| With the continuous progress of the society,there are new demands on the quality of development and People want to work and live in a safer and more environmentally friendly situation.Some extensive development modes which have great impact on the environment need to be transformed urgently.In the field of blasting,detonators and explosives are widely used as blasting equipments.But the excessive use of detonators and explosives for blasting has many negative effects,such as harmful gases,dust pollution,flying rocks,vibration damages,noise,etc.None of these damages,which have a negative effect on the surrounding area,can be eliminated.In order to avoid the use of explosives as much as possible while achieving the corresponding effect,a rock-breaking method without explosive is proposed in this paper and the feasibility of this method is confirmed.The main idea of this method is described as follows.High-pressure gas jets and shock waves,which from deflagration reaction of the energy bar consisting of aluminium fibres and ethanol in a closed tube,impact on surrounding rocks,and then cracks appear in rocks and continue to expand and penetrate.This will break rocks.Some basic works about the new rock-breaking method have been done in this paper.The shock tube for rock breaking is designed according to this new rock-breaking method and design details and instructions for use are given in this paper.The formula for calculating the safe reaction pressure in the shock tube for rock breaking is given.This formula is obtained through the dynamic load factor method.According to this formula,when the inner radius a=0.011 m and the outer radius b=0.0185 m,the safe reaction pressure is 113.7 MPa.Pre-calibrated strength checks can ensure the safety of the experiment.In order to analyze the effect of aluminum fibers on rock-breaking,both theoretical and experimental methods are used.Two theoretical models are used in this paper,including fixed capacity adiabatic combustion model and CJ deflagration model.Both models suggest that moderate amount of aluminium fibres helps to enhance the rock-breaking effect and the reaction product pressure increases and then decreases with the increase of the molar ratio of aluminum fiber ethanol.The best ratios obtained from the two theoretical models are 0.485 and 0.719,respectively,and the experimental fit shows that the optimal ratios is 0.492.All things considered,the best values for the molar ratios of aluminum fiber ethanol is about 0.3 to 0.8,which can be further optimized to be 0.485?0.492.These results provide guidance for the use of shock tube for rock breaking.At last,some cement mortar samples are used to test the actual rock breaking ability of this method.According to the experimental results,the sample 1 was broken under the condition of 1.0 g of aluminum fiber,10.0 mL of ethanol,and 1.0 MPa initial oxygen;the sample 2 and 3 were broken under the condition of 2.0 g of aluminum fiber,15.0 mL of ethanol,and 2.0 MPa initial oxygen.There were four major cracks along and perpendicular to the connecting line of the outlets in sample 2 and 3.The cracks were extended under the action of high pressure gas,causing the samples to break.Both lumpiness and fragmentation of the samples are good. |
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