| With the rapid development of the national economy,the demand for energy is increasing,and the mining of existing mineral resources is mostly within-1500m,the efficient and safe mining of deep resources has become the strategic orientation of the country.During the 13th five-year plan period,the state proposed a plan for the development of deep land resources(-1500m deep).In deep land resources exploitation,shaft is the"throat"of mineral resources exploitation,because shaft construction period is long,how to shorten shaft construction cycle is an important task of mine construction.Based on this,this topic based on the national key research project"deep resources prospecting and exploitation"corpus"deep well efficient break rock with flushing slag discharge key technology(2016YFC0600903)",to carry out the shaft deep hole section cut blasting and damage of surrounding rock control mechanism research,by means of laboratory tests,numerical simulations and field applications,analyze the rock-breaking mechanism of the segmented charge in the hole,evolution law of field strain in medium,provides a basis for reasonably optimizing the sectional charge coefficient in the hole and improving the energy utilization efficiency of explosives.The influence of blasting on surrounding rock damage was studied by CT scanning and 3d reconstruction,to study the mechanism of accumulated energy and the mechanism of loss reduction.The research results mainly include the following aspects:(1)Carried out the physical model test of deep hole sectional cutting.The sectional charging changed the stress state of the rock mass,changed the matching relationship between the anti-detonation force of rock and the rock breaking ability of explosives,thus reduced the clamping of rock at the bottom of the hole and increased the degree of rock fragmentation.The equivalent rock breaking resistance of subsection charge is greater than that of continuous charge,thus increasing the rock breaking depth.Through the model experiment,it can be concluded that the utilization ratio of blast-hole and cut cavity is the largest and the bulk ratio is the smallest when the proportion of upper section charge is 0.4.Upper and lower segment ratio change is the nature of the change of explosive energy distribution proportion,the section of rock mass under the original free surface,the distribution of smaller charge,can achieve good cutting effect,more explosive assigned to clip made of rock mass under the larger section,at the same time,the sectional blasting for next sublevel rock first created a new space for free surface and toss.(2)Using AUTODYN numerical software,it is concluded that the propagation velocity of cut cavity is divided into two stages.In the first stage,the rock is mainly affected by the interaction of explosive stress wave and detonation gas,and the velocity rises sharply.In the case of segmented charging,the throwing velocity of the upper segmented rock mass is higher than that of the continuous charging.After the upper segmented rock mass is thrown,the resistance line of the lower segmented explosive decreases,and the throwing velocity of the rock mass is higher than that of the measuring point at the same position of the continuous charging.Through the analysis of the fractal damage degree of the lower cut cavity with different section loading ratio,it is found that the damage degree of the upper cut cavity is the largest when the proportion of the upper section charging is 0.4,and the damage degree of the cut cavity is the largest.In this case,the stress state of the lower rock mass of the section charging is larger than that of the upper rock mass,which is conducive to the throwing of the lower rock mass.(3)The fracture characteristics and full-field strain evolution law of explosive crack in cylindrical charge envelope were studied,and it was concluded that the propagation length of the wing crack at the initiation point was the smallest regardless of the initiation at one end or the center of the cylinder charge envelope,and the propagation length of the wing crack increased with the propagation direction of explosive detonation.Center of columnar cartridge wing crack extension mainlyⅠtype is given priority to,end wing crack and the crack arrest stage of crack is given priority to withⅠtype crack,in the process of crack path deflect mainlyⅡtype crack;At one end of initiation,the maximum value of radial compressive strain corresponds to a distance of 0.67～0.83 times of the length of the blast-hole from the initiation point.At the center of initiation,the strain at the center point is the largest,and the compressive strain at both ends becomes smaller.Under both initiation modes,the phenomenon of end compressive strain concentration occurs.(4)According to the study on the strain superposition effect of double blast-hole in the cylindrical charge,the superposition effect can prolong the action time and strength of axial tensile strain,while the compressive strain only shows an increase in strength.At the position of the detonating end,the superposition effect of radial compressive strain and axial tensile strain is less than 2 times of the strain generated by the single hole,with the direction of explosive transmission,the superposition of radial pressure strain and axial tension strain is greater than 2 times the strain produced by single blast-hole.The maximum radial compressive strain is 2.38 times of the compressive strain of single blast-hole and the maximum axial tensile strain is 2.15times of the tensile strain of single blast-hole.(5)Analyzed the evolution law of full-field strain of segmented charge,the full-field strain shape of continuous charge on medium is changed from one strain to two strains.Under the condition that the destruction of the first explosive to the medium is satisfied,the effect of the second explosive on the medium is increased,and the time of the rock subjected to the explosion stress wave is prolonged.With the increase of the delay time between the two sections,the time of the medium under the action of the explosion load increases,and the interaction effect between the two sections weakens.The stress wave formed after the explosion of the upper section explosive is more obvious to the strain generated at the blockage of the lower section and lower section,which is more conducive to the fragmentation of the lower section medium.(6)By adopting the high speed schlieren and air shock wave overpressure test system,the explosion shock wave and detonation gas in the slit package were tracked and photographed,and the explosion shock wave was first transmitted along the slit direction,and the detonation gas mainly expanded along the slit direction in the shape of"Ⅰ".In the near area of the slit charge,the pressure ratio between the slit direction and the vertical slit direction decreases with the proportional distance increasing,this indicates that the closer to the slit cartridge,the greater the pressure difference between the two directions of the air shock wave.(7)For the materials with different strength,the extended form of blast wave and detonation gas is basically the same,maintaining a highly symmetrical form.In the early stage of explosion,explosion shock wave and detonation gas are first transmitted from the slit,which is not affected by the slit material.Different materials of slotted pipes have different effects on the cumulative energy effect,according to the overpressure curve,the stainless steel tube has the best cumulative energy effect,followed by PVC tube and plexiglass tube.(8)The blast wave in the direction of slit first reaches the hole wall of blast-hole and reflects,explosive gas mainly acting the slit direction on the wall of blast-hole,and it forms aggregation on the wall of the gun hole in the direction of the slit.The slit charge has the characteristic of accumulating explosive gas,and the expansion rate of the slit charge explosive gas is higher than that of the ordinary charge.The velocity of the blast wave at the hole wall is lower than that of the incident shock wave.The numerical simulation shows that the explosive fluctuation of the slit charge in the gun hole is consistent with the high speed schlieren test.(9)According to the schlieren test,the expansion shape of the blast wave is"spindle shaped"when one end explodes,and"diamond shaped"when the center explodes.The velocity attenuation zone occurs when the cylindrical charge changes from detonation wave to shock wave,and certain included Angle of detonation wave occurs during the process of detonation transmission,the angle ranges from 58~0 to 62~0.According to the model analysis,the angle between blast wave and blast-hole wall is90°near the detonation point of the cylindrical charge,during the detonation process,the included Angle between the blast wave and the gun hole wall is betweenδ～90°,and the value ofδis between 59~0～61~0.The rupture range of the columnar charge is about 5 times of the diameter of the gun hole,and it shows obvious fractal characteristics.It is mainly divided into three regions,namely,the medium is completely crushed,and the region is the crack concentration;The medium is broken seriously and is the crack transition zone;There are few detonation cracks in the medium,and the cracks are sparse.(10)According to the results of three-dimensional fracture reconstruction of rock mass failure by slot-filled cartridge bag and common cartridge bag,the explosive crack of slot-filled cartridge bag only produces two cracks along the slot-filled direction,while no obvious cracks occur in other directions.The rock mass damage degree was reduced by 57%.When the explosive crack of the common charge interacts with the joint,the crack and the joint surface have crack stopping or dislocation penetrating the joint surface,resulting in the formation of irregular fracture surface,the crack surface is relatively flat when penetrating joint.(11)Under the segmented charging structure,the three-dimensional cracks generated by the explosion on the rock body run through the whole specimen,the continuous charging structure,no explosion cracks are generated on the rock body in the block section 20mm away from the orifice.The damage degree of subsection charge rock was 23.5%higher than that caused by continuous charge.Under the two charging structures,the cracks generated by the 50mm explosion in the upper segment had the greatest difference,and the damage degree of the upper segment was 46.4%higher than that of the continuous charge.(12)It can be seen from the three-dimensional fracture distribution of rock after blasting in different filling media,when water and sand are used as filling media,the explosive crack is the most,the blast-hole crushing zone is the largest,the crack density is the largest,and the explosive crack is the least when air is uncoupled.At the bottom of the gun hole,a circular crack centered on the bottom of the hole is formed,the rock mass damage degree was 57.1%higher when water and sand filled medium than when air filled medium.(13)When the main explosive crack expands to the vicinity of the flaw,the flaw has an inhibitory effect on the crack growth.With the increase of the curvature of the flaw,the inhibitory effect increases continuously,so that the growth rate and stress intensity factor value of the explosive crack decrease.The energy accumulation rate of the closed defect crack is higher than that of the open crack,and the energy accumulation rate of the open crack decreases with the decrease of curvature,while the initiation time of the wing crack increases.The fracture toughness of the wing crack increases with the decrease of curvature,when the curvature decreases to a certain extent,the wing crack cannot crack.The fracture toughness of the wing crack is greater than that of the crack during propagation.There is a positive correlation between the dynamic stress intensity factor at the crack tip and the crack velocity,that is,within a certain range,the stress intensity factor increases with the increase of the crack propagation velocity.(14)Process relative to the propagation of the crack can be divided into three stages:independent extension,repel each other,attract each other,eventually forming connections to form each other;Crack propagation speed increase sudden when the crack interact in the process of the extension of crack,and the two horizontal distance of the crack tip decreases with the increase of crack initial vertical distance when the crack propagation speed increase;With the change of the two crack initial vertical distance,the two cracks begin interaction when the crack tip on the between 56～70mm;The largest vertical migration distance of crack position corresponding to the crack tip horizontal distance of zero moment,resulting from relative movement between two initial crack spacing in the vertical direction of the greater the offset distance,the smaller instead.(15)In respect of sectional cut blasting in vertical Wells,the hole utilization rate is 81.7%and the single consumption of explosives is 3.53kg/m~3 for continuous charging in cut holes.The average footage of blasting in the upper section of the cut hole is 5.5m,the utilization rate of the shot hole is 91.7%,and the single consumption of explosives is 3.14kg/m~3.Compared with the continuous charging,the utilization rate of the shot hole is increased by 10.0%,and the single consumption of explosives is reduced by 11.0%.From the lifted gangue heap,it can be found that the segmented charging rate of cut hole is less,which improves the gangue removal efficiency.There was no obvious half-eye mark on the common charging side around the shaft,while on the side of slot-filling packaging,due to the release of explosive energy along the slit direction,a smooth section was formed around the gun hole,and the half-eye mark rate of the gun hole was82.3%.(16)By comparing the acoustic wave test values of common charge and slit charge around the shaft before and after detonation,it is concluded that the acoustic wave variation area of common charge side is 2.4m hole depth(1.2m perpendicular to the shaft wall),the maximum damage degree of the shaft wall is 0.176,and the total damage value of each measuring point of wall surrounding rock is 0.8982.The acoustic wave variation area on one side of the slit charge package is 1.6m hole depth(0.8m perpendicular to the shaft wall),the maximum damage degree of the shaft wall is 0.104,and the total damage value of each measuring point of the shaft wall surrounding rock is 0.4759.The damage range of shaft wall rock with slit cartridge was reduced by 33.3%,the maximum damage degree of shaft wall was reduced by42.2%,and the total damage value of shaft wall rock was reduced by 47.0%. |
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