Research On The Technology Of Hard Rock Tunnel Parallel Cut Blasting

This thesis focuses on the problems in hard rock tunnel blasting,such as difficult drilling,difficult blasting,small blasting footage,low speed,low efficiency,etc.Through the study of rock blasting theory and the mechanism of parallel cut blasting,and according to the special construction conditions of hard rock tunnel blasting with small cross-section,the nine-hole rhombic stage delay parallel cut blasting by middle charge has been designed.Then the main factors affecting parallel cut blasting are studied by field test and numerical simulation,and the research results are used to optimize the original cutting plan.The optimized cutting plan is applicable and reasonable,which have well groove cavity,clean cutting groove and perfect cutting effect,besides,the residual hole phenomenon is gone.The optimized design can be used in military tunnel blasting and contribute to the rapid excavation of hard rock tunnel,and it has high practical value in the military.(1)According to the theory of explosive detonation,the rock blasting theory and the attenuation law of blast stress wave in rock mass,the radius of crushing zone and fracture area of rock blasting which blasthole diameter is 40 mm and charge diameter is 32 mm by non-coupled column charge are calculated.The calculation results are as follows: the radius of crushing zone,fracture area and damage area are 52 mm,177mm,249 mm,respectively,while the simulation results are are 60 mm,180mm,260 mm,respectively.The simulation results are in agreement with the theoretical results.(2)The simulation results show that the cut blasting by middle charge can make full use of the explosive energy to break rock,reduce the amount of explosive,and can optimize the groove cavity molding.But for the hard rock tunnel,the middle charge should not be used,while the full-hole charge is effective.(3)The spacing between charge holes has an important influence on the blasting effect.In this paper,I put forward that the spacing of the charging hole is slightly larger than 2 times of the radius of crushing zone,and smaller than the radius of fracture area.This method can effectively avoid the residual holes phenomenon caused by too large spacing and “squeezing dead” phenomenon caused by too small spacing.