Experimental Study On Effect Of Shoveling Depth On Ore Drawing Effects Of Non-pillar Sublevel Caving Method

With its advantages of safety,efficiency and low cost,the non-pillar sublevel caving method has been widely used in the domestic underground iron mines.Because the caved ore is gradually drawed under the overlying rock during the drawing process,the ore loss and dilution with poor recovery rate is very outstanding.Aiming at this problem,many researches at home and abroad focused on ore drawing theory,structural parameters,overburden formation and ore-drawing technology,and achieved fruitful results.During the process of non-pillar sublevel caving method,the shoveling depth has a great influence on the disturbance range and flow characteristics of ore and rock,it is an important factor which can not be ignored for the large loss and dilution,but the research in this aspect is rarely reported.Three kinds of caving space conditions with seven different shoveling depth were analyzed based on a single ore drawing model with large structure parameters of physical simulation experiment.Further draw body form and the ore loss and dilution under the influence of shoveling depth were studied by the location information of different marker particles.Main research contents and conclusions are as follow:(1)The waste rock at the front face of the end of the ore drawing will invade the ore drawing process earlier than the top waste rock.When the shovel depth is small,the rate of rock mixing rate increases slowly and the hanging-up arch often occurs at the ore drawing hole;with the increasing of shovel depth,the increasing rate of rock mixing rate enlarges and it is difficult to form the hanging-up arch in the ore drawing hole.Meanwhile,it is discovered that the inhomogeneous flow of ore and rock at the drawing hole is an important factor induced the waste rock at the front face of the end of the ore drawing invade the ore drawing process earlier and massively.(2)There is a certain matching relationship between the shoveling depth and the caving step in the process of non-pillar sublevel caving method.The greater the caving step is,the later the invasion time of the frontal waste stone will be;the greater the shoveling depth is,the earlier the invasion time of the frontal waste stone will be.When shoveling depth is small,the ore descent rate,rock increasing rate,single rock mixing rate with the rate of change is relatively flat,and the ore recovery rate was low with low rock mixing ratio;with the increasing of the shoveling depth,the rate of change of them increase gradually,and the recovery rate of ore and rock mixing rate also will increase.When the caving space is 92 mm,and the shoveling depth is 106.46 mm,the recovery rate can reach the maximum value at about 59% with mixing rate is about 16%.(3)The shoveling depth has a great influence on the slip surface developed along the direction of the entrance.Take the end wall as the reference,when the shoveling depth is less than 86.46 mm,the maximum trace of draw body along the draw way direction is about 120 mm,and when it is more than 86.46 mm,it is about 140 mm.The front rock intrusive drawing space in height in the roof level of the draw way above 20~30 mm,and the angle of intrusion is about 70°;the boundary of ore drawing in the roof level of the draw way is about 60~80 mm,with the angle is about60°,so the position of the sliding surface can been determined,sliding surface is one part of the arc of draw body.