A method for calculating the height of caving zone and fracture zone in gob-side entry retaining

Abstract

The present application belongs to the field of coal mine roadway surrounding rock control, and aims to solve the problem that the roof three-zone observation is restricted by time and space during the working face mining process, and the specific height of the caving zone and the fracture zone cannot be clarified. A kind of calculation method for caving zone and fracture zone height of gob-side entry retaining is provided, by dividing one section in the gob of gob-side entry retaining into A region, B region, C region, D region and E region, arranging pressure sensors, and combining with the advancing process of hydraulic support, the pressure change is monitored in real time, based on the area, value of the pressure sensor in B region, the density of the broken and swelled gangue rock in B region, the caving zone height is obtained; based on the area, value of the pressure sensor in D region, the density of the broken and swelled gangue rock in D region and the caving zone height, the fracture zone height is obtained. The method can evaluate the roof caving and fracture development of the goaf.

Description

Technical Field

[0001] This invention belongs to the field of coal mine roadway surrounding rock control, specifically involving a method for calculating the height of the caving zone and fracture zone in roadway retention along the goaf. Background Technology

[0002] In coal mining methods, open-pit mining accounts for only 6% to 7% of the output of key coal mines, with the remainder being underground mining. Underground mining widely employs the wall-mounted system, accounting for over 90% of underground mining output. Coal mines require a minimum recovery rate of 75% for thick coal seams, 80% for medium-thick seams, and 85% for thin coal seams. However, many mines fail to meet these requirements, with large coal pillars in certain sections being a significant reason for low recovery rates. Furthermore, coal resources are non-renewable, and leaving coal pillars represents a substantial waste of resources. Currently, there is a strong push for qualified coal mining enterprises to implement goaf-side roadway retention, with the 110 method referring to mining one working face while only excavating one roadway, retaining zero coal pillars. This technology reduces roadway excavation and maximizes coal pillar recovery.

[0003] However, during the application and promotion of roadway retention, the observation of the three zones of the roof during the mining process in coal mines is limited by time, space and technology, making it impossible to monitor in real time and clarify the specific height of the caving zone and fracture zone, which brings many inconveniences to the adjustment of roadway retention technology. Summary of the Invention

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

[0005] This invention employs the following technical solution: a method for calculating the height of the caving zone and fracture zone in a goaf-retaining roadway, comprising the following steps: dividing a section of the goaf area in the goaf-retaining roadway into region A, region B, region C, region D, and region E; region E, region D, region C, region B, and region A are sequentially arranged along the direction of the hydraulic support's advancement from the initial mining position, and pressure sensors are reserved at the bottom plate of the aforementioned regions; controlling the hydraulic support to advance forward from the initial mining position, the direct roof of region E, which has been pre-fractured by blasting, collapses with the movement of the hydraulic support, and simultaneously, with the continuous advancement of the hydraulic support... As the hydraulic support advances, the overlying roof cantilever in area E increases, bending and rotating towards the mining side. Upon reaching its limit, the roof fractures, creating the initial pressure. Continuing to control the hydraulic support's advance, the overlying roof in area E continues to bend and fracture, creating periodic pressure. At this point, the pressure sensor readings stabilize. The caving zone height is then determined based on the area and pressure values ​​of the pressure sensor in area B, the density of the fractured rock in area B, and the caving zone height in area B. Similarly, the fracture zone height is determined based on the area and pressure values ​​of the pressure sensor in area D, the density of the fractured rock in area D, and the caving zone height in area B.

[0006] Preferably, after the formation of the periodic pressure, region A is affected by the directional pre-splitting roof cutting line, forming a triangular caving zone. The overlying strata of the triangular caving zone are affected by the rotation and subsidence of the roof strata, and the pressure increases as the mining face advances. This region is a transition zone. Region B is the region for calculating the height of the caving zone. Since the basic roof is in a cantilever state, a cantilever beam will form in the old roof over the caving zone if the overlying strata are not affected by the structure. In region B, the goaf is filled with broken gangue. Region C is the transition zone between the cantilever beam and the fracture zone of the old roof. The pressure rises in a curve and gradually stabilizes in region D. Region D is the region for calculating the fracture zone. Since the overlying strata are affected by the caving zone and the fracture zone, a layer of cantilever beam will also form above the fracture zone. Region D provides the spatial basis for calculating the fracture zone.

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

[0008] Preferably, the formula for calculating the height h of the landslide zone in area B is:

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

[0010] Preferably, the formula for calculating the height H of the landslide zone in region 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 region D, ρ2 is the density of the crushed gangue rock in region D, and g is the acceleration due to gravity.

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

[0013] H' = Hh.

[0014] Preferably, multiple sets of pressure sensors are spaced apart at the base plate of areas A, B, C, D, and E along the advancing direction of the hydraulic support, and the pressure sensors are connected to an external control terminal via signal lines.

[0015] Compared with the prior art, the beneficial effects of the present invention are:

[0016] This method involves dividing the area, deploying pressure sensors, and monitoring pressure changes in real time during the advancement of hydraulic supports. The data from the pressure sensors is then used to calculate the height of the collapse zone and fracture zone. This method can effectively assess the roof collapse and fracture development in goaf areas, providing data support for mine safety.

[0017] The heights of the collapse zone and fracture zone are obtained through simple calculations, providing a theoretical basis for the control of surrounding rock pressure in the goaf-retaining tunnel of the 110 method. Compared with the original method of drilling and geophysical exploration to detect the three zones of the roof, this method is simple, easy to implement and low in cost. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

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

[0020] Figure 2 This is a side view of the pressure sensor mounting location in an embodiment of the present invention;

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

[0022] In the diagram: 1-Goaf section; 2-Goaf area; 3-Solid coal; 4-Pressure sensor; 5-Hydraulic support; 6-Signal line. Detailed Implementation

[0023] The technical solutions of the embodiments of the present invention will be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other implementation methods obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0024] It should be noted that the structures, proportions, sizes, etc., shown in the accompanying drawings of this specification are only for the purpose of assisting those skilled in the art in understanding and reading the content disclosed in the specification, and are not intended to limit the conditions under which the present invention can be implemented. Therefore, they have no substantial technical significance. Any modifications to the structure, changes in the proportional relationships, or adjustments to the size, without affecting the effects and objectives that the present invention can produce, should fall within the scope of the technical content disclosed in 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] This invention provides an embodiment:

[0026] This invention primarily addresses the difficulty in observing the three zones during the goaf retention process using the 110 method in various coal mining faces. It mainly utilizes the space in the retained section. Since there is no filling material on the goaf side of the 110 method goaf retention, it provides space for the installation and wiring of goaf pressure sensors. Pressure sensors 4 can be pre-reserved in front of the working face. Utilizing the principle of goaf surrounding rock collapse, the height of the collapse zone and fracture zone can be obtained through simple calculations, providing a theoretical basis for the pressure control of the surrounding rock in the 110 method goaf retention.

[0027] like Figures 1 to 3 As shown, a method for calculating the height of the caving zone and fracture zone in a goaf-retention tunnel includes the following steps:

[0028] One section of the goaf along the goaf is divided into area A, area B, area C, area D and area E. Areas E, D, C, B and A are set up sequentially along the direction of the hydraulic support advancing from the initial mining position. Multiple sets of pressure sensors are set at intervals along the direction of the hydraulic support advancing at the bottom plate of area A, B, C, D and E, and the pressure sensors are connected to an external control terminal through signal lines.

[0029] The hydraulic support is advanced from the initial mining position. Due to the "110 method" which pre-fractures the immediate roof with blasting, the pre-fractured immediate roof at the upper end of area E collapses as the hydraulic support moves. Combined with the principle of surrounding rock collapse in the goaf, the overlying basic roof remains in a cantilever beam state during the initial mining process and will not break. Simultaneously, as the hydraulic support continues to advance, the cantilever of the overlying basic roof in area E increases, rotating and bending towards the mining side. When it reaches its limit, the basic roof breaks, forming the initial pressure.

[0030] Continue controlling the hydraulic support advance. The overlying basic roof in area E continues to bend and fracture, repeating the aforementioned process to form periodic pressure. After periodic pressure is formed, the pressure sensor pressure tends to stabilize. In this embodiment, after periodic pressure is formed, area A is affected by the directional pre-splitting roof cutting line, forming a triangular caving zone. The overlying strata of the triangular caving zone are affected by the rotation and subsidence of the roof strata, and the pressure increases as the mining face advances. This area is a transition zone. Area B is the area for calculating the height of the caving zone. Since the basic roof is in a cantilever state, a cantilever beam will form in the old roof above the caving zone if the overlying strata are not affected by the structure. In area B, the goaf is filled with broken gangue. Area C is the transition zone between the cantilever beam and the fracture zone of the old roof. 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 strata are affected by the caving zone and the fracture zone, a layer of cantilever beam will also form on the upper layer of the fracture zone. Area D provides a spatial basis for calculating the fracture zone.

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

[0032] The height of the collapse zone is determined based on the area and value of the pressure sensor in region B, and the density of the crushed gangue rock.

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

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

[0035] Since the main roof of region B is in a cantilevered state, pressure sensor 4 in region B only measures the weight of the rock after it collapses at the height of the caving zone. Therefore, by using F1 = m1g, we can derive m1 = F1 / g, where m1 is the mass of the rock after it collapses at the height of the caving zone. By taking core samples, we can measure the density ρ1 of the crushed rock in region B, and thus determine the volume V1 of the overlying rock pressing on pressure sensor 4 in region B. Given the area S1 of the pressure sensor, we can calculate the height of the caving zone, h = V1 / S1.

[0036] Region C is the transition zone between the cantilever beam and the main fracture zone. The pressure rises in a certain curve, which is a transition zone and has little reference value for calculating the fracture zone.

[0037] The fracture zone height is determined based on the area and value of the pressure sensor in region D, the density of the immediate roof rock, and the height of the caving zone.

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

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

[0040] H' = Hh.

[0041] This invention primarily addresses the challenges of using the 110 method for roadway retention in coal mines. In this process, the roadway is left unfilled, and the loose rock mass formed after the roof collapses creates an independent space. The forces exerted by the surrounding rocks are negligible, eliminating the influence of tectonic stress on the calculation results. Furthermore, the absence of filler beside the roadway, with only ventilation ducts and U-shaped steel between the goaf and the roadway section, facilitates sensor placement. Utilizing this advantage, pressure sensors are pre-installed in the floor. Using the theory of rock strata collapse and the short-arm beam theory, the vertical distances between the collapse zone and fracture zone in the working face of the coal mine can be determined.

[0042] The above description is merely a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A method for calculating the height of caving zones and fracture zones in roadway retaining structures, characterized in that, Includes the following steps: One section of the goaf area along the goaf is divided into area A, area B, area C, area D and area E. Areas E, D, C, B and A are set up sequentially along the direction of the hydraulic support advancing from the initial mining position, and pressure sensors are reserved at the bottom plate of the above areas. As the hydraulic support is advanced from the initial mining position, the direct roof of the upper part of area E, which has been pre-fractured by blasting, collapses as the hydraulic support moves. At the same time, as the hydraulic support continues to advance, the overlying basic roof cantilever in area E increases and bends back towards the mining side. When it reaches its limit, the basic roof breaks, forming the initial pressure. Continue to control the hydraulic support to advance. The overlying main roof at area E continues to bend and break, forming periodic pressure. At this time, the pressure sensor pressure is stable. At this point, the height of the collapse zone is determined based on the area and pressure value of the pressure sensor in region B, the density of the crushed gangue rock in region B, and the height of the fracture zone is determined based on the area and pressure value of the pressure sensor in region D, the density of the crushed gangue rock in region D, and the height of the collapse zone in region B.

2. The method for calculating the height of the caving zone and fracture zone along the goaf as described in claim 1, characterized in that: After the formation of the periodic pressure, the A area is affected by the directional pre-splitting and top-cutting line, forming a triangular caving zone. The overlying strata of the triangular caving zone are affected by the rotation and subsidence of the roof strata, and the pressure increases as the mining face advances. This area is a transition zone. Area B is the area for calculating the height of the collapse zone. Since the basic roof is in a cantilever state, a cantilever beam will form in the old roof above the collapse zone if the overlying strata are not affected by the structure. The goaf area is filled with gangue fragments in Area B. Region C is the transition zone between the cantilever beam and the old roof fracture zone, where the pressure increases in a curve, and gradually stabilizes in region D. Region D is the calculation area of ​​the fracture zone. Due to the combined effect of the overlying rock strata and the fracture zone, a cantilever beam will also form on the upper layer of the fracture zone. Region D provides the spatial basis for calculating the fracture zone.

3. The method for calculating the height of the caving zone and fracture zone along the goaf as described in claim 1, characterized in that: The density of the crushed gangue rock was determined by core sampling.

4. The method for calculating the height of the caving zone and fracture zone along the goaf as described in claim 3, characterized in that: The formula for calculating the height h of the landslide zone in area B is: h = F1 / gρ1S1, where S1 is the area of ​​the pressure sensor in region B, F1 is the average pressure of the pressure sensor in region B, ρ1 is the density of the crushed gangue rock in region B, and g is the acceleration due to gravity.

5. The method for calculating the height of the caving zone and fracture zone along the goaf as described in claim 4, characterized in that: The formula for calculating the height H of the caving 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 region D, ρ2 is the density of the crushed gangue rock in region D, and g is the acceleration due to gravity. The formula for calculating the fracture zone height H' in region D is: H' = Hh.

6. The method for calculating the height of the caving zone and fracture zone along the goaf as described in claim 1, characterized in that: Multiple pressure sensors are spaced apart at the base plate in areas A, B, C, D, and E along the thrust direction of the hydraulic support, and the pressure sensors are connected to an external control terminal via signal lines.

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