Wall column type gob-side entry retaining surrounding rock stress control method

Abstract

The invention relates to the technical field of roadway support, in particular to a wall column type gob-side entry retaining surrounding rock stress control method, which comprises the following steps of: acquiring the layer number and the layer position of overlying strata above a gob-side entry retaining top plate, and judging the layer number and the layer position of key strata for controlling the movement of the strata above the gob-side entry retaining top plate; and key rock strata which are located above the gob-side entry retaining top plate and used for controlling rock strata movement are subjected to fracturing weakening, and the fracturing weakening positions are located above the working faces on the two sides of the gob-side entry retaining so that the mining-induced stress of the key rock strata of the working faces on the two sides of the gob-side entry retaining can be eliminated. According to the wall column type gob-side entry retaining surrounding rock stress control method, the overlying strata on the stoping working faces on the two sides of the gob-side entry retaining are effectively weakened, the working face overlying strata are promoted to stabilize key strata to form a weakening zone, and the situation that stable overlying strata structures cannot be formed on the working faces on the two sides of the entry retaining is eliminated; therefore, the strong mining-induced stress of the gob-side entry retaining in the whole service period is effectively adjusted and controlled, and the gob-side entry retaining in the whole service period is guaranteed to be safe and stable.

Description

Technical Field

[0001] The invention relates to the technical field of tunnel support, and in particular to a wall-column type gob-side tunnel retaining surrounding rock stress control method. Background Art

[0002] The technology of gob-side entry retention without coal pillars is a green and efficient way of mining coal resources. It is divided into two types: wall / pillar entry retention and wall-free self-formed entry retention. Among them, the wall / pillar entry retention and gob-side entry retention without coal pillars technology has been fully matured and basically solved the stability problem of surrounding rock in the entry.

[0003] The surrounding rock of the gob-retained roadway experiences the influence of mining stress disturbance caused by the mining of two different working faces during the roadway service period and the roadway reuse period. During the mining of the roadway-retained working face, the wall or column can effectively support the rotation and sinking movement of the overburden rock strata in the goaf, but it also changes the fracture position of the key rock strata overlying the goaf that controls the movement of the rock strata, making the fracture position of the overburden key rock strata in the goaf very likely to be located above the roadway roof. After the roadway-retained working face is mined, the fracture movement of the overburden key rock strata in the goaf causes rotation and slippage, which will cause the surrounding rock of the roadway to suffer strong mining stress and cause large deformation damage, and cause stress deformation damage to the roadway roof along the gob. Since the roadway-retained working face and the roadway-reused working face share the roadway-retained service for mining, the inclined advance fracture of the mining roof of the roadway-reused working face is at the same position as the inclined fracture of the overburden rock roof of the roadway-retained working face, that is, the mining of the roadway-reused working face will also cause the roadway to suffer strong mining stress and cause deformation damage. Summary of the invention

[0004] The invention provides a wall-column type gob-side tunnel retaining surrounding rock stress control method for solving the defect in the prior art that the gob-side tunnel retaining is easily subjected to strong mining stress and causes deformation and damage.

[0005] The present invention provides a method for controlling surrounding rock stress of a wall-column type gob-side entry retaining, comprising: Based on geological data, obtain the number and position of overburden layers above the roof of gob-side entry retention; Based on the number and position of overburden layers above the roof of gob-side entry retention, determine the number and position of key rock layers controlling rock strata movement above the roof of gob-side entry retention; The key rock strata that control the movement of rock strata above the top plate of the gob-side tunnel retaining are fractured and weakened, and the fracture weakening positions are located above the working faces on both sides of the gob-side tunnel retaining to eliminate the mining stress of the key rock strata on the working faces on both sides of the gob-side tunnel retaining.

[0006] According to a wall-column type gob-side entry retaining surrounding rock stress control method provided by the present invention, the number and position of key rock layers controlling rock layer movement above the top plate of the gob-side entry retaining are determined, including: Based on the load data of the overburden above the roof of the gob-side entry retaining, determine the position of the hard rock layer in the overburden above the roof of the gob-side entry retaining; Calculate the breaking distance of the hard rock layer in the overburden above the roof of the gob-side entry; Based on the breaking distance of the hard rock strata, the number and position of the key rock strata controlling the movement of the rock strata above the top plate of the gob-side entry are determined.

[0007] According to a wall-column type gob-side entry retaining surrounding rock stress control method provided by the present invention, The load data of the hard rock layer meets the following formula: Formula 1: ; Formula 2: ; Formula 3: ; In the formula, For the The maximum control range of the hard rock layer; Indicates the overburden above the roof of gob-side entry The load of the overburden rock on the mth hard rock layer; Indicates the overburden above the roof of gob-side entry Layered rock Loads acting on hard rock layers; represents the elastic modulus of the corresponding rock formation; Indicates the thickness of the corresponding rock layer; Indicates the bulk density of the corresponding rock formation.

[0008] According to a wall-column type gob-side entry retaining surrounding rock stress control method provided by the present invention, the breaking distance of the key rock layer above the top plate of the gob-side entry retaining that controls the movement of the rock layer satisfies the following formula: Formula 4: ; Formula 5: ; Formula 6: ; In the formula, Indicates The breaking distance of a hard rock layer; Indicates The breaking distance of a hard rock layer; Indicates the thickness of the corresponding rock layer; Indicates the load on the corresponding rock formation; Indicates the tensile strength of the corresponding rock formation.

[0009] According to a wall-column type gob-side entry retaining surrounding rock stress control method provided by the present invention, the fracturing and weakening of the key rock formation controlling the movement of the rock formation above the top plate of the gob-side entry retaining comprises: Determine the number and distribution of drilling sites based on the effective fracturing length of the fracturing equipment and the length of the goaf-side retaining tunnel; Arrange fracturing equipment at the first drilling site, and perform fracturing from high-level layers to low-level layers based on the number and positions of key rock layers that control rock movement above the top plate of the gob-side entry, until all key rock layers are fractured at the first drilling site; All key rock formations are subjected to stratum fracturing in other drilling sites in turn.

[0010] According to a wall-column type gob-side entry retaining surrounding rock stress control method provided by the present invention, the determining the number and distribution of drilling sites includes: Get the effective fracturing length of the fracturing equipment and length of gob-side entry , then the number of drilling sites a satisfies: , along the length direction of the gob-side entry There are a drill sites evenly distributed per unit length.

[0011] According to a wall-column type gob-side entry retaining surrounding rock stress control method provided by the present invention, the effective fracturing length of the fracturing equipment satisfy: .

[0012] According to a wall-column type gob-side tunnel retaining surrounding rock stress control method provided by the present invention, the drilling site is arranged in the gob-side tunnel retaining, and the fracturing boreholes used for fracturing are drilled on the top plate of the gob-side tunnel retaining and extend toward the working faces on both sides of the gob-side tunnel retaining to form a turning section borehole and a horizontal section borehole, and the horizontal section borehole is located in the key rock formation and parallel to the length direction of the gob-side tunnel retaining.

[0013] According to a wall-column type gob-side entry retaining surrounding rock stress control method provided by the present invention, among all key rock formations, the horizontal section drill hole in the lowest key rock formation is at least 15m higher than the top plate of the gob-side entry retaining, and the longitudinal extension range of the cracks in the hydraulic fracturing of the fracturing equipment is 5~8m.

[0014] According to a wall-column type gob-side entry retaining surrounding rock stress control method provided by the present invention, the horizontal distance between the horizontal section borehole and the side wall of the gob-side entry retaining is 5-10m.

[0015] The wall-column type goaf-side tunnel surrounding rock stress control method provided by the present invention, by fracturing and weakening the key rock strata, the fracture position of the key rock strata overlying the goaf of the tunnel-retaining working face is transferred to the area above the goaf, that is, the fracture position is located in the overlying area of ​​the goaf outside the wall column, and the fracture and collapse process of the overlying rock strata in the goaf no longer acts on the roof of the tunnel-retaining along the goaf, so that the force of the surrounding rock of the tunnel-retaining along the goaf can be greatly reduced, which is very beneficial to the safety and stability of the surrounding rock of the tunnel-retaining along the goaf. Similarly, the advanced tendency fracture position of the roof of the tunnel-retaining reuse working face is also moved outward to the tunnel-retaining reuse working face, and the advanced mining stress generated by the fracture and collapse process of the advanced roof of the tunnel-retaining reuse working face will not act on the tunnel-retaining along the goaf, thereby reducing and weakening the tunnel-retaining reuse from the advanced mining stress. In this way, the tunnel-retaining will not encounter the strong mining stress caused by the mining of the two working faces during the entire service period, ensuring the stable and safe use of the tunnel-retaining along the goaf during the entire service period. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In order to more clearly illustrate the technical solutions in the present invention or 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 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.

[0017] Figure 1 It is a schematic flow chart of the surrounding rock stress control method of the wall-column type gob-side entry retaining provided by the present invention.

[0018] Figure 2 It is a schematic diagram of the inclined overburden structure and stress distribution of the existing retained lane working face.

[0019] Figure 3 It is a schematic diagram of the inclined overburden structure and stress distribution of the existing retained lane reuse working face.

[0020] Figure 4 It is a schematic diagram of the inclined overburden structure and stress distribution of the lane retaining working face after the wall-column type gob-side lane retaining surrounding rock stress control method provided by the present invention is implemented.

[0021] Figure 5 It is a schematic diagram of the inclined overburden structure and stress distribution of the lane retaining reuse working face after the wall-column type goaf-side lane retaining surrounding rock stress control method provided by the present invention is implemented.

[0022] Figure 6 It is a schematic diagram of anchor support for the top plate of the retained lane after the wall-column type goaf-side retained lane surrounding rock stress control method provided by the present invention is implemented.

[0023] Figure 7 It is a schematic diagram of the plane layout of the lane retaining working face during the implementation of the wall-column type gob-side lane retaining surrounding rock stress control method provided by the present invention.

[0024] Figure 8 It is a schematic diagram of the arrangement of fracturing drilling holes in a single drilling field of the wall-column type gob-side tunnel retaining surrounding rock stress control method provided by the present invention.

[0025] Attached figure numbers: 1. Lane retention along the air; 2. Wall column; 3. Roof; 4. Lane retention working face; 5. Lane retention reuse working face; 6. Anchor cable; 7. Anchor rod; 8. Drilling of the change-of-direction section; 9. Drilling of the horizontal section. DETAILED DESCRIPTION

[0026] In order to make the purpose, technical solution and advantages of the present invention clearer, the technical solution of the present invention will be clearly and completely described below in conjunction with the drawings of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. 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.

[0027] In the description of the embodiments of the present invention, it should be noted that the terms "center", "longitudinal", "lateral", "up", "down", "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 accompanying drawings, and are only for the convenience of describing the embodiments of the present invention and simplifying the description, and do not indicate or imply that the devices or elements referred to must have a specific orientation, be constructed and operate in a specific orientation, and therefore cannot be understood as limitations on the embodiments of the present invention. In addition, the terms "first", "second", and "third" are used for descriptive purposes only and cannot be understood as indicating or implying relative importance.

[0028] In the description of the embodiments of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "connected" and "connection" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium. For ordinary technicians in this field, the specific meanings of the above terms in the embodiments of the present invention can be understood according to specific circumstances.

[0029] In the embodiments of the present invention, unless otherwise clearly specified and limited, the first feature being "above" or "below" the second feature may mean that the first and second features are in direct contact, or the first and second features are in indirect contact through an intermediate medium. Moreover, the first feature being "above", "above" and "above" the second feature may mean that the first feature is directly above or obliquely above the second feature, or simply means that the first feature is higher in level than the second feature. The first feature being "below", "below" and "below" the second feature may mean that the first feature is directly below or obliquely below the second feature, or simply means that the first feature is lower in level than the second feature.

[0030] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the embodiment of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, without contradiction.

[0031] Combine the following Figures 1 to 8 The specific implementation process of the wall-column type gob-side entry retaining surrounding rock stress control method of the present invention is described.

[0032] During coal mining, the surrounding rock of gob-side retained lanes experiences mining stress disturbance caused by two different working faces: the retained lane use period and the retained lane reuse period. Figure 2 The existing 4-dimension overburden structure and stress distribution of the reserved working face are shown in Fig. Figure 2 As shown in the figure, since the wall column 2 can effectively support the rotation and sinking movement of the overlying rock strata in the goaf, the fracture position of the key rock strata overlying the goaf that controls the movement of the rock strata is changed, and the fracture position of the key rock strata overlying the goaf is very likely to be located in the area above the roof 3 above the goaf-retaining roadway 1. Assuming that the fracture position of the key rock strata overlying the goaf is located above the roof 3, after the goaf-retaining working face 4 is mined, the fracture movement of the key rock strata overlying the goaf causes rotation and sliding, causing the surrounding rock of the goaf-retaining roadway 1 to suffer strong mining stress, resulting in large deformation and damage of the goaf-retaining roadway 1. Figure 3 The existing retained tunnel reuse working face 5 shows the overburden structure and stress distribution diagram, see Figure 3As shown in the figure, since the gob-retaining working face 4 and the gob-retaining reuse working face 5 share the gob-retaining gob 1 to serve the mining of the two working faces, it is determined that the advanced fracture of the mining roof 3 of the gob-retaining reuse working face 5 is at the same position as the inclined fracture of the overburden roof of the gob-retaining working face 4. After the mining of the gob-retaining reuse working face 5, the key rock strata overlying the gob will also rotate and slip due to the fracture movement, causing the surrounding rock of the gob-retaining gob 1 to suffer strong mining stress, resulting in large deformation and damage of the gob-retaining gob 1.

[0033] An embodiment of the present invention provides a method for controlling surrounding rock stress of a wall-column type gob-side entry retaining, see Figure 1 As shown, the following steps S1 to S3 are included.

[0034] S1. Based on geological data, obtain the number and position of overburden layers above the top plate of gob-side entry retention.

[0035] S2. Based on the number and position of the overburden above the top plate of the gob-side entry retaining, determine the number and position of the key rock layers that control the movement of the rock layers above the top plate of the gob-side entry retaining.

[0036] S3. The key rock strata that control the movement of rock strata above the top plate of the gob-side tunnel retaining are fractured and weakened, and the fracture weakening position is located above the working faces on both sides of the gob-side tunnel retaining to eliminate the mining stress of the key rock strata on both sides of the working faces of the gob-side tunnel retaining.

[0037] It can be understood that the wall-column type goaf-side tunnel surrounding rock stress control method of the present embodiment is to reduce the stress degree of the surrounding rock of the goaf-side tunnel 1 by controlling and changing the fracture position of the key rock strata overlying the goaf area of ​​the tunnel retaining working face 4 / tunnel retaining reuse working face 5. Specifically, the key rock strata above both sides of the top plate 3 of the goaf-side tunnel 1 are fractured and weakened to eliminate the mining stress of the key rock strata on both sides of the working faces of the goaf-side tunnel 1.

[0038] See also Figure 4 As shown, by fracturing and weakening the key rock strata, the fracture position of the key rock strata overlying the goaf of the goaf working face 4 is transferred to the area above the goaf, that is, the fracture position is located in the area overlying the goaf outside the wall column 2, and the fracture and collapse process of the overlying rock strata in the goaf no longer acts on the roof 3 of the goaf-retained goaf 1, which can greatly reduce the stress on the surrounding rock of the goaf-retained goaf 1, which is very beneficial to the safety and stability of the surrounding rock of the goaf-retained goaf 1. Similarly, see Figure 5 As shown, the advanced tendency fracture position of the roof 3 of the tunnel-retaining reuse working face 5 is also moved outward to the tunnel-retaining reuse working face 5, and the advanced mining stress generated by the advanced roof fracture and collapse process of the tunnel-retaining reuse working face 5 will not act on the tunnel-retaining along the goaf 1, thereby reducing the advanced mining stress suffered by the tunnel-retaining reuse. In this way, the tunnel-retaining will not encounter the strong mining stress caused by the mining of the two working faces during the entire service period, ensuring the stable and safe use of the tunnel-retaining along the goaf 1 during the entire service period.

[0039] contrast Figure 2 and Figure 4 The stress distribution below and the comparison Figure 3 and Figure 5 From the stress distribution below, it can be seen that the wall-column type gob-side tunnel surrounding rock stress control method of this embodiment weakens the key stable rock strata overlying the tunnels of the two working faces. After the tunnel working face 4 is pushed out, the roof tends to collapse into the gob area, and a stable overburden structure cannot be formed. Figure 4 As shown in the figure, a medium that cannot conduct stress is formed, which fundamentally eliminates mining stress. Similarly, in the process of mining with the reserved lane reuse working face 5, the function of conducting stress is also lost because the roof overburden is weakened and cannot form a stable structure, as shown in the figure. Figure 5 As shown, the advanced mining stress is fundamentally eliminated. Through the wall-column type surrounding rock stress control method of the gob-side tunnel retention of this embodiment, the overburden strata on the mining working faces on both sides of the gob-side tunnel retention 1 are effectively weakened, so that the key rock strata for the stability of the overburden of the working face form a weakened zone, and the working faces on both sides of the tunnel retention cannot form a stable overburden structure, thereby effectively regulating and controlling the strong mining stress of the gob-side tunnel retention 1 throughout the service period, and ensuring the safety and stability of the gob-side tunnel retention 1 throughout the service period.

[0040] Based on the wall-column type goaf-side tunneling surrounding rock stress control method in the above-mentioned embodiment, in some embodiments of the wall-column type goaf-side tunneling surrounding rock stress control method of the present invention, judging the number and position of key rock layers controlling the movement of rock layers above the top plate of the goaf-side tunneling includes the following steps S21~S23.

[0041] S21, determining the position of the hard rock layer in the overburden above the top plate of the gob-side entry retaining based on the load data of the overburden above the top plate of the gob-side entry retaining; S22, calculate the breaking distance of the hard rock layer in the overburden above the top plate of the gob-side entry; S23. Based on the breaking distance of the hard rock layer, determine the number and position of the key rock layers that control the movement of the rock layers above the top plate of the gob-side entry.

[0042] It can be understood that the hard rock layer in step S21 refers to those rock layers whose deflection during deformation is smaller than that of the lower rock layer and which do not coordinate deformation with the lower rock layer. By calculating the load data of the overburden above the top plate 3 of the gob-side entry, the position of the hard rock layer in the overburden above the top plate 3 of the gob-side entry is determined from bottom to top. The rock formation is hard and its control range reaches layer, then the upper Layer load is less than The load on the rock layer is calculated The load data of the hard rock layer meets the following formula: , and , where For the The maximum control range of the hard rock layer; Indicates the overburden above the roof of gob-side entry The load of the overburden rock on the mth hard rock layer; Indicates the overburden above the roof of gob-side entry retention Layered rock Loads acting on hard rock layers; represents the elastic modulus of the corresponding rock formation; Indicates the thickness of the corresponding rock layer; represents the bulk density of the corresponding rock layer, then the The rock layer is a hard rock layer. By performing load calculation on the overburden above the roof 3 of the gob-side entry retention one by one, the positions of all hard rock layers in the overburden and the soft rock layer groups controlled by them are obtained.

[0043] After determining the positions of all hard rock formations, calculate the breaking distance of the hard rock formations, and determine the number and position of the key rock formations above the top plate of the gob-side entry that control the movement of the rock formations based on the breaking distance of the hard rock formations. The breaking distance of the key rock formations above the top plate of the gob-side entry that control the movement of the rock formations needs to satisfy the following formula: , and ; In the formula, Indicates The breaking distance of a hard rock layer; Indicates The breaking distance of a hard rock layer; Indicates the thickness of the corresponding rock layer; Indicates the load on the corresponding rock formation; It represents the tensile strength of the corresponding rock layer. Through the above process, the number and position of the key rock layers controlling the movement of the rock layers above the top plate of the goaf-retained entry can be determined, which can be used for subsequent targeted hydraulic fracturing weakening.

[0044] In some embodiments of the wall-column type gob-side retaining surrounding rock stress control method of the present invention, fracturing and weakening the key rock strata that control the movement of the rock strata above the gob-side retaining roof includes: determining the number and distribution of drilling sites based on the effective fracturing length of the fracturing equipment and the length of the gob-side retaining 1; arranging the fracturing equipment in the determined first drilling site, and based on the number and position of the key rock strata that control the movement of the rock strata above the gob-side retaining roof 3, fracturing is performed from the high-level layer to the low-level layer in sequence until the stratum fracturing of all the key rock strata is completed in the first drilling site; and sequentially performing stratum fracturing of all the key rock strata in other drilling sites.

[0045] Specifically, determining the number and distribution of drilling sites includes: obtaining the effective fracturing length of the fracturing equipment and length of gob-side entry , then the number of drilling sites a satisfies: , along the length direction of the gob-side entry The effective fracturing length of the fracturing equipment is a uniformly distributed drilling site per unit length. It is obtained based on the equipment capacity of the fracturing tool string and the long-distance fracturing efficiency of the fracturing equipment. Generally speaking, the effective fracturing length of the fracturing equipment The maximum length shall not exceed 500m, and the minimum effective fracturing length shall not be less than 200m.

[0046] First, a kilometer-long directional drilling rig is used to select the first drilling site in the underground gob retention lane 1 to drill a horizontal fracturing borehole, and then a special pushing equipment is used to push the fracturing tool string to the specified position of the borehole, and then a fracturing pump is used to perform fracturing operations. A single borehole adopts a segmented sequential fracturing method, and hydraulic fracturing is carried out in sections from the deepest part of the borehole. The segmented fracturing length is set to b, and the number of fracturing times is , where b ranges from 15m to 30m. The fracturing sequence of key rock formations is from high layers to low layers one by one until all key rock formations are fracturing, and then the fracturing is moved to the second drilling site to repeat the above work until all drilling and fracturing operations are completed.

[0047] In some other embodiments of the wall-column type gob-side entry retaining surrounding rock stress control method of the present invention, the drilling site is arranged in the gob-side entry retaining 1, combined with Figure 7 and Figure 8 As shown, the fracturing boreholes used for fracturing are drilled in the top plate 3 of the gob-side tunnel 1 and extend toward the working faces on both sides of the gob-side tunnel 1 to form a redirection section borehole 8 and a horizontal section borehole 9. The horizontal section borehole 9 is located in the key rock formation and is parallel to the length direction of the gob-side tunnel 1.

[0048] It is understandable that in order to prevent the eventually weakened and collapsed rock strata from affecting the goaf-retained tunnel 1 during the collapse and sinking process, it is necessary to ensure that a certain space is left between the horizontal section borehole 9 and the side wall of the goaf-retained tunnel 1. This space is used for crack expansion due to hydraulic fracturing. Generally, the horizontal distance between the horizontal section borehole 9 and the side wall of the goaf-retained tunnel 1 is 5 to 10 m, and the crack expansion range of hydraulic fracturing is 5 to 8 m.

[0049] The drilling site is arranged in the gob-side tunnel 1, and the fracturing borehole used for fracturing is drilled in the roof 3 of the gob-side tunnel 1. Since the roof 3 and the upper rock formation need to be supported by anchor cables 6 and anchor rods 7, in order to ensure the support effect of the anchor cables 6 and anchor rods 7, see Figure 6 As shown, it is necessary to leave a certain unweakened stable area above the top plate 3, combined with Figure 7 and Figure 8As shown, among all the key rock formations, the horizontal section drill hole in the lowest key rock formation is at least 15m higher than the top plate 3 of the goaf retaining, that is, the lowest key rock formation that will eventually be weakened by hydraulic fracturing is at least 15m higher than the top plate 3 of the goaf retaining, the length of the anchor cable 6 and the anchor rod 7 is generally about 8m, and the longitudinal extension range of the cracks caused by hydraulic fracturing by the fracturing equipment is 5~8m, which ensures that the unweakened stable area for anchoring the anchor cable 6 and the anchor rod 7 can be reserved in the end.

[0050] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for controlling surrounding rock stress of a wall-column type gob-side entry retaining, characterized in that: include: Based on geological data, obtain the number and position of overburden layers above the roof of gob-side entry retention; Based on the number and position of overburden layers above the roof of gob-side entry retention, determine the number and position of key rock layers controlling rock strata movement above the roof of gob-side entry retention; The key rock strata that control the movement of rock strata above the top plate of the gob-side tunnel retaining are fractured and weakened, and the fracture weakening positions are located above the working faces on both sides of the gob-side tunnel retaining to eliminate the mining stress of the key rock strata on the working faces on both sides of the gob-side tunnel retaining.

2. The surrounding rock stress control method of wall-column type gob-side entry retaining according to claim 1 is characterized in that: The number and position of the key rock layers controlling the movement of rock layers above the roof of the gob-side entry retention are as follows: Based on the load data of the overburden above the roof of the gob-side entry retaining, determine the position of the hard rock layer in the overburden above the roof of the gob-side entry retaining; Calculate the breaking distance of the hard rock layer in the overburden above the roof of the gob-side entry; Based on the breaking distance of the hard rock strata, the number and position of the key rock strata controlling the movement of the rock strata above the top plate of the gob-side entry are determined.

3. The surrounding rock stress control method of wall-column type gob-side entry retaining according to claim 2 is characterized in that: No. The load data of the hard rock layer meets the following formula: Formula 1: ; Formula 2: ; Formula 3: ; In the formula, For the The maximum control range of the hard rock layer; Indicates the overburden above the roof of gob-side entry The load of the overburden rock on the mth hard rock layer; Indicates the overburden above the roof of gob-side entry retention Layered rock Loads acting on hard rock layers; represents the elastic modulus of the corresponding rock formation; Indicates the thickness of the corresponding rock layer; Indicates the bulk density of the corresponding rock formation.

4. The surrounding rock stress control method of wall-column type gob-side entry retaining according to claim 3 is characterized in that: The breaking distance of the key rock layer above the roof of the gob-side entry retaining that controls the movement of the rock layer satisfies the following formula: Formula 4: ; Formula 5: ; Formula 6: ; In the formula, Indicates The breaking distance of a hard rock layer; Indicates The breaking distance of a hard rock layer; Indicates the thickness of the corresponding rock layer; Indicates the load on the corresponding rock formation; Indicates the tensile strength of the corresponding rock formation.

5. The surrounding rock stress control method of a wall-column type gob-side entry retaining according to any one of claims 1 to 4, characterized in that: The fracturing and weakening of the key rock formations controlling the movement of rock formations above the top plate of the gob-side entry retention includes: Determine the number and distribution of drilling sites based on the effective fracturing length of the fracturing equipment and the length of the goaf-side retaining tunnel; Arrange fracturing equipment at the first drilling site, and perform fracturing from high-level layers to low-level layers based on the number and positions of key rock layers that control rock movement above the top plate of the gob-side entry, until all key rock layers are fractured at the first drilling site; All key rock formations are subjected to stratum fracturing in other drilling sites in turn.

6. The surrounding rock stress control method of wall-column type gob-side entry retaining according to claim 5 is characterized in that: Determining the number and distribution of drilling sites includes: Get the effective fracturing length of the fracturing equipment and length of gob-side entry , then the number of drilling sites a satisfies: , along the length direction of the gob-side entry There are a drill sites evenly distributed per unit length.

7. The surrounding rock stress control method of wall-column type gob-side entry retaining according to claim 6 is characterized in that: The effective fracturing length of the fracturing equipment satisfy: .

8. The surrounding rock stress control method of wall-column type gob-side entry retaining according to claim 5 is characterized in that: The drilling site is arranged in the gob-side tunnel, and the fracturing boreholes used for fracturing are drilled on the top plate of the gob-side tunnel and extend toward the working faces on both sides of the gob-side tunnel to form a turning section borehole and a horizontal section borehole. The horizontal section borehole is located in the key rock formation and is parallel to the length direction of the gob-side tunnel.

9. The surrounding rock stress control method of wall-column type gob-side entry retaining according to claim 8 is characterized in that: Among all the key rock formations, the horizontal section borehole in the lowest key rock formation is at least 15m higher than the top plate of the gob-side tunnelling, and the longitudinal extension range of the cracks caused by hydraulic fracturing by the fracturing equipment is 5~8m.

10. The surrounding rock stress control method of wall-column type gob-side entry retaining according to claim 8, characterized in that: The horizontal distance between the horizontal section borehole and the side wall of the gob-retained tunnel is 5 to 10 meters.

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