| During the process of obtaining material yard in material field excavation of water conservancy and hydroelectric dam,the improvement of rock excavation and reduction of natural and environmental disturbance are of great significance to the environmental protection in the vicinity of the material field.The way to realize good dam material grade in the damming has become a key technical problem during the process of the blasting excavation of material field.And the blasting block distribution of rock mass based on material grade is also of very important research significance and practical value.In this paper,aiming at the research object of hydraulic rock fill dam grade,the methods of theoretical analysis,numerical simulation based on LS/DYNA-DDA and field measurement are adopted to study the prediction model of strain rate-block sieving and the whole process of bench blasting,and the main conclusions are as follows:(1)Based on the rock breaking mechanism and process of bench blasting,the selection method of bench factors and main parameters is mainly demonstrated,and the prediction model of rock blasting fragmentation can be divided into four categories: distribution function model,stress wave model,energy model and fractal model,and the models are analyzed.The influence factors to the shape of blasting heap are compared,and the method of measuring the bulk of the slag is studied.(2)The production mechanism and theoretical determination method of small bulk material are discussed,and the factors that affect the radius of the crushing zone are determined.A numerical simulation method based on the strain rate block sieving model is put forward,which is verified by the example of the Lianghekou and Changheba Hydropower Project,and the results are combined with the results of the field screening.By comparing the simulation method with the KUS model,the rationality of the new prediction method is verified.On this basis,the factors such as the rock mass structure surface,the elastic modulus of rock and the uncoupling coefficient of charge are analyzed.(3)The bench blasting under the condition of different blasting spacing is simulated by DDA,and the reasonable distance between the front and back gun holes is determined,and the necessity of increasing the explosive charge at the bottom of the hole is verified.The model of the ballistic theory of DDA bench blasting is set up,the results of the model are compared with the theoretical results,and the final static distance after the block landing is supplemented,and it is proved that it is feasible to give the initial velocity value to the block in the DDA model.Compared with the unstructured surface model,the anti-propensity surface parallel to the front row resistance line is not favorable to the engineering blasting.(4)The rock bench blasting area can be divided into two parts of the near area and the middle and far area.According to the analysis of the block distribution in different regions,it is found that the size of the grade less than 5mm mostly emerged in the near area,and the size of the block in the middle and remote areas is larger than the size of the 5mm.And on the basis of exploring the characteristics of the numerical simulation,LS-DYNA is used to simulate the failure process in the near area when blasting is used to obtain dam level batching,the DDA is used to simulate the breaking-up,throwing of burst blocks and formation of blasting heap in the middle and far reaches.The velocity peak at the outer boundary of the LS-DYNA model of the near area is extracted and is loaded on the middle and remote region of DDA model.The fine numerical model of the whole process of the step blasting based on the LS/DYNA-DDA coupling is established and verified,and the evolution process of the explosive pile formation is analyzed. |
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