A method for grouting and filling to reduce subsidence of coal pillar-free overburden strata

Abstract

The application discloses a coal pillar-free overburden strata separation grouting and filling subsidence reduction method, which comprises the following steps: determining the horizon of all key layers in a panel range, the grouting key layer in overburden strata, the breaking distance of the grouting key layer and the mining width of the first mining face; determining the equivalent mining width according to the allowable mining width of the grouting key layer by using the fulcrum effect of the caving zone compaction area, calculating the maximum face length of the replacement working face, determining the length of the successive working face in the face length range, and obtaining an overburden strata separation filling mining system; no coal pillar is left between the working faces of the overburden strata separation filling mining system; the first mining face is mined, and the lower part of the key layer is grouted after the mining; the lower part of the key layer of the replacement working face is grouted when the replacement working face is mined; the remaining working faces are sequentially subjected to separation grouting and filling mining until the whole panel is mined; and no coal pillar is left between all the working faces. The application improves the grouting and filling subsidence reduction effect, further improves the recovery rate of coal resources in a mine, and reduces the mining and excavation cost.

Description

Technical Field

[0001] This invention belongs to the field of coal seam mining technology, and in particular relates to a method for reducing settlement by grouting and filling overburden separation without coal pillars. Background Technology

[0002] With the increase in coal mining years, the contradiction between surface structures and coal seams is becoming increasingly prominent. Existing overburden separation grouting technology, which uses coal pillars to isolate the working face, is increasingly favored by coal mines due to its advantages such as low cost, relatively independent mining and filling, and good surface subsidence reduction effect. At the same time, to reduce resource waste, pillarless mining is becoming increasingly common in coal mining, which brings challenges to overburden separation grouting for subsidence reduction.

[0003] Grouting for subsidence reduction under coal pillar-free conditions breaks the theoretical basis of this method, namely the grouting support system with fixed beams at both ends. The mining conditions at the working face undergo significant changes. Because the adjacent goaf loses the support of coal pillars, the fundamental conditions of the critical layer theory with fixed beams at both ends are also lost, leading to a rapid increase in the width of the grouting working face. According to the critical layer theory, the failure distance of the critical layer is often insufficient to support the mining width of two working faces. The failure of the critical layer, forming a cantilever beam, is inevitable, resulting in poor subsidence reduction and secondary geological disasters such as grout leakage at the surface. Summary of the Invention

[0004] To address the aforementioned technical problems, this invention proposes a pillarless overburden separation grouting method for reducing settlement, employing an equivalent mining width to create a discontinuous separation structure. This achieves the required breakage distance for a simply supported beam in pillarless overburden separation grouting, thus realizing the goal of pillarless overburden separation grouting for settlement reduction. This solves the resource waste problem caused by leaving coal pillars in existing overburden separation grouting technologies and improves the working face recovery rate.

[0005] To achieve the above objectives, the present invention provides a method for reducing settlement by grouting and filling overburden without coal pillars, comprising:

[0006] Determine the positions of all key strata within the panel area, the key grouting strata in the overburden, the fracture distance of the key grouting strata, and the width of the first mining face;

[0007] Based on the allowable mining width of the key grouting layer and utilizing the principle of the fulcrum effect of the compacted zone of the caving zone, the equivalent mining width is determined, the length of the successor working face is calculated, and the overburden separation and backfilling mining system is obtained; no coal pillars are left between the working faces of the overburden separation and backfilling mining system.

[0008] The first mining face is mined, followed by grouting of the lower part of the key layer;

[0009] When taking over a working face, grouting should be carried out in the lower part of the key layer of the working face.

[0010] The remaining working faces will be mined sequentially with grouting and backfilling until the entire panel is mined out; no coal pillars will be left between any of the working faces.

[0011] Preferably, the roadway layout for the coal pillar-free overburden separation grouting mining method is a goaf-retaining roadway layout.

[0012] Preferably, the height of the grouting key layer from the coal seam is greater than the sum of the height of the water-conducting fracture zone and the height of the safety isolation zone, and the key layer with the deepest burial depth among all key layers is selected as the grouting key layer.

[0013] Preferably, the formula for calculating the failure distance of the key grouting layer is as follows:

[0014]

[0015] In the formula: L1 represents the failure of the critical layer under grouting conditions; δ1 represents the tensile strength of the subcritical layer; h1 represents the thickness of the subcritical layer; and q1 represents the pressure exerted by the upper formation on the critical layer when it is not grouted.

[0016] Preferably, the formula for the width of the first mining face is:

[0017] W k =L k +2H k / tanθ

[0018] In the formula: W k L represents the maximum allowable mining width of the working face during grouting and filling of the Kth critical layer; K H represents the critical layer fracture distance; k θ represents the distance between the key stratum and the working coal seam; θ is the fracture angle of the overlying strata of the coal seam.

[0019] Preferably, the formula for determining the equivalent mining width based on the allowable mining width of the grouting key layer is as follows:

[0020]

[0021] In the formula: ε is the injection-production ratio; L 等效 L is the equivalent cut length of the working face; 首采 d is the length of the first working face cut. sc The width of the air intake roadway between the first mining face and the successor mining face is m; L 接替 The length of the cut eye is to replace the working face.

[0022] Preferably, the formula for calculating the length of the replacement working face is as follows:

[0023]

[0024] Wherein, the equivalent mining width value is taken as the limit mining width value allowed by the grouting key layer, dsc The dimensions for the layout of pillarless roadways in a mine.

[0025] Preferably, the process of obtaining the overburden delamination and backfilling mining system includes:

[0026] The width of the replacement working face is calculated, and a return airway is arranged according to the width of the replacement working face to obtain the first mining face mining system and "Y"-shaped ventilation system that enable the working face to meet the conditions for filling mining.

[0027] Preferably, the process of grouting the lower part of the key layer immediately following the initial mining face mining includes:

[0028] Following the grouting of the working face, grouting work is carried out when the delamination just begins to form at the beginning of the working face mining, and the positions of the first row of grouting boreholes are arranged.

[0029] During construction, the timing of the initial grouting is determined based on the amount of water loss from the borehole. The initial grouting is carried out when the amount of water loss from the borehole suddenly increases to exceed the preset threshold.

[0030] The positions of the first row of grouting boreholes are arranged according to the following formula:

[0031] S=H / tanθ

[0032] In the formula: S is the planar distance from the cut-off point and the roadway; H is the distance from the grouting layer to the roof of the coal seam; θ is the fracture angle of the overlying strata of the coal seam.

[0033] Preferably, when grouting is performed on the lower part of the key layer of the replacement working face during mining, the arrangement of grouting boreholes is based on the equivalent mining width. The borehole arrangement is based on the centerline of the equivalent mining width and is offset towards the first mining face.

[0034] Compared with the prior art, the present invention has the following advantages and technical effects:

[0035] This invention eliminates the supporting coal pillars between the overburden separation grouting working faces and adopts an equivalent mining width method for pillarless overburden separation grouting mining, forming a discontinuous separation structure. The replacement working face is always in a state of insufficient mining, which improves the grouting filling and sedimentation reduction effect, further improves the coal resource recovery rate of the mine, and reduces mining costs.

[0036] This invention limits the layout width of the continuous working face in the form of equivalent mining width, forming a discontinuous delamination structure, which meets the requirements of the simply supported beam for delamination grouting for fracture distance, thereby achieving the purpose of reducing settlement by delamination grouting without coal pillars.

[0037] The method of this invention eliminates the need for coal pillars between working faces, significantly improving the recovery rate of the panel area.

[0038] This invention extends the service life of auxiliary ventilation tunnels and saves on tunnel excavation costs. Attached Figure Description

[0039] The accompanying drawings, which form part of this application, are used to provide a further understanding of this application. The illustrative embodiments and descriptions of this application are used to explain this application and do not constitute an undue limitation of this application. In the drawings:

[0040] Figure 1 This is a plan view of the coal pillarless working face according to an embodiment of the present invention;

[0041] Figure 2 This is a diagram illustrating the coal pillar-free overburden separation grouting method for reducing settlement according to an embodiment of the present invention;

[0042] Figure 3 This is a structural diagram of the post-mining compaction zone of the working face according to an embodiment of the present invention;

[0043] Figure 4 This is a diagram showing the layout of the grouting boreholes for coal pillar-free overburden separation according to an embodiment of the present invention.

[0044] Among them, 1. Panel return airway; 2. Panel main haulage roadway; 3. Panel auxiliary haulage roadway; 4. First mining face; 5. First replacement working face; 6. Transport roadway; 7. Auxiliary intake airway; 8. Return airway; 9. Equivalent mining width; 10. Boundary line of compacted zone of first mining face; 11. Second replacement working face; 12. Compacted zone; 13. Uncompacted zone; 14. Delamination space; 15. Grouting subcritical layer; 16. Subcritical layer; 17. Main critical layer; 18. Grouting borehole; 19. Boundary line between weak layer and bedrock; 20. Surface; 21. Center line of first mining face; 22. Center line of equivalent mining width of replacement working face; 23. First row of boreholes of first mining face; 24. Boreholes of replacement face. Detailed Implementation

[0045] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. This application will now be described in detail with reference to the accompanying drawings and embodiments.

[0046] It should be noted that the steps shown in the flowchart in the accompanying drawings can be executed in a computer system such as a set of computer-executable instructions, and although a logical order is shown in the flowchart, in some cases the steps shown or described may be executed in a different order than that shown here.

[0047] like Figure 1-4 As shown, this embodiment provides a method for reducing settlement by grouting and filling overburden without coal pillars, including:

[0048] Determine the positions of all key strata within the panel area, the key grouting strata in the overburden, the fracture distance of the key grouting strata, and the width of the first mining face; the panel area includes panel return airway 1, panel main haulage airway 2, and panel auxiliary haulage airway 3.

[0049] Based on the allowable mining width of the key grouting layer and utilizing the principle of the fulcrum effect of the compacted zone of the caving zone, the equivalent mining width is determined, the length of the successor working face is calculated, and the overburden separation and backfilling mining system is obtained; no coal pillars are left between the working faces of the overburden separation and backfilling mining system.

[0050] The first mining face was mined four times, followed by grouting of the lower part of the key layer;

[0051] When mining a replacement working face, grouting is carried out in the lower part of the key layer of the replacement working face; the replacement working faces include the first replacement working face 5 and the second replacement working face 11.

[0052] The remaining working faces will be mined sequentially with grouting and backfilling until the entire panel is mined out; no coal pillars will be left between any of the working faces.

[0053] This embodiment determines the key grouting layer based on geological conditions, determines the width of the first mining face based on the allowable mining width of the key layer, and determines the width of the successor mining face based on the principle of equivalent mining width, thus forming a mining system. A pillarless layout is adopted between the mining faces. As mining progresses, grouting is injected into the layer below the target key layer through grouting holes. With the mining of new successor mining faces and the filling of the grouting layer, a discontinuous grouting structure is formed, achieving the required breakage distance for a simply supported beam grouting system, thereby realizing pillarless overburden grouting for settlement reduction.

[0054] Furthermore, the roadway layout for coal pillar-free overburden separation grouting mining is a goaf-retaining layout.

[0055] Furthermore, based on geological exploration data, the positions of all key strata within the panel area were determined.

[0056] Typically, before coal seam mining, the geological conditions above the coal seam are analyzed, and the key strata above the coal seam are determined based on the obtained geological exploration data.

[0057] like Figure 2 As shown, assuming that the geological data identifies three key layers within the panel area, namely the grouting sub-key layer 15, the sub-key layer 16, and the main key layer 17, it also includes the delamination space 14, the boundary between the weak layer and the bedrock 19, the surface 20, the centerline of the first mining face 21, the centerline of the equivalent mining width of the successor working face 22, and the borehole of the successor face 24. The characteristics of these key layers are shown in Table 1 below.

[0058] Table 1

[0059]

[0060] Furthermore, the height of the key grouting layer from the coal seam is greater than the sum of the heights of the water-conducting fracture zone and the safety isolation zone. Selecting the deepest key grouting layer as the key grouting layer is beneficial for improving the grouting effect. Assuming the sum of the heights of the water-conducting fracture zone and the safety isolation zone is 150m, then the key grouting layer is selected as the sub-key grouting layer 15.

[0061] Furthermore, the key grouting layer for the successor working face should be selected in the same manner as the first working face to achieve the best grouting effect.

[0062] like Figure 1 As shown, it includes the boundary line of the compacted zone of the first mining face 10, the compacted zone 12, and the uncompacted zone 13.

[0063] Furthermore, the formula for calculating the failure distance of the key grouting layer is as follows:

[0064]

[0065] In the formula: L1 represents the failure of the critical layer under grouting conditions; δ1 represents the tensile strength of the subcritical layer; h1 represents the thickness of the subcritical layer; and q1 represents the pressure exerted by the upper formation on the critical layer when it is not grouted.

[0066] Based on the data in Table 1, the calculated failure distance of the key grouting layer is 47.67m.

[0067] Furthermore, the formula for the width of the first mining face is as follows:

[0068] W k =L k +2H k Calculate / tanθ

[0069] In the formula: W k L represents the maximum allowable mining width of the working face during grouting and filling of the Kth critical layer; K H represents the critical layer fracture distance; k θ represents the distance between the key stratum and the working coal seam; θ is the fracture angle of the overlying strata of the coal seam.

[0070] Based on the data in Table 1, the allowable maximum mining width at the grouting and filling working face is calculated to be 209.72m. We take 209m as... Figure 1 The width of the first surface 4 in the middle.

[0071] Furthermore, the formula for determining the equivalent mining width based on the allowable mining width of the grouting key layer is as follows:

[0072]

[0073] In the formula: ε is the injection-production ratio; L 等效 L is the equivalent cut length of the working face;首采 d is the length of the first working face cut. sc L is the width of the air intake roadway between the first working face and the succeeding working face. 接替 The length of the cut eye is to replace the working face.

[0074] like Figure 1 As shown, it includes a transport roadway 6, an auxiliary air intake roadway 7, and a return air roadway 8.

[0075] Furthermore, the formula for calculating the length of the replacement working face is as follows:

[0076]

[0077] Wherein, the equivalent mining width value is taken as the limit mining width value allowed by the grouting key layer, d sc The dimensions for the layout of pillarless roadways in a mine.

[0078] Furthermore, the process of obtaining the overburden delamination and backfill mining system includes:

[0079] The width of the replacement working face is calculated, and the return airway is arranged according to the width of the replacement working face to obtain the first mining face mining system and "Y" type ventilation system that enable the working face to have the conditions for filling mining.

[0080] Specifically, the calculated width of the work face for the replacement is 151m. Figure 2 In this process, since the first working face 4 and the first successor working face 5 adopt pillarless mining and share a roadway, the location of the roadway is determined based on the calculated working face width. This forms the first working face mining system and the "Y"-shaped ventilation system, enabling the working face to meet the conditions for backfilling mining.

[0081] Furthermore, the process of grouting the lower part of the key stratum following the fourth mining operation at the first mining face includes:

[0082] Following the grouting of the working face, grouting work is carried out when the delamination just begins to form at the beginning of the working face mining, and the positions of the first row of grouting boreholes are arranged.

[0083] During construction, the timing of the initial grouting is determined based on the amount of water loss from the borehole. The initial grouting is carried out when the amount of water loss from the borehole suddenly increases to exceed the preset threshold.

[0084] The positions of the first row of grouting boreholes are arranged according to the following formula, such as... Figure 4 The first row of boreholes in the first mining face, number 23:

[0085] S=H / tanθ

[0086] In the formula: S is the planar distance from the cut-off point and the roadway; H is the distance from the grouting layer to the roof of the coal seam; θ is the fracture angle of the overlying strata of the coal seam.

[0087] Based on the parameters in Table 1, the distance S from the cut-off eye, the roadway, and other planes is calculated to be 77m.

[0088] like Figure 4 As shown, the remaining boreholes in the first mining face 4 are arranged sequentially according to the center line 21 of the first mining face. The arrangement principle can be based on the spacing control according to the slurry diffusion radius.

[0089] Furthermore, when grouting is carried out in the lower part of the key layer of the replacement working face during the mining process, the arrangement of grouting boreholes is based on the equivalent mining width, rather than the width of the replacement working face. The borehole arrangement is based on the centerline of the equivalent mining width and is offset towards the first mining face.

[0090] Specifically, during the takeover of the working face, grouting is performed on the lower part of the key layer of the takeover working face. Figure 4 The arrangement of grouting boreholes 18 in the first replacement working face 5 should be based on the equivalent mining width 9, rather than the width of the replacement working face. The borehole arrangement should be based on the center line 22 of the equivalent mining width of the replacement working face, and offset towards the first mining face 4.

[0091] Furthermore, the remaining working faces are sequentially subjected to delamination grouting and backfilling mining. The width of the (i+1)th working face is calculated according to the following formula:

[0092] L (i+1) =L d(i+1) -1 / 2L d(i) (1-ε)-d sc(i+1)

[0093] In the formula: ε is the injection-production ratio; L (i+1) L is the equivalent eye length of the (i+1)th working face; (i) Let be the length of the cut eye on the i-th working face;

[0094] d sc(i+1) L is the width of the air intake roadway between the i-th working face and the (i+1)-th working face; (i+1) Let be the length of the cut eye on the (i+1)th working face.

[0095] The above are merely preferred embodiments of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A method for reducing settlement by grouting and filling overburden without coal pillars, characterized in that, include: Determine the positions of all key strata within the panel area, the key grouting strata in the overburden, the fracture distance of the key grouting strata, and the width of the first mining face; Based on the allowable mining width of the key grouting layer and utilizing the principle of the fulcrum effect of the compacted zone of the caving zone, the equivalent mining width is determined, the length of the successor working face is calculated, and the overburden separation and backfilling mining system is obtained; no coal pillars are left between the working faces of the overburden separation and backfilling mining system. The first mining face is mined, followed by grouting of the lower part of the key layer; When taking over a working face, grouting should be carried out in the lower part of the key layer of the working face. The remaining working faces will be mined sequentially with grouting and backfilling until the entire panel is mined out; no coal pillars will be left between any working faces. The height of the key grouting layer from the coal seam is greater than the sum of the height of the water-conducting fracture zone and the height of the safety isolation zone, and the key layer with the deepest burial depth among all key layers is selected as the key grouting layer. The formula for determining the equivalent mining width based on the allowable mining width of the key grouting layer is as follows: In the formula: ε is the injection-production ratio; L 等效 L is the equivalent cut length of the working face; 首采 d is the length of the first working face cut. sc The width of the air intake roadway between the first mining face and the successor mining face is m; L 接替 To replace the cutting length of the working face; The formula for calculating the length of the replacement working face is as follows: Wherein, the equivalent mining width value is taken as the limit mining width value allowed by the grouting key layer, d sc Dimensions for the layout of pillarless roadways in a mine; The process of obtaining an overburden delamination and backfill mining system includes: The width of the replacement working face is calculated, and the return airway is arranged according to the width of the replacement working face to obtain the first mining face mining system and "Y" type ventilation system that enable the working face to have the conditions for backfilling mining. The process of grouting the lower part of the key stratum following the initial mining face mining includes: Following the grouting of the working face, grouting work is carried out when the delamination just begins to form at the beginning of the working face mining, and the positions of the first row of grouting boreholes are arranged. During construction, the timing of the initial grouting is determined based on the amount of water loss from the borehole. The initial grouting is carried out when the amount of water loss from the borehole suddenly increases to exceed the preset threshold. The positions of the first row of grouting boreholes are arranged according to the following formula: S=H / tanθ In the formula: S is the planar distance from the cut-off point and the roadway; H is the distance from the grouting layer to the roof of the coal seam; θ is the fracture angle of the overlying strata of the coal seam; When grouting is carried out in the lower part of the key layer of the replacement working face during the mining process, the arrangement of grouting boreholes is based on the equivalent mining width. The borehole arrangement is based on the centerline of the equivalent mining width and is offset towards the first mining face.

2. The method according to claim 1, characterized in that, The roadway layout for the coal pillar-free overburden separation grouting mining method described above is a goaf-retention layout.

3. The method according to claim 1, characterized in that, The formula for calculating the failure distance of the key grouting layer is as follows: In the formula: L1 is the critical layer failure distance in m under grouting conditions; δ1 is the tensile strength of the subcritical layer in kPa; h1 is the thickness of the subcritical layer in m; q1 is the upper formation pressure borne by the critical layer when it is not grouted.

4. The method according to claim 1, characterized in that, The formula for the width of the first mining face is as follows: W k =L k +2H k / tanθ; In the formula: W k L represents the maximum allowable mining width of the working face during grouting and filling of the Kth critical layer; K H represents the critical layer fracture distance; k θ represents the distance between the key stratum and the working coal seam; θ is the fracture angle of the overlying strata of the coal seam.

Images