| The enlarged structural parameter represents the development trend of modern pillarless sublevel caving. Cooperating with the construction project of Da Hong San Iron Mine, this dissertation studied the mining technology of high sublevel and large space drive interval of pillarless sublevel caving. The industrial experiment turned out that the sublevel height was increased from 15m to 20m, which could reduce 25% of the recovery and cutting costs, the ore volume of each step of blasting was increased by 7000t, the mining productivity was improved, and the ore loss and dilution rate was reduced effectively. The research achievements marks that sublevel height of pillarless sublevel caving in our country comes into a new state (20m high), the distance of similar mining technology level is shortened between our country and advanced western countries (30m high).The prediction of ore dilution and loss rate is one of the important part of drawing theory on pillarless sublevel caving. Based on the former resesrch about the dilution calculation of ore interfusion, a further research that the top and flank wastes were mixed into the drawing body causing loss and dilution of ore was made on in this dissertation. The calculation formula of top and flank wastes mixed dilution and recovery rate was worked out. And the system for loss and dilution rate calculation of side drawing theory is improved greatly, thus the theoretical basis for systematic predicting ore loss and dilution rate was established.Usually ore drawing dilution rate is influenced by the different combination of sublevel height, drive interval and step of blasting. The method of structural parameter optimization was studied in the dissertation. After objective function of the maximization of difference between recovery and dilution rate was founded to confirm step of blasting, the objective function of maximization of industrial unit of reserves gain and unin of concentrate gain were established as mathematical model. The traditional method only considering loss and dilution rate to define structural parameter was changed, a new approach was created to define structural parameter for the purpose of gaining the maximal bebefit in the deposit exploitation.Theory study and the experimental test turned out that ore-drawing dilution rate could be greatly reduced by low dilution ore-drawing. But nowadays ore-drawing managemen mode and the complicated conditions in practical production are not matched well. The dissertation changed the past combined cutoff grade ore-drawing, ration ore-drawing was applied for the first time.The industrial experiment showed that the mode of the ration ore-drawing is applicable with both simplicity and easiness, and the goal of low dilution ore-drawing could be well obtained. The dilution ratio of drawn ore could be controlled within 5% (not including the ore-drawing in the bottom and in the upper bottom sublevel). The new opportunity for the popularization and the application of the low dilution ore-drawing would be brought by the ore-drawing management mode.The study on the regularity of top rock level caving in Da Hong San Iron Mine showed that in mining in the newly-built mining quarters of the main mining field, blasting the top rock of body should be adopted in the formation of the covering rock. When mining in the newly-built quarters was finished, the combination of the two ways-level caving and blasting could be applied to form the covering rock. The height of the level caving of top rock was 120m. When mining in the following mining quarters were finished, the mechanism of level caving was completely formed in the top rock of body, and then the covering rock was formed through the use of the level caving of the top rock, the final height of the level caving reached 160m.In the middle mining field 1 and 2, after the first step mining were finished, the mechanism of the level caving in the top rock of body was formed and covering rock was formed by level caving afterwards.
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