Study On Flow Field And Rock Carrying Efficiency Of Foam Washing In Vertical Shaft Boring Machine

With the development of the national economy and the increase in the depth of mining of mineral resources,the deep shaft drilling technology has faced increasingly difficult technical problems in power transmission,shaft stability,and shaft wall sinking.Research on construction technology of shaft boring machine.In the shaft drilling method,the cuttings under the working face are easy to accumulate in situ,and it is difficult for the anti-gravity to move upwards.It is easy to cover the working face and cause repeated crushing,which affects the speed and efficiency of rock breaking and even the entire drilling.In view of this,in view of the shortcomings of the existing fluid well washing and mechanical slag discharge methods of the shaft boring machine,and the mud preparation difficulties that the shaft boring machine construction may face in areas such as drought and water shortage,the paper proposes the foam boring technology of the shaft boring machine,Analyze and propose the basic parameters that affect the flow field of well washing,and then comprehensively adopt numerical simulation,model test methods and other methods to carry out the research of the flow field and slag discharge efficiency of the foam washing well of the shaft boring machine.First of all,in order to meet the needs of washing and discharging slag in large diameter deep wells,4 foaming agents and 3 foam stabilizer were selected to evaluate foaming capacity and stability.The well washing foam formulation PMXJ(0.8%K12+0.2%BS-12+0.1%CMC)was developed,and the relationship between viscosity,temperature resistance and stability of foam was mastered.The results showed that the viscosity and temperature resistance of the foam had a great influence on the stability.The viscosity of the foam could be increased by increasing the viscosity of the base fluid.The foam exhibited certain temperature resistance within the experimental temperature range(20～60℃),which could meet the engineering requirements.Through laboratory experiments,the factors that affect foaming performance of foam generator are explored.It is concluded that changing the flow rate of gas and liquid can increase the flow rate of foam,and increase the effect of gas flow.The gas-liquid ratio is not too large when foaming,and the range of gas-liquid ratio corresponding to different gas-liquid flow rate is also different.Secondly,using FLUENT,only considering the single-phase flow conditions,through a single factor analysis,the hardware parameters such as the angle between the cutter head and the bottom of the hole,the bottom hole clearance height,the inner diameter of the slag discharge tube,the jet port inclination,the jet port inner diameter,etc.The degree and rules of influence on the characteristics and parameters of the flow field(pressure,flow rate in the slag discharge tube and pressure,flow rate in the bottom hole,distribution of the overburden and coverage area,etc.).The results show that the influence of various factors on the flow field is not monotone linear,but there is a certain peak,and the parameters are mutually restricted;among them,the jet flow only affects the flow field in the slag discharge tube and has almost no effect on the bottom hole flow field.Based on the results of single factor analysis,the optimal parameters were selected,and the orthogonal test analysis was carried out for the factors with greater influence,which laid the foundation for the subsequent research on the efficiency of foam well washing and slag discharge.Then,based on the optimization of the hardware parameters of the foam well washing system,the cuttings are regarded as discrete phases to simulate the process of the cuttings generated from the bottom of the well and carried by the fluid to the wellhead.The slag discharge rate,cumulative rock load and cuttings discharge rate are The indexes were analyzed to study the influence of slag discharge height,foam viscosity,cuttings particle size,and foam flow rate on the slag discharge effect.The results show that the foam-carrying efficiency is almost unchanged when the slag discharge height is in the range of 10m-50m;the foam rock-carrying capacity is gradually unable to meet the requirements when the cuttings increase in particle size;the foam injection flow rate has a greater impact on the rock-carrying efficiency Flow rate can obviously improve rock-carrying efficiency.Foam viscosity has a certain effect on well-washing efficiency.Properly increasing its viscosity can greatly improve well-washing efficiency.However,if the viscosity is too high,the foam stability will decrease and the rock-carrying efficiency will decrease.Finally,according to the influence of various factors found in the numerical simulation on the slag discharge efficiency of foam well washing,under reasonable similar shrinkage conditions,a model test study on the slag discharge efficiency of foam well washing was carried out.As the core index,the effects of five factors,such as cutter head speed,foam flow rate,foam gas-liquid ratio,foam viscosity,and rock particle size,on the efficiency of foam slag discharge were investigated and the accuracy of the numerical simulation conclusion was verified.The results show that the slag discharge rate increases with the increase of the cutter head speed,but the cutter head speed should not be too large;the increase of the injected gas-liquid ratio within a certain range can effectively improve the slag discharge efficiency,and if it is too high,the slag discharge rate does not change significantly;Increasing the injection flow rate significantly improved the efficiency of slag discharge.After the flow rate increased to 4m~3/h in the test,the effect of increasing the rock-carrying rate gradually weakened.As the particle size of the cuttings increased,the mixed fluid velocity gradually decreased,indicating the foam’s slag-carrying capacity and The viscosity cannot meet the slag discharge requirement;as the viscosity increases,the slag discharge efficiency increases first and then decreases.When the foam stabilizer is added until the viscosity of the base liquid is greater than 17.5m Pa·s,the foam stabilizer has an inhibitory effect on the foaming ability of the base liquid The ability of the foam to carry rocks has dropped significantly.Compared with the previous chapter,it is concluded that the experimental results and the simulation results have a good fit,indicating that the numerical calculation results are reliable.