Study On Rock Cuttability Improvement And Application In Deep Hard Rock

With the advantages of high efficiency,low disturbance and high construction quality,mechanical tool rock breaking overcomes some drawbacks of drilling and blasting method,and is more suitable for deep ore body mining under high geo-stress.However,hard rock has high integrity and strong corrosion resistance.It is difficult to use mechanical tools to break hard rock,and the tool wear is serious,which affects the mining efficiency.In order to efficiently apply mechanical cutting tools to deep hard rock mining,it is necessary to improve the cutting characteristics of hard rock and reduce the difficulty of breaking deep hard rock.In this paper,through the TRW-3000 test platform,the rock fragmentation experiments using conical pick under different confining pressure,cutting parameters and rock defects is carried out.The peak cutting force,insertion depth and specific energy are used to characterize the rock cuttability,and the effects of confining stress,cutting parameters and rock defects on the cutting characteristics of hard rock are explored.In the rock fragmentation experiment using conical pick under uniaxial confining stress,with the increase of uniaxial confining stress,the rock cuttability first decreases and then increases,and the rock failure mode changed from splitting failure to slabbing failure accompanied by high-speed ejection of fragments and loud sound.In the multiple rock fragmentation experiment,with the increase of cutting depth,the peak cutting force,insertion depth and cutting work also increase,while the specific energy first increases and then decreases.Comparing the results of the multiple rock fragmentation experiment and the single multiple rock fragmentation experiment,it can be seen that the multiple cutting will destroy the integrity of the rock,and the fracture surface formed by the rock fragmentation will affect the next cutting together with the original free surface of the rock,which improve the rock cuttability.For the rock samples with defects,it is found that defects such as drilling holes and cracks can improve the rock cuttability,which is conducive to the development,expansion and penetration of cracks in the rock.Therefore,the hard rock cutting characteristics can be improved by changing the stress condition of the rock,designing reasonable cutting and breaking parameters,and artificially prefabricating defects.The peak cutting force directly reflects the rock cutting characteristics.Researchers at home and abroad have established a series of peak cutting force prediction models,but these models are mostly two-dimensional models.In various rock fragmentation experiments using conical pick,it is found that the magnitude of the peak cutting force is directly related to the size of the fracture surface.Therefore,according to the experiment results of rock fragmentation without confining stress,a semi-elliptical cone fragment model is established,and a peak cutting force prediction model is established according to elastic fracture mechanics.Comparing the experimental value and the predicted value,the error is only 3.8%,which shows the accuracy of the prediction model.Combined with the fitting formula of peak cutting force under different confining stresses,the prediction model of peak pick force under different confining stresses is obtained.In the field application of non-explosive mechanized mining using a high-frequency impact hammer,the thickness of the excavation damage zone is in the range of 1.92-3.41 m,with an average thickness of 2.59 m.In the field application,the mining efficiency of high-frequency impact hammer was 50.6 t·h^-1,and the mining efficiency of the upper ore body after excavating the stress relief slot can reach 158.2 t·h^-1.At the same time,the non-explosive mechanized mining using high-frequency impact hammer also showed the advantages of high utilization rate of working hours,small lumpiness of spalling ore,less mining dust,stable roof,and less excavation damage.It can be seen that non-explosive mechanized mining using high-frequency impact hammer can meet the needs of deep mining,and excavating stress relief slot can change the stress condition of the upper ore body,create free surfaces,provide compensation space,which will improve mining efficiency.However,in the field application,it was also exposed that the mechanical tool is easy to wear when breaking hard rock,which affects the mining efficiency.Finally,based on the results of rock fragmentation experiments and non-explosive mechanized mining field application,the non-explosive mechanized mining equipment,mining method and mining mode are conceived from the two aspects of improving rock cutting characteristics and improving the rock breaking capacity of mining equipment.