Method for analyzing and calculating height of caving zone of hard roof of thick coal seam

Abstract

The invention provides a method for analyzing and calculating the height of a caving zone of a hard roof of a thick coal seam, and the method comprises the steps: obtaining the height and density of a key layer in an effective range through the calculation of physical and mechanical parameters of a coal seam working face based on a key layer theory; calculating the gravity center of the caving zone according to the constructed caving zone arch equation; calculating according to the gravity center of the caving zone to obtain a coal seam floor stress prediction value; and measuring to obtain a true stress value of the coal seam floor, and calculating to obtain the caving zone height according to a comparison result of the predicted stress value of the coal seam floor and the true stress value of the coal seam floor. According to the method, the height of the caving zone is accurately analyzed and calculated through the stress condition of the coal seam floor, the stability of the goaf is improved, and the damage rate of the goaf is reduced.

Description

Technical Field

[0001] The invention relates to the technical field of mine mining, and in particular to a method for analyzing and calculating the height of a hard roof collapse zone in a thick coal seam. Background Art

[0002] During the mining process, the rock blocks are broken and piled up, forming disordered rock blocks and ordered rock blocks. In disordered rock blocks, the top rock mass collapses directly, impacting the bottom of the coal seam, causing the rock strata to break and pile up in the goaf in a disordered manner. The rock blocks are of different sizes, with large gaps and expanded volumes, almost completely losing their original layered structure. Ordered rock blocks are located above the disordered rock block layer. The broken rock blocks are larger, the rock layer volume increases, and the spacing between blocks is smaller, forming a relatively regular stacking and maintaining the original layered structure. Among them, the development height of the collapse zone is affected by factors such as the thickness of the coal seam, the structure of the overburden, the thickness, the lithology of the overburden, and the geological structure.

[0003] However, the existing collapse zone height calculation method cannot accurately analyze and calculate the movement and deformation of the rock layer according to the stress condition of the coal seam floor. Therefore, it is very necessary to design a method for analyzing and calculating the collapse zone height of the hard roof of thick coal seams. Summary of the invention

[0004] The purpose of the present invention is to provide a method for analyzing and calculating the height of the collapse zone of the hard roof of a thick coal seam, so as to realize accurate analysis and calculation of the collapse zone height through the stress conditions of the coal seam bottom plate, so as to improve the stability of the goaf and reduce the destruction rate of the goaf.

[0005] To achieve the above object, the present invention provides the following solutions:

[0006] A method for analyzing and calculating the height of a hard roof collapse zone in a thick coal seam comprises the following steps:

[0007] Based on the key layer theory, the key layer height and key layer density within the effective range are calculated through the physical and mechanical parameters of the coal seam working face;

[0008] The center of gravity of the collapse zone is calculated based on the constructed collapse zone arch equation;

[0009] The predicted value of the force on the coal seam floor is obtained by calculating the center of gravity of the collapse zone;

[0010] The actual value of the coal seam floor force is measured, and the height of the collapse zone is calculated based on the comparison result between the predicted value of the coal seam floor force and the actual value of the coal seam floor force.

[0011] Optionally, the effective range is 100 meters.

[0012] Alternatively, the expression of the collapse zone arch equation is: Among them, d is the length of the coal seam working face, h is the thickness of the overlying rock layer, the y-axis is the height direction of the collapse zone, and the x-axis is the advancement length direction of the coal seam working face.

[0013] Optionally, the calculation formula for the center of gravity of the collapse zone is: Among them, h g It is the distance from the center of gravity of the collapse zone to the top of the first overlying rock layer.

[0014] Optionally, the calculation formula for the predicted value of the coal seam floor force is: Among them, σ n is the predicted value of the stress on the coal seam floor of the nth overlying rock layer, h gi is the distance from the center of gravity of the collapse zone to the top of the i-th overlying rock layer, γ i is the density of the i-th overburden layer, and h1 is the height of the first overburden layer.

[0015] Optionally, the calculation formula for the collapse zone height is: Among them, H is the height of the collapse zone, P is the true value of the force on the coal seam floor, γ n is the density of the nth overlying rock layer.

[0016] According to the specific embodiments provided by the present invention, the present invention discloses the following technical effects: the present invention provides a method for analyzing and calculating the height of the collapse zone of the hard roof of a thick coal seam, the method comprising: based on the key layer theory, calculating the key layer height and key layer density within the effective range through the physical and mechanical parameters of the coal seam working face; calculating the center of gravity of the collapse zone according to the constructed collapse zone arch equation; calculating the predicted force value of the coal seam floor according to the center of gravity of the collapse zone; measuring the actual force value of the coal seam floor, and calculating the collapse zone height according to the comparison result of the predicted force value of the coal seam floor and the actual force value of the coal seam floor. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. 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 creative labor.

[0018] Figure 1 It is a flow chart of the collapse zone height analysis and calculation method of the present invention;

[0019] Figure 2 It is an analytical diagram of the arch equation of the collapse zone of the present invention. DETAILED DESCRIPTION

[0020] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only 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.

[0021] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and understandable, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0022] like Figure 1 As shown, the present invention takes a collapse zone formed by the collapse of hard rock strata in a thick coal seam mining in a mine in Xinjiang as an embodiment, and provides a method for analyzing and calculating the height of the collapse zone of the hard roof of a thick coal seam, including the following steps:

[0023] Step 100: Based on the key layer theory, the key layer height and key layer density within the effective range are calculated by using the physical and mechanical parameters of the coal seam working face;

[0024] Specifically, cores were drilled in the coal seam working face and its roof and floor plates, and their physical and mechanical parameters such as tensile strength, Poisson's ratio, elastic modulus, deformation modulus, cohesion and internal friction angle were tested. Based on the key layer theory, the key layer distribution within 100m of the roof was calculated, and the third thick hard rock layer of sandy mudstone overlying the coal seam working face was found to be the key layer. The heights of the overlying rock layers within 100m are h1=1m, h2=57.12m and h3=48.8m, respectively, and the densities of the overlying rock layers are γ1=2.46g / cm 3 ,γ2=2.35g / cm 3 and γ3=2.23g / cm 3 .

[0025] Step 200: Calculate the center of gravity of the collapse zone according to the constructed collapse zone arch equation;

[0026] Specific as Figure 2 As shown in the figure, after the collapse of the first layer of overburden above the coal seam working face, the rock has a large accumulation space in the goaf, and the collapse zone formed is regarded as a rectangle. The space for the collapse of the second layer and above overburden begins to be limited, and the collapse zone formed by it is regarded as a parabolic arch. According to the calculation formula of the arch, the arch equation of the collapse zone is constructed and solved to obtain the center of gravity of the arch collapse zone, and the distance from the center of gravity to the top of the first layer of overburden is recorded as h g In this embodiment, the length of the coal seam working face is d=180m.

[0027] More specifically, the equation of the arched parabola formed by the collapse zone is expressed as: y = ax 2+bx+c; where a, b and c are all unknown constants. The coordinates of the left end point O, the right end point B and the vertex A of the arc parabola are (0, 0), (d, 0) and Substituting points O, B, and A into the arcuate parabola equation, we obtain and c=0, so the expression of the arch equation of the collapse zone is:

[0028]

[0029] Among them, d is the length of the coal seam working face, h is the thickness of the overlying rock layer, the y-axis is the height direction of the collapse zone, and the x-axis is the advancement length direction of the coal seam working face.

[0030] Furthermore, the horizontal coordinate position of the center of gravity of the collapse zone is The calculation formula of the ordinate is:

[0031]

[0032] Among them, h g is the distance from the center of gravity of the collapse zone to the top of the first overlying rock layer. Combined with the collapse zone arch equation, it is calculated to

[0033] Step 300: Calculate the predicted value of the coal seam floor force according to the center of gravity of the collapse zone;

[0034] Specifically, after the collapse of the first layer of overlying rock, the collapsed rock basically fills the goaf, and the distribution of its accumulation body is regarded as a rectangle. Starting from the second layer of rock, the distribution of the accumulation body gradually forms an arch.

[0035] When the first overlying rock layer collapses, the calculation formula for the predicted force value σ1 of the coal seam floor is: σ1=h1γ1;

[0036] When the second overburden layer collapses, the calculation formula for the predicted force value σ2 of the coal seam floor is: σ2=σ1+h g2 γ2;

[0037] When the nth layer of overlying rock collapses, the predicted value of the stress on the coal seam floor σ n The calculation formula is: n =σ1+σ2+…+σ n-1 +h gn γ n ;

[0038] The calculation formula for the predicted value of the coal seam floor force when the nth layer of overlying rock collapses is:

[0039]

[0040] Among them, σ nis the predicted value of the stress on the coal seam floor of the nth overlying rock layer, h gi is the distance from the center of gravity of the collapse zone to the top of the i-th overlying rock layer, γ i is the density of the i-th overburden layer, and h1 is the height of the first overburden layer.

[0041] Step 400: Measure the actual value of the coal seam floor stress, and calculate the collapse zone height based on the comparison result between the predicted value of the coal seam floor stress and the actual value of the coal seam floor stress.

[0042] Specifically, when the direct roof of the coal seam rotates and the force on the coal seam floor tends to be stable, the actual value of the force on the coal seam floor is measured by a dynamometer and is P=350 kN.

[0043] More specifically, when When the overlying rock layer collapses completely, the collapse zone height is calculated to be 17.75m. The calculation formula for the collapse zone height is:

[0044]

[0045] Among them, H is the height of the collapse zone, P is the true value of the force on the coal seam floor, γ n is the density of the nth overlying rock layer.

[0046] Furthermore, the calculated collapse zone height is used to predict and control the collapse of the rock strata above the goaf, thereby reducing the risk of safety accidents such as mine collapse and mine water disasters.

[0047] The beneficial effects of the present invention are as follows:

[0048] 1) The actual value of the coal seam floor force is obtained through actual measurement with a dynamometer, ensuring the reliability of the calculated data;

[0049] 2) The stress condition of the coal seam floor enables accurate calculation of the height of the collapse zone, reduces surface settlement, improves the stability of the goaf, and reduces the destruction rate of the goaf.

[0050] The various embodiments in this specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the various embodiments can be referenced to each other.

[0051] The present invention uses specific examples to illustrate the principles and implementation methods of the present invention. The above examples are only used to help understand the method and core ideas of the present invention. At the same time, for those skilled in the art, according to the ideas of the present invention, there will be changes in the specific implementation methods and application scope. In summary, the content of this specification should not be understood as limiting the present invention.

Claims

1. A method for analyzing and calculating the height of the hard roof collapse zone of a thick coal seam, characterized in that: The steps include: Based on the key layer theory, the key layer height and key layer density within the effective range are calculated through the physical and mechanical parameters of the coal seam working face; The center of gravity of the collapse zone is calculated based on the constructed collapse zone arch equation; The predicted value of the force on the coal seam floor is obtained by calculating the center of gravity of the collapse zone; The actual value of the force on the coal seam floor is measured, and the height of the collapse zone is calculated based on the comparison result between the predicted value of the force on the coal seam floor and the actual value of the force on the coal seam floor.

2. The method for analyzing and calculating the height of the hard roof collapse zone of a thick coal seam according to claim 1 is characterized in that: The effective range is 100 meters.

3. The method for analyzing and calculating the height of the hard roof collapse zone of a thick coal seam according to claim 1 is characterized in that: The expression of the collapse zone arch equation is: Among them, d is the length of the coal seam working face, h is the thickness of the overlying rock layer, the y-axis is the height direction of the collapse zone, and the x-axis is the advancement length direction of the coal seam working face.

4. The method for analyzing and calculating the height of the hard roof collapse zone of a thick coal seam according to claim 3 is characterized in that: The calculation formula of the center of gravity of the collapse zone is: Among them, h g It is the distance from the center of gravity of the collapse zone to the top of the first overlying rock layer.

5. The method for analyzing and calculating the height of the hard roof collapse zone of a thick coal seam according to claim 1 is characterized in that: The calculation formula for the predicted value of the coal seam floor force is: Among them, σ n is the predicted value of the stress on the coal seam floor of the nth overlying rock layer, h gi is the distance from the center of gravity of the collapse zone to the top of the i-th overlying rock layer, γ i is the density of the i-th overlying rock layer, and h1 is the height of the first overlying rock layer.

6. The method for analyzing and calculating the height of the hard roof collapse zone of a thick coal seam according to claim 5 is characterized in that: The calculation formula of the collapse zone height is: Among them, H is the height of the collapse zone, P is the true value of the force on the coal seam floor, γ n is the density of the nth overlying rock layer.

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