Since the collected ore is released by gravity, the method is generally applicable to the steeply inclined thin and fine ore body (pulse) of the ore-rock solid; and because the large amount of ore accumulates in the stope, the ore is required to be non-oxidizing and agglomerating. Sex and spontaneous combustion.
(1) Stope layout
Since the retention method is mainly used for the recovery of the steeply inclined thin and the thin ore body (pulse), the stope is generally arranged along the strike. The length of the stope depends mainly on the allowable exposed area of ​​the roof and upper rock of the working face. From the situation of using mines in China, the length of the stope is generally 40-60m when the height is 40~50m. If the surrounding rock is particularly solid, the length of the stope can reach 8 to 120m.
In order to protect the upper transport roadway and temporarily support the surrounding rock, a top column with a certain height is generally left; and in order to protect the lower transport roadway, the ore construction mine ore stored in the mine house is supported, and a certain height is required. The bottom column; if construction is required, a column should be placed on both sides of the mine.
(2) Precision cutting
The mining work includes the transportation lane 1, the patio 2 and the communication lane 3. In the thin and extremely thin veins, in order to facilitate prospecting, the stage alleys and patios are all excavated along the veins. The contact road generally tunnels along the patio every 4 to 5 meters. Its main function is to connect the patio to the mine, so that personnel, equipment, materials, wind pipes and fresh airflow enter the mine. In order to prevent the collapse of the ore and block the contact road, the contact degree on both sides should be staggered.
The cutting work involves digging the hopper 6 and pulling the bottom. The funnel spacing is generally 4 to 5 m in thin and very thin veins; in the medium or thick ore body, the reasonable burden area according to each funnel (generally 25 to 36 m3, the maximum should not exceed 50 m3, because the funnel burden area is too large, Not only increase the amount of flat field work during recovery, but also reduce the efficiency of the ore discharge). The bottom can start from the bottom of the contact road and start to dig into the downhole and then expand to the sides of the ore body.
(3) Recovery
The mining process includes: rock drilling (eye drilling), blasting, ventilation, partial ore mining, dome (top plate inspection, removal of pumice ) and flat field (leveling the surface of the heap), secondary crushing (explosion block). These jobs are completed in sequence and are called a recovery loop. The recovery cycle is repeated one by one, and when the mining face reaches the designed top column boundary, centralized ore mining (or a large amount of ore mining) is carried out.
In order to improve the efficiency of the ore discharge, the vibrating and concentrating machine is generally installed under the funnel, and the vibrating force is used to improve the ore flow performance, improve the passability of the ore discharge port, and reduce the secondary crushing amount.
(4) Ventilation
The ventilation line of the mine is: fresh air flow enters the mine from the side patio and the contact road. After cleaning the working surface, the dirty wind passes through the other side of the contact road and the patio, enters the upper return airway, and exits the ground through the return air well. .
(5) Pillar mining
When mining thin and extremely thin veins by the method of retention, some mines do not leave the column, and the bottom column is replaced by an artificial bottom column such as cement masonry. At this time, the proportion of the pillars is small.
For pillars with large reserves, before the start of centralized ore mining, the blastholes (bottom map) can be placed in the bottom column and the middle column of the top column respectively, and the top and bottom columns are blasted first and then the column is blasted. The collapsed ore of the pillar is discharged from the funnel at the bottom of the nugget together with the ore remaining in the mine. Before the collapse, the cutting patio should be excavated in the top column as the freedom of the top column to collapse.
(6) Evaluation
The advantages of the ore retention method are: simple structure, convenient management, and small production technology for easy cutting. Its main drawback is: mine left the room for about two-thirds of the ore can not be released in time, the backlog of funds; after stope mining is completed, leaving a large number of mined-out area needs treatment. The ore content of the pillars is large, and generally no recovery is carried out. Therefore, the ore loss is large.
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