阅读说明：本技术 矿化利用co2废气生态保护性采煤方法 (Mineralizing and utilizing CO2Waste gas ecological protective coal mining method ) 是由 马立强 吴乙辉 许玉军 翟江涛 王洋洋 于 2021-09-06 设计创作，主要内容包括：本发明公开了一种矿化利用CO-(2)废气生态保护性采煤方法,适用于煤矿井下。确定采场采动覆岩渗流隔离带稳定所需的充填开采临界关键参数,随着工作面的推进,在采出空间两端构筑密闭墙使开采完毕的区域封闭,之后向封闭区域浇筑CO-(2)矿化充填材料CFBF对采空区进行随采随充,并保证充填CFBF凝固后对采空区的支撑；CFBF利用矿区矸石、粉煤灰和矿井污水,辅以水泥和碱性硅基添加剂制备,既确保采动覆岩渗流隔离带形成,又可进行连续CFBF充填,最终实现CO-(2)与煤炭的置换。操作简单、结果可靠,可在实现CO-(2)矿化和固废材料处理的前提下大幅度提高煤炭资源的采出率。(The invention discloses a method for mineralizing and utilizing CO 2 The waste gas ecological protective coal mining method is suitable for underground coal mine. Determining filling mining critical key parameters required by stability of mining overburden seepage isolation zones of a stope, and mining along with the advance of a working faceConstructing sealing walls at two ends of the output space to seal the mined area, and then pouring CO into the sealed area 2 The mineralized filling material CFBF carries out mining and filling along with the goaf, and supports for the goaf after the CFBF is solidified are guaranteed; the CFBF is prepared by using gangue, coal ash and mine sewage in a mining area and assisting cement and an alkaline silicon-based additive, thereby not only ensuring the formation of a mining overburden seepage isolation zone, but also being capable of carrying out continuous CFBF filling, and finally realizing CO 2 Replacement with coal. Simple operation, reliable result and capability of realizing CO 2 Greatly improves the extraction rate of coal resources on the premise of mineralization and solid waste material treatment.)

1. Mineralizing and utilizing CO₂The waste gas ecological protective coal mining method is characterized in that:

along with the advance of the working face, sealing walls are built at two ends of the mining space to seal the mined area, and then CO is poured into the sealed area₂The mineralized filling material CFBF carries out mining and filling along with the goaf, and critical key parameters of strength of a filling body required by stability of a mining overburden seepage isolation zone of a CFBF filling stope are ensured in the filling process, so that the goaf is supported after the CFBF filling is solidified;

the CO is₂The mineralized filling material CFBF is prepared from fly ash 36-48%, coal gangue 12-24%, cement 5-10%, alkaline silicon-based additive 3-5% and mine water 13-44%The mass percentage of the components is configured; the method comprises the steps of obtaining fly ash and coal gangue generated in the mining process in situ during blending, crushing the coal gangue to obtain gangue powder, mixing and stirring the gangue powder, the fly ash and cement with the particle size of less than 5mm uniformly to obtain a solid mixture, preparing an aqueous solution of an alkaline silicon-based additive by using the alkaline silicon-based additive and water, feeding the aqueous solution into the solid mixture, and introducing CO recovered from industrial waste gas while stirring₂Per cubic meter of CO in the mixture of aqueous solution and solid₂The input amount is 5000L/h-50000L/h, the air input time is within 60 minutes, thereby obtaining CO₂Mineralized filling material CFBF;

and continuously mining and filling by using CFBF in the working face until all mining and filling of the working face are finished.

2. The mineralization of CO of claim 1₂The waste gas ecological protective coal mining method is characterized in that: according to the mining overburden rock permeability ratio, dividing the overburden rock into a seepage surge zone, a seepage micro-surge zone and a seepage isolation zone:

k＝αexp[β(σ₁-σ₃)]

wherein k is the permeability of the mining overburden rock, alpha and beta are coefficients, and sigma is₁-σ₃Is overburden rock bias stress.

3. The mineralization of CO of claim 1₂The method for mining the coal with the ecological protection of the waste gas is characterized in that the method for obtaining the critical value of the key parameters of the filling mining of the CFBF gob which ensures the stability of the seepage isolation zone comprises the following steps: determining the influence rule of mining overburden rock unloading and filling body creep on the overburden permeability, determining that the instantaneous deformation of a CFBF filling body does not cause sudden change instability, and determining the key mining parameters of CFBF goaf filling mining, wherein the long-term creep variable of the CFBF filling body is less than the maximum creep constraint quantity for ensuring the stability of a seepage isolation zone, wherein the key mining parameters comprise the CFBF filling rate and the CFBF filling body strength, and can be effectively supported, and the CFBF maximum lag filling distance N:

wherein N is the maximum hysteresis filling distance of CFBF, sigma_pRepresenting the strength of the coal pillar, F is the coefficient of Pythium, F represents the safety coefficient, 1.5-2 is taken,the internal friction angle of the overlying strata is shown, h is the mining height, and b is the mining space width.

4. The mineralization of CO of claim 1₂The waste gas ecological protective coal mining method is characterized in that: filling a goaf by using CFBF in a working face, simultaneously respectively defining development heights of large mining overburden rock cracks and micro cracks near the working face, drilling a hole above a mining space, enabling the drilled hole to penetrate through a seepage surge zone and a seepage surge zone, and injecting CFBF to a crack area existing in the seepage surge zone by using the drilled hole to seal the large mining overburden rock cracks; and then grouting and sealing the micro cracks existing in the crack area existing in the seepage micro-increase zone by using the drill hole, so as to prevent the cracks from further developing in the mining process.

5. The mineralization of CO as claimed in claim 4₂The waste gas ecological protective coal mining method is characterized in that: the slurry injected into the microcracked region is CO₂Mineralized nano silica gel grouting material CNS is prepared by mixing nano particles and base liquid according to the mass ratio of 1: 1000-100: 1000 and introducing CO₂Production of gas of which CO₂The feeding amount is 10-100L/min, and the base liquid is formed by mixing a silicon-based material and water according to the mass ratio of 1: 100-50: 100.

6. The mineralization of CO of claim 1₂The waste gas ecological protective coal mining method is characterized in that:

in order to identify the large cracks and micro cracks of the CFBF filling stope, firstly, an elastic foundation superposed beam and a transverse isotropic plane body mechanical model is established:

wherein, tau_m-maxThe maximum shear stress of the rock stratum; e_mThe elastic modulus of the mth rock stratum; h is_mIs the thickness of the mth layer rock stratum; h is_m-nThe thickness of the rock stratum between the nth rock stratum and the mth rock stratum is shown; q_m-nThe equivalent shear force of the composite beam is kN; a is_iAccumulating the development length of the fracture;

obtaining the maximum shear stress of the rock stratum according to the deflection of each rock stratum solved by the elastic foundation superposed beam force model, judging whether the rock stratum is broken according to a third strength theory, and calculating the shear stress distribution tau on the cross section of the mth rock stratum by using an elastoplasticity mechanical formula_mWhen τ is_m-max≥[τ_m]And when the fracture is large, accumulating the thicknesses of the fractured rock stratums to obtain the development height of the large fracture.

Wherein H_bfLarge fissure development height, h_iThe thickness of the ith layer of rock stratum is shown;

if τ_m-max<[τ_m]And if the m-th rock layer is not broken, calculating to obtain the maximum main stress distribution of different points in the rock layer, checking whether each point is broken point by point, connecting broken points to obtain the micro-fracture development condition, and accumulating the vertical lengths of the micro-fractures to obtain the thickness and the layer position of the micro-fracture area. The rock above the microcracked region is the intact rock. The condition of the stratum fracture zone can provide a basis for selecting a large fracture and micro fracture filling material of a CFBF filling stope.

7. The mineralization of CO as claimed in claim 4₂The waste gas ecological protective coal mining method is characterized in that the overlying strata fracture grouting method specifically comprises the following steps: for a large crack, directly performing grouting sealing by using a CFBF material after drilling; aiming at the micro cracks above the large cracks,after drilling, the nano particles and CO are adopted₂In situ generation of CO₂The base nanometer silica gel grouting material seals the mining overburden rock microcracks, solves the technical problem that the conventional large-particle-size aggregate grout cannot penetrate into the rock stratum microcracks, and simultaneously reduces the degree of secondary development of the microcracks induced by high pump pressure required by high-viscosity large-particle-size aggregate grout for plugging the cracks.

Technical Field

The invention relates to a coal mining method, in particular to a method for mineralizing and utilizing CO used in a coal mine₂An ecological waste gas protective coal mining method.

Background

In the primary energy consumption of China, the proportion of coal consumption is always over 60 percent, and the high-speed development of the economic society of China is powerfully promoted. The status of coal as the main body of primary energy in China will not change for a long time in the future. However, the mass exploitation of coal changes the stress environment of surrounding rocks of a stope, so that overlying strata are deformed and damaged, the overlying rocks are bent, deformed and collapsed, and then the ground surface is sunk, thereby not only harming the mining activity, but also causing ecological problems of superficial water resource loss, vegetation withering, land desertification and the like. Meanwhile, the consumption of coal resources can discharge a large amount of carbon dioxide, and according to incomplete statistics, CO generated by coal use₂The emission of CO occupies China₂The emission accounts for 72 percent of the global CO₂The emission amount is 28%, thereby causing the greenhouse effect to be intensified.

The filling mining is the most effective ecological protective mining technology for controlling the migration of overlying strata and mining subsidence at present, adopts the filling mining to prevent and control the coal mining subsidence and construct an ecological mine, and covers a plurality of fields of mining area ecological environment treatment, mining area waste solid treatment, mine water utilization and the like. According to the development of filling materials, filling mining mainly goes through three stages of dry filling, water sand filling and cemented filling, and the main filling materials comprise gangue, full tailings, half tailings, paste materials, paste-like materials, high-water materials, ultrahigh-water materials and the like. However, at present, CO can not be realized₂Mineralization of underground water and effective bearingCarrying the pressure of the overburden rock and controlling the filling material of the surface subsidence.

Disclosure of Invention

Aiming at the defects of the prior art, the method provides the mineralizing and utilizing CO with simple steps and convenient use₂An ecological waste gas protective coal mining method.

To achieve the above technical object, the mineralization of the present invention utilizes CO₂An ecological protective coal mining method for waste gas includes building sealed walls 17 at two ends of a mining space to seal the mined area, and pouring CO into the sealed area₂The mineralized filling material CFBF carries out mining and filling along with the goaf, and critical key parameters of strength of a filling body required by stability of a mining overburden seepage isolation zone of a CFBF filling stope are ensured in the filling process, so that the goaf is supported after the CFBF filling is solidified;

the CO is₂The mineralized filling material CFBF is prepared according to the mass percentage of 36-48 percent of fly ash, 12-24 percent of coal gangue, 5-10 percent of cement, 3-5 percent of alkaline silicon-based additive and 13-44 percent of mine water; the method comprises the steps of obtaining fly ash and coal gangue generated in the mining process in situ during blending, crushing the coal gangue to obtain gangue powder, mixing and stirring the gangue powder, the fly ash and cement with the particle size of less than 5mm uniformly to obtain a solid mixture, preparing an aqueous solution of an alkaline silicon-based additive by using the alkaline silicon-based additive and water, feeding the aqueous solution into the solid mixture, and introducing CO recovered from industrial waste gas while stirring₂Per cubic meter of CO in the mixture of aqueous solution and solid₂The input amount is 5000L/h-50000L/h, the air input time is within 60 minutes, thereby obtaining CO₂Mineralized filling material CFBF;

and continuously mining and continuously filling by using CFBF in the working face until all the blocks are mined and filled.

According to the mining overburden rock permeability ratio, dividing the overburden rock into a seepage surge zone, a seepage micro-surge zone and a seepage isolation zone:

k＝αexp[β(σ₁-σ₃)]

wherein k is the permeability of the mining overburden rock, alpha and beta are coefficients, and sigma is₁-σ₃Is rock of overburdenBias stress.

The method for obtaining the critical value of the CFBF goaf filling mining key parameter for ensuring the stability of the seepage isolation zone comprises the following steps of determining the influence rule of mining overburden unloading and filling body creep on the overburden permeability, determining that the CFBF filling body instantaneous deformation does not cause sudden change instability, and determining the key mining parameter of the CFBF goaf filling mining, wherein the CFBF filling body long-term creep variable is smaller than the maximum creep constraint quantity for ensuring the stability of the seepage isolation zone, and the key mining parameter comprises the CFBF filling rate, the CFBF filling body strength and the CFBF maximum lag filling distance N:

wherein N is the maximum hysteresis filling distance of CFBF, sigma_pRepresenting the strength of the coal pillar, F is the coefficient of Pythium, F represents the safety coefficient, 1.5-2 is taken,the internal friction angle of the overlying strata is shown, h is the mining height, and b is the mining space width.

Filling a goaf by using CFBF in a working face, simultaneously respectively defining development heights of large mining overburden rock cracks and micro cracks near the working face, drilling a hole above a mining space, enabling the drilled hole to penetrate through a seepage surge zone and a seepage surge zone, and injecting CFBF to a crack area existing in the seepage surge zone by using the drilled hole to seal the large mining overburden rock cracks; and then grouting and sealing the micro cracks existing in the crack area existing in the seepage micro-increase zone by using the drill hole, so as to prevent the cracks from further developing in the mining process.

The slurry injected into the microcracked region is CO₂The mineralized nano silica gel grouting material is prepared by mixing nano particles and base liquid according to a mass ratio of 1: 1000-100: 1000 and introducing CO₂Production of gas of which CO₂The feeding amount is 10-100L/min, and the base liquid is formed by mixing a silicon-based material and water according to the mass ratio of 1: 100-50: 100.

In order to identify the large cracks and micro cracks of the CFBF filling stope, firstly, an elastic foundation superposed beam and a transverse isotropic plane body mechanical model is established:

wherein, tau_m-maxThe maximum shear stress of the rock stratum; e_mThe elastic modulus of the mth rock stratum; h is_mIs the thickness of the mth layer rock stratum; h is_m-nThe thickness of the rock stratum between the nth rock stratum and the mth rock stratum is shown; q_m-nThe equivalent shear force of the composite beam is kN; a is_iAccumulating the development length of the fracture;

obtaining the maximum shear stress of the rock stratum according to the deflection of each rock stratum solved by the elastic foundation superposed beam force model, judging whether the rock stratum is broken according to a third strength theory, and calculating the shear stress distribution tau on the cross section of the mth rock stratum by using an elastoplasticity mechanical formula_mWhen τ is_m-max≥[τ_m]And when the fracture is large, accumulating the thicknesses of the fractured rock stratums to obtain the development height of the large fracture.

Wherein H_bfLarge fissure development height, h_iThe thickness of the ith layer of rock stratum is shown;

if τ_m-max<[τ_m]And if the m-th rock layer is not broken, calculating to obtain the maximum main stress distribution of different points in the rock layer, checking whether each point is broken point by point, connecting broken points to obtain the micro-fracture development condition, and accumulating the vertical lengths of the micro-fractures to obtain the thickness and the layer position of the micro-fracture area. The rock above the microcracked region is the intact rock. The condition of the stratum fracture zone can provide a basis for selecting a large fracture and micro fracture filling material of a CFBF filling stope.

The overlying strata fracture grouting method specifically comprises the following steps: for a large crack, directly performing grouting sealing by using a CFBF material after drilling; aiming at the micro cracks above the large cracks, the nano particles and CO are adopted after drilling₂In situFormation of CO₂The base nanometer silica gel grouting material seals the mining overburden rock microcracks, solves the technical problem that the conventional large-particle-size aggregate grout cannot penetrate into the rock stratum microcracks, and simultaneously reduces the degree of secondary development of the microcracks induced by high pump pressure required by high-viscosity large-particle-size aggregate grout for plugging the cracks.

Has the advantages that: the method utilizes the solid waste, mine water and CO recovered from industrial waste gas₂Preparing CFBF filling material and CNS grouting material with alkaline silicon-based additive to mineralize and utilize CO₂The method has the advantages that the waste gas ecological protective coal mining is realized, a large amount of waste solid and liquid in a mining area are treated, the subsidence reduction mining and the water retention mining can be realized, the ecological protective mining purpose of low-carbon and high-efficiency mineral resources is achieved, the slurry is injected into the cracks caused by coal mining in time, the water guide channel is sealed, the cracks are prevented from further developing, and the effect of water retention coal mining is achieved.

The method can fill the goaf through the CFBF material, control overlying strata migration, and simultaneously seal the large cracks and the micro cracks respectively by utilizing the CFBF material and the CNS material, thereby realizing water retention coal mining. A large amount of solid-liquid of the smelting-dressing waste generated in the coal production process is filled into the goaf by forming a CFBF filling material, so that the harmless treatment of the solid-liquid of the smelting-dressing waste is realized. CO generated in the coal production and utilization process and in industrial production₂Exhaust gas capture, CO being effected in the form of a slip-in material₂The underground mineralization of.

Drawings

FIG. 1 shows the utilization of CO by wall-type continuous mining and continuous mineralization in this example₂The process schematic diagram of the waste gas ecological protective coal mining method.

FIG. 2 is a flow chart of the wall type continuous mining, continuous filling, mining and charging process in this embodiment.

Fig. 3 is a schematic view of the wall type continuous mining continuous filling system according to the present embodiment.

Fig. 4 is a schematic view of the permeable partition for wall type continuous mining and continuous filling (full mining and partial filling) in the present embodiment.

FIG. 5 is a schematic view of the experimental apparatus for grouting in this example.

Fig. 6 is a flow chart of the wall-type continuous mining and continuous filling (full mining and local filling) process for grouting the large cracks of the overburden rock in the embodiment.

Fig. 7 is a flow chart of the wall-type continuous mining and continuous filling (full mining and local filling) overlying rock micro-fracture grouting process in the embodiment.

In the figure: 1 equipment withdraws the tunnel; 2. an auxiliary lane; 3. a main transportation lane; 4. stope branch roadways; 5. the roadway is filled; 6. filling the roadway; 7. preparing a roadway for filling; 8. mining the roadway; 9. a main material tank (gangue, fly ash and cement); 10. CO 2₂A tank; 11. auxiliary tanks (alkaline silicon-based additive, water); 12. a pulping tank; 13. filling a pipeline; 14. an aqueous layer; 15. a percolation barrier; 16. coal gangue; 17. a containment wall; 18. a boundary pillar of coal; 19. a seepage surge zone; 20. a seepage micro-augmentation zone; 21. the earth surface; 22. a fracture zone; 23. a microcracked region; 24. a pressure pump; 25. grouting tanks; 26. a valve; 27. a pressure gauge; 28. prefabricating a crack test piece; 29. a holder; 30. grouting and drilling a large crack; 31. and (5) grouting and drilling the micro cracks.

Detailed Description

Embodiments of the invention are further described below with reference to the accompanying drawings:

the invention relates to a method for mineralizing and utilizing CO₂An ecological protective coal mining method for waste gas, in particular to a wall type continuous mining continuous filling water-retention coal mining method, which comprises the following steps:

along with the advance of the working face, constructing a sealing wall 17 at two ends of each mined stope branch roadway after each mined stope branch roadway is mined to seal the mined area, and then pouring CO into the sealed area₂The mineralized filling material CFBF carries out mining and filling along with the goaf, and critical key parameters of strength of a filling body required by stability of a mining overburden seepage isolation zone of a CFBF filling stope are ensured in the filling process, so that the goaf is supported after the CFBF filling is solidified; filling a goaf by using CFBF (circulating fluid bed boundary) in a working face, simultaneously defining development heights of mining overburden rock large cracks and micro cracks near the working face respectively, drilling a hole above a stope branch roadway after mining of one stope branch roadway, enabling the drilled hole to penetrate through a seepage surge zone 19 and a seepage surge zone 20, and injecting CFBF to a crack area 22 existing in the seepage surge zone 19 by using the drilled hole to seal the overburden rock large cracks; drilling is then used to drill into the micro-fissures present in the fissured zones 23 present in the vadose zone 20Grouting and sealing are performed to prevent further development of cracks in the mining process.

The CO is₂The mineralized filling material CFBF is prepared according to the mass percentage of 36-48 percent of fly ash, 12-24 percent of coal gangue, 5-10 percent of cement, 3-5 percent of alkaline silicon-based additive and 13-44 percent of mine water; the method comprises the steps of obtaining fly ash and coal gangue generated in the mining process in situ during blending, crushing the coal gangue to obtain gangue powder, mixing and stirring the gangue powder, the fly ash and cement with the particle size of less than 5mm uniformly to obtain a solid mixture, preparing an aqueous solution of an alkaline silicon-based additive by using the alkaline silicon-based additive and water, feeding the aqueous solution into the solid mixture, and introducing CO recovered from industrial waste gas while stirring₂Per cubic meter of CO in the mixture of aqueous solution and solid₂The input amount is 5000L/h-50000L/h, the air input time is within 60 minutes, thereby obtaining CO₂Mineralized filling material CFBF;

and continuously mining and continuously filling by using CFBF in the working face until all the blocks are mined and filled.

As shown in FIG. 1 and FIGS. 2 a-2 f, one mineralization of the present invention utilizes CO₂The waste gas ecological protective coal mining method specifically comprises the following steps:

the method comprises the following steps of firstly, dividing a working face into a plurality of groups of mining blocks, arranging a stoping roadway in the mining blocks according to a normal longwall coal mining method, and mining coal by adopting a wide roadway tunneling mode.

Secondly, arranging an equipment withdrawal roadway 1, an auxiliary roadway 2 and a main transportation roadway 3 along the direction of the working face, excavating and cutting holes along the inclined direction at the edge of the working face to form a ventilation loop, wherein each wide roadway excavation of the whole working face is equal to one time of feed of a normal longwall working face coal mining machine, the width of a stope branch roadway 4 is equal to the size of one time of feed of the coal mining machine, namely, the mining area is arranged in a longwall working face mining mode, and an included angle between the main transportation roadway 3 and the stope branch roadway 4 is 40-60 degrees;

thirdly, dividing m stope branch roadways 4 along the advancing direction of the working face, wherein the first stope branch roadway 4 is arranged at the edge of the stope and close to the cut hole, and the rest mining subsections are sequentially sequenced; dividing the stope roadway into n mining stages, wherein n is 3-5;

taking 16 mining site branch roadways 4 divided into 4 mining stages as an example, wherein each stage comprises 4 roadways, specifically, a filled roadway 5, a filling roadway 6, a standby roadway 7 and a mining roadway 8; firstly, excavating a first stope branch lane 4 in a first mining stage, and then excavating a second stope branch lane 4, a third stope branch lane 4 and a fourth stope branch lane 4 in the first mining stage in sequence until the 4 th stope branch lane 4 in the 1 st mining stage is completely excavated; excavating the second, third and fourth mining stages in sequence according to the mining sequence until all the stope branch roadways 4 in each mining stage are completely excavated;

fifthly, after the excavation of the first stope branch roadway of the first mining stage is finished, immediately excavating a second stope branch roadway of the first mining stage, and simultaneously performing CFBF filling on the first stope branch roadway of the first mining stage to form continuous mining, continuous CFBF filling and CO filling₂And a coal replacement mining and filling mode, and a spare filling roadway 7 is reserved, namely after the first stope branch roadway of the first mining stage is mined, a second stope branch roadway of the first mining stage is immediately mined, after the mining is finished, a third stope branch roadway of the first mining stage is mined, and meanwhile CFBF filling is carried out on the first stope branch roadway of the first mining stage, and the second stope branch roadway of the first mining stage is used as the spare filling roadway 7, so that a mining and filling parallel mining mode of 'mining, filling and filling by one spare' is formed.

Wherein the filling system comprises a ground filling station and a filling pipeline, as shown in FIG. 3, the ground filling station mainly comprises slurry preparation and transportation and corollary equipment thereof, wherein the slurry preparation device comprises a main material tank 9, CO₂The tank 10, the auxiliary material tank 11 and the slurry forming tank 12, and the filling pipeline 13 consists of a drilling pipeline and an underground filling pipeline. When in use, firstly, quantitative gangue, fly ash and cement are injected into the main material tank 9, and quantitative alkaline silicon-based additive and water are injected into the auxiliary material tank 11, and the mixture is uniformly stirred; then the main material and the auxiliary material are simultaneously injected into a slurry forming tank 12 according to the set proportion, and CO is introduced while stirring₂And continuously pulping, and finally automatically conveying the slurry to a filling roadway sealed by a sealing wall 17 through a filling pipeline 13 by means of gravitational potential energy.

Ensuring the critical key parameter of the CFBF novel filling body strength required by the stability of the mining overburden seepage isolation belt of the CFBF filling stope so as to ensure the support of the CFBF filling to the goaf and determine the parameter of the CFBF filling body;

according to the permeability ratio of the mining overburden rock, the overburden rock is divided into a seepage surge zone 19, a seepage micro-surge zone 20 and a seepage isolation zone 15.

k＝αexp[β(σ₁-σ₃)]

In the formula: k is the permeability of the mining overburden rock; alpha and beta are coefficients; sigma₁-σ₃Is overburden rock bias stress.

The method comprises the steps of determining a critical value of a CFBF goaf filling mining parameter for ensuring the stability of a seepage isolation zone, and aiming at different filling mining methods, wherein the critical value comprises a long-wall filling method and a short-wall filling method, the rule of influence of mining overburden unloading and filling body creep on the permeability of overburden is determined, the critical mining parameter of CFBF goaf filling mining, which is characterized in that the instantaneous deformation of the CFBF filling body does not cause sudden instability, and the long-term creep variable of the CFBF filling body is smaller than the maximum creep constraint quantity for ensuring the stability of the seepage isolation zone, comprises the critical value of the CFBF filling rate, the CFBF filling body strength and the CFBF maximum hysteresis filling distance.

In the formula: n is the maximum hysteresis fill distance, σ, of CFBF_pTaking the strength of the coal pillar, F is the coefficient of Pouleia, F is the safety coefficient, taking 1.5-2,the internal friction angle of the overlying strata, h is the mining height and b is the mining space width.

Wherein, the coal seam overlying strata is deformed and damaged by the influence of exploitation, and the vertical and horizontal permeability are changed compared with the original state which is not influenced by the exploitation. The change of the rock stratum permeability is mainly influenced by the damage degree of the rock stratum, so that the mining overburden permeability zoning characteristics of the boundary influence zone are qualitatively analyzed by combining stress and deformation zoning on the basis of the overburden damage degree zoning of the mining area boundary influence zone. The damage degrees of a mining overburden rock collapse zone, a fracture zone and a bending subsidence zone are reduced in sequence, and the rock stratum permeability has obvious difference in the three areas. Thus, the permeability of the boundary affected zone may be zoned in the vertical direction according to the "vertical three zones" of the mining overburden.

Further, as shown in fig. 4, the CFBF mineralized filling material is used for filling mining wall-type continuous mining (full mining local filling) mining, the mining in the first, second and third stages is timely filled, the mining in the fourth stage is not filled after the mining, and a boundary coal pillar 18 is left outside the mining area, so that the method not only can protect the stability of the aquifer 14 and the ground surface 21, but also can save the filling cost.

In this method, a seepage surge zone 19, a seepage micro-surge zone 20 and a seepage isolation zone 15 are formed in the overlying strata of the stope from bottom to top, wherein a saddle-shaped fracture zone 22 is formed in the seepage zone above the stope, and a saddle-shaped micro-fracture zone 23 is formed above the fracture zone. Compared with the conventional mining method, the mining method can not form a caving zone in the overlying strata.

(3) The mine waste solid and liquid, such as gangue, fly ash and mine sewage, are supplemented with cement and alkaline silicon-based additive, and CO is added₂Determining that the stability of the mining overburden seepage isolation zone of the CFBF filling stope can be ensured and CO can be mineralized to the maximum extent₂The key proportion of the CFBF novel filling material is as follows.

The method comprises the following steps of filling a goaf by CFBF in a working face, defining development heights of mining overburden rock large cracks and micro cracks near the working face respectively, drilling a hole above a stope branch roadway after each stope branch roadway is mined, enabling the drilled hole to penetrate through a seepage surge zone 19 and a seepage surge zone 20, and injecting CFBF to a crack area 22 existing in the seepage surge zone 19 by utilizing the drilled hole to seal the overburden rock large cracks; then, the micro-cracks existing in the crack area 23 existing in the seepage micro-increase zone 20 from the drill hole are used for grouting and sealing, and the cracks are prevented from further developing in the mining process.

Wherein the grout injected in the microcrack region 23 is CO₂Mineralized nano silica gel grouting material consisting of nano particles and baseMixing the liquid according to the mass ratio of 1: 1000-100: 1000, and introducing CO₂Production of gas of which CO₂The feeding amount is 10-100L/min, and the base liquid is formed by mixing a base material and water according to the mass ratio of 1: 100-50: 100.

The concrete preparation method of the CFBF filling material comprises the following steps: mixing gangue, fly ash, mine water and cement uniformly according to a ratio, correspondingly adding an alkaline silicon-based additive according to the water quality characteristics of the mine water, and introducing CO₂Developed to CFBF filling material. The yield stress, viscosity and cohesive force of the CFBF filling material and the frictional resistance of the slurry are researched to ensure the transportability of the CFBF filling material; secondly, researching the physical and mechanical properties of the CFBF material to ensure that the CFBF material has enough strength to support a top plate; and finally, researching the micro-morphology of the CFBF filling material, the cracks formed after drying and the combination condition of the material under the micro-structure.

Specific tests on CFBF filler materials:

(ii) rheological action

The rheological properties of the uncured CFBF filler material were measured. Controlled Shear Rate (CSR) test in which the shear rate is controlled from 0.1s at a constant rate over a test time of 120s^-1Linear increase to 150s^-1. The CSR results can be fitted by rheological constitutive equations to determine yield stress and viscosity.

Slump test

Slump reflects the cohesion and frictional resistance of the slurry and is an important index for measuring transportability. In fact, a slump value of 100mm is a fundamental requirement for pack mining. In addition, a filling having a slump value of more than 160mm (minimum slump value of 71) has good transportability. All slump tests were repeated 3 times and the average slump value was used for further analysis.

Coagulation time and bleeding rate

Mixing and stirring the CFBF filling material according to the designed proportion. The coagulation time is measured by an inverted cup method, and the bleeding rate is measured by a cylinder metering method. The initial set time is measured from when the slurry is stirred with water until the slurry loses its flow characteristics at room temperature. The final set time is measured from the time the slurry is stirred with water until the slurry has completely hardened at room temperature. The water seepage rate is the ratio of the calculated water drainage height H to the grouting height H. More specifically, H is the height of the grout in the measuring cup after the measured flow time, and is the height of the discharged water appearing at the top after the slurry has completely hardened.

Uniaxial compressive strength test

After the corresponding cure time is reached, a Uniaxial Compression (UCS) test is performed to apply a displacement load to the specimen at a suitable rate. The peak stress and displacement of each filled specimen was recorded throughout the load failure. To demonstrate the short and medium term strength of the specimens, UCS were measured 3, 7, 14, 28 and 56 days after cure. All tests were repeated 3 times and the average UCS value was calculated for further analysis.

X-ray diffraction (XRD) and electron microscopy Scanning (SEM) -energy spectroscopy (EDS)

After the UCS test, a small portion of the sample was collected. The hydration was stopped with absolute ethanol and the samples were ground to less than 200 mesh. Thereafter, the sample was dried at 50 ℃ for 24 hours, and XRD test was performed to analyze the hydration product of the filled sample. The crushed filler samples were subjected to SEM-EDS analysis to determine their microscopic morphological and structural features. For SEM and XRD analysis it was shown that the process of stopping hydration and the process of mill drying were the same.

(4) A method for defining the development heights of large and micro cracks of mining overburden rock is provided while a CFBF goaf is filled, the CFBF filling material is used for grouting and sealing the large cracks of the mining overburden rock, and CO is used for sealing₂The base nanometer silica gel (CNS) grouting material is used for grouting and sealing the micro cracks and preventing the cracks from further developing in the mining process.

In order to identify the large cracks and micro cracks of the CFBF filling stope, firstly, an elastic foundation superposed beam and a transverse isotropic plane body mechanical model is established:

wherein, tau_m-maxThe maximum shear stress of the rock stratum; e_mThe elastic modulus of the mth rock stratum; h is_mIs the thickness of the mth layer rock stratum; h is_m-nThe thickness of the rock stratum between the nth rock stratum and the mth rock stratum is shown; q_m-nThe equivalent shear force of the composite beam is kN; a is_iAccumulating the development length of the fracture;

obtaining the maximum shear stress of the rock stratum according to the deflection of each rock stratum solved by the elastic foundation superposed beam force model, judging whether the rock stratum is broken according to a third strength theory, and calculating the shear stress distribution tau on the cross section of the mth rock stratum by using an elastoplasticity mechanical formula_mWhen τ is_m-max≥[τ_m]And when the fracture is large, accumulating the thicknesses of the fractured rock stratums to obtain the development height of the large fracture.

Wherein H_bfLarge fissure development height, h_iThe thickness of the ith layer of rock stratum is shown;

if τ_m-max<[τ_m]And if the m-th rock layer is not broken, calculating to obtain the maximum main stress distribution of different points in the rock layer, checking whether each point is broken point by point, connecting broken points to obtain the micro-fracture development condition, and accumulating the vertical lengths of the micro-fractures to obtain the thickness and the layer position of the micro-fracture area. The rock above the microcracked region is the intact rock. The condition of the stratum fracture zone can provide a basis for selecting a large fracture and micro fracture filling material of a CFBF filling stope.

The overlying strata fracture grouting method specifically comprises the following steps: aiming at the large cracks, a CFBF material with larger aggregate grain size is directly used for grouting and sealing; aiming at the micro cracks above the large cracks, the nano particles and CO are adopted₂In situ generation of CO₂The base nanometer silica gel (CNS) grouting material seals mining overburden rock microcracks, solves the technical problem that conventional large-particle-size aggregate grout cannot penetrate rock stratum microcracks, and simultaneously reduces the degree of secondary development of microcracks induced by high pump pressure required by high-viscosity large-particle-size aggregate grout for plugging cracks.

As shown in fig. 5, a grouting experiment device is used for detecting grouting parameters and grouting effect, and the grouting experiment device comprises a pressure pump 24, a grouting tank 25, a valve 26, a pressure gauge 27, a prefabricated crack test piece 28 and a clamp 29; the prefabricated crack test piece 28 is arranged in a sealed clamp 29, a pressure gauge 27 is arranged on the clamp 29, an inlet and an outlet are arranged on two sides of the clamp 29, a grouting tank 25 is connected with a pressure pump 24 and is also connected with the two inlets of the clamp 29 through a valve 26 and the pressure gauge 27, and the outlet of the clamp 29 is sequentially connected with the valve 26 and the pressure gauge 27.

The working process is as follows: firstly, preparing a standard filling body test piece, prefabricating a crack by using a universal testing machine, then placing the test piece into a clamp holder 29, respectively injecting a CFBF material and a CNS material by using a pressure pump 24, testing the grouting parameters and the grouting effect of the two materials, and providing basic data for engineering application.

Further, as shown in fig. 6 and 7, the fracture grouting process is as follows: for large fractures, the grouting step is similar to the filling step. The grouting system mainly comprises a ground grouting station and a grouting pipeline, firstly, quantitative gangue, fly ash and cement are injected into a main material tank 9, quantitative alkaline silicon-based additive and water are injected into an auxiliary material tank 11, and the mixture is uniformly stirred; then, the main material and the auxiliary material are simultaneously injected into a slurry forming tank 12 according to the set proportion, and CO is introduced while stirring₂Continuously pulping; third, grout is injected into the large fracture zone 22 through the large fracture grout bore 30. Aiming at the microcrack grouting, the general steps are consistent with the steps, but the main material tank 9 is not needed, meanwhile, nanoparticles are needed to be added into the auxiliary material tank 11, and finally, the prepared slurry is injected into the microcrack area 23 through the microcrack grouting drill hole 31.

Example 1: this example takes a particular mine in Shanxi. The average buried depth of the coal seam is about 220 m. The average length of the block is 330m, the average width is about 160m, and the reserve is about 20 ten thousand t. The upper part of the mining area is provided with a shallow water layer containing water and surface 21 water, the mining coal layer is XV number coal, the average thickness is 2.4m, and the dip angle is 1-2 degrees. The direct roof is limestone with the average thickness of 8.5m and the unidirectional compressive strength of 54.0-213.0 MPa. An IX number coal layer (a bedrock section which is separated from the direct top of limestone by about 20m and mainly contains sandy mudstone, limestone, fine sandstone, mudstone and the like, and the lithology is medium-hard overall) is also formed above the XV number coal. An effective water barrier layer (bedrock sections with the middle interval of about 20m, mainly comprising sandy mudstone, limestone, fine sandstone and mudstone, and the whole lithology is medium-hard) consisting of sandy mudstone and mudstone exists about 24m above the IX coal seam, the total thickness reaches 13.0m, the water barrier layer is about 57.0m above the XV coal seam, and a sandstone aquifer 14 is arranged above the XV coal seam.

Principal parameters

Width of stope branch roadway

In view of mining efficiency, in order to reduce the number of times of moving the working face to improve the coal mining efficiency of the continuous coal mining machine, the width of the stope branch roadway should be as large as possible, and the width of the stope branch roadway should be more than 5.0 m. From the aspect of surrounding rock control, in order to reduce the sinking amount of the roof before filling, the width of the stope branch roadway is as small as possible, and the width of the stope branch roadway is not more than 6.0 m. And determining the branch roadway width of the stope to be 6.0m and the height to be 2.6m according to the mining geological conditions of the test block and the mining experience of the mine.

② spacing coal pillar (spacer) width

The function of the coal pillar spacing: the function of the spacing coal pillars (isolating bodies) is to provide effective support for the top plate of the goaf in the stope branch roadway mining and filling processes, and control the movement of overlying strata and the subsidence of the earth surface 21. The internal structure of the coal pillar (isolated body) is as follows: and (4) the width of the spacing coal pillar, namely the width of N-1 stope branch roadways. In the 1 st mining stage, the spacer coal pillar is composed of solid coal (several stope roadways that have not yet been mined). In the 2 nd mining stage and the subsequent mining stage, the coal mine filling material consists of solid coal (a plurality of stope branch roadways which are not mined yet) and filling bodies which meet the design strength requirement. The last mining phase consists entirely of the pack. The separator width was determined to be 18 m. And under the condition that the designed width of the stope branch roadway is 6.0m, dividing the stope branch roadway in the whole block section into 4 mining stages.

Width of spacer

The design principle of the width of the separator is as follows: in order to ensure that the isolated body has certain bearing capacity and can effectively support the top plate in the stope branch roadway mining and filling processes, the width of the isolated body is as large as possible; the strength index of the filling body is determined by the curing time of the filling body, so that the strength of the filling body can be ensured to meet the design requirement only when the filling body meets the curing time requirement before the next stage of mining.

Filling system and process flow

Filling system

The filling system is composed of a ground filling station and a filling pipeline. The ground filling station mainly comprises slurry preparation, transportation and corollary equipment thereof, wherein the slurry preparation device comprises a main material tank 9 and CO₂A tank 10, an auxiliary material tank 11 and a pulping tank 12. The filling pipeline consists of a drilling pipeline and an underground filling pipeline.

Filling process flow

Firstly, quantitative fly ash, coal gangue 16 and cement are injected into a main material tank 9; then, the mixture is simultaneously injected into a slurry forming tank 12 with the aqueous solution of the alkaline silicon-based additive according to the set proportion, and CO is introduced while stirring₂And preparing the CFBF material. Secondly, the slurry is automatically conveyed to a filling roadway sealed by a sealing wall 17 through a filling pipeline by means of gravitational potential energy, and a CFBF material is used for filling; finally, the filling line is flushed.

Application effects

From the economic point of view, the partial corner area in the example panel area is not suitable for arranging stope branch roadways, coal in the area is not mined, and the mining rate of the whole test block section is 96.8%. The stope branch roadway filling and roof connecting effect and the ground surface 21 subsidence control effect are good.