Deep coal mine key layer discrimination method based on geological exploration hole multi-information mutual feedback

Abstract

The invention discloses a deep coal mine key layer discrimination method based on geological exploration hole multi-information mutual feedback, which comprises the following steps: collecting rock cores of rock layers by constructing geological exploration holes, and carrying out mechanical test on the rock cores to obtain physical and mechanical parameters of the rock layers and obtain the positions of key layers; then, an orthogonal multi-pole sub-array acoustic logging instrument extends into the geological exploration hole and reaches the key layer, acoustic measurement and data processing are carried out on the position, and then a geological interface imaging graph around the hole of the key layer and fracture distribution characteristics of the key layer are obtained; and finally, according to the fracture distribution characteristics, the key layer section is divided into a compact section, a fracture section and a high fracture section according to the division standard, and key layer positioning and internal structure classification are completed. By fusing a mutual feedback mechanism of multi-source information such as geological exploration, rock core test and logging imaging, quantitative identification and fine division of the key layer structure are realized, and data support is provided for improving the treatment efficiency of overlying strata in a deep coal mine and reducing the treatment cost.

Description

Technical Field

[0001] The present invention belongs to the field of coal mine key layer identification, and in particular relates to a deep coal mine key layer identification method based on multi-element information mutual feedback of geological exploration holes. Background Art

[0002] During deep coal mining, overburden structures often deform, fracture, and shift. These changes are the primary cause of dynamic hazards such as rock bursts and roof collapse. The key stratum, a crucial rock layer that controls the coordinated deformation and fracture evolution of the overburden, plays a decisive role in stress transmission and hazard formation at the working face due to its spatial location, thickness, and integrity. Therefore, accurately identifying the location and mechanical properties of the key stratum is a major challenge in current coal mine engineering geology. Existing methods for identifying the key stratum often rely on theoretical calculations and empirical criteria for parameters such as stratum thickness, stiffness, and strength. However, due to their significant simplification, they are unable to fully reflect the true structural characteristics under complex geological conditions. Particularly in deep, high-stress environments, rock strata exhibit hierarchical, multi-scale, and heterogeneous characteristics. Traditional methods can only determine the approximate location of the key stratum and struggle to identify its internal structural differences. Consequently, once the key stratum needs to be treated, the entire stratum must be constructed, which not only consumes significant human resources but also adds significant additional costs. In fact, the key layer includes both dense sections without cracks and sections with cracks developed to varying degrees. Clarifying these heterogeneous distributions is of great significance for subsequent precise management.

[0003] Therefore, how to provide a new method for identifying key layers in deep coal mines, which can focus on the structural differences within the key layers, realize the quantitative identification and fine division of the key layer structure, and provide data support for improving the efficiency of overburden management in deep coal mines and reducing management costs, is the research direction required by this invention. Summary of the Invention

[0004] In response to the problems existing in the above-mentioned existing technologies, the present invention provides a method for identifying key layers in deep coal mines based on the mutual feedback of multi-source information from geological exploration holes. By integrating the mutual feedback mechanism of multi-source information such as geological exploration, core testing and well logging imaging, the quantitative identification and fine division of key layer structures can be achieved, providing data support for improving the efficiency of overburden management in deep coal mines and reducing management costs.

[0005] In order to achieve the above object, the technical solution adopted by the present invention is: a method for identifying key layers in deep coal mines based on multi-element information feedback from geological exploration holes, comprising the following steps: Step 1: Core mechanical parameter testing: Construct a geological exploration hole, drill through each rock layer, collect cores from each rock layer during the drilling process, and determine the thickness of each rock layer; then perform mechanical testing on each core to obtain the physical and mechanical parameters of each rock layer, including density, elastic modulus, and tensile strength; Step 2: Locate the key layers: Based on the thickness, density, elastic modulus and tensile strength of each rock layer, the location of the key layers above the pre-mined coal seam is determined through calculation, including a main key layer and multiple sub-key layers; Step 3, reflection acoustic logging: An orthogonal multipole array acoustic logging instrument is inserted into the geological exploration hole and reaches the rock layer determined as the key layer in step 2. Acoustic measurement is performed at this location and reflected wave signals are extracted. The geological interface and fracture surface around the hole are imaged using the extracted reflected wave signals to obtain a geological interface image within a certain range around the key layer. The fracture distribution characteristics of the key layer are then obtained based on the geological interface image. Step 4: Critical layer segment classification: Based on the crack distribution characteristics of the critical layer, the critical layer segments are divided into dense segments, fractured segments, and highly fractured segments along the axial direction of the geological exploration hole according to the classification criteria, completing the key layer positioning and internal structure classification process. After classification, when conducting key layer treatment, blasting, fracturing, and other operations are mainly carried out on the dense and fractured segments. Since the highly fractured segments already have more cracks, centralized treatment is carried out on other areas. This not only makes the critical layer treatment more targeted and more effective, but also saves construction work and improves construction efficiency.

[0006] Furthermore, step one performs mechanical testing on each rock core, specifically: select a rock core and process it into a cylindrical sample and a disc-shaped sample respectively; first measure the mass and volume of the sample and calculate the density of the rock core; then perform a uniaxial compression test on the cylindrical sample, and use a strain gauge or extensometer to monitor the axial strain and lateral strain of the sample during the uniaxial compression process to obtain the compressive strength, elastic modulus and Poisson's ratio of the rock core; finally, perform a Brazilian split test on the disc-shaped sample to obtain the tensile strength of the rock core; repeat the above process for the remaining rock cores, thereby obtaining the density, elastic modulus and tensile strength of each rock layer.

[0007] Furthermore, the step 2 is specifically as follows: Determine the position of the hard rock layer in each rock layer from bottom to top: the hard rock layer refers to a rock layer that has a smaller deflection than the rock layer below it during deformation and does not deform in conjunction with the rock layer below it; Calculate the breaking distance of each hard rock layer. The specific formula is: Among them, l n is the breaking distance of the nth hard rock layer, m; q n is the load borne by the nth hard rock layer, MPa; (R T ) n is the tensile strength of the nth hard rock layer, MPa; H n is the thickness of the nth hard rock layer, m; According to the key layer identification theory, the position of the rock layer as the key layer is obtained by calculating the strength and stiffness of each rock layer and comparing them with the parameters of the adjacent rock layers. Specifically: The key layer mainly bears the self-weight and fracture deformation settlement load of the overlying non-key layer, among which the load caused by the overlying nth layer on the first layer (q n )1 is expressed as: Where: γ is the bulk density of the nth rock layer, kg / m 3 ;(q n )1 is the load generated when the nth layer of rock affects the first layer, kPa; T n is the elastic modulus of the nth rock layer, MPa; According to the theory of overburden key layer, if a certain rock layer is to be used as a key layer, it must first meet the following conditions (q n )1>(q n+1 ) 1, at this time, the q value is the load value generated by the interaction between the key layer and the overlying bearing rock layer; In addition to the above stiffness conditions, the key layer must also meet the strength conditions: Stiffness conditions: ; Strength conditions: ; If the calculated result of a certain rock layer does not meet the strength condition, the bearing rock layer load and self-weight of the layer will be applied as loads to the hard rock layer below it. Finally, a rock layer is obtained that meets both the stiffness condition and the strength condition. This rock layer is determined as the key layer. Then the determined key layers are divided according to the thickness or number of layers they can control. The rock layers that control the local activities of the overlying rock layers in the mining area are divided into sub-key layers, and the rock layers that control the activities of all rock layers up to the surface are divided into main key layers.

[0008] Furthermore, the orthogonal multipole array acoustic logging instrument in step three is cylindrical and consists of a transmitter, a receiver, and a sound insulator coaxially connected therebetween. The transmitter includes a monopole acoustic system and a dipole acoustic system. Both the transmitter and the receiver are made of piezoelectric ceramics, and the transmitter excites medium and high frequency acoustic signals through the piezoelectric effect.

[0009] Furthermore, the step three performs acoustic wave measurement on the key layer, specifically: performing acoustic wave measurement on the main key layer and sub-key layer through an orthogonal multipole array acoustic logging instrument, and capturing full-wave signals through the receiver on the instrument, which have various types of waveforms, including sliding longitudinal waves, sliding shear waves, Stoneley waves, reflected longitudinal waves, reflected shear waves and noise waveforms. These waveforms have different arrival time, phase and amplitude characteristics, which facilitate the subsequent extraction of reflected wave signals.

[0010] Furthermore, the step three extracts the reflected wave signal and images it, specifically, the full wave signal is processed in sequence as follows: suppressing the first wave to extract the reflected wave, separating the up and down wave fields, enhancing the reflected wave and performing offset imaging, thereby obtaining an imaging map of the geological interface around the key layer hole.

[0011] Furthermore, the crack distribution characteristics of the key layer are obtained in step three, specifically: the crack positions and geometric shapes of the key layer are obtained according to the geological interface imaging map, thereby determining the crack distribution characteristics of the key layer.

[0012] Furthermore, the division criteria of step 4 are: defining a section without obvious cracks as a dense section; defining a section with more than one and less than three cracks as a crack section; and defining a section with more than or equal to three cracks as a high-crack section.

[0013] Compared with the existing technology, the present invention first constructs a geological exploration hole, drills through various rock layers, collects rock cores from each rock layer during the drilling process, and performs mechanical tests on each rock core to obtain the physical and mechanical parameters of each rock layer; then, based on the mechanical parameters of each rock layer, the position of the key layer above the pre-mined coal seam is obtained; then, an orthogonal multipole array acoustic logging instrument is extended into the geological exploration hole and reaches the rock layer determined to be the key layer, acoustic wave measurement is performed on the position and the reflected wave signal is extracted, and after data processing, a geological interface image within a certain range around the key layer hole is obtained, and the crack distribution characteristics of the key layer are obtained; finally, based on the crack distribution characteristics, the key layer section is divided into a dense section, a crack section and a high crack section along the axial direction of the geological exploration hole according to the division criteria, completing the key layer positioning and internal structure classification process. The present invention realizes the quantitative identification and fine division of key layer structure through the mutual feedback mechanism of integrating multi-source information such as geological exploration, core test and logging imaging, providing a scientific basis for the stability analysis of overburden and disaster prevention and control in deep coal mines; and after classification, when carrying out key layer treatment, there is no need to construct the key layer as a whole, only blasting, fracturing and other operations are required for dense sections and fracture sections. Since the high-fracture section already has more fractures, by concentrating treatment on other areas, not only the key layer treatment is more targeted and the treatment effect is better, but also the construction workload is saved and the construction efficiency is improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 It is the overall flow chart of the present invention; Figure 2 This is a schematic diagram of acoustic logging of key layers in the present invention; Figure 3 This is a schematic diagram of the classification of key layer sections in the present invention. DETAILED DESCRIPTION

[0015] The present invention will be further described below.

[0016] like Figure 1 As shown, a method for identifying key layers in deep coal mines based on the mutual feedback of multivariate information of geological exploration holes includes the following steps: Step 1: Test the mechanical parameters of the rock core: Construct a geological exploration hole, drill it through each rock layer, collect rock cores from each rock layer during the drilling process, and determine the thickness of each rock layer; then perform a mechanical test on each rock core, specifically: select a rock core and process it into a cylindrical specimen and a disc-shaped specimen respectively; first measure the mass and volume of the specimen and calculate the density of the rock core; then perform a uniaxial compression test on the cylindrical specimen, and use a strain gauge or extensometer to monitor the axial strain and lateral strain of the specimen during the uniaxial compression process to obtain the compressive strength, elastic modulus and Poisson's ratio of the rock core; finally, perform a Brazilian splitting test on the disc-shaped specimen to obtain the tensile strength of the rock core; repeat the above process for the remaining rock cores to obtain the density, elastic modulus and tensile strength of each rock layer.

[0017] Step 2: Locate the key layers: Based on the thickness, density, elastic modulus and tensile strength of each rock layer, the location of the key layers above the pre-mined coal seam is determined through calculation, including a main key layer and multiple sub-key layers, specifically: Determine the position of the hard rock layer in each rock layer from bottom to top: the hard rock layer refers to a rock layer that has a smaller deflection than the rock layer below it during deformation and does not deform in conjunction with the rock layer below it; Calculate the breaking distance of each hard rock layer. The specific formula is: Among them, l n is the breaking distance of the nth hard rock layer, m; q n is the load borne by the nth hard rock layer, MPa; (R T ) n is the tensile strength of the nth hard rock layer, MPa; H n is the thickness of the nth hard rock layer, m; According to the key layer identification theory, the position of the rock layer as the key layer is obtained by calculating the strength and stiffness of each rock layer and comparing them with the parameters of the adjacent rock layers. Specifically: The key layer mainly bears the self-weight and fracture deformation settlement load of the overlying non-key layer, among which the load caused by the overlying nth layer on the first layer (q n )1 is expressed as: is the thickness of the nth rock layer, m.

[0018] According to the theory of overburden key layer, if a certain rock layer is to be used as a key layer, it must first meet the following conditions (q n )1>(q n+1) 1, at this time, the q value is the load value generated by the interaction between the key layer and the overlying bearing rock layer; In addition to the above stiffness conditions, the key layer must also meet the strength conditions: Stiffness conditions: ; Strength conditions: ; If the calculated result of a certain rock layer does not meet the strength condition, the bearing rock layer load and self-weight of the layer will be applied as loads to the hard rock layer below it. Finally, a rock layer is obtained that meets both the stiffness condition and the strength condition. This rock layer is determined as the key layer. Then the determined key layers are divided according to the thickness or number of layers they can control. The rock layers that control the local activities of the overlying rock layers in the mining area are divided into sub-key layers, and the rock layers that control the activities of all rock layers up to the surface are divided into main key layers.

[0019] Step 3, reflection acoustic logging: Use an orthogonal multipole array acoustic logging instrument to extend into the geological exploration hole and reach the rock layer determined as the main key layer and sub-key layer in step 2, perform acoustic measurement at the location and extract the reflected wave signal such as Figure 2 As shown in the figure, the geological interface and fracture surface around the hole are imaged by extracting the reflected wave signal, specifically: the main key layer and sub-key layer are measured by acoustic wave through the orthogonal multipole array acoustic logging instrument, and the full-wave signal is captured by the receiver on the instrument, which has various types of waveforms, including sliding longitudinal waves, sliding shear waves, Stoneley waves, reflected longitudinal waves, reflected shear waves and noise waveforms. These waveforms have different arrival time, phase and amplitude characteristics, which facilitate the subsequent extraction of reflected wave signals; then the full-wave signal is processed in sequence as follows: suppressing the first wave to extract the reflected wave, separating the uplink and downlink wave fields, enhancing the reflected wave and offset imaging, so as to obtain the geological interface imaging map within 10 meters around the key layer hole; according to the geological interface imaging map, the crack position and geometric shape of the key layer are obtained, so as to determine the crack distribution characteristics of the key layer. The above-mentioned orthogonal multipole array acoustic logging instrument is cylindrical and consists of a transmitter, a receiver and a sound insulator coaxially connected between the two. The transmitter includes a monopole acoustic system and a dipole acoustic system; both the transmitter and the receiver are made of piezoelectric ceramics, and the transmitter excites medium and high frequency acoustic wave signals through the piezoelectric effect.

[0020] Step 4. Classification of key layer sections: According to the crack distribution characteristics of the key layer, the classification criteria are as follows: the section without obvious cracks is defined as a dense section; the section with more than 1 and less than 3 cracks is defined as a fracture section; the section with more than or equal to 3 cracks is defined as a high fracture section; thus, the key layer section is divided into dense section, fracture section and high fracture section along the axial direction of the geological exploration hole. Figure 3As shown in the figure, the key layer positioning and internal structure classification process is completed. After classification, when carrying out key layer treatment, blasting and fracturing operations are mainly carried out on the dense and fractured sections. Since the highly fractured sections already have many cracks, centralized treatment of other areas not only makes the key layer treatment more targeted and more effective, but also saves construction work and improves construction efficiency.

[0021] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A method for identifying key layers in deep coal mines based on multi-element information feedback from geological exploration holes, characterized in that: The following steps are involved: Step 1: Core mechanical parameter testing: Construct a geological exploration hole, drill through each rock layer, collect cores from each rock layer during the drilling process, and determine the thickness of each rock layer; then perform mechanical testing on each core to obtain the physical and mechanical parameters of each rock layer, including density, elastic modulus, and tensile strength; Step 2: Locate the key layers: Based on the thickness, density, elastic modulus and tensile strength of each rock layer, the location of the key layers above the pre-mined coal seam is determined through calculation, including a main key layer and multiple sub-key layers; Step 3, reflection acoustic logging: An orthogonal multipole array acoustic logging instrument is inserted into the geological exploration hole and reaches the rock layer determined as the key layer in step 2. Acoustic measurement is performed at this location and reflected wave signals are extracted. The geological interface and fracture surface around the hole are imaged using the extracted reflected wave signals to obtain a geological interface image within a certain range around the key layer. The fracture distribution characteristics of the key layer are then obtained based on the geological interface image. Step 4: Classification of key layer sections: Based on the crack distribution characteristics of the key layer, the key layer sections are divided into dense sections, crack sections and high crack sections along the axial direction of the geological exploration hole according to the division standards, completing the key layer positioning and internal structure classification process.

2. The method for identifying key layers in deep coal mines based on multi-element information feedback from geological exploration holes according to claim 1 is characterized in that: The first step involves performing mechanical tests on each rock core, specifically: selecting a rock core and processing it into a cylindrical specimen and a disc-shaped specimen, respectively; first, measuring the mass and volume of the specimen to calculate the density of the rock core; then, performing a uniaxial compression test on the cylindrical specimen, and using a strain gauge or extensometer to monitor the axial strain and lateral strain of the specimen during the uniaxial compression process to obtain the compressive strength, elastic modulus, and Poisson's ratio of the rock core; finally, performing a Brazilian split test on the disc-shaped specimen to obtain the tensile strength of the rock core; and repeating the above process for the remaining rock cores to obtain the density, elastic modulus, and tensile strength of each rock layer.

3. The method for identifying key layers in deep coal mines based on multi-element information feedback from geological exploration holes according to claim 1 is characterized in that: The step 2 is specifically as follows: Determine the position of the hard rock layer in each rock layer from bottom to top: the hard rock layer refers to a rock layer that has a smaller deflection than the rock layer below it during deformation and does not deform in conjunction with the rock layer below it; Calculate the breaking distance of each hard rock layer. The specific formula is: Among them, l n is the breaking distance of the nth hard rock layer, m; q n is the load borne by the nth hard rock layer, MPa; (R T ) n is the tensile strength of the nth hard rock layer, MPa; H n is the thickness of the nth hard rock layer, m; According to the key layer identification theory, the position of the rock layer as the key layer is obtained by calculating the strength and stiffness of each rock layer and comparing them with the parameters of the adjacent rock layers. Specifically: The key layer mainly bears the self-weight and fracture deformation settlement load of the overlying non-key layer, among which the load caused by the overlying nth layer on the first layer (q n )1 is expressed as: Where: γ is the bulk density of the nth rock layer, kg / m 3 ;(q n )1 is the load generated when the nth layer of rock affects the first layer, kPa; T n is the elastic modulus of the nth rock layer, MPa; According to the theory of overburden key layer, if a certain rock layer is to be used as a key layer, it must first meet the following conditions (q n )1>(q n+1 ) 1, at this time, the q value is the load value generated by the interaction between the key layer and the overlying bearing rock layer; In addition to the above stiffness conditions, the key layer must also meet the strength conditions: Stiffness conditions: ; Strength conditions: ; If the calculated result of a certain rock layer does not meet the strength condition, the bearing rock layer load and self-weight of the layer will be applied as loads to the hard rock layer below it. Finally, a rock layer is obtained that meets both the stiffness condition and the strength condition. This rock layer is determined as the key layer. Then the determined key layers are divided according to the thickness or number of layers they can control. The rock layers that control the local activities of the overlying rock layers in the mining area are divided into sub-key layers, and the rock layers that control the activities of all rock layers up to the surface are divided into main key layers.

4. The method for identifying key layers in deep coal mines based on multi-element information feedback from geological exploration holes according to claim 1 is characterized in that: The orthogonal multipole array acoustic logging instrument in step three is cylindrical and consists of a transmitter, a receiver, and a sound insulator coaxially connected between the two. The transmitter includes a monopole acoustic system and a dipole acoustic system. Both the transmitter and the receiver are made of piezoelectric ceramics, and the transmitter excites medium and high frequency acoustic wave signals through the piezoelectric effect.

5. The method for identifying key layers in deep coal mines based on multi-element information feedback from geological exploration holes according to claim 1 is characterized in that: The step three is to perform acoustic wave measurement on the key layer, specifically: perform acoustic wave measurement on the main key layer and sub-key layer by using an orthogonal multipole array acoustic logging instrument, and capture the full-wave signal by the receiver on the instrument, which has various types of waveforms, including sliding longitudinal waves, sliding shear waves, Stoneley waves, reflected longitudinal waves, reflected shear waves and noise waveforms.

6. The method for identifying key layers in deep coal mines based on multi-element information feedback from geological exploration holes according to claim 5, characterized in that: The step three extracts the reflected wave signal and images it, specifically, the full wave signal is processed in sequence as follows: suppressing the first wave to extract the reflected wave, separating the up and down wave fields, enhancing the reflected wave and performing migration imaging, thereby obtaining a geological interface imaging map around the key layer hole.

7. The method for identifying key layers in deep coal mines based on multi-element information feedback from geological exploration holes according to claim 6, characterized in that: The step three of obtaining the crack distribution characteristics of the key layer is specifically as follows: according to the geological interface imaging map, the crack position and geometric shape of the key layer are obtained, thereby determining the crack distribution characteristics of the key layer.

8. The method for identifying key layers in deep coal mines based on multi-element information feedback from geological exploration holes according to claim 1 is characterized in that: The division criteria of step 4 are as follows: a section without obvious cracks is defined as a dense section; a section with more than one and less than three cracks is defined as a crack section; a section with more than or equal to three cracks is defined as a high crack section.

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