Study On Blasting Quality Optimization Of Open Pit Mine On Rock Hardness Identification While Drilling

Blasting is one of the most important links in the process of open-pit mining,and the quality of blasting has an important impact on the mining cost.At present,when designing blasting parameters,the judgment of rock hardness is often based on the large-scale formation lithology analysis provided by the geological survey report.However,due to the complex and changeable geological conditions of the mine and the diversity of rock types,the blasting parameters can not be designed accurately,resulting in the poor blasting quality.In this paper,through the combination of theoretical analysis,laboratory test,field experiment and numerical simulation,the blasting quality optimization problem based on rock hardness identification while drilling is systematically studied.The rock hardness identification model based on the working parameters of drilling machine is established by combining indoor test and field test;On the basis of rock hardness identification while drilling,the blasting parameter design scheme is optimized;Based on the results of rock hardness identification while drilling,a numerical model is established by using PFC numerical calculation software to simulate the blasting effect under various blasting parameter optimization schemes.Through the proposed blasting quality evaluation model based on the minimum comprehensive cost of rock stripping,the blasting quality under various blasting parameter optimization schemes is analyzed and evaluated.The main conclusions are as follows:(1)By analyzing the design method of blasting parameters and the rock breaking process and mechanism of bench blasting in open-pit mine,the variation rules of blasting parameters such as explosive consumption,hole row spacing,ultra deep length and packing length with rock hardness are obtained.It is clear that rock hardness is the basis of blasting parameter design,and accurate identification of rock hardness is the premise of reasonable design of blasting parameters and improvement of blasting quality;The cost of drilling,blasting,shovel loading,transportation and crushing in rock stripping engineering is calculated by using average block size and big block ratio.The variation law of comprehensive cost of rock stripping with average block size and big block ratio is obtained.The evaluation model of blasting quality is established based on the minimum comprehensive cost of rock stripping.(2)Based on the analysis of drilling process and rock breaking mechanism of1190 E cone drill,the variation rules of axial compression and torque shear stress on rock with the feed pressure,rotary pressure,drilling speed and rotary speed of drill are obtained.The four drill parameters are determined to represent rock hardness,and the working parameter acquisition system is established to collect the four drill parameters On this basis,the rock hardness identification model is established.(3)BP neural network is used to establish a rock hardness identification model,which takes drilling parameters as input vector and rock Proctor hardness coefficient as output vector,and contains two hidden layers and each hidden layer contains eight nodes.Laboratory tests show that the absolute error and relative error of rock hardness identification model meet the accuracy requirements of judging rock hardness,and can be used for field rock hardness measurement Through the field test in open pit mine,the distribution of rock hardness in the flat strata to be blasted is obtained,which provides the basis for the subsequent blasting quality optimization.(4)Based on the rock hardness identification while drilling,PFC2 D numerical calculation software is used to simulate and evaluate the blasting effect of the blasting parameter design scheme and the blasting parameter optimization scheme proposed in this paper,and the explosive unit consumption value which makes the rock stripping cost the lowest is obtained.It is found that the blasting quality can be guaranteed and the explosive unit consumption can be effectively reduced by using the subsection charging method.This paper has 94 figures,28 tables and 79 references.