Since the ore-retaining 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 of the working face and the surrounding rock of the upper plate. From the situation of using mines in China, the length of the stope is generally 40~60m when the stage height is 40~50m. If the surrounding rock is particularly stable, the length of the stope can reach 8m~120m.
In order to protect the upper transport roadway and temporarily support the surrounding rock, it generally has a certain height to withstand; and in order to protect the lower transport roadway, support the ore remaining in the mine, and construct the mining funnel, it is necessary to keep a certain Height of the bottom column; if a pedestrian patio is required, a column should be placed on both sides of the mine.
Shallow hole retention plan
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 4~5m. Its main function is to connect the patio with the mine to allow personnel, equipment, materials, plumbing and fresh airflow to 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 4~5m in thin and extremely thin veins; in the medium or thick ore body, according to the reasonable burden area of ​​each funnel (generally 25~36m 3 , the maximum should not exceed 50m 3 because the funnel burden area is over Large, not only increases the workload of the flat field during recovery, but also reduces 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 cycles are repeated one after another, and when the mining face reaches the designed topping boundary, centralized ore mining (or a large amount of ore mining) is carried out.
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 thin and very thin veins are mined by the method of retention, some mines do not leave a 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, the blastholes can be drilled in the top column, bottom column and inter-column before the start of centralized ore-concentration, and the top and bottom columns are blasted first and then the post-blast column. 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 free surface of the top column collapse, and the extraction funnel should be constructed at the bottom of the column.
6 ) Evaluation
The advantages of the ore retention method are: simple structure, convenient management, small amount of precision cutting work, and easy to master production technology. 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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