Working face evaluation method for mining thick coal seam island strip in two-wing goaf through grouting and filling

Abstract

The invention discloses a working face evaluation method for mining a thick coal seam island strip in a grouting and filling two-wing goaf, and belongs to the field of coal mine safety mining. The evaluation method comprises the following steps: constructing a non-separation grouting goaf-island strip coal pillar-goaf overlying strata space structure; and analyzing to obtain the average supporting stress # imgabs0 # of the working face of the non-separation-layer grouting island strip and the average supporting strength value # imgabs1 # of the coal pillar of the island strip, analyzing and calculating the average supporting stress # imgabs2 # of the working face of the island strip after separation-layer saturated grouting and separation-layer unsaturated grouting, and evaluating the reliability of the separation-layer saturated grouting and the separation-layer unsaturated grouting on the basis of # imgabs3 # and # imgabs4 #, wherein the average supporting stress # imgabs0 # of the working face of the non-separation-layer grouting island strip and the average supporting strength value # imgabs1 # of the working face of the non-separation-layer grouting island strip are subjected to separation-layer saturated grouting and separation-layer unsaturated grouting. From the perspective of underground mining safety and ground surface settlement control of an island strip working face, the influence of separation grouting of different degrees on island strip coal pillar mining is mainly analyzed for two-wing goaf areas, and by means of technical means such as spatial model establishment and mechanical analysis, the mining safety of the island strip working face is improved. Reliable prediction is provided for the safety and the mineability of thick coal seam island strip working face mining.

Description

Technical Field

[0001] The invention belongs to the field of safe mining of coal mines, and in particular relates to a method for evaluating a working face of an isolated island strip in a thick coal seam when grouting is used to fill two-wing goaf areas. Background Art

[0002] In order to maintain the "demand-supply" balance of coal resources, the intensity of coal mining has been continuously increased. However, with the gradual depletion of easily mined resources, in order to ensure the continuous mining of coal resources, the next step will continue to face the problems of coal mining under complex conditions, such as the safe mining of isolated strip coal pillars left by strip mining (skip mining). Strip mining technology is a coal mining method that can meet resource mining efficiency and effectively control ground subsidence. Under normal circumstances, it is easy to form a "goaf-isolated strip coal pillar-goaf" overburden space structure. The isolated strip coal pillar has a high degree of stress concentration and a high impact risk. The mining of isolated strip coal pillars often causes further stress concentration, which is easy to cause impact instability of the isolated working face of the coal pillar. In order to meet the needs of safe production, the island working face has the significant characteristics of complex overburden distribution, changeable roof movement, and coal body stress concentration. The mining of the island working face is very dangerous, and it is necessary to reliably evaluate the safety and mineability of the island strip working face. However, there are relatively few theoretical studies on the mining of the island coal pillar by grouting the two wings of the goaf of the island strip working face. Therefore, an evaluation method for the mining of thick coal seams by grouting the two wings of the goaf is proposed.

[0003] Therefore, a method for evaluating the working face of isolated island strips in thick coal seams by grouting to fill the goafs on both wings was proposed. Summary of the invention

[0004] In view of the problems existing in the prior art, the purpose of the present invention is to provide a method for evaluating the working face of isolated strips of thick coal seams mined in two-wing goaf areas by grouting filling, thereby solving the deficiencies in the prior art.

[0005] The purpose of the present invention can be achieved through the following technical solutions:

[0006] The method for evaluating the working face of isolated strips of thick coal seams by grouting and filling the two-wing goaf areas includes the following steps:

[0007] Construct the spatial structure of non-separated layer grouting goaf-isolated island strip coal pillar-goaf overburden;

[0008] Based on the spatial structure of the non-separated layer grouting goaf-isolated island strip coal pillar-goaf overburden, the average support stress of the non-separated layer grouting island strip working face is analyzed. The average support strength of isolated island strip coal pillars

[0009]

[0010] Analysis and calculation of the average bearing stress of the island strip working face after saturated grouting and unsaturated grouting of the separation layer Based on the average support stress of the non-separated layer grouting island strip working surface The average support strength of isolated island strip coal pillars Evaluate the effects of saturated grouting and unsaturated grouting.

[0011] Furthermore, the average bearing stress of the non-separated layer grouting island strip working surface The calculation formula is:

[0012]

[0013] Wherein, γ is the average bulk density of the overlying strata, D is the width of the isolated island strip coal pillar, α is the overburden movement angle, β is the overburden contact angle, L is the width of the goaf on both sides, H is the mining depth, h1 is the loading belt height, h2 is the delayed loading belt height, and h3 is the static loading belt height.

[0014] Furthermore, the average support strength of the isolated island strip coal pillar is The calculation formula is:

[0015]

[0016] Where: [σ] is the uniaxial compressive strength of the coal body, ρ is the width of the plastic zone on one side of the coal pillar, t is the width of the elastic zone on one side of the coal pillar, k is the stress concentration coefficient, M is the coal seam mining thickness, b is the coal seam mining height, δ is the coal wall side pressure coefficient, is the friction angle inside the coal body, c is the cohesion inside the coal body, f is the friction coefficient between the top and bottom plates and the coal seam contact surface, It is the internal friction angle between the contact surface between the roof and floor plates and the coal seam.

[0017] Furthermore, the average support stress of the island strip working surface after the saturated grouting of the separation layer is The calculation formula is:

[0018]

[0019] Furthermore, the average support stress of the working surface of the unsaturated grouting island strip of the delamination layer is The calculation formula is:

[0020]

[0021] Where: φ is the unsaturated grouting effect coefficient, and 0<φ<1.

[0022] Furthermore, the indicators for evaluating the effects of saturated grouting and unsaturated grouting include:

[0023] 1) Overall stability index of coal pillar after grouting of separation layer I C ':

[0024]

[0025] Among them, I C The larger the value of ', the higher the risk of impact instability of the isolated island strip coal pillar. C '<

[0026] 1.0, the coal pillar is overall stable; 1.0≤I C '<1.2, the overall weak impact hazard of the coal pillar, 1.2≤I C '<1.5; The overall medium impact hazard of the coal pillar, 1.5≤I C ', the overall strong impact hazard of the coal pillar;

[0027] 2) Working surface support stress release rate η:

[0028]

[0029] Among them, the higher the working face support stress release rate η, the better the effect of separation layer grouting on reducing the support stress of the working face;

[0030] 3) The limit width D' of isolated strip coal pillar:

[0031]

[0032] When D-D'>0, the isolated strip coal pillar is in a safe state, and when D-D'≤0, the isolated strip coal pillar is in an unsafe state;

[0033] 4) Profit of mining isolated island strip coal pillar after separation grouting a:

[0034]

[0035] Where: d is the sales profit per cubic meter of coal after deducting the cost of separation grouting and other costs; e is the sales profit per 1m 3 The cost of grouting the delamination layer; V' is the saturated grouting volume, and V" is the delamination space volume after grouting the unsaturated delamination layer.

[0036] The evaluation system of thick coal seam isolated strip working face for grouting filling two-wing goaf mining includes:

[0037] Spatial structure construction module: construct the spatial structure of non-separated layer grouting goaf-isolated island strip coal pillar-goaf overburden;

[0038] Non-separated layer grouting stress analysis module: Based on the non-separated layer grouting goaf-island strip coal pillar-goaf overburden space structure, the average support stress of the non-separated layer grouting island strip working face is analyzed and obtained. The average support strength of isolated island strip coal pillars

[0039] Separation layer grouting effect evaluation module: Analyze and calculate the average support stress of the island strip working surface after separation layer saturated grouting and separation layer unsaturated grouting Based on the average support stress of the non-separated layer grouting island strip working surface The average support strength of isolated island strip coal pillars Evaluate the effects of saturated grouting and unsaturated grouting.

[0040] A computer storage medium stores a readable program, which can execute the above-mentioned method for evaluating the working face of isolated island strips in thick coal seams by grouting and filling the two-wing goaf areas when the program is running.

[0041] An electronic device, comprising: a processor, a memory, a communication interface and a communication bus, wherein the processor, the memory and the communication interface communicate with each other through the communication bus;

[0042] The memory is used to store at least one executable instruction, and the executable instruction enables the processor to execute operations corresponding to the above-mentioned grouting filling two-wing goaf mining thick coal seam island strip working face assessment method.

[0043] A computer program product includes computer instructions, which instruct a computing device to execute operations corresponding to the above-mentioned method for evaluating the working face of an isolated island strip in thick coal seams by grouting and filling two-wing goaf areas.

[0044] Beneficial effects of the present invention:

[0045] The present invention starts from the perspective of underground mining safety and surface subsidence control of isolated strip working faces, and mainly analyzes the influence of different degrees of delamination grouting in the two-wing goaf areas on the mining of isolated strip coal pillars. By establishing spatial models and mechanical analysis and other technical means, an evaluation method suitable for delamination grouting filling of thick coal seam isolated strip working faces in the two-wing goaf areas is proposed, which provides reliability prediction for solving the safety and mineability of isolated strip working faces in thick coal seams. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, for ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0047] Figure 1 It is a spatial structure diagram of non-separated layer grouting goaf-isolated island strip coal pillar-goaf overburden;

[0048] Figure 2 This is a stress analysis model diagram of the working surface of the non-separated layer grouting island strip of the present invention;

[0049] Figure 3 This is a spatial structure diagram of the separation layer saturated grouting goaf area-isolated island strip coal pillar-goaf area overburden rock;

[0050] Figure 4 This is a stress analysis model diagram of the working surface of the saturated grouting island strip of the present invention;

[0051] Figure 5 This is a spatial structure diagram of the separation layer unsaturated grouting goaf area-isolated island strip coal pillar-goaf area overburden rock;

[0052] Figure 6 This is a stress analysis model diagram of the working surface support of the decoupled unsaturated grouting island strip of the present invention. DETAILED DESCRIPTION

[0053] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0054] Example 1

[0055] The method for evaluating the working face of isolated strips of thick coal seams by grouting and filling the two-wing goaf areas includes the following steps:

[0056] S1, construct the spatial structure of non-separated grouting goaf-isolated island strip coal pillar-goaf overburden;

[0057] Non-separated layer grouting goaf-isolated island strip coal pillar-goaf overburden space structure, such as Figure 1 As shown, the mining depth is H (unit: m), the width of the isolated island strip coal pillar is D (unit: m), the coal seam mining thickness is M (unit: m), the width of the goaf on both sides is L (unit: m), the overburden movement angle is α (unit: °), the overburden contact angle is β (unit: °), the separation angle is Δh1 (unit: m), the surface settlement height is Δh2 (unit: m), and the length of the goaf is L' (unit: m).

[0058] S2, based on the non-separation grouting goaf-island strip coal pillar-goaf overburden space structure, the average support stress of the non-separation grouting island strip working face is analyzed and obtained. The average support strength of isolated island strip coal pillars

[0059] 1. Analysis of support stress of isolated island strip coal pillar

[0060] (1) Lateral transfer stress of overburden in adjacent goaf

[0061] The lateral transfer stress of the overburden in adjacent goaf comes from the weight transfer of the overburden in the goaf. According to the stress influence effect, it can be divided into three zones: immediate loading zone, delayed loading zone and static loading zone.

[0062] Instant loading zone: As the mining work undergoes periodic bending, cracking and collapse in a short period of time, the rock formation that can promptly load the goaf and form a bearing structure. Figure 2 The rock formations in the red areas ① and ② (areas S1 and S2 respectively, and the shapes are approximately isosceles triangles), half of the weight of the rock formations in the area is borne by the goaf waste rock, and the other half is borne by the island strip working face. The height of the immediate loading zone is h1 (unit: m);

[0063] Delayed loading zone: A rock formation above the immediate loading zone that is suspended at the beginning of mining, but gradually delaminates and fractures over a long period of time as the load exceeds its own strength. Half of the weight of the delayed loading zone is borne by the island strip working face, i.e. Figure 2 The rock formations in the purple areas ③ and ④ (areas S3 and S4, respectively, and approximately trapezoidal in shape) are borne by the island strip working face, and the height of the delayed loading zone is h2 (unit: m);

[0064] Static loading zone: The rock group from above the delayed loading zone to the surface, which is less affected by mining. The rock weight distribution mechanism in this zone is the same as that in the delayed loading zone, that is, Figure 2 The rock formations in the middle yellow areas ⑤ and ⑥ (areas S5 and S6 respectively, and their shapes are approximately trapezoidal), the weight of the rock formations in the area is borne by the island strip working face, and the static load belt height is h3 (unit: m).

[0065] (2) Rock formation self-weight stress

[0066] The self-weight stress on the island strip working face comes from the weight of the rock formation above the island strip working face that is not affected by mining, that is, Figure 3 The rock formation group within the middle green area ⑦ (area S7, approximately the shape of an isosceles trapezoid).

[0067] According to the stress analysis of the overburden strata in different regions transmitted to the isolated island strip working face, the effective load area of ​​the working face is for

[0068]

[0069] According to the estimation method proposed in related research, the area S1 and S2 can be obtained as follows:

[0070]

[0071] The area of ​​regions S3 and S4 is

[0072]

[0073] The area of ​​regions S5 and S6 is

[0074]

[0075] The area S7 is

[0076] S7=(D-Hcotα)H (5)

[0077] Assume that the average bulk density of the overlying rock is γ (unit: kN / m 3 ), combined with equations (1) to (5), the average bearing stress of the working surface of the non-separated layer grouting island strip is for:

[0078]

[0079] Wherein, γ is the average bulk density of the overlying strata, D is the width of the isolated island strip coal pillar, α is the overburden movement angle, β is the overburden contact angle, L is the width of the goaf on both sides, H is the mining depth, h1 is the loading belt height, h2 is the delayed loading belt height, and h3 is the static loading belt height.

[0080] 2. Analysis of support strength of isolated island strip coal pillar

[0081] According to the methods and conclusions of relevant research, the average support strength of the isolated island strip coal pillar can be obtained. (Unit: MPa) is approximately

[0082]

[0083] Where: [σ] is the uniaxial compressive strength of the coal body (unit: MPa), ρ is the width of the plastic zone on one side of the coal pillar:

[0084] (Unit: m), t is the width of the elastic zone on one side of the coal pillar: (unit: m), k is the stress concentration factor (dimensionless), M is the coal seam mining thickness, b is the coal seam mining height (unit:

[0085] m), δ is the coal wall side pressure coefficient (dimensionless), is the friction angle in the coal body (unit: °), c is the cohesion in the coal body (unit: MPa), f is the friction coefficient between the roof and floor plates and the coal seam contact surface (dimensionless), It is the internal friction angle between the contact surface of roof and floor plates and coal seam (unit: °).

[0086] 3. Criteria for stability of isolated island strip coal pillar

[0087] According to the stress conditions of rock burst: when the average support stress acting on the isolated island strip coal pillar exceeds the average support strength, the isolated island strip coal pillar reaches the mechanical starting condition of rock burst instability. Combining equations (6) and (7), the instability criterion of the coal pillar can be obtained:

[0088]

[0089] Where: I C Defined as the overall stability index of the coal pillar, I C The larger the value of I is, the higher the risk of impact instability of the isolated island strip coal pillar will be. C <1.0, the coal pillar is overall stable; 1.0≤I C <1.2, the overall weak impact hazard of the coal pillar, 1.2≤I C <1.5; The overall medium impact hazard of the coal pillar, 1.5≤I C , the overall strong impact hazard of the coal pillar.

[0090] S3, analyze and calculate the average support stress of the island strip working surface after saturated grouting and unsaturated grouting of the separation layer Based on the average support stress of the non-separated layer grouting island strip working surface The average support strength of isolated island strip coal pillars Evaluate the effects of saturated grouting and unsaturated grouting;

[0091] The process of evaluating the effect of separation grouting is as follows:

[0092] 1. Selection of grouting location

[0093] In general, the selection of the separation layer grouting location should comply with the following principles:

[0094] ① The grouting position should be in the separation space below the key layer;

[0095] ② The grouting layer is located above the "water-conducting fracture zone" and is separated by a certain safety maintenance zone (generally 5 times the mining height) to prevent the slurry from entering the goaf and affecting the safety of coal mine production.

[0096] On the basis of meeting the above conditions, there are two delamination grouting schemes to choose from, namely, one-time grouting below the thick and hard key layer and multi-layer grouting. However, compared with the disadvantages of multi-layer grouting, such as many grouting times, complex process, time-consuming and labor-intensive, the one-time grouting below the thick and hard key layer is simple in process and convenient in construction. It can also directly control the thick and hard key layer to more effectively control surface settlement. Therefore, one-time grouting below the thick and hard key layer should be selected.

[0097] 2. Determination of grouting pressure

[0098] The grouting pressure should be no less than the natural ground pressure of the strata above the grouting filling layer, and no more than the rock stratum water-proof pressure from the grouting filling layer to the mining working face, so as to achieve the goal of stabilizing the surface and preventing slurry from collapsing underground. The principle is that in order to control the sinking of the overlying key layer, the grouting pressure must be greater than the self-weight of the overlying rock. The grouting pressure is expressed as

[0099] P 隔 >P 注 ≥P 地 (9)

[0100] Where: P 隔 P is the water-proof pressure from the grouting filling layer to the mining working face (unit: MPa); 注 is the grouting filling pressure (unit: MPa); P 地 It is the natural pressure of the formation above the grouting filling layer (unit: MPa).

[0101] In actual construction, the grouting pressure P at the grouting borehole can be controlled. 孔 To control the ground subsidence

[0102] P 孔 =P 注 -H1γ1≥P 地 -H1γ1=H1(γ-γ1) (10)

[0103] Where: P 孔 is the orifice pressure of the grouting hole (unit: MPa); H1 is the depth from the surface to the grouting filling layer (unit: m); γ is the comprehensive bulk density of the stratum above the grouting filling layer (unit: kN / m 3 ), γ1 is the bulk density of the filling slurry (unit: kN / m 3 ).

[0104] 3. Evaluation of the effect of saturated grouting in the separation layer

[0105] (1) Analysis of spatial structure changes

[0106] like Figure 3As shown in the figure, under ideal conditions, when the grouting volume reaches the saturated grouting volume, the rock layer in the "delayed loading zone" below the separation space is compressed and broken, and the broken rock and the "immediate loading zone" are fully compacted. At the same time, the deformation of the "static loading zone" above the separation space is fully affected by the saturated grouting of the separation layer, that is, the surface settlement disappears completely, and the opening of the separation space reaches the thickness of the mined coal seam, that is, Δh3=M. The cross-sectional shape of the separation space changes from "crescent shape" to "trapezoid shape", forming a new overburden space structure. At this time, the cross-sectional area S' of the separation space is:

[0107] S'=[L+(h1+h2)cotα-(h1+h2-Vh2)cotβ]Vh3 (11)

[0108] The saturated grouting volume V' is

[0109] V'=S'L'=[L+(h1+h2)cotα-(h1+h2-Vh2)cotβ]Vh3L' (12)

[0110] In order to effectively reduce ground settlement, the grouting volume should be as close to the saturated grouting volume as possible.

[0111] (2) Analysis of changes in coal pillar support stress

[0112] like Figure 4 As shown in the figure, the support stress of the island strip working face is analyzed under the two cases of no delamination grouting before mining and saturated delamination grouting before mining. The following conclusions can be drawn: after saturated delamination grouting, the grouting area can form a sufficient "downward pressure + upward support" effect on the rock strata above and below the delamination area, thereby reducing the support stress of the island strip working face.

[0113] ① Downward pressure effect: Through saturated grouting of the separation layer, the original "delayed loading zone" is fractured downward, and the rock layer and the original "immediate loading zone" are continuously broken downward to change their stress transfer mechanism, so that the weight of the rock layer of the original "delayed loading zone" and "immediate loading zone" is completely transferred to the goaf;

[0114] ② Upward lifting effect: through saturated grouting of the separation layer, the thick and hard key layer and the rock layer on the surface are lifted upward, so that the original "static load belt" presents a "uniform load" state, changing the lateral stress transfer mechanism of the "static load belt" and causing most of it to transfer to the goaf;

[0115] After saturated grouting of the separation layer, the supporting stress of the isolated island strip working face is the self-weight stress of the rock formation and the small part of the rock formation weight left by the original "static load belt" after the "upward effect" ( Figure 5 The weight of the rock formations in the middle yellow areas ⑧ and ⑨ is S8 and S9, and the shape is approximately a right triangle.

[0116] The area of ​​regions S8 and S9 is

[0117]

[0118] The average support stress of the island strip working face after saturated grouting of the separation layer is for:

[0119]

[0120] Through saturated grouting of delamination, the exposed state of the spatial structure of the overburden in the goaf is improved, and the supporting stress of the isolated island strip working face is greatly "released". Saturated grouting of delamination ensures the stability of the coal pillar of the isolated island strip and reduces the possibility of impact instability of the isolated island strip working face. Therefore, the grouting volume should be as close to the saturated grouting volume as possible.

[0121] 4. Evaluation of the effect of unsaturated grouting in separation layer

[0122] (1) Analysis of spatial structure changes

[0123] like Figure 5 As shown in the figure, in order to form a certain "downward pressure + upward support" effect on the rock layers above and below the delamination area, the amount of unsaturated grouting in the delamination should be greater than the initial delamination space volume V. At this time, the delamination opening is Vh4 (unit: m), and the cross-sectional area of ​​the delamination space should be an enlarged "crescent shape" (its area can be approximately calculated as a triangle). Then the unsaturated delamination grouting volume V" should meet the following requirements

[0124] V<V”<V' (15)

[0125] Where: V is the volume of the initial separation space: (Unit: m 3 ), V” is the volume of the stratum space after grouting of unsaturated stratum: (Unit: m 3 ).

[0126] The spatial structure of the overburden rock was analyzed in two cases: no delamination grouting before mining and unsaturated delamination grouting before mining. After unsaturated delamination grouting, the grouting area can form a certain "downward pressure + upward support" effect on the rock strata above and below the delamination area, which is manifested in that the ground settlement height can be reduced to a certain extent (from Δh2 to Δh5), the opening of the delamination space can be increased (from Δh1 to Δh4) and the rock strata below the delamination space can be compacted to a certain extent.

[0127] (2) Analysis of changes in coal pillar support stress

[0128] like Figure 6As shown in the figure, the support stress of the island strip working face is analyzed under the two cases of no delamination grouting before mining and unsaturated delamination grouting before mining. The following conclusions can be drawn: after unsaturated delamination grouting, the grouting area can form a certain "downward pressure + upward support" effect on the rock strata above and below the delamination area, thereby reducing the support stress of the island strip working face.

[0129] At this time, the lateral stress transfer mechanism of the overburden in the adjacent goaf is consistent with that when there is no grouting in the delamination layer, so the average support stress of the working face of the delamination unsaturated grouting island strip is for:

[0130]

[0131] Where: φ is the unsaturated grouting effect coefficient (dimensionless), 0<φ<1, and the specific value needs to be further analyzed in combination with the actual project.

[0132] 5. Evaluation index of separation layer grouting effect

[0133] (1) Safety index (the index is met as safe, and the index is not met as unsafe) ), the following is an explanation of the three sub-indicators of the safety index: the overall stability index of the coal pillar (safe m1, unsafe ), working surface support stress release rate (safe m2, unsafe ), the ultimate coal pillar width (safe m3, unsafe ).

[0134] ① Overall stability index of coal pillar after grouting of separation layer I C '

[0135] According to the stress conditions for rock burst: when the average support stress acting on the isolated island strip coal pillar exceeds the average support strength of the coal body, the coal pillar reaches the mechanical starting condition of rock burst instability. The stability criterion of the isolated island strip coal pillar during grouting of saturated and unsaturated delamination can be obtained by combining equations (7), (8), (14) and (16):

[0136]

[0137] I C ' is defined as the overall stability index of the coal pillar after grouting of the separation layer, I C The larger the value of ', the higher the risk of impact instability of the isolated island strip coal pillar. C '<1.0, the coal pillar is overall stable; 1.0≤I C '<1.2, the overall weak impact hazard of the coal pillar, 1.2≤I C '<1.5; The overall medium impact hazard of the coal pillar, 1.5≤I C', the overall strong impact hazard of the coal pillar.

[0138] From a security perspective, I C The smaller the value of ', the lower the risk of impact instability of the isolated strip coal pillar. After the separation grouting, the isolated strip coal pillar is affected by the "downward pressure + upward support" effect of the separation grouting area, and the overall stability index of the coal pillar is reduced (the reduction effect is affected by factors such as grouting rate), and the safety of the coal pillar is improved. C When '=1, the critical value of overall stability of the coal pillar is reached.

[0139] From the perspective of mineability, the evaluation of the mineability of isolated island strip coal pillars needs to comprehensively consider factors such as coal pillar stability, geological conditions, and mining methods. C When the overall stability index of the coal pillar is slightly higher, that is, 1<I C '≤1.2, the coal pillar is not mineable, but other technical means (such as high-position roof blasting, roof pre-splitting, etc.) can be used to make the unmineable island strip coal pillar mineable; when the overall stability index of the coal pillar is too high, that is, 1.2<I C ', the possibility of overall impact instability of the coal pillar is high and it is not mineable.

[0140] Therefore, on the basis of ensuring the safety and mineability of the isolated island strip coal pillar, the critical value of the overall stability index of the coal pillar after grouting is C '=1.2.

[0141] ②Working surface support stress release rate η

[0142] The working face support stress release rate is the ratio of the reduction value of the support stress on the island strip working face after saturated and unsaturated grouting of the separation layer to the support stress before grouting:

[0143]

[0144] The working face support stress release rate is a sensitive indicator that can accurately reflect the improvement of the support stress of the island strip working face by delamination grouting. The higher the working face support stress release rate, the better the effect of delamination grouting on reducing the support stress of the working face, and the more it can ensure the safety and feasibility of mining the island strip coal pillar. Ideally, the working face support stress release rate should be infinitely close to 100%.

[0145] However, the support stress release rate of the working face is greatly affected by the mining depth. When the working face is in a deep well state (buried depth exceeds 700m), the support stress release effect caused by delamination grouting is relatively large. When the stress release rate η>50%, the safety index is reached; when the working face is in a shallow buried state (buried depth does not exceed 700m), the stress release effect caused by delamination grouting is relatively small. When the stress release rate reaches 30% to 50%, the safety index is reached.

[0146] ③Limit width of isolated island strip coal pillar D'

[0147] During the mining process of isolated strip coal pillars after grouting, the overall stability index of the coal pillar needs to be continuously monitored. When the overall stability index of the coal pillar reaches the critical value, the limit width D' of the isolated strip coal pillar is:

[0148]

[0149] In the formula: Taking safety and mineability into consideration, the overall stability index of the coal pillar after grouting can be taken as I C '=1.2, but the specific value needs to be further analyzed in combination with the actual project.

[0150] When D-D'>0, the island strip coal pillar is in a safe state, that is, it is mineable. When D-D'≤0, the island strip coal pillar is in an unsafe state, that is, it is not mineable. At this time, technical solutions such as high-position roof blasting / pre-splitting can be used to reduce or transfer the overburden load, so that the unmineable island strip coal pillar can reach the mineable conditions and become mineable.

[0151] (2) Economic indicators (profitable, unprofitable) )

[0152] Considering factors such as coal mining profit, mining input cost and separation grouting cost, according to the economic benefit analysis, whether the mining of isolated strip coal pillars is profitable, the profit of mining isolated strip coal pillars after separation grouting is a

[0153]

[0154] Where: d is the cost per m after deducting the cost of grouting and other costs (such as mining material costs, labor costs, depreciation costs, maintenance costs, etc.) 3 Coal sales profit (unit: yuan / m 3 );e is every 1m 3 The cost of grouting of separation layer includes the manpower, material and financial resources related to grouting (unit: yuan / m 3 ). V' is the saturated grouting volume, and V" is the volume of the stratum space after grouting of the unsaturated stratum.

[0155] When a>0, mining of isolated strip coal pillars is profitable; when a≤0, mining of isolated strip coal pillars is not profitable, and the plan of suspending stratum grouting and filling mining (slow mining) should be adopted, and other economically applicable mining technology plans can be adopted.

[0156] Finally, based on the evaluation results, the mining strategy is selected.

[0157] The mining of isolated strip coal pillars requires comprehensive safety indicators (safe m, unsafe m ) and economic feasibility indicators (profitable, unprofitable ) for evaluation, the safety index includes three sub-indicators: the overall stability index of the coal pillar (safe m1, unsafe m2, ), working surface support stress release rate (safe m2, unsafe ), the ultimate coal pillar width (safe m3, unsafe ), then the comprehensive evaluation results of the mining of the isolated island strip coal pillar (mineable, unmineable ) can be expressed as

[0158]

[0159] Where: “-”, “+” and “.” represent “not”, “or” and “and” in logical operations respectively, the same below. The evaluation results are shown in Table 1.

[0160] Table 1 Comprehensive evaluation results

[0161]

[0162] Relevant conclusions and suggestions:

[0163] ① After grouting of the separation layer, the isolated strip coal pillar meets the safety and economic indicators, and the separation layer grouting filling mining can be carried out.

[0164] ② After the separation grouting, the isolated strip coal pillar meets the economic indicators, but fails to reach the safety indicators. It is necessary to take other measures (such as high-position roof blasting / pre-splitting, etc.) based on the actual project to further improve the safety of the isolated strip coal pillar and further evaluate it.

[0165] ③ If the isolated strip coal pillar does not meet the economic indicators after delamination grouting, the delamination grouting filling mining (slow mining) plan should be adopted. Other economical and applicable mining technology plans can be adopted, or an evaluation can be carried out when the coal price rises or the delamination grouting cost decreases.

[0166] Based on similar inventive concepts, an embodiment of the present invention also provides a computer storage medium storing a readable program, which, when running, can execute the above-mentioned method for evaluating the working face of isolated strips of thick coal seams mined in two-wing goafs by grouting.

[0167] Based on similar inventive concepts, an embodiment of the present invention provides an electronic device, comprising: a processor, a memory, a communication interface and a communication bus, wherein the processor, the memory and the communication interface communicate with each other through the communication bus;

[0168] The memory is used to store at least one executable instruction, and the executable instruction enables the processor to execute operations corresponding to the above-mentioned grouting filling two-wing goaf mining thick coal seam island strip working face assessment method.

[0169] Based on similar inventive concepts, an embodiment of the present invention also provides a computer program product, including computer instructions, which instruct a computing device to execute operations corresponding to the above-mentioned method for evaluating the working face of an isolated island strip in thick coal seams by grouting and filling two-wing goaf areas.

[0170] Example 2

[0171] In this embodiment, a grouting filling two-wing goaf mining thick coal seam isolated island strip working face assessment system is proposed, which specifically includes:

[0172] Spatial structure construction module: construct the spatial structure of non-separated layer grouting goaf-isolated island strip coal pillar-goaf overburden;

[0173] Non-separated layer grouting stress analysis module: Based on the non-separated layer grouting goaf-island strip coal pillar-goaf overburden space structure, the average support stress of the non-separated layer grouting island strip working face is analyzed and obtained. The average support strength of isolated island strip coal pillars

[0174] Separation layer grouting effect evaluation module: Analyze and calculate the average support stress of the island strip working surface after separation layer saturated grouting and separation layer unsaturated grouting Based on the average support stress of the non-separated layer grouting island strip working surface The average support strength of isolated island strip coal pillars Evaluate the effects of saturated grouting and unsaturated grouting.

[0175] The method of the present invention may be implemented in hardware, firmware, or as software or computer code that may be stored in a recording medium (such as a CDROM, RAM, floppy disk, hard disk, or magneto-optical disk), or as computer code that is originally stored in a remote recording medium or a non-temporary machine-readable medium downloaded over a network and will be stored in a local recording medium, so that the method described herein may be stored in such software processing on a recording medium using a general-purpose computer, a dedicated processor, or programmable or dedicated hardware (such as an ASIC or FPGA). It is understood that a computer, processor, microprocessor controller, or programmable hardware includes a storage component (e.g., RAM, ROM, flash memory, etc.) that can store or receive software or computer code, and when the software or computer code is accessed and executed by a computer, processor, or hardware, the method described herein is implemented. In addition, when a general-purpose computer accesses the code for implementing the method shown herein, the execution of the code converts the general-purpose computer into a dedicated computer for executing the method shown herein.

[0176] The above shows and describes the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments, and the above embodiments and descriptions are only for explaining the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, and these changes and improvements all fall within the scope of the present invention to be protected.

Claims

1. A method for evaluating the working face of isolated strips of thick coal seams by grouting and filling the two-wing goaf areas, characterized in that: The following steps are involved: Construct the spatial structure of non-separated layer grouting goaf-isolated island strip coal pillar-goaf overburden; Based on the spatial structure of the non-separated layer grouting goaf-isolated island strip coal pillar-goaf overburden, the average support stress of the non-separated layer grouting island strip working face is analyzed. The average support strength of isolated island strip coal pillars Analysis and calculation of the average bearing stress of the island strip working face after saturated grouting and unsaturated grouting of the separation layer Based on the average support stress of the non-separated layer grouting island strip working surface The average support strength of isolated island strip coal pillars Evaluate the effects of saturated grouting and unsaturated grouting.

2. The method for evaluating the working face of isolated island strips in thick coal seams by grouting and filling two-wing goaf areas according to claim 1 is characterized in that: The average support stress of the non-separated layer grouting island strip working surface The calculation formula is: Wherein, γ is the average bulk density of the overlying strata, D is the width of the isolated island strip coal pillar, α is the overburden movement angle, β is the overburden contact angle, L is the width of the goaf on both sides, H is the mining depth, h1 is the loading belt height, h2 is the delayed loading belt height, and h3 is the static loading belt height.

3. The method for evaluating the working face of isolated island strips in thick coal seams by grouting and filling two-wing goaf areas according to claim 2 is characterized in that: The average supporting strength of the isolated island strip coal pillar The calculation formula is: Where: [σ] is the uniaxial compressive strength of the coal body, ρ is the width of the plastic zone on one side of the coal pillar, t is the width of the elastic zone on one side of the coal pillar, k is the stress concentration coefficient, M is the coal seam mining thickness, b is the coal seam mining height, δ is the coal wall side pressure coefficient, is the friction angle inside the coal body, c is the cohesion inside the coal body, f is the friction coefficient between the top and bottom plates and the coal seam contact surface, It is the internal friction angle between the contact surface between the roof and floor plates and the coal seam.

4. The method for evaluating the working face of isolated island strips in thick coal seams by grouting and filling two-wing goaf areas according to claim 3 is characterized in that: The average support stress of the island strip working surface after saturated grouting of the separation layer The calculation formula is:

5. The method for evaluating the working face of isolated island strips in thick coal seams by grouting and filling two-wing goaf areas according to claim 4 is characterized in that: The average support stress of the unsaturated grouting island strip working surface The calculation formula is: Where: φ is the unsaturated grouting effect coefficient, and 0<φ<1.

6. The method for evaluating the working face of isolated island strips in thick coal seams by grouting and filling two-wing goaf areas according to claim 5 is characterized in that: The indicators for evaluating the effects of saturated grouting and unsaturated grouting in separation layers include: 1) Overall stability index of coal pillar after grouting of separation layer I C ': Among them, I C The larger the value of ', the higher the risk of impact instability of the isolated island strip coal pillar. C '< 1.0, the coal pillar is overall stable; 1.0≤I C '<1.2, the overall weak impact hazard of the coal pillar, 1.2≤I C '<1.5; The overall medium impact hazard of the coal pillar, 1.5≤I C ', the overall strong impact hazard of the coal pillar; 2) Working surface support stress release rate η: Among them, the higher the working face support stress release rate η, the better the effect of separation layer grouting on reducing the support stress of the working face; 3) The limit width D' of isolated strip coal pillar: When D-D'>0, the isolated strip coal pillar is in a safe state, and when D-D'≤0, the isolated strip coal pillar is in an unsafe state; 4) Profit of mining isolated island strip coal pillar after separation grouting a: Where: d is the sales profit per cubic meter of coal after deducting the cost of separation grouting and other costs; e is the sales profit per 1m 3 The cost of grouting the delamination layer; V' is the saturated grouting volume, and V" is the delamination space volume after grouting the unsaturated delamination layer.

7. Grouting filling two-wing goaf mining thick coal seam island strip working face assessment system, characterized by: include: Spatial structure construction module: construct the spatial structure of non-separated layer grouting goaf-isolated island strip coal pillar-goaf overburden; Non-separated layer grouting stress analysis module: Based on the non-separated layer grouting goaf-island strip coal pillar-goaf overburden space structure, the average support stress of the non-separated layer grouting island strip working face is analyzed and obtained. The average support strength of isolated island strip coal pillars Separation layer grouting effect evaluation module: Analyze and calculate the average support stress of the island strip working surface after separation layer saturated grouting and separation layer unsaturated grouting Based on the average support stress of the non-separated layer grouting island strip working surface The average support strength of isolated island strip coal pillars Evaluate the effects of saturated grouting and unsaturated grouting.

8. A computer storage medium storing a readable program, characterized in that: When the program is running, it can execute the method for evaluating the working face of isolated island strips in thick coal seams mined by grouting and filling two-wing goaf areas as described in any one of claims 1 to 6.

9. An electronic device, characterized in that: include: A processor, a memory, a communication interface and a communication bus, wherein the processor, the memory and the communication interface communicate with each other via the communication bus; The memory is used to store at least one executable instruction, and the executable instruction enables the processor to perform operations corresponding to the method for evaluating the working face of isolated island strips in thick coal seams mined in two-wing goaf areas with grouting as described in any one of claims 1-6.

10. A computer program product comprising computer instructions, characterized in that: The computer instructions instruct the computing device to execute operations corresponding to the method for evaluating the working face of isolated island strips in thick coal seams mined by grouting and filling two-wing goaf areas as described in any one of claims 1-6.

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