Gob-side entry retaining caving zone and fissure zone height calculation method

Abstract

The invention belongs to the field of coal mine roadway surrounding rock control, and aims to solve the problem that the specific heights of a caving zone and a fissure zone cannot be clarified due to the fact that roof three-zone observation is limited by time and space in the working face stoping process of a coal mine. According to the gob-side entry retaining caving zone and fissure zone height calculation method, one section in a gob-side entry retaining goaf is divided into an area A, an area B, an area C, an area D and an area E, pressure sensors are arranged, and pressure changes are monitored in real time in combination with the propelling process of a hydraulic support; the caving zone height is obtained based on the area and the numerical value of the pressure sensor in the area B and the density of the crushed and expanded gangue rocks in the area B; and obtaining the height of the fissure zone based on the area and numerical value of the pressure sensor in the D region, the density of the crushed and expanded gangue rock in the D region and the height of the caving zone. The method can evaluate the roof caving and fracture development conditions of the goaf.

Description

Technical Field

[0001] The present invention belongs to the field of surrounding rock control of coal mine tunnels, and in particular relates to a method for calculating the height of a collapsed zone and a fracture zone in a gob-side tunnel retaining system. Background Art

[0002] Among coal mining methods, open-pit mining accounts for only 6% to 7% of output at key coal mines, with the remainder being underground. Within underground mining, wall-type mining is widely used, accounting for over 90% of underground production. Coal mines require a recovery rate of at least 75% for thick coal seams, 80% for medium-thick coal seams, and 85% for thin coal seams. However, many mines fail to meet this requirement, with large coal pillars in certain sections being a major contributing factor to low recovery rates. Furthermore, coal resources are non-renewable, and leaving coal pillars is a significant waste of resources. Currently, coal mining enterprises with the necessary conditions are strongly encouraged to implement gob-side entry retention. The 110 method involves mining one working face, excavating only one drift, and retaining zero coal pillars. This technique reduces tunneling and maximizes the recovery of coal pillars.

[0003] However, in the process of promoting the application of goaf-side tunnel retention, the observation of the three zones of the roof during the working face mining process in coal mines is subject to time, space and technical limitations, and real-time monitoring is impossible, and the specific heights of the collapsed zone and the fracture zone cannot be clarified, which brings many inconveniences to the adjustment of the tunnel retention technology. Summary of the Invention

[0004] In order to solve at least one of the above-mentioned technical problems existing in the prior art, the present invention provides a method for calculating the height of the collapsed zone and the fracture zone of the gob-side entry.

[0005] The present invention is implemented by the following technical solution: a method for calculating the height of the collapsed zone and the fracture zone of the goaf-side tunnel retaining tunnel, comprising the following steps: dividing a section of the goaf-side tunnel retaining tunnel into area A, area B, area C, area D and area E, wherein the area E, area D, area C, area B and area A are arranged in sequence along the direction in which the hydraulic support advances from the initial mining position, and a pressure sensor is reserved at the bottom plate of the above-mentioned area; the hydraulic support is controlled to advance forward from the initial mining position, and the direct top of the upper end of the E area pre-cracked by blasting collapses with the movement of the hydraulic support, and at the same time, as the hydraulic support continues to move, the pressure sensor is set at the bottom plate of the above-mentioned area. As the hydraulic support is advanced, the cantilever of the overlying basic roof in area E increases and bends toward the mining side. When it reaches the limit, the basic roof breaks, forming the initial pressure. The hydraulic support is continued to be controlled to advance, and the overlying basic roof in area E continues to bend and break, forming a periodic pressure. At this time, the pressure of the pressure sensor is stable. At this time, the height of the collapse zone is obtained based on the area and pressure value of the pressure sensor in area B and the density of the broken and swelling waste rock in area B. The height of the fracture zone is obtained based on the area and pressure value of the pressure sensor in area D, the density of the broken and swelling waste rock in area D and the height of the collapse zone in area B.

[0006] Preferably, after the formation of cyclic pressure, the A area is affected by the directional pre-crack cutting line to form a triangular collapse zone. The overlying rock layer in the triangular collapse zone is affected by the rotation and sinking of the roof rock layer. The pressure increases as the mining working face advances forward. This area is a transition zone; the B area is the area for calculating the height of the collapse zone. Since the basic top is in a cantilever state, when the overlying rock layer is not affected by the structure, a cantilever beam will be formed in the old top overlying the collapse zone, and the waste rock in area B will fill the goaf; area C is the transition zone between the cantilever beam and the old top fracture zone. The pressure rises in a curve and gradually stabilizes in area D; area D is the area for calculating the fracture zone. Since the overlying rock layer is affected by the collapse zone and the fracture zone, a layer of cantilever beam will also be formed on the upper layer of the fracture zone. Area D provides a spatial basis for calculating the fracture zone.

[0007] Preferably, the density of the crushed gangue rock is measured by core sampling.

[0008] Preferably, the calculation formula for the collapse zone height h in area B is:

[0009] h=F1 / gρ1S1, where S1 is the area of the pressure sensor in area B, F1 is the average pressure of the pressure sensor in area B, ρ1 is the density of the crushed and expanded waste rock in area B, and g is the acceleration of gravity.

[0010] Preferably, the calculation formula for the height H of the collapse zone in area D is:

[0011] H = F2 / gρ2S2, where S2 is the area of the pressure sensor, F2 is the average pressure of the pressure sensor in area D, ρ2 is the density of the crushed and expanded waste rock in area D, and g is the acceleration of gravity;

[0012] The calculation formula for the fracture zone height H' in region D is:

[0013] H'=Hh.

[0014] Preferably, multiple groups of pressure sensors are arranged at intervals on the bottom plates of areas A, B, C, D and E along the propulsion direction of the hydraulic support, and the pressure sensors are connected to the external control terminal through signal lines.

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

[0016] This method divides the area, deploys pressure sensors, and integrates the hydraulic support's advancement process to monitor pressure changes in real time. The data from the pressure sensors is then used to calculate the heights of the collapsed and fractured zones. This method can effectively assess roof collapse and fracture development in goaf areas, providing data support for mine safety.

[0017] The heights of the collapse zone and the fracture zone are obtained through simple calculations, providing a theoretical basis for controlling the surrounding rock pressure of the goaf-side tunnel retained in the 110 construction method. Compared with the original method of drilling and geophysical exploration of the three zones of the roof, this method is simple, easy and low-cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0019] Figure 1 is a top view of the installation position of the pressure sensor in an embodiment of the present invention;

[0020] Figure 2 is a side view of the installation position of the pressure sensor in an embodiment of the present invention;

[0021] Figure 3 Schematic diagram of the pressure at the five regions A, B, C, D, and E in an embodiment of the present invention.

[0022] In the figure: 1- gob-side entry section; 2- goaf; 3- solid coal; 4- pressure sensor; 5- hydraulic support; 6- signal line. DETAILED DESCRIPTION

[0023] The technical solutions in the embodiments of the present invention are clearly and completely described in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. All other implementations derived by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts are within the scope of protection of the present invention.

[0024] It should be noted that the structures, proportions, sizes, etc. illustrated in the drawings of this specification are only used to match the contents disclosed in the specification for people familiar with this technology to understand and read, and are not used to limit the conditions under which the present invention can be implemented. Therefore, they have no substantive technical significance. Any structural modification, change in proportional relationship or adjustment of size should fall within the scope of the technical content disclosed in the present invention without affecting the efficacy and purpose that can be achieved by the present invention. It should be noted that in this specification, relational terms such as first and second are only used to distinguish one entity from several other entities, and do not necessarily require or imply any actual relationship or order between these entities.

[0025] The present invention provides an embodiment:

[0026] The present invention mainly solves the problem of difficult observation of the three zones in the process of retaining lanes along the goaf using the 110 method at each coal mining face in a coal mine. It mainly utilizes the space of the lane retaining section. There is no filling body on the goaf side of the 110 method, which provides space for the installation and wiring of the goaf pressure sensor. The pressure sensor 4 can be reserved in advance in front of the working face. The principle of rock collapse in the goaf is used to obtain the height of the collapse zone and the fracture zone through simple calculation, which provides a theoretical basis for the control of the surrounding rock pressure of the 110 method.

[0027] like Figures 1 to 3 As shown, a method for calculating the height of the collapsed zone and the fracture zone of the gob-side entry retaining includes the following steps:

[0028] A section of the goaf area along the goaf-retaining lane is divided into area A, area B, area C, area D and area E. The area E, area D, area C, area B and area A are arranged in sequence along the direction in which the hydraulic support advances from the initial mining position. Multiple groups of pressure sensors are arranged at intervals on the bottom plates of area A, area B, area C, area D and area E along the advancement direction of the hydraulic support, and the pressure sensors are connected to the external control terminal through signal lines.

[0029] The hydraulic support is controlled to advance forward from the initial mining position. Since the "110 method" pre-cracks the direct roof with blasting in advance, the direct roof at the upper end of area E, which has been pre-cracked by blasting, collapses with the movement of the hydraulic support. Combined with the principle of surrounding rock collapse in the goaf, the overlying basic roof remains in a cantilever beam state and will not break during the initial mining process. At the same time, as the hydraulic support continues to advance, the overlying basic roof in area E cantilever increases, turning and bending toward the mining side. When it reaches its limit, the basic roof breaks, forming the initial pressure.

[0030] The hydraulic support continues to be controlled to advance, and the overlying basic roof in area E continues to bend and fracture. The above process is repeated to form a cyclic pressure. After the cyclic pressure is formed, the pressure of the pressure sensor tends to be stable. In this embodiment, after the cyclic pressure is formed, the area A is affected by the directional pre-splitting top cutting line, forming a triangular collapse zone. The overlying rock strata in the triangular collapse zone are affected by the rotation and sinking of the roof rock strata. The pressure increases as the mining working face advances forward. This area is the transition zone; the area B is the area where the collapse zone height is calculated. Since the basic roof is in a cantilever state, when the overlying rock strata are not affected by the structure, a cantilever beam will be formed in the old roof overlying the collapse zone. The waste rock in area B will fill the goaf; the area C is the transition zone between the cantilever beam and the old roof fracture zone. The pressure rises in a curve and gradually stabilizes in area D; the area D is the area where the fracture zone is calculated. Since the overlying rock strata are affected by the collapse zone and the fracture zone, a layer of cantilever beam will also be formed in the upper layer of the fracture zone. Area D provides the spatial basis for the calculation of the fracture zone.

[0031] The height of the collapse zone and the fracture zone can be obtained through theoretical calculation. The specific calculation method is as follows:

[0032] The height of the collapse zone is obtained based on the area, value and density of the pressure sensor in area B;

[0033] The calculation formula for the height h of the collapse zone in area B is:

[0034] h=F1 / gρ1S1, where S1 is the area of the pressure sensor in area B, F1 is the average pressure of the pressure sensor in area B, ρ1 is the density of the crushed and expanded waste rock in area B, and g is the acceleration of gravity.

[0035] Because the base roof in region B is in a cantilevered state, pressure sensor 4 in region B only measures the weight of the rock at the collapse zone after collapse. Therefore, using F1 = m1g, we can derive m1 = F1 / g, where m1 is the mass of the rock at the collapse zone after collapse. Coring can measure the density ρ1 of the crushed and expanded waste rock in region B, thereby determining the volume V1 of the overlying rock pressing on pressure sensor 4 in region B. Given the pressure sensor area S1, the collapse zone height h = V1 / S1 can be calculated.

[0036] In the transition zone between area C and the cantilever beam and basic top fracture, the pressure rises in a certain curve. It is a transition zone and has little reference value for calculating the fracture zone.

[0037] The height of the fracture zone is obtained based on the area and value of the pressure sensor in area D, the density of the immediate top rock, and the height of the collapse zone.

[0038] The calculation formula for the collapse zone height H in area D is: H = F2 / gρ2S2, where S2 is the area of the pressure sensor, F2 is the average pressure of the pressure sensor in area D, ρ2 is the density of the crushed and expanded waste rock in area D, and g is the acceleration of gravity. The specific calculation method is similar to the calculation method for the collapse zone height h in area B.

[0039] The calculation formula for the fracture zone height H' in region D is:

[0040] H'=Hh.

[0041] The present invention mainly solves the problem that after the coal mine adopts the 110 method of retaining a lane along the goaf, the space in the later stage of retaining the lane is utilized, and there is no filling body in the retaining lane. After the roof collapses, the loose rock mass forms an independent space body, and the force exerted by the surrounding rocks can be basically ignored, eliminating the influence of the structural stress on the calculation results. In addition, there is no filling body beside the lane, and there are only air duct cloth and U-shaped steel in the goaf and the retaining lane section, which is convenient for laying sensors. Taking advantage of this convenient condition, pressure sensors are buried in the bottom plate in advance, and the vertical distance of the collapse zone and the fracture zone of the working face of the coal mine can be determined by using the rock formation collapse theory and the short arm beam theory calculation.

[0042] The foregoing description is merely a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any modifications or substitutions that can be readily conceived by a person skilled in the art within the technical scope disclosed herein should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be based on the scope of protection of the claims.

Claims

1. A method for calculating the height of collapse zone and fracture zone of gob-side entry retention, characterized in that: The following steps are involved: A section of the gob-side entry retaining goaf is divided into area A, area B, area C, area D and area E. The areas E, D, C, B and A are arranged in sequence along the direction in which the hydraulic supports are advanced from the initial mining position, and pressure sensors are reserved on the bottom plates of the above areas; The hydraulic support is controlled to advance forward from the initial mining position. The direct roof at the upper end of area E, which has been pre-cracked by blasting, collapses as the hydraulic support moves. At the same time, as the hydraulic support continues to advance, the overlying basic roof cantilever at area E increases and bends toward the mining side. When it reaches the limit, the basic roof breaks, forming the initial pressure. Continue to control the advancement of the hydraulic support. The overlying base roof in area E continues to bend and break, forming a cyclic pressure. At this time, the pressure of the pressure sensor is stable. At this time, the height of the collapse zone is obtained based on the area, pressure value, and density of the crushed and expanded gangue rock in area B of the pressure sensor in area B; the height of the fracture zone is obtained based on the area, pressure value, and density of the crushed and expanded gangue rock in area D of the pressure sensor in area D and the height of the collapse zone in area B.

2. The method for calculating the height of the collapsed zone and the fracture zone of the gob-side entry retaining according to claim 1 is characterized in that: After the formation of periodic pressure, the A area is affected by the directional pre-splitting top cutting line, forming a triangular collapse zone. The overlying rock layer in the triangular collapse zone is affected by the rotation and sinking of the roof rock layer. The pressure increases as the mining working face advances forward. This area is the transition zone. The B area is the area for calculating the height of the collapse zone. Since the basic roof is in a cantilever state, when the overlying rock layer is not affected by the structure, a cantilever beam will be formed in the old roof above the collapse zone, and the waste rock in the B area will fill the goaf. The C region is the fracture transition zone between the cantilever beam and the old top fracture zone, where the pressure rises in a curve and gradually stabilizes in the D region; The D area is the area for calculating the fracture zone. Since the overlying rock strata are affected by the collapse zone and the fracture zone, a layer of cantilever beams will also be formed on the upper layer of the fracture zone. The D area provides a spatial basis for calculating the fracture zone.

3. The method for calculating the height of the collapsed zone and the fracture zone of the gob-side entry retaining according to claim 1 is characterized in that: The density of the crushed gangue rock is measured by core sampling.

4. The method for calculating the height of the collapsed zone and the fracture zone of the gob-side entry retaining according to claim 3 is characterized in that: The calculation formula for the height h of the collapse zone in area B is: h=F1 / gρ1S1, where S1 is the area of the pressure sensor in area B, F1 is the average pressure of the pressure sensor in area B, ρ1 is the density of the crushed and expanded waste rock in area B, and g is the acceleration of gravity.

5. The method for calculating the height of the collapsed zone and the fracture zone of the gob-side entry retaining according to claim 4 is characterized in that: The calculation formula for the height H of the collapse zone in area D is: H = F2 / gρ2S2, where S2 is the area of the pressure sensor, F2 is the average pressure of the pressure sensor in area D, ρ2 is the density of the crushed and expanded waste rock in area D, and g is the acceleration of gravity; The calculation formula for the fracture zone height H' in region D is: H'=Hh.

6. The method for calculating the height of the collapsed zone and the fracture zone of the gob-side entry retaining according to claim 1 is characterized in that: A plurality of groups of pressure sensors are arranged at intervals on the bottom plates of areas A, B, C, D and E along the propulsion direction of the hydraulic support, and the pressure sensors are connected to the external control terminal through signal lines.

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