No-pillar sublevel caving method

In underground mining of metal deposits, ore body tilt thick (the thickness of the ore body 4 ~ 10m, ore angle 30 ° ~ 55 °) about 23% of the total mining deposits [1], the thick inclined coal ore It has always been a mining problem at home and abroad. The mining characteristics of this type of deposit are that the mobile space conditions of the collapsed ore are poor, and there is no “recycled section” condition. It is impossible to use the (low) lean ore mining method, but the actual This kind of situation is often encountered in production. When the ore body is mined by the sub-column-free sublevel caving method, the mining effect is significantly worse than that of the thick and steeply inclined ore body. The ore loss rate in some mines is as high as 40% [2] ].
In order to solve the problem of large depletion of caving method, domestic and foreign scholars have carried out a lot of research work on the law of ore movement under overburden, and have made significant progress in the theory of ore mining, computer simulation of ore mining, and ore mining process. Representative ore-mining theories include ellipsoid ore-mining theory, ellipsoid-like ore-mining theory, and stochastic medium ore-mining theory. These theories play an important role in guiding the study of ore mining and on-site production. Traditionally, the sublevel caving method without pillars is mainly used to mine ore bodies with steep slopes and medium thickness. With the application of low-lean mining technology and the improvement of mining equipment level, its application range is expanding.
Jade depression iron ore, Xishimen iron ore, gold and other mining site Xiadian industrial experiments show that the exploitation of low-loss mode for lean gently inclined (angle of 5 ° ~ 30 °) ore body, to achieve a safe, efficient mining and achieved A good technical and economic effect [3-5].
The current research focuses on the flow properties of loose ore and the mining of steeply inclined ore bodies [6-12]. Ren Fengyu considered the influence of the side wall of the upper plate, and established the movement equation of the loose rock in the inclined wall above 60° in different sections [13]. For the study of the movement equation of the loose ore in the medium-thick ore body of the inclined wall inclination angle (30°-55°), it is still a blank on the theoretical height.
In this paper, considering the influence of ore body thickness, a physical simulation experiment of inclined ore body with a dip angle of 55° and a thickness of 6-10 m is carried out.
1 preparation before the experiment
1.1 Experimental model
Experimental models were prepared using 10 mm thick wood plywood at a geometrical similarity ratio of 1:25. The simulated ore body has an inclination of 55° and a thickness of 6 to 10 m, and the size of the mining approach is 2.5 m×2.5 m. The model size is 135 cm x 6 cm x 120 cm. In order to facilitate the filling of the ore and the arrangement of the marking particles, the planks on one side of the model were sawed into 24 5 cm wide planks before the experiment, ensuring that the thickness of the ore filled each time was 5 cm. The size of the ore discharge port is 10cm×6cm×10cm, and a gate and a pallet are arranged at the ore discharge port to control the ore discharge speed.
1.2 Experimental materials
The experimental bulk materials were prepared according to the actual ore size of the ore block 1:25, and the gradation is shown in Table 1.

1.3 mark particles
In order to ensure the consistency of the experimental bulk fluidity, the bulk material used to make the marker particles is directly selected from the experimental bulk materials [14]. After selection, it is dyed and the marked paper is pasted on the granules. The size of the marker particles is 8 to 12 mm, and a layer of marker particles is placed every 5 cm in the vertical direction, and a marker particle is placed every 3 cm in the horizontal direction, for a total of 24 layers. The arrangement of the marker particles is shown in Figure 1.

2 experimental operation
Each layer of the ore should be compacted to reduce the seepage of fine particles with a packing density of 1.6015 g/cm3. During the ore-boring process, the single ore discharge amount should be about 100g, and the current release amount of the corresponding mark particles should be recorded in the order in which the mark particles are discharged. The ore is released from the ore discharge, and the amount of the released body before the arrival of a certain particle in the ore body reaches the discharge port is called the amount of the hole at the particle point.

During the ore-boring process, uniform ore release should be maintained as much as possible. The experiment of each ore body thickness should be repeated 2 or 3 times. Due to the presence of some ore with a relatively large particle size, in order to avoid clogging of the ore discharge, the width of the shovel for the ore is the same as the width of the ore discharge. Each time the mine is discharged, the shovel is used to clear the ore outlet to ensure that the mineway is filled with ore every time the mine is discharged.
3 experimental results
The amount of current release of each of the marker particles is accumulated in the order in which the particles are released, and the amount of discharge of the corresponding marker particles is obtained. The data of the uphole volume of each experiment was counted, and the XQ coordinate system was established, as shown in Fig. 2.

A plot of the release of the marker particles of each layer of different ore body thicknesses is plotted in the coordinate system (Fig. 3). According to the development of the curve, it is divided into three stages: the first stage is parabolic, the second stage is S-shaped growth curve, and the third stage is linear growth curve.



4 analysis of experimental results
4.1 Influence of ore body thickness on bulk flow
The development of the curve of the emission thickness of each ore body is basically the same. Therefore, the influence of the thickness of the ore body on the flow law of the bulk is relatively small and even negligible.
4.2 Influence of the side wall of the upper and lower plates on the flow of the bulk
The smaller the amount of the marker particles released, the earlier the release time is indicated. Under the same ore body thickness, in the parabolic phase of the release curve, the marker particles near the central axis of the ore discharge are preferentially released. It can be seen that at this stage, the upper and lower disc walls have no constraint on the bulk flow. At the end of this period, the side walls of the upper and lower plates have a restraining effect on the loose bodies. On the same horizontal layer, the flag particles closer to the side wall of the upper plate are released earlier.
5 Conclusion
(1) According to the graph of the release amount of the particles in each horizontal layer, it can be seen that the ore depositing under the condition of the inclined wall boundary is a complicated process. If the method is determined according to the method of reaching the pore volume, different types of emission body geometry will be obtained.
(2) During the bottom mining process under the condition of inclined wall boundary, the influence of ore body thickness on the flow of the bulk is relatively small, and basically does not affect the flow law of the bulk.
(3) Under the constraint of the side wall of the upper and lower discs, the looser body closer to the side wall of the upper disc is released first on the same horizontal layer.
references
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Author: Ouyang Bin, pottery dry strength; School of Nuclear Engineering, University of South China Resources;
Article source: "Modern Mines"; 2016.4;
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