Comprehensive law, room and pillar method

I. Overview

Due to the gentle inclination, it is difficult to return to the mining column under the open conditions of the mine. For the comprehensive method and the pillar method, the pillars should be treated differently depending on the specific conditions:

(1) For ore that is fully recovered with high value requirements, as far as possible, no pillars (replaced by artificial pillars) or recovered under the conditions of cement filling in the mine;

(2) Under the following circumstances, the pillars are not recovered: the surface needs to be protected, the ore value is low, and it cannot be replaced by artificial pillars; the retained pillars are mostly non-mineral or lean ore sections, and the mining grade is very low; Poor, it is difficult to ensure safe operation when returning to the mining column; to isolate the pillars to control the ground pressure and ensure the safety of the operation;

(3) Selective partial recovery. Whether the pillars are harvested or not, the quantity and location of the mining depends on the stability of the pillars and roof, the ore value and grade distribution, and whether the surface needs maintenance.

Selective recovery has the following conditions:

1. Pulling the column back to the mining column: According to the different degree of stability of the roof, some of the pillars are recovered at intervals. The interval may be one for the first one, one for the second, and one for the second. This method is applied when the ground pressure is not large and the grade distribution is relatively uniform.

2. Returning to the mining column by the column method: supporting the roof with the raft or artificial pillar near the pillar to be recovered and then recovering. When the ore body is not thick (less than 2~3m), the artificial pillar is built with stones, and when it is thick, the concrete column is used. The raft is easy to set up, and the side frame can be sown, but the wood consumption is large. It should be used as an emergency technical means when the source of the pit is sufficient and the ore value is high. Alternative methods should be used under conditions where the ore is of high value and the grade is high but the distribution is uneven.

3, the cutting column method back to the mining column: according to the stability of the roof and pillars and the distribution of useful components in the pillar, under the premise of ensuring sufficient pressure section of the pillar, the mining is rich and poor.

These methods are often used at the same time.

FIG 1 Guizhou mercury ore mining column selection back case

Figure 1 Pillar mining of Guizhou mercury mine

1—artificial pillar; 2—mineral column; 3—owned mining column

Figure 2 Inter-column extraction method

A—shallow hole blasting one side of the extraction column; b—medium hole blasting one side of the extraction column;

C—the side of the sampling column; d—the lower part of the extraction column; e—interval recovery; 1—medium hole;

2—shallow hole; 3—has returned to the mining column; 4—does not return to the mining column.

Table 1 Brief introduction of the comprehensive mining method and the pillar method of the mine in some domestic mines

The continuous pillars in the room are usually returned to the circular or square discontinuous pillars after the mining bins have been recovered. Whether the continuous pillar of the panel is recovered depends on the condition of the roof and its effect.

There are several situations in the top and bottom columns: (1) the width of the top and bottom columns is small, and the roof is not good when the roof is not good; (2) after the mining of the lower part, the roadway is continuous or Interval mining; (3) With the mining of the lower mine, use the mining system to mine.

The principle of choosing to recover is: under the premise of ensuring safety, it is difficult to collect poverty, and it is difficult to recover. The top plate is stable and not stable. Before the mining, the conditions of the roof and the pillar should be carefully checked, and the grade of the pillar should be reviewed. If necessary, additional sampling and testing should be carried out, and the trade-offs and corresponding technical measures should be decided according to the results obtained.

Excavation of the thin columns of thin and medium-thick inclined ore bodies by the comprehensive method or the room-pillar method is generally only partially extracted except that the top plate is very stable. The location and quantity of the extraction are determined according to the stability of the roof, the grade of the ore and the inclination of the ore body. Figure 2 shows several ways of extracting the column. Among them: mode a is conducive to the maintenance of the roof, but it is difficult to clean up the ore, and the efficiency is low; when the inclination of the ore body is steep, the modes c and a are favorable for the mining; the methods a and b are beneficial to improve the collapse efficiency. The corresponding method should be adopted in different situations. Table 1 shows the mine pillars of some mining mining room and comprehensive methods.

The shallow hole blasting method is usually used to return the mining column. However, the top plate is very stable and the inner body is blasted when the ore body is thick. Pay attention to the direction, number and detonation sequence of the blasthole, try not to damage the left part of the roof and the pillar, reduce the degree of ore scattering, create better conditions for the mining, and partially use the explosive force to move. A number of pillars are concentrated in one rock drilling (or the mine shaft is drilled when the mine is harvested), which is conducive to simplifying production organization and enhancing mining and operation safety.

Strict roof management to ensure the safety of mining is an important issue back to the mining column. From the bottom to the bottom, from the far and near return sequence, insist on timely and rapid recovery, so that the existence time of the pillar and the recovery time are as short as possible. Carefully study the maximum safe area that the top plate is allowed to expose, the maximum safe spacing and minimum safe size of the pillar. According to the actual situation of mining, review the geological data, pay attention to the existence of latent and weak surface. Establish a ground pressure observation system to closely monitor the stress, deformation and displacement of the roof and pillars, and provide safety forecasts in a timely manner. When the ore body is thick, the roof cleaning and bolt installation equipment should be configured as much as possible. The supplementary support means should pay attention to the construction quality and ensure reliable and timely. According to the uniformity principle of mine pillar mining, in order to achieve the purpose of multi-recovering the pillar under safe conditions, the mining method should be considered as a whole, so that the roof and pillar of the mine are in good condition after mining. American White Pine with initial copper ore 11.5m wide square pillar, which pillars is only 30% lower than the stress extent pillar. In the mining, the pillars collapsed and the roof fell, and the recovery rate of the mine pillars was low. Later, the pillar was changed to a 4.2m wide (and height, etc.) yielding pillar, and the panel twist was reduced to 90m, so that the stress of the panel pillar was adjusted to 54% greater than the room pillar stress, and the result was avoided. The top of the stope and the recovery rate are improved. This shows that under certain conditions, by adjusting the size of the mine pillars, the size of the separated pillars is relatively reduced, and a continuous pillar with a large rigidity is added at a certain distance, so that the discontinuous pillars are in the yielding state and the stress relief zone, so that More load is transferred to the surrounding original rock or the pillars in the remaining area, which is beneficial to control the stress of the roof and keep the pillar stable, which is convenient for mining the pillars. The Soviet Jezkazgan mine found that it is difficult to avoid the early damage of the roof and the pillar when leaving the mine in the mine, but the operation efficiency is low and the recovery rate is low. It is better to retain the strip column. After the mining house is finished, the strip-shaped ore column is reduced to a discontinuous ore column in the reverse order of the mine mining direction, and the mining block is finished. In this way, premature failure of the roof and the pillar is avoided, and the entire mining is carried out under the roof supported by the strip pillar, the roof falling is greatly reduced, and the mining operation is simple. It is also an effective way to recover the strip-shaped pillars by means of the collapse of the roof. It has been applied in France, the United States, the Soviet Union and other countries.

Generally, the mining method and system for mining in the mining area are still used for mining. The mines in China mainly use electric shovel, and the mine column can be transported by explosive force when it is close to the funnel. Maneuverable mining equipment that can be remotely controlled should be studied and adopted. In recent years, the remote control scraper is being applied gradually at home and abroad. In 1983, Outokumpu of Finland used the TR-350 and TR-500 scrapers equipped with remote control for the recovery of the column of the house column. The ore loss rate was reduced from 21% to 12%. The Soviet Mirgalim Mine also used the remote control scraper to collect the remaining ore from the mining house recovered from the room and pillar method, and achieved good results.