DYNA dynamic analysis software,and the effects of hole spacing,hole diameter and radial uncoupling coefficient on the effect of energy accumulation blasting are compared and analyzed.The results show that the hole diameter is positively correlated with the crack propagation length and the element stress peak value,and the hole spacing is negatively correlated with the crack propagation length and the element stress peak value.With the increase of the radial uncoupling coefficient,the fracture length and stress peak value increase at first and then decrease.(3)combined with the geological conditions of 3412 working face in Xinyuan Coal Mine,the parameters and schemes of pre-split and pressure accumulation blasting along goaf are designed.The blasting effects corresponding to different hole spacing,hole diameter and radial uncoupling coefficient are compared and analyzed.It is determined that the hole spacing is 1.2 m,the hole diameter is 70 cm,and the radial uncoupling coefficient is 1.6.At the same time,the drilling arrangement,blasting equipment and blasting time and scheme are determined,and the field construction technology of pre-split energy accumulation blasting is given,including drilling,charge,sealing and firing.(4)The influence of energy accumulation blasting on the crack propagation of the hole is analyzed by hole peeping.The peeping results show that the rock around the hole has obvious conical incision in the direction of energy accumulation ring accumulation energy,and obvious in the direction of energy accumulation.The horizontal fracture and vertical crack are well developed,and the fracture gap is larger,but there are only a small number of cracks in the direction of non-accumulation energy,and the development is not obvious.Therefore,energy accumulation blasting can have a good directional fracture effect on roof strata,so that cracks can expand directional,and then the purpose of directional fracture of roof strata can be realized.(5)The research results are applied to 3412 working face of Xinyuan Mine.The monitoring results show that the displacement of the two sides and the subsidence of the roof are reduced by 252 mm and 281 mm,respectively,and the reduction ranges are 35.8% and 62.4%,respectively.This indicates that the pre-split blasting roof cutting plays a key role in the process of retaining roadway along the goaf,and can control the deformation of the surrounding rock along the goaf in a reasonable range and improve the stability of the surrounding rock along the goaf.There are 38 figures,4 tables and 83 references in this dissertation. |
PDF Full Text Request