3D Model Test Of Ultra-deep-hole Column Charge Blasting In High Geostress Rock Mass

In December 2016,the national development and Reform Commission and the National Energy Board issued the coal industry development 13th Five-Year plan pointed out that coal accounts for more than 90%of China's fossil energy resources,which is the most stable,economic and independent guarantee energy.The proportion of coal in primary energy consumption will be gradually reduced,but in a long period of time,the main energy status will not change.13th Five-Year plan period,the economy of India and Southeast Asia and other regions of rapid development,the rapid growth of coal consumption,China's coal enterprises going out new opportunities.In order to achieve the 2025 Chinese manufacturing,make our country industry to move the automatic and intelligent direction,we must first be a coal industry upgrading,it is not only the trend of technology development,new requirements on safety production is also proposed.In order to realize the true meaning of the intelligent mining,should not only focus on coal mining informationization,automation,mechanization and technology,also need significant security risks in the process of prevention and control theory to carry out in-depth study of coal mining.Based on the project of National Natural Science Foundation of China the blasting mechanism and forced caving technology of super long deep hole column charge blasting in fully mechanized mining face(No.51374012).Taking deep hard roof as the research object,puts forward the control technology of ultra-deep-hole column charge loosening.Based on the theory of detonation dynamics,rock mechanics,fracture mechanics,stress wave theory and so on.By means of theoretical analysis,three-dimensional physical model test,numerical simulation and field test,a study on the fracture mechanism of the ultra-deep-hole column charge blasting under the condition of high ground stress.The relationship between the distribution of the stress field and the initial stress,the depth of the hole,the diameter of the hole,the distance between the holes and the coupling coefficient of the deep hole in the deep rock mass is studied.In this paper,the criterion of rock burst under the action of ground stress is established,and the mechanism of rock burst of deep hole blasting is studied.In the state of high ground stress,the blasting of ultra deep hole column charge is carried out.The explosive of the column will produce high strength shock wave,high temperature and high pressure explosive gas.Under the action of shock wave,the lateral displacement of the medium around the borehole forms a crushing zone,then decays into a stress wave,propagating in the medium and producing cracks in the radial of the borehole.Under the combined action of quasi static pressure of explosive gas and crustal stress,the radial fissure expands further.As the fracture continues to expand,the expansion pressure of the explosive gas decreases rapidly.When it drops to a certain extent,the elastic energy stored in the medium is released,and the unloading wave is formed and propagates to the center of the hole,and the circular cracks are formed in the medium,the radial fracture and the circumferential fracture intersect each other to form a fracture zone.In the static uniaxial compression test,the smaller the sand cement ratio is,the stronger the cementation between sand particles.The static uniaxial compressive strength of specimens decreases approximately with the increase of sand cement ratio.When the sand cement ratio is constant,the static uniaxial compressive strength increases with the increase of curing time.With the increase of curing time,the hydration reaction of the cementing material is more sufficient,and the dynamic strength of the specimen increases.With the hydration reaction of the cementing material,the cement and gypsum bonded particles decrease gradually.After reaching 21 d,the hydration reaction tends to stop.That is,the dynamic strength of the specimen is increased at 7 d-14 d,the speed of 14 d-21 d is increased slowly,and at last it remains basically unchanged.Taking into account the problem of the test cycle,we can determine the best curing time is 14 d.However,under the condition of passive confining pressure,the lateral deformation of the specimen is restrained by aluminum sleeve,the stress-strain curves can be divided into four stages:linear elastic stage,cohesive failure stage,compaction stage and unloading stage.Under the condition of high initial stress,the medium around the blasting hole is harder and broken,and the medium exhibits strong plasticity.In the case of uncoupled charge,there is an air gap between the borehole and the pillar.The greater the uncoupling coefficient,the larger the air gap in the borehole can effectively reduce the peak pressure of the blast wave and change the explosive stress wave,and can reduce the propagation time of explosive stress wave in rock mass and the quasi-static expansion time of explosive gas,expand the range of explosive fissure zone and improve the utilization rate of explosive energy.In addition,the initial stress has a certain inhibitory effect on burst propagation.Compared with the hydrostatic pressure state and the non-hydrostatic pressure state,it can be seen that under the hydrostatic pressure condition,the peak value of the strain wave in the hole direction,tangential direction and axial direction is almost the same,thus the cavity of the gun is round,and the distribution of the burst is distributed evenly around the hole after the explosion.However,in the non-hydrostatic pressure state,the maximum principal stress has a guiding effect on the crack propagation.With the increase of the lateral pressure coefficient,the peak value of the strain wave increases gradually,and the guiding effect of the maximum horizontal principal stress on the explosion crack is more obvious.In engineering practice,the design of blasting cycle is 30 m.,the working resistance of the hydraulic support of the working face is basically distributed in the normal range after blasting.The resistance of the front and rear columns is uniform,the resistance difference is less than 1 MPa,and the coal wall in the working face is more complete,basically there is no piece of help and roof fall.When the roof of the working face is treated by a loose blasting,the periodical pressure of the roof becomes smaller,and the local position of the working face has no obvious pressure.