Research On Size Effect Of Empty Hole In Horizontal Roadway Cut Blasting & Accumulating Characteristic Of Surrounding Rock Damage Caused By Frequently Blasting Vibration

Tunnel has often been applied in the construction of railroad andhighway in certain conditions to abridge mileage, advance work benefitand escape from disaster. A lot of laneways are needed in all kinds ofmines to constitute product system. The amount and total lengthen oflaneway or tunnel account for largish ratio in the building of railroad,highway, hydraulic power plant and mine.Excavation of laneway or tunnel and surrounding rocks stability arethe two main problems to be solved in the construction period. Drillingand blasting will still be primary method applied to excavate laneway ortunnel in the far future. Laneway or tunnel with medium or small fracturesurface accounts a great amount in all kinds of mine. Excavationefficiency and scale of surrounding rock relaxation not only affect cost ofexcavation and timbering, but also have great effects on the production ofmine. Parallel-hole blasting is effective technology approach to improvesingle cycle footage in medium and small fracture surface tunnel orlaneway. A lot of researches have been done on parallel-hole blastingtechnology and rock damage characteristic resulted from blastingvibration by the scholars from home and abroad. However, no substantialevolvement has been gained in the studies of parallel-hole blasting withbig empty hole and surrounding rock damage characteristic resulted fromcontinually blasting vibration. Therefore, the design of parallel-hole withempty hole and the plan of timbering have been still stick to be guided byblasting engineer's experience.Based on the practice of the excavation blasting of medium or smallfracture surface laneways, this paper is entitled as "Research on sizeeffect of empty hole in horizontal roadway cut blasting & accumulatingcharacteristic of surrounding rock damage caused by frequently blastingvibration". The effect of empty hole and the cut model of parallel-holeblasting have been systematically studied. Based on micro damagemechanics theory, the accumulating damage characteristic under theaction of cycling blasting has been researched through blasting vibration experiment and simulation cycling bump experiment. The energydistributing with frequency of blasting vibration-testing data has beenanalyzed in virtue of wavelet packet method. The surround rockrelaxation field-reaming characteristic affected by cycling blastingvibration has been studied by testing on the spot in term of velocitysurvey instruments. The main outcomes are as follows:(1) The maximum stress distributing between cut hole and emptyhole increases with the diameter of empty hole raised. The 3rd couplingstress field in rock caused by cut hole charge detonation and secondarystress field is affected greatly by initial stress. Method to determine thebest optimization space between cut hole and empty hole has been given.Definition of "rebirth rock coefficient" has been concluded.(2) An analysis model of cavum formed by cut holes blasting hasbeen established. Assessment method of the ratio of shiver shot off emptyspace has been supplied and testing on the spot proved its rationality.(3) Response of material to cycling blasting vibration existsaccumulating effects. The deteriorating trend will be strengthenedgradually when the action times increases if blasting vibration forceoverrun threshold value. The damage characteristic of material caused bycycling bump is affected by the surround stress acting on the material.Formula to estimate critical vibration velocity of original cracksspreading and method to determine crack-spreading length under theaction of certain blasting vibration has been given, respectively expressedas formula 4-80 and 4-81. A cycling blasting vibration damageevolvement model expressed as formula 4-86 and 4-87 has beenestablished based on micro-damage-mechanics theory on crack spreadingaccumulating.(4) The energy of blasting vibration will main centralize on higherfrequency stage if we choose larger empty diameter or less maximumcharge quantity detonate simultaneously. The frequency ratio weightingequivalent energy analysis method has been given for the first time basedon wavelet packet energy distributing in frequency theory.(5) Scale of surrounding rock relaxation can be divided into twoaspects. One is called surrounding rock relaxation caused by shape and size of tunnel or laneway; another is called surrounding rock relaxationformed by blasting vibration. Surrounding rock relaxation is affected byblasting vibration through two ways. At first, blasting vibration may bemake rock adjacent to out-border of surrounding rock relaxation rupture,secondly, blasting vibration may be do damage to the rock innersurrounding rock relaxation, as a result, the gather stress field will spreadto out of border and enlarge surrounding rock relaxation. Method thattesting blasting vibration velocity has been modified based on frequencyweighting has been supplied originally. The method was used to estimatedamage degree of rock inner relaxation field, and the results accords wellwith data from survey on the spot.The outcomes of the research have been applied to determineparallel hole with large empty hole and blasting parameters in the blastingof haulage water laneway. Large footage was got in small fracture surfacelaneway, and the affecting degree of blasting vibration to surroundingrock was controlled effectively. The haulage water laneway has beenworking for over a year without any problem. The project proved thefeasibility of results form the research.