Micro-vibration Blasting Control Technology Of Multilevel Wedge-cutting

In the tunnel construction by drilling-blasting method, the blasting vibration is inevitable in the construction process, which not only threatens the safety of the surrounding buildings, but also endangers the health of the residents.How to reduce the blasting vibration as far as possible without affecting the construction efficiency or little influence on the construction efficiency has become the main problem to be solved in the tunnel blasting construction.In order to reduce the blasting vibration on the surrounding buildings in construction of subway station disturbance, and improve the blasting efficiency of construction, the paper is based on Qingdao Metro Line 2 in the first phase of the construction of 01 Yanan Road Station near buildings with blasting construction as the background. Under the strick demanding conditions of building to blasting vibration, the paper from two aspects of theoretical analysis and field test studies damping mechanism of multilevel wedged-cutting, effects of different cutting blasting parameters on vibration of surface buildings, weight of influencing factors of blasting vibration in cutting blasting and the effect of free surface and minimum resistance line on tunnel blasting vibration. Then the research results are used to blasting construction of subway station.Not only the blasting vibration speed is controlled in the range of the design, but also the construction efficiency is improved, and the construction time is guaranteed.The main research conclusions of this paper are:(1) Damping mechanism of multilevel wedged-cutting can be analyzed from two aspects of the single maximum ignition charge and the numbers of free surface.(2) Multilevel wedged-cutting has better vibration damping effect in the blasting construction of shallow buried excavation tunnel close to existing building.It is better than the large-diameter empty-hole parallel cut in aspects about borehole density, blasting vibration control, hole utilization rate and the consumption of explosive and detonator.The second stage and third stage cut hole of multilevel wedged-cutting with hole by hole initiation has obvious damping effect.In the case of hole depth 1.1m, single hole charge 0.3kg,the peak vibration velocity that is generated by cutting hole by hole initiation can be reduced by 67.5%than cutting pair initiation.At the same time cutting hole by hole initiation will not reduce the utilization rate.(3) Strict control of blasting vibration should be selected to three or more multilevel wedge-cutting; Blasting hole inclination angle of at all levels from low level to high level increases gradually;Third level cutting hole depth should be greater than the other cutting hole;The first level and the second level cutting, the second level and the third level cutting the spacing should not be more than 0.4m; The number of second level cutting should serve as five pairs,others on the four; Hole at the saIme level cut holes should be used in the first post on both sides of the initiation sequence; Minimum time interval should be more than 25ms;The above measures can achieve a better effect of vibration reduction.(4) Using grey relational analysis method and the field measured data as the sample, combined with MATLAB program calculation,getting the multilevel wedge-cutting the importance order of blasting vibration controllable factors, from high to low as follows: the cutting area than second drilling, cutting the single maximum ignition charge,the first cut single maximum ignition charge, second cuthole hole depth,hole depth third cuthole, Underholing series, third slot single maximum ignition charge, the cutting hole blasting sequence, the minimum time interval.(5) The blasting vibration is effected by the free surface and the minimum resistance line. In the distance from the explosion center,single largest initiation same amount and the number of free surface and free surface quantity more, in tunnel ramp at the top of the particle vibration intensity is small; The same number of free surface and the direction of the line of least resistance and particle vibration intensity is different, which minimum resist line vertical upward, particle vibration intensity minimum; Particle vibration intensity is also related to the size of the minimum resistance line. Under the same conditions, the minimum resistance line is large, and the particle vibration intensity is also large.Conclusion of this research could provide references for the construction of similar projects.