CN115341935A

CN115341935A - Method for improving anchoring force of small coal pillar

Info

Publication number: CN115341935A
Application number: CN202210899148.8A
Authority: CN
Inventors: 刘跃东; 王东攀; 焦健康; 袁伟茗
Original assignee: Ccteg Coal Mining Research Institute Co ltd; Tiandi Science and Technology Co Ltd
Current assignee: Ccteg Coal Mining Research Institute Co ltd; Tiandi Science and Technology Co Ltd
Priority date: 2022-07-28
Filing date: 2022-07-28
Publication date: 2022-11-15

Abstract

The invention relates to the technical field of coal mining, and provides a method for improving the anchoring strength of a small coal pillar, which comprises the following steps: drilling holes are formed in the coal pillar side roadway side to the coal pillar, and the length of each drilling hole is smaller than the width of the coal pillar; delivering the bag inserted with the grouting pipe and the anchor cable into the drill hole; injecting grouting liquid into the bag through the grouting pipe, and tensioning and locking the anchor cable at the side roadway side of the coal pillar after the grouting liquid is solidified; wherein the bladder includes a deformable membrane that is permeable to water and air and resists the passage of slurry from the grouting fluid. According to the invention, pressurized grouting is carried out through the bag, and the small coal pillar can be anchored on one side based on the anchor cable, so that the safety and reliability of anchoring the small coal pillar are ensured, and the integral strength of the coal pillar is increased while the anchoring force is improved.

Description

Method for improving anchoring force of small coal pillar

Technical Field

The invention relates to the technical field of coal mining, in particular to a method for improving the anchoring strength of a small coal pillar.

Background

In the coal mining process, gob-side entry driving has good technical advantages and economic benefits, effectively relieves the shortage of mine working face replacement, and obviously improves the recovery rate of coal resources. The gob-side entry driving is to drive a roadway along the edge of a goaf or only leave a narrow coal pillar so as to arrange the roadway in a low stress field at one side close to the coal pillar, thereby facilitating roadway maintenance and reducing deformation. Because gob-side entry driving relies on the coal pillar to support the tunnel roof, need strengthen the intensive support to the coal pillar. In actual construction, reserved wide coal pillars or small coal pillars can be adopted to support the roadway roof according to field requirements.

Here, the retention mechanism of the wide coal pillar is: the strength of the coal body is greater than the overlying load, the strength of the coal body is closely related to the width of the coal pillar, and the coal pillar comprises 2 plastic zones and 1 elastic zone. Along with the increase of the buried depth of the working face, the range of the plastic zone is increased, the width of the reserved coal pillar needs to be increased, the waste of the coal pillar is caused, and therefore the concept of reserving the small coal pillar is provided.

The retention mechanism of the small coal pillar is as follows: the strength of the residual coal body is greater than that of the overlying load, the coal body is subjected to dynamic pressure influence, plastic damage is generated, the strength is reduced, meanwhile, the position of the coal body is located in the overlying load stress reduction area and is still less than that of the residual coal body, the roadway is allowed to deform to a certain extent, and the whole roadway is stable and usable. In order to improve the strength of the small coal pillar, external restraint can be provided for the small coal pillar by means of the anchor rod and the anchor cable, and the coal body can be reinforced by means of grouting and the like, so that the integrity of the small coal pillar is maintained.

In the correlation technique, because of the influence of working face dynamic pressure, most structures of the small coal pillar are in a plastic area, and the structures are broken, so that the small coal pillar is reinforced by generally adopting a bidirectional anchoring mode based on an anchor rod to control the large deformation of the small coal pillar. However, in practical application, the above-mentioned two-way anchoring manner is not reliable, and when the small coal pillar is influenced by the dynamic pressure of the working face and has a large deformation, the anchoring device is directly caused to exceed the pressure bearing range, so that the anchor cable is easily broken, the lock is easily bounced off, and the like, thereby causing safety accidents.

Disclosure of Invention

The invention provides a method for improving the anchoring force of small coal pillars, which is used for solving the problem that the small coal pillars are difficult to be anchored safely and reliably at present.

The invention provides a method for improving the anchoring strength of small coal pillars, which comprises the following steps:

drilling holes are formed in the coal pillar side roadway side to the coal pillar, and the length of each drilling hole is smaller than the width of the coal pillar;

delivering the bag inserted with the grouting pipe and the anchor cable into the drill hole;

injecting grouting liquid into the bag through the grouting pipe, and tensioning and locking the anchor cable at the side roadway side of the coal pillar after the grouting liquid is solidified;

wherein the bladder comprises a deformable membrane that is permeable to water and air and resists the passage of slurry from the grouting fluid.

According to the method for improving the anchoring force of the small coal pillar, the drill hole is arranged on the coal pillar side roadway to the coal pillar, and the method comprises the following steps:

collecting geological parameters of the coal pillar;

determining the geometric parameters of the drill hole according to the geological parameters;

and according to the geometric parameters, drilling construction is carried out on the coal pillar along the side lane of the coal pillar.

According to the method for improving the anchoring force of the small coal pillar, provided by the invention, the geological parameters comprise fracture development information of the coal pillar and rock mass strength; the geometrical parameters of the drill hole comprise the open hole position, the drilling direction and the drilling length of the drill hole.

and a plurality of drill holes are arranged at intervals towards the coal pillar along the stoping direction of a stoping working face, and the distance between two adjacent drill holes is predetermined or determined according to the geological parameters.

According to the method for improving the anchoring force of the small coal pillar, the grouting pressure of the grouting liquid is more than 3MPa.

According to the method for improving the anchoring strength of the small coal pillar, the grouting pressure is 3-5 MPa.

According to the method for improving the anchoring force of the small coal pillar, the bag extends along the length direction of the drill hole, and the length of the bag is determined according to the anchoring force between the bag and the coal pillar or the drawing force borne by the anchor cable.

According to the method for improving the anchoring strength of the small coal pillar, the diameter of the bag is larger than that of the drill hole, so that the outer side wall of the bag is abutted against the hole wall of the drill hole under the condition that the grouting liquid is filled in the bag.

According to the method for improving the anchoring force of the small coal pillar, provided by the invention, the anchor cable is arranged in the grouting pipe and is connected with the grouting pipe;

the first end of the grouting pipe is inserted into the bag, a grouting hole is formed in the first end of the grouting pipe, and the grouting pipe is communicated with the inner cavity of the bag through the grouting hole.

According to the method for improving the anchoring force of the small coal pillar, which is provided by the invention, the grouting pipe is provided with a first limiting piece and a second limiting piece, and the first limiting piece and the second limiting piece are arranged at intervals along the length direction of the grouting pipe;

the first end of the grouting pipe penetrates through the bag, and the bag is arranged between the first limiting part and the second limiting part.

According to the method for improving the anchoring strength of the small coal pillar, under-pressure grouting is carried out through the bag, the small coal pillar can be anchored on one side based on the anchor cable, the safety and the reliability of anchoring the small coal pillar are ensured, and the problem that the anchor cable is broken and the safety problem caused by the broken anchor cable when the existing small coal pillar is anchored on two sides is effectively solved.

Meanwhile, the pressurized grouting is carried out by adopting the bag, the flowing range of the grouting liquid can be controlled by the bag, the waste of the grouting liquid is reduced, the pressurized bag can extrude coal around the drill hole, the cementation of the coal in the hole wall range is improved, the stress concentration around the drill hole is reduced, the uniform diffusion of the stress is realized, the anchoring force is improved, and the integral strength of the coal pillar is increased.

Drawings

In order to more clearly illustrate the technical solutions of the present invention or the prior art, the drawings needed for the description of the embodiments or the prior art will be briefly described below, and it is obvious that the drawings in the following description are some embodiments of the present invention, and those skilled in the art can also obtain other drawings according to the drawings without creative efforts.

FIG. 1 is a schematic flow diagram of a method for improving the anchoring strength of a small coal pillar according to the present invention;

FIG. 2 is a schematic view of a small coal pillar anchored by the grouting pipe, anchor cable and bladder based anchoring device provided by the present invention;

fig. 3 is a schematic structural diagram of the anchoring device based on the grouting pipe, the anchor cable and the bladder provided by the invention.

Reference numerals:

100. a coal pillar; 200. tunneling along the gob; 300. stoping the working face; 400. an anchoring device; 500. directly ejecting; 600. a base top; 101. drilling;

41. a grouting pipe; 42. an anchor cable; 421. a guide head; 422. a lock assembly; 43. a pouch; 44. a first limit piece; 45. a second limiting member.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings, and it is obvious that the described embodiments are some, but not all embodiments of the present invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

A method of improving the anchoring of small coal pillars according to the present invention will be described with reference to fig. 1 to 3.

As shown in fig. 1 and fig. 2, this embodiment provides a method for improving anchoring strength of a small coal pillar, including the following steps:

and 110, drilling holes on the coal pillar side roadway side to the coal pillar, wherein the length of each drilling hole is smaller than the width of the coal pillar.

And step 120, delivering the bag inserted with the grouting pipe and the anchor cable into the drill hole.

Step 130, injecting grouting liquid into the bag through a grouting pipe, and stretching and locking the anchor cable at the side roadway side of the coal pillar after the grouting liquid is solidified; wherein the bladder includes a deformable membrane that is permeable to water and air and resists the passage of slurry from the grouting fluid.

As shown in fig. 2, the small coal pillar 100 is located between the gob-side entry driving 200 and the gob-side area, and a worker can support the small coal pillar 100 in the gob-side entry driving 200 to reduce the deformation of the small coal pillar 100. When the small coal pillars 100 are left, the strength of the residual coal bodies corresponding to the small coal pillars 100 is greater than the load of the direct roof 500 and the basic roof 600 covered on the small coal pillars 100.

Since both sides of the small coal pillar 100 are generally in a plastic zone, the strength of the coal body in the middle of the small coal pillar 100 is relatively large, and it can be considered that the middle of the small coal pillar 100 has an elastic zone. In the embodiment, the length of the drill hole 101 is smaller than the width of the coal pillar 100, so that the tail end of the drill hole 101 is located in the elastic area of the small coal pillar 100, pressurized grouting is performed through the bag 43, and the plastic area of the small coal pillar 100 can be anchored on one side based on the anchor cable 42 while the anchoring force between the bag 43 and the coal body is ensured.

Meanwhile, the deformable membrane of the embodiment can be formed by weaving warps and wefts, and both the warps and the wefts can be prepared by taking high-strength low-elongation synthetic fibers as raw materials. Wherein the synthetic fiber comprises synthetic fiber filaments such as polypropylene fibers, terylene and the like.

This embodiment can set up the density that warp and weft woven according to actual demand to make the deformable membrane possess and allow water and air to permeate through, and prevent the characteristic that the thick liquids in the slip casting liquid permeate through. That is, the bag of this embodiment has the characteristics that water and water are separated out, but do not separate out the thick liquid, and the slip casting is pressed in the area to the accessible bag, reduces the water cement ratio, improves grouting material's initial strength, increases the frictional force between the pore wall of bag and drilling to improve anchor power.

The grouting liquid of the present embodiment may be a cement-water-glass double-liquid slurry or a slurry made of other chemical materials that are easy to solidify. The present embodiment may determine the timing of tensioning the anchor line based on the setting time of the grout. After the slip casting liquid solidifies, this embodiment can be connected stretch-draw jack and the one end that the bag was kept away from to the anchor rope, stretch-draw anchor rope through stretch-draw jack, when the tensioning force of stretch-draw jack to the anchor rope reached the default, with the tool to lock on the anchor rope remove to the position with the coal pillar contact, thereby when stretch-draw jack and anchor rope separation, tool to lock and coal pillar butt, thereby carry out the locking to the anchor rope based on the tool to lock, and under the anchor effect of anchor rope and bag, realize the diffusion of pretightning force.

According to the invention, grouting is carried out under pressure through the bag, and the small coal pillar can be anchored on one side based on the anchor rope, so that the safety and reliability of anchoring the small coal pillar are ensured, and the problem of breakage of the anchor rope and safety caused by the breakage of the anchor rope when the existing small coal pillar is anchored on two sides is effectively solved.

In some embodiments, the drilling a hole in the pillar side roadway towards the pillar in this embodiment includes, but is not limited to, the following steps:

collecting geological parameters of the coal pillar;

and (4) according to the geometric parameters, drilling construction is carried out along the side roadway of the coal pillar to the coal pillar.

The geological parameters comprise fracture development information of the coal pillar and rock mass strength; the geometrical parameters of the borehole include the location of the opening of the borehole, the drilling direction and the drilling length.

Specifically, this embodiment can construct a inspection hole on the coal pillar in advance before drilling, surveys the crack development information of coal pillar through the drilling peep appearance, surveys the rock mass intensity of coal pillar through drilling static penetrometer. Of course, the embodiment can also detect the fracture development information and the rock strength of the coal pillar in the drilling process.

In the construction process, the small coal pillar is influenced by dynamic pressure of a goaf, most of structures of a coal body are in a plastic zone, but the strength of the coal body inside the coal pillar is larger than that of the coal body of the coal pillar close to a roadway side. Therefore, the distribution positions of the elastic zone and the plastic zone of the small coal pillar can be determined based on comprehensive analysis of crack development information and rock mass strength, the hole opening position, the drilling direction and the drilling length of the coal pillar during drilling construction can be conveniently determined, and the reliability of unilateral anchoring of the plastic zone of the small coal pillar is further ensured.

In some embodiments, as shown in fig. 2, the drilling of the coal pillar in the side roadway of the coal pillar includes, but is not limited to:

a plurality of drill holes 101 are arranged at intervals on the coal pillar 100 along the recovery direction of the recovery working face 300, and the distance between two adjacent drill holes 101 is predetermined or determined according to geological parameters.

In practical application, in the case that the geological parameters of the coal pillar along the extraction direction have small differences, the present embodiment may arrange a plurality of drill holes side by side at the same intervals.

Under the condition that the geological parameter difference of the coal pillar along the recovery direction is relatively large, for example, in a preset distance, the plastic zone distribution of the coal pillar is concentrated, and the distribution area is large, and the embodiment adaptively reduces the distance between two adjacent drill holes for the concentrated plastic zone distribution while arranging a plurality of drill holes side by side.

Of course, the embodiment may also set at least one of the drilling position, the drilling direction and the drilling length of the drill hole according to the distribution positions of the plastic zone and the elastic zone.

In some embodiments, based on the characteristic that the bag has the water and water separation and the water and gas separation but does not separate the grout, in order to improve the anchoring force between the bag and the hole wall of the drill hole, the grouting pressure of the grouting liquid can be set to be more than 3MPa.

In one example, the grouting pressure may be 3 to 5MPa. The grouting pressure may be, but is not limited to, 3MPa, 3.5MPa, 4MPa, 4.5MPa, 5MPa, or the like.

In some embodiments, to enhance the anchoring force between the bladder and the wall of the borehole, the present embodiment may provide that the bladder extends along the length of the borehole, the length of the bladder being determined by the anchoring force between the bladder and the coal pillar or the pulling force experienced by the anchor cable.

At the same time, the diameter of the bladder is greater than the diameter of the bore hole so that the outer sidewall of the bladder abuts the wall of the bore hole when the bladder is filled with grout. Obviously, the longer the length of the bladder, the more pressure grouting the bladder and the greater the anchoring force between the bladder and the walls of the borehole after the grouting has set.

In one example, the present embodiment may provide a bore diameter of 30-35 mm and a capsular bag diameter of 45-55 mm. For example, the bore hole is 32mm in diameter and the capsular bag is 50mm in diameter.

In some embodiments, as shown in fig. 2 and 3, to anchor the small coal pillar 100, the present embodiment further provides an anchoring device 400, and the anchoring device 400 includes a grouting pipe 41, an anchor cable 42 and a bladder 43.

To facilitate delivery of bladder 43 to a predetermined location within borehole 101, the present embodiment may locate anchor cable 42 within grout tube 41 and connect with grout tube 41; the first end of the grouting pipe 41 and at least a part of the anchor cable 42 are inserted into the bag 43, the first end of the grouting pipe 41 is provided with a grouting hole, and the grouting pipe 41 is communicated with the inner cavity of the bag 43 through the grouting hole.

The grouting holes are formed in the circumferential wall of the grouting pipe 41, and the diameter of the grouting holes can be set according to the maximum diameter of the slurry in the grouting liquid. For example, the diameter of the grout holes may be 2 to 3 times the maximum diameter of the grout in the grout.

In this embodiment, the first end of the grouting pipe 41 and the first end of the anchor cable 42 may be connected into a whole, or the grouting pipe 41 and the anchor cable 42 may be integrated into an integrated structure, so that a grouting channel is formed between the grouting pipe 41 and the anchor cable 42. In this case, the present embodiment may locate at least a portion of anchor cable 42 within pocket 43.

Of course, in this embodiment, the anchor cable 42 may be disposed outside the grouting pipe 41, and the first end of the grouting pipe 41 and the first end of the anchor cable 42 are inserted into the bag 43 together.

To facilitate delivery of bladder 43 within bore 101, this embodiment may provide for a first end of anchor cable 42 to extend beyond a first end of grout tube 41 and a guide head 421 at the first end of anchor cable 42. Since the diameter of the guide head 421 is larger than the diameter of the grouting pipe 41, the guide head 421 also functions as a stopper to prevent the anchor cable 42 from being separated from the grouting pipe 41 when the anchor cable 42 is pulled.

Further, in order to stretch and lock the anchor cable 42, a lock assembly 422 is disposed at the second end of the anchor cable 42.

Wherein, the lock assembly 422 includes a tray, a self-aligning ball pad and a lock. The second end of the anchor cable 42 is sequentially inserted into the tray, the self-aligning ball pad and the lock. The tray includes grafting portion and backstop portion, and grafting portion and backstop portion are connected, and grafting portion is suitable for pegging graft in drilling 101, and one side that backstop portion faced grafting portion is suitable for the butt in the side of coal column 100.

When the tension of the tensioning jack on the anchor cable 42 reaches a preset value, the tray can be clamped at the opening position of the drill hole 101, and the aligning ball pad is arranged between the tray and the lock. So, when stretch-draw jack and anchor rope 42 separate, under the tension effect on anchor rope 42, the lateral wall butt of tray and little coal pillar 100, the tool to lock butt is kept away from the one end of tray in the aligning ball pad, and the tool to lock can prevent anchor rope 42 and remove towards the drilling to realize the locking to anchor rope 42 based on tool to lock subassembly 422.

At least part of the self-aligning ball pad shown in this embodiment is inserted into the central hole of the tray to ensure the coaxiality of the tray and the anchor cable 42, and the reliability of the lock for locking the anchor cable 42 through the tray can be ensured.

Further, in order to limit the bag 43, the grouting pipe 41 of the present embodiment is provided with a first limiting member 44 and a second limiting member 45, and the first limiting member 44 and the second limiting member 45 are arranged at intervals along the length direction of the grouting pipe 41; the first end of the grouting pipe 41 is inserted into the bag 43, and the bag 43 is disposed between the first and

second stoppers

44 and 45.

Specifically, the first stopper 44 and the second stopper 45 are both detachably mounted on the grouting pipe 41. When the bag 43 is pressurized and injected, the bag 43 can be expanded, and the bag 43 can be prevented from moving in the axial direction along the injection pipe 41 by the limit action of the first and

second limit members

44 and 45.

The first limiting member 44 and the second limiting member 45 may be limiting members, and the limiting members may be connected with the grouting pipes 41 through internal threads and external threads.

In some examples, the present embodiment may also connect one end of the bladder 43 to the first stop 44 and the other end of the bladder 43 to the second stop 45 to prevent the bladder 43 from moving axially along the injection tube 41 during delivery of the bladder 43 into the borehole 101.

It should be noted that in order to facilitate the field anchoring operation of the small coal pillar 100, the anchor cable 42 of the present embodiment may be a steel cable, and at least a portion of the grouting pipe 41 may be a flexible tubular structure. The bendable portion of the grout tube 41 communicates with a pumping device to pump grout into the grout tube 41 through the pumping device, the grout being guided by the grout tube 41 into the bladder 43.

For example, the injection tube 41 may include a hard section having one end inserted in the bladder 43 and the other end communicating with one end of a flexible section, the other end of the flexible section communicating with the pumping device.

Therefore, the anchoring method based on the bag 43 and the under-pressure grouting can effectively improve the anchoring force of the anchor cable, reduce the stress concentration around the drill hole 101 and increase the overall strength of the coal pillar 100.

The anchoring method disclosed by the invention is not only applied to small coal pillar roadways, but also applied to other roadways with insufficient anchoring force in shallow layers, such as soft and broken coal bodies. In addition, the anchoring method disclosed by the invention can also be applied to rock burst roadways. The rock burst roadway generally adopts the means of drilling, water injection, blasting, cracking and the like to form a weak structure, and the anchoring method disclosed by the invention can transfer or absorb high stress and high energy.

Finally, it should be noted that: the above examples are only intended to illustrate the technical solution of the present invention, and not to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, it should be understood by those of ordinary skill in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some technical features may be equivalently replaced; and such modifications or substitutions do not depart from the spirit and scope of the corresponding technical solutions of the embodiments of the present invention.

Claims

1. A method of improving the anchorage of a small coal pillar, comprising:

2. The method for improving small coal pillar anchoring strength of claim 1, wherein the drilling a hole on the coal pillar side roadway to the coal pillar comprises:

collecting geological parameters of the coal pillar;

3. The method for improving the anchoring strength of the small coal pillar according to claim 2, wherein the geological parameters comprise fracture development information of the coal pillar and rock mass strength; the geometrical parameters of the drill hole comprise the open hole position, the drilling direction and the drilling length of the drill hole.

4. The method for improving small coal pillar anchoring strength of claim 2, wherein the drilling a hole on the coal pillar side roadway to the coal pillar comprises:

5. The method for improving the anchoring strength of a small coal pillar according to any one of claims 1 to 4, wherein the grouting liquid has a grouting pressure of more than 3MPa.

6. The method for improving the anchoring force of the small coal pillar according to claim 5, wherein the grouting pressure is 3-5 MPa.

7. The method of any one of claims 1 to 4, wherein the length of the bladder is determined by the anchoring force between the bladder and the coal pillar or the pulling force applied to the anchor cable.

8. The method of claim 7, wherein the diameter of the bladder is greater than the diameter of the bore hole such that an outer sidewall of the bladder abuts a wall of the bore hole when the bladder is filled with grouting fluid.

9. The method for improving the anchoring strength of a small coal pillar according to any one of claims 1 to 4, wherein the anchor cable is arranged in the grouting pipe and connected with the grouting pipe;

10. The method for improving the anchoring force of the small coal pillar according to claim 9, wherein a first limiting member and a second limiting member are arranged on the grouting pipe, and the first limiting member and the second limiting member are arranged at intervals along the length direction of the grouting pipe;