Weakly cemented overlying strata fracture partition division method suitable for western region

Abstract

The invention provides a weakly cemented overlying strata fracture partition division method suitable for the western region, and relates to the technical field of goaf overlying strata fracture partition division. According to the method, drilling does not need to be carried out in advance when the weakly cemented overlying strata is divided into the fractured zones, the working cost is reduced, scientificity is achieved, zone division is carried out from the aspects of the fracture form and the water blocking capacity of the weakly cemented overlying strata, and scientific guidance can be provided for the problems of on-site ground surface settlement prediction, multi-coal-seam mining, water-preserved mining and the like; quantitative calculation is adopted to characterize the water blocking capacity of the water-resisting layer, the relation between the seepage velocity of the water-resisting layer and the supply velocity of the overlying aquifer serves as the standard for judging whether the water-resisting layer has the water blocking capacity or not, the strong and weak fissure zone range is determined according to the standard, and the standard can serve as the theoretical basis for implementing the water-preserved mining technology.

Description

Technical Field

[0001] The invention relates to the technical field of overburden fracture zoning division in goaf areas, and in particular to a method for dividing weakly cemented overburden fracture zoning division suitable for western regions. Background Art

[0002] After the working face is pushed and mined, different areas of the overburden present different forms of collapse and damage. According to the special engineering geological conditions, it is necessary to consider the targeted overburden fracture zoning method, which has a great impact on the safety control issues such as multi-coal seam pressure relief mining, surface deformation, water conservation mining and underground support. Therefore, considering the impact of mining, a targeted method for the zoning division of weakly cemented overburden fracture is proposed, which is of great significance to the safe and efficient production of coal mines.

[0003] Traditionally, there are mainly empirical formula method, field measurement method and simulation analysis method for the division of overburden strata in goaf areas. The empirical formula method is based on statistical fitting of a large number of field measured data, taking into account the mining thickness of coal seams, overburden lithology, etc. This method is simple and easy to implement, but its accuracy and scientificity are poor; the field measurement method mainly adopts geophysical method and borehole detection method, which directly observes and analyzes the engineering site, and has good accuracy for the development of fractures in specific engineering sites, but also has some disadvantages, such as high drilling measurement cost, and the observation method is mainly macroscopic observation, which mainly observes the development height of water-conducting fracture zones. Usually, due to the failure to consider the overburden strata lithology, structure and other issues, the analysis of water retention, pressure relief and other issues is not comprehensive, and it cannot be well applied to the division of overburden rupture zoning; the simulation analysis method mainly adopts similar material simulation and numerical simulation methods, which can more intuitively show the overburden rupture characteristics and stress displacement field distribution law, and has a certain effect on the overburden rupture zoning, but because this method greatly simplifies the engineering site, the simulation results are somewhat different from the engineering site, and can only serve as a reference.

[0004] At present, the overburden strata are divided into caving zones, fissure zones and curved subsidence zones in the vertical direction. This division method mainly considers the fracture and migration characteristics of the overburden strata, and does not consider the impact of different areas in the overburden strata on the overall settlement of the overburden, stress changes in different areas and permeability change characteristics. The analysis of some problems such as multi-coal seam mining unloading and water conservation mining is not in-depth enough. Moreover, under the conditions of weakly cemented overburden strata widely distributed in the western region, the above three-zone division method of overburden strata is less applicable. Summary of the invention

[0005] The present invention provides a method for dividing the fracture zones of weakly cemented overburden suitable for the western region. The method divides the fracture zones of weakly cemented overburden according to the engineering geological characteristics of the rock (coal) layer and the influence of mining, thus avoiding the problems of single consideration factors, single results and poor scientificity of the traditional three-zone empirical formula of overburden.

[0006] In order to achieve the above object, the technical solutions adopted by the present invention are as follows:

[0007] A method for dividing fracture zones of weakly cemented overburden applicable to the western region, the method comprising the following steps:

[0008] Step 1: Obtain basic physical, mechanical and hydrogeological parameters of the overburden rock;

[0009] Step 2, determine the relative position of the overburden fracture partition in the goaf area;

[0010] Step 3: Calculate the fracture zone range of weakly cemented overburden in the goaf area.

[0011] Furthermore, the specific implementation process of step 1 is as follows:

[0012] According to the distribution of rock (coal) layers revealed by geological drilling, the thickness of the mined coal seam, the physical and mechanical parameters of the overlying rock layers, and the hydrogeological parameters are obtained.

[0013] Furthermore, the specific implementation process of step 2 is as follows:

[0014] According to the occurrence characteristics of the overlying rock (coal) layer, the weakly cemented overlying rock fracture zones in the goaf are divided into caving zone, structural balance zone, fracture zone and curved subsidence zone along the vertical direction.

[0015] Among them, if the overlying rock (coal) layer contains aquifers, the fracture zone will be specifically divided into strong fracture zones and weak fracture zones to analyze the disturbance of the aquifer.

[0016] Furthermore, in step 3, the process of determining the thickness of the caving zone is as follows:

[0017] The thickness of the caving zone is estimated based on the calculation formula of the thickness of the weakly bonded immediate roof obtained by inversion. Based on the measured data of the working resistance of the working face support, the calculation formula of the thickness of the weakly bonded immediate roof is:

[0018]

[0019] In the formula,

[0020] M Z —Thickness of the immediate roof, m; F S —The working resistance of the hydraulic support after the working surface pressure ends, kN; α—The angle between the hydraulic support column and the hydraulic support top beam, °; L 1—The distance from the hydraulic support column to the hydraulic support top beam’s action point to the end, m; G—The weight of the hydraulic support top beam, kg; L s —Length of top beam of hydraulic support, m; L d —center distance between adjacent hydraulic supports, m; γ Z —Direct top density, kN / m 3 ; L k —Hydraulic support top control distance, m;

[0021] The thickness of the caving zone is from the coal seam roof to M Z .

[0022] Furthermore, in step 3, the process of determining the thickness of the structural balance zone is as follows:

[0023] To determine the thickness of the structural balance zone, it is necessary to first understand the lithology of the overburden and determine whether an articulated rock block is formed after the rock formation is fractured. The structural balance zone is composed of the basic top of the working face or the overburden hard rock group. The estimation formula of the thickness of the structural balance zone is shown in formula (2);

[0024]

[0025] In the formula,

[0026] M E —Basic top thickness, m; M J —Thickness of structural balance zone, m; K T —Basic top rock and beam rock redistribution coefficient; ΔF—Difference in working resistance from the beginning to the end of the pressure cycle, kN; C—pressure step distance, m; γ E —Body weight of fractured rock, kN / m 3 ;b—breaking step distance, m; M max — ultimate bending moment of rock fracture, kN·m; σ t —Ultimate tensile strength of rock formation, MPa;

[0027] The thickness of the structural balance zone is M above the coal seam. Z To M J .

[0028] Furthermore, in step 3, the process of determining the thickness of strong and weak fracture zones is as follows:

[0029] According to the seepage velocity calculation formula (3), the water-isolating capacity of the overlying rock layer in the structural balance zone is quantitatively calculated;

[0030] First, determine the positional relationship between the overlying aquifer and the aquiclude, and number the overlying rock strata as i=1, 2, 3, ..., n;

[0031] Then the seepage velocity of each aquifer and the recharge velocity of the overlying aquifer are calculated. When the seepage velocity of the aquifer is greater than the recharge velocity of the overlying aquifer, that is, v1 When / v>1, the aquiclude has no water blocking ability, that is, it is a strong fracture zone; when the seepage velocity of the aquiclude is less than the recharge velocity of the overlying aquifer, that is, v 1 When / v≤1, the aquiclude has water blocking ability, that is, it is a weak fracture zone;

[0032]

[0033] In the formula,

[0034] v—aquifer recharge rate, m / d; Q—aquifer unit water yield, L / (s·m); A—seepage unit cross-sectional area of ​​the aquiclude in the study area, m 2 ;v 1 —seepage velocity of the aquiclude, m / d; ΔH—pressure difference of the i-th aquiclude, m; n—the i-th aquiclude is divided into n deformation micro-units; L—the length of the i-th aquiclude affected by mining, m, where L=2M 0 cotδ 0 +W,M 0 is the distance between the impermeable layer and the coal seam roof, m, δ 0 is the moving boundary angle, °; W—the coal seam mining length or strike length along the aquifer i section of the study area, m; M i —Thickness of the i-th waterproof layer, m; K ij —permeability coefficient of deformation unit j in the i-th aquiclude; L ij —The length of deformation unit j in the i-th aquiclude, m; k 0 —initial permeability, md; ε vij —Volume strain of deformable element j in the i-th aquiclude; —initial porosity, %; ρ—aquifer water density, kg·m -3 ; g—gravitational acceleration, m·s -2 ; η—dynamic viscosity coefficient, mPa·s; x—horizontal distance between the predicted point on the surface of deformation unit j in aquiclude i and the underground mining unit point, m; S(x',z i-1 )—the subsidence value of the upper rock layer of the aquiclude i at x', m; x'—the horizontal distance between the surface estimated point of deformation unit j in the i-1th rock layer and the underground mining unit point, m; a i —sinking coefficient of aquiclude i; R i —The main influence radius of the aquiclude i, m; q—The number of rock layers from the mined coal seam to the target aquiclude; h—The depth of the working face, m; d 1i , d 2i —Offset distance of the inflection points on the left and right sides of the aquiclude i, m, d for near-horizontal rock layers 1i =d 2i ;

[0035] When the i-th waterproof layer is judged to have water blocking capacity from the structural balance zone upward, the thickness of the strong fracture zone is M J To M i-1 , the thickness of the weak fracture zone is M i-1 To M i , where M i-1 is the height of the i-1th rock layer from the coal seam, M i is the height of the i-th rock layer from the coal seam.

[0036] Furthermore, in step 3, the process of determining the thickness of the curved sinking zone is as follows:

[0037] If the curved subsidence zone is located on the upper part of the weak fracture zone, the thickness of the curved subsidence zone is from the upper part of the coal seam to the ground surface.

[0038] The beneficial technical effects of the present invention are:

[0039] 1. The present invention does not require advance drilling when dividing the weakly cemented overburden fracture zones, which reduces work costs and is scientific. The zones are divided according to the fracture form and water-blocking capacity of the weakly cemented overburden, which can provide scientific guidance for on-site surface subsidence prediction, multi-coal seam mining, water-saving mining and other issues.

[0040] 2. The present invention adopts quantitative calculation to characterize the water-blocking capacity of the aquiclude, and takes the relationship between the seepage velocity of the aquiclude and the recharge velocity of the overlying aquifer as the standard for determining whether the aquiclude has water-blocking capacity. The range of strong and weak fracture zones is determined based on this, which can serve as a theoretical basis for implementing water-saving mining technology. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 It is a flow chart of a method for dividing weakly cemented overburden fracture zones applicable to the western region according to an embodiment of the present invention;

[0042] Figure 2 Schematic diagram of relative positions of fractured zones of weakly cemented overburden in goaf according to an embodiment of the present invention;

[0043] Figure 3 This is a columnar diagram of the overlying rock (coal) layer of a coal mine 3-1 in an embodiment of the present invention;

[0044] Figure 4 This is a distribution location map of weakly cemented overburden fracture zones in the 3-1 coal goaf area of ​​a coal mine according to an embodiment of the present invention. DETAILED DESCRIPTION

[0045] In order to make the purpose, technical scheme and beneficial effects of the present invention more clearly understood, the present invention is further described in detail below in combination with specific embodiments and with reference to the accompanying drawings. Certain embodiments of the present invention will be described more comprehensively with reference to the accompanying drawings, in which some but not all embodiments will be shown. In fact, the various embodiments of the present invention can be implemented in many different forms and should not be construed as being limited to the embodiments described herein; rather, these embodiments are provided so that the present invention meets applicable legal requirements.

[0046] In the description of the present invention, it should be noted that the terms "inside", "outside", "upper", "lower", "front", "back" and the like indicate directions or positional relationships based on directions or positional relationships shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific direction, be constructed and operated in a specific direction, and therefore cannot be understood as limiting the present invention. In addition, the terms "first" and "second" are used for descriptive purposes only, and cannot be understood as indicating or implying relative importance.

[0047] This embodiment is combined with the actual situation of a coal mine. Figures 1 to 4 As shown, a method for dividing fracture zones of weakly cemented overburden applicable to the western region is provided, comprising the following steps.

[0048] Step 1: Obtain basic physical, mechanical and hydrogeological parameters of the overburden rock

[0049] The specific implementation process of step 1 is as follows:

[0050] According to the distribution of rock (coal) layers revealed by geological drilling, the thickness of the mined coal seam, the physical and mechanical parameters of the overlying rock layers, and the hydrogeological parameters are obtained.

[0051] Through on-site investigation of the geological characteristics of coal in a coal mine, the rock (coal) layer column diagram is as follows: Figure 3 As shown, the upper 42.09m of 3-1 coal seam is mostly mineable 2-2 medium coal, and the upper 65.05m is distributed with thick aquifer of Middle Jurassic Zhiluo Formation. The characteristic parameters of coal seam and surrounding rock are obtained, including rock mechanical properties parameters of main rock (coal) layer, interlayer spacing, hydrogeological characteristic parameters, burial depth, mining thickness and other parameters. Some geological parameters of overlying rock layer of 3-1 coal are shown in Table 1.

[0052] Table 1 3-1 Calculation parameters of coal overburden fracture zoning

[0053]

[0054] Step 2: Determine the relative position of the overburden fracture division in the goaf area

[0055] The specific implementation process of step 2 is as follows:

[0056] According to the occurrence characteristics of the overlying rock (coal) layer, the weakly cemented overlying rock fracture zones in the goaf are divided into caving zone, structural balance zone, fracture zone and curved subsidence zone along the vertical direction.

[0057] Among them, if the overlying rock (coal) layer contains aquifers, the fracture zone will be specifically divided into strong fracture zones and weak fracture zones to analyze the disturbance of the aquifer.

[0058] Each overlying rock (coal) layer has the following occurrence characteristics:

[0059] ① Spalling zone: It is mainly composed of weakly cemented roof. Due to the characteristics of its rock strata, it is very easy to collapse. After a large area of ​​rock collapses in the spalling zone, discrete broken rock blocks are formed. After the collapse, the gangue formed in the goaf plays a supporting role for the overlying rock strata. The pores between the broken rock blocks are large, the permeability coefficient is greatly increased, and it has strong conductivity.

[0060] ② Structural balance zone: It is mainly composed of stable articulated balanced structural rock strata formed by mutual compression under the action of horizontal force after fracture in the overlying rock. It has a major controlling effect on the manifestation of mine pressure on the working face and the migration of overlying rock strata. It can be composed of the basic top of the working face or the overlying hard rock group. After fracture, obvious through cracks are formed between the articulated rock blocks, which have strong conductivity, and the integrity and continuity of the rock strata are poor.

[0061] ③ Strong and weak fracture zones: mainly composed of fractured rock formations with low fracture degree in the upper part of the structural balance zone. This area is divided into strong and weak fracture zones according to the degree of fracture development. Among them, the degree of fracture development in the strong fracture zone is high, the degree of pressure relief is good, but it does not have water-proofing ability, and has integrity and continuity to a certain extent; the degree of fracture development in the weak fracture zone is relatively low, the degree of pressure relief is poorer than that of the strong fracture zone, and the pressure relief range is small, but it has water-proofing ability, good integrity and continuity.

[0062] ④Bending and sinking zone: It is mainly composed of the bending and sinking rock strata in the upper part of the weak fracture zone. The rock strata show an overall bending and sinking destruction form. The degree of development of cracks inside the rock strata is low, the degree and range of pressure relief are small, and good integrity and continuity are maintained.

[0063] According to the geological occurrence characteristics of the overlying rock (coal) layers of the 3-1 coal, there are mineable coal seams and aquifers distributed above the 3-1 coal. Therefore, it is determined to divide the overlying rock (coal) layers of the 3-1 coal into caving zones, structural balance zones, strong fracture zones, weak fracture zones and curved subsidence zones. According to the different zones where the coal in 2-2 is located, the surrounding rock fracture characteristics are determined, and the strong and weak fracture zones are divided to analyze the disturbance of the 3-1 coal mining on the overlying aquifer.

[0064] Step 3: Calculation of the fracture zoning range of weakly cemented overburden in the goaf

[0065] The process of determining the thickness of the caving zone is as follows:

[0066] The thickness of the caving zone is estimated based on the calculation formula of the thickness of the weakly bonded immediate roof obtained by inversion. Based on the measured data of the working resistance of the working face support, the calculation formula of the thickness of the weakly bonded immediate roof is:

[0067]

[0068] In the formula,

[0069] M Z —Thickness of the immediate roof, m; F S —The working resistance of the hydraulic support after the working surface pressure ends, kN; α—The angle between the hydraulic support column and the hydraulic support top beam, °; L 1 —The distance from the hydraulic support column to the hydraulic support top beam’s action point to the end, m; G—The weight of the hydraulic support top beam, kg; L s —Length of top beam of hydraulic support, m; L d —center distance between adjacent hydraulic supports, m; γ Z —Direct top density, kN / m 3 ; L k —Hydraulic support top control distance, m;

[0070] The thickness of the caving zone is from the coal seam roof to M Z .

[0071] The process of determining the thickness of the structural balance belt is as follows:

[0072] To determine the thickness of the structural balance zone, it is necessary to first understand the lithology of the overburden and determine whether an articulated rock block is formed after the rock formation is fractured. The structural balance zone is composed of the basic top of the working face or the overburden hard rock group. The estimation formula of the thickness of the structural balance zone is shown in formula (2);

[0073]

[0074] In the formula,

[0075] M E —Basic top thickness, m; M J —Thickness of structural balance zone, m; K T —Basic top rock and beam rock redistribution coefficient; ΔF—Difference in working resistance from the beginning to the end of the pressure cycle, kN; C—pressure step distance, m; γ E —Body weight of fractured rock, kN / m 3 ;b—breaking step distance, m; M max — ultimate bending moment of rock fracture, kN·m; σ t —Ultimate tensile strength of rock formation, MPa;

[0076] The thickness of the structural balance zone is M above the coal seam. ZTo M J .

[0077] The process of determining the thickness of strong and weak fracture zones is as follows:

[0078] According to the seepage velocity calculation formula (3), the water-isolating capacity of the overlying rock layer in the structural balance zone is quantitatively calculated;

[0079] First, determine the positional relationship between the overlying aquifer and the aquiclude, and number the overlying rock strata as i=1, 2, 3, ..., n;

[0080] Then the seepage velocity of each aquifer and the recharge velocity of the overlying aquifer are calculated. When the seepage velocity of the aquifer is greater than the recharge velocity of the overlying aquifer, that is, v 1 When / v>1, the aquiclude has no water blocking ability, that is, it is a strong fracture zone; when the seepage velocity of the aquiclude is less than the recharge velocity of the overlying aquifer, that is, v 1 When / v≤1, the aquiclude has water blocking ability, that is, it is a weak fracture zone;

[0081]

[0082] In the formula,

[0083] v—aquifer recharge rate, m / d; Q—aquifer unit water yield, L / (s·m); A—seepage unit cross-sectional area of ​​the aquiclude in the study area, m 2 ;v 1 —seepage velocity of the aquiclude, m / d; ΔH—pressure difference of the i-th aquiclude, m; n—the i-th aquiclude is divided into n deformation micro-units; L—the length of the i-th aquiclude affected by mining, m, where L=2M 0 cotδ 0 +W,M 0 is the distance between the impermeable layer and the coal seam roof, m, δ 0 is the moving boundary angle, °; W—the coal seam mining length or strike length along the aquifer i section of the study area, m; M i —Thickness of the i-th waterproof layer, m; K ij —permeability coefficient of deformation unit j in the i-th aquiclude; L ij —The length of deformation unit j in the i-th aquiclude, m; k 0 —initial permeability, md; ε vij —Volume strain of deformable element j in the i-th aquiclude; —initial porosity, %; ρ—aquifer water density, kg·m -3 ; g—gravitational acceleration, m·s -2; η—dynamic viscosity coefficient, mPa·s; x—horizontal distance between the predicted point on the surface of deformation unit j in aquiclude i and the underground mining unit point, m; S(x',z i-1 )—the subsidence value of the upper rock layer of the aquiclude i at x', m; x'—the horizontal distance between the surface estimated point of deformation unit j in the i-1th rock layer and the underground mining unit point, m; a i —sinking coefficient of aquiclude i; R i —The main influence radius of the aquiclude i, m; q—The number of rock layers from the mined coal seam to the target aquiclude; h—The depth of the working face, m; d 1i , d 2i —Offset distance of the inflection points on the left and right sides of the aquiclude i, m, d for near-horizontal rock layers 1i =d 2i ;

[0084] When the i-th waterproof layer is judged to have water blocking capacity from the structural balance zone upward, the thickness of the strong fracture zone is M J To M i-1 , the thickness of the weak fracture zone is M i-1 To M i , where M i-1 is the height of the i-1th rock layer from the coal seam, M i is the height of the i-th rock layer from the coal seam.

[0085] The process of determining the thickness of the curved sinking zone is as follows:

[0086] If the curved subsidence zone is located on the upper part of the weak fracture zone, the thickness of the curved subsidence zone is from the upper part of the coal seam to the ground surface.

[0087] According to the hydrogeological characteristic parameters of the overburden rock (coal) layer in the study area 3-1, the parameters required by equations (1) to (3) are substituted into the calculation to obtain the distribution range of the weakly cemented overburden fracture zones in the goaf area.

[0088] The measured data is substituted into formula (1) to calculate the thickness of the immediate roof, which is 9.5 m. The range of the caving zone is determined to be 9.5 m from the 3-1 coal roof upwards. Then the required parameters are substituted into formula (2) to estimate the thickness of the structural balance zone to be about 33.68 m. The range of the structural balance zone is preliminarily determined to be 9.5 m to 43.18 m. This range includes conglomerate, sandy mudstone and 2-2 medium coal seams. Since the characteristics of sandy mudstone and 2-2 medium coal do not conform to the characteristics of the structural balance zone, the structural balance zone is determined to be The upper part is composed of thick conglomerate layer, and the conglomerate layer ranges from 35.3m above the 3-1 coal roof. Therefore, the structural balance zone is determined to be from 9.5m to 35.3m above the 3-1 coal roof. Finally, the strong and weak fracture zones of the fractured rock layer above the structural balance zone are determined, and the impermeable layers above the structural balance zone are numbered (impermeable layers #1, #2, #3). The water-blocking capacity of the impermeable layers is determined and calculated one by one. The calculated aquifer recharge rate is 2.1×10 -3 m / d, the seepage velocity of the overlying aquiclude #1 in the mining area is 3.3×10 -2 m / d, the seepage velocity of aquiclude #2 is 5.2×10 -5 m / d, the aquiclude #2 has water-blocking capacity under the influence of mining, so it is determined that the aquiclude #2 is a weak fracture zone, and it is determined that the upper part of the 3-1 coal roof is from 35.3m to 51.55m as a strong fracture zone, and the upper part of 51.55m to 65.05m is a weak fracture zone, and the curved subsidence zone is located from 65.05m to the surface of the upper part of the 3-1 coal roof.

[0089] In summary, the results of the zoning of weakly cemented overburden fractures are as follows: the caving zone ranges from 9.5m above the 3-1 coal, the structural balance zone ranges from 9.5m to 35.3m above the 3-1 coal, the strong fracture zone ranges from 35.3m to 51.55m above the 3-1 coal, the weak fracture zone is located at about 51.55m to 65.05m above the 3-1 coal roof, and the curved sinking zone is located from 65.05m above the 3-1 coal roof to the surface. The distribution of the zoning of weakly cemented overburden fractures in the 3-1 coal goaf area is as follows: Figure 4 shown.

[0090] So far, the present embodiment has been described in detail in conjunction with the accompanying drawings. Based on the above description, those skilled in the art should have a clear understanding of the weakly cemented overburden fracture zoning method applicable to the western region of the present invention. The weakly cemented overburden fracture zoning method applicable to the western region of the present invention does not require advance drilling when zoning the weakly cemented overburden fracture, which reduces work costs and is scientific. Zoning is carried out from the aspects of the fracture form and water blocking capacity of the weakly cemented overburden, which can provide scientific guidance for on-site surface subsidence prediction, multi-coal seam mining, water-conserving mining and other issues; quantitative calculation is used to characterize the water blocking capacity of the aquiclude, and the relationship between the seepage velocity of the aquiclude and the recharge velocity of the overlying aquifer is used as the standard for determining whether the aquiclude has water blocking capacity, and the range of strong and weak fracture zones is determined on this basis, which can serve as a theoretical basis for implementing water-conserving mining technology.

[0091] The specific embodiments described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for dividing weakly cemented overburden fracture zones suitable for the western region, characterized in that: The method comprises the following steps: Step 1: Obtain basic physical, mechanical and hydrogeological parameters of the overburden rock; Step 2, determine the relative position of the overburden fracture partition in the goaf area; Step 3: Calculate the fracture zone range of weakly cemented overburden in the goaf area.

2. A method for dividing fracture zones of weakly cemented overburden rocks applicable to the western region according to claim 1, characterized in that: The specific implementation process of step 1 is as follows: According to the distribution of rock (coal) layers revealed by geological drilling, the thickness of the mined coal seam, the physical and mechanical parameters of the overlying rock layers, and the hydrogeological parameters are obtained.

3. A method for dividing weakly cemented overburden fracture zones applicable to the western region according to claim 2, characterized in that: The specific implementation process of step 2 is as follows: According to the occurrence characteristics of the overlying rock (coal) layer, the weakly cemented overlying rock fracture zones in the goaf are divided into caving zone, structural balance zone, fracture zone and curved subsidence zone along the vertical direction. Among them, if the overlying rock (coal) layer contains aquifers, the fracture zone will be specifically divided into strong fracture zones and weak fracture zones to analyze the disturbance of the aquifer.

4. A method for dividing fracture zones of weakly cemented overburden rocks applicable to the western region according to claim 3, characterized in that: In step 3, the process of determining the thickness of the caving zone is as follows: The thickness of the caving zone is estimated based on the calculation formula of the thickness of the weakly bonded immediate roof obtained by inversion. Based on the measured data of the working resistance of the working face support, the calculation formula of the thickness of the weakly bonded immediate roof is: In the formula, M Z —Thickness of the immediate roof, m; F S —The working resistance of the hydraulic support after the working surface pressure ends, kN; α—The angle between the hydraulic support column and the hydraulic support top beam, °; L1—The distance from the hydraulic support column to the hydraulic support top beam to the end, m; G—The weight of the hydraulic support top beam, kg; L s —Length of top beam of hydraulic support, m; L d —center distance between adjacent hydraulic supports, m; γ Z —Direct top density, kN / m 3 ; L k —Hydraulic support top control distance, m; The thickness of the caving zone is from the coal seam roof to M Z .

5. A method for dividing fracture zones of weakly cemented overburden rocks applicable to the western region according to claim 4, characterized in that: In step 3, the process of determining the thickness of the structural balance zone is as follows: To determine the thickness of the structural balance zone, it is necessary to first understand the lithology of the overburden and determine whether an articulated rock block is formed after the rock formation is fractured. The structural balance zone is composed of the basic top of the working face or the overburden hard rock group. The estimation formula of the thickness of the structural balance zone is shown in formula (2); In the formula, M E —Basic top thickness, m; M J —Thickness of structural balance zone, m; K T —Basic top rock and beam rock redistribution coefficient; ΔF—Difference in working resistance from the beginning to the end of the pressure cycle, kN; C—pressure step distance, m; γ E —Body weight of fractured rock, kN / m 3 ;b—breaking step distance, m; M max — ultimate bending moment of rock fracture, kN·m; σ t —Ultimate tensile strength of rock formation, MPa; The thickness of the structural balance zone is M above the coal seam. Z To M J .

6. A method for dividing fracture zones of weakly cemented overburden rocks applicable to the western region according to claim 5, characterized in that: In step 3, the process of determining the thickness of strong and weak fracture zones is as follows: According to the seepage velocity calculation formula (3), the water-isolating capacity of the overlying rock layer in the structural balance zone is quantitatively calculated; First, determine the positional relationship between the overlying aquifer and the aquiclude, and number the overlying rock strata as i=1, 2, 3, ..., n; Then the seepage velocity of each aquiclude and the recharge velocity of the overlying aquifer are calculated. When the seepage velocity of the aquiclude is greater than the recharge velocity of the overlying aquifer, that is, v1 / v>1, the aquiclude has no water blocking ability, that is, it is a strong fracture zone; when the seepage velocity of the aquiclude is less than the recharge velocity of the overlying aquifer, that is, v1 / v≤1, the aquiclude has water blocking ability, that is, it is a weak fracture zone. In the formula, v—aquifer recharge rate, m / d; Q—aquifer unit water yield, L / (s·m); A—seepage unit cross-sectional area of ​​the aquiclude in the study area, m 2 ; v1—seepage velocity of aquiclude, m / d; ΔH—pressure difference of the water head of the ith aquiclude, m; n—the ith aquiclude is divided into n deformation micro-units; L—the length of the ith aquiclude affected by mining, m, where L=2M0 cotδ0+W, M0 is the distance between the aquiclude and the coal seam roof, m, δ0 is the moving boundary angle, °; W—the length or strike length of the coal seam along the i-section direction of the aquiclude in the study area, m; M i —Thickness of the i-th waterproof layer, m; K ij —permeability coefficient of deformation unit j in the i-th aquiclude; L ij —length of deformation unit j in the i-th aquiclude, m; k0 —initial permeability, md; ε vij —Volume strain of deformable element j in the i-th aquiclude; —initial porosity, %; ρ—aquifer water density, kg·m -3 ; g—gravitational acceleration, m·s -2 ; η—dynamic viscosity coefficient, mPa·s; x—horizontal distance between the predicted point on the surface of deformation unit j in aquiclude i and the underground mining unit point, m; S(x',z i-1 )—the subsidence value of the upper rock layer of the aquiclude i at x', m; x'—the horizontal distance between the surface estimated point of deformation unit j in the i-1th rock layer and the underground mining unit point, m; a i —sinking coefficient of aquiclude i; R i —The main influence radius of the aquiclude i, m; q—The number of rock layers from the mined coal seam to the target aquiclude; h—The depth of the working face, m; d 1i , d 2i —Offset distance of the inflection points on the left and right sides of the aquiclude i, m, d for near-horizontal rock layers 1i =d 2i ; When the i-th waterproof layer is judged to have water blocking capacity from the structural balance zone upward, the thickness of the strong fracture zone is M J To M i-1 , the thickness of the weak fracture zone is M i-1 To M i , where M i-1 is the height of the i-1th rock layer from the coal seam, M i is the height of the i-th rock layer from the coal seam.

7. A method for dividing fracture zones of weakly cemented overburden rocks applicable to the western region according to claim 6, characterized in that: In step 3, the process of determining the thickness of the curved sinking zone is as follows: If the curved subsidence zone is located on the upper part of the weak fracture zone, the thickness of the curved subsidence zone is from the upper part of the coal seam to the ground surface.

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