Coal gangue filling post-production water reducing method

Abstract

The invention provides a coal gangue filling post-production water reducing method, and relates to the technical field of green mining of coal mines. The method comprises the following steps: determining the position and row pitch of grouting holes according to the position of a coal mine goaf and the diffusion radius of coal gangue slurry; analyzing the overlying strata of the coal mine goaf, and determining the development height of the caving zone; according to the development height of the caving zone, the vertical depth between a grouting end hole and a corresponding grouting hole is calculated, and the grouting end hole is located at the top of the caving zone; drilling is conducted according to the position, the row pitch and the vertical depth of the grouting holes; and coal gangue slurry is injected into the grouting holes to fill the goaf in the coal mine, and the bleeding rate of the coal gangue slurry meets the preset requirement. By means of the mode, coal seam roof cracks can be filled and blocked, a supply channel is blocked, the water inflow of a mine is reduced, and meanwhile part of mine water can be consumed through manufacturing of coal gangue slurry. The coal gangue is subjected to underground treatment, the problem that the coal gangue is stacked on the ground to pollute the environment is solved, and green mining of a coal mine is achieved.

Description

Technical Field

[0001] The present application relates to the technical field of green coal mining, and in particular to a method for reducing water after coal gangue filling and mining. Background Art

[0002] How to organically combine comprehensive treatment of mining subsidence areas, water-saving coal mining and comprehensive utilization of coal gangue has become an important research topic for the economic development of coal mines. A scientific, effective, long-term stable and economically feasible comprehensive treatment method is urgently needed to protect the safe production of coal mines and the ecological environment protection of mining areas. Comprehensive treatment has become an inevitable requirement for the long-term development of mines.

[0003] It should be noted that the information disclosed in the above background technology section is only used to enhance the understanding of the background of the present application, and therefore may include information that does not constitute the prior art known to ordinary technicians in the field. Summary of the invention

[0004] The present application provides a method for reducing water after coal gangue filling mining, which at least to a certain extent provides a scientific, effective, long-term stable and economically feasible comprehensive coal mine management method.

[0005] Other features and advantages of the present application will become apparent from the following detailed description, or may be learned in part by the practice of the present application.

[0006] According to one aspect of the present application, a method for post-mining water reduction by gangue filling is provided, characterized in that it includes: determining the position and row spacing of grouting holes according to the position of the coal mine goaf and the diffusion radius of the gangue slurry; analyzing the overlying rock strata in the coal mine goaf to determine the development height of the collapse zone; calculating the vertical depth between the grouting end hole and the corresponding grouting hole according to the development height of the collapse zone, the grouting end hole being located at the top of the collapse zone; drilling according to the position, row spacing and vertical depth of the grouting holes; injecting gangue slurry into the grouting holes to fill the goaf in the coal mine, the water seepage rate of the gangue slurry meeting the preset requirements.

[0007] In one embodiment of the present application, it also includes: analyzing the properties of slurry made from coal gangue in coal mines, and preparing coal gangue slurry whose diffusion radius and water seepage rate meet preset requirements based on the analysis results.

[0008] In one embodiment of the present application, the analysis results include: a curve of the relationship between the measured density of the gangue slurry and the funnel viscosity, the settling time and average settling velocity of the gangue slurry under different particle size gradings, the proportion of large-particle size gangue powder in the gangue slurry that meets the preset injectability requirements, the slurry parameters when the diffusion radius of the gangue slurry in the goaf meets the preset requirements, and one or more of the water seepage of the gangue slurry of different mass concentrations prepared per kilogram of gangue; the properties of the slurry made of gangue in the coal mine are analyzed , including: setting multiple groups of coal gangue slurries under water-cement ratios, analyzing the measured density and funnel viscosity of the coal gangue slurry under each group of water-cement ratios, determining the relationship curve between the measured density and funnel viscosity of the coal gangue slurry, and the coal gangue slurries under different water-cement ratios are prepared using the same batch of coal gangue powder; and / or, configuring multiple groups of coal gangue slurries by fixing the water-cement ratio and changing the particle size distribution of the coal gangue powder, or fixing the particle size distribution of the coal gangue powder and changing the water-cement ratio, analyzing the slurry parameters of each group of coal gangue slurries, and determining the relationship curve between the measured density and funnel viscosity of the coal gangue slurry under different particle size distributions. Settling time and average settling velocity; and / or, setting multiple groups of water-cement ratios, setting two groups of coal gangue slurries under each group of water-cement ratios, the two groups of coal gangue slurries have the same proportion of small-particle-size coal gangue powder, one group of coal gangue slurries uses coal gangue powder of the first largest particle size range, and the other group of coal gangue slurries uses coal gangue powder of the second largest particle size range, the two groups of coal gangue slurries under the same water-cement ratio have the same proportion of coal gangue powder of the first largest particle size range and coal gangue powder of the second largest particle size range, and the proportion of coal gangue powder of the same particle size range is different under different water-cement ratios. The proportion of large-size coal gangue powder in the two groups of coal gangue slurries is different; the overall stability of the two groups of coal gangue slurries under each water-cement ratio is analyzed to determine the proportion range of large-size coal gangue powder in the coal gangue slurry that meets the preset injectability requirements; and / or, through numerical simulation research on the diffusion law of coal gangue slurry at different mass concentrations, determine the slurry parameters when the diffusion radius of the coal gangue slurry in the goaf meets the preset requirements; and / or, through a water seepage test, determine the water seepage amount of coal gangue slurry with different mass concentrations prepared per kilogram of coal gangue.

[0009] In one embodiment of the present application, the slurry parameters include: at least one of slurry density, viscosity, expansion, water separation rate, saturated density and saturated water content.

[0010] In one embodiment of the present application, the particle size range of the small-particle coal gangue powder is 0-0.18 mm, the first large particle size range is 0.60 mm-1.18 mm, and the second large particle size range is 1.18 mm-2.36 mm.

[0011] In one embodiment of the present application, the slurry parameters include: at least one of the grouting pipe radius, grouting pressure, slurry density and slurry initial viscosity.

[0012] In one embodiment of the present application, it also includes: determining the porosity of the collapse zone; calculating the volume of coal gangue slurry that can be injected into the collapse zone based on the porosity; calculating the required mass of coal gangue based on the volume, so as to prepare the coal gangue in advance according to the required mass of coal gangue.

[0013] In one embodiment of the present application, determining the void ratio of the collapse zone may include: calculating the void ratio of the collapse zone according to the following formula:

[0014]

[0015] Among them, K p is the expansion coefficient of the broken rock in the collapse zone; is the void ratio of the collapse zone.

[0016] In one embodiment of the present application, the calculating the volume of the coal gangue slurry that can be injected into the caved zone according to the porosity includes: calculating the volume of the coal gangue slurry that can be injected into the caved zone according to the following formula:

[0017]

[0018] Among them, b is the width of the working face in the goaf; l is the length of the working face in the goaf; b is the height of the working face in the goaf; is the porosity of the collapse zone; V is the volume of coal gangue slurry that can be injected into the collapse zone.

[0019] In one embodiment of the present application, the calculating the required mass of coal gangue according to the volume includes: calculating the required mass of coal gangue according to the following formula:

[0020] V e =V×f

[0021] m=V e ×ρ sat ×(1-ω sat )

[0022] Where V is the volume of coal gangue slurry that can be injected into the collapse zone; f is the filling coefficient; V e Effectively fill the space of the collapse zone; sat is the water content of saturated coal gangue after natural dehydration; ρ sat is the saturated density of coal gangue after natural dehydration; m is the required mass of coal gangue.

[0023] The technical solution provided by the embodiments of the present application includes at least the following beneficial effects:

[0024] The technical solution provided by the embodiment of the present application can fill and seal the cracks in the coal seam roof by drilling a hole to the top of the collapse zone to form a grouting channel and injecting coal gangue slurry into the grouting hole, blocking the supply channel and reducing the water inflow in the mine. At the same time, the production of coal gangue slurry can consume part of the mine water. The underground disposal of coal gangue solves the problem of environmental pollution caused by surface stacking of coal gangue and realizes green mining of coal mines.

[0025] Furthermore, in terms of safe mining of coal mines, after the gangue slurry is fully filled, air leakage into the goaf can be reduced, which is beneficial to fire prevention management of the working face.

[0026] Furthermore, backfill mining greatly reduces rock movement and surface subsidence and deformation, protecting the groundwater environment and surface ecological environment.

[0027] Furthermore, by grouting coal gangue in the collapsed area of ​​the goaf, filling the water-conducting fissures caused by mining, and blocking the water inrush channels of the mine, the amount of water in the mine is reduced, the pressure on mine drainage and surface water treatment is alleviated, and the cost of treating mine water and coal gangue is reduced.

[0028] It should be understood that the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] The drawings herein are incorporated into the specification and constitute a part of the specification, illustrate embodiments consistent with the present application, and together with the specification are used to explain the principles of the present application. Obviously, the drawings described below are only some embodiments of the present application, and for ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0030] Figure 1 A schematic diagram showing the zoning and zoning characteristics of the mining overburden in one embodiment of the present application;

[0031] Figure 2 A schematic diagram showing slurry diffusion in one embodiment of the present application;

[0032] Figure 3 A flow chart of a method for reducing water after coal gangue filling mining in yet another embodiment of the present application is shown. DETAILED DESCRIPTION

[0033] Example embodiments will now be described more fully with reference to the accompanying drawings. However, example embodiments can be implemented in a variety of forms and should not be construed as limited to the examples set forth herein; rather, these embodiments are provided so that this application will be more comprehensive and complete and fully convey the concepts of the example embodiments to those skilled in the art. The described features, structures, or characteristics may be combined in any suitable manner in one or more embodiments.

[0034] In addition, the accompanying drawings are only schematic illustrations of the present application and are not necessarily drawn to scale. The same reference numerals in the drawings represent the same or similar parts, and thus their repeated descriptions will be omitted. It should be noted that the concepts of "first", "second", etc. mentioned in the present application are only used to distinguish between different "large particle size ranges" and the like.

[0035] Gangue is a kind of solid waste generated during coal mining and processing. When piled on the surface, it is easy to cause spontaneous combustion, dust and other problems, causing great harm to the environment. The main way to deal with gangue is to transport it out. It costs a lot to transport gangue out every year, which brings great economic losses to coal mines. How to organically combine the comprehensive management of goaf subsidence areas, water-saving coal mining and comprehensive utilization of gangue has become an important research topic for the economic development of coal mines. Therefore, there is an urgent need for a scientific, effective, long-term, stable and economically feasible comprehensive management method to escort the safe production of coal mines and the ecological environment protection of mining areas. Comprehensive management has become an inevitable requirement for the long-term development of mines.

[0036] According to the analysis of hydrogeological conditions, there is a hydraulic connection between mine water and upper shallow groundwater. In areas with more developed fissures, the mine water inflow is large. This solution reduces the mine water inflow by filling and blocking the cracks in the coal seam roof, blocking the supply channel, and filling slurry materials can consume part of the mine water. The coal gangue produced in the coal mine is disposed of underground, which fundamentally solves the environmental pollution problem caused by the stacking of coal gangue and realizes green mining of coal mines.

[0037] When applying this scheme, it is necessary to study the coal mine so as to facilitate the subsequent application of this scheme to reduce water in the coal mine after coal gangue filling.

[0038] 1. Mining space division

[0039] After coal mining, the underground working face forms a goaf. Under the influence of stratum gravity and mining, the stratum is continuously damaged from bottom to top. The damaged space is transmitted upward in turn, and continuously develops in the stratum until it reaches the surface, causing the surface to sink. Under the action of gravity, it is compacted and stabilized. The whole process conforms to the law of conservation of space and is a dynamic process. Therefore, the changes in underground space after coal mining can be divided into dynamic space and static space, which together constitute the underground space formed by coal mining.

[0040] It should be noted that the study of dynamic and static underground space can not only explain the occurrence and development of stratum movement, but also reveal the changing laws of stratum movement and surface stability. At the same time, studying the basic laws of stratum movement is of great significance to the scientific and rational use of underground space, and is also an important theoretical support for rock control.

[0041] After coal seam mining, the overlying rock strata in the goaf lose their supporting foundation and break and collapse. Figure 1 As shown in the figure, according to the fracture and crushing characteristics of the overlying rock strata, the underground space (cracks) generally presents the following characteristics in its distribution: in the vertical direction of the goaf, three different mining influence zones are formed, from bottom to top, namely, collapse zone I, fracture zone II, and curved sinking zone III; in the horizontal direction, with the continuous advancement of the working face, three different dynamic change zones will be formed, namely, coal wall support zone A, delamination zone B, and re-compaction zone C.

[0042] 2. Filling space analysis

[0043] 2.1 Dynamic spatial analysis

[0044] After coal seam mining, two types of cracks are formed in the overlying rock strata: one is the delamination cracks, which are interlayer cracks that appear between layers as the rock strata sink; the other is the vertical fracture cracks, which are interlayer cracks formed as the rock strata sink and break.

[0045] In the non-full mining stage, the spatial structure height of the "O"-shaped circle of the overburden in the mining area generally develops linearly with the advancement of the working face, and the spatial structure height is about half of the short side span of the mined area. This development law has conditional restrictions. In fact, the spatial structure height is controlled by the width of the working face. The spatial structure height development of a working face of a certain width has a maximum value. Before the spatial structure height develops to the corresponding maximum value, it is controlled by the advancement length of the working face. The spatial structure height is about half of the advancement length of the working face. After reaching the maximum value of the short side of the goaf, the evolution of the "O"-shaped spatial structure height of the overburden in the mining area no longer develops upward with the advancement of the working face, but is controlled by the short side span of the goaf. That is, before the goaf is "squared", the spatial structure height increases with the advancement of the working face. After the goaf is "squared", the spatial structure height develops to the maximum height under the conditions of the width of the working face.

[0046] According to the dynamic space "O" ring space theory, the drilling arrangement should be away from the middle area of ​​the goaf (the middle of the working face is compacted and difficult to use).

[0047] 2.2 Static spatial analysis

[0048] Longwall mining is a high-intensity coal mining method with serious mining damage. After the coal seam is mined, a goaf is formed, which destroys the original stress state of the surrounding rock. When the stress exceeds its strength limit, the rock layer will deform, crack and even fall out. Under the longwall mining conditions where the roof is managed by the full caving method, according to the fracture and crushing characteristics of the overlying rock (including the coal seam itself), the most common form of movement and deformation of the overlying rock mass on the coal seam is the formation of three different mining influence zones: caving zone, fracture zone, and curved sinking zone.

[0049] Analyze from the time relationship of rock strata movement. From a large number of rock movement observations, it is known that the damage zone caused by underground coal mining first forms a collapse zone, followed by a fracture zone, and finally an overall sinking, resulting in surface movement and deformation. There is a gradual process from underground coal mining to surface movement. Although the direct roof can fall quickly after coal seam mining, the old roof does not fall immediately. It takes a time for the old roof to fall and compact the goaf space. Therefore, before the old roof comes to press, the direct roof that falls is not compacted by the overlying rock strata. Therefore, the goaf at this time has favorable conditions such as large goaf space and good connectivity of collapse zones and fracture zones, which can ensure a high filling rate and can smoothly inject a large amount of filling slurry.

[0050] According to static space analysis, the space of loosely accumulated broken rocks below the collapse zone is the main target of grouting.

[0051] 3. The filling amount of coal gangue

[0052] 3.1 Void ratio of collapsed zone

[0053] The porosity of the broken rock mass in the collapse zone can be expressed by the ratio of the pore volume between the rock blocks in the broken state to the total volume, while its crushing expansion coefficient is the ratio of the volume of the rock mass after crushing to the volume before crushing. According to the definitions of the porosity of the broken rock mass and the crushing expansion coefficient, there is a relationship between the two as shown in the following formula 1.

[0054]

[0055] Among them, K p is the expansion coefficient of the broken rock in the collapse zone; is the void ratio of the collapse zone.

[0056] After the roof collapses, the broken rocks form a disorderly piled bulk in the goaf. According to the difference in rock mechanical properties, the size and arrangement of the broken rock blocks are different, and their crushing expansion coefficients are also different, generally 1.10-1.40. Under normal circumstances, the hard rock layer is broken into large pieces and arranged neatly, and its crushing expansion coefficient is small, generally 1.10-1.20; the soft rock layer is small in size and arranged randomly after being broken, and its crushing expansion coefficient is large, generally 1.30-1.40; after the medium-hard rock layer is broken, the crushing expansion coefficient is between the hard rock layer and the soft rock layer, generally 1.20-1.30.

[0057] 3.2 Slurry can be injected into the collapse zone

[0058] The volume of coal gangue slurry that can be injected into the collapse zone is calculated according to the following formula 2:

[0059]

[0060] Among them, b is the width of the working face in the goaf; l is the length of the working face in the goaf; b is the height of the working face in the goaf; is the porosity of the collapse zone; V is the volume of coal gangue slurry that can be injected into the collapse zone.

[0061] 3.3 Required quality of gangue

[0062] Calculate the required mass of coal gangue according to the following formula 3 and formula 4:

[0063] V e =V×f (3)

[0064] m=V e ×ρ sat ×(1-ω sat ) (4)

[0065] Where V is the volume of coal gangue slurry that can be injected into the collapse zone; f is the filling coefficient (dimensionless); V e Effectively fill the space of the collapse zone; sat is the water content of saturated coal gangue after natural dehydration (dimensionless); ρ sat is the saturated density of coal gangue after natural dehydration; m is the required mass of coal gangue.

[0066] Based on the above analysis of the filling amount of coal gangue, the porosity of the collapse zone can be determined; based on the porosity, the volume of coal gangue slurry that can be injected into the collapse zone can be calculated; based on the volume, the required mass of coal gangue can be calculated so that the coal gangue can be prepared in advance according to the required mass of coal gangue.

[0067] Among them, the porosity of the collapse zone can be determined according to the above formula 1.

[0068] The volume of coal gangue slurry that can be injected into the collapse zone is calculated according to the above formula 2.

[0069] The required mass of coal gangue is calculated according to the above formula 3 and formula 4.

[0070] 4. Analyze the properties of slurry made from coal gangue

[0071] 4.1 Study the critical value of water-cement ratio when making slurry of coal gangue with different particle sizes, test the slurry density and viscosity, and select the appropriate water-cement ratio, so as to select the optimal particle size and economic slurry ratio according to construction practice.

[0072] 4.2 Use coal gangue that meets the particle size requirements to make coal gangue slurries with different water-cement ratios, measure the measured density and funnel viscosity (which may also include: particle density, apparent viscosity) of the fine-grained gangue powder slurry at different water-cement ratios, and obtain the relationship curve between the measured density and the funnel viscosity.

[0073] The embodiments of the present application do not limit the specific particle size of the coal gangue that meets the particle size requirements. For example, the coal gangue that meets the particle size requirements may include coal gangue powder whose particle size can pass through an 80-mesh sieve.

[0074] The embodiments of the present application do not limit which water-cement ratios are specifically included in the different water-cement ratios. For example, the different water-cement ratios may include: 1.0, 1.2, 1.4, 1.5, 1.6, a total of 5 water-cement ratios.

[0075] In one embodiment, the coal gangue slurries at different water-cement ratios are prepared using the same batch of coal gangue powder.

[0076] 4.3 By fixing the water-cement ratio and changing the particle size distribution of the gangue powder, or fixing the particle size distribution of the gangue powder and changing the water-cement ratio, multiple groups of gangue slurries were prepared. The slurry parameters of each group of gangue slurry were analyzed, the settling time and average settling velocity of the gangue slurry under different particle size distributions were determined, and the injectability was analyzed.

[0077] In one embodiment, the slurry parameters include at least one of slurry density, viscosity, expansion, water separation rate, saturated density and saturated water content.

[0078] 4.4 Set multiple groups of water-cement ratios, and set two groups of coal gangue slurries under each group of water-cement ratios. The proportion of small-particle-size coal gangue powder in the two groups of coal gangue slurries is the same. Coal gangue powder in the first largest particle size range is used in one group of coal gangue slurry, and coal gangue powder in the second largest particle size range is used in the other group of coal gangue slurry. The proportion of coal gangue powder in the first largest particle size range and the coal gangue powder in the second largest particle size range in the two groups of coal gangue slurries under the same water-cement ratio are the same, and the proportion of coal gangue powder in the large particle size range in the two groups of coal gangue slurries using coal gangue powder in the same particle size range under different water-cement ratios is different; analyze the overall stability of the two groups of coal gangue slurries under each group of water-cement ratios, and determine the proportion range of large-particle-size coal gangue powder in the coal gangue slurry that meets the preset injectability requirements.

[0079] The embodiments of the present application do not limit what particle size range is a small particle size and what particle size range belongs to the first largest particle size range or the second largest particle size range.

[0080] For example, the particle size range of small-particle coal gangue powder is 0 to 0.18 mm (millimeter), the first largest particle size range is 0.60 mm to 1.18 mm, and the second largest particle size range is 1.18 mm to 2.36 mm.

[0081] The preset injectability requirements can be determined based on the specific coal mine, and this application does not impose any restrictions on this.

[0082] 4.5 Through numerical simulation research on the diffusion law of coal gangue slurry under different mass concentrations, the slurry parameters are determined when the diffusion radius of coal gangue slurry in the goaf meets the preset requirements.

[0083] In one embodiment, the slurry parameters may include at least one of: grouting pipe radius, grouting pressure, slurry density and slurry initial viscosity.

[0084] It should be noted that the specific diffusion radius that meets the preset requirements needs to be determined according to the specific conditions of the goaf in the coal mine, and this application does not limit this. For example, in a coal mine, based on a specific analysis of the goaf, the diffusion radius of the gangue slurry required is 75m (meters).

[0085] 4.6 Conduct a static water separation test on the gangue slurry to determine the saturated density and saturated water content of the gangue slurry under natural sedimentation conditions (24 hours).

[0086] 4.7 The water seepage test is used to determine the water seepage amount of the coal gangue slurry with different mass concentrations prepared per kilogram of coal gangue.

[0087] 5. Similar simulation

[0088] According to the research results on the properties of slurry made from coal gangue, injectable coal gangue slurry was made, and a grouting flow consolidation performance test system suitable for on-site goaf was designed to study the actual diffusion radius, diffusion effect and water separation of gangue powder slurry.

[0089] According to the above analysis results of the properties of the slurry made from coal gangue, a coal gangue slurry is prepared whose diffusion radius and water seepage rate meet the preset requirements.

[0090] After completing the research on coal gangue slurry, it is necessary to analyze how to drill holes to facilitate the injection of coal gangue slurry.

[0091] 6. Theoretical analysis of drilling parameters

[0092] Grouting is carried out in the collapsed zone of the goaf to ensure that the grouting borehole can effectively enter the collapsed zone, that is, to ensure that the final grouting hole is located in the collapsed zone. The height of the collapsed zone of the overburden in the fully-mechanized coal mining should be determined. The height of the collapsed zone in the fully-mechanized coal mining is measured by the rock stratum expansion method, the empirical formula method, the key layer theory and the actual situation on site.

[0093] In order to ensure that the water-conducting channels of mining fractures are effectively blocked by grouting, it is necessary to determine the height of the water-conducting fracture zone in fully-mechanized coal mining. According to the slurry self-flow diffusion radius determined by the study of the diffusion characteristics of the grouting slurry in the goaf, the goaf utilization rate and the slurry accumulation and superposition effect are analyzed to enable the slurry filled in the grouting boreholes to be effectively superimposed, and finally set a reasonable grouting borehole spacing.

[0094] 6.1 Calculate and determine the height of the collapse zone.

[0095] 6.2 Calculate and determine the development height of the water-conducting fracture zone.

[0096] 6.3 Diffusion mechanism of grouting slurry in goaf

[0097] The diffusion distance of slurry in the collapse zone is related to the initial velocity, slurry concentration, particle size, and medium pore characteristics. Figure 2 As shown, the slurry flow velocity in zone I gradually decreases after leaving the orifice, but is greater than the critical velocity, and the particles do not deposit; the slurry flow velocity in zone II decreases to below the critical velocity, forming a stable deposition; there is no cement deposition in zone III, and it is all filtered water flow.

[0098] According to the diffusion mechanism of grouting slurry in goaf and the location of goaf, the diffusion radius of gangue slurry is designed. The location and spacing of grouting holes are further designed according to the diffusion radius of gangue slurry and the location of goaf.

[0099] 6.4 Drilling Plane Layout

[0100] According to the rock movement theory, the porosity on both sides of the collapse zone of the working face is greater than that in the middle. Therefore, two rows of grouting holes need to be arranged close to the upper and lower drifts (avoiding the middle area). According to theoretical research, the diffusion radius of the slurry is R. In order to effectively fill the goaf, the two rows are located at a distance of no more than R from the coal pillars on both sides.

[0101] 6.5 The final grouting hole is located at the upper part of the collapse zone.

[0102] 6.6 Drilling structure

[0103] For each borehole, the drilling process can be divided into three steps: the first opening, construction to the bottom of the Quaternary system, the oil casing is lowered, and the wall is protected to prevent the hole from collapsing; the second opening, construction to the top of the water-conducting fracture zone, the oil casing is lowered to seal and stop water; the third opening, the bare hole is constructed to the end hole.

[0104] 6.7 Drilling Construction Technology

[0105] At the first opening, a drill bit is used to drill to the bottom of the Quaternary system, and the surface casing of the oil casing is lowered. Ordinary silicate cement is used for cementing. The cement slurry is returned to the wellhead and left to solidify for several hours.

[0106] The second drilling uses a drill bit to drill to the top of the water-conducting fracture zone, and the oil casing is lowered to seal and stop water. Ordinary silicate cement is used for cementing, and the cement slurry is returned to the wellhead; wait for several hours for solidification.

[0107] The third opening uses a drill bit to drill to the final hole, a bare hole.

[0108] The embodiments of the present application do not limit the drill bit specifications used for each opening, and they can be determined according to actual construction requirements.

[0109] By drilling through three openings, the drilling of grouting holes can be achieved more safely and efficiently, and the hole tilting can be effectively prevented.

[0110] 6.8 Cementing

[0111] Before lowering the oil casing, use a long pipe of about 20-30m with the same diameter to conduct exploration operations to ensure that the wellbore is unobstructed. For the reduced diameter section and the blocked section, the hole must be carefully reamed, and the reaming speed must be controlled at 15 minutes per single pipe. The diameter is circulated to ensure that the sand at the bottom of the well is clean, and the slurry is replaced.

[0112] Materials: Prepared with ordinary Portland cement (e.g., P.O42.5 ordinary Portland cement), the mortar specific gravity is 1.70-1.80 g / cm 3 The pH value of clean water should be greater than 5, and the cement slurry of the check valve can be swept away after the cement solidifies for 72 hours.

[0113] Cementing process: lower the drill pipe to align the positive and negative joints of the upper water stop; pump in a certain amount of clean water as the pre-fluid; pump in cement slurry; pump in clean water for slurry replacement; reverse the drill pipe and wait for solidification for 72 hours; sweep away the water stop.

[0114] Sealing water-stopping quality inspection: adopt the water level pressure difference method. After 72 hours of cement sealing water-stopping, sweep away the cement plug in the casing, and then fill the casing with clean water, and observe continuously for 4 hours. If the water column liquid level drops no more than 2cm per hour, it is qualified; otherwise, it is unqualified and needs to be re-sealed.

[0115] 6.9 Grouting Design

[0116] The slurry type and proportion are determined according to engineering tests and numerical simulations, and the gangue slurry is transported to the collapse zone through a pump pipe. Flow and pressure monitoring are set on each orifice pipeline. Single-hole grouting end standard: The grouting end pressure is determined according to the actual situation on site and the material property test. For example, if the NBB-390 / 15 grouting pump is used for grouting, and the grouting project volume is 3000t (tons), then the single-hole grouting end standard is: the grouting end pressure reaches 1-1.5Mpa (megapascals), the grouting volume per unit time is less than 50L / min and the duration exceeds 15min, and the overall grouting volume reaches 3000t. Any of the above conditions can be used as the standard for ending grouting.

[0117] 6.10 Sealing

[0118] Grouting and sealing: After the grouting is completed, the entire borehole needs to be sealed. Before sealing, the hole is swept to the bottom of the main hole section, and pure cement slurry is used for drilling and upward grouting and sealing. The specific gravity of P.O42.5 ordinary silicate cement slurry is not less than 1.65 tons / m 3 After the cement slurry in the sealing section solidifies, the vertical distance between the solidification surface and the drill hole mouth shall not be greater than 5m, otherwise the hole must be sealed again.

[0119] like Figure 3 As shown, in one embodiment of the present application, the method for reducing water after coal gangue filling mining may include S301 to S305.

[0120] S301, determining the location and spacing of grouting holes according to the location of the coal mine goaf and the diffusion radius of the coal gangue slurry.

[0121] S302, analyze the overlying rock strata in the coal mine goaf to determine the development height of the collapse zone.

[0122] S303, according to the development height of the collapse zone, the vertical depth between the grouting end hole and the corresponding grouting hole is calculated, and the grouting end hole is located at the top of the collapse zone.

[0123] S304, drilling is performed according to the position, row spacing and vertical depth of the grouting holes.

[0124] S305, injecting gangue slurry into the grouting hole to fill the goaf in the coal mine, and the water seepage rate of the gangue slurry meets the preset requirements.

[0125] For the specific implementation of S301-S305, please refer to the above analysis and research on coal mines, which will not be repeated here.

[0126] It should be noted that the execution order of S301-S305 can be arbitrary and can be adjusted according to the actual situation of the coal mine.

[0127] Directional drilling is performed on the ground in the goaf, grouting is performed within the collapse zone, the voids in the goaf are filled, the cracks in the roof of the goaf are blocked, and the water conduit from the upper aquifer into the goaf is blocked, thus reducing the drainage volume in the goaf. At the same time, the use of mine water and coal gangue for slurry consumption can reduce the cost of water treatment and solid waste treatment. Filling the goaf can also reduce ground subsidence, achieving multiple purposes such as water reduction, subsidence reduction, waste removal, and pollution control.

[0128] In terms of safe mining of coal mines, after full filling, air leakage into the goaf is reduced, which is beneficial to fire prevention management of the working face. Through filling mining, rock stratum movement and surface settlement deformation are greatly reduced, protecting the groundwater environment and surface ecological environment.

[0129] While implementing the comprehensive management of coal gangue grouting and filling in the goaf subsidence area, we have achieved the goal of "taking and giving back to the original place" of coal gangue, scientifically and rationally solving the problem of solid waste treatment in mines; and realizing water-saving coal mining. Through the grouting and filling of coal gangue in the goaf subsidence area, the mining-driven water-conducting fissures are filled, the mine water inflow channel is blocked, the mine water inflow is reduced, and the pressure on mine drainage and surface water treatment is alleviated.

[0130] The technical solution provided by the embodiment of the present application can fill and seal the cracks in the coal seam roof by drilling a hole to the top of the collapse zone to form a grouting channel and injecting coal gangue slurry into the grouting hole, blocking the supply channel and reducing the water inflow in the mine. At the same time, the production of coal gangue slurry can consume part of the mine water. The underground disposal of coal gangue solves the problem of environmental pollution caused by surface stacking of coal gangue and realizes green mining of coal mines.

[0131] Furthermore, in terms of safe mining of coal mines, after the gangue slurry is fully filled, air leakage into the goaf can be reduced, which is beneficial to fire prevention management of the working face.

[0132] Furthermore, backfill mining greatly reduces rock movement and surface subsidence and deformation, protecting the groundwater environment and surface ecological environment.

[0133] Furthermore, by grouting coal gangue in the collapsed area of ​​the goaf, filling the water-conducting fissures caused by mining, and blocking the water inrush channels of the mine, the amount of water in the mine is reduced, the pressure on mine drainage and surface water treatment is alleviated, and the cost of treating mine water and coal gangue is reduced.

[0134] Those skilled in the art will readily appreciate other embodiments of the present application after considering the specification and practicing the invention disclosed herein. The present application is intended to cover any modification, use or adaptation of the present application, which follows the general principles of the present application and includes common knowledge or customary techniques in the art that are not disclosed in the present application. The specification and examples are intended to be exemplary only, and the true scope of the present application is indicated by the appended claims.

Claims

1. A method for reducing water after coal gangue filling mining, characterized in that: include: Determine the location and spacing of grouting holes according to the location of coal mine goaf and the diffusion radius of coal gangue slurry; Analyze the overlying rock strata in the coal mine goaf to determine the height of the collapse zone; According to the development height of the collapse zone, the vertical depth between the grouting end hole and the corresponding grouting hole is calculated, and the grouting end hole is located at the top of the collapse zone; Drilling is performed according to the position, row spacing and vertical depth of the grouting holes; Gangue slurry is injected into the grouting hole to fill the goaf in the coal mine, and the water seepage rate of the gangue slurry meets the preset requirements.

2. The method according to claim 1, characterized in that Also includes: The properties of slurry made from coal gangue in coal mines are analyzed, and based on the analysis results, coal gangue slurry with diffusion radius and water seepage rate meeting the preset requirements is prepared.

3. The method according to claim 2, characterized in that The analysis results include: a curve of the relationship between the measured density of the gangue slurry and the funnel viscosity, the settling time and average settling velocity of the gangue slurry under different particle size gradations, the proportion range of large-size gangue powder in the gangue slurry that meets the preset injectability requirements, the slurry parameters when the diffusion radius of the gangue slurry in the goaf meets the preset requirements, and one or more of the water seepage of the gangue slurry of different mass concentrations prepared per kilogram of gangue; The analysis of the properties of the slurry made from coal gangue in the coal mine includes: The gangue slurries under multiple water-cement ratios are set, the measured density and funnel viscosity of the gangue slurries under each water-cement ratio are analyzed, and the relationship curve between the measured density and funnel viscosity of the gangue slurries is determined. The gangue slurries under different water-cement ratios are prepared using the same batch of gangue powder. And / or, multiple groups of gangue slurries are prepared by fixing the water-cement ratio and changing the particle size distribution of the gangue powder, or fixing the particle size distribution of the gangue powder and changing the water-cement ratio, and the slurry parameters of each group of gangue slurries are analyzed to determine the settling time and average settling velocity of the gangue slurries under different particle size distributions; And / or, multiple groups of water-cement ratios are set, and two groups of coal gangue slurries are set under each group of water-cement ratios, the proportion of small-size coal gangue powder in the two groups of coal gangue slurries is the same, one group of coal gangue slurry uses coal gangue powder in the first largest particle size range, and the other group of coal gangue slurry uses coal gangue powder in the second largest particle size range, the proportion of coal gangue powder in the first largest particle size range and the proportion of coal gangue powder in the second largest particle size range in the two groups of coal gangue slurries under the same water-cement ratio are the same, and the proportion of coal gangue powder in the large particle size range in the two groups of coal gangue slurries using coal gangue powder in the same particle size range under different water-cement ratios is different; analyze the overall stability of the two groups of coal gangue slurries under each group of water-cement ratios, and determine the proportion range of large-size coal gangue powder in the coal gangue slurry that meets the preset injectability requirements; And / or, by numerically simulating the diffusion law of gangue slurry at different mass concentrations, determine the slurry parameters when the diffusion radius of the gangue slurry in the goaf meets the preset requirements; And / or, the water seepage amount of the coal gangue slurry with different mass concentrations prepared per kilogram of coal gangue is measured through a water seepage test.

4. The method according to claim 3, characterized in that The slurry parameters include: at least one of slurry density, viscosity, expansion, water separation rate, saturated density and saturated water content.

5. The method according to claim 3, characterized in that: The particle size range of the small-particle coal gangue powder is 0-0.18 mm, the first largest particle size range is 0.60 mm-1.18 mm, and the second largest particle size range is 1.18 mm-2.36 mm.

6. The method according to claim 3, characterized in that: The slurry parameters include: at least one of the grouting pipe radius, grouting pressure, slurry density and slurry initial viscosity.

7. The method according to claim 1, characterized in that Also includes: Determine the void ratio of the collapse zone; According to the porosity, the volume of coal gangue slurry that can be injected into the collapse zone is calculated; According to the volume, the mass of the required coal gangue is calculated so that the coal gangue can be prepared in advance according to the mass of the required coal gangue.

8. The method according to claim 7, characterized in that Determining the void ratio of the collapse zone may include: The void ratio of the collapse zone is calculated according to the following formula: Among them, K p is the expansion coefficient of the broken rock in the collapse zone; is the void ratio of the collapse zone.

9. The method according to claim 7, characterized in that: The method of calculating the volume of coal gangue slurry that can be injected into the collapse zone according to the porosity comprises: The volume of coal gangue slurry that can be injected into the collapse zone is calculated according to the following formula: Among them, b is the width of the working face in the goaf; l is the length of the working face in the goaf; b is the height of the working face in the goaf; is the porosity of the collapse zone; V is the volume of coal gangue slurry that can be injected into the collapse zone.

10. The method according to claim 7, characterized in that The step of calculating the required mass of coal gangue according to the volume comprises: The required mass of coal gangue is calculated according to the following formula: In e =V×f m=V e ×ρ sat ×(1-ω sat ) Where V is the volume of coal gangue slurry that can be injected into the collapse zone; f is the filling coefficient; V e Effectively fill the space of the collapse zone; sat is the water content of saturated coal gangue after natural dehydration; ρ sat is the saturated density of coal gangue after natural dehydration; m is the required mass of coal gangue.

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