Study On Design And Process Optimization Of Wet-Shotcrete Unit In Coal Mine

Shotcrete is an important technique for surrounding rock support,according to the amount and position of water can be divided into dry,half-wet and wet three kinds.Dry shotcrete is forbidden in coal mine because of dust and spraying rebound,and these problems alse beyond control of half-wet shotcrete.In comparison,the wet-shotcrete of making concrete products and re-spraying has the inherent advantages of no dust and low rebound,but the limited underground space and the secondary dust emission of the traditional rapid accelerator process have become the key problems in promoting the use of this process.Therefore,this paper first designs a new type of wet-shotcrete system according to the actual working conditions of coal mines.Secondly,in-depth analysis and optimization of feeding system and accelerator-water solution parameters,developed a new type of wet-shotconcrete jetting unit using the new type of accelerator process.Finally,the spraying effect and the improvement of concrete mechanical properties were evaluated by field spray test.The main research results are as follows :(1)According to the underground conditions and wet-shotcrete of coal mines,the wet-shotcrete spraying system of coal mines is proposed,which mainly includes the feeding system,the output spraying system and the new accelerator process.The feeding system is mainly composed of underground feeding device and double mixing device,which can produce concrete products.The output injection system is mainly composed of double piston output device,which can output high efficiency and long distance shotcrete products.The novelty accelerating technology is mainly to prepare the accelerator-water solution and add it into the special injection,which can reduce dust and improve the accelerating effect.(2)Based on the discrete element method,the simulation calculation model of feeding and mixing device of feeding system is established,and the design of ’ uniaxial reverse blade ’ and ’ double layer mixing structure ’ plays an active role in the improvement of concrete material ratio and mixing effect.The influence of spiral speed,stacking height,blade form and spacing on working performance is mastered,and the optimal parameters of feeding system are determined.(3)Combined with the hydration process of cement and the mechanism of traditional solid accelerator,the feasibility of the new accelerating technology of ’making aqueous solution with solid accelerator ’ was demonstrated.Laboratory tests were carried out using different mass solutes and solvents to master the influence of accelerator solution on the coagulation effect and determine the optimal accelerator parameters.(4)Based on the parameter optimization of feeding system and accelerating technology,a novelty type of wet-shotcrete unit which can use the new accelerating technology is developed.The field jetting test shows that it has significant improvement in reducing dust,reducing rebound and improving the strength of shotcrete.There are 89 drawings,33 tables and 115 references in this paper.