AU2020100234A4 - Method for water conservation mining by filling flexible strip - Google Patents

Method for water conservation mining by filling flexible strip Download PDF

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AU2020100234A4
AU2020100234A4 AU2020100234A AU2020100234A AU2020100234A4 AU 2020100234 A4 AU2020100234 A4 AU 2020100234A4 AU 2020100234 A AU2020100234 A AU 2020100234A AU 2020100234 A AU2020100234 A AU 2020100234A AU 2020100234 A4 AU2020100234 A4 AU 2020100234A4
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backfilling
mining
strip
gap
ratio
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AU2020100234A
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Jie Chen
Qingxiang HUANG
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Xian University of Science and Technology
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Xian University of Science and Technology
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    • E—FIXED CONSTRUCTIONS
    • E21—EARTH DRILLING; MINING
    • E21F—SAFETY DEVICES, TRANSPORT, FILLING-UP, RESCUE, VENTILATION, OR DRAINING IN OR OF MINES OR TUNNELS
    • E21F15/00—Methods or devices for placing filling-up materials in underground workings
    • E21F15/08—Filling-up hydraulically or pneumatically
    • C—CHEMISTRY; METALLURGY
    • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
    • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
    • C04B14/00—Use of inorganic materials as fillers, e.g. pigments, for mortars, concrete or artificial stone; Treatment of inorganic materials specially adapted to enhance their filling properties in mortars, concrete or artificial stone
    • C04B14/02—Granular materials, e.g. microballoons
    • C04B14/04—Silica-rich materials; Silicates
    • C04B14/06—Quartz; Sand
    • C04B14/068—Specific natural sands, e.g. sea -, beach -, dune - or desert sand
    • C—CHEMISTRY; METALLURGY
    • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
    • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
    • C04B18/00—Use of agglomerated or waste materials or refuse as fillers for mortars, concrete or artificial stone; Treatment of agglomerated or waste materials or refuse, specially adapted to enhance their filling properties in mortars, concrete or artificial stone
    • C04B18/04—Waste materials; Refuse
    • C04B18/06—Combustion residues, e.g. purification products of smoke, fumes or exhaust gases
    • C04B18/08—Flue dust, i.e. fly ash
    • C—CHEMISTRY; METALLURGY
    • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
    • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
    • C04B28/00—Compositions of mortars, concrete or artificial stone, containing inorganic binders or the reaction product of an inorganic and an organic binder, e.g. polycarboxylate cements
    • C04B28/02—Compositions of mortars, concrete or artificial stone, containing inorganic binders or the reaction product of an inorganic and an organic binder, e.g. polycarboxylate cements containing hydraulic cements other than calcium sulfates
    • C04B28/04—Portland cements
    • E—FIXED CONSTRUCTIONS
    • E21—EARTH DRILLING; MINING
    • E21F—SAFETY DEVICES, TRANSPORT, FILLING-UP, RESCUE, VENTILATION, OR DRAINING IN OR OF MINES OR TUNNELS
    • E21F15/00—Methods or devices for placing filling-up materials in underground workings
    • E21F15/005—Methods or devices for placing filling-up materials in underground workings characterised by the kind or composition of the backfilling material
    • C—CHEMISTRY; METALLURGY
    • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
    • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
    • C04B2111/00—Mortars, concrete or artificial stone or mixtures to prepare them, characterised by specific function, property or use
    • C04B2111/00017—Aspects relating to the protection of the environment
    • E—FIXED CONSTRUCTIONS
    • E21—EARTH DRILLING; MINING
    • E21C—MINING OR QUARRYING
    • E21C41/00—Methods of underground or surface mining; Layouts therefor
    • E21C41/16—Methods of underground mining; Layouts therefor
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02W—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO WASTEWATER TREATMENT OR WASTE MANAGEMENT
    • Y02W30/00—Technologies for solid waste management
    • Y02W30/50—Reuse, recycling or recovery technologies
    • Y02W30/91—Use of waste materials as fillers for mortars or concrete

Abstract

Abstract The present invention discloses a method for water conservation mining by filling a flexible strip, including the following steps: discrimination of a special water conservation mining area: through the analysis and calculation of conditions of coal seam occurrence, determining whether a mining area belongs to a special water conservation mining area; preparation of a flexible backfilling material: a paste backfilling material including, by mass percentage, 70% of aeolian sand, 6% of cement, 7.7% of fly ash, 0.3% of additive and 16% of water, where a flexible backfilling strip allows a compression ratio of 7-10%; pumping of the backfilling material: sequentially conveying the paste backfilling material prepared on the ground to a drilling pipe, a mining area where a filling working face is located, and a working face filling point through a pumping system; determining of a gap backfilling ratio and an aspect ratio parameter of the backfilling strip: determining the gap backfilling ratio according to stability conditions of an aquiclude, and determining the aspect ratio parameter of the backfilling strip according to medium and long-term stability conditions of the backfilling strip. The present invention has small filling amount and low cost, and has the advantages of high recovery rate and no threat of wide-range roof caving. Aeolian sand Cement Additive Fly ash Water bulk vehicle bulk vehicle bulk vehicle bulk vehicle Cylindrical barn Cylindrical barn Pool Cylindrical barn Cylindrical barn Feeder Feeder Water pump Water pump Feeder Feeder Weighing hopper Weighing hopper Wegig hopper Weighing hopper Weighing hopper] Weighing hopper Mixer Mixer Slrybucket Filling pump Filling pump Groundpipe Drilling pipe Downhole pipe Working face pipe Three-way pipevalve Backfilling point

Description

METHOD FOR WATER CONSERVATION MINING BY FILLING FLEXIBLE STRIP (51) International Patent Classification(s)
E21F 15/00 (2006.01) C04B 28/04 (2006.01)
C04B 14/06 (2006.01) E21C 41/16 (2006.01)
C04B 18/08 (2006.01) E21F 15/08 (2006.01) (21) Application No: 2020100234 (22) Date of Filing: 2020.02.18 (45) Publication Date: 2020.03.26 (45) Publication Journal Date: 2020.03.26 (45) Granted Journal Date: 2020.03.26 (71) Applicant(s)
XI'AN UNIVERSITY OF SCIENCE AND TECHNOLOGY (72) Inventor(s)
HUANG, Qingxiang;CHEN, Jie (74) Agent / Attorney
Michael Buck IP, PO Box 78, Red Hill, OLD, 4059, AU
Abstract
2020100234 18 Feb 2020
The present invention discloses a method for water conservation mining by filling a flexible strip, including the following steps: discrimination of a special water conservation mining area: through the analysis and calculation of conditions of coal seam occurrence, determining whether a mining area belongs to a special water conservation mining area; preparation of a flexible backfilling material: a paste backfilling material including, by mass percentage, 70% of aeolian sand, 6% of cement, 7.7% of fly ash, 0.3% of additive and 16% of water, where a flexible backfilling strip allows a compression ratio of 7-10%; pumping of the backfilling material: sequentially conveying the paste backfilling material prepared on the ground to a drilling pipe, a mining area where a filling working face is located, and a working face filling point through a pumping system; determining of a gap backfilling ratio and an aspect ratio parameter of the backfilling strip: determining the gap backfilling ratio according to stability conditions of an aquiclude, and determining the aspect ratio parameter of the backfilling strip according to medium and long-term stability conditions of the backfilling strip. The present invention has small filling amount and low cost, and has the advantages of high recovery rate and no threat of wide-range roof caving.
3/3
2020100234 18 Feb 2020
Figure AU2020100234A4_D0001
FIG. 5
METHOD FOR WATER CONSERVATION MINING BY FILLING FLEXIBLE STRIP
TECHNICAL FIELD
The present invention relates to the field of water conservation mining methods, and in particular to a method for water conservation mining by filling a flexible strip.
BACKGROUD
Northern Shaanxi is located in the arid area of the northwestern inland of China, and at the border of the Mu Us Desert and the Loess Plateau in northern Shaanxi. The water resources are scarce and the ecological environment is fragile. The area is rich in coal reserves, excellent in coal quality, simple in geological structure, and superior in mining technology. With the large-scale development of the mining area, mining-induced fractures directly lead to the loss of phreatic water of an aquifer, resulting in the drying up of wellspring, rivers and reservoirs that originally received the aquifer recharge.
Overlying strata of a coal seam in the Jurassic coalfield in northern Shaanxi mainly include a bedrock layer, a weathered layer, a soil layer and a sand layer from bottom to top. The sand layer includes aeolian sand and sarawusu formation, the thickness is generally within 10 m, and the bottom contains phreatic water with a water level of 0.9-9.27 m, which is a main aquifer; the soil layer refers to lishi loess and hipparion red soil, generally has a thickness of 10-40 m, and is a good aquiclude; the weathered layer refers to a bedrock top weathering zone, generally has a thickness of 20-25 m, and is a weak aquifer; the bedrock layer is unweathered bedrock covering a primary mineable coal bed, is mainly composed of sandstone, has a large thickness variation, generally has a thickness of 30-380 m, and together with the soil layer constitutes a water-resisting rock group.
In northern Shaanxi, the key to water conservation mining is to ensure the stability of the aquiclude, that is, the upward fracture and the downward fracture generated after the mining are not communicated with the aquiclude, as shown in FIGs. 1-2. According to indexes such as the developmental heights of downward fractures and upward fractures, a mining height and a bedrock thickness, with the stability of the water-resisting rock group as a control target, with reference to an engineering empirical formula, the mining in the northern Shaanxi is divided into three categories:
The first category: natural water conservation mining category. A long-wall full-seam mining method is adopted. After the mining, a water-resisting rock group is in a continuous bending zone after mining, the water-resisting performance of the effective water-resisting rock group is stable, and natural water conservation mining can be achieved.
i
The second category: special water conservation mining class. The effective water-resisting rock group is located in a caving zone or a fractured zone after mining, the mining will cause complete destruction of the water-resisting rock group, and a special mining mode such as backfilling mining must be adopted to achieve water conservation mining.
The third category: controllable water conservation mining class. After coordinated mining or height-limiting slicing mining, the development heights of the upward fractures and downward fractures can be reduced, so that the fractures do not pass through the water-resisting rock group and water conservation mining is achieved.
Due to the typical characteristics of shallow coal seam occurrence, thin bedrock and a thick loose bed in the Jurassic coalfields in northern Shaanxi, the stability of the aquifer is easily destroyed after mining, thereby leading to the loss of phreatic water of the aquifer. The phreatic water in the aquifer is water that surface vegetation and human beings depend on for survival and living. This makes the ecological environment in northern Shaanxi even worse. Therefore, it is necessary to use water conservation mining in northern Shaanxi.
Theoretically, the study on the stability of shallow coal seam overlying strata and water-resisting rock strata in China does not take into account the importance of “flexibility” of the water-resisting rock group containing a clay layer for the reduction of the control cost. The study on the stability of the water-resisting rock group is still limited to the conventional research mode of a water flowing fracture zone, mainly focusing on the study of the upward fractures of the fracture zone, ignoring the downward fractures of a tensile zone at the edge of a subsidence basin.
Technically, a domestic strip filling technology mainly uses a hard rock layer as a key layer of a framework, and the backfilling strip is basically designed according to a rigid strip, and the ground surface subsidence is mainly considered in the criterion. In addition, the previous strip mining is at the expense of coal resources, and the threat of extensive roof caving exists, which is not desirable for large-scale mining in northern Shaanxi.
SUMMARY
In order to solve the technical problems of coal development of a special water conservation mining area which mainly includes the Shenfu mining area in northern Shaanxi and the Dongsheng mining area in Inner Mongolia, the present invention provides a method for water conservation mining by filling a flexible strip, which adopts a sand-based backfilling material with lower strength and low cost and allows a backfilling strip to have a certain compression amount.
To achieve the above objective, the technical solution adopted by the present invention is:
A method for water conservation mining by filling a flexible strip, including the following steps:
step SI of discrimination of a special water conservation mining area: through the empirical analysis and calculation of conditions of coal seam occurrence, determining whether a mining area belongs to a special water conservation mining area;
step S2 of preparation of a flexible backfilling material, where a paste backfilling material includes, by mass percentage,
70% of aeolian sand, 6% of cement, 7.7% of fly ash, 0.3% of additive and 16% of water; and the flexible backfilling strip formed by the backfilling material allows a compression ratio of 7-10%, which reduces the material cost;
step S3 of pumping of the backfilling material: sequentially conveying the paste backfilling material prepared on the ground to a drilling pipe, a mining area where a filling working face is located, and a working face filling point through a pumping system;
step S4 of determining of a gap backfilling ratio and an aspect ratio parameter of the backfilling strip:
step S41: after the parameters of the mining height, the compression ratio (amount) of the backfilling strip, the elastic modulus of a backfilling body and a gap between backfill and a roof are determined, calculating the gap backfilling ratio K of a filling working face according to the following formula (the ratio of a filling gap width to a backfilling strip width):
K_(Wf-^Ef i (M-A)yH where K is a gap backfilling ratio; M is a mining height, m; Δ is a gap between backfill and a roof (a difference between the mining height and a backfilling height), m; H is a mining depth, m; γ is an overlying strata volume weight, MN/m3; JFf is a compression amount of the backfilling strip, m; and Ef is an elastic modulus of a backfilling body (measured by test), MPa;
step S42: according to a critical cubic uniaxial compressive strength test of an on-site backfilling body, in view of a safety factor of 2.0 times, determining a long-term stable uniaxial compressive strength 5C of the backfilling body on site;
according to an ultimate strength theory of the backfilling body, obtaining a formula for calculating an aspect ratio of the backfilling strip:
Z>J2O(1 + W/_17
V is, where L is an aspect ratio of the backfilling strip; K is a gap backfilling ratio; // is a mining height, m; and γ is an overlying strata volume weight, MN/m3;
substituting the gap backfilling ratio K obtained in the step S42 into the formula of the step S42, and calculating a minimum aspect ratio L which satisfies the long-term stability in the backfilling strip under the material strength; where in the calculation, the uniaxial compressive strength <)c of the backfilling body takes the 28d strength of the backfilling body; the 28d strength of the backfilling material obtained in this technology has a strength of 2 MPa;
step S5 of filling of a recovering working face:
adopting a double-strip equal-gap filling mining mode to cooperate with a long-wall mining system; where when the working face is backfilled, the filling should be performed strictly in accordance with the determined gap backfilling ratio and the aspect ratio of the backfilling strip.
For the backfilling material conveyed to the working face, a strip filling bracket with the patent number CN203756229U is used to fill a strip in a goaf, and the bracket can simultaneously satisfy functions of supporting, backfilling and auxiliary isolation.
The conditions for determining whether a mining area belongs to a special water conservation mining area in the step SI are:
Hr<h + 3M + h. = 18M + 3M + 2M = 23M
G u a where Hg is a thickness of an overlying strata water-resisting rock group of a working face, h h m; is an upward fracture development height which is 18 times the mining height, m; d is a downward fracture depth which is twice the mining height, m; and M is the mining height, m.
The particle size of the aeolian sand in the step S2 is 0-25 mm, and the mud content does not exceed 8%; the cement is 32.5# ordinary Portland cement; and the particle size of the fly ash is 0-25 mm.
An HGBS (S valve type) series industrial filling pump is used in the step S5. In use, an adaptive filling pump should be selected according to a downhole filling amount.
It is detected that the properties of the flexible backfilling material of the present invention are as follows: slump: 21.5-25 cm; compressive strength: 0.28 MPa (8 h strength), 2 MPa (28 d strength); bleeding rate: 4% (stationary bleeding rate), 29% (pressure bleeding rate); the prepared backfilling material has good performance and can meet the filling requirements.
The present invention has the following beneficial effects:
Whether a key layer is broken is no longer considered, and the stability of an aquiclude is controlled by controlling the development height of the fracture zone; aeolian sand widely distributed in northern Shaanxi is used as a main material of a backfilling material, and strip filling is performed for a goaf, and water conservation mining is achieved by controlling the stability of a water-resisting rock group; an overlying strata aquiclude and a backfilling strip are allowed to have a certain sinking amount and compression amount, but mining fractures are not allowed to pass through the water-resisting rock group, and thus the method is called “METHOD FOR WATER CONSERVATION MINING BY BACKFILLING FLEXIBLE STRIP”, so that the method has the advantages of small filling amount and low cost compared with original strip backfilling and full-backfilling mining, and the method has the advantages of high recovery rate and no threat of large-range roof caving compared with original strip mining.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a schematic diagram showing that an upward fracture zone and a downward fracture zone of mining overlying strata do not pass through an aquiclude;
FIG. 2 is a schematic diagram showing that an upward fracture zone and a downward fracture zone of mining overlying strata pass through an aquiclude;
Fig. 3 is a diagram showing a mode of double-strip long-wall strip backfilling mining along a trend according to an embodiment of the present invention;
FIG. 4 is a cross-sectional diagram of a goaf using double-strip backfilling along a trend according to an embodiment of the present invention; and
FIG. 5 is a flow chart of a process for flexible strip backfilling according to an embodiment of the present invention.
DESCRIPTION OF THE EMBODIMENTS
In order to make the objectives and advantages of the present invention clearer and more comprehensible, the present invention will be further described in detail below with reference to the embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the present invention and are not intended to limit the present invention.
Embodiment
Special water conservation mining areas in Shenfu mining area in northern Shaanxi and the Dongsheng mining area in Inner Mongolia are mainly mined by using a long-wall coal mining method, so this specific implementation mainly relies on a production system using a long-wall coal mining method to achieve water conservation mining by flexible strip backfilling. As shown in FIG. 3, a backfilling mining system (a system for mining by long-wall double-strip equal-gap filling along a trend) is presented. The system includes both an asymmetric supporting system of “coal pillars-backfilling strips” and a symmetric supporting system of “backfilling strips - backfilling strips”, as shown in FIG 4.
A filling system of this specific implementation mainly includes a backfilling material preparation system, a pumping system and a backfilling system. Firstly, in a ground slurry preparation station, according to the proportion of the present invention, backfilling material components are mixed to prepare a paste backfilling material, and then the paste backfilling material is conveyed through the ground via a pipeline to a downhole backfilling working face, and a closed strip space formed by isolation measures is backfilled with paste through a packed hydraulic support, thereby achieving strip backfilling. The whole filling process is as shown in FIG. 5.
A specific implementation method of the specific implementation:
Step S1 of discrimination of a special water conservation mining area.
Through the empirical analysis and calculation of conditions of coal seam occurrence, whether a mining area belongs to a special water conservation mining area is determined. If it is determined that the mining area belongs to a special water conservation mining area, then the purpose of water conservation mining can be achieved by applying this specific implementation.
According to engineering experience, in the northern Shaanxi area, for a moderately stable h bedrock roof, a development height of an upward fracture thereof is generally 18 times h higher than or equal to a mining height, and a downward fracture d thereof is generally twice the mining height. Taking into account the safe thickness of 3M (M mining height), the total thickness Hg of a water-resisting rock group (bedrock and a clay aquiclude) that can achieve water conservation mining is:
HG<hu+3M + hd = 23M
Such an area is called a special water conservation mining area, and a special mining mode such as strip filling must be adopted to achieve water conservation mining.
Step S2 of preparation of a flexible backfilling material.
The backfilling material adopted by this specific implementation is mainly composed of aeolian sand, cement, fly ash, additive, water, and the like, which are widely present on the earth surface of northern Shaanxi. The formula of the material by mass (total mass being 100%): 70% of aeolian sand, 6% of cement, 7.7% of fly ash, 0.3% of additive, and 16% of water.
The prepared material allows a compression ratio of 10% to reduce material cost.
The requirements for quality of component materials are:
aeolian sand: the particle size is 0-25 mm, and the mud content does not exceed 8%; cement: 32.5# ordinary Portland cement; and fly ash: the particle size is 0-25 mm.
Step S3 of pumping of a backfilling material
A route of sequentially conveying the paste backfilling material prepared on the ground
2020100234 18 Feb 2020 through a pumping system is: a ground slurry preparation station - a drilling pipe, a mining area where a backfilling working face is located, and a working face filling point, as shown in FIG. 5. An HGBS (S valve type) series industrial backfilling pump is used in this specific implementation. In use, an adaptive filling pump should be selected according to a downhole filling amount.
Step S4 of determining of a gap backfilling ratio and an aspect ratio parameter of the backfilling strip.
Based on the optimization principle of the backfilling effect with reference to the characteristics of a coal mining process in shallow coal seam in a special water conservation mining area in northern Shaanxi, it is recommended that the working face width in the water conservation mining area be designed to be 250-300 m.
(1) Determining of a gap backfilling ratio:
This specific implementation is flexible strip backfilling, which allows the backfilling strip to have a certain compression amount. In practical engineering applications, the compression ratio should generally be controlled at 7-10%. According to the stability of an overlying strata aquiclude, an allowable compression amount JFf of the backfilling strip is determined, and then the gap backfilling ratio is determined according to the following formula:
K_(Wf-A)Ef i (Μ-Α)γΗ (1) where K is a gap backfilling ratio; M is a mining height, m; Δ is a gap between backfilling body and a roof (a difference between the mining height and a backfilling height), m; H is a mining depth, m; γ is an overlying strata volume weight, MN/m3; JFf is a compression amount of the backfilling strip, m; and Ej is an elastic modulus of a backfilling body (measured by test), MPa.
After the parameters of the mining height, the compression ratio (amount) of the backfilling strip, the elastic modulus of a backfilling body and a gap between backfill and a roof are determined, the gap backfilling ratio K of a filling working face can be calculated.
(2) Determining of an aspect ratio:
According to a critical cubic uniaxial compressive strength test of an on-site backfilling body, in view of a safety factor of 2.0 times, a long-term stable uniaxial compressive strength 5C of the backfilling body is determined on site. According to an ultimate strength theory of the backfilling body, a formula for calculating an aspect ratio of the backfilling strip is obtained:
Λ > J20*1 + ^-..7
V (2) where L is an aspect ratio of the backfilling strip; K is a gap backfilling ratio; H is a mining height, m; and γ is an overlying strata volume weight, MN/m3.
The gap backfilling ratio K obtained in the calculation formula (1) is substituted into the calculation formula (2), and a minimum aspect ratio L which satisfies the long-term stability under the material strength can be calculated, where in the calculation, the uniaxial compressive strength <)c of the backfilling body takes the 28d strength of the backfilling body, and the 28d strength of the backfilling material obtained in this specific embodiment has a strength of 2 MPa.
According to the actual experience on site, the gap backfilling ratio is 3.5-6.0, and the aspect ratio is 2.5-5. For example, take the typical occurrence conditions of a special water conservation mining area in northern Shaanxi as an example: the buried depth is 72 m, the thickness of the clay layer is 12 m, the mining height is 4 m, the working face length is 250 m, the average volume weight of overlying strata is 24 kN/m3, the calculated gap backfilling ratio is 4.235, and the aspect ratio is 4.25, that is, when the mining height is 4 m, the flexible backfilling strip has a width of 17 m and a filling gap width of 72 m.
Step S5 of filling of a recovering working face.
A double-strip equal-gap backfilling mining mode is adopted in this specific implementation to cooperate with a long-wall mining system. For the paste backfilling material conveyed to the working face, a strip filling bracket with the patent number CN203756229U is selected for backfilling, and the bracket can simultaneously satisfy functions of supporting, filling and auxiliary isolation. When the working face is backfilled, the backfilling should be performed strictly in accordance with the determined gap backfilling ratio and the aspect ratio of the backfilling strip.
The foregoing descriptions are only preferred implementation manners of the present invention. It should be noted that for a person of ordinary skill in the art, several improvements and modifications may further be made without departing from the principle of the present invention. These improvements and modifications should also be deemed as falling within the protection scope of the present invention.

Claims (5)

  1. WHAT IS CLAIMED IS:
    1. A method for water conservation mining by filling a flexible strip, comprising the following steps:
    step SI of discrimination of a special water conservation mining area: through the analysis and calculation of conditions of coal seam occurrence, determining whether a mining area belongs to a special water conservation mining area;
    step S2 of preparation of a flexible backfilling material: a backfilling material comprising, by mass percentage,
    70% of aeolian sand, 6% of cement, 7.7% of fly ash, 0.3% of additive, and 16% of water;
    step S3 of pumping of the backfilling material: sequentially conveying the paste backfilling material prepared on the ground to a drilling pipe, a mining area where a backfilling working face is located, and a working face backfilling point through a pumping system;
    step S4 of determining of a gap backfilling ratio and an aspect ratio parameter of the backfilling strip:
    step S41: according to the stability of the aquiclude, obtaining a calculation formula of the gap backfilling ratio:
    K_(Wf-N)Ef i (Μ-Ν)γΗ wherein K is a gap backfilling ratio; AT is a mining height, m; Δ is a gap between backfill and a roof (a difference between the mining height and a backfilling height), m; H is a mining depth, m; γ is an overlying strata volume weight, MN/m3; JFf is a compression amount of the backfilling strip, m; Ef is an elastic modulus of a backfilling body (measured by test), MPa;
    after the parameters of the mining height, the compression amount of the backfilling strip, the elastic modulus of the backfilling body and the gap between backfill and a roof are determined, the gap backfilling ratio K of a backfilling working face can be calculated according to the foregoing formula;
    step S42: according to a critical cubic uniaxial compressive strength test of an on-site backfilling body, in view of a safety factor of 2.0 times, determining a long-term stable uniaxial compressive strength 5C of the backfilling body on site; according to an ultimate strength theory of the backfilling body, obtaining a formula for calculating an aspect ratio of the backfilling strip:
    Λ> |20(l + ^_
    1 3/· wherein L is an aspect ratio of the backfilling strip; K is a gap backfilling ratio; H is a
    2020100234 18 Feb 2020 mining height, m; and γ is an overlying strata volume weight, MN/m3;
    substituting the gap backfilling ratio K obtained in the step S41 into the formula of the step S42, and calculating a minimum aspect ratio L which satisfies the long-term stability in the backfilling strip;
    step S43: determining a backfilling strip width and a backfilling gap width;
    substituting the minimum aspect ratio L obtained in the step S42 into the following formula to calculate the backfilling strip width:
    Bc = LM wherein Bc is a backfilling strip width, m; L is an aspect ratio of the backfilling strip; and M is a mining height, m;
    substituting the gap backfilling ratio K obtained in the step S41 into the following formula to calculate the filling gap width:
    Bg = KBc wherein Bg is a filling gap width, m; Bc is a backfilling strip width, m; and K is a gap backfilling ratio;
    step S5 of filling of a recovering working face:
    adopting a double-strip equal-gap backfilling mining mode to cooperate with a long-wall mining system; when the working face is backfilled, the backfilling should be performed strictly in accordance with the determined gap backfilling ratio and the aspect ratio of the backfilling strip.
  2. 2. The method for water conservation mining by filling a flexible strip according to claim 1, wherein conditions for determining whether a mining area belongs to a special water conservation mining area in the step SI are:
    when the thickness Hg of an overlying strata water-resisting rock group of the working face h is less than the sum of an upward fracture development height , a downward fracture height h d and a safety belt thickness which is 3 times the mining height, the mining will cause complete destruction of the water-resisting rock group, such an area is called a special water conservation mining area, and a special mining mode such as strip backfilling must be adopted to achieve water conservation mining; that is, conditions for determining the special water conservation mining area are:
    Hr<h + 3M + h,=18M + 3M + 2M = 23M (_r u a wherein Hg is a thickness of an overlying strata water-resisting rock group of a working h face, m; is an upward fracture development height which is 18 times the mining height, m;
    io
    2020100234 18 Feb 2020 d is a downward fracture depth which is twice the mining height, m; and M is the mining height, m.
  3. 3. The method for water conservation mining by backfilling a flexible strip according to claim 1, wherein the particle size of the aeolian sand in the step S2 is 0-25 mm, and the mud content does not exceed 8%; the cement is 32.5# ordinary Portland cement; and the particle size of the fly ash is 0-25 mm.
  4. 4. The method for water conservation mining by backfilling a flexible strip according to claim 1, wherein in the determining of two key parameters for strip backfilling and mining in the step S4: a gap backfilling ratio and an aspect ratio of a backfilling strip, a formula for calculating a gap backfilling ratio of the backfilling strip (the ratio of a backfilling gap width to a backfilling strip width):
    K 1 (Μ-Δ)γΗ wherein K is a gap backfilling ratio; M is a mining height, m; Δ is a gap between backfilling body and a roof (a difference between the mining height and a backfilling height), m; H is a mining depth, m; γ is an overlying strata volume weight, MN/m3; JFf is a compression amount of the backfilling strip, m; Ef is an elastic modulus of a backfilling body (measured by test), MPa;
    a formula for calculating an aspect ratio of the backfilling strip is:
    ΐ 3<Z wherein L is an aspect ratio of the backfilling strip; K is a gap backfilling ratio; H is a mining height, m; and γ is an overlying strata volume weight, MN/m3.
  5. 5. The method for water conservation mining by backfilling a flexible strip according to claim 1, wherein a double-strip equal-gap backfilling mining mode is adopted in the step S5 to cooperate with a long-wall mining system.
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CN113387665A (en) * 2021-07-07 2021-09-14 河南绿岩工程科技有限公司 Liquefied consolidation material and preparation method thereof
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WO2023213045A1 (en) * 2022-05-06 2023-11-09 河南理工大学 Mining-induced high-level fractured space grouting repair method
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