A method for predicting the duration of surface movement in coal seam mining

Abstract

The present application relates to a kind of coal seam mining surface movement continuation time prediction method, can predict the surface movement continuation time caused by coal seam mining under different geological conditions at different mining speed, the coal seam mining surface movement continuation time prediction model parameter proposed in the present application can be predicted only according to coal seam thickness, mining depth and working face mining speed and other parameters, without a large number of field monitoring data, easy for field application.The movement continuation time predicted by the method is a theoretical model established by rigorous theoretical derivation, contains few parameters, and the parameters are easy to determine, the predicted value is basically consistent with the field monitoring value, and the prediction accuracy is high.

Description

TECHNICAL FIELD

[0001] The present application relates to a coal seam mining surface movement duration prediction method. BACKGROUND

[0002] The surface movement and deformation caused by coal mining is a complex time and space problem, and the total sum of the time experienced by the surface subsidence is called the surface movement duration.

[0003] At present, the empirical formula given in the "three-under" coal mining regulations is mostly used to calculate the surface movement duration, but the formula is not strong in pertinence, and the calculation result is large. The empirical prediction model is not uniform in form, which is not conducive to popularization and application. The parameter determination method of the empirical model is inconsistent, so that the model parameters estimated by each mining area are quite different, and the predicted surface movement duration is quite different from the actual situation, and the prediction accuracy is low. The empirical prediction model considers fewer factors affecting the surface movement duration, and it is difficult to fully reflect the influence of factors such as coal seam mining height, mining depth and coal seam mining speed. SUMMARY

[0004] The technical problem to be solved by the present application is to provide a coal seam mining surface movement duration prediction method with fewer parameters, easy-to-determine parameters and high prediction accuracy.

[0005] To solve the above problems, the technical scheme adopted by the present application is:

[0006] A coal seam mining surface movement duration prediction method, the key technology of which lies in that the prediction method comprises the following steps:

[0007] a. Establish a prediction function of the surface subsidence caused by coal seam mining:

[0008]

[0009] In formula (1), W(t) is the instantaneous subsidence value of a certain point on the surface, W0 is the final subsidence value of a certain point on the surface, and C is the time influence parameter of the improved model.

[0010] b. Establish a coal seam mining surface movement duration prediction model according to formula (1):

[0011]

[0012] In formula (2), T2 is the surface movement duration.

[0013] c. Calculate the time influence parameter C according to the following formula (3):

[0014]

[0015] H is the average mining depth; v is the mining speed of the coal seam; the value of n is 1.2-1.4;

[0016] d, obtaining the values of W0, H and v, and substituting them into formula (3) and formula (2) respectively to calculate the surface movement duration T2.

[0017] Further, the W0 is obtained by monitoring or calculated according to the following formula (4)

[0018] W0=mq cosα (4)

[0019] In formula (4), m is the thickness of the coal seam; α is the inclination of the coal seam; q is the subsidence coefficient.

[0020] Further, the value of n in formula (3) is selected as 1.4.

[0021] Further, the formula (1) in step a is obtained by the following steps:

[0022] The following differential equation is established to describe the dynamic subsidence process of the surface:

[0023]

[0024] Solving formula (1-1) obtains the following formula:

[0025]

[0026] Integrating both sides of formula (1-2) obtains the following formula:

[0027]

[0028] In formula (1-3), A is an integral constant; t is the real-time time, and the unit is day;

[0029] Simplifying formula (1-3) obtains the following formula:

[0030]

[0031] In formula (1-4), B is an integral constant;

[0032] Taking the moment when the subsidence amount reaches 10mm as the subsidence starting moment, that is, t=0, according to formula (1-4), there is

[0033] B=100W0-1 (1-5)

[0034] Substituting formula (1-5) into formula (1-4) obtains the formula (1).

[0035] Further, the formula (2) in step b is obtained by the following steps:

[0036] Let the time corresponding to the end of the ground movement be T2, and the ground subsidence amount W(T2) at this time is obtained according to formula (1):

[0037]

[0038] Assuming that each month is 30 days, the ground subsidence amount W(T2-180) at 6 months before the end of the ground movement is obtained according to formula (2-1):

[0039]

[0040] According to formula (2-2) and the definition of the ground movement duration, the following relationship needs to be met between the two subsidence amounts W(T2-180) and W(T2):

[0041]

[0042] When the difference between the subsidence amount at T2 and the subsidence amount at T2-180 is exactly 30 mm, T2 is the ground movement duration, and since the unit of the predicted subsidence amount difference on the left side of formula (2-3) is m, and the unit on the right side is mm, formula (2-3) can be converted to:

[0043]

[0044] The above formula (2-4) is simplified to obtain formula (2).

[0045] Further, the determination method of the model parameter C is as follows:

[0046] According to the probability integral theory, under the condition of mining of a near-horizontal coal seam, when the mining range reaches the critical value of sufficient mining, the maximum ground subsidence amount is approximately equal to 0.98W0, assuming that the mining speed is v, and the critical size of the goaf is L f , then the critical time of sufficient mining can be expressed as Combined with formula (1), the calculation formula of the model influence parameter C is obtained as:

[0047]

[0048] When the working face advancing distance is nH, sufficient mining is reached, and therefore L f is:

[0049] L f = nH (3-2)

[0050] Formula (3) for calculating the model influence parameter C is obtained by substituting formula (3-2) into formula (3-1).

[0051] The beneficial effects produced by the above technical solution are:

[0052] The coal seam mining surface movement duration time prediction method provided by the application has the advantages that the movement duration time is a theoretical model established through rigorous theoretical derivation, contains few parameters, and the parameters are easy to determine, the predicted value is basically consistent with the field monitoring value, and the prediction accuracy is high; the parameters of the coal seam mining surface movement duration time prediction model proposed by the application can be predicted only according to parameters such as the coal seam thickness, mining depth and working face mining speed, without the need for a large amount of field monitoring data, and the application is convenient. BRIEF DESCRIPTION OF DRAWINGS

[0053] Figure 1 is a coal mining stratum distribution schematic diagram.

[0054] Figure 2 is a three-stage diagram of surface movement.

[0055] Figure 3 is a surface movement duration time calculation model diagram.

[0056] Figure 4 is a comparison result of predicted values and measured values of the "three-under mining specification".

[0057] Figure 5 is a comparison result of predicted values and measured values of the theoretical model of the application.

[0058] Figure 1 Middle: 1-surface; 2-loose layer; 3-bedrock layer; 4-coal seam; 5-floor. DETAILED DESCRIPTION

[0059] In order to make the purpose, technical scheme and advantages of the application more clear, the application will be clearly and completely described below in combination with specific examples.

[0060] As shown in Figure 1 , the strata from the surface of the coal mine to the bottom are in turn: loose layer 2, bedrock layer 3, coal seam 4 and floor 5, the upper surface of the loose layer 2 is the surface 1, and the surface movement duration time is caused by the bedrock layer 3 movement duration time and the loose layer 2 movement duration time caused by the coal seam 4 mining; the bedrock layer 3 movement duration time is directly caused by the coal seam 4 mining; and the loose layer 2 movement duration time is caused by the bedrock layer 3 movement duration time.

[0061] The coal seam mining surface movement duration time prediction method provided by the application has the advantages that the movement duration time is a theoretical model established through rigorous theoretical derivation, contains few parameters, and the parameters are easy to determine, the predicted value is basically consistent with the field monitoring value, and the prediction accuracy is high; the parameters of the coal seam mining surface movement duration time prediction model proposed by the application can be predicted only according to parameters such as the coal seam thickness, mining depth and working face mining speed, without the need for a large amount of field monitoring data, and the application is convenient.

[0062] a, establish a coal seam mining induced time model to describe the prediction function of surface subsidence:

[0063] The application proposes the instantaneous subsidence speed of a certain point on the surface The product of the difference between the final settlement value W0 of the point and the instantaneous settlement W(t) and the instantaneous settlement W(t) is in direct proportion, thereby establishing the following differential equation to describe the dynamic settlement process of the ground surface:

[0064]

[0065] In the formula, W(t) is the instantaneous settlement value of a point on the ground surface; W0 is the final settlement value of a point on the ground surface; and C is the time influence parameter of the improved model.

[0066] Solving equation (1-1) gives:

[0067]

[0068] Integrating both sides of equation (1-2) gives:

[0069]

[0070] In equation (1-3), A is an integral constant; and t is the real-time time, in days.

[0071] Simplifying equation (1-3) gives:

[0072]

[0073] In equation (1-4), B is an integral constant.

[0074] In the actual monitoring process, it is difficult to accurately determine the critical settlement time of a point on the ground surface, and usually the time when the settlement amount reaches 10 mm is taken as the settlement start time, i.e., t = 0, W(t) = 0.01 m, according to equation (1-4), we have:

[0075] B = 100W0-1 (1-5)

[0076] Substituting equation (1-5) into equation (1-4) gives the function describing the dynamic settlement of the ground surface as

[0077]

[0078] b. According to equation (1), an extended time prediction model of the ground surface movement caused by coal mining is established:

[0079] The ground surface movement and deformation caused by coal mining is a complex time and space problem, such as Figure 2As shown, it is generally considered that the initial stage of surface subsidence is when the surface subsidence reaches 10 mm to the subsidence rate reaches 50 mm / month or 1.7 mm / day, the active stage of surface subsidence is when the subsidence rate is greater than 50 mm / month or 1.7 mm / day, and the subsidence rate is less than 50 mm / month or 1.7 mm / day, and when the cumulative surface subsidence for 6 consecutive months is less than 30 mm, it is the subsidence attenuation stage; the sum of the time experienced in the three stages is called the surface movement duration.

[0080] According to Figure 3 and the definition of the surface movement duration, the time corresponding to the end of the attenuation stage is the surface movement duration. Assuming that the time corresponding to the end of the attenuation stage is T2, according to formula (1), the surface subsidence amount W(T2) at this time is:

[0081]

[0082] Meanwhile, assuming that each month is 30 days, according to formula (1), the surface subsidence amount W(T2-180) in the 6 months before the surface movement is stable is:

[0083]

[0084] According to formula (2-2) and the definition of the surface movement duration, the two subsidence amounts W(T2-180) and W(T2) need to satisfy the following relationship:

[0085]

[0086] In the formula: T2 is the surface movement duration.

[0087] Formula (2-3) requires that the left prediction value is less than or equal to 30 mm, that is, when the difference between the subsidence amount at T2 and the subsidence amount at T2-180 is just 30 mm, it is the surface movement duration. Since the unit of the left prediction subsidence amount difference in formula (2-3) is m, and the unit on the right is mm, in order to unify, formula (2-3) can be converted to:

[0088]

[0089] Simplifying the above formula (2-4) obtains:

[0090]

[0091] Formula (2) is the surface movement duration prediction model, which is based on strict theoretical derivation, and has a more solid theoretical basis than the traditional empirical prediction model, and the model only contains one model parameter C, which is convenient for field application.

[0092] c. Determination of the time influence parameter C:

[0093] According to the probability integral theory, when the mining range reaches the critical value of full mining, the maximum surface subsidence is approximately equal to 0.98W0 under the condition of nearly horizontal coal seam mining. Assuming that the mining speed is v, and the critical size of the goaf is L f , the critical time of full mining can be expressed as The calculation formula of the model influence parameter C is obtained by combining formula (1) as follows:

[0094]

[0095] Since the mining speed is easy to determine, the key to determining the time model parameter is to determine the critical size of the goaf when full mining is reached. A large number of studies have shown that full mining is reached when the working face advancing distance is nH, wherein n is 1.2-1.4, so L f is:

[0096] L f = nH (3-2)

[0097] The calculation formula of the model influence parameter C is obtained by substituting formula (3-2) into formula (3-1) as follows:

[0098]

[0099] According to the actual application situation, n is preferably 1.4.

[0100] The W0 is obtained by monitoring or calculated according to the following formula (4)

[0101] W0 = mqcosα (4)

[0102] In formula (4), m is the thickness of the coal seam; α is the coal seam inclination angle; and q is the subsidence coefficient.

[0103] The following is a prediction example of the surface movement duration time:

[0104] The working face mining parameters of 20 mines are collected and counted, mainly including the average mining depth (H / m), the maximum surface subsidence (W0 / m), the coal seam mining speed (v / (m·d-1)) and the coal seam thickness (m / m), and the results are shown in Table 1. The model parameter C is obtained by substituting the parameters in Table 1 into formula (3), and then the prediction value T2 of the surface movement duration time of the 20 mines is obtained by substituting C into formula (2). At the same time, the surface movement duration time T1 is obtained according to the prediction formula of the “Three-under Mining Specification”, and the prediction results of the two models are shown in Table 2. The T2 and T1 are compared with the monitoring value T M of the surface movement duration time of each mine to verify the accuracy and rationality of the prediction model, and the comparison results are shown in Figure 4 and Figure 5 .

[0105] Table 1 20 mine face parameters

[0106]

[0107]

[0108] Table 2 20 mine surface movement duration prediction values and measured values

[0109]

[0110] From Table 2 and Figure 4 It can be seen that the measured values of the surface movement duration of the 20 mines and the predicted values of the "three-under mining specifications" differ greatly, and the prediction accuracy is low. When the average mining depth is greater than 400m, the minimum difference between the predicted values and the measured values of the surface movement duration is 523 days, and the maximum difference is 1322 days. When the average mining depth is less than 400m, the minimum difference between the predicted values and the measured values of the surface movement duration is 18 days, and the maximum difference is 111 days. It shows that the prediction formula of the "three-under mining specifications" is mainly suitable for the case where the average mining depth is less than 400m, and when the average mining depth exceeds 400m, the prediction accuracy of the formula is low, and the applicability is not strong.

[0111] From Table 2 and Figure 5 It can be seen that the measured values of the surface movement duration of the 20 mines and the predicted values of the surface movement duration prediction model established in this paper basically agree, the prediction accuracy is high, and the rationality and accuracy of the model are verified. At the same time, the average mining depth of the 20 mines changes in the range of 72.5m-920m, the coal seam thickness changes in the range of 1.8m-10.7m, and the mining speed changes in the range of 1.0m / d-9.6m / d, and the prediction results of the surface movement duration prediction model established in this paper are close to the measured results, and the minimum difference between them is only 9 days, which shows that the prediction model has strong applicability and can be used for surface movement duration prediction under different geological conditions and different mining intensities.

[0112] The coal seam mining induced surface movement duration prediction method provided by the application can predict the coal seam mining induced surface movement duration under different geological conditions and different mining speeds, and has the following advantages compared with the existing model:

[0113] (1) The predicted movement duration T2 is a theoretical model established by rigorous theoretical derivation, contains few parameters, and the parameters are easy to determine. The prediction value is basically consistent with the field monitoring value, which shows that the prediction accuracy is high.

[0114] (2) The parameters of the coal seam mining induced surface movement duration prediction model proposed by the application can be predicted only according to the parameters such as coal seam thickness, mining depth and working face mining speed, without the need for a large amount of field monitoring data, which is convenient for field application.

[0115] Although the foregoing embodiments are described in detail, those skilled in the art can modify the technical solutions described in the foregoing embodiments, or make equivalent replacements to some of the technical features; and these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present application.

Claims

1. A method of predicting the duration of surface movement in coal mining, characterized by, The prediction method comprises the following steps: a. establishing a prediction function of surface subsidence caused by coal seam mining: In formula (1), W(t) is the instantaneous subsidence value of a point on the surface; W0 is the final subsidence value of a point on the surface; C is a time influence parameter of the improved model; b. establishing a surface movement duration prediction model of coal seam mining according to formula (1): In formula (2), T2 is the surface movement duration; c. calculating the time influence parameter C according to the following formula (3): In formula (3), H is the average mining depth; v is the coal seam mining speed; the value of n is 1.2-1.4; d. obtaining the values of W0, H and v, and substituting them into formula (3) and formula (2) to calculate the surface movement duration T2; The formula (1) in step a is obtained by the following steps: The following differential equation is established to describe the surface dynamic subsidence process: Solving formula (1-1) obtains the following formula: Integrating both sides of formula (1-2) obtains the following formula: In formula (1-3), A is an integral constant; t is the real-time time, and the unit is day; Simplifying formula (1-3) obtains the following formula: In formula (1-4), B is an integral constant; Taking the time when the subsidence amount reaches 10 mm as the subsidence starting time, that is, t=0, according to formula (1-4), there is B=100W0-1 (1-5) Substituting formula (1-5) into formula (1-4) obtains the formula (1); The formula (2) in step b is obtained by the following steps: Supposing that the time corresponding to the end of surface movement is T2, according to formula (1), the surface subsidence amount W(T2) at this time is: Supposing that each month is 30 days, according to formula (2-1), the surface subsidence amount W(T2-180) at 6 months before the end of surface movement is: According to formula (2-2) and the definition of surface movement duration, the two subsidence amounts W(T2-180) and W(T2) need to satisfy the following relationship: When the difference between the subsidence amount at T2 and the subsidence amount at T2-180 is just 30 mm, T2 is the surface movement duration, since the unit of the predicted subsidence amount difference on the left side of formula (2-3) is m, and the unit on the right side is mm, therefore, formula (2-3) can be converted into Simplifying the above formula (2-4) obtains formula (2).

2. The method of claim 1, wherein, The W0 is obtained by monitoring or calculated according to the following formula (4) W0=mq cosα (4) In formula (4), m is the thickness of the coal seam; α is the inclination of the coal seam; q is the subsidence coefficient.

3. The method of claim 1, wherein, The value of n in formula (3) is selected as 1.

4.

4. The method of claim 1, wherein, The determination method of the time influence parameter C is as follows: According to the probability integral theory, under the condition of nearly horizontal coal seam mining, when the mining range reaches the critical value of full mining, the maximum surface subsidence is approximately equal to 0.98W0, assuming the mining speed is v, and the critical size of the goaf is L f , then the critical time of full mining is expressed as The calculation formula of model influence parameter C is obtained by combining formula (1): When the working face advances a distance of nH, full mining is reached, so L f is: L f = nH (3-2) Substituting formula (3-2) into formula (3-1) obtains the calculation formula (3) of the model influence parameter C.

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