CN115126506A - Grouting transformation method for protecting coal pillar of fourth aquifer of liberation shallow part - Google Patents
Grouting transformation method for protecting coal pillar of fourth aquifer of liberation shallow part Download PDFInfo
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Abstract
The invention provides a grouting transformation method for a fourth aquifer protection coal pillar of a liberation shallow part, wherein an overlying loose layer is arranged above the fourth aquifer, the fourth aquifer directly covers a bedrock layer, the protection coal pillar is positioned in the bedrock layer, and the grouting transformation method comprises the following steps: s1, determining the range of the protective coal pillar; s2, drilling to core, and determining the information of a fourth aquifer, an overlying unconsolidated formation and a bedrock formation; s3, performing the drilling water pressing test obtained in the S2 step; s4, performing grouting test on the drill hole obtained in the S2 step; s5, determining a grouting range, and arranging grouting holes in the grouting range; s6, dividing intervals of the grouting holes; s7, grouting; and S8, stopping grouting. The method can improve the upper limit of the exploitation of the water-retaining coal pillar and improve the recovery rate of coal on the premise of ensuring the safe production of a working face.
Description
Technical Field
The invention relates to the field of underground mining methods, in particular to a grouting transformation method for a fourth aquifer protection coal pillar of a liberation shallow part.
Background
The east mining area of China develops the coal series, and contains a large amount of high-quality coal resources, but the upper part of the coal series develops a loose aquifer, so the water-rich property is strong, the coal series is threatened by water damage of different degrees in the production process of mines, and most coal beds belong to deep mining and have large water pressure, so the water damage treatment before mining becomes the first problem of the safe production of the mines in the east area, and the water damage treatment method is also a technical problem in the safe production and scientific research of coal mines. In order to prevent the water damage of the water-bearing stratum at the upper part of the coal bed, a large amount of water-retaining coal pillars need to be reserved in the traditional coal mining to ensure the safe production of the working face. Therefore, a large amount of coal resources are left underground and cannot be recycled, and particularly high-quality coal resources cause huge waste of the coal resources. The loose layer waterproof coal rock pillar reserved in east China and North China only has over 50 hundred million tons, energy shortage is relieved, the maximum improvement of the recovery rate of coal resources becomes an urgent task of the current coal industry, and therefore the upper mining limit of a coal mine is improved, and coal pressing under water, buildings, railways and the like at the mining level of the upper portion of a mine is mined, so that the method has important significance for promoting coal production benefits, improving the recovery rate of the coal resources and relieving energy shortage.
As the mining resources of part of the eastern old mining areas are gradually reduced, until the later 80 s of the last century, many experts and scholars in the industry pay attention to the research of coal mining under middle and thick loose aquifers to improve the mining upper limit, thereby achieving the purpose of liberating the coal reserves as much as possible. Although partial water-retaining coal pillars are recovered in mining areas such as Huainan area, Huaibei area, Yanzhou area and the like, the range for improving the mining upper limit of the water-retaining coal pillars is limited, the recovery efficiency is low, the pressed coal under the water body accounts for about 25% of the total amount of the pressed coal under the water body, and the danger degree of water damage is high. At the present stage, the method mainly comprises the steps of coal mining method adjustment (such as layering, height limitation, strip and filling mining) and stoping and water retention coal pillars by the methods of plugging and grouting the top of the water guide crack belt in the stoping process. The adjustment of the coal mining method before mining still comes from the sacrifice of a large amount of coal resources, and the requirement of high-efficiency development of the coal resources is not met; in the stoping process, the plugging and grouting of the water-guiding fissure zone easily causes a large amount of slurry to flow into a goaf, so that the grouting amount is large and the plugging effect is poor.
In view of the fact that no effective, feasible and scientific liberation exploitation method for the exploitation aspect of the bottom protection coal pillar with four coal contents exists at present, in order to improve the recovery rate of coal resources under the four coal contents, relieve the shortage of coal energy in the eastern mining area, further improve the underwater coal mining method in the eastern and western mining areas in China and achieve the coal mining and water retention target, the safe, efficient and practical grouting reconstruction method for reconstructing the structure with four coal contents to liberate the fourth water-bearing layer protection coal pillar with the shallow part is urgent, and has very important significance and application prospect.
Disclosure of Invention
The invention aims to provide a grouting transformation method for protecting a coal pillar of a fourth aquifer at a liberation shallow part, aiming at a series of problems in the recovery of the water-retaining coal pillar of the fourth aquifer at present, aiming at overcoming the defects of the prior art, the method can improve the upper mining limit of the water-retaining coal pillar, improve the recovery rate of coal, protect water resources of a mining area and reasonably utilize industrial solid wastes, so that the grouting transformation method has great significance for the healthy and sustainable development of the coal industry in China and the construction of the ecological society on the premise of ensuring the safe production of a working face.
In order to achieve the above purpose, the invention provides the following technical scheme:
a grouting transformation method for a fourth aquifer protection coal pillar in a liberation shallow part, wherein an overlying loose layer is arranged above the fourth aquifer, the fourth aquifer directly covers a bedrock layer, the protection coal pillar is positioned in the bedrock layer, and the grouting transformation method comprises the following steps: s1, determining the range of the coal pillar; s2, drilling to core, and determining the information of a fourth aquifer, an overlying unconsolidated formation and a bedrock formation; s3, performing a water pressure test on the drill hole obtained in the step S2; s4, performing grouting test on the drill hole obtained in the S2 step; s5, determining a grouting range, and arranging grouting holes in the grouting range; s6, dividing intervals of the grouting holes; s7, grouting; and S8, stopping grouting.
Further, in the grouting transformation method for the fourth aquifer protection pillar at the liberation shallow part, in step S1, the protection pillar range is an area surrounded by the outer ends of the protection pillars after being connected, the protection pillar range is defined as F1, the cross section of the protection pillar range is a quadrangle, the ground positions corresponding to four vertexes of the quadrangle are a point a, a point b, a point c and a point d, and the ground position corresponding to a central point of the quadrangle is a point O; preferably, the cross section of the protection coal pillar range is rectangular.
Further, in the above-described grouting transformation method for protecting a coal pillar of a fourth aquifer of the liberation shallow part, in step S2, coring is performed at each of the point a, the point b, the point c, the point d, and the point O, and the information of the fourth aquifer includes a thickness and an initial water level pressure p 0 The information of the overburden loose layer comprises thickness, the information of the bedrock layer comprises thickness and bedrock top surface depth, and preferably, the drilling coring is pre-grouting coring, and the drilling coring is coring in a weathering zone at the upper part of the fourth aquifer and the bedrock layer.
Further, in the above grouting transformation method for the fourth aquifer protection pillar in the liberation shallow part, in the step S3, the water pressure test is a multi-stage water pressure test, and each stage of water pressure test is performedPressure of the test is p wi Pressure p of each stage of the water pressure test wi Are all greater than the initial water level pressure p of the fourth aquifer 0 Setting p to wi ＝1.2*p 0 、1.4*p 0 And 1.6. sup. p 0 (ii) a The pressure of a certain stage of water pressure test is p wi Measuring the water flow rate Q in a corresponding steady state wi And calculating and obtaining the water permeability of a certain test section in the depth range to be grouted in each drill hole under different water pressure through a formula (1):
wherein q is wi Water permeability, Lu; l is the length of a test section, m, and the test section is a section selected in the height direction of the drill hole; p is a radical of wi The pressure value is MPa of a pressurized water test; q wi The water flow is L/min of a pressurized water test;
and (3) calculating and obtaining the permeability coefficient of each test section in each drilling hole under different pressurized water pressures through a formula (2):
wherein, K wi Is the permeability coefficient, m/d; r is a radical of hydrogen 0 In order to be the radius of the drilled hole,
preferably, the fourth aquifer and the bedrock are evaluated for injectibility through the water permeability calculated by the water pressure test, and the specific evaluation method is as follows: water permeability q wi Above 5Lu, the rock mass has better injectivity; water permeability q wi When the content is between 1 and 5Lu, the injectability of the rock mass is general; water permeability q wi Below 1Lu, this indicates poor pourability of the rock mass.
Further, in the above-described method for reforming a coal pillar protected by a fourth aquifer in a shallow liberation area, in step S4, a slip-casting initiation pressure P is obtained from a slip-casting index 1 And pressure P of slurry channeling 2 Actual grouting pressure p si Between priming pressure P 1 And pressure P of slurry channeling 2 Setting x grades of the grouting pressure value of the grouting test, wherein x is preferably 5-10; grouting pressure value p of grouting test si Are all initial water level pressure p 0 Multiples of (d); preferably, the grouting pressure p si Sequentially comprises the following steps: p is a radical of 0 →1.2p 0 →1.4p 0 →1.6p 0 →1.8p 0 →2p 0 … …; recording grouting pressure value p si Corresponding actual slurry flow rate Q si ；
Calculating to obtain different grouting pressure values p of the grouting test through a formula (3) si The following slurry permeability:
wherein q is si For the rate of penetration, Lu; l is the length of the test segment, m; p is a radical of si The grouting pressure value is MPa in the grouting test; q si The actual slurry flow rate of the grouting test is L/min; preferably, the rate of pulp extraction q si Grouting pressure value p of more than 1Lu si As priming pressure P 1 Corresponding to an actual slurry flow rate of Q 1 Preferably, in the grouting test process, the grouting pressure value when adjacent holes are subjected to slurry channeling caused by grouting pressure at a certain stage is taken as the slurry channeling pressure P 2 Corresponding to an actual slurry flow rate of Q 2 。
Further, in the grouting transformation method for the fourth aquifer protection coal pillar at the liberation shallow part, in step S5, the grouting range is an area surrounded by the connection of the centers of the outermost grouting holes, the grouting range is defined as F2, the cross section of the grouting range is a quadrangle, the boundary of the grouting range F2 is outside the boundary of the protection coal pillar range F1, and the distance between the boundary of the grouting range F2 and the boundary of the protection coal pillar range F1 is 2 to 4 times the grouting diffusion radius R; preferably, the grouting holes include first-type grouting holes and second-type grouting holes, the first-type grouting holes are sequentially arranged to form a line, the second-type grouting holes are sequentially arranged to form another line, a line of the first-type grouting holes is arranged at the boundary of the grouting range F2, a line of the second-type grouting holes is arranged, a line of the first-type grouting holes is arranged until the center line of the grouting range F2, the first-type grouting holes and the second-type grouting holes are arranged in a mirror image manner until the boundary of the other side of the grouting range F2, the first-type grouting holes in the adjacent line are arranged in a staggered manner that the center of the first-type grouting holes in the adjacent line is 2 times the grouting diffusion radius R from the center of the second-type grouting holes in the other line, during construction, the first type of grouting holes are constructed first, then the second type of grouting holes are constructed, and preferably, the distance between the circle centers of two adjacent grouting holes in the same row is 2 times of the grouting diffusion radius R; preferably, the grouting hole is a ground straight hole or a directional inclined hole, preferably, the cross section of the grouting range is rectangular, and the ground position corresponding to the center point of the grouting range is a point O.
Further, in the grouting transformation method for protecting a coal pillar in a fourth aquifer of the liberation shallow part, in step S6, the grouting hole includes two open sections, namely a first open section and a second open section, the first open section starts from the ground surface and ends 5m below the top surface of the fourth aquifer, and the second open section starts from 5m below the top surface of the fourth aquifer and ends 10m below the top surface of the bedrock; the two-opening section is internally provided with N grouting sections, the length of each grouting section is 4-8 m, the N grouting sections are divided into three transformation sections, namely an upper transformation section, a middle transformation section and a lower transformation section, the upper transformation section starts from 5m below the top surface of the fourth aquifer to the bottom surface of the N/3 grouting section, the middle transformation section starts from the bottom surface of the N/3 grouting section to the bottom surface of the 2N/3 grouting section, and the lower transformation section starts from the bottom surface of the 2N/3 grouting section to the bottom surface of the N grouting section.
Further, in the above grouting transformation method for protecting a coal pillar in a fourth aquifer of the liberation shallow part, in step S7, the grouting treatment is performed on the second opened section by a segmented descending and orifice-closed static pressure grouting method; preferably, a grouting process combining continuous grouting and intermittent grouting is adopted in the grouting process;
during grouting, the two open sections are regarded as homogeneous strata, and different grouting pressure target values P are obtained 1 Or P 2 The following slurry diffusion radius R satisfies formula (3):
wherein R is the slurry diffusion radius m; k is the permeability coefficient of the soil layer to be injected and m/h, and is determined by an indoor test; t is the time required for slurry diffusion, h, and is determined by a grouting test; h is the grouting pressure and m expressed by the height of a water column, and is measured by a grouting test; r is 0 Is the radius of the grouting pipe, m; n is the effective porosity of the injected coal rock mass and is determined by an indoor test; mu.s w The viscosity of water, mPa & s; mu.s s0 The initial viscosity and mPa & s of the slurry; alpha is the time-varying coefficient of the slurry viscosity; a is an integral parameter related to a time-varying coefficient alpha of the slurry viscosity; e is a natural constant with a value of 2.71828.
Further, in the above grouting transformation method for protecting a coal pillar in a fourth aquifer at the liberation shallow part, in step S7, the grouting material is a mixed slurry of portland slag cement and fly ash, preferably, the amount of fly ash mixed in the grouting material in the upper transformation stage is 40% to 60% of the portland slag cement by mass ratio, the amount of fly ash mixed in the grouting material in the middle transformation stage is 20% to 40% of the portland slag cement by mass ratio, no fly ash mixed in the grouting material in the lower transformation stage is pure portland slag cement slurry grouting, preferably, a downward-type sealed static pressure grouting sleeve is used for grouting, the aperture of the first opening stage is 216mm, a Φ 177.8 × 8.05mm grouting sleeve is put in, cement is cemented, the aperture of the second opening stage is 152mm, preferably, the grouting holes at the outermost side of the grouting range F2 are grouted first, grouting other first-type grouting holes, and finally grouting second-type grouting holes; preferably, the other grouting holes except the outermost grouting hole of the grouting region F2, the middle reconstruction section and the lower reconstruction section are grouted by using a normal grouting pressure P, the grouting holes and the upper reconstruction section on the outermost side of the grouting range F2 reduce the final grouting pressure to be P- Δ P, the Δ P is 0.5-1.0MPa, and the diffusion range of the grout is controlled.
Further, in the above grouting transformation method for protecting a coal pillar in a fourth aquifer of the liberation shallow part, in step S8, the grouting stopping control is performed by using the dual criteria of the grouting final pressure and the grouting amount; preferably, the grouting final pressure is not lower than 1.5 times of the hydrostatic pressure of the tested section; and when the grouting pressure reaches the end standard, gradually shifting to reduce the pump amount until the pump amount reaches 60L/min, maintaining for 30min, then pressing water, wherein the unit water absorption rate is not more than 1Lu, and stopping grouting under the condition that the two standards are met.
The method fills the blank that no effective, feasible and scientific method for protecting the coal pillar of the fourth aquifer of the liberation shallow part exists at present, and can realize scientific design of grouting parameters, grouting materials and grouting sequence and division optimization of grouting intervals by drilling and coring in the range of the coal pillar of the fourth aquifer to determine the tectonic structural characteristics and the injectability index of the fourth aquifer, thereby having important theoretical significance for subsequently developing research on a coal pillar reservation method under the fourth aquifer and determining the mining upper limit of the coal pillar under the fourth aquifer.
Drawings
The accompanying drawings, which are incorporated in and constitute a part of this application, illustrate embodiments of the invention and, together with the description, serve to explain the invention and not to limit the invention. Wherein:
fig. 1 is a flowchart of a grouting transformation method according to an embodiment of the present invention.
Fig. 2 is a schematic diagram of an embodiment of the present invention.
Fig. 3 is a schematic diagram of grouting holes arranged in the grouting range according to an embodiment of the invention.
FIG. 4 is a schematic diagram of two open sections of a grouting hole according to an embodiment of the invention.
Fig. 5 is a schematic diagram of dividing N grouting sections according to an embodiment of the invention.
Description of reference numerals: 1, covering a loose layer; 2 a fourth aqueous layer; a 3-base rock stratum; 4, protecting the coal pillars; 5, a coal seam; 6, transforming the area; 8, modifying a leading water fracture zone; 9, transforming the water flowing fractured zone; 10 grouting holes of a first type; 11 a second type grouting hole; 12, opening a section; 13, opening a second section; 14 grouting section, 15 top of the fourth aquifer, 16 bottom of the fourth aquifer; f1 protection of coal pillar range; f2 slip range.
Detailed Description
The present invention will be described in detail below with reference to the embodiments with reference to the attached drawings. The various examples are provided by way of explanation of the invention, and not limitation of the invention. In fact, it will be apparent to those skilled in the art that modifications and variations can be made in the present invention without departing from the scope or spirit thereof. For instance, features illustrated or described as part of one embodiment, can be used with another embodiment to yield a still further embodiment. It is therefore intended that the present invention encompass such modifications and variations as fall within the scope of the appended claims and their equivalents.
In the description of the present invention, the terms "longitudinal", "lateral", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the drawings, which are for convenience of description of the present invention only and do not require that the present invention must be constructed and operated in a specific orientation, and thus, should not be construed as limiting the present invention. The terms "connected," "connected," and "disposed" as used herein are intended to be broadly construed, and may include, for example, fixed and removable connections; can be directly connected or indirectly connected through intermediate components; the connection may be a wired electrical connection, a wireless electrical connection, or a wireless communication signal connection, and a person skilled in the art can understand the specific meaning of the above terms according to specific situations.
One or more examples of the invention are illustrated in the accompanying drawings. The detailed description uses numerical and letter designations to refer to features in the drawings. Like or similar designations in the drawings and description have been used to refer to like or similar parts of the invention. As used herein, the terms "first," "second," and "third," etc. may be used interchangeably to distinguish one component from another, and are not intended to denote the position or importance of the individual components.
As shown in fig. 1 to 5, according to an embodiment of the present invention, there is provided a grouting transformation method for protecting a pillar 4 of a fourth aquifer 2 in a shallow part, wherein an overlying unconsolidated layer 1 is located above the fourth aquifer 2, the fourth aquifer 2 directly covers a bed layer 3, and the pillar 4 is located in the bed layer 3, the grouting transformation method including the steps of:
s1, determining the range of the coal pillar 4;
in the step S1, the range of the protective coal pillar 4 is an area surrounded by the outer ends of the protective coal pillar 4 after being connected, as shown in fig. 2 and 3, the range of the protective coal pillar 4 is defined as F1, the cross section of the range of the protective coal pillar 4 is a quadrangle, the ground positions corresponding to four vertexes of the quadrangle are a point a, a point b, a point c, and a point d, and the ground position corresponding to a central point of the quadrangle is a point O. Preferably, the cross section of the range of the protective coal pillar 4 is rectangular. The range of the protective coal pillar 4 is determined according to the existing 'specification of coal pillar setting and coal pressing mining for buildings, water bodies, railways and main roadways' (2017 edition) and the data of a working face of a mining area, for example, a vertical section method, a vertical line method, a digital elevation projection method, a deformation prediction method and the like can be adopted.
S2, drilling holes for coring, and determining information of a fourth aquifer 2, an overlying unconsolidated formation 1 and a bedrock formation 3;
in step S2, as shown in fig. 3, core drilling is performed at the point a, the point b, the point c, the point d, and the point O, respectively, and the information of the fourth aquifer 2 includes a thickness, an initial water level pressure p, and the like 0 ，
The information of the overburden loose layer 1 comprises thickness, the information of the bedrock layer 3 comprises thickness and bedrock top surface depth, and preferably, the drilling coring is pre-grouting coring and is performed in a weathering zone at the upper part of the fourth aquifer 2 and the bedrock layer 3. The bedrock layer 3 weathering zone is the uppermost part of the bedrock layer 3, and the uppermost part of the bedrock layer 3 is not completely diagenetic and belongs to the bedrock layer 3 weathering zone.
Determination of the fourth aquifer 2 thickness, initial water level pressure p by drilling coring 0 The thickness of overburden 1, the thickness of bedrock layer 3 and the depth of the bedrock top surface in preparation for the subsequent steps.
S3, performing a water pressure test on the drill hole obtained in the step S2;
in the step S3, a water pressure test is performed on the borehole obtained in the step S2 to obtain parameters such as the water pressure test pressure and the penetration amount, permeability characteristics of the fourth aquifer 2 and the bedrock layer 3 are determined by analysis, and a corresponding injectivity index is calculated to perform injectivity evaluation.
The water pressure test is a multi-stage water pressure test, and the pressure of each stage of water pressure test is p wi ，
Pressure p of each stage of water pressure test wi Are all greater than the initial water level pressure p of the fourth aquifer 2 0 Setting for p wi ＝1.2*p 0 、1.4*p 0 And 1.6. sup. p 0 ；
The pressure of a certain stage of pressurized water test is p wi Measuring the water flow rate Q in a corresponding steady state wi And calculating and obtaining the water permeability of a certain test section in the depth range to be grouted in each drill hole under different water pressure through a formula (1):
wherein q is wi Water permeability, Lu; l is the length of a test section, m, and the test section is a section selected in the height direction of the drill hole; p is a radical of wi The pressure value is MPa of a pressurized water test; q wi The water flow is L/min of a pressurized water test;
and (3) calculating and obtaining the permeability coefficient of each test section in each drilling hole under different pressurized water pressures through a formula (2):
wherein, K wi Is the permeability coefficient, m/d; r is a radical of hydrogen 0 In order to be the radius of the drilled hole,
preferably, the fourth aquifer 2 and the bedrock 3 are evaluated for injectibility by calculating the obtained water permeability through a water pressure test, and the specific evaluation method is as follows:
water permeability q wi Above 5Lu, it indicates that the fourth aquifer 2 and the basement 3 weathered zone have better injectivity;
water permeability q wi When the total content of the water in the fourth aquifer 2 is 1-5 Lu, the injectability of the weathered zone of the fourth aquifer 2 and the basement layer 3 is general;
water permeability q wi Less than 1Lu indicates poor injectivity of the fourth aquifer 2 and the basement 3 weathered zone.
The water-cement ratio and the grouting pressure of the slurry are adjusted according to the three different conditions, and when the grouting performance is good, the water-cement ratio is properly reduced; when the pourability is poor, the water-cement ratio is properly increased. The mixing amount of the fly ash is adjusted according to the three different types, and when the injectability is good, the mixing amount of the fly ash is properly increased; when the injectability is poor, the mixing amount of the fly ash is properly reduced.
S4, performing grouting test on the drill hole obtained in the S2 step;
in the step S4, a grouting test is performed on the drilled hole obtained in the step S2, a corresponding relation between the grouting test pressure and the grout penetration is obtained, and grout injectibility indexes of the fourth aquifer 2 and the basement rock layer 3 are determined through analysis, so as to obtain actual grouting engineering parameters. The injectability index is mainly obtained through the water pressing test in the step S3, and the injectability index is more accurate after being verified by matching with the grouting test. Meanwhile, according to the injectability evaluation obtained by the pressurized water test in the step S3, the grouting test can be optimized, if the pressurized water test shows that the injectability is poor, the first-stage grouting pressure of the grouting test needs to be increased, and the total grouting pressure level needs to be increased.
According to the slurry canObtaining the initial pressure P of grouting according to the grouting index 1 And pressure P of slurry channeling 2 Actual grouting pressure p si Between priming pressure P 1 And pressure P of slurry channeling 2 In the middle of the above-mentioned period,
setting x grades of grouting pressure values of the grouting test, wherein x is preferably 5-10; grouting pressure value p of grouting test si Are all initial water level pressure p 0 Multiple of (2);
preferably, the grouting pressure p si Sequentially comprises the following steps: p is a radical of formula 0 →1.2p 0 →1.4p 0 →1.6p 0 →1.8p 0 →2p 0 ……；
Recording grouting pressure value p si Corresponding actual slurry flow rate Q si ；
Calculating to obtain different grouting pressure values p of the grouting test through a formula (3) si The following slurry permeability:
wherein q is si For the starch penetration rate, Lu; l is the length of the test segment, m; p is a radical of si The grouting pressure value is MPa in the grouting test; q si The actual slurry flow rate of the grouting test is L/min;
preferably, the slurry taking rate q si Grouting pressure value p of more than 1Lu si As priming pressure P 1 Corresponding to an actual slurry flow rate of Q 1 ，
Preferably, in the grouting test process, the grouting pressure value when the adjacent holes have the slurry channeling caused by the grouting pressure of a certain stage is taken as the slurry channeling pressure P 2 Corresponding to an actual slurry flow rate of Q 2 。
S5, determining a grouting range, and arranging grouting holes in the grouting range;
in step S5, the grouting range is an area surrounded by the connected circle centers of the outermost grouting holes, and is defined as F2, as shown in fig. 3, the cross section of the grouting range may be a quadrangle,
the boundary of the grouting range F2 is outside the boundary of the protective pillar 4 range F1,
the distance between the boundary of the grouting range F2 and the boundary of the protective coal pillar 4 range F1 is 2-4 times of the grouting diffusion radius R;
preferably, the grout holes include a first type of grout holes 10 and a second type of grout holes 11,
a plurality of the first type grouting holes 10 are sequentially arranged to form a row, a plurality of the second type grouting holes 11 are sequentially arranged to form another row,
firstly, a row of the first type grouting holes 10 is arranged at one side boundary of the grouting range F2, then a row of the second type grouting holes 11 is arranged, then a row of the first type grouting holes 10 is arranged till the middle line position of the grouting range F2, and then the arrangement of the first type grouting holes 10 and the second type grouting holes 11 is mirrored till the other side boundary of the grouting range F2.
The first-type grouting holes 10 in the adjacent row are arranged in a staggered manner with respect to the second-type grouting holes 11 in the other row, as shown in fig. 3, and are arranged in rows in the transverse direction and columns in the longitudinal direction. Starting from the transverse boundary of the grouting range F2, a row of first-type grouting holes 10, a row of second-type grouting holes 11, and … … are arranged alternately in sequence to form the first-type grouting holes 10. Starting from the longitudinal boundary of the grouting range F2, a row of first-type grouting holes 10, a row of second-type grouting holes 11 and … … are sequentially arranged in a penetrating manner, and the last row is the first-type grouting hole 10. The grouting holes in the same row or the same column are the first-type grouting holes 10 or the second-type grouting holes 11, and the centers of the grouting holes in the same row or the same column are on the same straight line. The grouting device is beneficial to drilling construction, formation of a grouting curtain and guarantee of uniformity of grouting in a grouting range, and the adjacent grouting holes are fully utilized to realize air channeling pressure relief, so that grouting quantity is controlled, and grouting effect is guaranteed.
The distance between the circle centers of the first type grouting holes 10 in the adjacent row and the second type grouting holes 11 in the other row is 2 times of the grouting diffusion radius R, during construction, the first type grouting holes 10 are constructed first, and then the second type grouting holes 11 are constructed, preferably, the distance between the circle centers of two adjacent grouting holes in the same row is 2 times of the grouting diffusion radius R; preferably, the grouting hole is a ground straight hole or a directional inclined hole, preferably, the cross section of the grouting range is rectangular, and the ground position corresponding to the center point of the grouting range is a point O.
S6, dividing intervals of the grouting holes;
in step S6, as shown in fig. 4, the grouting hole includes two open sections, namely a first open section 12 and a second open section 13, wherein the first open section 12 starts from the ground surface and ends 5m below the top surface of the fourth aquifer 2, and the second open section 13 starts from 5m below the top surface of the fourth aquifer 2 and ends 10m below the top surface of the bedrock layer 3;
Dividing the N grouting sections 14 into three transformation sections, namely an upper transformation section, a middle transformation section and a lower transformation section, wherein N is preferably a multiple of 3, the upper transformation section starts from 5m below the top surface of the fourth aquifer 2 to the bottom surface of the N/3 grouting section 14,
the middle reforming section starts from the bottom surface of the N/3 grouting section 14 to the bottom surface of the 2 xN/3 grouting section 14,
the lower reforming section starts from the bottom surface of the 2 × N/3 grouting section 14 to the bottom surface of the N grouting section 14,
if N is not a multiple of 3 after dividing the grouting section 14 according to the actual formation (thickness of overlying unconsolidated formation 1), it can be adjusted appropriately, taking an integer. Assuming that N is 10, the upper 3 grouting sections 14 may be upper reconstruction sections, the middle 3 grouting sections 14 may be middle reconstruction sections, and the lower 4 grouting sections 14 may be lower reconstruction sections.
The division of the N grouting sections 14 into an upper reconstruction section, a middle reconstruction section and a lower reconstruction section provides for a subsequent grouting step.
S7, grouting;
in the step S7, in the above step,
grouting treatment is carried out on the grouting of the second opening section 13 by adopting a segmented descending and orifice-closed static pressure grouting method;
preferably, a continuous and intermittent grouting combined grouting process is adopted in the grouting process;
during grouting, the two open sections 13 are regarded as homogeneous strata, and target values P of different grouting pressures are obtained 1 Or P 2 The following slurry diffusion radius R satisfies formula (3):
wherein R is the slurry diffusion radius m; k is the permeability coefficient of the injected soil layer and m/h, and is measured by an indoor test; t is the time required for slurry diffusion, h, and is determined by a grouting test; h is the grouting pressure and m expressed by the height of a water column, and is measured by a grouting test; r is 0 Is the radius of the grouting pipe, m; n is the effective porosity of the injected coal rock mass and is determined by an indoor test; mu.s w The viscosity of water, mPa & s; mu.s s0 The initial viscosity and mPas of the slurry; alpha is the time-varying coefficient of the slurry viscosity; a is an integral parameter related to a time-varying coefficient alpha of the slurry viscosity; e is a natural constant with a value of 2.71828.
In the step S7, the grouting material is mixed slurry of slag portland cement and fly ash,
preferably, the mixing amount of the fly ash in the grouting material in the upper modification section is 40-60% of the slag portland cement,
the mixing amount of the fly ash in the grouting material in the middle reconstruction section is 20-40% of that of the slag portland cement according to the mass ratio,
according to the mass ratio, the grouting material in the lower reconstruction section is not doped with fly ash, pure slag silicate cement slurry is adopted for grouting,
along with the increase of the mixing amount of the fly ash, the stone rate of the slurry is improved, the setting time is increased, when the mixing amount of the fly ash is below 20-30%, the compressive strength of the stone body is slowly reduced along with the increase of the mixing amount, and when the mixing amount is more than 30%, the compressive strength of the stone body is obviously reduced; the larger the water-cement ratio is, the lower the calculus rate is, and the longer the setting time of the slurry is. The increase of the water of the stone body means the increase of the particle spacing of solid matters, and a skeleton structure is not easy to form.
Preferably, a descending sealing static pressure grouting sleeve is adopted for grouting,
the aperture of the first opening section 12 is phi 216mm, a phi 177.8 multiplied by 8.05mm grouting casing (steel grade J55) is put in the first opening section, cement is used for cementing, and the aperture of the second opening section 13 is phi 152 mm.
Preferably, the grouting holes at the outermost side of the grouting range F2 are grouted first, and the area of the grouting range F2 is subjected to 'lock seaming', so that ineffective diffusion is reduced. Grouting other first-class grouting holes 10 and finally grouting second-class grouting holes 11; preferably, the other grouting holes except the outermost grouting hole of the grouting region F2, the middle reconstruction section and the lower reconstruction section are grouted by using a normal grouting pressure P, the grouting holes and the upper reconstruction section on the outermost side of the grouting range F2 reduce the final grouting pressure to be P- Δ P, the Δ P is 0.5-1.0MPa, and the diffusion range of the grout is controlled.
The inner side slurry diffusion range of the outermost grouting holes of the grouting range F2 is restrained by the grouting slurry of the inner grouting holes, and the outer sides of the outermost grouting holes are not restrained; the stratum pressure of the upper transformation section is small, the porosity of the corresponding grouting layer is large, and the grouting performance is good. And the pressure reduction and stopping injection are adopted for the two parts, namely the injection hole at the outermost side of the injection range F2 and the upper modification section, so that the invalid diffusion of the slurry can be avoided, the use amount of the slurry is controlled, and the economic benefit is remarkable.
The aim of modifying the aquifer according to the grouting: the method comprises the steps of liberating a shallow part, namely a fourth aquifer 2 to protect a coal pillar 4, determining a second opening section 13 as a grouting section 14, grouting from 5m below the top surface of the fourth aquifer 2 to 10m below the top surface of a foundation layer 3, pressurizing and grouting to compact flowing sand in the fourth aquifer 2, squeezing away hole fracture water of the fourth aquifer 2, splitting and modifying the fourth aquifer 2, forming a skeleton structure in the fourth aquifer 2, reducing the water-rich property of the fourth aquifer 2 in a modification area 6 (as shown in figure 2, the modification area 6 is a three-dimensional space formed by a grouting range F2 on the plane and a second opening section 13 area on the vertical direction), changing the fourth aquifer 2 into an effective water-resisting layer or a class III water body close to the drainage, and liberating the shallow part, namely the fourth aquifer 2 to protect resources of the coal pillar 4. The reconstructed leading water fractured zone 8 and the reconstructed leading water fractured zone 9 are shown in fig. 2. After grouting transformation, the strength of the fourth water-bearing layer 2 is improved, the fourth water-bearing layer 2 can be exploited to protect the coal pillar 4, and the generated water-guiding fracture zone cannot affect the fourth water-bearing layer 2. Thereby avoiding the fourth aquifer 2 from bursting water and sand due to excavation influence to cause production accidents, and liberating coalable coal resources covered by the fourth aquifer 2.
S8, stopping grouting;
in the step S8, performing grouting stopping control by using the dual standards of grouting final pressure and grouting amount;
preferably, the grouting final pressure is not lower than 1.5 times of the hydrostatic pressure of the tested section; and when the grouting pressure reaches the end standard, gradually shifting to reduce the pump amount until the pump amount reaches 60L/min, maintaining for 30min, and then pressurizing water, wherein the unit water absorption rate is not more than 1Lu, otherwise, re-injecting is required until the unit water absorption rate is less than the standard value. Namely grouting until the unit water absorption rate is not more than 1Lu, otherwise, grouting is required to be continued. Only when the two standards are met simultaneously, the grouting section can be considered to reach the grouting ending standard, and grouting can be stopped.
Due to the particularity of the grouting engineering, the conditions that adjacent holes are connected in series and the ground is deformed and the like due to the grouting of a loose layer are considered, so that the grouting pressure can be adjusted according to the actual conditions on site, and the total pressure is not lower than 1.5 times of the hydrostatic pressure of the position to be grouted in principle.
The water guide fractured zone generated by the mining of the fourth aquifer protection coal pillar 4, namely the reconstructed front water guide fractured zone 8, can reach the fourth aquifer 2. For liberation shallow portion fourth aquifer protection coal pillar 4 is in order to improve the exploitation upper limit, carries out the slip casting transformation to fourth aquifer 2, and the water guide fracture area that produces when mining is carried out to the coal seam of fourth aquifer protection coal pillar 4 below again after the slip casting transformation promptly reforms water guide fracture area 9 and can not reach fourth aquifer 2.
From the above description, it can be seen that the above-described embodiments of the present invention achieve the following technical effects: the method fills the blank that no effective, feasible and scientific method for liberating the shallow part of the fourth aquifer 2 to protect the coal pillar 4 exists at present, the characteristics of the overlying strata structure and the injectibility index of the fourth aquifer 2 are determined through drilling and coring exploration in the range of the fourth aquifer to protect the coal pillar 4, the scientific design of grouting parameters, grouting materials and grouting sequence and the division optimization of grouting sections can be realized, and the method has important theoretical significance for the subsequent development of the method research for reserving the coal pillar under the fourth aquifer 2 and the determination of the mining upper limit of the coal pillar under the fourth aquifer 2.
The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention, and various modifications and changes may be made by those skilled in the art. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (10)
1. A grouting transformation method for a fourth water-bearing stratum protection coal pillar at a liberation shallow part is characterized in that an overlying loose layer is arranged above the fourth water-bearing stratum, the fourth water-bearing stratum is directly covered on a bedrock stratum, the protection coal pillar is positioned in the bedrock stratum,
the grouting transformation method comprises the following steps:
s1, determining the range of the coal pillar;
s2, drilling to core, and determining the information of a fourth aquifer, an overlying unconsolidated formation and a bedrock formation;
s3, performing a water pressure test on the drill hole obtained in the step S2;
s4, performing grouting test on the drill hole obtained in the S2 step;
s5, determining a grouting range, and arranging grouting holes in the grouting range;
s6, dividing intervals of the grouting holes;
s7, grouting;
and S8, stopping grouting.
2. The grouting transformation method of a fourth aquifer protection pillar of a liberation shallow as claimed in claim 1,
in the step S1, the protection pillar range is an area surrounded by the outer ends of the protection pillars after being connected, the protection pillar range is defined as F1, the cross section of the protection pillar range is a quadrangle, the ground positions corresponding to four vertexes of the quadrangle are a point a, a point b, a point c and a point d, and the ground position corresponding to the center point of the quadrangle is a point O;
preferably, the cross section of the protection coal pillar range is rectangular.
3. The grouting transformation method for the fourth aquifer protection coal pillar of the liberation shallow as claimed in claim 2,
in the step S2, coring is drilled at the point a, the point b, the point c, the point d, and the point O, respectively,
the information of the fourth aquifer comprises thickness and initial water level pressure p 0 ，
The information of the overlying bulk layer includes a thickness,
the information of the bedrock stratum comprises thickness and bedrock top surface depth,
preferably, the drilling coring is pre-grouting coring, and the drilling coring cores a weathering zone in an upper portion of the fourth aquifer and the bedrock formation.
4. The grouting transformation method of a fourth aquifer protection pillar of a liberation shallow as claimed in claim 3,
in the step S3, the water pressure test is a multi-stage water pressure test, and the pressure of each stage of water pressure test is p wi ，
Pressure p of each stage of water pressure test wi Are all greater than the initial water level pressure p of the fourth aquifer 0 Setting for p wi ＝1.2*p 0 、1.4*p 0 And 1.6. sup. p 0 ；
The pressure of a certain stage of water pressure test is p wi Measuring the water flow rate Q in a corresponding steady state wi And calculating and obtaining the water permeability of a certain test section in the depth range to be grouted in each drill hole under different water pressure through a formula (1):
wherein q is wi Water permeability, Lu; l is the length of a test section, m, and the test section is a section selected in the height direction of the drill hole; p is a radical of wi The pressure value is MPa of a pressurized water test; q wi The water flow is L/min of a pressurized water test;
and (3) calculating and obtaining the permeability coefficient of each test section in each drilling hole under different pressurized water pressures through a formula (2):
wherein, K wi Is the permeability coefficient, m/d; r is 0 In order to be the radius of the drilled hole,
preferably, the fourth aquifer and the bedrock are evaluated for injectibility through the water permeability calculated by the water pressure test, and the specific evaluation method is as follows:
water permeability q wi Above 5Lu, the rock mass has better injectivity;
water permeability q wi When the content is between 1 and 5Lu, the injectability of the rock mass is general;
water permeability q wi Below 1Lu, this indicates poor pourability of the rock mass.
5. The grouting transformation method for a fourth aquifer protection coal pillar of a liberation shallow as claimed in claim 1,
in the step S4, the slip casting starting pressure P is obtained according to the slip casting performance index 1 And pressure P of slurry channeling 2 Actual grouting pressure p si Between priming pressure P 1 And pressure P of slurry channeling 2 In the above-mentioned manner,
setting x grades of grouting pressure values of the grouting test, wherein x is preferably 5-10; grouting pressure value p of grouting test si Are all initial water level pressure p 0 Multiples of (d);
preferably, the grouting pressure p si Sequentially comprises the following steps: p is a radical of 0 →1.2p 0 →1.4p 0 →1.6p 0 →1.8p 0 →2p 0 ……；
Recording grouting pressure value p si Corresponding actual slurry flow rate Q si ；
Calculating to obtain grouting pressure values p of the grouting test at different grouting pressure values through a formula (3) si The following slurry permeability:
wherein q is si For the starch penetration rate, Lu; l is the length of the test segment, m; p is a radical of si The grouting pressure value is the grouting pressure value of the grouting test, and is MPa; q si The actual slurry flow rate of the grouting test is L/min;
preferably, the slurry taking rate q si Grouting pressure value p when being more than 1Lu si As priming pressure P 1 Corresponding to an actual slurry flow rate of Q 1 ，
Preferably, in the grouting test process, the grouting pressure value when the adjacent holes have the slurry channeling caused by the grouting pressure of a certain stage is taken as the slurry channeling pressure P 2 Corresponding to an actual slurry flow rate of Q 2 。
6. The grouting transformation method of a fourth aquifer protection pillar of a liberation shallow as claimed in claim 1,
in the step S5, the grouting range is an area surrounded by the connected circle centers of the outermost grouting holes, the grouting range is defined as F2, the cross section of the grouting range is a quadrangle,
the boundary of the grouting range F2 is outside the boundary of the protective pillar range F1,
the distance between the boundary of the grouting range F2 and the boundary of the protective coal pillar range F1 is 2-4 times of the grouting diffusion radius R;
preferably, the grouting holes comprise a first type grouting hole and a second type grouting hole,
the plurality of first-type grouting holes are sequentially arranged to form a line, the plurality of second-type grouting holes are sequentially arranged to form another line,
arranging a row of the first type grouting holes at the boundary of the grouting range F2, arranging a row of the second type grouting holes, arranging a row of the first type grouting holes until the middle line position of the grouting range F2, mirroring the arrangement of the first type grouting holes and the second type grouting holes until the other side boundary of the grouting range F2,
the first type grouting holes in the adjacent row are staggered with the second type grouting holes in the other row,
the distance between the circle center of the first type grouting hole in the adjacent row and the circle center of the second type grouting hole in the other row is 2 times of the grouting diffusion radius R,
when in construction, the first type of grouting holes are firstly constructed, then the second type of grouting holes are constructed,
preferably, the distance between the centers of two adjacent grouting holes in the same row is 2 times of the grouting diffusion radius R;
preferably, the grouting hole is a ground straight hole or a directional inclined hole,
preferably, the cross section of the grouting range is rectangular, and the ground position corresponding to the central point of the grouting range is a point O.
7. The grouting transformation method of a fourth aquifer protection pillar of a liberation shallow as claimed in claim 1,
in step S6, the grouting hole includes two open sections, namely a first open section and a second open section, the first open section starts from the ground surface and ends 5m below the top surface of the fourth aquifer, and the second open section starts from 5m below the top surface of the fourth aquifer and ends 10m below the top surface of the bedrock;
n grouting sections are arranged in the secondary opening section, the length of each grouting section is 4-8 m,
dividing N grouting sections into three transformation sections, namely an upper transformation section, a middle transformation section and a lower transformation section,
the upper reconstruction section begins 5m below the top surface of the fourth aquifer to end at the bottom surface of the N/3 grouting section,
the middle reconstruction section starts from the bottom surface of the N/3 grouting section to the bottom surface of the 2 x N/3 grouting section,
and the lower reconstruction section starts from the bottom surface of the 2 × N/3 grouting section to the bottom surface of the N grouting section.
8. The grouting transformation method of a fourth aquifer protection pillar of a liberation shallow as claimed in claim 7,
in the step S7, in the above step,
grouting treatment is carried out on the grouting of the second opening section by adopting a segmented descending and orifice closed static pressure grouting method;
preferably, a continuous and intermittent grouting combined grouting process is adopted in the grouting process;
during grouting, the two open sections are regarded as homogeneous strata, and different grouting pressure target values P are obtained 1 Or P 2 The following slurry diffusion radius R satisfies formula (3):
wherein R is the slurry diffusion radius m; k is the permeability coefficient of the soil layer to be injected and m/h, and is determined by an indoor test; t is the time required by the diffusion of the slurry and h, and is measured by a grouting test; h is the grouting pressure and m expressed by the height of a water column, and is measured by a grouting test; r is 0 Is the radius of the grouting pipe, m; n is the effective porosity of the injected coal rock mass and is determined by an indoor test; mu.s w The viscosity of water, mPa & s; mu.s s0 The initial viscosity and mPa & s of the slurry; alpha is the time-varying coefficient of the slurry viscosity; a is an integral parameter related to a time-varying coefficient alpha of the viscosity of the slurry; e is a natural constant with a value of 2.71828.
9. The grouting transformation method of a fourth aquifer protection pillar of a liberation shallow as claimed in claim 7,
in the step S7, the grouting material is mixed slurry of slag portland cement and fly ash,
preferably, the mixing amount of the fly ash in the grouting material in the upper modification section is 40-60% of the slag portland cement,
the mixing amount of the fly ash in the grouting material in the middle reconstruction section is 20-40% of that of the slag portland cement according to the mass ratio,
according to the mass ratio, the grouting material in the lower reconstruction section is not doped with fly ash, pure slag silicate cement slurry is adopted for grouting,
preferably, a descending sealing static pressure grouting sleeve is adopted for grouting,
the aperture of the first opening section is phi 216mm, a phi 177.8 multiplied by 8.05mm grouting sleeve is put in, cement is used for cementing,
the aperture diameter of the two-opening section is 152mm,
preferably, the grouting holes at the outermost side of the grouting range F2 are grouted first, then the other grouting holes of the first type are grouted, and finally the grouting holes of the second type are grouted;
preferably, the grouting areas F2 except the outermost grouting holes and the middle and lower reconstruction sections are grouted by normal grouting pressure P,
and the grouting holes and the upper transformation section on the outermost side of the grouting range F2 reduce the grouting final pressure to be P-delta P, wherein the delta P is 0.5-1.0MPa, and the diffusion range of the grout is controlled.
10. The grouting transformation method of a fourth aquifer protection pillar of a liberation shallow as claimed in claim 1,
in the step S8, performing grouting stopping control by using the dual standards of grouting final pressure and grouting amount;
preferably, the grouting final pressure is not lower than 1.5 times of the hydrostatic pressure of the tested section;
when the grouting pressure reaches the end standard, the pump amount is reduced by gear shifting gradually until the pump amount reaches 60L/min, water pressing is carried out after 30min is maintained, the unit water absorption rate is not more than 1Lu,
and stopping grouting under the condition that the two standards are met simultaneously.
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