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  The overburden layer in the sublevel caving method without bottom column not only plays a role in damaging the impact of the surrounding rock when it is falling, but also provides extrusion blasting conditions to prevent the ore from being scattered in the goaf and ensuring normal mining. The sublevel caving method without bottom column requires that the covered rock layer be filled in time with the goaf.
The formation of the overburden may utilize natural caving or the use of forced caving. Mines that need to be forced to ceiling in foreign countries are generally first mined by other mining methods, such as the stage forced collapse method, the stage mining method, etc., and then converted to the bottomless sublevel caving method. At this time, the general empty area treatment method is adopted. A cover rock formation can be formed.
In some mines in China, blind ore bodies that can not fall in time are used. In the initial stage of production, there is no sub-pillar sublevel caving method. There are two main methods for forming rock strata. First, concentrated topping, this method is based on the arrangement of the sub-column sublevel caving method, mining 1 to 2 sections, but at this time, due to the absence of overburden, the ore is discharged under the empty field, and some of the ore thrown in the empty area is temporarily Can not be shipped out, when the top plate reaches a certain exposed area, and there is enough compensation space in the empty field, it can be concentrated. Another method of topping is to use side-by-side mining. This method digs a series of roofing roadways parallel to the mining road. In the topping roadway, the upper hole is drilled into the fan-shaped top hole, and the mining hole is divided into several times. Row blasting forms a covered rock formation.
When the inclined ore body is mined, the formed cover rock layer will be lost in the lower plate, so the top plate should be supplemented and topped. The method is to extend the approach to the upper plate and use the normal mining method to collapse the surrounding rock for supplementary release. top.