Bottomless column segmented parallel ore feeding method

Abstract

This invention relates to the field of mining methods, specifically to a bottomless, segmented parallel ore-draining method. The method comprises the following steps: S1. After the collapse of the access road of a first drilling roadway, the width of the collapsed section along the strike of the ore body is determined as L2. Multiple second drilling roadways are designed along the direction perpendicular to the strike of the ore body. The access distance M between adjacent second drilling roadways is determined based on the access distance m between adjacent first drilling roadways; S2. The number n of second drilling roadways is calculated based on the ore body access length L between the vein roadway and the cutting roadway, the width L1 of the collapsed section, the width L2 of the collapsed section, and the access distance M between adjacent second drilling roadways; S3. Based on the number n of second drilling roadways and the access distance M between adjacent second drilling roadways, second drilling roadways are deployed between the vein roadway and the cutting roadway for ore body recovery. This ore-draining method is applied to ore recovery after the collapse of a drilling roadway access roadway, significantly improving ore recovery efficiency and reducing dilution rate.

Description

Technical Field

[0001] This invention relates to the field of mining methods, specifically to a bottomless, segmented, parallel ore-discharging method. Background Technology

[0002] The sublevel caving mining method without pillars divides the stage into sub-sections using sub-roads; each sub-section is further divided into strips, each with a single mining roadway. There is no dedicated bottom structure for ore discharge within each strip; instead, ore is directly discharged and transported within the mining roadway. Mining is carried out sequentially between strips and from top to bottom between sub-sections. As the sub-section ore is mined, the overlying caving rock collapses and fills the goaf. Mining of the strips involves drilling upward-facing fan-shaped blast holes within the mining roadway, using small caving steps (1.5–3 m) to compress and blast the waste rock-filled caving area. The caved ore, under the loose overlying rock, is directly transported from the end floor of the mining roadway to the pass using loading equipment.

[0003] Under normal circumstances, ore blocks are arranged along the strike of the ore body. The main haulage roadway is located on the footwall of the ore body along the strike, and cross-vein roadways are arranged perpendicular to the ore body. Drilling roadways are excavated at regular intervals. Normally, each ore block is mined using a single drilling roadway for blasting and ore release. However, under conditions of well-developed joints and fractured ore bodies, well-constructed drilling roadways are prone to partial or complete collapse or damage due to mining activities, leading to the inability to mine normally, severe ore loss, and extremely low ore recovery rates for the ore block. This seriously affects the balance of production capacity and the smooth execution of the production schedule.

[0004] To address the problem of inability to mine normally due to the collapse of drilling tunnels, a proposed solution is to add new drilling tunnels perpendicular to the original tunnels in the mining area. Multiple new drilling tunnels can then be used for parallel blasting to release ore (with each tunnel's advance not exceeding one caving step). This method effectively solves the problem of high mining difficulty caused by the collapse of the original drilling tunnels. Once the original drilling tunnels are destroyed, the mining process for that block can be immediately stopped. The collapsed area is bypassed, and new drilling tunnels (the original tunnels) are excavated perpendicular to the ore body, then parallel to the original cross-cutting tunnels, and blasted to release ore. This method makes it possible to mine the ore block normally even when drilling tunnels collapse, achieving good mining results and significantly increasing the ore recovery rate. Simultaneously, the parallel blasting of multiple new drilling tunnels significantly reduces the ore dilution rate. However, at present, this new rock drilling tunnel layout is mostly designed based on experience. The specific number of new rock drilling tunnels and the spacing between adjacent new rock drilling tunnels are all based on the experience of mining construction engineers. There is no qualitative or quantitative method for scientific and precise calculation. In actual application, it is difficult to achieve the optimal mining effect. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of the aforementioned background technology and provide a bottomless, segmented, parallel ore discharge method.

[0006] The technical solution of this invention is as follows: a bottomless column-based segmented parallel ore-discharge method, wherein multiple first drilling tunnels are arranged along the strike of the ore body, adjacent first drilling tunnels are parallel to each other and the distance between the tunnels in the direction perpendicular to the strike of the ore body is m, the length of the ore body tunnel located between the vein tunnel and the cutting tunnel is L, and the width of the collapsed and recovered section located at the junction of the first drilling tunnel and the cutting tunnel along the strike of the ore body is L1.

[0007] The specific steps are as follows:

[0008] S1. When the access road of a certain first drilling roadway collapses, the width of the collapsed section along the direction of the ore body is determined to be L2. Multiple second drilling roadways are designed along the direction perpendicular to the direction of the ore body. The access distance M between adjacent second drilling roadways is determined according to the access distance m between adjacent first drilling roadways.

[0009] S2. Calculate the number of second drilling tunnels (n) based on the ore body access length L between the vein tunnel and the cutting tunnel, the width of the collapsed section L1, the width of the collapsed section L2, and the distance M between adjacent second drilling tunnels. Then, adjust the distance M between adjacent second drilling tunnels to obtain the correction value M based on the ore body access length L between the vein tunnel and the cutting tunnel, the width of the collapsed section L1, the width of the collapsed section L2, and the number n of second drilling tunnels. 修 ;

[0010] S3. Based on the number of second drilling tunnels n and the correction value M 修 A second drilling tunnel was set up between the vein tunnel and the cutting tunnel for ore body recovery.

[0011] According to the bottomless, segmented parallel ore discharge method provided in this application, in step S1, the method for determining the approach distance M of adjacent second drilling tunnels based on the approach distance m of adjacent first drilling tunnels includes: calculating the approach distance M of adjacent second drilling tunnels according to the following formula:

[0012] M = k * m

[0013] Where: M—the distance between the entrances of adjacent second drilling tunnels;

[0014] k—the approach spacing coefficient, with a value of 0.6 to 0.9, is a coefficient related to the degree of fragmentation of the surrounding rock structure and the block size of the ore body;

[0015] m — the distance between adjacent first rock drilling tunnels.

[0016] According to the bottomless, segmented parallel ore discharge method provided in this application, the approach spacing coefficient k is calculated according to the following formula:

[0017] k=ε*ζ

[0018] Where: k——route spacing coefficient, with a value of 0.6 to 0.9;

[0019] ε—Degree of fragmentation of the surrounding rock structure of the ore body, with a value ranging from 0.7 to 0.95;

[0020] ζ — Packing density, with a value of 0.8 to 0.95.

[0021] According to the bottomless, segmented parallel ore-discharging method provided in this application, the method for calculating the number n of the second drilling tunnels in step S2 includes:

[0022] The theoretical parameter t is calculated using the following formula:

[0023] t=(L-L1-L2) / M

[0024] Where: t — theoretical parameter;

[0025] L—Length of the ore body access route between the vein tunnel and the cutting tunnel;

[0026] L1 – Width of the collapsed and mined section;

[0027] L2 – Width of the collapsed section of the road access;

[0028] If t < 1, then no second drilling tunnel is arranged in the ore block, and n = 0; if t ≥ 1, then n is the integer after rounding t.

[0029] According to the bottomless, segmented, parallel ore-discharging method provided in this application, in step S2, the correction value M is obtained. 修 The methods include:

[0030] Calculate the correction value M using the following formula. 修 :

[0031] M 修 =(L-L1-L2) / n

[0032] Where: M 修 — Correction value for the spacing between adjacent second drilling tunnels;

[0033] L—Length of the ore body access route between the vein tunnel and the cutting tunnel;

[0034] L1 – Width of the collapsed and mined section;

[0035] L2 – Width of the collapsed section of the road access;

[0036] n — the number of second rock-drilling tunnels.

[0037] The advantages of this application are: 1. After the collapse of the first drilling tunnel, this application analyzes the ore body between the cross-cutting tunnel and the cutting tunnel, determines the number and spacing of the second drilling tunnel perpendicular to the first drilling tunnel, conducts a quantitative analysis of the second drilling tunnel, determines the precise design of the second drilling tunnel, which greatly facilitates the mining of the ore body, can effectively improve the ore mining efficiency, and can significantly reduce the ore dilution rate.

[0038] 2. This application can directly determine the approach spacing of the adjacent second rock drilling tunnel by using the approach spacing and approach spacing coefficient of the adjacent first rock drilling tunnel. There is a corresponding relationship between the approach spacing of the second rock drilling tunnel and the approach spacing of the second rock drilling tunnel. The approach spacing of the second rock drilling tunnel can be quickly determined by the calculation method of this application. The determination method is simple and quick.

[0039] 3. The access spacing coefficient in this application is determined based on the degree of fragmentation of the surrounding rock structure and the block size of the deposits. The degree of fragmentation of the surrounding rock structure and the block size of the deposits are parameters that truly reflect the properties of the ore body in the current area. The access spacing coefficient calculated using these parameters can accurately reflect the ore body structure and provide a good basis for the calculation of the second drilling tunnel.

[0040] 4. The method for calculating the number of second drilling tunnels in this application is extremely simple. The number of second drilling tunnels is calculated by the length of the ore body access road, the width of the collapsed mining section, the width of the access road collapse section, and the distance between the second drilling tunnel access road. The calculation method is simple, fully considers the ore body structure, effectively improves the ore body mining efficiency, and reduces the ore dilution rate.

[0041] 5. This application corrects the spacing between adjacent second drilling tunnels by calculating the number of second drilling tunnels, thus obtaining a corrected value for the spacing between adjacent second drilling tunnels. This correction method ensures that the spacing between the outermost second drilling tunnel and the adjacent through-cutting tunnel is M. 修 / 2, ensuring that the newly excavated second rock drilling tunnel, vein tunnel, and cutting tunnel are evenly distributed, thus guaranteeing sufficient stability.

[0042] The ore extraction method proposed in this application is applied to ore recovery after the collapse of the drilling tunnel approach. It can accurately calculate the spacing and number of subsequent newly added drilling tunnels, which greatly improves the efficiency of ore recovery and effectively reduces the ore dilution rate. It has great potential for widespread application. Attached Figure Description

[0043] Figure 1 : Schematic diagram of the layout of the first rock drilling tunnel in this application;

[0044] Figure 2 This application includes schematic diagrams of the collapsed mining section and the collapsed section of the access road;

[0045] Figure 3: Schematic diagram of the layout of the second rock drilling tunnel in this application;

[0046] Among them: 1—through-vein tunnel; 2—cutting tunnel; 3—first drilling tunnel; 4—second drilling tunnel; 5—collapsed and mined section; 6—collapsed access section. Detailed Implementation

[0047] Embodiments of the present invention are described in detail below, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain the present invention, and should not be construed as limiting the present invention.

[0048] In the description of this invention, it should be understood that the terms "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0049] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this invention, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0050] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0051] This application relates to a method for segmented parallel ore discharge without a bottom pillar, such as... Figures 1-3 As shown, the ore body strikes laterally, and multiple first drilling tunnels 3 are arranged along the strike of the ore body. Adjacent first drilling tunnels 3 are parallel to each other, and the distance between adjacent first drilling tunnels 3 is m. It also includes a through-cutting tunnel 1 and a cutting tunnel 2 perpendicular to the strike of the ore body. The through-cutting tunnel 1 and the cutting tunnel 2 are arranged laterally along the strike of the ore body. The bed surface and the cutting tunnel 2 intersect the first drilling tunnel 3 perpendicularly. The part between the through-cutting tunnel 1 and the cutting tunnel 2 is the ore body mining part. The ore body access length between the through-cutting tunnel 1 and the cutting tunnel 2 is L.

[0052] Mining is carried out on the side of the cutting tunnel 2 facing the vein tunnel 1. The width of the collapsed mining section 5 located at the junction of the first drilling tunnel 3 and the cutting tunnel 2 along the strike of the ore body is L1.

[0053] Specifically, the ore-discharging method of this application is carried out according to the following steps:

[0054] S1. When the access road of a certain first drilling tunnel 3 collapses, the width of the collapsed section 6 along the direction of the ore body is determined to be L2. Multiple second drilling tunnels 4 are designed along the direction perpendicular to the direction of the ore body. The access distance M between adjacent second drilling tunnels 4 is determined according to the access distance m between adjacent first drilling tunnels 3.

[0055] The second drilling tunnel 4 is laid out perpendicular to the first drilling tunnel 3, that is, it is laid out along the direction perpendicular to the ore body. The layout of the second drilling tunnel 4 is closely related to the structure of the first drilling tunnel 3. In addition, the layout of the second drilling tunnel 4 also needs to take into account the structure of the ore body between the vein tunnel 1 and the cutting tunnel 2.

[0056] The approach spacing of the adjacent second drilling tunnel 4 is set according to the approach spacing of the adjacent first drilling tunnel 3. Because the mining space between the vein tunnel 1 and the cutting tunnel 2 is limited, if the existing structure of the first drilling tunnel 3 is not considered and the approach spacing of the adjacent second drilling tunnel 4 is set arbitrarily, the problem of ore body collapse or the ore body mining may not meet the set requirements may occur. Therefore, the approach spacing of the second drilling tunnel 4 needs to be set with the original approach spacing of the first drilling tunnel 3 in mind. (Due to equipment factors such as drilling, charging, and occurrence, the cross-sectional dimensions of the first drilling tunnel 3 and the second drilling tunnel 4 in this application are the same, and the cross-sectional parameters are all the original design values ​​and are not changed.)

[0057] S2. Calculate the number of second drilling tunnels (n) based on the ore body access length L between the vein tunnel 1 and the cutting tunnel 2, the width L1 of the collapsed mining section 5, the width L2 of the collapsed section 6, and the access distance M between adjacent second drilling tunnels (n). Then, adjust the access distance M between adjacent second drilling tunnels based on the ore body access length L between the vein tunnel and the cutting tunnel, the width L1 of the collapsed mining section, the width L2 of the collapsed section, and the number of second drilling tunnels (n) to obtain the correction value M. 修 ;

[0058] After obtaining the access spacing of the adjacent second drilling tunnel 4, the number of second drilling tunnels 4 can be calculated based on the ore body structure between the cutting tunnel 2 and the vein tunnel 1. It is definitely impossible to lay out the second drilling tunnel 4 in the collapsed mining section 5 and the access collapse section 6. The second drilling tunnel 4 can only be laid out in the part between the collapsed mining section 5 and the access collapse section 6.

[0059] Considering the relative positional relationship between the outermost second drilling tunnel 4 and the adjacent vein tunnel and cutting tunnel, it is necessary to ensure that the outermost second drilling tunnel 4 and the adjacent vein tunnel and cutting tunnel are evenly distributed. The spacing should not be too large or too small, otherwise it will affect the recovery efficiency or stability. Therefore, it is necessary to correct the calculated spacing M between adjacent second drilling tunnels to ensure that the final arrangement between the second drilling tunnel 4 and the vein tunnel and cutting tunnel is uniform.

[0060] S3, based on the number n of the second rock drilling tunnel 4 and the correction value M 修 A second drilling tunnel 4 was constructed between the vein tunnel 1 and the cutting tunnel 2 for ore body mining.

[0061] In some embodiments of this application, step S1 above has been optimized. Specifically, in step S1, the method for determining the approach distance M of the adjacent second drilling tunnel 4 based on the approach distance m of the adjacent first drilling tunnel 3 includes: calculating the approach distance M of the adjacent second drilling tunnel 4 according to the following formula:

[0062] M = k * m

[0063] Where: M——the approach distance between adjacent second rock drilling tunnels 4;

[0064] k—the approach spacing coefficient, with a value of 0.6 to 0.9, is a coefficient related to the degree of fragmentation of the surrounding rock structure and the block size of the ore body;

[0065] m——the distance between adjacent first rock drilling tunnels 3.

[0066] Because the original structure of the first drilling tunnel 3 needs to be considered, as well as the condition of the ore body, it is particularly important to select an appropriate spacing between adjacent second drilling tunnels 4. Too wide a spacing between adjacent second drilling tunnels 4 will affect the ore body recovery efficiency, while too small a spacing between adjacent second drilling tunnels 4 will cause the ore body to collapse. In this embodiment, the spacing between adjacent second drilling tunnels 4 is calculated by combining the spacing between adjacent first drilling tunnels 3 and the characteristics of the ore body. The resulting spacing between adjacent second drilling tunnels 4 can avoid the problem of ore body collapse while ensuring the recovery efficiency.

[0067] In a further embodiment of this application, the aforementioned route spacing coefficient is calculated, and the specific route spacing coefficient k is calculated according to the following formula:

[0068] k=ε*ζ

[0069] Where: k——route spacing coefficient, with a value of 0.6 to 0.9;

[0070] ε—Degree of fragmentation of the surrounding rock structure of the ore body, relative to the degree of fragmentation of the surrounding rock of adjacent access routes, with a value of 0.7 to 0.95;

[0071] ζ—Accumulation block size, relative to normal ore collapse accumulation, with a value of 0.8 to 0.95.

[0072] The degree of fragmentation of the surrounding rock structure and the size of the deposited mass are the parameters that best reflect the properties of the ore body. The greater the degree of fragmentation of the surrounding rock structure and the smaller the size of the deposited mass, the more easily the ore body is likely to collapse. The greater the degree of fragmentation of the surrounding rock structure, the smaller the value; and the greater the size of the deposited mass, the larger the value.

[0073] In another embodiment of this application, step S2 described above is optimized. Specifically, in step S2, the method for calculating the number n of the second rock-drilling tunnels 4 includes:

[0074] The theoretical parameter t is calculated using the following formula:

[0075] t=(L-L1-L2) / M

[0076] Where: t — theoretical parameter;

[0077] L—Length of the ore body access route between vein tunnel 1 and cutting tunnel 2;

[0078] L1 – 5 width of the collapsed and mined section;

[0079] L2 – Width of the collapsed section of the road access road;

[0080] If t < 1, then the second drilling tunnel 4 will not be arranged in the ore block, and n = 0; if t ≥ 1, then n is the integer after rounding t.

[0081] For the ore body mining section between the vein tunnel 1 and the cutting tunnel 2, the collapsed mining section 5 and the access road collapse section 6 are areas where the second drilling tunnel 4 cannot be laid. Therefore, the second drilling tunnel 4 can only be laid in the ore body area between the collapsed mining section 5 and the access road collapse section 6. Since the access road spacing of adjacent second drilling tunnels 4 has been obtained, the ratio of the ore body section where the second drilling tunnel 4 can be laid to the access road spacing of adjacent second drilling tunnels 4 is used as a theoretical parameter. The theoretical parameter may not be an integer, but the number of second drilling tunnels 4 is definitely an integer. The number of second drilling tunnels 4 can be obtained by rounding t.

[0082] In a further embodiment of this application, step S2 described above is further optimized. Specifically, in step S2, the correction value M is obtained. 修 The methods include:

[0083] Calculate the correction value M using the following formula. 修 :

[0084] M 修=(L-L1-L2) / n

[0085] Where: M 修 — Correction value for the spacing between adjacent second drilling tunnels;

[0086] L—Length of the ore body access route between the vein tunnel and the cutting tunnel;

[0087] L1 – Width of the collapsed and mined section;

[0088] L2 – Width of the collapsed section of the road access;

[0089] n — the number of second rock-drilling tunnels.

[0090] By correcting the spacing M between adjacent second drilling tunnels, a corrected value for the spacing between adjacent second drilling tunnels is obtained. This correction method ensures that the spacing M between the outermost second drilling tunnel and the adjacent through-cutting tunnel is constant. 修 / 2, ensuring that the newly excavated second rock drilling tunnel, vein tunnel, and cutting tunnel are evenly distributed, thus guaranteeing sufficient stability.

[0091] In this application, the approach spacing of adjacent first drilling tunnels 3 refers to the distance between the centerlines of adjacent first drilling tunnels 3 along the direction perpendicular to the ore body; the approach spacing of adjacent second drilling tunnels 4 refers to the distance between the centerlines of adjacent second drilling tunnels 4 along the direction of the ore body; the ore body approach length between vein tunnel 1 and cutting tunnel 2 refers to the distance between the adjacent sides of vein tunnel 1 and cutting tunnel 2 along the direction of the ore body; the width of the approach collapse section 6 along the direction of the ore body refers to the distance between the two sides of the approach collapse section 6 along the direction of the ore body; and the width of the collapsed and mined section 5 refers to the distance between the two sides of the collapsed and mined section 5 along the direction of the ore body.

[0092] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as claimed. The scope of protection of this invention is defined by the appended claims and their equivalents.

Claims

1. A method for parallel ore discharge without pillars, comprising multiple first drilling tunnels arranged along the strike of the ore body, wherein adjacent first drilling tunnels are parallel to each other and the distance between them in the direction perpendicular to the strike of the ore body is m, the length of the ore body tunnel located between the vein tunnel and the cutting tunnel is L, and the width of the collapsed and recovered section located at the junction of the first drilling tunnel and the cutting tunnel is L1. Its features are: Follow these steps: S1. When the access road of a certain first drilling roadway collapses, the width of the collapsed section along the direction of the ore body is determined to be L2. Multiple second drilling roadways are designed along the direction perpendicular to the direction of the ore body. The access distance M between adjacent second drilling roadways is determined according to the access distance m between adjacent first drilling roadways. S2. Calculate the number of second drilling tunnels (n) based on the ore body access length L between the vein tunnel and the cutting tunnel, the width of the collapsed section L1, the width of the collapsed section L2, and the distance M between adjacent second drilling tunnels. Then, adjust the distance M between adjacent second drilling tunnels to obtain the correction value M based on the ore body access length L between the vein tunnel and the cutting tunnel, the width of the collapsed section L1, the width of the collapsed section L2, and the number n of second drilling tunnels. 修 ; S3. Based on the number of second drilling tunnels n and the correction value M 修 A second drilling tunnel was set up between the vein tunnel and the cutting tunnel for ore body recovery.

2. The method for segmented parallel ore discharge without a bottom pillar as described in claim 1, characterized in that: In step S1, the method for determining the approach distance M of an adjacent second rock drilling tunnel based on the approach distance m of an adjacent first rock drilling tunnel includes: calculating the approach distance M of an adjacent second rock drilling tunnel according to the following formula: M=k*m Where: M—the distance between the entrances of adjacent second drilling tunnels; k—the route spacing coefficient, with a value of 0.6~0.9, is a coefficient related to the degree of fragmentation of the surrounding rock structure and the block size of the ore body; m — the distance between adjacent first rock drilling tunnels.

3. The method for segmented parallel ore discharge without a bottom pillar as described in claim 2, characterized in that: The route spacing coefficient k is calculated according to the following formula: k=ε*ζ Where: k——route spacing coefficient, with a value of 0.6~0.9; ε—Degree of fragmentation of the surrounding rock structure of the ore body, with a value ranging from 0.7 to 0.95; ζ — Packing density, with a value of 0.8 to 0.

95.

4. The method for segmented parallel ore discharge without a bottom pillar as described in claim 1, characterized in that: In step S2, the method for calculating the number n of the second rock drilling tunnels includes: The theoretical parameter t is calculated using the following formula: t = (L - L1 - L2) / M Where: t — theoretical parameter; L—Length of the ore body access route between the vein tunnel and the cutting tunnel; L1 – Width of the collapsed and mined section; L2 – Width of the collapsed section of the road access; If t < 1, then no second drilling tunnel is arranged in the ore block, and n = 0; if t ≥ 1, then n is the integer after rounding t.

5. The method for segmented parallel ore discharge without a bottom pillar as described in claim 1, characterized in that: In step S2, the correction value M is obtained. 修 The methods include: Calculate the correction value M using the following formula. 修 : M 修 =(L-L1-L2) / n Where: M 修 — Correction value for the spacing between adjacent second drilling tunnels; L—Length of the ore body access route between the vein tunnel and the cutting tunnel; L1 – Width of the collapsed and mined section; L2 – Width of the collapsed section of the road access; n — the number of second rock-drilling tunnels.

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