Prediction method for long-term deformation of different-inclination-angle inclined coal seam on mountainous area earth surface

Abstract

The invention relates to the technical field of long-term deformation monitoring of coal mining subsidence areas, in particular to a method for predicting long-term deformation of different-dip-angle inclined coal seams on the surface of a mountainous area. The method comprises the following steps: establishing an uphill-direction cavity area range calculation formula, a downhill-direction cavity area range calculation formula, an uphill-direction cavity area equivalent mining thickness calculation formula, a compaction area equivalent mining thickness calculation formula and a downhill-direction cavity area equivalent mining thickness calculation formula of inclined coal seams with different inclination angles; a mountain surface inclined coal seam long-term deformation prediction formula with different inclination angles is established; acquiring a coal seam inclination angle in a research area, judging an inclined coal seam type, and acquiring calculation parameters; substituting the obtained parameters into a long-term deformation prediction formula of the inclined coal seam with different inclination angles on the surface of the mountainous area to obtain a long-term deformation result in the research area; the problems that an existing monitoring technology for regional residual deformation is large in measurement difficulty and low in precision, and residual deformation of inclined coal seams with inclination angles of different degrees is not fully considered are solved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of long-term deformation monitoring of coal mining subsidence area, and particularly relates to a long-term deformation prediction method for inclined coal seams with different inclinations on mountain surfaces. BACKGROUND

[0002] Under the influence of complex topography and other factors, the surface movement and deformation caused by underground mining of coal resources in mountainous areas is more serious than in plain areas, and the complex topography of mountainous areas also has a certain degree of influence on residual deformation. The residual deformation of inclined coal seams is different from that of horizontal coal seams, and the residual deformation of inclined coal seams has different geometric and mechanical distribution characteristics from horizontal coal seams, and often shows skewness.

[0003] At present, the equivalent variable mining thickness prediction model is often used to monitor the residual deformation of the area, and traditional methods such as leveling and traverse surveying can also be used to monitor the residual subsidence of mountainous area mining; GNSS (Global Navigation Satellite System) can also be used to monitor the residual subsidence of mountainous area / mining area mining.

[0004] However, the existing technology is difficult to measure, has low precision, and is easily disturbed by external factors. If the probability integral method based on equivalent variable mining thickness with symmetrical distribution characteristics is used, the prediction error is large, and at present, the residual deformation prediction of inclined coal seams often only considers gently inclined coal seams or steeply inclined coal seams, and no prediction model can fully consider the residual deformation of inclined coal seams with different inclinations. Therefore, the study of long-term deformation of inclined coal seams with different inclinations is very important, and the study of long-term deformation of inclined coal seams on mountain surfaces is not mature.

[0005] Therefore, it is necessary to invent a long-term deformation prediction method for inclined coal seams with different inclinations on mountain surfaces to solve the above problems. SUMMARY

[0006] The present application provides a long-term deformation prediction method for inclined coal seams with different inclinations on mountain surfaces to solve the problems of difficult measurement, low precision, and easy disturbance by external factors in the existing residual deformation monitoring technology of the area, and the residual deformation prediction of inclined coal seams often only considers gently inclined coal seams or steeply inclined coal seams, and no prediction model can fully consider the residual deformation of inclined coal seams with different inclinations.

[0007] The present application is implemented by using the following technical solutions:

[0008] A method for predicting long-term deformation of different inclination angle inclined coal seams on mountain surface, comprising the following steps:

[0009] S10: establishing a range calculation formula of a cavity area in an upward direction, a range calculation formula of a cavity area in a downward direction, an equivalent mining thickness calculation formula of a cavity area in an upward direction, an equivalent mining thickness calculation formula of a compression area, an equivalent mining thickness calculation formula of a cavity area in a downward direction, and a long-term deformation prediction formula of different inclination angle inclined coal seams on mountain surface;

[0010] S20: obtaining a coal seam inclination angle in a study area, judging a type of inclined coal seam, and obtaining calculation parameters;

[0011] S30: obtaining a range of a cavity area in an upward direction and a range of a cavity area in a downward direction according to the coal seam inclination angle through the range calculation formula of the cavity area in the upward direction and the range calculation formula of the cavity area in the downward direction;

[0012] S40: obtaining an equivalent mining thickness of a cavity area in an upward direction, an equivalent mining thickness of a compression area, and an equivalent mining thickness of a cavity area in a downward direction according to the coal seam inclination angle through the equivalent mining thickness calculation formula of the cavity area in the upward direction, the equivalent mining thickness calculation formula of the compression area, and the equivalent mining thickness calculation formula of the cavity area in the downward direction;

[0013] S50: inputting surface coordinate data in a calculation area into a computer, fitting a smooth curve through a polynomial to obtain a function thereof, judging a concave-convex interval of the function, calculating a sliding influence function, and obtaining mountain surface characteristic coefficients according to a mountain surface characteristic coefficient table;

[0014] S60: substituting parameters obtained in S20-S50 into the long-term deformation prediction formula of different inclination angle inclined coal seams on mountain surface to obtain a long-term deformation result in the study area.

[0015] Further, step S10 specifically comprises:

[0016] S11: dividing a goaf into three parts and improving a cavity area variable mining thickness model to establish a probability integral method prediction model based on equivalent variable mining thickness;

[0017] S12: using the probability integral method prediction model based on equivalent variable mining thickness to establish a long-term deformation prediction formula of a near-horizontal coal seam and a long-term deformation prediction formula of an acute-inclined coal seam according to residual deformation structures of the near-horizontal coal seam and the acute-inclined coal seam;

[0018] S13: taking the residual deformation structures of the near-horizontal coal seam and the acute-inclined coal seam as boundary conditions to establish a range calculation formula of a cavity area in an upward direction and a range calculation formula of a cavity area in a downward direction of a gently-inclined coal seam and an inclined coal seam;

[0019] S14: According to the residual deformation structure of gently inclined coal seam and the residual deformation structure of steeply inclined coal seam, the calculation formula of the upper slope direction hollow area range, the calculation formula of the lower slope direction hollow area range, the calculation formula of the upper slope direction hollow area equivalent mining thickness, the calculation formula of the equivalent mining thickness of the compaction area and the calculation formula of the lower slope direction hollow area equivalent mining thickness of different inclination angle inclined coal seam are derived;

[0020] S15: According to the calculation formula of the upper slope direction hollow area range, the calculation formula of the lower slope direction hollow area range, the upper slope direction hollow area equivalent mining thickness, the equivalent mining thickness of the compaction area and the calculation formula of the lower slope direction hollow area equivalent mining thickness of different inclination angle inclined coal seam, the long-term deformation prediction formula of different inclination angle inclined coal seam is established;

[0021] S16: Considering the influence of mountainous surface, the long-term deformation prediction formula of different inclination angle inclined coal seam of mountainous surface is established.

[0022] Further, in step S11: the establishment of the probability integral method prediction model based on equivalent variable mining thickness includes:

[0023] Firstly, the goaf is divided into three parts: left hollow area, middle insufficient compaction area and right hollow area;

[0024] Then, in view of the integral difficulty caused by linear variable thickness of the hollow area, a discretization improvement scheme is proposed, that is, the hollow area is subdivided into small blocks with equal width, and the middle line height of the block is taken as the equivalent mining thickness parameter;

[0025] Finally, by superimposing the unit subsidence contribution of each block, combining the residual inclination parameter and the length of the hollow area, the probability integral method prediction model based on equivalent variable mining thickness is constructed.

[0026] Further, in step S12: the long-term deformation prediction formula of the near horizontal coal seam is applicable to the coal seam with inclination angle less than 8°, and its establishment includes:

[0027] Firstly, the near horizontal coal seam is divided into left hollow area, middle insufficient compaction area and right hollow area from left to right according to the inclination direction;

[0028] Then, according to the probability integral method prediction model based on equivalent variable mining thickness, taking the block discretization height of left hollow area and right hollow area, the residual active thickness of middle insufficient compaction area and mining thickness as the core parameters, combining the time factor influence coefficient and the main influence angle tangent in the rock property and prediction parameter correlation coefficient table, the long-term deformation prediction formula of the near horizontal coal seam is constructed.

[0029] Further, in step S12: the long-term deformation prediction formula of the steeply inclined coal seam is applicable to the coal seam with inclination angle greater than 45°, and its establishment includes:

[0030] According to the characteristics of the rock mass sliding and filling in the downward direction, asymmetric partition is adopted, the height of the caving zone and the equivalent mining thickness calculated by the rock fragmentation coefficient are introduced, the height of the cavity zone in the upward direction, the mining influence propagation angle and the lithology parameter table are used as the core parameters, and the long-term deformation prediction formula of the steep coal seam is established by combining the time factor.

[0031] Further, in step S13, the establishment of the cavity zone range calculation formula in the upward direction and the cavity zone range calculation formula in the downward direction of the gently inclined coal seam and the inclined coal seam includes:

[0032] Taking the inclination angle alpha as the core variable, the boundary conditions of the near-horizontal coal seam and the steep coal seam are combined, the quantitative relationship between the inclination angle and the cavity zone range is established, that is, the cavity zone range in the downward direction decreases with the increase of the inclination angle, and the cavity zone range in the upward direction increases with the increase of the inclination angle, and thus the cavity zone range calculation formula in the upward direction and the cavity zone range calculation formula in the downward direction of the gently inclined coal seam and the inclined coal seam are established; and the cavity zone range calculation formula in the upward direction and the cavity zone range calculation formula in the downward direction of the gently inclined coal seam are applicable to the coal seam with an inclination angle greater than 8° and less than 25°, and the cavity zone range calculation formula in the upward direction and the cavity zone range calculation formula in the downward direction of the inclined coal seam are applicable to the coal seam with an inclination angle greater than 25° and less than 45°.

[0033] Further, in step S16, the long-term deformation prediction formula of the inclined coal seam with different inclination angles in the mountainous area is established by superimposing the ground movement deformation value caused by mining in the flat area and the deformation increment caused by mining-induced sliding, and the core parameters include the flat deformation parameters, the mining-induced sliding increment parameters and the mountainous area characteristic parameters: the flat deformation parameters include the subsidence value, the horizontal movement value, the inclination value, the curvature value and the horizontal deformation value under the same geological mining conditions, which are obtained by the flat probability integral prediction formula; the mining-induced sliding increment parameters include the subsidence, the horizontal movement, the inclination, the curvature and the horizontal deformation increment caused by sliding; and the mountainous area characteristic parameters include the mountainous area ground surface characteristic coefficient, the topographic trend surface inclination angle and the sliding influence function.

[0034] Further, in step S20, the calculation parameters include the subsidence coefficient, the horizontal movement coefficient, the main influence radius and the tangent of the main influence angle, the inflection point offset distance and the mining influence propagation angle.

[0035] The present application provides a prediction method for long-term deformation of inclined coal seams with different inclination angles in mountainous areas, which has the following advantages compared with the prior art:

[0036] 1. Compared with the existing residual deformation monitoring technology, the present method improves the calculation accuracy and is applied to long-term deformation prediction of inclined coal seams by improving the cavity zone.

[0037] 2. Compared with the existing monitoring technology for regional residual deformation, which only considers the long-term deformation prediction method of gently inclined coal seams and the long-term deformation prediction method of steeply inclined coal seams, and does not fully consider the problem of residual deformation of inclined coal seams with different degrees of inclination, the present invention takes the coal seam inclination as the variable of the prediction model in the problem of long-term deformation of inclined coal seams, and regards the structure of the residual deformation of nearly horizontal coal seams and steeply inclined coal seams as the boundary condition of the model. Based on the random medium theory, a long-term deformation prediction method for inclined coal seams in the interval [0°, 90°] is constructed.

[0038] 3. Compared with the existing monitoring technology of regional residual deformation, which does not consider the long-term deformation prediction model of mountain surface under the condition of inclined coal seams and only considers the situation of horizontal coal seams, the present invention fully considers the joint influence of mountain surface and inclined coal seams with different inclination angles, and superimposes the long-term deformation prediction model of inclined coal seams with different inclination angles with the mountain surface movement prediction model to construct a long-term deformation prediction model of inclined coal seams with different inclination angles on the mountain surface. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 It is a flow chart of the present invention.

[0040] Figure 2 It is a specific flow chart of step S10 in the present invention.

[0041] Figure 3 It is a block diagram of the probability integration method prediction model based on equivalent variable thickness of the present invention.

[0042] Figure 4 It is a block diagram of the cavity area division of the present invention.

[0043] Figure 5 It is a schematic diagram of equivalent mining thickness of a near-horizontal coal seam according to the present invention.

[0044] Figure 6 This is a schematic diagram of calculating the cavity area in the downhill direction of a steeply inclined coal seam according to the present invention.

[0045] Figure 7 It is a schematic diagram of equivalent mining thickness of steeply inclined coal seams according to the present invention.

[0046] Figure 8 It is a schematic diagram of equivalent mining thickness of inclined coal seams according to the present invention. DETAILED DESCRIPTION

[0047] A method for predicting the long-term deformation of coal seams with different dip angles on the surface of mountainous areas, such as Figure 1 As shown, the following steps are included:

[0048] S10: Establishing a formula for calculating the range of the gob in the upward direction of the inclined coal seam, a formula for calculating the range of the gob in the downward direction of the inclined coal seam, a formula for calculating the equivalent mining thickness of the gob in the upward direction, a formula for calculating the equivalent mining thickness of the compression zone, a formula for calculating the equivalent mining thickness of the gob in the downward direction, and a formula for predicting the long-term deformation of the inclined coal seam on the surface of the mountainous area.

[0049] As shown in Figure 1 , step S10 specifically includes:

[0050] S11: Dividing the gob into three parts and improving the gob variable mining thickness model to establish a prediction model based on the equivalent variable mining thickness probability integral method.

[0051] The point x subsidence value caused by unit mining is:

[0052]

[0053] In the formula: r is the main influence radius.

[0054] The existing prediction model of the equivalent variable mining thickness probability integral method based on the zoning of the gob into three parts, i.e., the left gob, the middle insufficient compression zone, and the right gob, the left and right gobs as boundary zones, and the superposition idea, usually simplifies the gob to an equivalent mining height m'. According to the calculation formula of the probability integral method for any point on the ground and considering the symmetry of the gob, the prediction model of the equivalent variable mining thickness probability integral method can be obtained, as shown in the following formula:

[0055] W0(x) = ∫ AC m′W e (x-s)ds + ∫ CD m1W e (x-s)ds + ∫ DB m′W e (x-s)ds (1-2)

[0056]

[0057] U0(x) = brI0(x) (1-4)

[0058] In the formula: W0(x) is the residual subsidence value of a certain point on the ground; x is the horizontal coordinate of any point on the ground; s is the horizontal coordinate of the mining unit; AC, CD, and DB are integral intervals; as shown in Figure 3 , m' and m1 represent the residual active thickness of the boundary zone and the middle insufficient compression zone, respectively; W e (x) is the unit subsidence formed by unit mining; I0(x) is the residual inclination; I b1 , I z , and I b2Residual tilt of AC, CD, DB segment respectively; U0(x) is residual horizontal movement value; b is horizontal movement coefficient.

[0059] The cavity zone is simplified as equivalent mining height m' because the thickness of the cavity zone of the variable mining thickness model is linearly changed. If the thickness of the cavity zone is introduced into a first order function with variable x, it will be impossible to integrate in the probability integral method model, but based on the most basic integral idea, the cavity zone part can be divided into multiple small areas for calculation to improve the accuracy.

[0060] Figure 4 The middle yellow area is a small block divided in the boundary cavity zone, the width of each block is the same, and the height is the same as the original height corresponding to the block center line. Assuming that the number of small blocks is n0, the height of each block can be calculated as shown in the following formula:

[0061]

[0062] m1=m(1-q) (1-6)

[0063] According to the same method, the right cavity zone can also be divided and calculated as shown in the following formula:

[0064]

[0065] In the formula: n is the block number of the left cavity zone, from left to right, it is 1, 2, 3…; m, m1 are the mining thickness and the residual active thickness of the middle insufficiently compacted zone respectively; n' represents the block number of the right cavity zone; n0' is the number of small blocks of the right cavity zone; l0 is the length of the left cavity zone; l'0 is the length of the right cavity zone.

[0066] Through the above method, the cavity zone is refined, and a new prediction model based on equivalent variable mining thickness probability integral method is constructed by using the superposition idea, as shown in the following formula:

[0067]

[0068] S12: According to the residual deformation structure of the near-horizontal coal seam and the residual deformation structure of the steeply inclined coal seam, a long-term deformation prediction formula of the near-horizontal coal seam and a long-term deformation prediction formula of the steeply inclined coal seam are established by using the probability integral method prediction model based on equivalent variable mining thickness.

[0069] When the upper rock mass of the working face collapses, the rock mass generally exists in a layered structure. For the nearly horizontal coal seam with a dip angle less than 8°, the upper rock mass collapses in a layered structure and remains on the floor of the working face, and the collapsed rock mass exists in a sheet structure and does not roll down the mountain or dislocate along the bedding plane due to the gravity component, so it is not necessary to consider the sliding of the working face from the uphill side to the downhill side, that is, the residual deformation of the horizontal coal seam is similar. Figure 5 As shown in FIG. 2, the left side cavity zone, the middle insufficiently compacted zone and the right side cavity zone are formed from left to right.

[0070] The equivalent mining thickness of the nearly horizontal coal seam is still calculated by the method for the cavity zone, and the two side cavity zones are calculated by dividing the cavity zone into multiple small regions based on the basic integration idea to improve the accuracy, and the following formula is obtained:

[0071]

[0072] m1=m(1-q) (2-2)

[0073]

[0074] In the formula, h n is the height of the nth block of the left side cavity zone; h n′ is the height of the nth block of the right side cavity zone; n is the block number of the left side cavity zone, which is 1, 2, 3, … from left to right; m and m1 are the mining thickness and the residual active thickness of the middle insufficiently compacted zone, respectively; n' represents the block number of the right side cavity zone; and n0' is the number of small blocks of the right side cavity zone.

[0075] Taking the x-axis as the starting point at the downhill direction of the open-off cut of the nearly horizontal coal seam, the long-term deformation prediction formula of the nearly horizontal coal seam is obtained as follows:

[0076]

[0077] U0(x) = brI0(x) (2-6)

[0078]

[0079] In the formula, W0(x, t) is the subsidence value at x at time t; s1 is the length of the cavity zone in the downhill direction; s2 is the length of the cavity zone in the uphill direction; s1 and s2 can be taken from Table 1; H is the mining depth of the open-off cut; tanβ is the tangent value of the main influence angle; I0(x, t) is the residual inclination; I b1 , I z and I b2are the residual inclinations of the downhill void area, the insufficiently compacted area, and the uphill void area, respectively; U0(x) is the residual horizontal movement value; s′1, s′2, and l′ are the relationships between s1, s2, and l after coordinate transformation, respectively; α is the inclination of the coal seam; θ is the propagation angle of mining influence; L is the mining length of the inclined coal seam; c is the influence coefficient of the time factor related to the mechanical properties of the overlying rock strata; and t is time.

[0080] Table 1 Correlation coefficients between lithology and prediction parameters

[0081]

[0082] For steeply inclined coal seams with an inclination angle greater than 45°, when the inclination angle of the coal seam is large, the rock blocks that fall to the bottom of the goaf slide in the downward direction along the inclined working surface due to gravity, and first fill the lower boundary cavity area, forming an insufficiently compacted area with a broken and loose structure. The range of the cavity in the uphill direction of the goaf increases due to the continuous falling of rock blocks, until the overlying rock mass reaches a new balance. By studying the movement and destruction laws of overlying rock after mining at a high-angle coal seam, it was found that the rock blocks that fall to the bottom of the goaf, under the influence of their own gravity, roll in the downward direction along the inclined working surface to continuously fill the lower boundary cavity, weakening the movement of the rock layer in the downhill direction, thereby inhibiting the further falling of the rock blocks directly on the top of the coal seam; the cavity in the uphill direction will become larger as the rock blocks on the coal seam roof fall and flow, until the overlying rock layer reaches a new balance and forms a new equilibrium. Figure 7 The surface residual subsidence model after mining of steeply inclined coal seams is shown.

[0083] When the buried inclination of the coal seam is large, the degree of damage of the direct roof overburden in the uphill part of the goaf is higher, while the degree of damage in the downhill part is lower. Figure 6 The arch shape shown in the figure, after the continuous collapse of the coal seam roof rock blocks, can eventually form a nearly triangular overburden failure shape ACD. The product of the direct roof overburden failure area ACD and the collapse expansion coefficient K of the collapsed rock is equivalent to the area of ​​ABC plus the rectangular area of ​​the goaf with a length of l.

[0084]

[0085] Where: H m is the height of the caving zone, in meters; K is the expansion coefficient of the rock in the caving zone, which is an empirical value based on measured data and is generally taken as 1.10-1.40.

[0086] When the inclination of a coal mine is large, the goaf in the downhill direction of the mining face is filled by the rock that collapses in the uphill direction, and the mining thickness m gradually increases from downhill to uphill. Therefore, the average thickness of the coal seam with a large inclination is greater than the mining thickness when calculating the gently inclined coal seam. The equivalent mining thickness is defined as m′, and its expression is as follows.

[0087]

[0088] The equivalent mining thickness m1 of the middle insufficiently compacted area is:

[0089]

[0090] The calculation method for the cavity area in the above is still used on the steeply inclined coal seam. Based on the most basic integral idea, the cavity area in the upward direction is calculated by dividing the cavity area into multiple small areas to improve the accuracy, and the following formula is obtained:

[0091]

[0092] In the formula, h n′ is the height of the nth block of the cavity area in the upward direction; n' is the block number of the cavity area in the upward direction, which is 1, 2, 3, … from left to right; m is the thickness of the mining coal seam; H m is the height of the caving zone; n0' is the number of small blocks of the cavity area in the upward direction.

[0093] Taking the cut-and-fill hole at the downward direction of the steeply inclined coal seam as the x-axis origin, the long-term deformation prediction formula of the steeply inclined coal seam is obtained as:

[0094]

[0095] U0(x,t) = brI0(x,t) (2-19)

[0096]

[0097] In the formula, W0(x,t) is the subsidence value at x at time t; s2 is the length of the cavity area in the upward direction; s1 and s2 can be taken from Table 1; H is the mining depth at the cut-and-fill hole; tanβ is the tangent value of the main influence angle; I0(x,t) is the residual inclination; I z and I b2 are the residual inclinations of the insufficiently compacted area and the upward cavity area, respectively; U0(x) is the residual horizontal movement value; s'2 and l' are the relationships of s2 and l after coordinate conversion, respectively; α is the coal seam inclination angle; θ is the propagation angle of the mining influence; L is the mining length of the inclined coal seam; c is the time factor influence coefficient related to the mechanical properties of the overburden rock; and t is the time.

[0098] S13: Taking the residual deformation structure of the near-horizontal coal seam and the residual deformation structure of the steeply inclined coal seam as the boundary conditions, the calculation formula of the upward cavity area range of the gently inclined coal seam and the inclined coal seam and the calculation formula of the downward cavity area range are established.

[0099] S14: According to the residual deformation structure of gently inclined coal seam and the residual deformation structure of steeply inclined coal seam, the calculation formula of the upper direction hollow area range of different inclined coal seams, the calculation formula of the lower direction hollow area range, the calculation formula of the equivalent mining thickness of the upper direction hollow area, the equivalent mining thickness calculation formula of the compaction zone and the equivalent mining thickness calculation formula of the lower direction hollow area are derived.

[0100] From the above description, we know that for the near horizontal coal seam, the two side hollow areas are roughly similar to the horizontal coal seam, but for the steeply inclined coal seam, the lower direction hollow area is filled and the upper direction hollow area range is large, so for the gently inclined coal seam and the inclined coal seam, the lower direction hollow area range under the same geological conditions will be smaller and smaller with the increase of the dip angle, and the upper direction hollow area range will be larger and larger with the increase of the dip angle. As shown in the following formula: Figure 8 Therefore, we take the dip angle as a variable to establish the calculation formula of the upper direction hollow area range and the lower direction hollow area range as follows:

[0101] The lower direction hollow area range is:

[0102]

[0103] The upper direction hollow area range is:

[0104]

[0105] Similarly, the equivalent mining thickness can be calculated as follows:

[0106] The equivalent mining thickness of the lower direction hollow area is:

[0107]

[0108] The equivalent mining thickness of the compaction zone is:

[0109]

[0110] The equivalent mining thickness of the upper direction hollow area is:

[0111]

[0112] S15: According to the calculation formula of the upper direction hollow area range of different inclined coal seams, the calculation formula of the lower direction hollow area range, the equivalent mining thickness of the upper direction hollow area, the equivalent mining thickness of the compaction zone and the equivalent mining thickness of the lower direction hollow area, the long-term deformation prediction formula of different inclined coal seams is established.

[0113] Through the above calculation formula of the hollow area range and the calculation formula of the equivalent mining thickness, we can establish the long-term deformation prediction model of different inclined coal seams:

[0114] When 0° < a < 8°,

[0115]

[0116] U0(x) = brI0(x) (2-6)

[0117]

[0118] When 8° < α < 45°,

[0119]

[0120] When 45° < α < 90°,

[0121]

[0122] U0(x,t) = brI0(x,t) (2-19)

[0123]

[0124] S16: Considering the influence of mountain surface, a long-term deformation prediction formula of inclined coal seam with different dip angles of mountain surface is established.

[0125] Mountain surface movement includes surface movement caused by coal mining and surface movement caused by mountain slope sliding, so for the prediction of mountain surface movement deformation, the surface movement deformation value caused by mining on flat ground and the amount of mountain sliding can be superimposed to predict, as shown in the following formula:

[0126]

[0127] In formula (3-1) ~ (3-4), W(x), U(x), i(x), K(x), and E(x) are respectively the subsidence, horizontal movement, inclination, curvature and horizontal deformation values under the same geological mining conditions, which can be obtained by the flat ground probability integral prediction formula; ΔW(x), ΔU(x), Δi(x), ΔK(x), and ΔE(x) are respectively the subsidence, horizontal movement, inclination, curvature and horizontal deformation increments caused by mining-induced sliding of the slope.

[0128] The additional subsidence and additional horizontal movement values of mountain surface caused by mining-induced sliding can be represented by the following formula:

[0129] ΔW(x) = D x P(x)W(x)tan 2 α x (3-5)

[0130] ΔU(x) = D x P(x)W(x)tanα x (3-6)

[0131] where ΔW(x), ΔU(x) are additional subsidence and horizontal movement caused by mining-induced slip;

[0132] D x is the surface feature coefficient of mountainous area, whose value is referenced to Table 2;

[0133] P(x) is the slip influence function;

[0134] W(x) is the subsidence value of flat ground under the same geological and mining conditions;

[0135] α x is the inclination of the terrain trend surface of the smoothed surface point.

[0136] Table 2 Surface feature coefficient table of mountainous area

[0137]

[0138] If there is sufficient actual observation data, the slip influence function P(x) can be calculated by the following formula:

[0139]

[0140] or

[0141]

[0142] If there is no sufficient actual observation data, formula (3-9) can be used for calculation.

[0143]

[0144] where A, P, t are slip influence parameters.

[0145] Therefore, the formula of the surface mining subsidence prediction model of mountainous area is:

[0146] W'(x) = W(x) + D x P(x)W(x)tan 2 α (3-10)

[0147] U'(x) = U(x) + D x P(x)W(x)tanα (3-11)

[0148] The formula of the long-term deformation prediction model of mountainous area is further:

[0149] W'(0(x, t) = [W0(x, t) + D x P(x)W0(x, t)tan 2 α](1 - e -ct ) (3-12)

[0150] U'(0(x, t) = [U0(x, t) + Dx P(x)W0(x,t)tan a (1 - e -ct ) (3-13)

[0151] Substitute the long-term deformation prediction formula of different inclination angle inclined coal seam in the above into the long-term deformation prediction formula of different inclination angle inclined coal seam in mountainous area surface.

[0152] The total formula is as follows:

[0153] When 0° < a < 8°,

[0154]

[0155] U'(x,t) = bri(x,t) + D(x)P(x)W'(x,t)tan a x (3-15)

[0156]

[0157] In the formula:

[0158]

[0159] When 8° < a < 45°,

[0160]

[0161] U'(x,t) = bri(x,t) + D(x)P(x)W'(x,t)tan a x (3-18)

[0162]

[0163] In the formula:

[0164]

[0165] When 45° < a < 90°,

[0166]

[0167] U'(x,t) = bri(x,t) + D(x)P(x)W'(x,t)tan a x (3-21)

[0168]

[0169] In the formula:

[0170]

[0171] S20: Obtain the coal seam dip angle in the study area, determine the inclined coal seam type, and obtain the calculation parameters.

[0172] (1) Subsidence coefficient q

[0173] The subsidence coefficient q is a very important parameter for predicting the surface movement and deformation of the goaf, and its value reflects the degree of caving of the overburden strata above the inclined coal seam after mining. The greater the q value, the more complete the caving of the overburden strata above the coal seam, resulting in greater surface subsidence, inclination deformation, and curvature value. When the working face of the coal mine meets the full mining conditions, the value of q can be calculated according to the measured maximum subsidence value W max , the mining thickness m, and the coal seam dip angle a according to (4-1).

[0174]

[0175] When there is insufficient measured data, the subsidence coefficient q can be calculated according to Table 1.

[0176] (2) Horizontal movement coefficient b

[0177] Under the condition of full mining, the horizontal movement coefficient b is equal to the ratio of the maximum residual horizontal movement value to the maximum residual subsidence value caused by the mining of the inclined coal seam, and the calculation is as shown in formula (4-2).

[0178]

[0179] The horizontal movement coefficient b can also be taken from Table 1.

[0180] (3) Main influence radius r and main influence tangent tanβ

[0181] When the working face of the coal seam meets the full mining conditions, the movement and deformation of the surface mainly occur within the interval of x = -r ~ r. The influencing factors of tanβ value are many, mainly related to the nature of the goaf roof and the mining depth of the coal seam. Under the condition of the same mining depth of the coal seam, the tanβ value of hard rock is smaller; when the overburden rock properties are the same, the mining depth is positively correlated with the tanβ value.

[0182]

[0183] The tanβ value can also be taken from Table 1 in the regulation.

[0184] (4) Inflection point offset distance s1, s2

[0185] The inflection point of the moving and deformation curve is located directly above the coal wall without considering the overhanging effect of the inside of the coal wall, and under actual mining conditions, the overhanging effect of the goaf roof inside the coal wall makes the ground surface moving and deformation curve above it translate to the center of the goaf, causing the inflection point of the moving and deformation curve to deviate, and the distance of the deviation is the inflection point deviation distance.

[0186] (5) Mining influence propagation angle θ

[0187] The mining influence propagation angle θ is a parameter specific to the working face of the mining coal seam, and the size of the coal seam dip angle has a relatively obvious influence on θ, and the calculation expression is as follows:

[0188] θ = 90°-kα (4-4)

[0189] In formula (4-4), k is a coefficient related to the lithology of overburden rock, and generally takes a value within the range of 0.5-0.8. θ can also be taken according to the regulations in Table 1.

[0190] S30: According to the coal seam dip angle, the up-dip direction goaf range calculation formula and the down-dip direction goaf range calculation formula are used to obtain the up-dip direction goaf range and the down-dip direction goaf range;

[0191] S40: According to the coal seam dip angle, the up-dip direction goaf equivalent mining thickness calculation formula, the compaction zone equivalent mining thickness calculation formula and the down-dip direction goaf equivalent mining thickness calculation formula are used to obtain the up-dip direction goaf equivalent mining thickness, the compaction zone equivalent mining thickness and the down-dip direction goaf equivalent mining thickness;

[0192] S50: The ground surface coordinate data in the calculation area is input into the computer, a smooth curve is calculated by polynomial fitting, the function thereof is solved, the concave-convex interval of the function is judged, the sliding influence function is calculated, and the mountain area ground surface characteristic coefficient is obtained according to the mountain area ground surface characteristic coefficient table;

[0193] S60: The parameters obtained in S20-S50 are substituted into the long-term deformation prediction formula of the inclined coal seam with different dip angles in the mountain area ground surface to obtain the long-term deformation result in the study area.

[0194] In the description of the present application, it should be understood that the indicated orientation or positional relationship is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the present application and simplifying the description, and therefore cannot be understood as a limitation on the present application.

[0195] While embodiments of the application have been shown and described, it is to be understood that the embodiments described are merely exemplary of the principles and application of the present application. Numerous modifications and adaptions can be effected without departing from the spirit and scope of the present application, which is not limited to the exact construction and arrangement described. It is intended, therefore, to cover all modifications and adaptions that fall within the scope of the claims and their equivalents.

Claims

1. A method for predicting long-term deformation of coal seams with different inclination angles on the surface of mountainous areas, characterized by: The following steps are involved: S10: Establish calculation formulas for the range of the uphill hollow area, the range of the downhill hollow area, the equivalent mining thickness calculation formulas for the uphill hollow area, the equivalent mining thickness calculation formulas for the compacted area, and the equivalent mining thickness calculation formulas for the downhill hollow area of ​​coal seams with different dip angles, as well as long-term deformation prediction formulas for inclined coal seams with different dip angles on the mountainous surface; S20: Obtain the inclination angle of the coal seam in the study area, determine the type of the inclined coal seam, and obtain calculation parameters; S30: according to the coal seam inclination, obtaining the range of the uphill direction cavity area and the range of the downhill direction cavity area by using the uphill direction cavity area calculation formula and the downhill direction cavity area calculation formula; S40: according to the inclination of the coal seam, the equivalent mining thickness of the uphill direction void area, the equivalent mining thickness of the compaction area, and the equivalent mining thickness of the downhill direction void area are obtained by using the calculation formula of equivalent mining thickness of the uphill direction void area, the calculation formula of equivalent mining thickness of the compaction area, and the calculation formula of equivalent mining thickness of the downhill direction void area; S50: Inputting the surface coordinate data in the calculation area into the computer, calculating a smooth curve by polynomial fitting and finding its function, determining the concave and convex interval of the function, calculating the slip influence function, and obtaining the mountain surface characteristic coefficient according to the mountain surface characteristic coefficient table; S60: Substitute the parameters obtained from S20-S50 into the long-term deformation prediction formula of coal seams with different dip angles on the mountain surface to obtain the long-term deformation results in the study area.

2. The method for predicting long-term deformation of inclined coal seams with different inclination angles on mountainous surfaces according to claim 1 is characterized by: Step S10 specifically includes: S11: Divide the goaf into three parts and improve the variable mining thickness model of the goaf area, and establish a probability integral method prediction model based on equivalent variable mining thickness; S12: Based on the residual deformation structure of nearly horizontal coal seams and the residual deformation structure of steeply inclined coal seams, a long-term deformation prediction formula for nearly horizontal coal seams and a long-term deformation prediction formula for steeply inclined coal seams are established using a probability integral method prediction model based on equivalent variable mining thickness; S13: Taking the residual deformation structure of nearly horizontal coal seams and the residual deformation structure of steeply inclined coal seams as boundary conditions, establish the calculation formulas for the range of the cavity area in the uphill direction of gently inclined coal seams and the downhill direction of inclined coal seams; S14: Based on the residual deformation structure of gently inclined coal seams and steeply inclined coal seams, the calculation formulas for the range of the uphill void area, the range of the downhill void area, the equivalent mining thickness calculation formula for the uphill void area, the equivalent mining thickness calculation formula for the compaction area, and the equivalent mining thickness calculation formula for the downhill void area in coal seams with different dip angles are derived; S15: Based on the calculation formulas for the range of the uphill void area, the range of the downhill void area, the equivalent mining thickness of the uphill void area, the equivalent mining thickness of the compacted area, and the equivalent mining thickness of the downhill void area in coal seams with different dip angles, a long-term deformation prediction formula for coal seams with different dip angles is established; S16: Considering the influence of mountainous surface, a long-term deformation prediction formula for coal seams with different inclination angles on mountainous surface is established.

3. The method for predicting long-term deformation of inclined coal seams with different inclination angles on mountainous surfaces according to claim 2, characterized in that: In step S11: the establishment of the probability integral method prediction model based on equivalent variable thickness sampling includes: First, the goaf is divided into three parts: the left hollow area, the middle under-compaction area, and the right hollow area; Then, to address the integration difficulties caused by the linear thickness variation in the void area, a discretization improvement scheme is proposed, which is to subdivide the void area into small blocks of equal width and use the block centerline height as the equivalent mining thickness parameter. Finally, by superimposing the unit subsidence contributions of each block and combining the residual tilt parameters and the length of the void zone, a probability integral method prediction model based on equivalent variable mining thickness is constructed.

4. The method for predicting long-term deformation of inclined coal seams with different inclination angles on mountainous surfaces according to claim 2, characterized in that: In step S12: the long-term deformation prediction formula for near-horizontal coal seams is applicable to coal seams with a coal seam inclination angle less than 8°, and its establishment includes: First, the nearly horizontal coal seam is divided into the left hollow area, the middle insufficient compaction area and the right hollow area from left to right according to the dip direction; Then, according to the probability integral method prediction model based on equivalent variable mining thickness, the discretization height of the blocks in the left and right void areas, the residual activatable thickness of the insufficiently compacted area in the middle, and the mining thickness are taken as core parameters. Combined with the influence coefficient of the time factor and the main influencing angle tangent in the correlation coefficient table between lithology and prediction parameters, a long-term deformation prediction formula for near-horizontal coal seams is constructed.

5. The method for predicting long-term deformation of inclined coal seams with different inclination angles on the mountainous surface according to claim 2 is characterized by: In step S12: the long-term deformation prediction formula for steeply inclined coal seams is applicable to coal seams with an inclination angle greater than 45°, and its establishment includes: In view of the characteristics of rock blocks sliding and filling in the downward direction, asymmetric zoning is adopted, and the height of the caving zone and the rock expansion coefficient are introduced to calculate the equivalent mining thickness. The height of the hollow block in the upward direction, the mining impact propagation angle and the lithology parameter table are used as core parameters. Combined with the time factor, a long-term deformation prediction formula for steeply inclined coal seams is established.

6. The method for predicting long-term deformation of inclined coal seams with different inclination angles on mountainous surfaces according to claim 2, characterized in that: In step S13, the establishment of the calculation formulas for the range of the cavity area in the upward direction of the gently inclined coal seam and the inclined coal seam and the calculation formula for the range of the cavity area in the downward direction includes: Taking the dip angle α as the core variable and combining the boundary conditions of nearly horizontal coal seams and steeply inclined coal seams, a quantitative relationship between the dip angle and the range of the void area is established, that is, the range of the void area in the downhill direction decreases with the increase of the dip angle, and the range of the void area in the uphill direction increases with the increase of the dip angle. Therefore, the calculation formulas for the uphill direction of the void area range and the downhill direction of the void area range of gently inclined coal seams and inclined coal seams are established; and the calculation formulas for the uphill direction of the void area range and the downhill direction of the void area range of gently inclined coal seams are applicable to coal seams with a dip angle greater than 8° and less than 25°, and the calculation formulas for the uphill direction of the void area range and the downhill direction of the void area range of inclined coal seams are applicable to coal seams with a dip angle greater than 25° and less than 45°.

7. The method for predicting long-term deformation of inclined coal seams with different inclination angles on mountainous surfaces according to claim 2, characterized in that: In step S16: the long-term deformation prediction formula for inclined coal seams with different inclination angles on the mountain surface is established by superimposing the surface movement deformation value caused by flat land mining and the deformation increment caused by mountain mining slip. The core parameters include flat land deformation parameters, mining slip increment parameters, and mountain area characteristic parameters: the flat land deformation parameters include the flat land subsidence value, horizontal movement value, inclination value, curvature value and horizontal deformation value under the same geological mining conditions, which are obtained by the flat land probability integral prediction formula; the mining slip increment parameters include the subsidence, horizontal movement, inclination, curvature and horizontal deformation increment caused by slip; the mountain area characteristic parameters include the mountain surface characteristic coefficient, the terrain trend surface inclination, and the slip influence function.

8. The method for predicting long-term deformation of inclined coal seams with different inclination angles on mountainous surfaces according to claim 1 is characterized by: In step S20: the calculation parameters include the subsidence coefficient, the horizontal movement coefficient, the main influence radius and the main influence angle tangent, the inflection point offset, and the mining influence propagation angle.

Images