Mining method for reducing floor loss and balancing roof water conservation by forming a self-forming roadway without coal pillar

Abstract

The present invention discloses a method for balanced water conservation mining of the roof with reduced damage of the bottom plate of a self-forming lane without coal pillars, which relates to the technical field of coal mining, and includes the following steps: calculating the height of the water-conducting fracture zone of the roof and the depth of the water-conducting damage zone of the bottom plate; carrying out pre-splitting and top cutting design and support design of the self-forming lane without coal pillars; carrying out grouting reinforcement of the roof plate, grouting reinforcement of the bottom plate, and filling of the goaf area behind the frame; according to the above steps, the balanced water conservation mining of the roof with reduced damage of the bottom plate of the self-forming lane without coal pillars is finally realized. The present invention adopts the above-mentioned method for balanced water conservation mining of the roof with reduced damage of the bottom plate of the self-forming lane without coal pillars, which ensures the stability of the aquifers at the top and bottom plates of the coal seam. On the one hand, the coal pillars in conventional mining are eliminated, the damage to the bottom plate caused by the stress concentration of the bottom plate is reduced by unloading the pressure by cutting the top plate, and the water conservation mining of the bottom plate is realized by three-dimensional reinforcement of the bottom plate; on the other hand, balanced mining is realized by grouting reinforcement outside the top cutting range of the roof plate and rock mass expansion regulation within the top cutting range, which reduces the subsidence of the overburden rock and realizes the water conservation mining of the roof plate.

Description

Technical Field

[0001] The invention relates to the technical field of coal mining, in particular to a coal pillar-free self-forming laneway bottom plate loss reduction roof plate balance water conservation mining method. Background Art

[0002] At present, more than 90% of my country's coal resources are mined by longwall mining. Longwall mining is an efficient underground coal mining method. It arranges longwall working faces in coal seams and uses mechanized equipment to complete coal cutting, loading and support operations. Depending on whether coal pillars are left between working faces, it can be divided into a coal pillar mining system and a coal pillar-free mining system. Among them, the coal pillar-free self-forming lane mining method is currently the more advanced coal pillar-free mining system. There are two major problems in how to protect water resources (water conservation mining) under the conditions of large-scale coal mining in my country:

[0003] (1) In the coal pillar mining system, coal pillars are left between working faces. Due to the stress concentration of coal pillars, uneven distribution of confining pressure and unbalanced settlement and deformation, on the one hand, the roof rock strata will form a complete "three zones" (collapse zone, water-conducting fracture zone and curved lower zone). Once the collapse zone or water-conducting fracture zone is connected to the roof aquifer, it will cause the loss of roof water resources and affect the ecological environment; on the other hand, due to the retention of coal pillars, a certain range of "compression-tension zone" and "compression-shear zone" exist in the floor rock strata near the coal pillars, and the maximum damage depth increases. If the floor damage zone is connected to the floor aquifer, the floor water will flow into the mining space through the water-conducting channel, causing the water-bearing structure to be destroyed.

[0004] (2) As a new method of coal pillar-free mining, self-forming lane mining can improve resource recovery rate by eliminating coal pillars and alleviate the problem of mining and excavation continuity tension, but how to take effective methods to achieve water-saving and balanced mining still needs to be solved. It is mainly reflected in:

[0005] However, there are still the following problems to be solved:

[0006] ① When the distance between the mining coal seam and the roof and floor aquifers is determined and the thickness of the coal seam is thin or medium-thick, in order to achieve water-preserving mining on the floor, there is a lack of design methods for the top cutting height that considers the filling degree of the goaf. How to use technical means such as pressure relief to reduce the damage range of the floor compression / shear zone and reduce the floor water-conducting damage zone and depth is still unknown, that is, how to achieve floor loss reduction and achieve bottom water-preserving mining.

[0007] ② When the top-cut rock mass cannot fill the goaf due to thick coal seams and large mining height, the water-conducting fracture zone of the roof and the water-conducting damage zone of the floor may be connected to the aquifer. At this time, adjusting the top-cut height can no longer meet the requirements of water-preserving mining. It is unknown how to improve the filling degree in the mining space, meet the support function of the top plate of the goaf, and achieve effective support and balanced mining of the overburden and middle and high rock strata, that is, how to avoid the sinking of the roof, achieve balanced mining, and achieve mining with water preservation on the roof. Summary of the invention

[0008] The purpose of the present invention is to provide a method for balanced water-preserving mining of the roof with reduced floor damage and without coal pillars, so as to solve the problems raised in the above-mentioned background technology, ensure the stability of the aquifers on the roof and floor of the coal seam, realize balanced mining, reduce the subsidence of the overburden rock, and realize water-preserving mining of the roof.

[0009] To achieve the above object, the present invention provides a coal pillar-free self-forming roadway floor loss reduction roof balance water conservation mining method, comprising the following steps:

[0010] Step S1, conduct a pumping test and drill and coring the top and bottom rock layers to determine the properties of the top and bottom rock layers, the distance between the coal seam and the aquifer, and the properties of the aquifer, and calculate the height of the water-conducting fracture zone in the roof and the depth of the water-conducting damage zone in the bottom;

[0011] Step S2, based on the surrounding rock properties, according to theoretical formulas and numerical simulations, pre-splitting and top cutting design and support design of self-forming tunnel without coal pillars are carried out;

[0012] Step S3, conducting a series of numerical simulation tests based on the physical and mechanical parameters of the rock formation, the pre-splitting and top cutting design of the self-forming roadway without coal pillars, and the support design results;

[0013] Step S4: when the water-conducting fracture zone of the roof or the water-conducting damaged zone of the bottom plate is connected to the aquifer, grouting reinforcement of the roof, grouting reinforcement of the bottom plate and filling of the goaf behind the frame are selected accordingly according to different situations;

[0014] Step S5, according to the above steps, finally realize the coal pillar-free self-forming roadway bottom plate loss-reducing roof balanced water-preserving mining.

[0015] Preferably, in step S1, the height H of the water-conducting fracture zone of the roof is calculated. R The formula is as follows:

[0016]

[0017] Among them, H R is the height of the water-conducting fracture zone in the medium-hard roof, m; M is the thickness of the coal seam, m;

[0018] The formula for calculating the depth d of the bottom plate water-conducting damage zone is as follows:

[0019] d=0.0085T+0.1665a+0.1079L-4.3579

[0020] Among them, d is the depth of the bottom water-conducting damage zone, m; T is the average mining depth, m; a is the inclination angle of the coal seam, °; L is the inclined length of the working face, m.

[0021] Preferably, the specific steps of step S2 are as follows:

[0022] Step S21: When the mining height is less than 5m, the cutting height H F The value range is preliminarily determined by the following formula:

[0023] H F =(H C -ΔH1-ΔH2) / (K-1)

[0024] Among them, H C is the mining height, ΔH1 is the roof subsidence, ΔH2 is the floor heave, and the expansion coefficient K=K0e -at , K0 is the initial expansion coefficient of the roof collapse rock mass, a is the undetermined coefficient, and t is the time variable;

[0025] Step S22: When the mining height is above 5m, the cutting height H F The value range is preliminarily determined by the following formula:

[0026] H F =(H C -ΔH1-ΔH2-ΔH B ) / (K-1)

[0027] Among them, H C is the mining height, ΔH1 is the roof subsidence, ΔH2 is the floor heave, ΔH B is the filling height.

[0028] Preferably, the specific steps of step S3 are as follows:

[0029] Step S31, in the case of thin and medium thick coal layers, the volume of the collapsed rock mass at different top cutting heights is such that it satisfies the following equation:

[0030] △V m =△V B =(K-1)H C S

[0031] Among them, △V m is the mining volume, △V B is the crushing volume, S is the mining area;

[0032] Under the condition that the above equations are satisfied, the development of roof collapse zone, fracture zone and the range of bottom plate water conduction damage zone are calculated and compared with the distance of roof and bottom plate aquifers, including three cases;

[0033] Step S32: In the case of thick coal seams with large mining height, when the roof expansion cannot completely fill the goaf, the roof water-conducting fracture zone and the bottom plate water-conducting damaged zone are connected to the aquifer. According to different situations, the properties of the aquifer are considered and grouting reinforcement of the bottom plate and filling of the goaf behind the frame are carried out to ensure that the aquifer structure is not damaged.

[0034] Preferably, the three situations in step S31 include:

[0035] (4) The height of the roof fracture zone or the depth of the floor water-conducting damage zone has not reached the pre-protected aquifer position, and construction and mining are carried out according to the design parameters without taking any control measures;

[0036] (5) When the height of the roof fracture zone or the depth of the bottom water-conducting damage zone just reaches the position of the pre-protected aquifer, adjust the top cutting height H C 2. Take measures such as deep and shallow hole combination blasting and support cyclic loading and unloading to increase the degree of collapse and expansion of the rock mass, and ensure that the aquifer structure is not affected by mining;

[0037] (6) If the height of the roof fracture zone or the depth of the bottom water-conducting damage zone exceeds the position of the pre-protected aquifer, adjust the top cutting height H C Or if the extent of the collapsed rock mass is no longer able to meet the requirements of water conservation mining and lane retention at the same time, three-dimensional grouting reinforcement of the bottom plate or grouting transformation of the aquiclude and aquifer outside the top plate cutting range shall be adopted.

[0038] Preferably, the method adopted for the roof grouting reinforcement in step S4 is underground advance drilling grouting to reinforce and transform the aquifer and aquiclude outside the top cutting range.

[0039] Preferably, the bottom plate grouting reinforcement in step S4 includes:

[0040] Step S41, making the final hole pressure of the drilling grouting reach 1.5 to 2.0 times the water pressure P of the aquifer;

[0041] Step S42, the peripheral reinforcement range of the working face is L=L1+30m, where L1 is the peripheral mining influence range of the coal seam, which is comprehensively determined by plastic mechanics theory and numerical simulation;

[0042] Step S43, the bottom plate grouting reinforcement depth D1 is calculated according to the water inrush coefficient of the normal block section being no more than 0.1MPa / m and the water inrush coefficient of the structural damage section being no more than 0.06MPa / m, as shown in the following formula:

[0043] D1=d+[(Pd×0.06)÷0.1]

[0044] Among them, P is the water pressure of the aquifer and d is the maximum depth of the bottom plate water conduction damage zone.

[0045] Preferably, the filling of the goaf after the support in step S4 includes: using a grouting support to inject coal gangue and fly ash into the goaf after the coal seam is mined, and the filling volume V C As shown below:

[0046] V C =V m -V B

[0047] Among them, V m Represents the mining volume, V B Indicates the volume of rock collapse and expansion.

[0048] Therefore, the present invention adopts the above-mentioned coal pillar-free self-forming tunnel bottom plate damage reduction roof balanced water-preserving mining method to ensure the stability of the coal seam top and bottom plate aquifers. On the one hand, it eliminates the coal pillars in conventional mining, reduces the bottom plate damage caused by bottom plate stress concentration by top cutting and unloading, and realizes bottom plate water-preserving mining through three-dimensional reinforcement of the bottom plate; on the other hand, balanced mining is achieved through grouting reinforcement outside the top cutting range and rock mass expansion regulation within the top cutting range, reducing overburden subsidence and realizing roof water-preserving mining.

[0049] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0050] Figure 1 It is a process flow chart of an embodiment of the method for mining with reduced roof balance and water conservation by self-forming laneway floor without coal pillars according to the present invention;

[0051] Figure 2 The schematic diagram of adjusting the top cutting height and the crushing expansion degree to realize water conservation mining in the present invention, wherein Figure (a) is a schematic diagram of adjusting the top cutting height, and Figure (b) is a schematic diagram of increasing the crushing expansion degree;

[0052] Figure 3 Schematic diagram of the grouting reinforcement of the bottom plate of the present invention, wherein Figure (a) is a plan view, and Figure (b) is an AA cross-sectional view;

[0053] Figure 4 This is a schematic diagram of the grouting transformation outside the top cutting range of the present invention;

[0054] Figure 5 This is a schematic diagram of filling the goaf area behind the frame of the present invention;

[0055] Figure numerals: 1. Constant resistance anchor cable; 2. Reserved tunnel; 3. Coal seam at the mining side working face; 4. Roof aquifer; 5. Roof impermeable layer; 6. Old roof stratum; 7. Direct roof stratum; 8. Coal seam at the next working face; 9. Direct bottom stratum; 10. Old bottom stratum; 11. Bottom impermeable layer; 12. Bottom aquifer; 13. Reserved tunnel track; 14. Roof pre-splitting seam line; 15. Gangue retaining support equipment; 16. Temporary support equipment behind the frame; 17. Goaf after gangue crushing and expansion filling; 18. Reserved tunnel; 19. Directed pre-splitting seam; 20. Development range of the roof fissure zone; 21. Development range of the roof collapse zone; 22. Development range of the floor water-conducting damage zone; 23. Adjusted roof cutting height range; 24. Collapsed goaf; 25. Coal seam of the current working face; 26. Another drift tunnel of the working face; 27. Goaf of the previous working face; 28. Grouting drilling holes of the floor; 29. ​​Hydraulic support of the working face; 30. Goaf of the current working face; 31. Underground drilling site; 32. Slurry diffusion of the floor; 33. Grouting drilling holes of the roof; 34. Slurry diffusion outside the roof cutting range; 35. Goaf filling body. DETAILED DESCRIPTION

[0056] The technical solution of the present invention is further described below through the accompanying drawings and embodiments.

[0057] Unless otherwise defined, the technical terms or scientific terms used in the present invention should be understood by people with ordinary skills in the field to which the present invention belongs. The words "first", "second" and similar words used in the present invention do not indicate any order, quantity or importance, but are only used to distinguish different components. "Include" or "comprise" and similar words mean that the elements or objects appearing before the word include the elements or objects listed after the word and their equivalents, without excluding other elements or objects. "Connect" or "connected" and similar words are not limited to physical or mechanical connections, but may include electrical connections, whether direct or indirect. "Up", "down", "left", "right" and the like are only used to indicate relative positional relationships. When the absolute position of the described object changes, the relative positional relationship may also change accordingly.

[0058] Example

[0059] See also Figure 1-5 The present invention provides a method for balanced water-preserving mining with reduced floor and roof in a self-forming lane without coal pillars. The method uses directional pre-cracking on the side of the goaf so that the roof of the goaf after mining slides along the pre-cracking position. Due to the crushing and expansion characteristics of the gangue, the goaf can be filled, thereby realizing balanced mining. Since the top is cut to relieve pressure and no coal pillars are left, the goaf can maintain mechanical balance in time, the range of the roof collapse zone is increased, the range of the roof fracture zone is reduced, there is no "compression-tension / compression-shear zone" on the floor, and the range of the water-conducting damage zone of the floor is reduced, thereby realizing water-preserving mining.

[0060] Aiming at the situation of pillarless self-forming mining in thin and medium-thick coal seams, a design method for the top cutting height considering different filling degrees of the goaf is proposed; when adjusting the key parameters of the pillarless self-forming mining still cannot avoid the destruction of the aquifer structure, countermeasures such as grouting reinforcement of the bottom plate or grouting transformation of the aquiclude and aquifer outside the range of roof cutting are proposed.

[0061] When mining thick coal seams with large mining heights and no coal pillars in self-forming tunnels, the natural collapse of the roof and the rock mass cutting and expansion cannot completely fill the goaf, and the water-conducting fracture zone of the roof and the water-conducting damage zone of the floor may be connected to the aquifer. At this time, the goaf filling and the floor grouting reinforcement should be carried out according to different situations. Therefore, in order to ensure that the aquifer structure is not damaged, a floor grouting reinforcement parameter design method considering the properties of the aquifer and a post-frame mining and filling coordinated control technology are proposed.

[0062] The method for mining without coal pillars and self-forming laneway with reduced floor loss and balanced roof water conservation of the present invention specifically comprises the following steps:

[0063] Step S1, conduct a pumping test and drill and coring the top and bottom rock layers to determine the properties of the top and bottom surrounding rocks, the distance between the coal seam and the aquifer, and the properties of the aquifer, and calculate the height of the roof water-conducting fracture zone and the depth of the bottom water-conducting damage zone.

[0064] In the above step S1, the height H of the water-conducting fracture zone in the roof is calculated. R The formula is as follows:

[0065]

[0066] Among them, H R is the height of the water-conducting fracture zone in the medium-hard roof, m; M is the thickness of the coal seam, m;

[0067] The formula for calculating the depth d of the bottom plate water-conducting damage zone is as follows:

[0068] d=0.0085T+0.1665a+0.1079L-4.3579

[0069] Among them, d is the depth of the bottom water-conducting damage zone, m; T is the average mining depth, m; a is the inclination angle of the coal seam, °; L is the inclined length of the working face, m.

[0070] Step S2, based on the surrounding rock properties, according to theoretical formulas and numerical simulations, pre-splitting and top cutting design and support design of the self-forming tunnel without coal pillars are carried out.

[0071] The specific steps of the above step S2 are as follows:

[0072] Step S21: When the mining height is less than 5m, the cutting height H F The value range is preliminarily determined by the following formula:

[0073] H F =(H C -ΔH1-ΔH2) / (K-1)

[0074] Among them, H C is the mining height, ΔH1 is the roof subsidence, ΔH2 is the floor heave, and the expansion coefficient K=K0e -at , K0 is the initial expansion coefficient of the roof collapse rock mass, a is the undetermined coefficient, and t is the time variable;

[0075] Step S22: When the mining height is above 5m, the cutting height HF shall not only consider the above-mentioned rock mass expansion and collapse, but also consider the use of mining and filling coordinated control technology to fill the goaf after the frame, so that the volume of rock mass collapse and expansion plus the filling volume can support the goaf roof. F The value range is preliminarily determined by the following formula:

[0076] H F =(H C -ΔH1-ΔH2-ΔH B ) / (K-1)

[0077] Among them, H C is the mining height, ΔH1 is the roof subsidence, ΔH2 is the floor heave, ΔH B is the filling height.

[0078] Step S3, a series of numerical simulation tests are carried out according to the physical and mechanical parameters of the rock formation, the pre-splitting and top cutting design of the self-forming tunnel without coal pillars, and the support design results.

[0079] The specific steps of the above step S3 are as follows:

[0080] Step S31, in the case of thin and medium thick coal layers, the volume of the collapsed rock mass at different top cutting heights is such that it satisfies the following equation:

[0081] △V m =△V B =(K-1)H C S

[0082] Among them, △V m is the mining volume, △V B is the crushing volume, S is the mining area;

[0083] When the above equations are satisfied, the development of the roof collapse zone, fracture zone and the range of the bottom plate water conduction damage zone are calculated and compared with the distance between the roof and bottom plate aquifers, including three cases as follows:

[0084] (1) The height of the roof fracture zone or the depth of the bottom water-conducting damage zone has not reached the pre-protected aquifer. In this case, construction and mining are carried out according to the design parameters without taking additional control measures, such as Figure 1 As shown, 1 is a constant resistance anchor cable; 2 is a reserved roadway; 3 is a coal seam on the mining side; 4 is a roof aquifer; 5 is a roof aquifer; 6 is an old roof stratum; 7 is a direct roof stratum; 8 is a coal seam on the next working face; 9 is a direct bottom stratum; 10 is an old bottom stratum; 11 is a bottom aquifer; 12 is a bottom aquifer; 13 is a reserved roadway track; 14 is a pre-cracked seam line on the roof; 15 is a gangue retaining support device; 16 is a temporary support device after the frame; 17 is a goaf after gangue crushing and expansion filling; 18 is a reserved roadway. In this case, before the mining of the working face, the reserved roadway 2 is first reinforced with a constant resistance anchor cable 1 (see Figure 1 (a)), and then the top plate is pre-cracked to form a top plate pre-crack seam line 14 (see Figure 1 (b)). After the working face is mined, the roof collapses and expands to form a goaf 17 filled with waste rock. At the same time, waste rock retaining support equipment 15 and temporary support equipment 16 are installed to maintain the stability of the tunnel (see Figure 1 (c)). As the lag distance increases, the reserved tunnel 2 gradually recovers stability. At this time, the temporary support equipment 16 is withdrawn in batches for recycling, and finally forms 18 that does not damage the aquifer structure (see Figure 1 (d)).

[0085] (2) The height of the roof fracture zone or the depth of the bottom water-conducting damage zone just reaches the position of the pre-protected aquifer. At this time, the top cutting height H needs to be adjusted. C 2. Take measures such as deep and shallow hole combined blasting and support cyclic loading and unloading to increase the degree of collapse and expansion of the rock mass to ensure that the aquifer structure is not affected by mining. Figure 2 As shown, 19 is the directional pre-crack cut; 20 is the development range of the roof crack zone; 21 is the development range of the roof collapse zone; 22 is the development range of the bottom plate water-conducting damage zone; 23 is the adjusted top cutting height range; 24 is the collapsed goaf. Figure 1 Based on the process flow of the bottom plate loss reduction and roof balance water conservation mining method without coal pillars, the range of the top cutting height to be adjusted 23 and the range of the roof collapse zone development 21 are adjusted, thereby reducing the range of the roof fracture zone development 20 and the range of the floor water conduction damage zone development 22, and finally achieving water conservation mining (see Figure 2 (a)). In addition, measures such as shallow hole combined blasting and support cyclic loading and unloading can be taken to increase the degree of collapse of the rock mass, and finally fill the collapsed goaf 24, thereby reducing the development range 20 of the roof fracture zone and the development range 22 of the floor water-conducting damage zone, and achieving the goal of water conservation mining (see Figure 2 (b)).

[0086] (3) When the height of the roof fracture zone or the depth of the bottom water-conducting damage zone exceeds the position of the pre-protected aquifer, the top cutting height H is adjusted. C Or the collapse of the rock mass can no longer meet the requirements of water conservation and tunnel retention, so it is necessary to adopt three-dimensional grouting reinforcement of the bottom plate, such as Figure 3 As shown, 25 is the coal seam of this working face; 26 is another drift tunnel of the working face; 27 is the goaf of the previous working face; 28 is the bottom plate grouting drilling hole; 29 is the hydraulic support of the working face; 30 is the goaf of this working face; 31 is the underground drilling site; 32 is the bottom plate slurry diffusion. For bottom plate water conservation mining, the bottom plate grouting reinforcement method should be used in advance, and a suitable underground drilling site 31 should be selected to carry out the bottom plate grouting drilling 28 construction, so that the bottom plate slurry diffusion 32 covers a certain area of ​​the bottom plate outside the entire working face for reinforcement, and then carry out Figure 1 The process of water conservation and successful tunnel retention is finally achieved. Or the grouting transformation of the aquifer and aquifer outside the roof cutting range, such as Figure 4 As shown, 33 is the top plate grouting drilling hole; 34 is the grouting diffusion outside the top cutting range. In this case, the top plate grouting drilling hole 33 is constructed to the top plate outside the top cutting range, and then the grouting diffusion 34 outside the top cutting range covers it to achieve the sealing and reinforcement of the water-conducting cracks in the top plate, and then the top plate grouting is carried out. Figure 1 The technological process realizes water-preserving mining and successful lane retention.

[0087] Step S32: In the case of thick coal seams with large mining height, when the roof expansion cannot completely fill the goaf, the water-conducting fracture zone of the roof and the water-conducting damage zone of the floor are connected to the aquifer. According to different situations, the properties of the aquifer are considered and the roof and floor grouting reinforcement and the back-end goaf filling are carried out. Figure 5 As shown, 35 is the goaf filling body. The purpose of the back-up goaf filling is to compensate for the space that cannot be filled by the gangue in the goaf, so that the entire goaf can be filled and compacted after the gangue is crushed and expanded. The filling material of the goaf filling body 35 can be selected from coal gangue, fly ash and other materials, so that after the coal seam is mined, the solidification of the filling body and the crushing and expansion of the gangue can be carried out simultaneously. In this case, the aquifer structure of the roof and floor can be maintained, and the roadway can be safely retained.

[0088] Step S4: When the water-conducting fracture zone of the roof or the water-conducting damaged zone of the bottom plate is connected to the aquifer, grouting reinforcement of the roof, grouting reinforcement of the bottom plate and filling of the goaf behind the frame are selected according to different situations.

[0089] Roof grouting reinforcement: The method adopted is underground advance drilling and grouting to reinforce and transform the aquifer and impermeable layer outside the top cutting range.

[0090] Bottom slab grouting reinforcement includes:

[0091] Step S41, making the final hole pressure of the drilling grouting reach 1.5 to 2.0 times the water pressure P of the aquifer;

[0092] Step S42, the peripheral reinforcement range of the working face is L=L1+30m, where L1 is the peripheral mining influence range of the coal seam, which is comprehensively determined by plastic mechanics theory numerical value and simulation;

[0093] Step S43, the bottom plate grouting reinforcement depth D1 is calculated according to the water inrush coefficient of the normal block section being no more than 0.1MPa / m and the water inrush coefficient of the structural damage section being no more than 0.06MPa / m, as shown in the following formula:

[0094] D1=d+[(Pd×0.06)÷0.1]

[0095] Among them, P is the water pressure of the aquifer and d is the maximum depth of the bottom plate water conduction damage zone.

[0096] Backfilling of goaf after support: After coal seam recovery, the goaf is filled with coal gangue and fly ash by grouting support. The filling volume is V C As shown below:

[0097] V C =V m -V B

[0098] Among them, V m Represents the mining volume, V B Indicates the volume of rock collapse and expansion. Based on the above calculation results, taking into account the compression deformation and settlement of the filling body, a filling coefficient of 1.2 to 1.5 is added.

[0099] Step S5, according to the above steps, first change the coal mining method, carry out the design of self-forming mining without coal pillars, judge whether water-preserving mining can be achieved according to the specific parameters after design, and then take corresponding technical measures to ensure that the aquifer structure is not destroyed, and finally achieve self-forming mining without coal pillars with reduced bottom plate and balanced water-preserving mining on the top plate, and reserve a drift for the next working face to achieve mining without coal pillars.

[0100] Therefore, the present invention adopts the above-mentioned coal pillar-free self-forming tunnel bottom plate damage reduction roof balanced water-preserving mining method to ensure the stability of the coal seam top and bottom plate aquifers. On the one hand, it eliminates the coal pillars in conventional mining, reduces the bottom plate damage caused by bottom plate stress concentration by top cutting and unloading, and realizes bottom plate water-preserving mining through three-dimensional reinforcement of the bottom plate; on the other hand, balanced mining is achieved through grouting reinforcement outside the top cutting range and rock mass expansion regulation within the top cutting range, reducing overburden subsidence and realizing roof water-preserving mining.

[0101] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that they can still modify or replace the technical solution of the present invention with equivalents, and these modifications or equivalent replacements cannot cause the modified technical solution to deviate from the spirit and scope of the technical solution of the present invention.

Claims

1. A coal pillar-free self-forming roadway bottom plate loss reduction roof plate balance water conservation mining method, characterized in that: The following steps are involved: Step S1, conduct a pumping test and drill and coring the top and bottom rock layers to determine the properties of the top and bottom rock layers, the distance between the coal seam and the aquifer, and the properties of the aquifer, and calculate the height of the water-conducting fracture zone in the roof and the depth of the water-conducting damage zone in the bottom; In step S1, the height of the water-conducting fracture zone in the roof is calculated The formula is as follows: = in, is the height of water-conducting fracture zone in the medium-hard roof, m; is the thickness of the coal seam, m; Calculate the depth of the bottom plate water-conducting damage zone The formula is as follows: in, is the depth of the bottom plate water-conducting damage zone, m; is the average mining depth, m; is the coal seam inclination, °; is the inclined length of the working surface, m; Step S2, based on the surrounding rock properties, according to theoretical formulas and numerical simulations, pre-splitting and top cutting design and support design of self-forming tunnel without coal pillars are carried out; Step S3, conducting a series of numerical simulation tests based on the physical and mechanical parameters of the rock formation, the pre-splitting and top cutting design of the self-forming roadway without coal pillars, and the support design results; The specific steps of step S3 are as follows: Step S31, in the case of thin and medium thick coal layers, the volume of the collapsed rock mass at different top cutting heights is such that it satisfies the following equation: in, For mining volume, is the crushing volume, is the mining area, is the mining height, the expansion coefficient , is the initial expansion coefficient of the roof collapse rock mass, is the coefficient to be determined, is the time variable; Under the condition that the above equations are satisfied, the development of roof collapse zone, fracture zone and the range of bottom plate water conduction damage zone are calculated and compared with the distance of roof and bottom plate aquifers, including three cases; The three situations in step S31 include: (1) The height of the roof fracture zone or the depth of the floor water-conducting damage zone has not reached the pre-protected aquifer. Construction and mining are carried out according to the design parameters without taking any control measures. (2) When the height of the roof fracture zone or the depth of the bottom water-conducting damage zone just reaches the position of the pre-protected aquifer, adjust the top cutting height.

2. Take measures such as deep and shallow hole combination blasting and support cyclic loading and unloading to increase the degree of collapse and expansion of the rock mass, and ensure that the aquifer structure is not affected by mining; (3) If the height of the roof fracture zone or the depth of the bottom water-conducting damage zone exceeds the position of the pre-protected aquifer, adjust the top cutting height Or the extent of collapse and expansion of the rock mass can no longer meet the requirements of water conservation and tunnel retention at the same time, and the bottom plate is reinforced by three-dimensional grouting or the waterproof layer and aquifer outside the top plate cutting range is transformed by grouting; Step S32: In the case of thick coal seams with large mining height, when the roof expansion cannot completely fill the goaf, the roof water-conducting fracture zone and the floor water-conducting damage zone are connected to the aquifer. According to different situations, the properties of the aquifer are considered and the floor grouting reinforcement and the back-end goaf filling are performed to ensure that the aquifer structure is not damaged; Step S4: when the water-conducting fracture zone of the roof or the water-conducting damaged zone of the bottom plate is connected to the aquifer, grouting reinforcement of the roof, grouting reinforcement of the bottom plate and filling of the goaf behind the frame are selected accordingly according to different situations; Step S5, according to the above steps, finally realize the coal pillar-free self-forming roadway bottom plate loss-reducing roof balanced water-preserving mining.

2. The method for coal pillar-free self-forming roadway floor loss reduction roof balance water conservation mining according to claim 1 is characterized in that: The specific steps of step S2 are as follows: Step S21: When the mining height is less than 5m, the cutting height The value range is preliminarily determined by the following formula: in, is the mining height, is the roof subsidence, is the amount of bottom heave, the coefficient of crushing expansion , is the initial expansion coefficient of the roof collapse rock mass, is the coefficient to be determined, is the time variable; Step S22: When the mining height is above 5m, the cutting height The value range is preliminarily determined by the following formula: in, is the mining height, is the roof subsidence, is the amount of basal distension, is the filling height.

3. The method for coal pillar-free self-forming roadway floor loss reduction roof balance water conservation mining according to claim 1 is characterized in that: The method adopted for the roof grouting reinforcement in step S4 is underground advance drilling grouting to reinforce and transform the aquifer and aquiclude outside the top cutting range.

4. The method for coal pillar-free self-forming laneway floor loss reduction roof balance water conservation mining according to claim 3 is characterized in that: The bottom plate grouting reinforcement in step S4 includes: Step S41: Make the final hole pressure of drilling grouting reach the water pressure of the aquifer P 1.5 to 2.0 times; Step S42: Reinforcement of the periphery of the working surface ,in The peripheral mining influence range of the coal seam is determined by plastic mechanics theory and numerical simulation; Step S43: Bottom plate grouting reinforcement depth The calculation is based on the assumption that the water inrush coefficient of the normal block section is no more than 0.1MPa / m and the water inrush coefficient of the structural damage section is no more than 0.06MPa / m, as shown in the following formula: in, is the aquifer water pressure, It is the maximum depth of the bottom plate water-conducting damage zone.

5. The method for coal pillar-free self-forming roadway floor loss reduction roof balance water conservation mining according to claim 4 is characterized in that: The back-end filling of the goaf in step S4 includes: using a grouting support to inject gangue and fly ash into the goaf after the coal seam is mined, and the filling volume is As shown below: in, represents the mining volume, Indicates the volume of rock collapse and expansion.

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