Grouting bolt-cable composite beam and supporting method for advanced support of fractured surrounding rock in deep coal mines

Abstract

It discloses a grouting bolt-cable composite beam and supporting method for advanced support of fractured surrounding rock in deep coal mines. The quadrate plates are fixed at both ends of the steel beam, the anchor cable holes are arranged in the center of the steel beam and the quadrate plates, and the diameter of anchor bolt holes should be larger than that of the grouting cables. There are four anchor bolt holes on each quadrate plate, and each anchor bolt hole corresponds to a anchor plate, the horizontal surface of the anchor plate is close to the quadrate plate, and the arc parts of the four anchor plates are all facing the center of the quadrate plate.

Claims

1. A grouting bolt-cable composite beam for advanced support of fractured surrounding rock in coal mines, which is characterized in that includes a steel beam, grouting cables, grouting bolts, quadrate plates, anchor plates, fastening nuts and an anchor rigging; the anchor plates are wedge-shaped blocks, upper and lower surfaces of each of the wedge-shaped blocks is a horizontal and an inclined plane with an anchor bolt hole arranged in the middle, an angle of each of the wedge-shaped blocks ensures that each of the grouting bolts is perpendicular to the inclined plane; connection relationship of the above components is as follows: the quadrate plates are fixed at both ends of the steel beam, anchor cable holes are arranged in the center of the steel beam and the quadrate plates; there are four quadrate anchor bolt holes on each of the quadrate plates, and each of the quadrate anchor bolt holes corresponds to and is aligned to one of the anchor bolt holes of the anchor plates, horizontal surface of each of the anchor plates is close to one of the quadrate plates, and arc parts of four of the anchor plates are all facing center of the quadrate plates; each of the grouting bolt passes through one of the anchor bolt holes of one of the anchor plates and one of the quadrate anchor bolt holes of one of the quadrate plates, and is fixed in a roof by a first anchoring agent, and the free end of the bolt is applied with pretension through one of the fastening nuts; besides, each of the grouting cables passes through each of the anchor cable holes and is fixed in the overlying stable rock stratum by a second anchoring agent, and the free end of the cable is fixed by the anchor rigging.

2. The grouting bolt-cable composite beam for advanced support of fractured surrounding rock in the coal mines according to claim 1, which is characterized in that, wedge-shaped tips of the anchor plates are concave arc-shaped.

3. The grouting bolt-cable composite beam for advanced support of fractured surrounding rock in the coal mines according to claim 1, which is characterized in that, the anchor bolt holes on the quadrate plates are long round holes in order to adapt to boreholes with different inclinations.

4. The grouting bolt-cable composite beam for advanced support of fractured surrounding rock in the coal mines according to claim 1, wherein the grouting bolt-cable composite beam is used for supporting the fractured surrounding rock in the coal mines.

Description

DESCRIPTION OF FIGURES

(1) In order to illustrate the implementation of the invention or the prior technology more clearly, the figures used in the invention will be briefly described below.

(2) FIG. 1 is a structural schematic of the grouting bolt-cable composite beam for advanced support of fractured surrounding rock in deep coal mines.

(3) FIG. 2 is a structural schematic of quadrate plate and steel beam of the grouting bolt-cable composite beam for advanced support of fractured surrounding rock in deep coal mines.

(4) FIG. 3 is a structural schematic of anchor plate of the grouting bolt-cable composite beam for advanced support of fractured surrounding rock in deep coal mines.

(5) FIG. 4 is the elevation view of the grouting bolt-cable composite beam for advanced support of fractured surrounding rock in deep coal mines.

(6) FIG. 5 is the upward view of the grouting bolt-cable composite beam for advanced support of fractured surrounding rock in deep coal mines.

(7) FIG. 6 is a structural schematic of S3 of the grouting bolt-cable composite beam for advanced support of fractured surrounding rock in deep coal mines.

(8) FIG. 7 is a structural schematic of S4 of the grouting bolt-cable composite beam for advanced support of fractured surrounding rock in deep coal mines.

(9) FIG. 8 is a structural schematic of S5 of the grouting bolt-cable composite beam for advanced support of fractured surrounding rock in deep coal mines.

(10) FIG. 9 is the supporting effect of the grouting bolt-cable composite beam for advanced support of fractured surrounding rock in deep coal mines.

(11) FIG. 10 is the supporting profile of the grouting bolt-cable composite beam for advanced support of fractured surrounding rock in deep coal mines.

(12) FIG. 11 is the top view of grouting slurry diffusion of the grouting bolt-cable composite beam for advanced support of fractured surrounding rock in deep coal mines.

(13) FIG. 12 is the profile of grout diffusion in surrounding rock of grouting bolt along A-A direction.

(14) In the figures: 1—quadrate plate, 2—anchor plate, 3—steel beam, 4—anchor cable hole, 5—anchor bolt hole, 6—grouting bolt, 7—grouting cable, 8—roadway, 9—fastening nut, 10—anchor rigging, 11—working face, 12—goaf, 13—advanced abutment pressure zone, 131—shallow grouting zone, 132—deep grouting zone, 14—initial stress zone, 141—no-grouting zone, 15—distribution curve of advance abutment pressure, 16—bolt-grouting range, 17—cable-grouting range.

(15) Detail Implementation Method

(16) The preferred implementation detail of the invention is described based on the figures, to make the advantages and features of the invention easier to be understood by those skilled in the field. Thus, the protections cope of the invention can be defined more clearly.

(17) The anchor plate 2 used in the composite beam is shown in FIG. 3, which shows the state of four anchor plates 2 arranged on the quadrate plate 1. As shown in the figure, the anchor plate 2 is the wedge-shaped block, whose upper and lower surfaces are horizontal and inclined planes respectively with anchor bolt hole 5 arranged in the middle. The angle of wedge-shaped block should ensure that the grouting bolt 6 is perpendicular to the inclined plane of anchor plate 2, that is to say, the anchor bolt hole 5 is perpendicular to the anchor plate 2. The tip of wedge-shaped block is concave arc-shaped to avoid affecting the installation of the grouting cable 7 in the center of the quadrate plate 1.

(18) The grouting bolt-cable composite beam for advanced support of fractured surrounding rock in deep coal mines, as shown in FIG. 1-5. It includes steel beam 3, grouting cable 7, grouting bolt 6, quadrate plate 1, anchor plate 2, fastening nut 9 and anchor rigging 10. The quadrate plates 1 are welded and fixed at both ends of the steel beam 3, the anchor cable holes 4 are arranged in the center of the steel beam 3 and the quadrate plates 1, and the diameter of anchor cable holes 4 should be larger than that of the grouting cables 7. There are four anchor bolt holes 5 on each quadrate plate 1, the horizontal surface of the anchor plate 2 is close to the quadrate plate 1, and the arc parts of the four anchor plates 2 are all facing the center of the quadrate plate 1. The grouting bolt passes through the anchor plate 2 and quadrate plate 1 in turn, and is fixed in the roof by the anchoring agent, and the free end of the grouting bolt 6 is applied with pretension through the fastening nut 9. Besides, The grouting cable 7 passes through the anchor cable hole 4 and is fixed in the overlying stable rock stratum by the anchoring agent, and the free end of the grouting cable 7 is fixed by the anchor rigging 10.

(19) The anchor bolt hole 5 on the quadrate plate 1 is the long round hole in order to adapt to the boreholes with different inclinations. And the diameters of long round holes should be larger than that of the grouting bolts 6, so that the bolts can move in the long round holes to adapt to the angle changes of borehole. Meanwhile, it can improve the fault tolerance rate in the drilling construction process.

(20) In the FIG. 6-12, the grouting bolt-cable composite beam supporting method for advanced support of fractured surrounding rock in deep coal mines is as follows:

(21) S1. The Stress Relief Method is Used to Monitor the Advance Abutment Pressure of Working Face

(22) With the working face 11 advanced, the roof behind the working face gradually collapses and becomes goaf 12. Several boreholes are arranged in the roadway 8 along the coal seam strike within a certain range in the advanced working face (It is generally about 20 m). The relative change of surrounding rock stress is obtained by using borehole stressmeter, and then the distribution characteristics of advance abutment pressure are analyzed and the distribution curve of advance abutment pressure 15 is drawn, which is the advanced abutment pressure zone 13 shown in the figure.

(23) S2. Borehole Imaging Method is Used to Detect the Roadway Roof

(24) S2.1. Several boreholes are arranged at the roof along the coal seam strike within the advance abutment pressure zone 13. The fracture detection is carried out by using the borehole imaging method to obtain the height, range and damage degree of the roof fracture. According to the detection result, the borehole angle can be determined. Then, the matching anchor plate is selected based on the borehole angle.

(25) S2.2. Taking the midpoint of the borehole axis as the dividing line, the range from the orifice to the midpoint is defined as the shallow part, and the range from the midpoint to the bottom of the borehole is defined as the deep part. The S2.1 borehole imaging results were analyzed, including the number of fractures and the fracture opening degree. And the area between the first borehole with cracks in the shallow part and the first one in the deep part affected by the advanced abutment pressure is defined as the shallow grouting zone 131, as shown in FIG. 7 and FIG. 8. Similarly, the area between the first deep fracture borehole and the borehole closest to the peak stress is defined as the deep grouting zone 132, as shown in FIG. 8.

(26) S3. Reinforcement and Support Design for Roadway Beyond the Range of Advance Abutment Pressure

(27) S3.1. Row Spacing P of Composite Beam Determination

(28) As shown in FIG. 11-12, the maximum diffusion range K of grouting slurry of the grout bolit 6 in the surrounding rock is:
K=R+S

(29) Where R is the slurry diffusion radius when the grouting bolt 6 is vertically arranged, the unit is m; S is the slurry diffusion range when the grouting bolt is inclined, the unit is m.

(30) When the grouting anchor bolt 6 is vertically arranged, the slurry diffusion radius R is:

(31) $R=\sqrt{\frac{\mathrm{QT}}{\pi \mathrm{HN}}}$

(32) Where Q is grouting amount per unit time, the unit is m.sup.3/min; T is the grouting duration, the unit is min; N is the porosity of rock stratum, which can be obtained by indoor rock mechanics test; H is the thickness of the rock injected with slurry, the unit is m.

(33) The thickness H of the rock injected with slurry can be determined in FIG. 12 as:
H=L.Math.sin θ

(34) Where L is the length of grouting bolt 6, the unit is m; θ is the inclination of grouting bolt 6 in the surrounding rock, θ=90°−α, and a is the inclination of anchor plate 2, the unit is °.

(35) When the grouting bolt 6 is inclined, the slurry diffusion range S is:
S=R+√{square root over (L.sup.2−H.sup.2)}

(36) The row spacing P of composite beam should meet the following requirements:
P≤2S.Math.cos β,

(37) Where β is the downward inclination of grouting bolt 6 in surrounding rock, the unit is °.

(38) S3.2. The grouting bolt-cable composite beam is arranged according to the row spacing P beyond the advanced abutment pressure zone 13 (initial stress zone 14). In this process, the grouting bolt 6 and grouting cable 7 are pretensioned, but the grouting construction is not carried out (no-grouting zone 141 in FIG. 7), so as to realize the preliminary support and reinforcement of the roadway 8.

(39) S4. Grouting Construction of Shallow Grouting Zone 131

(40) Within the influence range of advance abutment pressure zone 13, the surrounding rock of roadway 8 is gradually damaged from shallow to deep.

(41) According to the detection results of roof fracture zone, the selective grouting construction is carried out to the grouting bolts entering the shallow grouting zone 131, so as to realize the reinforcement of the shallow surrounding rock of roadway.

(42) S5. Grouting Construction of Deep Grouting Zone 132

(43) As the working face continues to advance, grouting construction is carried out for the grouting cable 7 entering the deep grouting zone 132, and the grouting construction is carried out for the grouting bolt 6 entering the shallow grouting zone 131, so as to achieve the progressive reinforcement of the surrounding rock from shallow to deep, from the surface to the inside. The bolt-grouting range 16 and cable-grouting range 17 show in the FIG. 11.

(44) Every time the working face 11 completes a cycle footage, repeat the above S1-S5.

(45) The grouting construction in the above steps should be started in the maintenance team and completed as soon as possible to provide stable surrounding rock environment for the solidification of grouting materials.

(46) In the embodiment of the invention, the inclinations of the four anchor plates 2 are the same, which is intentionally designed for the sake of beauty. In reality, the angles of anchor plates 2 are not necessarily the same. In addition, the grouting bolt-cable composite beam is mainly applicable to the roof conditions with large faults and a large number of rock fragments. In practice, selective grouting can be carried out according to the development degree of cracks in the roof. When the internal cracks of the roof are relatively developed and connected with each other, the number of bolt-grouting is 6-8. When the roof is complete and stable, and there are only a few tiny cracks and joints, the bolt-grouting number is 0-3.

(47) The above is only a detail implementation of the invention, but the protection scope is not limited thereto. Any changes or substitutions without creative work shall be covered within the protection scope of the invention. Therefore, the protection scope of the invention should be limited by the protection scope as defined in the claims.