Early warning method of water inrush from coal mine roof separation based on multi-factor indicators

Abstract

The present application relates to a method for early warning of water inrush from delamination of coal mine roof based on multi-factor indicators, including: identifying the location of water-accumulating delamination of overburden, upper rock layer and lower aquiclude of mining overburden; determining the different breaking sequences of upper rock layer and lower aquiclude under mining action based on the breaking criteria of upper rock layer and lower aquiclude during mining of working face; selecting microseismic early warning indicators, constructing a multi-factor microseismic early warning model for delamination of coal mine roof and obtaining a microseismic comprehensive early warning signal; constructing a water level early warning model based on the water level evolution type during the evolution of delamination of working face roof and obtaining a water level early warning signal; establishing a support resistance early warning indicator model based on the support resistance early warning indicator of delamination water inrush and obtaining a support resistance early warning signal; establishing a comprehensive early warning model based on the microseismic early warning signal, water level early warning signal and support resistance early warning signal, and obtaining a multi-factor comprehensive early warning indicator result. The present application realizes accurate early warning of water inrush from delamination of coal mine roof.

Description

Technical Field

[0001] The present application belongs to the technical field of mine water hazard prevention and control, and specifically relates to a coal mine roof delamination and water inrush warning method based on multi-factor indicators. Background Art

[0002] During the mining process of the mining area / working face, due to the uneven settlement of the overlying rock strata, a closed abscission space develops near the aquifer and forms an abscission water body. Once the aquiclude is broken, a water inrush channel is formed between the abscission layer and the mining area / working face, and abscission water inrush occurs. In recent years, the high-mining and fully-mechanized mining conditions of the Jurassic-Cretaceous overburden have led to frequent abscission water inrush, causing varying degrees of property losses and even casualties.

[0003] At present, coal mine microseismic early warning is widely used in the field of rock burst. The early warning method for mine water inrush is basically based on the water inrush cases of aquifers within the traditional water-conducting fracture zone. Through the analysis methods of mathematical statistics and decision theory, fixed monitoring signals are selected to establish comprehensive early warning indicators.

[0004] However, unlike traditional mine water inrush, the evolution of delamination water inrush is the result of the coupling of engineering mining and in-situ overburden. The evolution mechanism of delamination water inrush is different under different engineering geological conditions. Therefore, the response characteristics of various monitoring signals of mining overburden in the process of disaster preparation and disaster causing are quite different. The early warning of delamination water inrush needs to fully consider the evolution law of mining overburden structure, analyze the mechanism of delamination water inrush disaster, and then select appropriate monitoring indicators for comprehensive early warning. However, it is difficult to achieve accurate early warning of delamination water inrush in mining working face based only on the existing early warning method of roof water inrush, which leads to a certain blindness in the early warning of delamination water during the advancement of the working face, and cannot effectively ensure mining safety. Summary of the invention

[0005] In view of the above analysis, an embodiment of the present invention aims to provide a coal mine roof delamination water inrush warning method based on multi-factor indicators to solve at least one of the above problems existing in the prior art.

[0006] The object of the present invention is achieved in that:

[0007] A coal mine roof separation water inrush early warning method based on multi-factor indicators, comprising:

[0008] S1. Establish an engineering geological model of the mining overburden to identify the locations of the water-accumulating strata, upper rock layers and lower aquicludes of the mining overburden;

[0009] S2. Based on the fracture criterion of the upper rock layer and the lower aquiclude during mining, determine the different fracture sequences of the upper rock layer and the lower aquiclude under mining action; select microseismic early warning indicators, construct a multi-factor microseismic early warning model for water inrush from the roof of the coal mine, and obtain a comprehensive microseismic early warning signal;

[0010] S3. Based on the water level evolution type during the evolution of the roof absorptive water of the working face, a water level warning model is constructed to obtain a water level warning signal;

[0011] S4. Establish a support resistance warning indicator model based on the support resistance warning indicator of delamination water inrush, and obtain a support resistance warning signal;

[0012] S5. Based on the microseismic warning signal, water level warning signal and support resistance warning signal, a comprehensive warning model is established to obtain a multi-factor comprehensive warning indicator result.

[0013] Furthermore, in step S2, microseismic early warning indicators are selected based on the different fracture sequences of the upper rock layer and the lower impermeable layer under mining action and the water inrush situation during the mining of the working face.

[0014] Further, in step S2, the breaking criteria of the upper rock layer and the lower aquiclude are:

[0015]

[0016] In the above formula, α is the exposed length of the rock layer; β is the thickness of the upper rock layer or the lower impermeable layer; Λ is the elastic modulus of the upper rock layer or the lower impermeable layer; χ is the bending stiffness of the elastic beam section; q is the total load on the rock layer; x and y are the horizontal and vertical coordinates of the model respectively; M is the mining height of the working face; K p h is the rock layer expansion coefficient, which is 1.03-1.035; n is the distance between the upper rock layer or the lower aquiclude floor and the coal seam roof; σ c is the uniaxial compressive strength of rock; m, s, a are the Hooke-Brown criterion constants;

[0017] Among them, when J(x,y)>1, the rock layer is broken.

[0018] Furthermore, in step S3, the water level evolution type during the evolution of the working face roof absorptive water is divided into a water level periodic fluctuation type and a water level continuous drop type, and a water level warning model of the water level periodic fluctuation type and the water level continuous drop type is constructed to obtain a water level warning signal of the water level periodic fluctuation type and the water level continuous drop type.

[0019] Furthermore, in step S3, the judgment conditions for the water level periodic fluctuation type and the water level continuous drop type are as follows:

[0020] For the water level periodic fluctuation type: during the entire mining period, there is only one water-absorbed layer, and only one adjacent rock layer in the aquifer meets the following judgment conditions:

[0021]

[0022] The remaining adjacent rock layers all meet the following judgment conditions:

[0023] as well as

[0024] For the type of continuous water level decline: During the entire mining period, multiple water-accumulated strata are formed at the bottom and inside of the aquifer, and there are two or more adjacent rock layers in the aquifer that meet the following conditions:

[0025]

[0026] In the above formula, Λ i-1 ,Λ i and Λ i+1 is the elastic modulus of the i-1, i and i+1 layers; i-1 ,Ψ i and i+1 is the thickness of the i-1, i and i+1 layers.

[0027] Furthermore, for the periodic fluctuation of water level, the water level change is selected as the early warning indicator; for the continuous drop of water level, the water level change and the speed of water level change are selected as early warning indicators.

[0028] Further, in step S3, based on the water level change warning discrimination model, a water level change warning signal L is calculated; based on the water level change speed warning discrimination model, a water level change speed warning signal V is calculated;

[0029] Among them, the water level change warning discrimination model is:

[0030] L= <RH 0 -RH i >

[0031] The water level change speed early warning discrimination model is:

[0032] V= <v 0 -v d >

[0033] In the above formula, <> is the discriminant function, and there is RH t Represents the water level change at time t; RH 0 is the water level change warning threshold; L and V are 1, indicating that the indicator has reached the warning threshold; L and V are 0, indicating that the indicator has not reached the warning threshold; v d Indicates the speed of water level change; v 0 It is the water level change speed warning threshold.

[0034] Further, in step S4, the support resistance warning index MP of delamination water inrush is calculated according to the following formula:

[0035]

[0036] In the above formula, γ is the average volume force of the rock mass, Z is the resistance at the end of the support cycle, S is the top beam area, H lc It is the distance between the roof of the lower aquiclude and the roof of the coal seam.

[0037] Furthermore, the support resistance early warning model is:

[0038] P= <MP t -MP 0 >

[0039] In the above formula, < > is the discriminant function, MP t It indicates the early warning index of the support resistance at time t; MP 0 is the warning threshold of the support resistance; P is 1, indicating that the indicator reaches the warning threshold; 0 indicates that the indicator does not reach the warning threshold.

[0040] Further, in step S5, the comprehensive early warning model is:

[0041] EWI=L·(E·P+V)

[0042] In the above formula, L, E, P, and V represent the water level change warning signal, microseismic warning signal, support resistance warning signal, and water level change speed warning signal, respectively. 1 means that the indicator reaches the warning threshold, and 0 means that the indicator does not reach the warning threshold; RH t and RH 0 They represent the water level change at time t and its warning threshold respectively; v t and v 0 Respectively represent the water level change speed and its warning threshold on that day; ME t and ME 0 They represent the comprehensive early warning index of microseismic earthquakes and their early warning thresholds at time t; MP t and MP 0 They represent the comprehensive early warning index of the support resistance and its early warning threshold at time t respectively;

[0043] When the comprehensive warning indicator EWI ≥ 1, the disaster warning is activated.

[0044] Compared with the prior art, the coal mine roof delamination water inrush warning method based on multi-factor indicators provided by the present invention fully considers the evolution mechanism of delamination water inrush, establishes a mechanical model of the delamination structure of the overburden rock that can accumulate water, analyzes the mechanical mechanism of the formation of the water guide channel during the advancement of the working face, and on this basis comprehensively considers factors such as water level under different engineering geological parts, micro-seismicity, and support resistance to establish a multi-factor comprehensive warning index, which can accurately warn of delamination water inrush in the mining working face, and can provide more guiding reference for timely disaster avoidance during actual production in the mine. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] In order to more clearly illustrate the embodiments of this specification or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in the embodiments of this specification. For ordinary technicians in this field, other drawings can also be obtained based on these drawings.

[0046] Figure 1 A schematic diagram of the structure of the overburden rock water-accumulating detached layer, the upper rock layer and the lower aquiclude provided by the present invention;

[0047] Figure 2 Mechanical model of fixed-support beam of upper rock layer and lower water-proof layer provided by the present invention;

[0048] Figure 3 A schematic diagram of the early warning principle of coal mine roof separation and water inrush based on multi-factor indicators provided by the present invention;

[0049] Figure 4 The invention provides a curve of the evolution of coal mine roof separation water inrush warning indicators over time based on multiple factor indicators. DETAILED DESCRIPTION

[0050] In order to make the purpose, technical scheme and advantages of the embodiments of the present application clearer, the technical scheme in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, rather than all of the embodiments. It should be noted that, in the absence of conflict, the embodiments in the present application and the features in the embodiments can be combined, separated, interchanged and / or rearranged with each other. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of this application.

[0051] In the accompanying drawings, the size and relative size of components may be exaggerated for clarity and / or descriptive purposes. When the exemplary embodiments may be implemented differently, a specific process sequence may be performed in a different order than described. For example, two successively described processes may be performed substantially simultaneously or in an order opposite to the order described. In addition, the same reference numerals represent the same components.

[0052] The terms used here are for the purpose of describing specific embodiments, and are not intended to be restrictive. As used here, unless the context clearly indicates otherwise, the singular forms "one (kind, person)" and "said (the)" are also intended to include plural forms. In addition, when the terms "comprise" and / or "include" and their variations are used in this specification, it is explained that there are stated features, integral bodies, steps, operations, parts, assemblies and / or their groups, but it is not excluded that there are or add one or more other features, integral bodies, steps, operations, parts, assemblies and / or their groups. It should also be noted that, as used here, the terms "substantially", "approximately" and other similar terms are used as approximate terms and not as degree terms, so that they are used to explain the inherent deviations of the measured values, calculated values ​​and / or the values ​​provided that will be recognized by those of ordinary skill in the art.

[0053] Example 1

[0054] A specific embodiment of the present invention discloses a coal mine roof separation water inrush warning method based on multi-factor indicators, comprising the following steps:

[0055] S1. Collect stratigraphic data of the mining area / working face, establish an engineering geological model of the mining overburden, and identify the locations of the water-accumulating strata, upper rock strata and lower impermeable layers of the mining overburden.

[0056] S11. Collect geological data of the mining area / working face and establish an engineering geological model of the overburden rock. The collected geological data include exploration drilling data, hydrogeological data, etc. According to the information of the mined coal seam, lithology, aquifer, etc., an engineering geological model of the overburden rock is established based on the geological data collected above.

[0057] In this embodiment, the "engineering geological model of mining overburden" refers to a simplified model of overburden that clarifies coal seam mining information (including coal seam thickness, coal seam burial depth, mining area / working face width) and the spatial location of water-accumulating strata and near-field roof rock layers (distance from the coal seam). To establish an engineering geological model of mining overburden, it is first necessary to clarify the strata, thickness, lithology, structure, and burial depth of each rock layer based on the hydrogeological data of the mining area / working face and the comprehensive stratigraphic columnar diagram and stratigraphic profile diagram of the mining area / working face, and identify the coal seam, the main aquiclude, and the aquiclude.

[0058] S12. Obtain the engineering geological condition parameters of the overburden rock at the working face through on-site investigation, coring, indoor testing and other methods, and determine the specific locations of the water-accumulating stratum, upper rock stratum and lower aquiclude based on the engineering geological condition parameters of the overburden rock at the working face.

[0059] like Figure 1 As shown, the "water-accumulating stratum" in this embodiment refers to the stratum space that provides a direct water source for stratum water inrush. A stratum that can accumulate water needs to meet two basic conditions: first, there is a combined structure of an upper rock layer and a lower aquiclude, so that the upper rock layer and the lower aquiclude settle unevenly during the mining process; and the lower aquiclude does not develop conductive cracks during the bending and deformation process, and still maintains a certain aquiclude. At this time, a temporarily closed stratum can be formed between the upper rock layer and the lower aquiclude, providing space for stratum water accumulation. Second, the closed stratum space is located just near the aquifer. Generally, the stratum that can accumulate water is located in the water-bearing bottom plate or inside the aquifer, ensuring that during the development of the stratum, the groundwater stored in the aquifer continues to converge into the closed stratum space to form a stratum water body, that is, a direct water source for stratum water inrush.

[0060] The "lower aquiclude" in this embodiment refers to a relatively soft rock layer located below the water-absorptive layer, which plays a water-isolating role. By way of example, the lower aquiclude includes low-permeability aquiclude rock layers such as mudstone, mudstone sandstone, siltstone, and shale; the "upper rock layer" refers to a relatively hard rock layer located above the water-absorptive layer. The upper rock layer is generally a water-filled aquifer, and the rock types are fine sandstone, medium sandstone, coarse sandstone, conglomerate, etc.

[0061] S121. Obtain the engineering geological condition parameters of the overburden of the working face through methods such as on-site investigation, coring, and indoor testing. The engineering geological condition parameters of the overburden of the working face include basic physical and mechanical parameters of the rock, rock layer thickness, distance from the coal seam, and length and width of the working face. It should be noted that if the lower aquiclude and the upper rock layer are composite layers composed of different lithologies, the average value of the physical and mechanical parameters of each rock layer is taken as the calculation parameter of the fracture criterion.

[0062] S122. Based on the established mining-induced overburden engineering geological model, the steps of calculating and determining the specific locations of the water-accumulating stratum, the upper rock stratum, and the lower aquiclude include:

[0063] S1221. Divide the rock formations into coordinated deformation and fracture groups according to the following discriminant formula:

[0064]

[0065] Among them, Λ i and Λ i+1 is the elastic modulus of the i-th and i+1-th layers; Ψ i and i+1is the thickness of the i-th and i+1-th rock layers. If the adjacent rock layers satisfy the discriminant relationship of formula (1), they are classified as the same rock group, otherwise, they do not belong to the same rock group.

[0066] S1222. The interface between adjacent rock groups is regarded as the location of the separation layer; according to the measured fracture-mining ratio of the mine, the height H of the traditional water-conducting fracture zone during the early warning working face mining is calculated according to the following formula: w :

[0067] H w =δ×M(2)

[0068] In the above formula, δ is the measured cracking ratio of the mine, and M is the mining height of the working face.

[0069] S1223. Based on the height of the traditional water-conducting fracture zone during the early warning working face mining, determine the positions of all strata within the bedrock range above the traditional water-conducting fracture zone; screen out water-accumulating strata based on the position of the aquifer: wherein the water-accumulating strata are located in the water-bearing bottom plate or inside the aquifer, and the rock group below the water-accumulating strata and above the water-conducting fracture zone is regarded as the lower aquiclude, and the rock group above the water-accumulating strata is regarded as the upper rock layer.

[0070] S2. Based on the fracture criteria of the upper rock strata and the lower aquiclude during mining, determine the different fracture sequences of the upper rock strata and the lower aquiclude under mining action; and based on the different fracture sequences of the upper rock strata and the lower aquiclude under mining action and the water inrush during mining of the working face, select microseismic warning indicators, construct a multi-factor microseismic warning model for water inrush from coal mine roof strata, and calculate to obtain the microseismic comprehensive warning signal.

[0071] S21. Based on the basic mechanical model of the lower aquiclude and the upper rock stratum, the maximum principal stress and the minimum principal stress under the action of rock mining are calculated; and based on the Hooke-Brown criterion, the criterion for the damage of the upper rock stratum and the lower aquiclude is obtained.

[0072] S211. Establish the basic mechanical model of the lower aquiclude and upper rock strata.

[0073] First, in the initial deformation stage of the rock formation, since the deformation range is small, it can be assumed that the rock formation undergoes only elastic deformation, which satisfies the elastic mechanics theory. Due to the pressure transmission effect of the overlying stratum water body, the load on the lower impermeable layer can be regarded as a uniformly distributed load, and further equivalent to a concentrated force. The mechanical model is shown in the attached figure. Figure 2 Based on elastic mechanics, the normal stress in the x-direction of the lower aquiclude is:

[0074]

[0075] The calculation formula for the maximum deflection of the fixed beam (at x = 0) is:

[0076]

[0077] And the maximum deformation of the rock layer is expressed by the following formula:

[0078] w(0)=M-(K p -1)h n (5)

[0079] From this we can get:

[0080]

[0081] Then we can obtain:

[0082]

[0083] Then, the calculation formula of the maximum principal stress and the minimum principal stress under the mining action of the rock formation is obtained as follows:

[0084]

[0085] Δ 1 and Δ 3 are the maximum principal stress and minimum principal stress under the action of rock mining; α is the exposed length of the rock layer, which can be approximated as the width of the working face; β is the thickness of the upper rock layer or the lower impermeable layer; Λ is the elastic modulus of the upper rock layer or the lower impermeable layer; χ is the bending stiffness of the elastic beam section; q is the total load on the rock layer; x, y are the horizontal and vertical coordinates of the model respectively; M is the mining height of the working face; K p h is the rock layer expansion coefficient, which is 1.03-1.035; n It is the distance between the bottom plate of the upper rock layer or lower aquiclude and the top plate of the coal seam.

[0086] S212. Assuming shear failure of the rock formation, obtain the rock formation failure identification index based on the Hooke-Brown criterion.

[0087] The Hooke-Brown criterion is:

[0088]

[0089] Among them, Δ 1 and Δ 3 are the maximum principal stress and minimum principal stress under the mining action of rock formation; σ c is the uniaxial compressive strength of rock; m, s, a are the Hooke-Brown criterion constants.

[0090] Based on the Hooke-Brown criterion, the rock formation failure judgment index J is obtained as follows:

[0091]

[0092] Substituting formula (8) into formula (10), the breaking criterion of the upper rock layer and the lower aquiclude is obtained as follows:

[0093]

[0094] Among them, when J(x,y)>1, the rock layer is broken.

[0095] S213. According to the fracture criteria of the upper rock strata and the lower aquiclude, determine the different fracture sequences of the upper rock strata and the lower aquiclude under mining action.

[0096] S22. Based on the different fracture sequences of the upper rock layer and the lower impermeable layer under mining action and the water inrush during the working face mining, microseismic early warning indicators are selected, a microseismic early warning model is constructed, and the microseismic early warning signal is calculated based on the constructed microseismic early warning indicator model.

[0097] Analyzing the microseismic signals of the overburden (development of water-conducting channels) is of great significance for the early warning of water inrush from the stratum. According to the description in step S1, since the lower impermeable layer is mainly muddy soft rock and the upper rock layer is mainly gravel rock, the crack-structure evolution law of the upper rock layer and the lower impermeable layer of the overburden under different engineering geological conditions is different, which further leads to the large difference in the response characteristics of different microseismic early warning indicators during the approaching water inrush of each working face. Therefore, if the microseismic signal is used to warn the water inrush from the stratum of the working face, first use the breaking criteria of the upper rock layer and the lower impermeable layer obtained in step S21 to analyze the breaking conditions of the lower impermeable layer and the upper rock layer of the overburden, and on this basis, select, process and integrate multiple microseismic early warning indicators in a targeted manner to obtain the microseismic precursor information of mud-sand water inrush, which provides a reference for disaster forecasting and early warning during mining.

[0098] First, select the total number of times per day, total daily energy, average energy per time, >10 3 J Energy Daily Occurrence Times, <10 3 Five basic parameters such as the number of J energy daily occurrences are used as microseismic early warning indicators. Specifically, according to the different fracture sequences of the upper rock layer and the lower aquifer under mining action, microseismic early warning indicators are selected and a microseismic early warning model is constructed. Specifically, the following three situations are included:

[0099] Case 1: If the water inrush during the mining of the working face is caused by the breaking of the upper rock layer, that is, the breaking criterion J of the lower impermeable layer is ≤1 and the breaking criterion J of the upper rock layer is >1. In this case, the microseismic early warning indicators are selected as the daily total energy TE, the average energy per time E and the value greater than 10 3 JTotal number of microseismic events per dayF 1 , the first microseismic comprehensive early warning model is obtained as follows:

[0100] ME 1=sta(TE)·sta(E)·sta(F) (12)

[0101] Among them, sta() means to standardize the indicators.

[0102] In general, data standardization is to select the maximum and minimum values ​​for a set of known data for calculation; however, the microseismic comprehensive early warning is calculated based on the microseismic data generated in real time by the mining face. In other words, the microseismic data in the unmined area is unknown, so it is impossible to reasonably define the sample capacity for obtaining the maximum and minimum values. In order to unify the microseismic early warning of the entire mine (mining area), according to the change scale of each microseismic early warning indicator of the mined working face, the daily total energy TE, the average energy E per time, and the maximum and minimum values ​​greater than 10 are selected. 3 JTotal number of microseismic events per dayF 1 The standardized scales (minimum and maximum values) are (0,1000), (0,10), and (0,30) respectively.

[0103] Case 2: If the water inrush during the mining of the working face is caused by the breaking of the lower impermeable layer, that is, the breaking criterion J of the lower impermeable layer is greater than 1 and the breaking criterion J of the upper rock layer is less than 1. In this case, the microseismic early warning indicators are the total number of times per day TN, the average energy per time E and less than 10 3 JTotal number of microseismic events per dayF 2 , the second microseismic comprehensive early warning model is obtained as follows:

[0104]

[0105] According to the change scale of each microseismic early warning index of the mined working face, the daily total number TN and less than 10 3 JTotal number of microseismic events per dayF 2 The standardized scales (minimum and maximum values) are (0,100) and (0,30) respectively.

[0106] Case 3: If the water inrush during the mining of the working face is caused by the coordinated breaking of the lower aquiclude and the upper rock layer, that is, the breaking criterion J of the lower aquiclude is greater than 1 and the breaking criterion J of the upper rock layer is greater than 1. In this case, the microseismic early warning indicators are selected as the total number of times per day TN and the total energy per day TE, and the third microseismic comprehensive early warning model is obtained as follows:

[0107] ME 3 =sta(TN)·sta(TE) (14)

[0108] Based on the three microseismic comprehensive early warning models obtained above, the microseismic early warning signal E is obtained as follows:

[0109] E= <ME t -ME 0 >(15)

[0110] Among them, < > is the discriminant function,

[0111] In the formula, ME t represents the comprehensive early warning index of microseismic events at time t, ME 0 is the microseismic warning threshold. E is 1, indicating that the indicator reaches the warning threshold, and 0 indicates that the indicator does not reach the warning threshold.

[0112] S3. The water level evolution type during the evolution of the working face roof absorptive water is divided into a water level periodic fluctuation type and a water level continuous drop type. A water level early warning model for the water level periodic fluctuation type and the water level continuous drop type is constructed. The water level early warning signals for the water level periodic fluctuation type and the water level continuous drop type are obtained by calculation according to the water level early warning model.

[0113] S31. The judgment conditions for water level periodic fluctuation type and water level continuous decline type are as follows:

[0114] (1) For the water level periodic fluctuation type: during the entire mining period, there is only one water-logged stratum, and only one adjacent rock layer in the aquifer meets the following judgment conditions:

[0115]

[0116] The remaining adjacent rock layers all meet the following judgment conditions:

[0117]

[0118] (2) For the type of continuous water level decline: During the entire mining period, multiple water-accumulated strata are formed at the bottom and inside the aquifer, and there are two or more adjacent rock layers in the aquifer that meet the following conditions:

[0119]

[0120] Among them, Λ i-1 ,Λ i and Λ i+1 is the elastic modulus of the i-1, i and i+1 layers; i-1 ,Ψ i and i+1 is the thickness of the i-1, i and i+1 layers.

[0121] S32. For the periodic fluctuation of water level, the water level change is selected as the early warning indicator; for the continuous drop of water level, the water level change and the speed of water level change are selected as early warning indicators.

[0122] The calculation formula of water level change is as follows:

[0123] RH t =L t -L0 (16)

[0124] The water level change rate calculation formula is as follows:

[0125] v d =L d -L d-1 (20)

[0126] Among them, L t is the water level at time t during the mining period of the working face, L 0 L is the initial water level when the working face starts mining; d-1 and L d They are the aquifer water level at 12:00 the previous day and the water level at 12:00 the current day. t and v d A positive number indicates that the water level is rising, RH t and v d A negative number indicates a drop in water level.

[0127] S33. Based on the water level change warning discrimination model, a water level change warning signal L is calculated; based on the water level change speed warning discrimination model, a water level change speed warning signal V is calculated.

[0128] Among them, the water level change warning discrimination model is:

[0129] L= <RH 0 -RH t > (21)

[0130] In the above formula, < > is the discriminant function, RH t Represents the water level change at time t; RH 0 is the water level change warning threshold; L is 1, indicating that the indicator has reached the warning threshold; 0, indicating that the indicator has not reached the warning threshold. Preferably, the water level change warning threshold RH 0 It is -10~-20m.

[0131] The water level change speed warning discrimination model is:

[0132] V= <v 0 -v d >(22)

[0133] In the above formula, <> is the discriminant function, v d Indicates the speed of water level change; v 0 is the water level change rate warning threshold; V is 1, indicating that the indicator reaches the warning threshold; 0, indicating that the indicator does not reach the warning threshold. Preferably, the water level change rate warning threshold is -1 m / d.

[0134] S4. A support resistance warning index model is established based on the support resistance warning index of delamination water inrush, and a support resistance warning signal is obtained by calculation.

[0135] S41. Obtain support resistance warning indicators for delamination water inrush.

[0136] The deformation and fracture of the lower aquiclude leads to large-cycle pressure on the working face. When the lower aquiclude breaks during a certain large-cycle pressure, delamination water inrush occurs on the working face. For the strong support resistance warning of delamination water inrush on the working face, it is necessary to consider the support resistance and the spatial distribution law of the lower aquiclude of the working face at the same time, establish the support resistance warning index from the perspective of the deformation and fracture of the lower aquiclude, and warn of delamination water inrush on the working face. Equivalent the direct top load and the old top force to the rock mass with a support resistance influence height of H, the support resistance warning index MP of delamination water inrush is calculated according to the following formula:

[0137]

[0138] In the above formula, γ is the average volume force of the rock mass, Z is the resistance at the end of the support cycle, S is the top beam area, H lc It is the distance between the roof of the lower aquiclude and the roof of the coal seam.

[0139] S42. Construct a support resistance warning model based on the support resistance warning index of delamination water inrush, and calculate the support resistance warning signal based on the support resistance warning model.

[0140] The support resistance warning model is:

[0141] P= <MP t -MP 0 > (18)

[0142] In the above formula, <> is the discriminant function, MP t It indicates the early warning index of the support resistance at time t; MP 0 is the stent resistance warning threshold; P is 1, indicating that the indicator reaches the warning threshold; 0, indicating that the indicator does not reach the warning threshold. Preferably, the threshold of the stent resistance warning signal is 0.95.

[0143] S5. Based on the microseismic warning signal obtained in step S2, the water level warning signal obtained in step S3, and the support resistance warning signal obtained in step S4, a comprehensive warning model is established, and a multi-factor comprehensive warning indicator result is obtained based on the comprehensive warning model.

[0144] Based on the evolution mechanism of delamination water inrush under different engineering geological conditions, combined with the significance of microseismic early warning signals, water level early warning signals, and support resistance early warning signals, a schematic diagram of the principle of comprehensive early warning for complex disasters is proposed, such as Figure 3 shown.

[0145] The water level drop before the water inrush essentially reflects the filling of the abscission layer with water, that is, the process of the formation of the direct water source. Only when the water level change reaches the warning value, it means that the "direct water source" formed under the action of mining has reached the disaster-causing level, and the "water level warning" should be activated. The abnormal microseismic warning index is caused by the breaking of the overburden rock, reflecting the formation of water-conducting fissures. When the water level change and the microseismic comprehensive index reach the warning value at the same time, it is still impossible to conclude that the water-conducting channel has been formed in the abscission layer that can accumulate water.

[0146] The support resistance warning signal obtained in step S4 reflects the support resistance index, which can directly reflect the deformation and breakage degree of the lower aquiclude. The abnormal support resistance index indicates that the self-stabilizing ability of the lower aquiclude is weakened, and the force on the support is increased. Therefore, the microseismic and support resistance are combined to reflect the formation of a water-conducting channel in the stratum where water can accumulate: when the combined indicators of microseismic and support resistance reach the warning value, that is, the mining overburden has formed a water-conducting channel in the stratum where water can accumulate, the "water-conducting channel warning" should be turned on.

[0147] In addition, the speed of water level change can reflect the speed of abscission formation (sinking of lower aquiclude) to a certain extent, and indirectly reflect the deformation and breakage of the lower aquiclude (development of water burst channels). For the water level type identified in S3, for working faces with continuous water level drop, the "water channel warning" can also be activated when the water level change speed reaches the warning value, provided that the water level change reaches the warning value.

[0148] Based on the above analysis, a comprehensive warning model is established based on the microseismic warning signal obtained in step S2, the water level warning signal obtained in step S3, and the support resistance warning signal obtained in step S4 as follows:

[0149] EWI=L·(E·P+V)(19)

[0150] In the above formula, L, E, P, and V represent the water level change warning signal, microseismic warning signal, support resistance warning signal, and water level change speed warning signal, respectively. 1 means that the indicator reaches the warning threshold, and 0 means that the indicator does not reach the warning threshold; RH t and RH 0 They represent the water level change at time t and its warning threshold respectively; v t and v 0 Respectively represent the water level change speed and its warning threshold on that day; ME t and ME 0 They represent the comprehensive early warning index of microseismic earthquakes and their early warning thresholds at time t; MP t and MP 0 They respectively represent the comprehensive warning index of the support resistance at time t and its warning threshold.

[0151] When the comprehensive warning indicator EWI ≥ 1, the disaster warning is activated.

[0152] Actual project cases

[0153] Taking Cuimu Coal Mine in Yonglong Mining Area of ​​Ordos Basin as an example, the coal mine roof separation and water inrush warning method based on multi-factor indicators in the above embodiment 1 is applied to a working face of Cuimu Coal Mine.

[0154] 1. According to step S1, the locations of the mining-induced overburden water-accumulating strata, the upper rock strata and the lower aquiclude are identified.

[0155] This embodiment takes a working face of Cuimu Coal Mine as an example, obtains comprehensive stratigraphic conditions by taking stratigraphic data, and divides the comprehensive stratigraphic rock group, as shown in Table 1. According to the engineering hydrogeological conditions of Cuimu Coal Mine, the coarse sandstone at the bottom of the Cretaceous Luohe Formation aquifer can be regarded as the upper rock layer, and the mudstone layer of the Jurassic Anding Formation is the lower impermeable layer. The working face width is 165m, the strike length is 800m, and the average mining height is 7m.

[0156] Table 1 Stratum conditions of the 21308 working face of Cuimu Coal Mine

[0157]

[0158] 2. Select and calculate microseismic early warning indicators according to step S2

[0159] According to the calculation of the fracture criterion F of the lower impermeable layer and the upper rock layer, it is determined that the 21308 working face meets the situation 1 in step S22. Therefore, the daily total energy TE, the average energy per time E and the value greater than 10 are selected for this working face. 3 JTotal number of microseismic events per dayF 1 As an indicator for participating in microseismic early warning.

[0160] 3. According to step S3, water level type identification and water level warning indicator selection are performed

[0161] Substituting the parameters in Table 2 into formula (11), we can obtain the lower aquiclude breaking criterion F 1 It is always less than 1, and the upper rock layer is broken. The coarse-grained sandstone with an average thickness of 97.05m and an average thickness of 18.06m in the aquifer satisfies formula (18), proving that there are multiple strata of water accumulation around the aquifer, which belongs to the type of continuous water level decline. Therefore, the water level change and water level change speed are selected as water level warning indicators.

[0162] Table 2 Calculation parameters of the fracture criterion for the upper rock layer and the lower aquiclude

[0163]

[0164] 4. Calculate the support resistance index according to step S4

[0165] 5. Calculate the results of the multi-factor comprehensive early warning indicators and issue early warnings according to step S5

[0166] According to the relationship between water inrush near the separation layer and the response of various indicators under different engineering geological conditions analyzed in the previous article, the various warning indicators and their warning thresholds corresponding to the working face are determined, and the water level change, microseismic, support resistance, water level change speed warning signals (L, E, P, V) and comprehensive warning indicators EWI during the working face mining period are obtained. For the convenience of comparison, the y-offset stacked line diagram of the L, E, P, V and EWI curves is drawn, as shown in Figure 4 As shown. It can be seen that there is no strict correspondence between L, E, P, V and whether the working face is close to water inrush. That is, during the period of water inrush, L, E, P, V are often greater than 0, indicating that the water level change, microseismic, support resistance, and water level change speed indicators have reached the warning threshold. Moreover, only when EWI is close to water inrush is EWI>0, which proves that the comprehensive warning indicator EWI proposed in the present invention can accurately warn the water inrush from the delamination of the mining working face under different engineering geological conditions before the disaster.

[0167] Compared with the prior art, the coal mine roof delamination and water inrush warning method based on multi-factor indicators provided in this embodiment fully considers the evolution mechanism of delamination and water inrush, establishes a mechanical model of the delamination structure of the overburden rock that can accumulate water, analyzes the mechanical mechanism of the formation of water conduction channels during the advancement of the working face, and on this basis comprehensively considers factors such as water level under different engineering geological parts, micro-seismicity, and support resistance to establish a multi-factor comprehensive warning index, which can accurately warn of delamination and water inrush in the mining working face, and can provide more guiding reference for timely disaster avoidance during actual production in the mine.

[0168] The specific implementation methods described above further illustrate the purpose, technical solutions and beneficial effects of the present application in detail. It should be understood that the above description is only the specific implementation method of the present application and is not intended to limit the scope of protection of the present application. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present application should be included in the scope of protection of the present application.

Claims

1. A coal mine roof separation water inrush warning method based on multi-factor indicators, characterized in that: include: S1. Establish an engineering geological model of the mining overburden to identify the locations of the water-accumulating strata, upper rock layers and lower aquicludes of the mining overburden; S2. Based on the fracture criterion of the upper rock layer and the lower aquiclude during mining, determine the different fracture sequences of the upper rock layer and the lower aquiclude under mining action; select microseismic early warning indicators, construct a multi-factor microseismic early warning model for water inrush from the roof of the coal mine, and obtain a comprehensive microseismic early warning signal; S3. Based on the water level evolution type during the evolution of the roof absorptive water of the working face, a water level warning model is constructed to obtain a water level warning signal; S4. Establish a support resistance warning indicator model based on the support resistance warning indicator of delamination water inrush, and obtain a support resistance warning signal; S5. Based on the microseismic comprehensive warning signal, the water level warning signal and the support resistance warning signal, a comprehensive warning model is established to obtain a multi-factor comprehensive warning indicator result; In step S2, the breaking criteria of the upper rock layer and the lower aquiclude are: In the above formula, To reveal the length of the rock formation; is the thickness of the upper rock layer or the lower aquiclude; is the elastic modulus of the upper rock layer or the lower aquiclude; is the bending stiffness of the elastic beam section; x, y are the horizontal and vertical coordinates of the model respectively; To mine high for the working face; is the rock formation expansion coefficient; It is the distance between the upper rock layer or the lower aquiclude floor and the coal seam roof; is the uniaxial compressive strength of rock; m, s, a are the Hooke-Brown criterion constants; Among them, when J (x, y) > 1, the rock layer is broken.

2. The method for early warning of water inrush from coal mine roof separation based on multi-factor indicators according to claim 1 is characterized in that: In step S2, microseismic early warning indicators are selected based on the different fracture sequences of the upper rock layer and the lower impermeable layer under the mining action and the water inrush situation during the mining of the working face.

3. The method for early warning of water inrush from coal mine roof separation based on multi-factor indicators according to claim 1 is characterized in that: In step S3, the water level evolution type during the evolution of the working face roof absorptive water is divided into a water level periodic fluctuation type and a water level continuous drop type, and a water level warning model of the water level periodic fluctuation type and the water level continuous drop type is constructed to obtain a water level warning signal of the water level periodic fluctuation type and the water level continuous drop type.

4. The method for early warning of water inrush from coal mine roof separation based on multi-factor indicators according to claim 3 is characterized in that: In step S3, the judgment conditions for water level periodic fluctuation type and water level continuous decline type are as follows: For the water level periodic fluctuation type: during the entire mining period, there is only one water-absorbed layer, and only one adjacent rock layer in the aquifer meets the following judgment conditions: The remaining adjacent rock layers all meet the following judgment conditions: as well as For the type of continuous water level decline: During the entire mining period, multiple water-accumulated strata are formed at the bottom and inside of the aquifer, and there are two or more adjacent rock layers in the aquifer that meet the following conditions: In the above formula, , and For the i-1 , i and i+1 elastic modulus of the rock layer; , and For the i-1 , i and i+1 The thickness of the rock layer.

5. The method for early warning of water inrush from coal mine roof separation based on multi-factor indicators according to claim 3 is characterized in that: For the water level periodic fluctuation type, the water level change is selected as the early warning indicator; For the type of continuous water level drop, the water level change amount and water level change speed are selected as early warning indicators.

6. The method for early warning of water inrush from coal mine roof separation based on multi-factor indicators according to claim 5, characterized in that: In step S3, based on the water level change warning discrimination model, a water level change warning signal L is calculated; based on the water level change speed warning discrimination model, a water level change speed warning signal V is calculated; Among them, the water level change warning discrimination model is: The water level change speed early warning discrimination model is: In the above formula, in the above formula, is the discriminant function, ; express The water level change at each moment; is the water level change warning threshold; L and V are 1, indicating that the indicator has reached the warning threshold; L and V are 0, indicating that the indicator has not reached the warning threshold; Indicates the speed of water level change; It is the water level change speed warning threshold.

7. The method for early warning of water inrush from coal mine roof separation based on multi-factor indicators according to claim 1, characterized in that: In step S4, the support resistance warning index of delamination water inrush is calculated according to the following formula: : In the above formula, is the average volume force of the rock mass, is the end-cycle resistance of the stent; is the top beam area, is the distance between the roof of the lower aquiclude and the roof of the coal seam; H is the height affected by the support resistance.

8. The method for early warning of water inrush from coal mine roof separation based on multi-factor indicators according to claim 7, characterized in that: The support resistance early warning model is: In the above formula, is the discriminant function, ; express Always keep the support resistance warning indicator; is the warning threshold of the support resistance; P is 1, indicating that the indicator reaches the warning threshold; 0 indicates that the indicator does not reach the warning threshold.

9. The method for early warning of water inrush from coal mine roof separation based on multi-factor indicators according to claim 1, characterized in that: In step S5, the comprehensive early warning model is: In the above formula, , , , ; , , , They represent the water level change warning signal, microseismic comprehensive warning signal, support resistance warning signal, and water level change speed warning signal respectively. 1 means that the indicator reaches the warning threshold, and 0 means that the indicator does not reach the warning threshold; and Respectively The water level change at each moment and its warning threshold; and They represent the speed of water level change and its warning threshold on that day respectively; and Respectively Comprehensive early warning indicators of microseismic events and their early warning thresholds; and Respectively Comprehensive early warning index of support resistance at all times and its early warning threshold; When the comprehensive early warning indicators Activate disaster warning.

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