Exploration method for rock burst energy easy-to-release key layer

Abstract

The invention discloses a rock burst energy easy-to-release key layer exploration method, which comprises the following exploration processes: step 1, calculating and determining a hard soil-covered rock layer, and determining the position of the hard rock layer in the soil-covered rock layer and the position of a soft rock layer group controlled by the hard rock layer by judging the hard rock layer; 2, the fracture displacement of each hard rock stratum is calculated; thirdly, the fracture distances of all the hard rock stratums are compared, and the positions of key stratums are determined; 4, exploring a rock stratum between the separation position and the water flowing fractured zone through conventional logging, underground imaging and coring test modes; and 5, comprehensively analyzing to obtain the position of the key layer in combination with a calculation result and an actual probing condition. According to the exploration method, a theoretical basis is combined with an on-site exploration result, the position of a key layer can be accurately positioned, and effective support is provided for follow-up separation layer grouting treatment and large-energy mine earthquake prevention.

Description

Technical Field

[0001] The invention relates to the technical field of geological exploration, and in particular to a method for detecting a key layer where rock burst energy can be easily released. Background Art

[0002] The large-scale goaf formed by coal seam mining will inevitably cause serious damage to the overburden, and the time and space process is relatively complex. The overburden damage height is of great significance for coal mining under water, water conservation mining, and liberation layer mining for gas control. Since the overburden damage height is related to the lithology, in general, the damage height of the soft overburden is 9 to 12 times the mining thickness, the medium-hard overburden is 12 to 18 times the mining thickness, and the hard overburden is 18 to 28 times the mining thickness.

[0003] There are usually multiple key layers above the coal seam. This paper analyzes the process of mine tremors induced by the movement of multiple key layers. Figure 1 As shown, assuming that there are the first, second, and i-th key layers, the distances between the coal seam and the key layers are h1, h2, ..., hi respectively, and the distance from the ground surface is H. Ei (i=1, 2...n) in the figure represents the energy released by a fracture of the i-th key layer.

[0004] like Figure 1 As shown in the figure, with the advancement of the working face, the overburden strata begin to be exposed and fractured. When the first key layer fractures, the energy released is E1; when the second key layer fractures, the energy released is E2; when the i-th key layer fractures, the energy released is Ei. The energy released by the key layer fracture will spread to the surroundings. When the low-level key layer fractures, part of the energy will be transferred to the high-level key layer. When the high-level key layer fractures, part of the energy will continue to be transferred to the higher-level key layer until the rupture height of the overburden strata reaches the surface. At this time, a cycle of mine earthquake induced by the fracture of the key layer is completed and the next cycle is entered. The mine earthquake induced by the fracture of multiple key layers has obvious periodicity. In addition, each key layer in the multiple key layers "alone" fractures, which will undergo the process of rock burst energy accumulation and release, but the multiple key layers affect each other. The low-level key layer will transfer energy to the high-level key layer, and the high-level key layer will also compress the low-level key layer to fracture. However, there is currently no effective exploration method for the key layer that is easy to release rock burst energy. Summary of the invention

[0005] In view of the shortcomings in the prior art, the present invention provides a method for detecting key layers where impact rock pressure energy is easily released. The method combines theoretical basis with field exploration results, can accurately locate the position of the key layer, and provide effective support for subsequent delamination grouting treatment and prevention of large-energy mine earthquakes.

[0006] A method for detecting key layers where rock burst energy can be easily released, the detection process is as follows:

[0007] Step 1: Calculate and determine the hard overburden rock layer, and identify the position of the hard rock layer in the overburden rock layer and the position of the soft rock layer group it controls by distinguishing the hard rock layer;

[0008] Step 2, calculating the breaking distance of each hard rock layer;

[0009] Step 3, comparing the fracture distances of each hard rock layer to determine the position of the key layer;

[0010] Step 4: Exploring the rock layer between the separation position and the water-conducting fracture zone by conventional logging, downhole imaging, and coring analysis;

[0011] Step 5: Combine the calculation results with the actual exploration situation and conduct a comprehensive analysis to determine the location of the key layer.

[0012] As a preferred embodiment of the above technical solution, in step 1, the hard rock layer is a rock layer whose deflection is smaller than that of the lower rock layer during deformation, but does not deform in coordination with the lower rock layer. The load of the first hard rock layer is calculated according to the composite beam principle as follows:

[0013]

[0014] In the formula, it is assumed that the first rock layer is a hard rock layer, the first to mth rock layers are deformed in a coordinated manner and the curvatures of the rock layers are the same, and the m+1th rock layer is the second hard rock layer, q1(x) m is the load exerted by the mth rock layer on the first hard rock layer; h i , γ i 、E i are the thickness, bulk density, and elastic modulus of the i-th rock layer, respectively. i = 1, 2, ..., m. Then the load exerted by the m+1-th layer on the first hard rock layer is:

[0015]

[0016] Since the m+1th layer is a hard rock layer, its deflection is smaller than that of the lower rock layer. The rock layers above the m+1th layer no longer need the lower rock layer to bear the load it bears. Therefore, it must be:

[0017] q1(x) m+1 <q1(x) m

[0018] Integrating and simplifying the above formulas, we can get the hard rock layer position determination formula:

[0019]

[0020] When making specific judgments, calculate layer by layer starting from the first rock layer above the coal seam. and When the hard rock layer position discrimination formula is satisfied, the calculation will no longer proceed upwards. At this time, starting from the 1st layer upwards, the m+1th layer is the 1st hard rock layer. Starting from the 1st hard rock layer, the position of the 2nd hard rock layer is determined according to the above method, and so on, until the top hard rock layer is determined, wherein the top hard rock layer is set as the nth hard rock layer. By discriminating the position of the hard rock layer, the position of the hard rock layer in the overburden and the soft rock layer group it controls are obtained.

[0021] As a preferred embodiment of the above technical solution, in step 2, the breaking distance of the hard rock layer is calculated using the fixed-end beam model, then the breaking distance L of the k-th hard rock layer is k It can be calculated by the following formula:

[0022]

[0023] In the formula, h k is the thickness of the kth hard rock layer, in m; σ k is the tensile strength of the kth hard rock layer, in MPa; q k is the load borne by the kth hard rock layer, in MPa, then q k The deterministic formula is:

[0024]

[0025] In the formula, k represents the kth hard rock layer, k = 1, 2, ..., n-1. Since the elastic energy of the topsoil layer can be regarded as 0, assuming the thickness of the topsoil layer is H and the bulk density is γ, the load on the top hard rock layer, i.e. the nth hard rock layer, can be calculated as follows:

[0026]

[0027] Where, j represents the layer number of the soft rock layer group controlled by the kth hard rock layer; m k is the number of soft rock layers controlled by the kth hard rock layer; E K,j 、h k，j , γ k，j are the elastic modulus, layer thickness and bulk density of the jth rock layer in the soft rock layer group controlled by the kth hard rock layer, in GPa, m, and MN / m respectively. 3 , when j=0, it is the mechanical parameter of the hard rock layer.

[0028] As a preferred embodiment of the above technical solution, in step 3, the breaking distances of various rock layers are compared and the position of the key layer is determined according to the following formula:

[0029] L k <L K+1

[0030] In the formula, k represents the kth hard rock layer, k = 1, 2, ..., n-1. If the breaking distance of the kth layer satisfies the above formula, then the kth hard rock layer is the key layer.

[0031] As a preferred embodiment of the above technical solution, in step 4, the development position of the overburden rock layer is first determined through unexpected situations during the drilling process, and then the soft and hard bottom positions of the rock layer development positions are analyzed and confirmed through conventional well logging, downhole imaging, and core sampling analysis.

[0032] Compared with the prior art, the present invention has the following beneficial effects:

[0033] This exploration method combines drilling with computational analysis to identify the key layer locations where rock burst can be easily released in the delamination-developed part of the mine, making it easier to analyze the locations where mine tremors and high-energy events occur, thereby improving the effect of delamination grouting treatment and better preventing the occurrence of high-energy mine tremors. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 This is the mining earthquake model induced by the fracture of key layers in the background technology.

[0035] Figure 2 This is a flow chart of the detection method invented. DETAILED DESCRIPTION

[0036] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0037] The present invention is further described in detail below in conjunction with the accompanying drawings:

[0038] A method for detecting key layers where rock burst energy can be easily released, the detection process is as follows:

[0039] Step 1: Calculate and determine the hard overburden rock layer, and identify the position of the hard rock layer in the overburden rock layer and the position of the soft rock layer group it controls by distinguishing the hard rock layer;

[0040] Step 2, calculating the breaking distance of each hard rock layer;

[0041] Step 3, comparing the fracture distances of each hard rock layer to determine the position of the key layer;

[0042] Step 4: Exploring the rock layer between the separation position and the water-conducting fracture zone by conventional logging, downhole imaging, and coring analysis;

[0043] Step 5: Combine the calculation results with the actual exploration situation and conduct a comprehensive analysis to determine the location of the key layer.

[0044] In this embodiment, in step 1, the hard rock layer is a rock layer whose deflection is smaller than that of the lower rock layer during deformation, but does not deform in coordination with the lower rock layer. The load of the first hard rock layer is calculated according to the composite beam principle as follows:

[0045]

[0046] In the formula, it is assumed that the first rock layer is a hard rock layer, the first to mth rock layers are deformed in a coordinated manner and the curvatures of the rock layers are the same, and the m+1th rock layer is the second hard rock layer, q1(x) m is the load exerted by the mth rock layer on the first hard rock layer; h i , γ i 、E i are the thickness, bulk density, and elastic modulus of the i-th rock layer, respectively. i = 1, 2, ..., m. Then the load exerted by the m+1-th layer on the first hard rock layer is:

[0047]

[0048] Since the m+1th layer is a hard rock layer, its deflection is smaller than that of the lower rock layer. The rock layers above the m+1th layer no longer need the lower rock layer to bear the load it bears. Therefore, it must be:

[0049] q1(x) m+1 <q1(x) m

[0050] Integrating and simplifying the above formulas, we can get the hard rock layer position determination formula:

[0051]

[0052] When making specific judgments, calculate layer by layer starting from the first rock layer above the coal seam. and When the hard rock layer position discrimination formula is satisfied, the calculation will no longer proceed upwards. At this time, starting from the 1st layer upwards, the m+1th layer is the 1st hard rock layer. Starting from the 1st hard rock layer, the position of the 2nd hard rock layer is determined according to the above method, and so on, until the top hard rock layer is determined, wherein the top hard rock layer is set as the nth hard rock layer. By discriminating the position of the hard rock layer, the position of the hard rock layer in the overburden and the soft rock layer group it controls are obtained.

[0053] In this embodiment, in step 2, the breaking distance of the hard rock layer is calculated using the fixed-end beam model, so the breaking distance L of the k-th hard rock layer is k It can be calculated by the following formula:

[0054]

[0055] In the formula, h k is the thickness of the kth hard rock layer, in m; σ k is the tensile strength of the kth hard rock layer, in MPa; q k is the load borne by the kth hard rock layer, in MPa, then q k The deterministic formula is:

[0056]

[0057] In the formula, k represents the kth hard rock layer, k = 1, 2, ..., n-1. Since the elastic energy of the topsoil layer can be regarded as 0, assuming the thickness of the topsoil layer is H and the bulk density is γ, the load on the top hard rock layer, i.e. the nth hard rock layer, can be calculated as follows:

[0058]

[0059] Where, j represents the layer number of the soft rock layer group controlled by the kth hard rock layer; m k is the number of soft rock layers controlled by the kth hard rock layer; E K,j 、h k，j , γ k，j are the elastic modulus, layer thickness and bulk density of the jth rock layer in the soft rock layer group controlled by the kth hard rock layer, in GPa, m, and MN / m respectively. 3 , when j=0, it is the mechanical parameter of the hard rock layer.

[0060] In this embodiment, in step 3, the breaking distances of the various rock layers are compared and the key layer position is determined according to the following formula:

[0061] L k <L K+1

[0062] In the formula, k represents the kth hard rock layer, k = 1, 2, ..., n-1. If the breaking distance of the kth layer satisfies the above formula, then the kth hard rock layer is the key layer.

[0063] Specifically, if the breaking distance of the kth hard rock layer is greater than the breaking distance of the k+1th hard rock layer above it, the load borne by the k+1th hard rock layer is added to the kth hard rock layer, and the breaking distance of the kth hard rock layer is recalculated. If the recalculated breaking distance of the kth hard rock layer is less than the breaking distance of the k+1th hard rock layer, L is taken. k <L K+1 This means that the breaking of the kth hard rock layer is controlled by the k+1th hard rock layer, that is, before the k+1th hard rock layer breaks, the kth hard rock layer does not break. Once the k+1th hard rock layer breaks, its load acts on the kth hard rock layer, causing the kth hard rock layer to break.

[0064] Starting from the bottom hard rock layer, judge layer by layer. k <l k+1 (k=1,2,…,n-1) is true, and when L k <L K+1 Recalculate the breaking distance of the kth hard rock layer.

[0065] In this embodiment, in step 4, the development position of the overburden rock layer is first determined through unexpected conditions during the drilling process, and then the soft and hard transition positions of the rock layer development positions are analyzed and confirmed through conventional logging, downhole imaging, and coring analysis.

[0066] Next, in step five, the position of the key layer for easy release of rock burst energy is determined based on the previously calculated key layer breaking distance. Specifically, the actual development position of the overburden detachment layer can be inferred based on the calculated key layer breaking distance and the position of drill drop and leakage in actual drilling. Finally, the hard rock layer above the detachment development position is found by referring to the logging, downhole imaging and core sampling results, and the position of the key layer for easy release of rock burst energy can be determined. That is, the hard rock layer above the overburden detachment development position is the key layer for easy release of rock burst energy.

[0067] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for detecting key layers where rock burst energy can be easily released, characterized in that: The exploration process is: Step 1: Calculate and determine the hard overburden rock layer, and identify the position of the hard rock layer in the overburden rock layer and the position of the soft rock layer group it controls by distinguishing the hard rock layer; Step 2, calculating the breaking distance of each hard rock layer; Step 3, comparing the fracture distances of each hard rock layer to determine the position of the key layer; Step 4: Exploring the rock layer between the separation position and the water-conducting fracture zone by conventional logging, downhole imaging, and coring analysis; Step 5: Combine the calculation results with the actual exploration situation and conduct a comprehensive analysis to determine the location of the key layer.

2. A method for detecting key layers where rock burst energy can be easily released according to claim 1, characterized in that: In step 1, the hard rock layer is a rock layer whose deflection is smaller than that of the lower rock layer during deformation, but does not deform in coordination with the lower rock layer. The load of the first hard rock layer is calculated according to the composite beam principle: In the formula, it is assumed that the first rock layer is a hard rock layer, the first to mth rock layers are deformed in a coordinated manner and the curvatures of the rock layers are the same, and the m+1th rock layer is the second hard rock layer, q1(x) m is the load exerted by the mth rock layer on the first hard rock layer; h i , γ i 、E i are the thickness, bulk density, and elastic modulus of the i-th rock layer, respectively. i = 1, 2, ..., m. Then the load exerted by the m+1-th layer on the first hard rock layer is: Since the m+1th layer is a hard rock layer, its deflection is smaller than that of the lower rock layer. The rock layers above the m+1th layer no longer need the lower rock layer to bear the load it bears. Therefore, it must be: q1(x) m+1 <q1(x) m Integrating and simplifying the above formulas, we can get the hard rock layer position determination formula: When making specific judgments, calculate layer by layer starting from the first rock layer above the coal seam. and When the hard rock layer position discrimination formula is satisfied, the calculation will no longer proceed upwards. At this time, starting from the 1st layer upwards, the m+1th layer is the 1st hard rock layer. Starting from the 1st hard rock layer, the position of the 2nd hard rock layer is determined according to the above method, and so on, until the top hard rock layer is determined, wherein the top hard rock layer is set as the nth hard rock layer. By discriminating the position of the hard rock layer, the position of the hard rock layer in the overburden and the soft rock layer group it controls are obtained.

3. The method for detecting key layers where rock burst energy can be easily released according to claim 1, characterized in that: In step 2, the breaking distance of the hard rock layer is calculated using the fixed-end beam model, so the breaking distance of the k-th hard rock layer is L k It can be calculated by the following formula: In the formula, h k is the thickness of the kth hard rock layer, in m; σ k is the tensile strength of the kth hard rock layer, in MPa; q k is the load borne by the kth hard rock layer, in MPa, then q k The deterministic formula is: In the formula, k represents the kth hard rock layer, k = 1, 2, ..., n-1. Since the elastic energy of the topsoil layer can be regarded as 0, assuming the thickness of the topsoil layer is H and the bulk density is γ, the load on the top hard rock layer, i.e. the nth hard rock layer, can be calculated as follows: Where, j represents the layer number of the soft rock layer group controlled by the kth hard rock layer; m k is the number of soft rock layers controlled by the kth hard rock layer; E K,j 、h k，j , γ k，j are the elastic modulus, layer thickness and bulk density of the jth rock layer in the soft rock layer group controlled by the kth hard rock layer, in GPa, m, and MN / m respectively. 3 , when j=0, it is the mechanical parameter of the hard rock layer.

4. A method for detecting key layers where rock burst energy can be easily released according to claim 1, characterized in that: In step 3, the breaking distances of each rock layer are compared and the position of the key layer is determined according to the following formula: L k <L K+1 In the formula, k represents the kth hard rock layer, k = 1, 2, ..., n-1. If the breaking distance of the kth layer satisfies the above formula, then the kth hard rock layer is the key layer.

5. The method for detecting key layers where rock burst energy can be easily released according to claim 1 is characterized in that: In step 4, the development position of the overburden rock layer is first determined through unexpected situations during the drilling process, and then the soft and hard bottom positions of the rock layer development positions are analyzed and confirmed through conventional logging, downhole imaging, and core sampling analysis.

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