Wall caving method

There are two types of work, linear and stepped.

1 Straight line - good for roof management. Each work surface does not interfere with each other and has high work efficiency. However, when the eel is used for ore mining, the upper part of the antimony ore cannot perform other operations, and the ability of various equipments cannot be fully utilized, which may reduce the production capacity of the ore.

2 Stepped working face——The mining and mining work and pillar work can be carried out on different steps respectively, but this form is difficult to manage due to the difficulty of the pillars, so it is rarely used at present (the lower step has a large suspended ceiling). The largest part of the field pressure is just in the middle and lower part of the stope.

For mines applying wall caving, the working face of the mining face is generally linear.

2, falling mine

Off the wall caving mining shallow hole, usually yT-25,01-30 other light type air-leg rock drill, individual soft ore mining by using picks (e.g., Lawrence manganese ore, ore, etc. used Jiaozuo) usually has a depth blasthole It is 1.2 to 1.8 meters, slightly larger than the one-time advancement distance of the working surface. The minimum resistance line W = 0.6 to 1.0 meters. The detonating line is used, and the fire detonator is detonated. The commonly used explosive is ammonium nitrate explosive.

The amount of blast hole per meter is 1.3 to 1.7 tons/meter.

3, mining and transportation

Most mines use electric rafts to mine, and electric shovel winches are installed in cutting roads or diverting chambers. With the progress of the mining face, the electric winch is regularly moved.

28 is a common power rake or rake 30KW electric winch, scraper bucket volume of 0.25 ~ 0.3m ^3, Scraper transfer efficiency is 100 to 120 tons / Taiwan class, (Pang fort rake iron ore mining and power efficiency of 250 ~300 tons / shift)

For soft ore, may be employed haulage chain plate conveyor ore, if under this condition, power is still rake ore, will cause great lean (e.g. Changgiakou gold ore, gneiss plate, the scraper The bottom plate has a deep groove, resulting in a depletion rate of up to 48%)

4, roof management

For the longwall caving method, roof management is very important. It is not only related to the issue of safe production, but also to a large extent affects labor productivity, pit wood consumption and recovery costs.

(1) Standing pillar support roof

1 Wooden pillar support - the diameter of the column is 18 ~ 22 cm, the column cap is 0.5 meters long.

2 Metal pillar support——The metal pillar support capacity is larger than that of the wooden pillar, and it can be reused many times, but the weight is large. In the mine where the roof and the bottom plate are stable and the thickness of the ore body does not change much, the hydraulic shield bracket can also be used.

3 Other support methods - In addition to wooden pillars and metal pillars, poles, rafts and pillars can also be used.

The poles are generally used in conjunction with wooden supports to increase the spacing of the columns and reduce wood consumption.

The raft has a large bearing area and supporting capacity, and is generally used to support both sides of the sliding mouth with a relatively large exposed area at the lower part of the stope and to protect the upper safety exit. It should be noted that the erection of the raft does not affect the mining.

(2) Topping

In order to reduce the pressure on the working face, ensure the normal operation of the mining work. Therefore, when the mining face is advanced to a certain distance, the pillars of the goaf should be removed in a planned manner, and the top should be put down to ensure production safety. There are plans to remove this pillar caving roof slate stone work called caving.

a, topping steps:

1 Before putting the top, first lay the intensive pillars, you can play a single row of dense pillars. If the pressure is big, the single row can't work, you can play double rows. (This is called the IP top pillar, without the column.)

2 Place the top blasthole in a local area. Hole depth 1.6 to 1.8 m, blasthole angle is about ^600. The blasthole hits 0.5 meters outside the IP top pillar, and a row of eyes is pushed in the reverse propulsion direction. The eye is pre-polished and the top plate is forced to collapse after charging. When the top plate cannot fall naturally, it is necessary to win the eye, and vice versa.

3 Retracting the column – recovering the pillar work in the topping area, generally using the back column winch of the upper stage roadway to recover the pillar, adopting the 15-20KW slow-moving winch, pressing from the bottom to the top in the oblique direction, along the direction from far to near The order is back to the column. (The winch is placed at the safety port). (From the figure A, the slash is removed)

If the pillar cannot be recovered manually or mechanically due to large ground pressure or other reasons, use an auger to drill a small hole in the pillar to load the explosive or directly attach the explosive to the pillar to collapse the pillar.

b. Topping parameters:

Topping parameters include: topping distance, topping distance and hanging top distance, hanging top distance=mounting distance+control top distance

1 Topping distance - The width of each topping is called the topping distance, and the range of the topping distance is relatively large, generally several times the pillar shed. The change is between 2.8 and 10 meters. Some mines use a topping distance of 1.2 to 6.4 meters, which is determined by the specific conditions of the surrounding rock.

2 Control top distance - When the top is placed, it is guaranteed to maintain the maximum width of normal mining work, called the control top distance. Generally the distance of 2-3 rows of pillars.

3 Suspended top distance—The width of the ceiling exposed is called the overhanging distance.

The specific conditions of each mine are different, and the ceiling distance is different.

(3) The necessity of planned topping work

As the longwall working face advances, the exposed area of ​​the top plate is gradually increased, and the top pressure is also increasing. When the top pressure reaches a dangerous limit, it is possible to crush a large number of pillars and cause the top surface of the working surface to fall. In order to reduce the top pressure of the working face and ensure the normal working of the mining work, when the working surface is advanced to a certain distance, a part of the top plate far away from the working surface is manually forced to collapse, so that the broken and exploding rock supports the upper rock layer. In this way, the exposed area of ​​the ceiling of the goaf is reduced, and the top pressure of the working surface is also reduced, so that a pressure reduction zone is formed near the working surface, so that normal mining work can be performed.

5, ventilation

The ventilation condition of the longwall working face is better. The fresh air flow passes through the pedestrian well in the lower stage, and the cutting alley enters the working surface. After cleaning the working surface, the living wind passes through the upper safety road and is discharged to the upper stage. Partition ventilation should be considered when the length along the strike is large.