Design method of self-forming lane by cutting top of close-distance coal seam

Abstract

The present invention provides a design method for self-forming lanes by cutting off the top of a close-range coal seam, which relates to the technical field of coal mining safety control. Aiming at the current problems of great support difficulty and poor stability during mining of close-range coal seams under overlying goafs, the influence of collapse of overlying goafs on lanes is considered, support design is carried out in different areas based on the deadweight of the working face roof, and constrained concrete columns and unit hydraulic supports are introduced for alternating support to achieve active and passive coordinated support, reduce support difficulty, and improve lane stability.

Description

Technical Field

[0001] The invention relates to the technical field of coal mining safety control, and in particular to a method for designing a self-forming laneway by cutting the top of a close-range coal seam. Background Art

[0002] Traditional underground coal mining mostly uses coal pillar mining, which wastes a lot of coal pillar resources. The current coal mining method of cutting the top and forming a lane can eliminate the need for coal pillars and recover a large amount of resources.

[0003] Close-range coal seams are coal seams that are close in distance and have significant mutual influence during mining. In the occurrence state of coal seams, the mutual influence of coal seam spacing on mining is the main factor. After the adjacent coal seams are mined, the stress distribution law and deformation and failure characteristics of their surrounding rocks will change significantly. When mining close-range coal seams under the overlying goaf, the tunnel roof is thin, the scope of applying anchoring structure is limited, the construction of anchoring structure is inconvenient, and support is difficult. In particular, the mining impact caused by the collapse of the overburden rock at the working face is severe, and the dynamic pressure in the tunnel is large, which can easily lead to roof collapse accidents in the tunnel. Summary of the invention

[0004] The purpose of the present invention is to provide a design method for cutting the top of a close-range coal seam to form a self-contained tunnel in response to the defects of the prior art, taking into account the impact of the collapse of the overlying goaf on the tunnel, carrying out support design in different areas based on the deadweight of the working face roof, introducing constrained concrete columns and unit hydraulic supports for alternating support, realizing active and passive coordinated support, reducing the difficulty of support, and improving the stability of the tunnel.

[0005] The purpose of the present invention is to provide a method for designing a self-forming lane by cutting the top of a close-range coal seam, which adopts the following scheme:

[0006] include:

[0007] Measure the rock layer parameters of the working face roof, calculate the parameters of the tunnel reinforcement support and configure the tunnel reinforcement support accordingly;

[0008] For the dynamic pressure section, restrained concrete columns and unit hydraulic supports are used for alternate support along the extension direction of the tunnel on the goaf side. The active support of the unit hydraulic support and the passive support of the restrained concrete columns work together. There are Π-shaped beams distributed between the restrained concrete columns and the unit hydraulic supports.

[0009] After the dynamic pressure section is stabilized, it will serve as the stable section. The unit hydraulic supports of the stable section will be withdrawn, and restrained concrete columns will be arranged at the position of the original unit hydraulic supports.

[0010] Furthermore, after measuring the rock strata parameters of the working face roof, the support resistance in the tunnel is calculated based on the fault zone, collapse zone, upper coal layer and the height of the working face roof, so that the reinforced support force in the tunnel is greater than the support resistance in the tunnel, and the top cutting height and top cutting angle are calculated, and the top cutting height is less than the thickness of the working face roof.

[0011] Furthermore, before configuring the reinforced support in the tunnel, constant resistance and large deformation anchor cables are injected on the tunnel working face side and the middle of the tunnel for support, and pre-cracking and cutting are performed; the support length of the constant resistance and large deformation anchor cables is less than the thickness of the working face roof and is located below the top surface of the working face roof.

[0012] Furthermore, for the dynamic pressure section, two spaced constrained concrete columns are provided between two adjacent unit hydraulic supports, and a constrained concrete column is arranged at the position after the original unit hydraulic supports are withdrawn in the stable section.

[0013] Furthermore, the constrained concrete column is made by pouring core concrete into the external constraining material, and the parameters of the constrained concrete include cross-sectional shape and size, external constraining material wall thickness, concrete strength, external constraining material strength, and overall height.

[0014] Furthermore, the cross-section of the constrained concrete is circular or square, the external constraining material is steel, the strength of the internal poured core concrete is C20-C70, and the height of the constrained concrete is the height of the roadway.

[0015] Furthermore, a pad for supporting the confined concrete is provided on the top of the confined concrete.

[0016] Furthermore, a pressure-yielding flexible cushion layer is provided above the cushion plate, and the pressure-yielding flexible cushion layer fits the tunnel roof.

[0017] Furthermore, after the roof is cut, the tunnel cut holes are spied on, and the blasting parameters are adjusted according to the cut hole crack ratio; when the cut hole crack ratio is not less than the set value, the top cutting effect is judged to be good; when the cut hole crack ratio is less than the set value, the top cutting effect is judged to be poor, and the blasting parameters are adjusted; during blasting, the blasting parameters are controlled to maintain the stability of the tunnel.

[0018] Furthermore, during the mining process of the working face, the deformation of the surrounding rock in the tunnel and the stress of the reinforced support components in the tunnel are monitored, and feedback optimization is carried out.

[0019] Compared with the prior art, the present invention has the following advantages and positive effects:

[0020] (1) In view of the current problems of great support difficulty and poor stability when mining coal seams close to the overlying goaf, the impact of the collapse of the overlying goaf on the tunnel was considered. Based on the deadweight of the working face roof, support design was carried out in different areas. Constrained concrete columns and unit hydraulic supports were introduced for alternating support to achieve active and passive coordinated support, reduce support difficulty, and improve tunnel stability.

[0021] (2) Withdraw the unit hydraulic support and add a restraining concrete column at the position to prevent the subsequent top plate from sinking further, reduce the use of unit hydraulic supports, and maintain support stability. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] The accompanying drawings in the specification, which constitute a part of the present invention, are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations on the present invention.

[0023] Figure 1 This is a schematic diagram of close-range coal seam mining before rock stratum mining in Example 1 of the present invention.

[0024] Figure 2 It is a schematic diagram of the rock stratum after mining and before top cutting in the close-range coal seam mining in Example 1 of the present invention.

[0025] Figure 3 It is a schematic diagram of the top cutting after the close-range coal seam mining rock stratum is mined in Example 1 of the present invention.

[0026] Figure 4 It is a schematic diagram of the design method of cutting the top of a close-range coal seam to form a lane in Example 1 of the present invention.

[0027] Figure 5 It is a schematic diagram of the reinforcement support in the dynamic pressure section of the tunnel in Example 1 of the present invention.

[0028] Figure 6 It is a schematic flow chart of the method for designing a self-forming lane by cutting off the top of a close-range coal seam in Example 1 of the present invention. DETAILED DESCRIPTION

[0029] Example 1

[0030] In a typical embodiment of the present invention, Figure 1-Figure 6 As shown, a design method for cutting the top of a close-range coal seam to form a self-contained lane is given.

[0031] See also Figure 1 , the design methods for cutting the top of the close-distance coal seam into a self-forming lane include:

[0032] Measure the rock layer parameters of the working face roof, calculate the parameters of the tunnel reinforcement support and configure the tunnel reinforcement support accordingly;

[0033] For the dynamic pressure section, restrained concrete columns and unit hydraulic supports are used for alternate support along the extension direction of the tunnel on the goaf side. The active support of the unit hydraulic support and the passive support of the restrained concrete columns work together. There are Π-shaped beams distributed between the restrained concrete columns and the unit hydraulic supports.

[0034] After the dynamic pressure section is stabilized, it will serve as the stable section. The unit hydraulic supports of the stable section will be withdrawn, and restrained concrete columns will be arranged at the position of the original unit hydraulic supports.

[0035] like Figure 1-Figure 6As shown, the design method of cutting the top of the close-range coal seam to form a self-contained lane is explained in detail as follows.

[0036] Obtain the rock parameters of the working face roof through geological exploration, especially the roof thickness h, and also determine the coal seam mining height ;

[0037] According to the thickness of the roof rock layer, the constant resistance large deformation anchor cable is designed, and the top cutting parameter design of the self-forming roadway in the close-range coal seam top cutting and the reinforcement support design in the roadway are carried out;

[0038] The support strength and economic efficiency are verified based on the basic parameters of the support design to determine the appropriate support plan, and ultimately form a construction design for close-range coal seam top cutting and self-forming tunneling.

[0039] In this embodiment, the design of the constant resistance large deformation anchor cable includes:

[0040] Before pre-splitting, at least one row of constant resistance large deformation anchor cables shall be installed on the side of the cut. The length of the anchor cables, including the anchor cable support length, shall be 500-800mm lower than the top plate thickness h. The parameters such as the spacing between rows shall be reasonably adjusted according to the on-site geological conditions. Figure 3 As shown in the figure, the constant resistance large deformation anchor cable works together with the existing anchor cables and anchor rods in the tunnel to maintain the stability of the structure in the tunnel.

[0041] Combination Figure 4 and Figure 5 The design of top cutting parameters for self-cutting roadways in close distance coal seams mainly includes top cutting height and top cutting angle. The selection range of roadway top cutting angle is 10°-30°, and the design value of top cutting height is ,in .when When While allowing the roof to collapse smoothly, it is necessary to prevent gas and water from the overlying goaf from flowing into the tunnel along the cut holes, which could cause safety hazards.

[0042] In the design of reinforcement support inside the self-formed tunnel of the close-range coal seam top cutting, constant resistance large deformation anchor cables, unit hydraulic supports, single pillars, Π-shaped beams, portal supports, constrained concrete columns, etc. are mainly used.

[0043] The support resistance of the self-formed tunnel is calculated. Assuming that the collapse height of the overlying rock layer is H+h+h', the weight of the collapsed rock mass during coal mining in this layer is ,in, is the height of the collapse zone, is the height of the fault zone, h is the height of the roof, and h' is the height of the upper coal seam.

[0044] The support resistance per meter of tunnel is F=γG, where γ is the safety factor, and its value range is 1.5~2.5. The greater the weight of the collapsed rock mass, the greater the value of γ. At the same time, after the design of the top cutting parameters and the design of the reinforcement support in the tunnel are completed, the support effect needs to be verified by means of numerical simulation and other means. The support force provided by the support component should not be less than the support resistance F=γG to ensure that the support component can effectively control the deformation of the surrounding rock.

[0045] like Figure 6 As shown in the figure, the support resistance is mainly provided by the restrained concrete columns, and the main design parameters of the restrained concrete columns include cross-sectional shape and size, wall thickness of external restraining material, concrete strength, strength of external restraining material, overall height, etc. The parameters of related supporting equipment also need to be designed, including pad thickness and cross-sectional size.

[0046] The design parameters of the restrained concrete column are as follows: The restrained concrete cross-section selection includes square and circular (assuming the side length is a and the radius is r), the external restraint material is usually steel (assuming the wall thickness is t), and the concrete strength is selected in the range of C20~C70 (assuming the strength is ), the overall height is designed to be the tunnel height.

[0047] The ultimate bearing capacity of the confined concrete column is calculated by the relevant confined concrete column design parameters. The specific calculation process includes:

[0048] The first step is to calculate the interaction coefficient between the confined material and concrete in the confined concrete. The calculation formula is as follows:

[0049] (1)

[0050] Where: is the interaction coefficient between the constraint material and concrete, To constrain the cross-sectional area of ​​the material, is the cross-sectional area of ​​concrete, To constrain the material yield strength, is the axial compressive strength of concrete.

[0051] Step 2: Calculate the combined axial compressive strength of the confined concrete columns:

[0052] (2)

[0053] Where: is the combined axial compressive strength of confined concrete columns.

[0054] The third step is to calculate the ultimate bearing capacity of confined concrete. The calculation formula is as follows:

[0055] (3)

[0056] Where: To constrain the ultimate bearing capacity of concrete, is the cross-sectional area of ​​the confined concrete column, , is the combined axial compressive strength of confined concrete columns.

[0057] In order to verify the accuracy of the calculation, the bearing capacity of the confined concrete columns can be checked by carrying out numerical simulation.

[0058] Constrained concrete columns have the characteristics of high bearing capacity and low cost. Although unit hydraulic supports, single pillars, Π-shaped beams, portal supports, etc. are expensive, they are recyclable and reusable. When designing reinforced support, if the deformation of the surrounding rock can be controlled by using only support methods such as unit hydraulic supports, single pillars, Π-shaped beams, portal supports, etc., they should be used first. Otherwise, constrained concrete columns should be used for high-strength support, and a support design with constrained concrete columns as the core should be established.

[0059] In order to ensure that the restrained concrete columns can fully control the deformation of the surrounding rock on site and still have sufficient strength reserve, the ultimate bearing capacity of the restrained concrete must be guaranteed. , where F is the support resistance, To constrain the ultimate bearing capacity of concrete, k is the safety factor, and the value of k is between 1.5 and 2.0. The better the stability of the top slab surrounding rock, the smaller the value, and vice versa.

[0060] In order to ensure that the high-strength restrained concrete support does not damage the integrity of the top plate, it is necessary to ensure that ,in, is the ultimate bearing capacity of the confined concrete, A is the pad area, The tensile strength of the roof rock is to prevent the concrete columns from drilling through the roof. At the same time, the pad area should not be too large to avoid construction difficulties.

[0061] A flexible cushion layer can be used to prevent the restrained concrete column from drilling through the top plate and the high-strength support from becoming unstable. The flexible cushion layer can be made of waste materials such as wood blocks and rubber.

[0062] In this embodiment, after completing the calculation of support resistance, the dynamic pressure section of the self-forming lane is supported, wherein, Figure 4 As shown in the figure, the dynamic pressure section adopts restrained concrete columns and unit hydraulic supports for alternate support on the goaf side. A unit hydraulic support is installed after every two restrained concrete columns, where the restrained concrete is passive support and the unit hydraulic support is active support. The two work together actively and passively to achieve stable control of the tunnel roof. Figure 4As shown, after the dynamic pressure section is stabilized, it serves as a stable section, the unit hydraulic support is withdrawn, and a restraining concrete column is added at this position to prevent the subsequent top plate from continuing to sink.

[0063] Among them, the active support of the unit hydraulic support and the passive support of the constrained concrete column work together, and a Π-shaped beam is distributed between the constrained concrete column and the unit hydraulic support.

[0064] In addition, for the dynamic pressure section, two spaced constrained concrete columns are arranged between two adjacent unit hydraulic supports. One constrained concrete column is arranged at the original unit hydraulic support position.

[0065] The pressure in the dynamic pressure section is relatively large and the top plate sinks severely, so active and passive support are used together. After the dynamic pressure section is stable, the hydraulic support is withdrawn and transported forward and used alternately. Then, since the support resistance becomes smaller after the hydraulic support is withdrawn, the support resistance is guaranteed by adding constrained concrete columns.

[0066] It should be pointed out that when the unit hydraulic support is withdrawn, the unit hydraulic support slowly contracts, causing the top plate to gradually deform until it falls onto the restraining concrete column and is then carried by the restraining concrete column.

[0067] Different from the existing cast-in-place concrete wall support, the cast-in-place concrete wall needs to be constructed with formwork, which is difficult to construct. Even if an integral mold is used, it is inconvenient to transport and adjust the corresponding larger formwork in a narrow lane. In this embodiment, the constrained concrete column is smaller in overall volume and easier to transport. It is cast on the well, then cured for about a month and then transported to the well for construction. The strength of the constrained concrete column can be more effectively exerted.

[0068] Confined concrete is formed by pouring concrete into steel pipes or other external constraining materials. Due to the restraint of the external structure, the confined concrete has higher compressive strength, and the concrete ensures that the external constraints are not prone to instability and failure. The restraint structure and concrete carry the load together, and the two show a "symbiotic phenomenon" in mechanical properties, which makes it have the advantages of high strength, good ductility and low cost.

[0069] After the design of the cutting top parameters and the design of the reinforced support in the tunnel are completed, the support effect needs to be verified by means of numerical simulation and other means. The support force provided by the support components should not be less than the support resistance F=γG to ensure that the support components can effectively control the deformation of the surrounding rock. At the same time, the support components need to have sufficient rigidity to ensure that the support will not fail. Otherwise, it is necessary to replace the support system with higher strength and rigidity. Under the condition of meeting the strength and height requirements, it is advisable to select a lower-cost support method.

[0070] After the roof is cut, the tunnel cut holes are inspected and the blasting parameters are adjusted according to the cut hole crack rate. During blasting, the blasting parameters are controlled to maintain the stability of the tunnel. When the cut hole crack rate is not less than the set value, the top cutting effect is judged to be good; when the cut hole crack rate is less than the set value, the top cutting effect is judged to be poor, and the blasting parameters are adjusted.

[0071] Specifically, if the crack rate of the cut hole is greater than or equal to 75%, the top cutting effect is considered to be good, and if it is less than 75%, the top cutting effect is considered to be poor, and the blasting charge structure should be adjusted to increase the amount of explosives to ensure that the top cutting effect meets the expected requirements. At the same time, if the roof is broken and collapsed on a large scale after blasting, the charge should be reduced to avoid affecting the stability of the roadway.

[0072] During the mining process at the working face, the deformation of the surrounding rock in the tunnel and the stress of the supporting components should be monitored to ensure the stability of the surrounding rock in the tunnel and to timely conduct feedback and optimization of relevant parameters.

[0073] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A design method for cutting the top of a close-range coal seam to form a lane, characterized in that: include: Measure the rock layer parameters of the working face roof, calculate the parameters of the tunnel reinforcement support and configure the tunnel reinforcement support accordingly; For the dynamic pressure section, restrained concrete columns and unit hydraulic supports are used for alternate support along the extension direction of the tunnel on the goaf side. The active support of the unit hydraulic support and the passive support of the restrained concrete columns work together. There are Π-shaped beams distributed between the restrained concrete columns and the unit hydraulic supports. After the dynamic pressure section is stabilized, it will be used as the stable section, the unit hydraulic support of the stable section will be withdrawn, and the restrained concrete column will be arranged at the position of the original unit hydraulic support; For the dynamic pressure section, two spaced constrained concrete columns are set between two adjacent unit hydraulic supports, and a constrained concrete column is set at the position after the original unit hydraulic support is withdrawn in the stable section; the pressure in the dynamic pressure section is relatively large, and the top plate sinks seriously, so active and passive support are used together. After the dynamic pressure section is stable, the hydraulic support is withdrawn and transported forward, and used alternately. Then, since the support resistance becomes smaller after the hydraulic support is withdrawn, the support resistance is guaranteed by adding constrained concrete columns; After measuring the rock parameters of the working face roof, the support resistance in the tunnel is calculated based on the fault zone, collapse zone, upper coal layer and the height of the working face roof, so that the reinforcement support force in the tunnel is greater than the support resistance in the tunnel, and the top cutting height and top cutting angle are calculated. The top cutting height is less than the thickness of the working face roof. Before configuring the reinforced support in the tunnel, constant resistance large deformation anchor cables are injected on the tunnel working face side and the middle of the tunnel for support, and pre-cracking and cutting are performed; the support length of the constant resistance large deformation anchor cables is less than the thickness of the working face roof and is located below the top surface of the working face roof.

2. The method for designing a self-forming laneway by cutting the top of a close-range coal seam as claimed in claim 1, characterized in that: The constrained concrete column is made by pouring core concrete into the external constraining material. The parameters of the constrained concrete include cross-sectional shape and size, wall thickness of the external constraining material, concrete strength, strength of the external constraining material, and overall height.

3. The method for designing a self-forming laneway by cutting the top of a close-range coal seam as claimed in claim 1 or 2, characterized in that: The cross section of the confined concrete is circular or square, the external confining material is steel, the strength of the internally poured core concrete is C20-C70, and the height of the confining concrete is the height of the roadway.

4. The method for designing a self-forming laneway by cutting the top of a close-range coal seam as claimed in claim 3, characterized in that: A pad is provided on the top of the confined concrete to support it.

5. The method for designing a self-forming laneway by cutting the top of a close-range coal seam as claimed in claim 4, characterized in that: A pressure-yielding flexible cushion layer is arranged above the cushion plate, and the pressure-yielding flexible cushion layer fits the tunnel roof.

6. The method for designing a self-forming laneway by cutting the top of a close-range coal seam as claimed in claim 1, characterized in that: After the roof is cut, the cut holes in the tunnel are inspected and the blasting parameters are adjusted according to the crack ratio of the cut holes. When the crack ratio of the cut holes is not less than the set value, the cutting effect is judged to be good. When the crack ratio of the cut holes is less than the set value, the cutting effect is judged to be poor and the blasting parameters are adjusted. During blasting, the blasting parameters are controlled to maintain the stability of the tunnel.

7. The method for designing a self-forming laneway by cutting the top of a close-range coal seam as claimed in claim 1, characterized in that: During the mining process of the working face, the deformation of the surrounding rock in the tunnel and the stress of the reinforced support components in the tunnel are monitored, and feedback optimization is carried out.

Images