Double-roadway tunneling narrow coal pillar pressure relief anti-impact supporting method

Abstract

The invention discloses a double-roadway tunneling narrow coal pillar pressure relief and scour prevention supporting method, and relates to the technical field of coal mine narrow coal pillar pressure relief and scour prevention. The method comprises the following steps that firstly, a hole is drilled in the narrow coal pillar, reaming is conducted after the hole is drilled to a certain length, and after reaming is completed, the hole continues to be drilled till the whole narrow coal pillar is drilled through; then, the distance between the drill holes is determined, and multi-row drilling is carried out; then, opposite-pull grouting anchor cables are installed in the drill holes; and lagging for a period of time T, and grouting into the hole through the grouting anchor cable. According to the method, high stress in the narrow coal pillar is released in a drilling and reaming mode, the peak value of a stress concentration area is effectively reduced, elastic energy is released, damage of the elastic energy to the narrow coal pillar is relieved, rock burst is prevented, the surface of the narrow coal pillar is not affected by reaming, and the stability of the narrow coal pillar is high; meanwhile, the bearing capacity of the coal pillar can be improved by installing the grouting anchor cables in the drill holes, further deformation of the roadway is prevented, grouting is conducted after high stress in the coal pillar is released, and the purpose of reinforcing the coal body can be achieved.

Description

Technical Field

[0001] The invention relates to the technical field of pressure relief and anti-bumping of narrow coal pillars in coal mines, and in particular to a pressure relief and anti-bumping supporting method for narrow coal pillars in double-lane excavation. Background Art

[0002] The existence of high stress concentration areas in coal pillars is the fundamental reason for inducing rock burst in coal pillars. High stress concentration causes a large amount of elastic strain energy to accumulate in coal rock mass and brings rock burst danger to the working face. Usually, the method of releasing high stress in coal pillars is used to prevent and control rock burst. The existing pressure relief technical means mainly include cross-tunnel mining to relieve tunnel pressure, tunnel surrounding rock slotting and drilling loosening pressure relief, traditional blasting pressure relief, pressure relief using pressure relief tunnels and pre-mining in advance, etc., among which drilling pressure relief is the most widely used. Drilling pressure relief uses the drilling space to compensate for the volume expansion and deformation of the surrounding rock, thereby maintaining the stability of the tunnel, which can simultaneously relieve pressure and limit the deformation of the surrounding rock. At present, coal mines mostly use large-diameter drilling to relieve pressure and prevent rock burst. However, traditional large-diameter drilling pressure relief, on the one hand, has a large number of drilling holes, limited pressure relief space, and general pressure relief effect; on the other hand, large-diameter drilling further reduces the stability of coal pillars, while the engineering workload is large, the investment is large, and the time consumption is long. In the double-tunnel layout, the narrow coal pillar needs to withstand the impact of two mining operations. During the mining process, the plastic zone of the narrow coal pillar between the double tunnels increases, the stress concentration degree is higher, and the bearing capacity of the coal pillar is reduced, which makes the stability requirements of the coal pillar higher. The traditional large-diameter drilling pressure relief method cannot meet its pressure relief and anti-impact requirements. Summary of the invention

[0003] In view of the above problems, the present invention discloses a method for unloading and anti-bumping support of narrow coal pillars in double tunnels, which adopts the method of large-diameter drilling and hole expansion. On the one hand, the surface of the narrow coal pillar is not affected by the hole expansion, and the coal pillar has high stability; on the other hand, the hole expansion method has a large unloading space and a small number of holes, which saves time. At the same time, the installation of tension grouting anchor cables in the large-diameter drilled holes can effectively improve the bearing capacity of the coal pillar itself and prevent further deformation of the tunnel.

[0004] According to the purpose of the present invention, a method for unloading and anti-bumping support of narrow coal pillars in double tunnel excavation is proposed, comprising the following steps:

[0005] Step 1: Use a drilling and expansion machine to drill a large-diameter hole with a radius of R0 on the narrow coal pillar at a position L0 away from the roadway roof;

[0006] Step 2: When the large-diameter borehole is drilled to a certain length, the blades on both sides of the drill rod are opened to drill an expansion hole with a length of L and a radius of R; after the expansion hole drilling is completed, the blades on both sides are retracted, and the large-diameter borehole is continued to be drilled until the entire narrow coal pillar is drilled through;

[0007] Step 3: Drill multiple rows and columns of large-diameter drill holes according to the spacing D between the large-diameter drill holes;

[0008] Step 4: Install the tension grouting anchor cable in the large diameter borehole, install the tray to the tail of the anchor cable and fix it with a lock to pre-tighten the anchor cable;

[0009] Step 5: After a delay of a period of time T, grouting is injected into the large diameter borehole by pulling the grouting anchor cable;

[0010] Step 6: Repeat steps 1 to 5 until the tunnel excavation is completed.

[0011] Preferably, in step one, the distance L0 between the top large-diameter borehole and the tunnel roof is 1.0-1.2 m, and the radius R0 of the large-diameter borehole is 50-150 mm.

[0012] Preferably, in step 2, the method for determining the length L and radius R of the expanded hole is as follows:

[0013] S21, the energy Q generated by rock burst in narrow coal pillars 冲 Equivalent to the energy Q released by the expansion of the hole with radius R 扩 , then we get the relationship Where: Q 冲 Q is the energy generated by rock burst in narrow coal pillars; 扩 is the energy released by hole expansion; R is the hole expansion radius; L is the hole expansion length; S is the elastic volume expansion coefficient, E is the elastic modulus, v is the Poisson's ratio of the coal pillar; σ1, σ2, σ3 are the three-dimensional stresses of the coal pillar; σ is the stress of the coal pillar; G is the shear elastic modulus, E is the elastic modulus, v is the Poisson's ratio of the coal column; L 破 is the basic breaking step distance, h is the thickness of the basic top rock layer, v is the Poisson's ratio of the coal pillar, σ s is the tensile strength of the basic top rock layer, q is the deadweight of the rock layer and the load on it; D is the spacing between the large-diameter boreholes, k is the risk correction coefficient of the spacing between large-diameter boreholes, which is used to correct the construction risk caused by the excessive or too small spacing between pressure relief boreholes, and is related to the drilling dust removal; the dust removal mass ratio b = w' / w, w' is the actual dust removal mass per unit length of a single large-diameter borehole, w is the calculated dust removal mass per unit length of a single large-diameter borehole, w = ρπd 2 / 4, ρ is the density of the coal seam, d is the diameter of the drill bit for large-diameter drilling construction; for the weak impact danger zone 1.5≤b≤2, k=18.84, for the medium impact danger zone 2<b≤3, k=15.56, for the strong impact danger zone b>3, k=6.28; d is the diameter of the drill bit for large-diameter drilling construction; K is the deformation modulus index, K=λ / E, where λ is the softening modulus after the peak of the stress-strain curve, and E is the elastic modulus;

[0014] S22, the entire process of drilling and reaming is converted by cutting method, and the relationship formula 2 is derived from the equal volume. Where: R is the expansion radius; L is the expansion length; R0 is the radius of the large diameter drilling hole; a is the width of the narrow coal pillar;

[0015] S23, the sum of the large diameter drilling and expansion volume is equivalent to a radius of The borehole volume is derived from the relation Where: R is the expansion radius; L is the expansion length; R0 is the radius of the large diameter drilling hole; a is the width of the coal pillar;

[0016] According to equations 1, 2, and 3, we can solve the hole expansion radius R = 3R0 and the length

[0017] Preferably, in step 2, the drilling and expansion is performed when the drilling length of the large-diameter borehole reaches three-eighths of the width of the narrow coal pillar.

[0018] Preferably, in step 5, the lag time T is determined by:

[0019] The lag time T is equivalent to the time T of releasing rock burst energy when the hole with radius R is expanded. 冲 , the lag time T is related to the change in hole expansion volume, so the lag time Where: V is the initial volume of the hole, V = πR 2 L; R is the hole expansion radius, L is the hole expansion length; V' is the volume after hole expansion deformation. According to the empirical formula, V'=CV, C is 0~1; v 变形 It is the average value of hole expansion deformation velocity.

[0020] Compared with the prior art, the advantages of the double-lane excavation narrow coal pillar pressure relief and anti-bumping support method disclosed in the present invention are:

[0021] (1) The present invention utilizes a large-diameter drilling and hole expansion method to release the high stress in the narrow coal pillar, effectively reduce the peak value of the stress concentration area, release elastic energy, slow down the damage of the narrow coal pillar caused by elastic energy, and prevent the occurrence of impact ground pressure. The surface of the narrow coal pillar is not affected by the hole expansion, and the coal pillar has high stability. At the same time, by installing tension grouting anchor cables in the large-diameter drill hole, the bearing capacity of the coal pillar itself can be improved to prevent further deformation of the tunnel. After the high stress in the coal pillar is released, grouting is performed to achieve the purpose of strengthening the coal body.

[0022] (2) The present invention completes the pressure relief, support and grouting processes in the same borehole, eliminating the need for secondary drilling, reducing resource waste and saving costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the embodiments of the present invention or the technical solutions of the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0024] Figure 1 It is a schematic diagram of the pressure relief and anti-collision support structure disclosed in the present invention.

[0025] Figure 2 This is the layout diagram of the tension grouting anchor cables.

[0026] Figure 3 This is the drilling construction drawing.

[0027] In the figure: 1-pull grouting anchor cable; 2-tray; 3-lock; 4-narrow coal pillar; 5-tunnel; 6-large diameter borehole; 7-hole expansion. DETAILED DESCRIPTION

[0028] The specific implementation of the present invention is briefly described below in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0029] Figure 1-Figure 3 The preferred embodiments of the present invention are shown and analyzed in detail.

[0030] The invention discloses a method for unloading pressure and preventing impact of narrow coal pillars in double tunnel excavation, comprising the following steps:

[0031] Step 1: Use a drilling and expansion machine to drill a large-diameter borehole 6 with a radius R0 at a position L0 from the top of the tunnel 5 on the narrow coal pillar 4. The distance L0 between the top large-diameter borehole 6 and the top of the tunnel 5 is 1.0m, and the radius R0 of the large-diameter borehole 6 is 100mm.

[0032] Step 2: When the drilling length of the large-diameter borehole 6 reaches three-eighths of the width of the narrow coal pillar 4, open the blades on both sides of the drill rod and drill an expansion hole 7 with a length of L and a radius of R; after the drilling of the expansion hole 7 is completed, retract the blades on both sides and continue to drill the large-diameter borehole 6 until the entire narrow coal pillar 4 is drilled through.

[0033] The length L and radius R of the expansion hole 7 are determined as follows:

[0034] S21, the energy Q generated by the rock burst of the narrow coal pillar 4 冲 Equivalent to the energy Q released by the expansion hole 7 with a radius of R 扩, then we get the relationship Where: Q 冲 Q is the energy generated by rock burst in the narrow coal pillar 4; 扩 is the energy released by the expansion hole 7; R is the radius of the expansion hole 7; L is the length of the expansion hole 7; S is the elastic volume expansion coefficient, E is the elastic modulus, v is the Poisson's ratio of the coal pillar; σ1, σ2, σ3 are the three-dimensional stresses of the coal pillar; σ is the stress of the coal pillar; G is the shear elastic modulus, E is the elastic modulus, v is the Poisson's ratio of the coal column; L 破 is the basic breaking step distance, h is the thickness of the basic top rock layer, v is the Poisson's ratio of the coal pillar, σ s is the tensile strength of the basic top rock layer, q is the deadweight of the rock layer and its upper load; D is the spacing of the large-diameter boreholes 6, k is the risk correction coefficient of the spacing of large-diameter boreholes 6, which is used to correct the construction risk caused by the excessive or too small spacing of the pressure relief boreholes, and is related to the drilling dust removal; the dust removal mass ratio b = w' / w, w' is the actual dust removal mass per unit length of a single large-diameter borehole 6, w is the calculated dust removal mass per unit length of a single large-diameter borehole 6, w = ρπd 2 / 4, ρ is the density of the coal seam, d is the diameter of the drill bit for the large-diameter drilling 6 construction; for the weak impact danger zone 1.5≤b≤2, k=18.84, for the medium impact danger zone 2<b≤3, k=15.56, for the strong impact danger zone b>3, k=6.28; d is the diameter of the drill bit for the large-diameter drilling 6 construction; K is the deformation modulus index, K=λ / E, where λ is the softening modulus after the peak of the stress-strain curve, and E is the elastic modulus;

[0035] S22, drilling, reaming 7 The whole process adopts the cutting method to convert, and the relationship formula 2 is derived from the equal volume. Where: R is the radius of the expansion hole 7; L is the length of the expansion hole 7; R0 is the radius of the large diameter drilling hole 6; a is the width of the narrow coal pillar 4;

[0036] S23, the sum of the volumes of the large diameter drilling hole 6 and the expanded hole 7 is equivalent to a radius of The borehole volume is derived from the relation Where: R is the radius of the expansion hole 7; L is the length of the expansion hole 7; R0 is the radius of the large diameter drilling hole 6; a is the width of the narrow coal pillar 4;

[0037] According to equations 1, 2, and 3, we can obtain the radius of the expanded hole 7, R = 3R0, and the length

[0038] Step 3: Drill multiple rows and columns of large diameter holes 6 according to the spacing D between the large diameter holes 6, such as Figure 3 shown.

[0039] Step 4: Install the tension grouting anchor cable 1 in the large diameter borehole 6, install the tray 2 to the tail of the tension grouting anchor cable 1 and fix it with the lock 3, and pre-tighten the anchor cable. Figure 2 The final support structure is shown in Figure 1 shown.

[0040] Step 5: After a delay of a period of time T, grouting is performed into the large diameter borehole 6 by pulling the grouting anchor cable 1. The method for determining the delay time T is:

[0041] The lag time T is equal to the time T of the expansion hole 7 with a radius R to release the rock burst energy. 冲 , the lag time T is related to the volume change of the expanded hole 7, so the lag time Where: V is the initial volume of the expanded hole 7, V = πR 2 L; R is the radius of the expanded hole 7, L is the length of the expanded hole 7; V' is the volume of the expanded hole 7 after deformation, according to the empirical formula, V'=CV, C is 0~1; It is the average value of the deformation speed of hole expansion 7.

[0042] Step 6: Repeat steps 1 to 5 until the excavation of tunnel 5 is completed.

[0043] The above description of the disclosed embodiments enables those skilled in the art to implement and use the present invention. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit and scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest range consistent with the principles and novel features disclosed herein.

Claims

1. A method for unloading pressure and preventing impact of narrow coal pillars in double tunnel excavation, characterized in that: The following steps are involved: Step 1: Drill a large-diameter borehole (6) with a radius of R0 at a position L0 from the roof of the tunnel (5) on the narrow coal pillar (4) using a drilling and expansion machine; Step 2: When the large diameter borehole (6) is drilled to a certain length, the blades on both sides of the drill rod are opened to drill an expansion hole (7) with a length of L and a radius of R; after the expansion hole (7) is drilled, the blades on both sides are retracted, and the large diameter borehole (6) is continued to be drilled until the entire narrow coal pillar (4) is drilled through; Step 3: Drilling multiple rows and columns of large-diameter drill holes (6) according to the spacing D between the large-diameter drill holes (6); Step 4: Install the tension grouting anchor cable (1) in the large diameter borehole (6), install the tray (2) to the tail of the tension grouting anchor cable (1) and fix it with a lock (3) to pre-tighten the anchor cable; Step 5: After a delay of a period of time T, grouting is performed into the large diameter borehole (6) by pulling the grouting anchor cable (1); Step 6: Repeat steps 1 to 5 until the excavation of the tunnel (5) is completed.

2. A method for unloading pressure and preventing impacts in narrow coal pillars for double tunneling according to claim 1, characterized in that: In step 1, the distance L0 between the top large-diameter borehole (6) and the top plate of the tunnel (5) is 1.0-1.2 m, and the radius R0 of the large-diameter borehole (6) is 50-150 mm.

3. A method for unloading pressure and preventing impacts in narrow coal pillars for double tunneling according to claim 1, characterized in that: In step 2, the length L and radius R of the expanded hole (7) are determined as follows: S21. Equivalent the energy Q generated by rock burst in the narrow coal pillar (4) 冲 to the energy Q released by the reaming hole (7) with a radius of R 扩 , and then the relational expression one can be obtained In the formula: Q 冲 is the energy generated by rock burst in the narrow coal pillar (4); Q 扩 is the energy released by the reaming hole (7); R is the radius of the reaming hole (7); L is the length of the reaming hole (7); S is the elastic volume expansion coefficient, E is the elastic modulus, v is the Poisson's ratio of the coal pillar; σ1, σ2, σ3 are the triaxial stresses of the coal pillar; σ is the stress of the coal pillar; G is the shear elastic modulus, E is the elastic modulus, v is the Poisson's ratio of the coal pillar; L 破 is the breaking step distance of the basic roof, h is the thickness of the basic roof rock layer, v is the Poisson's ratio of the coal pillar, σ s is the tensile strength of the basic roof rock layer, q is the self-weight of the rock layer and the load thereon; D is the spacing of the large-diameter boreholes (6), k is the risk correction coefficient for the spacing of the large-diameter boreholes (6), that is, used to correct the construction risk caused by too large or too small spacing of the pressure relief boreholes, and is related to the powder discharge of the boreholes; the powder discharge mass ratio b = w' / w, w' is the actual powder discharge mass per unit length of a single large-diameter borehole (6), w is the calculated powder discharge mass per unit length of a single large-diameter borehole (6), w = ρπd 2 / 4, ρ is the coal seam density, d is the construction bit diameter of the large-diameter borehole (6); for the weak rock burst danger area 1.5 ≤ b ≤ 2, k = 18.84, for the medium rock burst danger area 2 < b ≤ 3, k = 15.56, for the strong rock burst danger area b > 3, k = 6.28; d is the construction bit diameter of the large-diameter borehole (6); K is the deformation modulus index, K = λ / E, where λ is the softening modulus after the peak of the stress-strain curve, and E is the elastic modulus; S22, drilling, reaming (7) The whole process adopts the cutting method to convert, and the relationship formula 2 is derived from the equal volume. Where: R is the radius of the expansion hole (7); L is the length of the expansion hole (7); R0 is the radius of the large diameter drilling hole (6); a is the width of the narrow coal pillar (4); S23, the sum of the volumes of the large diameter drilling hole (6) and the expanded hole (7) is equivalent to a radius of The borehole volume is derived from the relation Where: R is the radius of the expansion hole (7); L is the length of the expansion hole (7); R0 is the radius of the large diameter drilling hole (6); a is the width of the narrow coal pillar (4); According to equations 1, 2, and 3, we can solve the expansion hole (7) to obtain the radius R = 3R0 and the length 4. A method for unloading pressure and preventing impacts in narrow coal pillars for double tunneling according to claim 3, characterized in that: In step 2, when the drilling length of the large diameter borehole (6) reaches three eighths of the width of the narrow coal pillar (4), the borehole is drilled and expanded (7).

5. The method for pressure relief and anti-bumping support of narrow coal pillars in double tunnel excavation according to claim 1 is characterized in that: In step 5, the lag time T is determined by: The lag time T is equal to the time T of releasing rock burst energy by the expansion hole (7) with radius R. 冲 , the lag time T is related to the volume change of the hole expansion (7), so the lag time Where: V is the initial volume of the hole expansion (7), V = πR 2 L; R is the radius of the expanded hole (7), L is the length of the expanded hole (7); V' is the volume of the expanded hole (7) after deformation. According to the empirical formula, V'=CV, C is 0-1; is the average value of the deformation velocity of hole expansion (7).

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