| High-pressure jet grouting, an important kind of waterjets technology application form, is comprehensively used for many different purposes, such as increasing the bearing capacity, creating water cuff-offs supporting open and underground excavations,strengthening coal mine safe and efficient mining and preventing coal and gas outburst, There is extensive influence the performance of high-pressure water jet by the double-side wall vertical confined region created by itself, Nevertherless, Research interest never focused on this structure dynamic characteristics and flow-field structure.In this thesis, Evaluation parameter system was investigated by studying the turbulent theory Then, Double-side wall vertical confinement construction is established to study the high-pressure turbulent round jet discharging from a circular nozzle into submerged water region. Specifically, the focus was on identifying changes in the mean flow, votices structure, turbulent intensity, Reynolds stress and flow-field structure, The principal parameters are Reynolds number, vertical confinement depth and swirl number. The axial and lateral confinement were negligible. In CFD simulation, Reynolds stress turbulent model was used to calculate the construction flow behavior. Particle image velocimetry (PIV) was used to investigate the flow and to validate the simulation model, Measurements ware taken on two orthogonal plane along the jet axis; one parallel and one perpendicular on the double-side wall. The frequency rate of acquired image pairs is14.5Hz using a1600pixels×1200pixels camera. In addition, It was dicussed that using high-pressure jet grouting to sloving the problem of coal and gas outburst in strenghening coal efficient mining.The main discussion results are as follows:(1) High-presuure jet-grouting cutting in coal seams is simplified and double-side wall vertical confinement construction and paramters is established to research the flow field. CFD simulation method and flow parameters is also introduced. Particle image velocimetry is used to diagnosis the relatively low Reynolds number double-side wall vertical confinement construction dynamic characterstics and flow-field structure to validate robustness and reliability of CFD calculating model. (2) Based on the Reynolds stress turbulence model,the relativley high Reynolds number, double-side wall vertical confinement construction and swirl number were numerical simulated to investigate the flow-field beheaviour. The principal parameters are Reynolds number, vertical confinement depth and swirl number. The results show that the high-pressure confinement flow changes from free jet to wall jet via transition region, where the flow turbulent features transfer from vertical dirction to transverse direction, resulting in a local negative pressure zone at neighbouting of the vertical double-side wall, In the region of free and wall jet, the flow always became similar to their own behaviours. The double-side wall vertical confinement construction always has effect on mean flow, votices structure, turbulent intensity, Reynolds stress etc., but influent characteristics are imparity in separated region. Reynolds number affects dynamic characterstics and flow-field structure in transition region while the other two region of free and wall jet is no effect. The vertical confinement depth do not impact whole beheaviours and flow-field structure in double-side wall vertical confinement construction, however, it induces an space hysteresis effects which changes the location of transition region moving downstream when the vertical confinement depth increasing; Swirl number mainly modifies the dynamic property distribution and also changes flow-field structure simultaneously. Additionally, various intensity vortices appears in the outlet region changes flow-field structure and dynamic characterstics.(3)Based on fluid transient theory and experimental method, Transient process of high-pressure jet-grouting system is investigated for keeping safety of construction in scene.Prediction method for system parameters of the transient process and validation of the method predicting results, The results shows that high-pressure jet-grouting system transient characteristics is relavent to structure and parameters of execution units.(4) Prediciton method for high-pressure jet grouting cutting radius in coal seams is established form the flow field characteristics and coal flagmentation rules. Depending on principle of experiment design, Uniform design method is employed to design experiment, which validate the rubustness and credibility of prediction method. Results shows that high-pressure jet-grouting cutting radius is in proportion to nozzle radius, and also in proportion to jet pressure's quarter power.(5) Complete sets of high pressure jet grouting cutting equipment, which is fitting for low permeability of coal seam gas control, is developed and applied to F15-24080coal field in10th mine of Pingdingshan. Cutting radius in scene is studied and also validated the prediction method of high-pressure jet-grouting cutting radius.Results shows that using high-pressure jet-grouting cutting slotting technology could reduce the amount of drilling, shorten the drilling time of construction and improve the efficiency of construction, Compared with the ordinary drilling, the gas concentration increased significantly and attenuation rate is very slow,and flow rate is also changing little, In the extraction of4months, slotted gas extraction from scalar is up by more than three times. Using high-pressure jet-grouting cut slotting technology to gover gas in low permeability coal mine can reduce gas drainage concentration rate, increase the speed of gas drainage, significantly improve the efficiency of gas extraction.(6)The high-pressure jet-grouting slotting system is also employed in B11b coal field of Xieyi mine of Huainan. Results shows that gas drainage discharge is up by more than30%compared with other method. After slotting within60days, the single slotting borehole's draninage gas concentration most remain at around90%. Compared with the ordinary drilling, single borehole's draninage gas concentration reduce slowly. The high-pressure jet-grouting slotting method can achieve fast eliminating coal and gas outburst. |
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