Empty field method

I. Overview

The primary condition for the recovery of the inter-column by the empty field method (including the retention method) is that the mine is filled with cement, and the filling body does not fall under the required exposed surface, and provides necessary support for the surrounding rock and ore of the upper and lower plates.

It is generally believed that when the intermediate column is used for the recovery of the inter-column, the filling body strength R ₂₈ ≥1~2MPa is required, and when the stage is high, R ₂₈ ≥2～4MPa.

The mine is filled with cement, mostly due to the value and grade of the ore (sometimes to control the movement of the rock and maintain the surface). The selected method of mining the column should ensure that the ore loss and depletion are low. Compared with the filling method, the empty field method has a series of advantages such as simple recovery process, high recovery strength and low mining cost. However, if the properties of the ore and the conditions of the deposit do not guarantee high recovery under low depletion, it is not suitable.

The ore and surrounding rock are stable, the ore body is stable, the shape is regular, the suitable dip angle, and the strength of the filling body of the mine is large, which is the basic condition for successfully using the empty field method to recover the inter-column. There are differences in the requirements for different methods (or scenarios).

The room and pillar method is mainly in the stable and inclined thin to medium-thick ore body of the roof and the ore, and the cement is used to fill the continuous pillar of the mine.

In addition to the general conditions of use, the following conditions should be emphasized for the mining of the column by the retention method: (1) the ore is stable, the pillar has no deformation and damage; (2) the surrounding rock does not help during the mining and ore-mining process; (3) the ore body The inclination angle is greater than 60°; (4) the ore body shape, especially the lower plate is relatively regular.

The stage mining method (usually segmented rock drilling) can reduce the ore stability and the inclination of the ore body appropriately, but it requires higher stability of the surrounding rock and the degree of ore body regularity. Its use conditions are: (1) the inclination angle is less than 60°, it is difficult to mine by the method of retaining ore, the workload of the flat field is too large; (2) it is unsafe to work under the roof of a large area of ​​ore; (3) to improve the mining intensity The geological conditions are suitable for mining with the stage mining method; (4) The mining method is used in the staged rock drilling stage of the mining house, and the segmented roadway exists in the inter-column.

China first applied the VCR method in the inter-column of cemented filling mines. It overcomes many shortcomings of the mining method and the mining method in the staged rock drilling stage. The structure of the stope is simple, the mining work is easy to mechanize, and some ore can be used to support the surrounding rock and the filling body. The work is safe and the ore is broken evenly. The bulk output rate is low. The above advantages have gradually expanded the scope of application. However, due to the use of stage rock drilling and horizontal stratified ore mining, the section of the rock drilling chamber is also large, and the stability of the ore, especially the regularity of the ore body shape, is higher than that of the section rock drilling stage.

Table 1 is a summary of some mines using the empty field method to recover the inter-column.

Table 1 Some mines use the empty field method to recover the filling of the mine room column

When using the empty field method to recover the inter-column, the mining and mining work is basically the same as that of the mining house, but there are also some characteristics, such as: (1) the nugget patio and the connecting road are generally arranged directly on the column or its upper and lower plates. In the surrounding rock, some of them can be placed in the filling body, which is reserved in advance when the mining room is cemented; (2) In order to improve the recovery rate of the top and bottom columns and ensure the safety of mining, a concrete artificial bottom column can be used, but the area is better. At the time of construction, it is quite difficult to construct a funnel structure artificial bottom column. Most mines still retain the ore bottom column. Before filling, the funnel is filled with ore, and a layer of cement material is filled thereon, and then filled with water sand or waste rock. (3) Strictly control the direction and depth of the blasthole to maintain a certain distance from the filling body to prevent damage to the filling body; (4) When using the upward stratification and mining to the upper part of the upper column, it is sometimes used to prevent accidents. The hole is collapsed once; (5) It is not appropriate to pick up the adjacent column at the same time; (6) The empty field formed by the recovery is generally filled with water sand or waste stone.