Directional asymmetrical self-adaptive constant-resistance opposite-pulling anchor cable for gob-side entry driving coal pillar and using method of directional asymmetrical self-adaptive constant-resistance opposite-pulling anchor cable

Abstract

The invention relates to a directional asymmetric self-adaptive constant-resistance opposite-pulling anchor cable for a gob-side entry driving coal pillar and a using method, and belongs to the technical field of mining supporting. The anchor cable comprises an anchorage device, a prestress steel strand, a high-pressure telescopic cavity, a low-pressure telescopic cavity, a first spring and a second spring, the first spring is arranged in the low-pressure telescopic cavity, the second spring is arranged in the high-pressure telescopic cavity, and the prestress steel strand is arranged between the first spring and the second spring. Prestressed steel strands extending out of the low-pressure telescopic cavity and the high-pressure telescopic cavity are arranged at the other ends of the first spring and the second spring correspondingly, and anchorage devices are arranged on the outer sides of the prestressed steel strands at the two ends correspondingly. According to the method, effective anchoring of the coal pillar can be achieved, deformation and load changes of surrounding rock can be sensed and adapted through an opposite-pulling mechanical mechanism, and the supporting resistance of the coal pillar can be dynamically adjusted.

Description

Technical Field

[0001] This invention relates to a directional asymmetric adaptive constant resistance tie anchor cable for coal pillars in goaf excavation and its application method, belonging to the field of mining support technology. Background Technology

[0002] As my country's primary energy source, the safe, efficient, and green mining of coal is crucial for achieving the national energy strategy and sustainable development. Pillarless mining technology, a key direction for the scientific development of coal resources and environmental protection in mining areas, mainly includes two forms: leaving roadways along the goaf and excavating roadways along the goaf. This technology significantly reduces the number of coal pillars left in traditional mining by optimizing roadway layout, thereby greatly improving coal extraction rates, reducing roadway excavation work at the source, and effectively alleviating problems such as coal pillar stress concentration and roadway maintenance difficulties, resulting in significant economic and environmental benefits.

[0003] In pillarless mining systems, goaf-side excavation technology involves re-excavating the lower working face along the edge of the collapsed goaf after the upper section of the working face has been mined and the overlying strata have stabilized. Compared to goaf-side roadway retention, goaf-side excavation avoids the intense mining pressure manifestation phase during working face mining, and the stability of the surrounding rock is relatively easier to control. However, the key to the success of goaf-side excavation lies in the stability of the adjacent "narrow coal pillar." This coal pillar, as a crucial structure separating the goaf from the excavated roadway and supporting roof pressure, is subjected to non-uniform stress under the influence of the overlying strata's shifting and transport. Specifically, the stress on the goaf side is significantly higher than that on the roadway's coal face, leading to asymmetrical deformation and failure of the coal pillar. Therefore, effective control of the coal pillar and prevention of overall goaf-side roadway instability caused by its failure is crucial for safe and efficient coal mine production.

[0004] To control the deformation of the surrounding rock in roadways, especially the stability of narrow coal pillars, traditional support methods often employ anchor bolts, anchor cables, and other support structures. However, conventional support designs are ill-suited to the asymmetrical stress characteristics of coal pillars, leading to problems such as asynchronous stress between the support structure and the coal pillar, uncoordinated deformation, and unclear failure mechanisms.

[0005] Chinese patent document CN114909163A discloses a high-strength adaptive large deformation bidirectional tension anti-impact anchor cable, including a bidirectional adaptive device installed in the through hole of the free coal pillar. The bidirectional adaptive device is embedded with two resistance heads, and the ends of the two resistance heads that are far apart from each other are respectively connected to steel strands. The other ends of the two steel strands pass out of the bidirectional adaptive device and are fixed to the two ends of the free coal pillar through a tray and a nut. However, the ultimate goal of roadway support is to ensure that the roadway cross-section always meets the production requirements during use. This anchor cable does not achieve directional control of the deformation of the coal pillar, and it is difficult to control the direction of the deformation of the coal pillar. If the direction of the roadway deformation cannot be controlled, the roadway cross-section may be reduced, affecting the use of the roadway. At the same time, there is no way to control the asymmetric deformation of the coal pillar. Summary of the Invention

[0006] To address the shortcomings of existing technologies, this invention provides a directional asymmetric adaptive constant resistance tension anchor cable for coal pillars in gob-side roadways and its application method. This cable not only effectively anchors the coal pillar itself but also senses and adapts to changes in surrounding rock deformation and load through a tension mechanical mechanism, dynamically adjusting its support resistance. This achieves precise offsetting and transfer of asymmetric loads, ultimately ensuring the long-term stability of narrow coal pillars and roof during gob-side roadway service, fundamentally improving the safety and reliability of narrow coal pillars in gob-side roadways.

[0007] The technical solution of the present invention is as follows:

[0008] An asymmetric adaptive constant resistance tension anchor cable for directional coal pillars in goaf excavation roadways includes an anchor, prestressed steel strands, a high-pressure expansion cavity, a low-pressure expansion cavity, a first spring, and a second spring, wherein:

[0009] A first spring is installed inside the low-pressure telescopic cavity, a second spring is installed inside the high-pressure telescopic cavity, a prestressed steel strand is installed between the first spring and the second spring, and prestressed steel strands extending out of the low-pressure telescopic cavity and the high-pressure telescopic cavity are respectively installed at the other ends of the first spring and the second spring, and anchors are respectively installed on the outer sides of the prestressed steel strands at both ends.

[0010] Anchors are used to maintain the tension of prestressed steel strands and transfer it to the rock strata being reinforced;

[0011] Prestressed steel strands are used to transfer the applied prestress to the rock mass.

[0012] According to a preferred embodiment of the present invention, the spring constant of the first spring is k1, and the spring constant of the second spring is k2, where k2 = 2k1.

[0013] According to a preferred embodiment of the present invention, the low-pressure expansion cavity is disposed in the low-pressure deformation zone of the rock mass, and the high-pressure expansion cavity is disposed in the high-pressure deformation zone of the rock mass.

[0014] The low-pressure expansion cavity is used to enable deformation to occur preferentially in the low-pressure deformation zone than in the high-pressure deformation zone when subjected to stress.

[0015] The high-pressure expansion joint is used to slowly release pressure when the high-pressure deformation zone encounters the high-pressure or low-pressure expansion joint reaching its limit and the threshold of the high-pressure expansion joint, by extending the anchor cable (extending the second spring).

[0016] According to a preferred embodiment of the present invention, an anchor claw is provided on the prestressed steel strand between the first spring and the second spring via an anchor claw sleeve, with the anchor claw facing the high-pressure expansion cavity.

[0017] An anchor claw is an elastic metal structure that extends outwards from the anchor cable like a claw. During the installation of the anchor cable, due to its elastic properties, it will undergo inward compression deformation. When the anchor cable deforms towards the high-pressure expansion cavity, the anchor claw will embed into the coal and rock mass, inhibiting the anchor cable from deforming towards the high-pressure expansion cavity.

[0018] According to a preferred embodiment of the present invention, baffle sleeves are fixedly installed on the prestressed steel strands facing outwards inside the low-pressure telescopic cavity and the high-pressure telescopic cavity, and the baffle sleeves are used to limit the springs (the first spring and the second spring) to avoid excessive deformation.

[0019] According to a preferred embodiment of the present invention, the prestressed steel strand is formed by winding multiple steel wires, including high-strength prestressed steel strand, high-strength prestressed steel wire, and finely rolled threaded steel bars, and the appropriate type of steel strand is selected according to the requirements of the coal mine.

[0020] The above-mentioned method for using directional asymmetric adaptive constant resistance tie-bar anchors for coal pillars in goaf excavation follows these steps:

[0021] (1) Install the anchor cable into the narrow coal pillar in the goaf tunnel;

[0022] (2) The anchor cable is depressurized and deformed.

[0023] According to a preferred embodiment of the present invention, in step (1), when the anchor cable is installed, the low-pressure expansion cavity is used as the head of the anchor cable and it is inserted into the narrow coal pillar along the goaf tunnel. Then, anchors are installed on the prestressed steel strands at both ends for fixation.

[0024] According to a preferred embodiment of the present invention, in step (2), based on the influence of asymmetric load and internal rock structure on the coal pillar, the anchor cable decompression varies depending on the deformation of the coal pillar, specifically:

[0025] ① When the stress F≥F1 and the deformation area is only in the low pressure deformation area, the first spring in the low pressure expansion cavity will deform and elongate, and will only depressurize and deform towards the head of the anchor cable. F is the stress value of the anchor cable, and F1 is the initial threshold for the first spring to deform.

[0026] ② When the stress F≥F2 and the deformation area is only in the high pressure deformation area, the second spring in the high pressure expansion cavity will deform and elongate, and will only decompress and deform towards the tail of the anchor cable. F2 is the initial threshold for the second spring to deform.

[0027] ③ When the stress F≥F2 and the deformation area is only in the low stress deformation area, the elongation of the first spring in the low pressure expansion chamber has reached the limit value. At this time, the second spring in the high pressure expansion chamber begins to elongate and deform, and depressurizes towards the anchor cable head.

[0028] ④ When the stress F≥F1, the deformation area is first in the low-pressure deformation zone, and the first spring stops deforming; then, the stress in the high-pressure deformation zone increases, but is inhibited by the anchor claw, and the stress in the anchor cable continues to increase. When the stress increases to F≥F2, the second spring in the high-pressure deformation zone begins to deform.

[0029] The beneficial effects of this invention are as follows:

[0030] 1. This invention is designed for the asymmetric stress environment of narrow coal pillars in roadways along the goaf, accurately addressing the core challenges of such roadway support: uneven stress on both sides of the coal pillar and complex roof load transmission. Traditional symmetrical support systems are ill-suited to these conditions, while this anchor cable, through a "pull-off" mechanism and segmented telescopic structure, achieves active adaptation and control of asymmetric loads, demonstrating clear engineering relevance and practicality.

[0031] 2. The anchor cable of this invention is internally equipped with a low-pressure expansion cavity and a high-pressure expansion cavity, and uses springs with different elastic coefficients to form a two-stage progressive deformation mechanism:

[0032] In the low-pressure stage: prioritize adapting to smaller deformations and avoid stress concentration caused by premature rigid resistance;

[0033] High-pressure stage: Started when the low-pressure chamber reaches its limit or is directly subjected to high pressure, to achieve slow depressurization and prevent sudden damage.

[0034] 3. This invention constrains the deformation direction of the anchor cable through the anchor claw structure, ensuring that the pressure relief direction is controllable and avoiding support failure due to arbitrary deformation. This directional control mechanism enables the anchor cable to maintain a clear mechanical path under asymmetric load, improving the reliability and durability of the support system. Attached Figure Description

[0035] Figure 1 This is a schematic diagram illustrating the characteristics of the collapse of the overlying strata in the mining area;

[0036] Figure 2 This is a diagram showing the non-uniform load distribution on a coal pillar;

[0037] Figure 3 This is a schematic diagram of the asymmetric deformation of a coal pillar after being subjected to a non-uniform load.

[0038] Figure 4 This describes the arrangement of the invention within the coal pillar;

[0039] Figure 5 This is a side view of the present invention;

[0040] Figure 6 This is a front view of the present invention;

[0041] Figure 7 This is the anchor cable of the present invention that has not undergone deformation;

[0042] Figure 8 This is the anchor cable depressurization condition ① of the present invention;

[0043] Figure 9 This is the anchor cable depressurization condition ② of the present invention;

[0044] Figure 10 This is the anchor cable depressurization condition ③ of the present invention;

[0045] Figure 11 This refers to the anchor cable depressurization condition ④ of the present invention.

[0046] In the diagram: 1-overlying strata, 2-A key block, 3-break line, 4-B key block, 5-C key block, 6-basic roof, 7-working face, 8-roadway, 9-narrow coal pillar, 10-goaf, 11-anchor, 12-prestressed steel strand, 13-high-pressure expansion cavity, 14-second spring, 15-anchor claw, 16-low-pressure expansion cavity, 17-first spring, 18-steel strand slot, 19-high-pressure deformation zone, 20-low-pressure deformation zone, 21-anchor claw sleeve, 22-stop block sleeve. Detailed Implementation

[0047] The present invention will be further described below with reference to the embodiments and accompanying drawings, but is not limited thereto.

[0048] Example 1:

[0049] like Figure 4-7 As shown, this embodiment provides an asymmetric adaptive constant resistance tension anchor cable for directional coal pillars in goaf excavation, including an anchor 11, prestressed steel strands 12, a high-pressure expansion cavity 13, a low-pressure expansion cavity 16, a first spring 17, and a second spring 14, wherein:

[0050] A first spring 17 is installed inside the low-pressure telescopic cavity 16, and a second spring 14 is installed inside the high-pressure telescopic cavity 13. A prestressed steel strand 12 is installed between the first spring 17 and the second spring 14. The other ends of the first spring 17 and the second spring 14 are respectively provided with prestressed steel strands extending out of the low-pressure telescopic cavity and the high-pressure telescopic cavity. Anchors 11 are respectively installed on the outer side of the prestressed steel strands at both ends.

[0051] Anchor 11 is used to maintain the tension of the prestressed steel strand and transfer it to the reinforced rock layer. The anchor is an existing structure, composed of three parts: an anchor ring, an anchor wedge, and a wire ring. The anchor ring has a cylindrical design with a conical inner hole. The wedge has threaded teeth on its inner surface and a conical outer surface. The conical surface of the anchor ring's inner hole should mate with the outer surface of the wedge. When installation and tensioning are completed, the wedge follows the spirally wound steel strand, wedging itself between the steel strand and the anchor ring to complete the anchor cable anchoring.

[0052] The prestressed steel strand 12 is used to transfer the applied prestress to the rock mass.

[0053] The spring constant of the first spring 17 is k1, and the spring constant of the second spring 14 is k2, where k2 = 2k1.

[0054] The low-pressure expansion cavity 16 is located in the low-pressure deformation zone of the rock mass, and the high-pressure expansion cavity 13 is located in the high-pressure deformation zone of the rock mass.

[0055] The low-pressure expansion cavity 16 is used to enable deformation to occur preferentially in the low-pressure deformation zone than in the high-pressure deformation zone when subjected to stress.

[0056] The high-pressure expansion chamber 13 is used to slowly release pressure when the high-pressure deformation zone encounters the high-pressure or low-pressure expansion chamber reaching its limit and the threshold of the high-pressure expansion chamber, by extending the anchor cable (extending the second spring).

[0057] An anchor claw 15 is provided on the prestressed steel strand between the first spring 17 and the second spring 14 through the anchor claw sleeve 21, with the anchor claw 15 facing the high-pressure expansion cavity 13.

[0058] Anchor claw 15 is an elastic metal structure that extends outward from the anchor cable like a claw. During the installation of the anchor cable, due to its elastic properties, it will undergo inward compression deformation. When the anchor cable deforms towards the high-pressure expansion cavity, the anchor claw 15 will embed into the coal and rock mass, inhibiting the anchor cable from deforming towards the high-pressure expansion cavity.

[0059] Baffle sleeves 22 are fixedly installed on the prestressed steel strands facing outward inside the low-pressure telescopic cavity 16 and the high-pressure telescopic cavity 13. The baffle sleeves limit the springs (first spring and second spring) to prevent excessive deformation.

[0060] The prestressed steel strand 12 is formed by winding multiple steel wires. The types include high-strength prestressed steel strand, high-strength prestressed steel wire and fine-rolled threaded steel bar. The appropriate type of steel strand is selected according to the requirements of the coal mine.

[0061] Characteristics of overlying strata collapse in the mining area, such as Figure 1 As shown, the overlying rock layer 1, which is the collective name of all rock layers above the basic top 6, is the "load source" that transmits its own weight and tectonic stress and generates loading on the lower structure.

[0062] Key Block 2 is located behind the working face, adjacent to the break line, with the working face below it. It is supported by a support frame, but it may still rotate, affecting the mining pressure manifestation of the working face.

[0063] Break line 3 is the trajectory of a through crack generated in the key block under the combined action of tension and shear, marking the transformation of the rock strata from a continuous beam state to a masonry beam structure; the location of the break line determines the hinge point of the block and the load transfer path.

[0064] Key block B4, located between key blocks A and C, plays a role in transferring loads and coordinating deformation. Below it is the boundary area between the coal pillar and the goaf, which may be supported by gangue and generate shear force with key block A.

[0065] C key block 5 is located in the rock strata above the goaf, supported by gangue, and forms a hinged structure with B key block.

[0066] The basic roof 6 is a rock stratum located directly above the coal seam, with low strength and a relatively small layer thickness. It collapses as the goaf is mined out, serving as the "first barrier" for roof management. Its collapse and fragmentation properties determine the degree of filling and air leakage in the goaf.

[0067] Working face 7 is the working space consisting of the coal mining machine, supports and conveyors. It is the core area for coal mining, immediate roof support and dynamic balance control of the surrounding rock.

[0068] Roadway 8 is a passageway excavated for transportation, ventilation, and pedestrian access in the working face. It is affected by the combined pressure of mining-driven support and lateral support, and its stability needs to be maintained through coal pillar size, support type, and pressure relief measures.

[0069] Narrow coal pillars (9) are coal bodies left between roadways or at the edge of goaf areas to support overlying strata, isolate goaf areas from roadways, and control surface subsidence. Their width directly determines whether the coal pillar itself enters plastic failure and the long-term stability of the roadway.

[0070] Goaf 10 is the void area formed after coal mining. As the basic roof and overlying strata collapse, break up, and compact, the goaf becomes the "accepting space" for the final settlement of the overlying strata. Its collapse-compaction process determines the amount of surface subsidence and the periodic compaction intensity of the working face.

[0071] The above-mentioned method for using directional asymmetric adaptive constant resistance tie-bar anchors for coal pillars in goaf excavation follows these steps:

[0072] (1) Install the anchor cable into the narrow coal pillar of the gob-side excavation roadway. When installing the anchor cable, use the low-pressure expansion cavity as the anchor cable head to extend into the narrow coal pillar of the gob-side excavation roadway, and then install anchors on the prestressed steel strands at both ends for fixation.

[0073] (2) The anchor cable undergoes stress relief deformation. Based on the influence of asymmetric load and internal rock structure on the coal pillar, the stress relief of the anchor cable varies depending on the deformation of the coal pillar. Specifically:

[0074] ① When the stress F ≥ F1, and the deformation area is only in the low-pressure deformation zone, the anchor cable will undergo the following... Figure 8 As shown in the figure, the first spring in the low-pressure telescopic cavity deforms and elongates, and will only depressurize and deform towards the head of the anchor cable. F is the stress value of the anchor cable, and F1 is the initial threshold for the deformation of the first spring.

[0075] ② When the stress F ≥ F2, and the deformation area is only in the high-pressure deformation zone, the anchor cable will undergo the following... Figure 9 As shown in the deformation diagram, the second spring inside the high-pressure telescopic cavity will deform and elongate, and will only depressurize and deform towards the tail of the anchor cable. F2 is the initial threshold for the deformation of the second spring.

[0076] ③ When the stress F ≥ F2, and the deformation area is only in the low-stress deformation zone, the anchor cable will undergo the following... Figure 10 As shown in the deformation, the first spring in the low-pressure telescopic cavity has reached its limit. At this time, the second spring in the high-pressure telescopic cavity begins to extend and deform, decompressing and deforming towards the anchor cable head.

[0077] ④ When the stress F ≥ F1, the deformation area is initially in the low-pressure deformation zone, and the first spring stops deforming. Then, the stress in the high-pressure deformation zone increases, but is inhibited by the anchor claws, causing the stress in the anchor cable to continuously increase. When the stress increases to F ≥ F2, the second spring in the high-pressure deformation zone begins to deform. Similarly, the principle of the deformation area first being the high-pressure deformation zone and then the low-pressure deformation zone is the same. Figure 11 As shown.

Claims

1. A type of directional asymmetric adaptive constant resistance tie-bar anchor cable for coal pillars in goaf excavation, characterized in that, Includes anchorage, prestressed steel strand, high-pressure expansion joint, low-pressure expansion joint, first spring and second spring, wherein: A first spring is installed inside the low-pressure telescopic cavity, a second spring is installed inside the high-pressure telescopic cavity, a prestressed steel strand is installed between the first spring and the second spring, and prestressed steel strands extending out of the low-pressure telescopic cavity and the high-pressure telescopic cavity are respectively installed at the other ends of the first spring and the second spring, and anchors are respectively installed on the outer sides of the prestressed steel strands at both ends. Anchors are used to maintain the tension of prestressed steel strands and transfer it to the rock strata being reinforced; Prestressed steel strands are used to transfer the applied prestress to the rock mass.

2. The asymmetric adaptive constant resistance tie-bar anchor cable for directional coal pillar directional excavation along the goaf as described in claim 1, characterized in that, The spring constant of the first spring is k1, and the spring constant of the second spring is k2, where k2 = 2k1.

3. The asymmetric adaptive constant resistance tie-bar anchor cable for directional coal pillar burial in goaf excavation as described in claim 2, characterized in that, The low-pressure expansion cavity is set in the low-pressure deformation zone of the rock mass, and the high-pressure expansion cavity is set in the high-pressure deformation zone of the rock mass. The low-pressure expansion cavity is used to enable deformation to occur preferentially in the low-pressure deformation zone than in the high-pressure deformation zone when subjected to stress. The high-pressure expansion joint is used to slowly release pressure when the anchor cable elongates in a high-pressure deformation zone, or when the high-pressure or low-pressure expansion joint reaches its limit and the threshold of the high-pressure expansion joint.

4. The asymmetric adaptive constant resistance tie-bar anchor cable for directional coal pillar burial in roadway excavation as described in claim 3, characterized in that, An anchor claw is installed on the prestressed steel strand between the first spring and the second spring, with the anchor claw facing the high-pressure expansion cavity.

5. The asymmetric adaptive constant resistance tie-bar anchor cable for directional coal pillar burial in goaf excavation as described in claim 4, characterized in that, Baffle sleeves are fixedly installed on the prestressed steel strands facing outward inside the low-pressure expansion cavity and the high-pressure expansion cavity.

6. The asymmetric adaptive constant resistance tie-bar anchor cable for directional coal pillar burial along goaf excavation as described in claim 5, characterized in that, Prestressed steel strands are formed by winding multiple steel wires, and the types include high-strength prestressed steel strands, high-strength prestressed steel wires, and precision-rolled threaded steel bars.

7. The method of using the directional asymmetric adaptive constant resistance tie-bar anchor cable for coal pillars in goaf excavation as described in claim 5, characterized in that, The steps are as follows: (1) Install the anchor cable into the narrow coal pillar in the goaf tunnel; (2) The anchor cable is depressurized and deformed.

8. The method of using the directional asymmetric adaptive constant resistance tie-bar anchor cable for coal pillars in goaf excavation as described in claim 7, characterized in that, In step (1), when the anchor cable is installed, the low-pressure expansion cavity is used as the head of the anchor cable to extend into the narrow coal pillar along the goaf roadway, and then the anchor is installed on the prestressed steel strands at both ends for fixation.

9. The method of using the directional asymmetric adaptive constant resistance tie-bar anchor cable for coal pillars in goaf excavation as described in claim 8, characterized in that, In step (2), based on the influence of asymmetric loads and the internal structure of the rock on the coal pillar, the stress relief of the anchor cable varies depending on the deformation of the coal pillar. Specifically: ① When the stress F≥F1 and the deformation area is only in the low pressure deformation area, the first spring in the low pressure expansion cavity will deform and elongate, and will only depressurize and deform towards the head of the anchor cable. F is the stress value of the anchor cable, and F1 is the initial threshold for the first spring to deform. ② When the stress F≥F2 and the deformation area is only in the high pressure deformation area, the second spring in the high pressure expansion cavity will deform and elongate, and will only decompress and deform towards the tail of the anchor cable. F2 is the initial threshold for the second spring to deform. ③ When the stress F≥F2 and the deformation area is only in the low stress deformation area, the elongation of the first spring in the low pressure expansion chamber has reached the limit value. At this time, the second spring in the high pressure expansion chamber begins to elongate and deform, and depressurizes towards the anchor cable head. ④ When the stress F≥F1, the deformation area is first in the low-pressure deformation zone, and the first spring stops deforming; then, the stress in the high-pressure deformation zone increases, but is inhibited by the anchor claw, and the stress in the anchor cable continues to increase. When the stress increases to F≥F2, the second spring in the high-pressure deformation zone begins to deform.

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