AU2021355609B2

AU2021355609B2 - Method for mining by filling and caving

Info

Publication number: AU2021355609B2
Application number: AU2021355609A
Authority: AU
Inventors: Qingping CHAI; Guohui GONG; Wensheng Liu; Dong Ma; Anlin SHAO; Zhiyu Xie; Liansheng XU
Original assignee: Ansteel Group Mining Corp Ltd
Current assignee: Ansteel Group Mining Corp Ltd
Priority date: 2021-05-28
Filing date: 2021-11-22
Publication date: 2023-08-10
Anticipated expiration: 2041-11-22
Also published as: CN113202475A; CN113202475B; WO2022247176A1; AU2021355609A1

Abstract

The present invention discloses a method for mining by filling and caving, overcoming the problems of serious ore loss and dilution, surface subsidence existing in the non-pillar sublevel caving method, and a new problem of ore loss and dilution caused by 5 the dry gravels and tailings filled with on the top. The overlying rocks formed by the non-pillar sublevel caving method are grouted to form a layer of grouted overlying rocks the thickness of which is equal to the height of two sublevels formed by the non-pillar sublevel caving method. Ore mining is carried out by non-pillar sublevel caving method under the grouted overlying rocks, so that the grouted overlying rocks completely wrap the 10 new caving ores. In the process of ore drawing, it not only prevents the waste rocks from the front of the drawing ores from mixing into them, but also prevents the gravels and tailings filled with on the top from passing through the new caving ores to mix into the drawing ores. And arched suspension beams are constructed on the roof of the goaf, and the goaf is intensively filled from the top through a filling blind ore pass. The method has the 15 advantages such as simple mining process, high mining intensity, high efficiency, high mechanization, safety, low mining costs, non-surface subsidence, and low ore loss and dilution, and is applicable to all underground mining of metal ores.

Description

METHOD FOR MINING BY FILLING AND CAVING FIELD OF THE INVENTION

The present disclosure belongs to the technical field of filling mining for underground

mines, relating to a method for mining by filling and caving.

BACKGROUND OF THE INVENTION

An underground mining method includes three essential process steps of mining

preparation, cutting and mining. According to the maintenance way of earth pressure, the

underground mining methods include three categories of an open stope mining method, a

filling mining method and a caving mining method.

Under the current requirements of environmental protection, all mines are

recommended to adopt the filling method. The traditional open stope mining method, for

example, requires subsequent filling to prevent surface subsidence. However, the filling

method involves mining under a large exposed area with poor safety and complicated

filling processes, which requires processes such as water filtration, cementation and

maintenance, having disadvantages of low production capacity as well as high costs.

As a representative of the caving method, a non-pillar sublevel caving method has the

advantages such as simple process structure, high mining intensity, high efficiency, high

mechanization, safety, and low mining costs. This method is popularized around the world,

but still has two critical defects of serious ore loss and dilution and surface subsidence.

Is there a better mining method having safety, low cost and high production efficiency,

as well as without surface subsidence to be ascribed?

If the problems of serious ore loss, dilution and surface subsidence existing in the

non-pillar sublevel caving method were solved, the above requirements will basically be

met.

Firstly, the problem of serious ore loss and dilution existing in the non-pillar sublevel

caving method is analyzed.

In the standard non-pillar sublevel caving method, the ore body is divided into several

stages, which are then divided into several sublevels by means of mining roadways to mine

sublevel by sublevel from top to bottom. The operations such as drilling, caving and ore

removal in each sublevel are all carried out in the mining roadway, mining from the tail end to the start of the mining roadway in a backward manner. Each mining operation covers a small a small caving space of generally 1.5m-2m.

Drawing ore of the caving ores under the overburden stratum, the ores will be mixed

with the rocks during ore drawing due to directly contact ores with rocks, resulting in

serious ore loss and dilution during ore drawing. The problem of serious ore loss and

dilution during ore drawing under the overburden stratum has not been well solved, which

is a major problem that plagues the mining industry.

Drawing ore under the overburden stratum may be mixed with waste overburden

rocks from the front, top and sides of the ores. A lot of practices show that the most waste

overburden rocks are mixed from the front of the ores. The ore loss and dilution will be

greatly reduced as long as the waste rocks from the front can be prevented from mixing

with the ores. If slurries are grouted into the overlying rocks to build the grouted

overburden stratum, the ore drawing under the grouted overburden stratum can effectively

prevent the waste rocks on the front from mixing with the ores, thereby solving the

problem of the serious ore loss and dilution during ore drawing existing in the non-pillar

sublevel caving method.

For mines built by the non-pillar sublevel caving method, due to very thick overlying

rocks, grouting the whole overlying rocks requires significant costs. Therefore, the

overlying rocks of the lower sublevel are grouted from the upper sublevel only during the

mining process. According to the safety requirements of the non-pillar sublevel caving

method, the mining at the upper sublevel must precede that at the lower sublevel by 20m,

or mining sublevel-by-sublevel. The grouting position has been covered by the overlying

rocks to form an area closed by the overlying rocks, and personnel cannot enter the

grouting position. In the non-pillar sublevel caving method, each mining covers a small

caving space, the position of the grouting requires to be changed along with the mining of

each caving space. Therefore, grouting overlying rocks of the non-pillar sublevel caving

method has the problem of the area being closed by the overlying rocks, long distances, and

position changing, which is a difficult problem.

Secondly, the problem of surface subsidence existing in the non-pillar sublevel caving

method is analyzed.

For the non-pillar sublevel caving method, a goaf will be formed above the overburden stratum along with ore drawing. With the increase of mining scope and mining depth, the area of the goaf also gradually grows. When the roof of the goaf exceeds the allowable exposed area, the rocks surrounding the roof of the goaf are destroyed and collapse, and the deformation and destruction of the rocks surrounding the roof continues growing upwards until reaching to the surface, resulting in surface subsidence.

The most effective way to solve the problem of surface subsidence is to fill the goaf,

that is, the goaf isfilled from the top with backfill such as waste rocks and mill tailings.

However, filling the goaf has a problem that the backfill cannot be in contact with the roof

of the goaf. As the goaf cannot be fully filled, the roof will continue to deform and collapse

until the surface is destroyed. Therefore, how to fully fillthe goaf to contact the roof is a

key to solving the problem of surface subsidence in the non-pillar sublevel caving method.

In addition, it brings some new problems as the goaf is filled from the top with waste

rocks and mill tailings to bear earth pressure. As the ore body at the lower part is mined by

non-pillar sublevel caving method, the dry waste rocks and mill tailings filled with from the

top of the goaf are easily mixed into the drawing ores during ore drawing, particularly the

mill tailings. The mill tailings' particulates are very fine, so that a large amount of mill

tailings will pass through the new caving ores to mix into the drawing ores, deteriorating

the ore drawing effect.

In summary, in order to solve the problems of serious ore loss and dilution and surface

subsidence existing in the non-pillar sublevel caving method, methods of grouting

overlying rocks and filling the goaf from the top through a filling well can be adopted

respectively. However, it is necessary to solve problems caused by grouting such as the

area being closed by the overlying rocks, long distances, and position changing, and

problem of roof-contact of the goaf, and problem of serious ore loss and dilution caused by

the gravels and tailings filled with from the top of the goaf mixed into the drawing ores.

SUMMARY OF THE INVENTION

To solve the problems existing in the above-mentioned caving mining method and

filling mining method, it is an object of the present invention to provide a method for

mining by filling and caving to disclose a newfilling mining method having characteristics

such as less ore loss and dilution, low costs, safety, high efficiency and non-surface

subsidence.

The object of the present invention includes the following technical solutions:

A method for mining by filling and caving includes mining ore by a non-pillar

sublevel caving under grouted overlying rocks, constructing arched suspension beams on

the roof of a goaf, and intensively filling the goaf from the top through a filling blind ore

pass, wherein the method includes the following steps:

Si: Constructing the arched suspension beams on the roof of the goaf and arranging a

filling system

The roof of the goaf formed by mining ore through the non-pillar sublevel caving

method is burst into several arched suspension beams using a blasting method, wherein the

arched suspension beams is composed of arches and a vertical beams. Several filling blind

ore passes connected to the goaf are arranged at a height position above 50m over the

centers of the arches of all the arched suspension beams of the roof of the goaf, wherein

each filling blind ore pass is connected to the ground through a filling blind ore pass

connecting channel and a ground filling well. And a filling system is built on the ground,

wherein the filling system includes a filling material bin, a filling material mixing plant,

and a filling material conveying line which conveys a filling material source to the filling

blind ore pass via the filling material bin, the filling material mixing plant, the ground

filling well and the filling blind ore pass connecting channel;

S2: Pre-burying grouting pipes

Deep ditches are excavated along full length at both sides of the bottom of the

uppermost sublevel mining roadway of the non-pillar sublevel caving method for mining

ore and extended to the uppermost sublevel connecting channel. A grouting pipe, formed by

sleeving an inner pipe with an outer pipe, is buried into each deep ditch. The grouting pipe

is extended out of the ground at the uppermost sublevel connecting channel, wherein the

inner pipe of the grouting pipe is connected to grouting equipment by means of joint pipes.

The deep ditch is filled with the slag from working face and the surface is then cemented

and sealed with concrete, such that the pre-burying processes of the grouting pipes of all

the uppermost sublevel mining roadways are completed after the concrete dry completely;

The uppermost sublevel and the second sublevel are then mined through the

traditional non-pillar sublevel caving method, when a fan-shaped medium-deep hole is

arranged in the second sublevel mining roadway, the distance between the bottom of the fan-shaped medium-deep hole and the grouting pipe pre-buried at the uppermost sublevel is greater than 0.5m;

S3: Grouting overlying rocks

When mining is carried out to the third sublevel mining roadway, retreating mining is

carried out from the tail end to the entry end of the third sublevel mining roadway. After

ore drawing for mining of one caving space is completed, the overlying rocks that fall to

the end of the working face are grouted at the end of the working face of the current third

sublevel mining roadway by the grouting equipment through the grouting pipe at the

uppermost sublevel connecting channel until the slurry flows out of the working face, and

then the grouting pipe is washed by injecting water for 1 to 2 minutes. The inner pipe of the

grouting pipe at the grouting equipment is pulled out by a length of one caving space and

the grouting outlet is adjusted to a grouting position for the next caving space, and then the

next caving space is mined. Grouting is carried out again and mining until the current third

sublevel mining roadway is completely mined, such that the overlying rocks at the current

third sublevel mining roadway are grouted completely. The mining and grouting overlaying

rocks at all the third sublevel mining roadways are completed in the same way.

S4: Filling the goaf

The goaf is filled with the gravel and tailings backfill through the filling blind ore

pass;

S5: Mining other sublevels

A fourth sublevel and the lower sublevels are mined by the traditional non-pillar

sublevel caving method.

S6: filling new goafs in time

along with the mining of the ore body in step S5, the overlying rocks and the gravel

and tailings backfill move downward and a new goaf appears on an upper part. The new

goaf is filled in time by means of repeating step S4 to keep it stuffed.

Preferably, bursting the roof of the goaf formed by ores mining by the non-pillar

sublevel caving into several arched suspension beams using a blasting method is to

excavate a drilling roadway along the strike of the ore body in the surrounding rock on the

goaf side, wherein the horizontal distance between the drilling roadway and the goaf side is

10 to 20 m, and the bottom of the drilling roadway is at the same height as the bottom of the roof of the goaf. Beam-shaped blastholes are arranged straight opposite to the center position of arch of each arched suspension beam to be burst in the drilling roadway, so that the roof forms the arched suspension beam structure having suspension beams by blasting method.

Preferably, the arched suspension beams are composed of the arches and the vertical

beams. The area of the arch of each arched suspension beam is S'=KS, the length L of the

arch is equal to the thickness of the ore body, a span is W=S'/L, and the total height from

the top of the arch to the bottom of the vertical beam is H= Wtana/2+b, the width d of the

vertical beam is 4 to 8 m, the length thereof is equal to the thickness of the ore body, and b

is the distance between the bottom of the arch and the bottom of the vertical beam, usually

ranging from 1 to 3m;

wherein, S' represents the area of the arch of each arched suspension beam, S

represents an allowable exposed area ensuring the stability of the roof, K represents the

area coefficient ranging from 0.3 to 0.9, a represents a natural repose angle of the gravel

and tailings backfill that filled on the top.

Preferably, the arch of the arched suspension beam has a cross-sectional shape such as

circular arc, three-centered arch or triangular arch.

Preferably, the diameters of the filling blind ore pass and the ground filling well range

from 2 to 4 m.

Preferably, the depth of the deep ditch ranges from 30 to 50 cm and the width of the

deep ditch is larger than the diameter of the outer pipe of the grouting pipe.

Preferably, the outer pipe of the grouting pipe is made of PPR pipe material having a

diameter ranging from 2 to 2.5 inches. And 2 to 4 rows of grouting holes having a diameter

of 0.5 to 1 cm are arranged along full length on the lower part and sides of the outer pipe,

and the outer pipe is connected with each other by means of hot melt. The inner pipe is a

continuous jointless rubber tube having a diameter of 3/4 or 1 inch. The inner pipe is

inserted into the outer pipe, both having the same length.

Preferably, the grouting equipment employs a water pump or a grouting machine.

Preferably, the grouting material used for grouting is solid sodium silicate which is

dissolved in water to prepare a grouting solution before grouting, wherein the mass ratio of

the solid sodium silicate to water is 1:(5-20), and the volume ratio of once grouting amount to the overlying rocks to be grouted is 1: (5-20).

Preferably, filling the with the gravel and tailings backfill through the filling blind ore

pass in the step 4, wherein the lumpiness of the gravels is less than 0.5 m, and the mass

ratio of the gravels to the tailings is 1: (0-3).

The new high-efficiency method for mining by filling and caving provided in the

present invention has the advantages such as simple mining process structure, high mining

intensity, high efficiency, high mechanization, safety, low mining costs, non-surface

subsidence and low ore loss and dilution, and is applicable to all underground mining of

metal ores.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG.1 is a schematic diagram of constructing the arched suspension beam structure on

the roof of the goaf and thefilling system arrangement.

FIG.2 is an effect diagram of bursting the roof of the goaf into the arched suspension

beam structure.

FIG. 3 is an effect diagram of grouting the overlying rocks when mining the third

sublevel.

FIG.4 is an effect diagram of intensively filling the goaf after grouting the overlying

rocks.

FIG.5 is a schematic diagram of the grouting pipe arrangement.

FIG.6 is a schematic diagram of arrangement of the deep ditch and the grouting pipes

in the mining roadway.

FIG.7 is a schematic diagram of the grouting equipment arranged in the uppermost

sublevel connecting channel.

FIG.8 is a horizontal cross-sectional schematic diagram of arrangement of the

grouting pipes.

FIG.9 is a schematic diagram showing the combination of the inner pipe and the outer

pipe, and the grouting holes on grouting pipe.

FIG.10 is a schematic diagram of constructing the arched suspension beam structure

on the roof by blasting method.

FIG.11 is a schematic diagram of the dimension of the arched suspension beam

structure on the roof.

DETAILED DESCRIPTION OF EMBODIMENTS

The embodiments of the present invention will now be described in detail with

reference to the accompanying drawings.

As shown in FIGs.1 and 2, the method for mining by filling and caving provided in

the present invention includes mining ore by a non-pillar sublevel caving under the grouted

overlying rocks 14, constructing arched suspension beams on the roof of the goaf, and

intensively filling the goaf from the top through the filling blind ore passes, wherein the

method includes the following steps:

SI: Constructing the arched suspension beams on the roof of the goaf and arranging

the filling system.

The roof 1 of the goaf 8 formed by mining ore through the non-pillar sublevel caving

arched suspension beams are composed of the arches 3 and the vertical beams 2. Several

filling blind ore passes 4 connected to the goaf 8 are arranged at the height position above

50 m over the centers of the arches 3 of all the arched suspension beams of the roof of the

goaf 8, wherein each filling blind ore pass 4 is connected to the ground 7 through the filling

blind ore pass connecting channel 5 and the ground filling well 6. And a filling system is

built on the ground 7, wherein the filling system includes a filling material bin, a filling

material mixing plant, and a filling material conveying line which conveys the filling

material source to the filling blind ore passes 4 via the filling material bin, the filling

material mixing plant, the ground filling well 6 and the filling blind ore pass connecting

channel5.

As shown in FIGs. 1 and 10, a blasting method is used to burst the roof 1 of the goaf 8

formed by ore mining through a non-pillar sublevel caving method into several arched

suspension beam structures, and to excavate the drilling roadway 16 along the strike of the

ore body in the surrounding rock on the side of the goaf 8, wherein the horizontal distance

between the drilling roadway 16 and the side of the goaf 8 is 10 to 20 m, and the bottom of

the drilling roadway 16 is at the same height as the bottom of the roof 1 of the goaf 8. The

beam-shaped blastholes 17 are arranged straight opposite to the center positions of the

arches 3 of each arched suspension beams to be burst in the drilling roadway 16, and the

rocks inside the arched suspension beams are burst using the blasting method, so that the roof forms an arched suspension beam having suspension beams. S2: Pre-burying grouting pipes. As shown in FIGs.3, 5, 6, 7, 8 and 9, the deep ditches 12 are excavated along full length on both sides of the bottom of each uppermost sublevel mining roadway 10 of the non-pillar sublevel caving for mining ore and extended to the uppermost sublevel connecting channel 18. The grouting pipe 13, formed by sleeving an inner pipe 21 with an outer pipe 20, is buried into each deep ditch 12. The outer pipe 20 of the grouting pipe 13 is made of PPR pipe material having a diameter ranging from 2 to 2.5 inches. And 2 to 4 rows of grouting holes 22 having a diameter of 0.5 to 1 cm are arranged along full length at the lower part and sides of the outer pipe 20, wherein the outer pipe 20 is connected with each other by means of hot melt. The inner pipe 21 is a continuous jointless rubber tube having a diameter of 3/4 or 1 inch. The inner pipe 21 is inserted into the outer pipe 20, both having the same length. Employing the continuous rubber tube for the inner pipe 21 facilitates smooth extraction of the inner pipe 21 from the outer pipe 20 when adjusting a grouting outlet.

The grouting pipe 13 is extended out of the ground at the uppermost sublevel connecting roadway 18, wherein the inner pipe 21 of the grouting pipe 13 is connected to the grouting equipment 19 by joint pipes. The deep ditch 12 is filled with the slag from the working face and the surface is then cemented and sealed with concrete, such that the pre-burying processes of the grouting pipes 13 of all the uppermost sublevel mining roadways 10 are completed after the concrete dry completely. The uppermost sublevel and the second sublevel are then mined through the traditional non-pillar sublevel caving method. As shown in FIG. 5, when the fan-shaped medium-deep hole 25 is arranged in the second sublevel mining roadway 23, the distance between the bottom of the fan-shaped medium-deep hole 25 and the grouting pipe 13 pre-buried at the uppermost sublevel is greater than 0.5m, preventing the pre-buried grouting pipe 13 from being blown up. As shown in FIGs.1, 2 and 11, the arched suspension beams are composed of the arches 3 and the vertical beams 2. The area of the arch 3 of each arched suspension beam is S'=KS, the length L of the arch 3 is equal to the thickness of the ore body, the span is W=S'/L, and the total height from the top of the arch 3 to the bottom of the vertical beam 2 is H= Wtana /2+b, the width d of the vertical beam 2 is 4 to 8 m, and the length thereof is equal to the thickness of the ore body, and b is the distance between the bottom of the arch

3 and the bottom of the vertical beam 2, usually ranging from 1 to 3 m;

wherein, S' represents the area of the arch 3 of each arched suspension beam, S

represents the allowable exposed area ensuring the stability of the roof, K represents the

area coefficient ranging from 0.3 to 0.9, a represents the natural repose angle of the gravel

and tailings backfill that filled on the top.

The arch 3 of the arched suspension beam has a cross-sectional shape such as circular

arc, three-centered arch or triangular arch, or other shapes required according to the actual

engineering.

The diameters of the filling blind ore pass 4 and the surface filling well 6 range from 2

to 4 m.

As shown in FIG. 6, the depth of the deep ditch 12 ranges from 30 to 50 cm and the

width larger than the diameter of the outer pipe 20 of the grouting pipe 13, which enable to

smoothly bury the grouting pipe 13.

S3: Grouting overlying rocks.

As shown in FIG. 3, when mining is carried out to the third sublevel mining roadway

15, retreating mining is carried out from the tail end to the entry end of the third sublevel

mining roadway 15. After ore drawing for mining of one caving space is completed, the

overlying rocks 9 fall to the end of the working face and are grouted at the end of the

working face of the current third sublevel mining roadway 15 by the grouting equipment 19

through the grouting 13 at the uppermost sublevel connecting roadway 18 until the slurry

flows out of the working face, and then the grouting pipe 13 is washed by injecting water

for 1 to 2 minutes. The inner pipe 21 of the grouting pipe 13 at the grouting equipment 19

is pulled out by a length of one caving space and the grouting outlet is adjusted to the

grouting position for the next caving space, and then the next caving space is mined.

Grouting is carried out again and mining until the current third sublevel mining roadway 15

is completely mined, such that the overlying rocks at the current third sublevel mining

roadway are grouted completely. The mining and grouting overlaying rocks at all the third

sublevel mining roadways are completed in the same way. The pre-buried grouting pipe 13

at the uppermost sublevel is used to grout the third sublevel instead of the second sublevel so as to increase the grouting thickness of the overlying rocks, so that the thickness of the grouted overlying rocks reach the height of two sublevels formed by the non-pillar sublevel caving method.

The grouting equipment 19 employs a water pump or a grouting machine.

The grouting material used for grouting is solid sodium silicate which is dissolved in

water to prepare a grouting solution before grouting, wherein the mass ratio of solid sodium

silicate to water is 1 : (5-20), and the volume ratio of once grouting amount to the overlying

rocks to be grouted is 1 : (5-20).

S4: Filling the goaf.

The goaf 8 is filled with the gravel and tailings backfill 11 through the filling blind ore

pass 4, where the lumpiness of the gravels is less than 0.5 m, and the mass ratio of the

gravels to the tailings is 1 : (0-3).

S5: Mining ores at the other sublevels and S6: filling new goafs in time.

The fourth sublevel and the lower sublevels are mined by the traditional non-pillar

sublevel caving method. However, the overlying rocks are the grouted overlying rocks, and

the thickness of the grouted overlying rocks must reach the height of two sublevels formed

by the non-pillar sublevel caving method, so that the grouted overlying rocks completely

wrap the new caving ores. In the process of ore drawing, it not only prevents the waste

rocks from the front of the drawing ores from mixing into them, but more importantly

prevents the gravels and tailings filled with on the top from passing through the new caving

ores to mix into the drawing ores. In the case that the ore body is mined, the overlying

rocks and the gravel and tailings backfill 11 move downward and a new goaf appears on an

upper part. The new goaf is filled in time to keep it stuffed by repeating step S4, as the ore

body is mined in step S5; i.e. the new goaf is progressively filled with the gravel and

tailings backfill 11 as per step S4 to keep it full, belonging to the dynamic process for the

goaf, as shown in FIG.4, wherein 24 indicates the fourth sublevel mining roadway.

Claims

What is claimed is:

1. A method for mining by filling and caving, comprising mining ore by a non-pillar

sublevel caving method under grouted overlying rocks, constructing arched suspension

beams on the roof of a goaf formed by the non-pillar sublevel caving method, and

intensively filling the goaf from a top through a filling blind ore pass, wherein the method

comprises the following steps of:

filling system

using a blasting method to burst the roof of the goaf into several arched suspension

beams composed of arches and vertical beams; arranging, at a height position above 50 m

over the centers of the arches of all arched suspension beams of the roof of the goaf,

several filling blind ore passes connected to the arches, wherein each filling blind ore pass

is connected to the ground through a filling blind ore pass connecting channel and a ground

filling well; and building a filling system on the ground, wherein the filling system

comprises a filling material bin, a filling material mixing plant, and a filling material

conveying line which conveys a filling material source to the filling blind ore pass via the

filling material bin, the filling material mixing plant, the ground filling well and the filling

blind ore pass connecting channel;

S2: pre-burying grouting pipes

excavating deep ditches along full length at both sides of a bottom of each uppermost

sublevel mining roadway formed by the non-pillar sublevel caving method and extending

them to an uppermost sublevel connecting channel, and burying a grouting pipe into each

deep ditch, wherein the grouting pipe is formed by sleeving an inner pipe with an outer

pipe; enabling the grouting pipe to extend out of the ground at the uppermost sublevel

connecting channel, connecting the inner pipe of the grouting pipe to a grouting equipment

by means of joint pipes, filling the deep ditch with slag from a working face and then

cementing and sealing a surface with concrete, such that the pre-burying processes of the

grouting pipes of all the uppermost sublevel mining roadways are completed after the

concrete dries completely;

and then mining an uppermost sublevel and a second sublevel through the non-pillar

sublevel caving method, wherein a fan-shaped medium-deep hole is arranged in a second sublevel mining roadway, and a distance between a bottom of the fan-shaped medium-deep hole and the grouting pipe pre-buried at the uppermost sublevel is greater than 0.5m; S3: grouting overlying rocks mining to a third sublevel mining roadway, and carrying out retreating mining from a tail end to an entry end of the third sublevel mining roadway; after completing drawing ore from one caving space, the overlying rocks that fall to an end of the working face are grouted at the end of the working face of the third sublevel mining roadway by the grouting equipment through the grouting pipe at the uppermost sublevel connecting channel until slurry is flowing out of the working face, and then washing the grouting pipe by injecting water for 1 to 2 minutes; pulling out the inner pipe of the grouting pipe at the grouting equipment by a length of one caving space and adjusting a grouting outlet to a grouting position for a next caving space, and then mining the next caving space, repeating the grouting and mining steps until the current third sublevel mining roadway is completely mined, such that the overlying rocks at the current third sublevel mining roadway are grouted completely, and mining and grouting overlaying rocks at all the third sublevel mining roadways are completed in the same way; S4: filling the goaf filling the goaf with a gravel and tailings backfill through the filling blind ore pass; S5: mining ores at other sublevels mining a fourth sublevel and lower sublevels by the non-pillar sublevel caving method; and S6: filling new goafs in time as the ore body is mined according to step S5, where the overlying rocks and the gravel and tailings backfill move downward and a new goaf appears on an upper part, filling the new goaf progressively by repeating step S4 to keep it full.

2. The method for mining by filling and caving according to claim 1, wherein the bursting the roof of the goaf excavates a drilling roadway along a strike of the ore body in the surrounding rock on a goaf side, wherein a horizontal distance between the drilling roadway and the goaf side is 10 to 20m, and a bottom of the drilling roadway is at the same height as a bottom of the roof of the goaf; and wherein beam-shaped blastholes are arranged straight and opposite to a center position of each arched suspension beam to be burst in the drilling roadway, so that the roof forms the arched suspension beam structure having suspension beams by blasting method.

3. The method for mining by filling and caving according to claim 1, wherein an area of the arch of each arched suspension beam is S'=KS, a length L of the arch is equal to a thickness of the ore body, a span is W=S'/L, and a total height from a top of the arch to a bottom of the vertical beam is H= Wtana/2+b, a width d of the vertical beam is 4 to 8m and a length thereof is equal to the thickness of the ore body; b is a distance between a bottom of the arch and the bottom of the vertical beam and ranges from 1 to 3m, wherein S' represents the area of the arch of each arched suspension beam, S represents an allowable exposed area ensuring the stability of the roof, K represents an area coefficient ranging from 0.3 to 0.9, and a represents a natural repose angle of the gravel and tailings backfill filled on the top of the arch.

4. The method for mining by filling and caving according to claim 1, wherein the arches of the arched suspension beam each have a cross-sectional shape of a circular arc, a three-centered arch or a triangular arch.

5. The method for mining by filling and caving according to claim 1, wherein diameters of the filling blind ore pass and the ground filling well range from 2 to 4 m.

6. The method for mining by filling and caving according to claim 1, wherein a depth of the deep ditch ranges from 30 to 50 cm and a width of the deep ditch is larger than a diameter of the outer pipe of the grouting pipe.

7. The method for mining by filling and caving according to claim 1, wherein the outer pipe of the grouting pipe is made of PPR pipe material having a diameter ranging from 2 to 2.5 inches, wherein 2 to 4 rows of grouting holes having a diameter of 0.5 to lcm are arranged along a full length on a lower part and sides of the outer pipe, and the outer pipe is connected with each other by hot melt; the inner pipe is a continuous jointless rubber tube having a diameter of 3/4 or 1 inch; and the inner pipe is inserted into the outer pipe, both having the same length.

8. The method for mining by filling and caving according to claim 1, wherein the grouting equipment employs a water pump or a grouting machine.

9. The method for mining by filling and caving according to claim 1, wherein the grouting material used for grouting is solid sodium silicate which is dissolved in water to prepare a grouting solution before grouting, wherein a mass ratio of the solid sodium silicate to water is 1:(5-20), and a volume ratio of once grouting amount to the overlying rock to be grouted is 1: (5-20).

10. The method for mining by filling and caving according to claim 1, wherein in step

S4, a lumpiness of the gravels is less than 0.5 m, and a mass ratio of the gravels to the

tailings is 1: (0-3).