| The goaf is the underground cavity formed by artificial underground mining or geological tectonic movement. It has such characteristics as strong insidious characteristic, spatial distribution regularity of anomalies, unpredictable collapse of the roof, and it considered to be one of the major hazardous sources to cause accident in open pit mining. Therefore, precise detecting for unknown underground goaf is of great significance in order to ensure the safety production of opencast working.Three-dimensional laser scanning detection technology combined with drilling technology in cavity monitoring has been applied successfully in the world, but there are still many problems in multilayer cavity drilling field to be solved yet. Reverse circulation drilling technology with hollow-through DTH hammer can be used in multilayer cavity drilling, meanwhile a C-ALS 3d laser scanner will be sent to the cavity to detect accurately. Reverse-circulation drilling bit is the key to the formation of reverse circulation in reverse circulation drilling system with hollow-through DTH hammer, and it should suffer the impact from the piston and transmit the stress wave to rock mass to fracture it.Drilling a multiple cavity, the rock slag crumbs at the bottom of the bore can be brought into double-wall drill pipe center channel by the unique fluid channel of reverse circulation drill bit and through the reverse circulation return to the surface, so the drilling break does not affect the normal drilling. At the same time, dedicated reverse-circulation bit should meet the lowering requirement of C-ALS 3d laser scanner in case it blocked. For this reason, in the multilayer cavity detection technology, dedicated reverse-circulation bit should have good reverse circulation effect, strong impact resistance and meet the process requirements and capabilities, laying the foundation to solve multiple cavity detection problem.According to dedicated reverse-circulation bit for YuanJiaCun iron ore mine multi-layer cavity detection project, the slipper type reverse-circulation bit is developed. The structure of the bit is designed including a large diameter center channel structure, double row of inner nozzles structure and slipper structure which is used in reverse-circulation bit for the first time. Therefore, further research on the reverse circulation mechanism and stress distribution of the slipper type reverse-circulation bit is extremely important for the performance stability of drilling tool system.First of all, orthogonal design experiment of fluid channel in the new slider block reverse circulation drilling bit and CFD numerical simulation experiment were carried out.Wthin the center channel diameter D2, double row inside nozzle diameter D1, dip Angle θs and deflection Angle θd of four factors in orthogonal experiment, observing the effect of the factors on the external ring suction volume Mh, it is concluded that the factors of primary and secondary order and significant level through range analysis and variance analysis, and then the optimal solution is going trend analysis through trend diagram; Analyzing the effect of the center channel diameter and double row inside nozzle holes diameter on the influence regularity of external ring suction volume through CFD numerical simulation, which is in order to get the optimal solution. stress analysis for slider block reverse circulation bit body through ANSYS ls-dyna, and going structure optimization design of slide block structure, optimizing the best sliding block structure is in order to meet the drilling construction requirements, which is providing reliable theoretical basis for the subsequent physical design of the bit.Secondly, observing the operational performance of sliding block reverse circulation bits through drilling experiment, the results of the reverse circulation is better, the drilling efficiency is higher, the average drilling efficiency of very broken stratum and hard stratum can reach 33.75 m/h and 10.17 m/h respectively. Taking the slider block reverse circulation bits can effectively solve the problem of the center channel blockage, and slider structure is meeting the requirement of drilling construction. Successful drill through the multilayer cavity, and through the center channel achieving C-ALS of 3d laser scanners which can solve the problem that multilayer cavity drilling and scanning are operating together.Finally, in order to further improving the effect of reverse circulation, this paper puts forward two new reverse circulation structures that the narrow seam inside nozzle structure and the groove inside nozzle structure, and through the numerical simulation analyzing the flow field and the stress field of two kinds of reverse circulation structures, and providing reference and guidance for subsequent reverse circulation structure optimizing... |
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