Study On Liquid Cleaning System And Flow Field Of Vertical Shaft Boring Machine

With the development of the national economy,the depth of resource exploitation is getting larger and larger.Vertical shaft development is the most important development method for deep solid mineral resources exploitation,and deep shaft construction is its primary link.As a highly mechanized shaft building method,drilling method faces more and more difficult technical problems as the well depth increases.Under this background,the full-face shaft boring machine technology is highly valued in China and abroad,and related research is carried out.In the construction process of full-face shaft boring machine,well washing and discharging slag has always been a key technical problem which is difficult to solve.To this end,this thesis proposes a liquid cleaning system suitable for full-face vertical shaft boring machines,and through numerical simulation and model test methods,the hardware parameters optimization of the well washing system and the change law of the well flow field are successively carried out the study.Firstly,aiming at the key technical difficulties faced by vertical shaft boring machine for washing well and slag discharge,the research puts forward a more targeted and applicable well washing and slag discharge scheme for liquid cleaning: it can accommodate a certain pressure by adding a sealing disc at the heading of the shaft boring machine.The sealing chamber of the well washing liquid;the radial flow velocity of the drilling fluid is increased by adding a radial jet on the cutter head;and the return flow rate of the drilling fluid is increased by providing a jet flow in the slag discharge pipe.Based on this scheme,a simplified model of the well washing system was established and the parameters affecting the washing flow field were analyzed.Secondly,the pure flow field numerical model is used,and the distribution pattern of cross flow layer and the energy loss of the system are taken as the main evaluation indexes,carries out the optimization research on the shape of the cutterhead,the clearance height at the bottom of the well,the parameters of the jet port and the parameters of the jet port,and obtains the appropriate parameter combination of the well washing system,which lays the foundation for the follow-up study.Then,based on the fluid-solid coupling model,the influence of the density,viscosity and flow rate of the drilling fluid on the well washing effect was studied based on the main evaluation criteria of the rock carrying rate and the rock clearing rate.The research shows that the density of drilling fluid is linearly positively correlated with the rock clearing rate.The rock carrying rate is also positively correlated with the density of drilling fluid,but the growth rate is slow.The flow rate of drilling fluid is positively correlated with the rock clearing rate,but the growth rate is gradually increasing,and the rock carrying rate law is the same;the viscosity of the drilling fluid on the rock clearing rate and the rock carrying rate are increased with the increase of viscosity,and the rock clearing rate and rock carrying rate are first decreased and then increased.Finally,the simulation test bench of the full-face shaft boring machine liquid washing system was designed,and the influence of the drilling speed and flow rate on the well washing effect was studied through the model test rig.At the same time,the results of physical simulation experiments are compared with numerical simulation results to test the reliability of numerical simulation and physical experiment results.The research shows that the rock clearing rate and the rock carrying rate increase with the increase of rotational speed,but the increase rate is gradually reduced;the rock clearing rate and the rock carrying rate are the same as the flow rate.When the physical simulation speed is 4r/min and the flow rate in the slag discharge pipe is 1.4m/s,the bottom cuttings can be completely taken out.In addition,the influence law of the flow rate on the rock carrying rate and the rock clearing rate in the physical simulation is consistent with the law obtained by numerical simulation;under similar working conditions,the error of the rock carrying rate and rock clearing rate is about 30%,and the result is considered reliable.