| The roadheader is the key equipment to the coal mine mechanization excavation,in the process of hard rock breaking, the conical pick bear great cutting force andwear, and the cutting efficiency is lower, footage cost increases, it has become animportant factor affecting China’s coal resources more productive. Thus, in order toimprove work efficiency of the TBM picks in the hard rock breaking process，basedon system dynamics performance and rock fragmentation theory of rock breaking bypick, studying rock breaking performance and configuration method of pick assistedwith high pressure water jet, which can solve the difficult problem of hard rockexcavation, improve the degree of mechanization mechanized excavation rate, andfinally realize the effective way of coal resources more productive. The theoreticalanalysis, simulation and experiment are combined to investigate the rock breakingperformance of conical pick assisted with high pressure water jet.Based on mechanical rock breaking theory and water jet impact rock breakingtheory in this paper, the cutting mechanism of rock fragmentation by the conical pickassisted with the high pressure water jet was researched, the rock breaking by pickassisted with water jet test bench was developed. The rock sample for cutting test isdeveloped by considering the compressive strength and density of the rock, and waterjet through the centre of pick, water jet place in front of pick, water jet place on sideof pick water jet place in back of pick were designed and processed.In order to verify the internal flow channel reliability of water jet through thecentre of pick and study damage of water jet impact rock, internal flow channel andwater jet impact damage model were analyzed in the simulation, the results indicatedthat alloy head nozzle structure design was reasonable, water jet impact damage wasmainly caused by shear failure and tensile failure, water jet impact crushing rocks aremainly concentrated in the bottom of the impact point, rock damage range below thepoint of impact is gradually increased with the water jet pressure increase.Four kinds configuration modes of pick assisted with water jet was built by usingSPH particles combined with FEA finite element method, dynamic process of rockbreaking and force of pick was analysed in different configuration mode, and theincidence angle of jet, impact pressure, distance between jet and pick bit, cuttingdepth was researched, achieve the rock tensile stress, compressive stress and stressreduction rate in the process of rock breaking. Based on simulation analysis of different configuration, experimental study offour configuration modes were conducted, the results indicated that rock breaking bypick assisted with water jet have a good effect, the force of pick decreased obviousely,compared to the reduced rate of four configuration modes, it showed that water jetthrough the centre of pick was the best, followed by water jet in the back of pick, thethird was water jet in the front of pick, the last was water jet on side of pick. But thewater jet in the back of pick had some problems such as nozzle wass easy to damage.It also indicated the simulation models were correct, rock breaking properties of pickassisted with high pressure water jet was achieved in different configurations, andprovides reference basis for rock breaking of pick assisted with high pressure waterjet. |
