Method for controlling coal-rock interfacial effect of anchor net support roof of soft coal seam in sliding tectonic area

Abstract

The invention discloses a sliding tectonic area soft coal seam anchor net support roof coal rock interfacial effect control method, which comprises the following steps of: according to geological mining conditions of a roadway, firstly determining anchor net support parameters and a support system of the roadway according to an anchor net support parameter determination method of a general roadway; then according to the change of the top coal thickness, the anchor rod length and the anchor cable length with preliminarily determined parameters are adjusted, the anchor rod and anchor cable arrangement mode of the preliminarily determined supporting system is adjusted, and the specific adjustment principle for the anchor rod length and the anchor cable length is designed as follows: the distance between the inner anchoring heads of the adjusted anchor rod and anchor cable and the coal rock interface is larger than 1.0 m; therefore, the anchoring performance of the anchor rod cable is brought into full play, the interfacial effect on the roof coal-rock interface is avoided, separation on the roof coal-rock interface and overall sinking of the roof are effectively controlled, the serious accident of overall collapse of the roof is prevented, and the safety of the roof is guaranteed.

Description

Technical Field

[0001] The invention relates to the technical field of mine pressure and rock layer control, in particular to a method for controlling coal-rock interface effect of an anchor mesh supporting roof of a soft coal seam in a sliding structure area. Background Art

[0002] Affected by the sliding geological structure, the bolt support technology for coal roadways in extremely soft and thick coal seams has many technical difficulties: strong rheology of the coal body, high anchor loss rate of the anchor cable, large changes in the surrounding rock conditions of the roadway, and great construction difficulty. Among them, the coal roadways in extremely soft and thick coal seams are prone to interface effects such as delamination at the interface between the roof and coal and rock, such as Figure 1 As shown, Figure 1 The maximum principal stress distribution curve of the tunnel roof surrounding rock under different internal friction angles (structural surfaces) shows the maximum principal stress distribution law of the tunnel roof surrounding rock along the depth direction in the extremely soft coal tunnel in the sliding structure area. From the distribution of the maximum principal stress of the tunnel roof surrounding rock, near the coal-rock interface of the tunnel roof, when the top coal transitions to the rock layer, the maximum principal stress of the tunnel roof surrounding rock first decreases greatly, and then suddenly increases more. This is the interface effect at the coal-rock interface. This stress drops sharply, causing the gripping force of the anchor rod or anchor cable to decrease, thereby causing the anchoring force of the anchor rod or anchor cable to decrease. In this way, it is difficult for the shallow coal body to form a stable anchor net support bearing structure, resulting in delamination at the coal-rock interface below the rock layer. Therefore, during the anchor net support process, once the inner anchor head of the anchor rod or anchor cable is anchored near the coal-rock interface, this interface effect is very likely to occur at the coal-rock interface. At this time, the roof will sink as a whole, and even cause a large area of ​​roof collapse, resulting in a serious roof accident.

[0003] Although there are many existing anchor support theories, these theories do not take into account the characteristics of the loose and rheological characteristics of the broken coal in the sliding structure area, nor do they take into account the actual bearing condition of the anchor cable during the deformation and destruction of the loose and broken coal body. The synergistic mechanism of the anchor cable is not clear, resulting in blindness in the arrangement of the anchor cable. In addition, the existing anchor net support technology emphasizes high-strength prestressing, but there are few previous studies on how to form a stable anchor net support bearing structure under the conditions of the loose and rheological conditions of the coal body under the influence of sliding geological structures. Therefore, there is insufficient understanding of the interface effect of the coal-rock interface of the roof of the coal roadway with anchor net support in extremely soft and thick coal seams. As a result, during the anchor net support process, the anchor net support technical parameters cannot be adjusted in time according to the changes in the thickness of the top coal of the coal roadway in extremely soft and thick coal seams. It is difficult to avoid the interface effect generated when the inner anchor head of the anchor rod or anchor cable is anchored near the interface of the roof coal rock, and thus the delamination at the coal-rock interface or the overall sinking of the roof cannot be effectively controlled. Summary of the invention

[0004] The purpose of the present invention is to provide a method for controlling the coal-rock interface effect of the anchor mesh supporting roof in a soft coal seam in a sliding structure area, which can effectively control the delamination or overall sinking of the roof at the roof coal-rock interface, thereby ensuring the safety of the roof.

[0005] The technical solution of the present invention is:

[0006] A method for controlling coal-rock interface effect of anchor mesh support roof in soft coal seams in sliding structural areas, comprising the following steps:

[0007] S1 Determine the anchor net support parameters and support system of the tunnel according to the geological mining conditions of the tunnel;

[0008] S2 According to the change of the top coal thickness, the anchor rod length and the anchor cable length of the anchor net support parameters are adjusted, and the anchor rod and anchor cable arrangement mode of the anchor net support system is adjusted according to the change of the top coal thickness; the adjustment principle of the anchor rod length and the anchor cable length is: the distance between the inner anchor head of the adjusted anchor rod and anchor cable and the coal-rock interface is greater than 1.0m; the principle of adjusting the anchor rod and anchor cable arrangement mode under different top coal thickness conditions is: when the local top coal is broken and the pressure exceeds the set pressure value during construction, one of the measures of increasing the anchor cable installation density or reducing the spacing between anchor rods is adopted to improve the support strength;

[0009] Furthermore, the specific method for adjusting the length of the anchor rod and the length of the anchor cable includes:

[0010] S21 When the top coal thickness differs from the determined anchor length within 0.5 m, a short anchor cable is used to replace the anchor with preliminarily determined parameters, and the distance between the inner anchor head of the short anchor cable and the coal-rock interface is greater than 1.0 m;

[0011] S22 When the top coal thickness is greater than L1, L1 = anchor length + 1.0m, and the difference with the anchor length of the initially determined parameters is within 0.5m, the anchor with the confirmed parameters is replaced by a short anchor, the length of the short anchor is 4.0m to 5.0m, wherein the calculation formula of the anchor length of the initially determined parameters is: L = 4.5 + 0.98x - 0.06x 2 , where x is the top coal thickness;

[0012] S23 When the top coal thickness is greater than L2, L2 = anchor cable length + 1.0m, the anchor cable length is determined according to the anchor cable length with the preliminary determined parameters.

[0013] Furthermore, the anchor mesh support system includes: anchor mesh cable, steel ladder beam, double-layer mesh and anchor cable combined support; or the top adopts steel mesh, hard plastic mesh, H-shaped steel belt and anchor cable combined support, and the side adopts steel mesh, hard plastic mesh, H-shaped steel belt and anchor rod combined support.

[0014] Furthermore, the double-layer mesh includes: a metal diamond mesh and a black double-resistance mesh; and the H-shaped steel belt is a transverse steel belt.

[0015] Compared with the prior art, the present invention has the following beneficial effects:

[0016] Since delamination is prone to occur at the coal-rock interface and the anchorability is low, the anchoring performance of the anchor cable will be weakened. According to the interface effect of the coal-rock interface at the roof of the extremely soft coal roadway and the change in the thickness of the top coal, the present invention timely adjusts the length of the anchor rod or anchor cable to make the distance between the inner anchoring head of the anchor rod and anchor cable and the coal-rock interface greater than 1.0m, so as to give full play to the anchoring performance of the anchor rod cable and avoid the interface effect at the coal-rock interface of the roof, so as to effectively control the delamination at the coal-rock interface of the roof and the overall sinking of the roof, prevent the overall collapse of the roof and other serious accidents, and ensure the safety of the roof. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 This is a schematic diagram of the maximum principal stress distribution law along the depth direction of the roof surrounding rock of extremely soft coal roadway in the sliding structure area.

[0018] Figure 2 It is a schematic diagram of the anchor cable length variation principle of the present invention.

[0019] Figure 3 The maximum principal stress distribution curve of the surrounding rock of the tunnel roof at different top coal thicknesses after the interface effect of the anchor mesh supporting the roof coal-rock interface of the extremely soft and thick coal seam is eliminated in the present invention.

[0020] Figure 4 This is a geological profile of the upper and lower drifts on the working face of an application example of the present invention.

[0021] Figure 5 This is a plan view of the layout of top plate anchor rods and anchor cables in an application example of the present invention.

[0022] Figure 6 for Figure 5 Cross-section diagram of anchor net support at middle section II.

[0023] Figure 7 for Figure 5 Cross-section diagram of anchor net support at section II-II.

[0024] Figure 8 This is a real picture of the anchor beam mesh support effect of the application example of the present invention. DETAILED DESCRIPTION

[0025] Combine the following Figures 1 to 8, the specific embodiments of the present invention are described in detail. In the description of the present invention, it should be understood that the terms "center", "upper", "lower", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention.

[0026] The terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features; in the description of the present invention, unless otherwise specified, "plurality" means two or more.

[0027] According to the results of theoretical analysis, under the same mechanical parameters of coal and rock mass, as the thickness of the top coal increases, the self-stabilizing capacity of the roadway roof decreases sharply, and the difficulty of controlling the roof surrounding rock increases. However, when the bearing structure formed by the anchor in the shallow surrounding rock is relatively stable, the sinking of the top coal and the immediate roof will decrease, and the anchor net support is mainly borne by the deformation pressure of the shallow coal body itself. In addition, from the distribution of the maximum principal stress of the roadway surrounding rock, when the thickness of the top coal is thick, there is always an area in the coal body below the immediate roof. Although the maximum principal stress of the surrounding rock in this area is slowly decreasing, the overall stress level of the surrounding rock in this area is relatively high.

[0028] According to theoretical analysis and the successful experience of anchor mesh support in a large number of engineering practices, different anchor mesh support technical solutions should be adopted according to the changes in the thickness of the top coal in the extremely soft and thick coal seam.

[0029] Example

[0030] A method for controlling coal-rock interface effect of anchor mesh support roof in soft coal seams in sliding structural areas, comprising the following steps:

[0031] S1 According to the geological mining conditions of the tunnel, the anchor net support parameters and support system of the tunnel are preliminarily determined according to the anchor net support parameter determination method of the general tunnel;

[0032] S2 adjusts the anchor rod length and anchor cable length of the anchor net support parameters preliminarily determined according to the change of top coal thickness, and adjusts the anchor rod and anchor cable arrangement mode of the anchor net support system preliminarily determined according to the change of top coal thickness; the adjustment principle of the anchor rod length and the anchor cable length is: the distance between the inner anchoring head of the adjusted anchor rod and anchor cable and the coal-rock interface is greater than 1.0m; the principle of adjusting the anchor rod and anchor cable arrangement mode under different top coal thickness conditions is: when the local top coal is broken and the pressure exceeds the set pressure value during construction, take one of the measures of increasing the anchor cable installation density or reducing the spacing between anchor rods to improve the support strength.

[0033] like Figure 2 As shown, when the top coal thickness is 3m, the anchor cable length is 4m; when the top coal thickness is 5m, the anchor cable length is 6.2m; when the top coal thickness is 7m, the anchor cable length is 8.2m; the adjustment of the above anchor cable lengths is based on the adjustment principle that the distance between the inner anchoring head of the anchor cable and the coal rock section is greater than 1.0m. It is worth noting that when the top coal thickness is greater than 7m, for example 10 meters, an 8.2m anchor cable can also be used, but it is necessary to ensure that the distance between the inner anchoring head of the anchor cable and the coal rock section is greater than 1.0m.

[0034] The specific adjustment method for the anchor rod length and the anchor cable length includes:

[0035] S21 When the top coal thickness differs from the determined anchor length within 0.5 m, a short anchor cable is used to replace the anchor with preliminarily determined parameters, and the distance between the inner anchor head of the short anchor cable and the coal-rock interface is greater than 1.0 m;

[0036] S22 When the top coal thickness is greater than L1, L1 = anchor length + 1.0m, and the difference with the anchor length of the initially determined parameters is within 0.5m, the anchor with the confirmed parameters is replaced by a short anchor, the length of the short anchor is 4.0m to 5.0m, wherein the calculation formula of the anchor length of the initially determined parameters is: L = 4.5 + 0.98x - 0.06x 2 , where x is the thickness of the top coal. The calculated anchor cable length by the above calculation formula is such that the distance between the anchor head and the coal-rock interface is always greater than 1.0 m, which can give full play to the anchoring performance and control the stability of the roof;

[0037] S23 When the top coal thickness is greater than L2, L2 = anchor cable length + 1.0m, the anchor cable length is determined according to the anchor cable length with the preliminary determined parameters.

[0038] In some embodiments, the anchor mesh support system includes: anchor mesh cables, steel ladder beams, double-layer mesh and anchor cable combined support; or the top uses steel mesh, hard plastic mesh, H-shaped steel belt and anchor cable combined support, and the side uses steel mesh, hard plastic mesh, H-shaped steel belt and anchor rod combined support.

[0039] The double-layer mesh includes: a metal diamond mesh and a black double-resistance mesh; the H-shaped steel belt is a transverse steel belt.

[0040] In some embodiments, the anchor cables of the anchor net support of a general roadway are arranged in a five-point arrangement, such as "2-3-2" and "3-4-3", so that the anchor cables of different sections are structurally complementary. Here, "3" means that 3 anchor cables are arranged in the support section, "2" means that 2 anchor cables are arranged in the support section, and so on.

[0041] Application Examples

[0042] Case study of anchor net support in upper tunnel of XX mine

[0043] like Figure 4 As shown, the coal seams in the working face of XX Mine are extremely unstable. Judging from the thickness of the coal seams exposed in the upper and lower drifts of the working face, the minimum thickness of the coal seams in the upper and lower drifts is only 0.7m, and the maximum reaches 10.6m.

[0044] The upper auxiliary tunnel of XX Mine is designed as a rectangular cross section, with a net width × net height = 4.8 × 3.0m, and a net cross section of 14.4m 2 .

[0045] According to the theory of natural balanced arch, the tunnel is supported by anchor cable + steel ladder beam + double-layer mesh (metal diamond mesh and black double-resistance mesh) + anchor cable. The specific support scheme is as follows: Figure 5 , Figure 6 as well as Figure 7 shown.

[0046] During the excavation process, when the coal thickness is less than 5m, the top excavation is carried out, and when the coal thickness is greater than 5m, the bottom excavation is carried out. When excavating from the top and the bottom, the anchor rods, steel ladder beams, and the top mesh support parameters are the same, but the anchor cable arrangement method and anchor cable length are different. When the top coal thickness in the coal seam is 1 to 5m, the anchor cable length is 6.2 to 7.2m, and the anchor cables are arranged in a "3-2-3" manner, with an anchor cable spacing of 0.8m, that is, they are arranged in a row of 3 and 2 in a row; when the top coal thickness is greater than 5m, the anchor cable length is 8.2 to 9.2m, and the roof anchor cables are arranged in a "3-2-3" manner, with an anchor cable spacing of 0.8m. A 4.25m long side anchor cable is added to the upper half of the two sides for reinforcement support, and the side anchor cable spacing is 1.6m.

[0047] The effect of using anchor beam mesh support in this application example is as follows Figure 8 shown.

[0048] After applying the above-mentioned anchor mesh support technology, the delamination of the coal-rock interface of the roof and the overall sinking of the roof were effectively controlled, ensuring the stability of the tunnel roof and reducing the tunnel support cost.

[0049] Specific as Figure 3As shown in the figure, the maximum principal stress distribution curve in the depth direction of the tunnel roof surrounding rock is obtained after the method of controlling the coal-rock interface effect of the extremely soft and thick coal seam anchor mesh support roof is adopted for different top coal thicknesses. Figure 3 It can be seen that when the thickness of the top coal is 1.5m, the maximum principal stress distribution of the surrounding rock in the shallow range of 0 to 1.25m of the anchor mesh supported roadway is approximately horizontal, and the average maximum principal stress is about 1.18MPa. Under this condition, the maximum principal stress fluctuation mainly occurs in the direct roof range. When the thickness of the top coal increases to 6.5m, the stress distribution morphology of the surrounding rock in the shallow part of the roadway changes greatly, and the maximum principal stress of the surrounding rock in the shallow range of 0 to 3.75m of the roadway presents an approximately linear fluctuation increase state. After that, with the increase in depth, the maximum principal stress in the top coal begins to slowly decrease from a basically stable state. When the top coal thickness is 11.5m, the stress distribution morphology is basically similar to it, but the stress level in the shallow stress fluctuation zone is significantly lower than that.

[0050] The maximum principal stress distribution curve of the tunnel roof surrounding rock at different top coal thicknesses shows that there is no sharp drop in the maximum principal stress at the coal-rock interface. This shows that the control method of this embodiment has eliminated the coal-rock interface effect of the anchor mesh support roof in extremely soft and thick coal seams.

[0051] Field measurement results show that after adopting the control method of this embodiment, the delamination at the coal-rock interface of the coal roadway roof in the extremely soft and thick coal seam disappears, and no obvious delamination occurs at the coal-rock interface of the coal roadway roof in the extremely soft and thick coal seam.

[0052] In addition, the overall sinking of the coal roadway roof in extremely soft and thick coal seams has been effectively controlled, avoiding serious accidents such as sudden collapse of the roof.

[0053] The above disclosures are only several preferred specific embodiments of the present invention. However, the embodiments of the present invention are not limited thereto. Any changes that can be conceived by those skilled in the art should fall within the protection scope of the present invention.

Claims

1. A method for controlling the coal-rock interface effect of the anchor mesh supporting roof of a soft coal seam in a sliding structural area, characterized in that: The following steps are involved: S1 Preliminarily determine the anchor net support parameters and support system of the tunnel according to the geological mining conditions of the tunnel; S2 adjusts the anchor rod length and anchor cable length of the preliminarily determined anchor net support parameters according to the change of top coal thickness, and adjusts the anchor rod and anchor cable arrangement mode of the preliminarily determined anchor net support system according to the change of top coal thickness; the adjustment principle for the preliminarily determined anchor rod length and anchor cable length is: the distance between the inner anchoring head of the adjusted anchor rod and anchor cable and the coal-rock interface is greater than 1.0m; the principle for adjusting the anchor rod and anchor cable arrangement mode under different top coal thickness conditions is: when the local top coal is broken and the pressure exceeds the set pressure value during construction, take one of the measures of increasing the anchor cable installation density or reducing the spacing between anchor rods to improve the support strength.

2. The method for controlling the coal-rock interface effect of the anchor mesh supporting roof in a soft coal seam in a sliding structural area according to claim 1 is characterized in that: The specific adjustment method for the initially determined anchor rod length and anchor cable length includes: S21 When the top coal thickness differs from the preliminarily determined anchor rod length within 0.5 m, a short anchor cable is used to replace the preliminarily determined anchor rod, and the distance between the inner anchor head of the short anchor cable and the coal-rock interface is greater than 1.0 m; S22 When the top coal thickness is greater than L1, L1 = anchor length + 1.0m, and the difference with the anchor length of the initially determined parameters is within 0.5m, the anchor with the confirmed parameters is replaced by a short anchor, the length of the short anchor is 4.0m to 5.0m, wherein the calculation formula of the anchor length of the initially determined parameters is: L = 4.5 + 0.98x - 0.06x 2 , where x is the top coal thickness; S23 When the top coal thickness is greater than L2, L2 = anchor cable length + 1.0m, the anchor cable length is determined according to the anchor cable length with the preliminary determined parameters.

3. The method for controlling the coal-rock interface effect of the anchor mesh supporting roof in a soft coal seam in a sliding structural area according to claim 1, characterized in that: The anchor net support system includes: Combined support of anchor net cables, steel ladder beams, double-layer nets and anchor cables; Or the top is supported by a combination of steel mesh, hard plastic mesh, H-shaped steel belt and anchor cables, and the side is supported by a combination of steel mesh, hard plastic mesh, H-shaped steel belt and anchor rods.

4. The method for controlling the coal-rock interface effect of the anchor mesh supporting roof in a soft coal seam in a sliding structure area according to claim 3 is characterized in that: The double-layer mesh includes: a metal diamond mesh and a black double-resistance mesh; the H-shaped steel belt is a transverse steel belt.

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