| The Ma Keng Iron Mine intends to adopt the method of stage-chamber backfilling mining,which requires higher stability of the bottom structure roadway than the general roadway.It is found through investigation that the existing scheme is to adopt secondary roof pressure for roadway construction,and the surrounding hole spacing is not uniform and not distributed on the same line,resulting in the explosion stress wave and detonation gas quasi-static pressure action cannot be on the same line,leading to the serious phenomenon of over-excavation and under-excavation.In the process of roof pressing blasting,in order to ensure that all the ore bodies in the roof pressing area caved down,a little more explosives were used,resulting in a large damage to the roof ore body.Under the action of frequent blasting vibration,large areas of the roadway had the phenomenon of banding and roof falling.And the large supporting range in the later stage increases the construction cost of roadway.The goaf of Ma keng Iron Mine is filled in different areas after ore drawing,and the service time of bottom structure is short.Because of the high cost of smooth blasting technology,it is obviously a great economic waste to use it.In this paper,the sub-smooth blasting technology is proposed on the basis of smooth blasting in order to meet the cumulative damage of medium deep and deep hole frequent blasting in Ma keng Iron Mine and reduce the support cost.(1)In order to meet the design requirements of technical parameters,on the basis of full investigation and understanding of the existing scheme and the performance of the explosives used in the mine as well as the drilling and blasting conditions,by combining theory with practice,blasting funnel experiments were carried out respectively in the magnet ore body and the rock-sandwiched ore body to calculate the optimal buried depth and the optimal proportional buried depth.It is found that the small structure has great influence on the explosive stress wave and the detonating gas,and the rock-containing ore body is more difficult to be exploded than pure magnetite.In this mine,the rock-containing ore body should be considered,and the mining method should be optimized rationally.According to the general charge structure of smooth blasting,the single consumption of the explosive should be controlled between 1.75kg/m~3 and 1.85kg/m~3,the minimum resistance line should be800mm?1300mm,and the hole bottom distance should be 900mm?1300mm,which is of certain reference value to the design of sub-smooth blasting parameters.(2)The cutting quality directly affects the smooth blasting effect and footage.In order to select the cutting scheme reasonably,the wedge cutting,straight hole cutting and composite cutting are tested on the spot respectively.The cutting consumables and cutting drilling are considered to select the suitable cutting method for the mine.It can be seen from wedge-shaped cutting that wedge-shaped cutting can form a good cutting cavity,and the explosive consumption and detonator consumption of cutting are also more than that of straight hole cutting,which is greatly affected by the roadway section.It is recommended to use wedge-shaped cutting in the excavation of large section roadway.In the straight hole cutting,when the integrity of the ore body is good and there is no obvious rock inclusion,it is suggested to adopt the"1+8"type straight hole cutting.In the presence of small structural fissures and rock inclusion ore body,it is suggested to adopt the"2+8"type straight hole cutting.The composite cutting method of blasting with four empty straight holes,one charging straight holes and two rows of symmetrical inclined holes has the advantages of straight hole cutting and wedge cutting,but it also has the problems of large amount of explosive and detonator consumption.In the process of drilling,the deviation rate is greatly affected by the turning workers.Therefore,the composite cutting method can be used in the ore body with complex conditions.(3)The layout experiments of cutting,auxiliary hole,secondary hole and contour hole are carried out to find out the reasonable location range of the holes.Among the three kinds of sub-smooth blasting schemes,the periphery holes of"1+8"49 holes and"2+8"51 holes should be evenly distributed with an interval of 800mm,while the spacing of ore drawing routes should be controlled within 600mm.In the initiation mode,the top hole and the side hole should be divided into two sections.In charge structure,27mm explosive shall be used,80mm shall be taken for the interval between"1+8"49 holes and"2+8"51 holes,and300mm shall be taken for ore drawing route.Only two smooth auxiliary holes are needed in weak rock mass such as ore body with good integrity or large physicochemical limestone,and three smooth auxiliary holes are needed in small structure of quartzite.Based on the technical and economic comparative analysis of the four blasting schemes,although the current scheme has a slight advantage in the amount of engineering drilling and the consumption of initiating materials,the blasting effect in the aspects of the regularity of the tunnel contour,the utilization rate of blast holes,the rate of blast marks and the control of surrounding rock damage is far from that of the three sub-smooth blasting scheme.(4)According to Sodev's formula,it is deduced that the ore body belongs to hard ore body,the four schemes are all within the range of safety standard,and the influence of blasting vibration on the stability of surrounding rock of roadway is within the reasonable range.Based on the analysis of wavelet packet energy,it is found that the damage of existing scheme to surrounding rock is more serious than smooth blasting.Combined with instantaneous energy spectrum analysis,the wavelet packet energy analysis shows that the amount of explosives used in the roof pressure area of the existing scheme has great damage to the roof,and the surrounding hole arrangement is not uniform,resulting in the joint action of explosive stress wave and detonating gas not on the same line,so that the half-hole rate of the existing scheme does not have the sub-smooth blasting technology.(5)It is further proved that the damage of sub-smooth blasting is smaller than that of the existing scheme by measuring the loose ring.The acoustic wave velocity curve shows that the existing test area is mainly affected by excavation,while the test area of"2+8"is greatly affected by the original joints of the rock mass.According to the theory of loose ring support,the existing scheme and"2+8"scheme need to be supported.Compared with the economic index of roadway construction,it is further verified that the sub-smooth blasting is better than the existing scheme. |
PDF Full Text Request