Method for inducing caving and troughing and its application in soft ore body

The cutting groove is an important process of the sub-column-free sublevel caving method. The cutting project is a project to open up the initial mining face and the collapse compensation space, mainly including the cutting of the cutting roadway, the cutting of the patio and the formation of the cutting groove. Whether the cutting project can excavate and cut the quality of the cutting groove according to the design requirements is directly related to whether the mining can be carried out normally and the effect of the mining is good or bad. If the cutting height does not meet the design requirements, the mining blasting will not easily form a suspended roof with the upper overburden, and not only the ore that has collapsed cannot be released, but also affects the recovery of the subsequent step, and when the suspended roof suddenly falls. It is also easy to cause serious accidents [1]. Therefore, the quality of the cutting groove has a significant impact on the blasting effect, and also affects the mine production cost and mining efficiency. The cutting project without sub-column sublevel caving method is large, and the excavation work environment of the upper cutting well is bad, especially the construction work surface is small, the ventilation conditions are poor, the gun poisoning and casualties often occur, and the soft ore rock mine excavation More dangerous and difficult.
1 grooving method and evaluation According to the construction of the patio, the formation of the cutting groove can be divided into two types: cutting patio trough and non-cutting patio trough [2]. The cutting patio trough is based on the first forming of the patio, the patio is used as the center of the cutting trough blasting and provides the free surface and the compensation space for the cutting trough operation; the non-cutting patio trough does not construct the cutting patio, and the cutting trough is completed by the blasting technology. Construction.
The cutting patio trough is divided into a cutting trough and a cutting patio combined troughing method and a cutting well pulling method. The cutting cross-section and the cutting patio joint trough are to cut a cutting alley along the boundary of the ore body to penetrate the end of each mining roadway, and then dig into the cutting patio at the appropriate position according to the blasting needs; on both sides of the cutting patio, self-cutting flat drilling Drill several rows of parallel or fan-shaped blastholes, each row of 4 to 6 blastholes; cut the patio as a free surface, and blast one or both sides to form a cutting groove (see Figure 1). The method is the most common drawing method used in the sub-column sublevel caving method, and the quality of the forming trough is easy to ensure, but the cutting amount is large.

Some mines use the cutting patio troughing method (see Figure 2). This method does not need to dig into the cutting alley, only the cutting section of the mining roadway with a section of 1.5m×2.5m, and the short side of the tunnel. The distance of 1~2m is favorable for the rock drilling of the trolley; the center line of the parallel mining roadway with the long side of the patio; 3 rows of blastholes on each side of the cutting patio, fine blasting, once slotting [3], the method is in each The end of the roadway must be dug into the cutting patio, so it is suitable for the case where the mining roadway is arranged along the ore body and is long.

The cutting patio trough is mainly made by blasting technology, which is mainly divided into a fan-shaped hole step angle groove forming method (see Fig. 3), a split blasting groove method and a wedge-shaped pulling groove method. The blasting area of ​​the fan-shaped hole step angle into the groove method is divided into the top expansion area, the trough area and the normal blasting area. The key of the groove method is to form a sufficient compensation space at the end of the top picking, and then the upper fan-shaped hole is arranged at the step angle, the rock-drilling lane is a free surface, and the full-section blasting forms a cutting groove. The method is convenient and flexible, has low troughing cost, short cycle and strong operability, and is relatively common in small stope and residual mine recovery.

The blasting groove method (see Figure 4), in the end of the mining roadway 4 ~ 5m, chisel 8 rows of fan-shaped blastholes, each row of 7 holes, blasting in rows, which is equivalent to forming a cutting patio. In addition, in order to ensure the area and shape of the cutting groove, three rows of 9, 10, 11 cutting holes are arranged, which are arranged in a manner equivalent to the cutting patio pulling method. The troughing method is also used under the condition that the ore is relatively broken. However, since the ore body is broken, it is difficult to have the conditions of the split blasting, so the practical application is not much.

The one-time blasting method of the wedge-shaped gutter is to cut the four-row angle of the fan-shaped blasthole in the cutting lane, and then use the millisecond blast to form the cutting groove once (see Figure 5). This troughing method is most suitable for use where the ore is not stable or is difficult to dig into the cutting patio [4-5].

2Inducing caving and pulling method and application
2.1 Project Overview Gold Mine ore 213 # 3 stope design using non-pillar sublevel caving mining, crushing of surrounding rock weak (see FIG. 6), taken in the registration process, a different degree of Roadway deformation and collapse.

The cutting roadway between 1# and 2# is called “1# cut lane”. Because of the broken rock, the metal arch frame and the backing plate are supported by the scaffolding. The middle section is seriously deformed. Support (see Figure 6 (a)), the repair is more difficult, the stability of the two ends is still good, a little maintenance can be used for rock drilling operations. Connect the opening of the cutting roadway between the 2# and 3# roads (hereinafter referred to as 2# cut lane), and the roof will fall off. The stability of the roof exposed block is poor (Fig. 6(b)), and the safety of the repairing construction is poor. It is difficult to use the traditional grooving scheme for the current stable rock conditions and technical level of the mine, and the safety is poor. It is necessary to develop a new method of pulling grooves according to the blastability of the rock.
2.2 Induced caving and troughing scheme and application 3# The cutting roadway is seriously damaged, and the roof does not have the condition of drilling the upward blasthole. The traditional troughing method is difficult to adapt to the stability characteristics of the ore. Therefore, according to the characteristics of the roof collapse when the excavation is not supported, and the engineering damage location, the method of inducing caving [6-8] cutting trough is proposed. The specific scheme is as follows: firstly, the roadway destruction of 1# and 2# The edge is maintained to ensure the safety of the medium-deep hole construction and the scraper mining, and the internal support structure is removed under the conditions of safe conditions to remove the falling ore, so that the roof has better falling conditions; Under the condition of good roof maintenance, the medium and deep holes are drilled into the two layers (see Figure 7(a)), and the blasting of the free surface is carried out to break the section and the way to the upper disc, and the exposed area of ​​the roof is increased. The ore body naturally falls. At the end of the 3# approach, the cutting roadway shown in Fig. 7(a) is constructed, and the ore body is used for ore mining by using a scraper or a skimmer to provide a space for the subsequent caving. After the induced fall to a sufficient height, the cutting area is used as the compensation space to cut the blasthole to expand the cutting channel as shown in Fig. 7(b) to form a complete cutting groove and carry out subsequent mining of the ore body.

According to the above scheme, the construction is carried out, and a good cutting groove is formed, and the 3# approach is started. The 3 rows of blastholes have been blasted, and the caving volume is 800t. At present, 300t has been mined, and there is no empty field on the working surface, indicating that the blasting The effect is good, which also shows that the quality of the groove formed by the scheme is good.
3 Conclusions The cutting trough is a key project in stope mining because of its special location and its important role in recovery. Different drawing methods have their own characteristics and applicable conditions. Which grooving method is selected depends on the stability of the field engineering. The soft ore body has good maneuverability, requires high strength support, and the safety of the cutting patio construction is poor. The induced caving method is the first mining segment for similar ore bodies, especially for sublevel caving without pillars. Has good applicability.

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Article source: Mining Technology; 2017.17(2)

Author: Ma Qibiao; gold Yantai Vocational College, Yantai City, 265 401;