Research And Application Of Blasting To Form A Shaft By One Step With Medium-length Hole

Raises excavation is the most difficult project among all digging projects. Digging raise by normal method needs substantial labour with aweful working conditions and low safety assurance. The most economical and effective method for digging a raise is one-step blasting method.Based on the project study on powerful mining technology for large-thick broken ore body with full-sublevel one time pre-splitting and tight blasting of Shandong Gold Corporation, in the reference foreign and domestic materials on blasting theory and insite examples about blasting to from a shaft, methods such as throey analysis,model prediction, numerical simulation and insite test are used to systemly and deeply research on blasting to from a shaft by one step with medium-length hole. Several conclusions can be obtained as below:(1)According to blasting theory and straight cutting mechanics, parameters related to blasting to form a raise are analyzed. As to main parameters, such as the initial space, the number of blasting hole, the distance between blasting hole and empty hole, the concentration of charge and the delay time is computed respectively, thus different blasting hole outlay methods are designed.(2) Based on the projection pursuit regression theory,9factors (compressive magnitude, rock density, diameter of empty hole, number of empty hole, diameter of charged hole, number of charged hole, the maximum resistance line, amount of charge and linear charged density of the initial hole) are selected as discriminating index constructing the model to predict2factors (, depth of shaft and size of shaft). Apply the established model to predict the effect of shaft blasting38groups of data are trained and tested. The predicted results are consistent with the measured ones. Thus, use the model to predict the blasting result of the former design.(3) Through the approach of LS-DYNA, dynamic rock breakage process with blast hole and various diameters of empty hole is simulated and blasting result with different diameter and number of empty hole is analyzed. Numerical result shows:Empty hole in blasting cut produces empty hole effect, which orients rock breakage whose area becomes larger as the diameter of empty hole increases. Compare different groups of models, Compression fragmentation zone and tension fragmentation zone are more obviously observed with large size of empty hole.(4) Programs fit to Xinchen gold mine are selected and put into use. Because of high ration of deflecting, the first trial was not successful. After ameliorating the design, the second trial was succeeded. The raise is run through with blasting caters at both sides are well controlled. The cross section corresponds with the design.The3rd trial based on the former experience succeded with high basting utinilty ratio and smooth surface. The third deign is about raise brushing. After blasting, the cross is smooth with high blasting ratio. The depth and the section meet the design.