Method for controlling subsidence area caused by underground mining in adjoining open-pit mine

Patent metadata

Field	Value
Publication number	US-11085296-B2
Application number	US-201716605122-A
Country	US
Kind code	B2
Filing date	Jun 6, 2017
Priority date	Apr 19, 2017
Publication date	Aug 10, 2021
Grant date	Aug 10, 2021

Abstract

A method for controlling a subsidence area caused by underground mining in an adjoining open-pit mine, applied in an open-pit and underground coordinated mining process. In the method, a ground subsidence area caused by underground mining and production is directly filled and covered with overburden materials such as soil and rock discharged from an adjoining open-pit mine; small and medium fracture zones and large fracture zones caused by mining are timely backfilled, tamped, and levelled according to areas before the ground subsidence area appears, the thickness of the levelled soil layer is kept above 1 m, and the area slope is controlled within 7°. By fully using overburden materials from an adjoining open-pit mine, the method controls a subsidence area caused by underground mining and greatly shortens the discharge distance of the overburden materials from the adjoining open-pit mine, also solves the safety problems such as air leakage and spontaneous combustion of coal caused by fractures in mine subsidence, and brings significant economic and social benefits.

First claim

The invention claimed is:

1. A method for controlling a subsidence area caused by underground mining adjoining an open pit mine, wherein the method comprises the following steps:
a. with an advance of the open-pit mine, a goaf is formed in an underground mining face along with the advance; along with a collapse of an overlying strata, two types of damaged zones, including medium and small fracture zones and large fracture zones, reaching a ground surface in different sizes, and a surface subsidence area are formed;
collecting soil and rock strippings produced in the open-pit mine;

b. screening and classifying the strippings to obtain rock and soil substances, transporting the strippings to the subsidence area to fill the fractures in different widths in the subsidence area on the ground surface respectively;
for medium and small fractures with a width of smaller than 0.3m in the surface subsidence area, a screened soil is filled into the medium and small fractures first;
when the fractures are filled to an elevation at a distance of 3m from a pit bottom of the subsidence area, filling the medium and small fractures with small rock blocks, till the pit bottom of the subsidence area is reached;

for large fractures with a width of greater than 0.3m in the surface subsidence area, screened large rock blocks are filled into cavities in the large fractures first, and then continue to fill the large fractures with small rock blocks screened from the strippings, till the pit bottom of the subsidence area is reached;

c. after all medium and small fractures and large fractures in the subsidence area are filled, compacting the pit bottom of the subsidence area by dynamic compaction, and then filling the screened large rock blocks into the subsidence area to an elevation at the distance of 2m from the ground surface, filling the subsidence area further with small rock blocks screened from the strippings till all of subsidence area are covered by the large rock blocks, then grouting a cement mortar into the subsidence area to an elevation at a distance of 1m from a ground surface; after the cement mortar is completely solidified, covering the filled cement mortar with the soil screened from the strippings, and compacting in layers at intervals of about 0.3m, till a filling surface is flush with the ground surface; and
d. new medium and small fracture zones, large fracture zones, and surface subsidence area are formed along with further advance of the underground mining face, repeat the steps a, b and c, till all fractures and subsidence areas disappear and the collapse of the ground surface stops.

2. The method of claim 1 , wherein, the medium and small fracture zones and the large fracture zones are backfilled and compacted in layers, wherein the ratio of the particle size of the rock used for a backfilling to the width of the current fracture is smaller than 1:3 in the backfilling process, and the compaction in layers to the surface soil and the compaction to the pit bottom of the subsidence area are dynamic compaction, 3 times of point compaction, skipped compaction at interval and 1 time of full compaction.

3. The method of claim 1 , wherein, with the advance of the underground mining face, the ground surface is backfilled timely before medium and small fracture zones and large fracture zones are formed in the ground surface; the slope of the subsidence area shall not be greater than 7° after the subsidence area is leveled, the thickness of the cement mortar grouted in a concrete layer shall not be smaller than 0.5m, and the thickness of the soil discharged from the open-pit mine backfilled in the surface layer shall not be smaller than 1m.

4. A method of stabilizing an area associated with underground mining adjacent an open pit mine, the method comprising the following steps:
a. with an advance of the open-pit mine, forming a goaf in the underground mining face along with the advance, thus forming two types of damage zones with the collapse of overlying strata, (wherein the damage zones are medium and small fracture zones and large fracture) zones, which damage zones reach the ground surface in different sizes, forming a surface subsidence area, and collecting soil and rock strippings produced in the open-pit mine;
b. screening the collected soil and rock strippings to obtain rock and soil substances, filling fractures of different widths in the surface subsidence area and on the ground surface with the substances, by (i), for medium and small fractures having a width of less than about 0.3 meters in the surface subsidence area, filling screened soil into the medium and small fractures; after filling the medium and small fractures to an elevation at a distance of about 3 meters from the bottom of the surface subsidence area, filling the medium and small fractures with small rock blocks, until a bottom of the surface subsidence area is reached, and (ii), for large fractures having a width of greater than about 0.3 meters in the surface subsidence area, first filling screened large rock blocks into cavities in large fractures, and then continuing filling the large fractures with small rock blocks screened from the strippings, until the bottom of the surface subsidence area is reached;
c. after filling the medium and small fractures and the large fractures in the surface subsidence area, then compacting the bottom of the surface subsidence area, and then placing screened large rock blocks into the surface subsidence area to an elevation at a distance of about 2 meters from the ground surface, filling and covering the surface subsidence area further with screened large rock blocks, then grouting mortar into the surface subsidence area to an elevation at a distance of about 1 meter from the ground surface;
after the mortar solidifies, covering the solidified mortar with soil screened from the strippings, and compacting it in layers at intervals of about 0.3 meters, until a filling surface is flush with the ground surface; and
d. while forming new medium and small fracture zones, large fracture zones, and surface subsidence area with further advance of the underground mining face, repeating steps a, b and c, until fractures and subsidence areas and ground surface collapse are reduced.

Assignees

• Univ China Mining

Inventors

• Ju Feng
• Guo Shuai
• Fu Zhipeng
• Huang Peng
• Li Pingshan
• Liu Yunfei

Classifications

• E21F15/00 Primary

  Methods or devices for placing filling-up materials in underground workings (dams E21F17/103 {; chocks made of flexible containers filled with backfilling material E21D15/483}) · CPC title

• E21C41/16

  Methods of underground mining (winning machines therefor E21C25/00 - E21C39/00); Layouts therefor · CPC title