Advanced reconstruction method of high porosity aquifer based on groundwater resource protection

Abstract

The application provides a high porosity aquifer advanced reconstruction method based on groundwater resource protection, which comprises the following steps: a water conducting fracture zone calculation formula is given and the water conducting fracture zone development height is calculated; if the water conducting fracture zone does not enter the aquiclude and the original aquiclude thickness is less than the optimal aquiclude thickness x, the region needs to be advanced reconstructed for the high porosity aquifer. During the reconstruction, a horizontal directional drilling hole is constructed from the ground to the high porosity aquifer between the water conducting fracture zone top boundary and the aquiclude bottom boundary; after the grouting process is completed, a vertical inspection hole is constructed on the ground to sample and test the grouting horizon core. The upper section of the high porosity aquifer is reconstructed into an aquiclude by using a grouting process, so as to increase the thickness of the aquiclude under the target protection aquifer, reduce the groundwater loss amount of the target protection aquifer overlying the aquiclude, and realize the protection of the target protection aquifer groundwater resource.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of coal seam roof aquifer groundwater protection, and particularly relates to a high porosity aquifer advanced reconstruction method based on groundwater resource protection. BACKGROUND

[0002] In the northwest region of China, surface water resources are scarce, and groundwater resources, as an important part of water resources, even become the only water supply source in many regions, and play an important role in maintaining industrial and agricultural production, human and animal drinking water, and controlling ecological environment. Large-scale and high-intensity mining of coal resources changes the internal structure of the aquiclude and the original water storage structure, forming a series of water-conducting fissures in the stratum, accelerating the hydraulic connection between the overlying aquifers of the coal seam, and causing the aquifer groundwater flowing into the mining space to be converted into mine water inrush. A large amount of mine water inrush induces the decline of the groundwater level in the mining area, the loss of groundwater resources, and leads to the exhaustion of regional groundwater resources and the degradation of the ecological environment. At present, mining methods such as limited high mining and filling mining are commonly used to reduce the disturbance of mining on groundwater, but there are problems such as large waste of coal resources and low mining efficiency. SUMMARY

[0003] The present application aims to at least solve one of the technical problems in the related art. To this end, the present application provides a high porosity aquifer advanced reconstruction method based on groundwater resource protection, which can reduce the loss of aquifer groundwater above the aquiclude disturbed by coal seam mining, and realize the protection of aquifer groundwater resources.

[0004] The present application provides a high porosity aquifer advanced reconstruction method based on groundwater resource protection, which comprises the following steps:

[0005] Step S1, collecting the measured data of the regional water-conducting fissure zone, respectively counting the development height H of the water-conducting fissure zone, the coal seam mining thickness M, the coal seam mining depth D, and the coal mining face width B, and using a multiple regression analysis method to obtain an empirical formula of the water-conducting fissure zone height:

[0006] Formula one: H = a x M + b x B + g x ln(D) + C

[0007] Wherein, a, b, and g are fitting parameters, C is a constant, D = M1 + M2 + M3 + M4, M1 is the target protection aquifer thickness, M2 is the aquiclude thickness, M3 is the high porosity aquifer thickness, and M4 is the bedrock aquifer thickness, M1, M2, M3, and M4 are obtained by searching regional geological exploration drilling data;

[0008] At the same time, the target protective aquifer, aquiclude, high porosity aquifer and coal seam are tested for bulk density, elastic modulus, cohesion, internal friction angle, Poisson's ratio, porosity and permeability coefficient. On this basis, a coal seam mining groundwater loss model is built on a COMSOL multi-physical field coupling analysis software simulation platform to analyze the relationship between different aquifer thickness and target protective aquifer groundwater loss under the conditions of average coal seam thickness and average coal seam depth, and the following formula is obtained:

[0009] Formula two: y = a + b x c x

[0010] Wherein: y is the groundwater loss, x is the aquifer thickness, b and c are fitting parameters, and a is a constant;

[0011] When d(y) / d(x) = -0.75, the aquifer thickness x is the optimal aquifer thickness. The optimal aquifer thickness x is obtained by differentiating and transforming formula two as follows:

[0012]

[0013] Step S2, based on the aquiclude thickness M2 data of each exploration borehole, an aquiclude thickness contour distribution map of the region is drawn, and the area where the water flowing fractured zone does not enter the aquiclude and the original aquiclude thickness is less than the optimal aquiclude thickness x is circled, and it is considered that the area needs to be pre-reformed for high porosity aquifer;

[0014] Step S3, the aquiclude is sampled, and the mineral composition and mechanical parameters of the aquiclude are tested and obtained, and the grouting material similar to the properties of the aquiclude is obtained through proportioning test;

[0015] Step S4, based on the regional exploration borehole data, the water flowing fractured zone development height H of the region is calculated using formula one, and a water flowing fractured zone top interface contour map is drawn, and a horizontal directional drilling hole is constructed from the ground downward, and the horizontal directional drilling hole terminal hole position is maintained at 15-20m below the aquiclude bottom boundary;

[0016] Step S5, the slurry is transported to the high porosity aquifer between the water flowing fractured zone top boundary and the aquiclude bottom boundary by the horizontal directional drilling hole using the grouting pump;

[0017] Step S6, after the grouting process is completed, a vertical inspection hole is constructed on the ground, the grouting position core is sampled, the slurry diffusion distance L is observed and measured, and the water pressure test is carried out to test the permeability coefficient of the grouting position. When the sum of the slurry diffusion distance L and the aquiclude thickness M2 is greater than the optimal aquiclude thickness x, and the ratio of the permeability coefficient of the grouting position tested by the water pressure test to the permeability coefficient of the aquiclude is less than 0.8, it is considered that the requirements are met. If the requirements are not met, grouting needs to be carried out again until the requirements are met.

[0018] In some embodiments, in step S3, the grouting material includes clay, cement and water, with the mass ratio of clay to cement being 8:2 and the water-to-solid ratio being 1:1.

[0019] In some embodiments, in step S5, the grouting termination pressure is 2.5 times the hydrostatic pressure of the high-porosity aquifer, and the grouting stabilization time is 30 minutes. Attached Figure Description

[0020] The above and / or additional aspects and advantages of the present invention will become apparent and readily understood from the following description of the embodiments taken in conjunction with the accompanying drawings.

[0021] in:

[0022] Figure 1 This is a flowchart of a method for advanced modification of high-porosity aquifers based on groundwater resource protection in an embodiment of the present invention;

[0023] Figure 2 This is a schematic diagram of a high-porosity aquifer advanced modification method based on groundwater resource protection in an embodiment of the present invention;

[0024] Figure 3 This is a graph showing the relationship between different impermeable layer thicknesses and groundwater loss in the target protected aquifer in an embodiment of the present invention.

[0025] Figure 4 This refers to the advanced modification area of ​​the high-porosity aquifer in this embodiment of the invention.

[0026] Figure label:

[0027] 1-Target protected aquifer; 2-Aquitard; 3-High porosity aquifer; 4-Bedrock aquifer; 5-Coal seam; 6-Boundary of water-conducting fracture zone; 7-Horizontal directional borehole; 8-Grouted rock mass; 9-Vertical inspection hole. Detailed Implementation

[0028] Embodiments of the present invention are described in detail below, examples of which are illustrated in the accompanying drawings. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain the present invention, and should not be construed as limiting the present invention.

[0029] The following describes an embodiment of the present invention with reference to the accompanying drawings, which is a method for advanced modification of high-porosity aquifers based on groundwater resource protection.

[0030] like Figure 1 , 2 As shown in the figure, this invention proposes a method for the advanced modification of high-porosity aquifers based on groundwater resource protection, comprising the following steps:

[0031] Step S1, collect the measured data of the water conducting fractured zone in the collection area, respectively, count the development height H of the water conducting fractured zone, the mining thickness M of the coal seam, the mining depth D of the coal seam, the width B of the coal mining face, and use the multiple regression analysis method to obtain the empirical formula of the height of the water conducting fractured zone:

[0032] Formula one: H = a x M + b x B + g x ln(D) + C

[0033] Wherein: a, b, g are fitting parameters, C is a constant, D = M1 + M2 + M3 + M4, M1 is the thickness of the target protective aquifer, M2 is the thickness of the aquiclude, M3 is the thickness of the high porosity aquifer, M4 is the thickness of the bedrock aquifer, M1, M2, M3, M4 are obtained by looking up the regional geological exploration drilling data;

[0034] At the same time, the bulk density, elastic modulus, cohesion, internal friction angle, Poisson's ratio, porosity, and permeability coefficient of the target protective aquifer, the aquiclude, the high porosity aquifer, and the coal seam are obtained through testing. On this basis, a coal mining groundwater loss model is constructed based on the COMSOL multi-physical field coupling analysis software simulation platform to analyze the relationship between the groundwater loss of the target protective aquifer and the different aquiclude thicknesses and the average coal seam thickness and the average coal seam depth in the area. The following formula is obtained:

[0035] Formula two: y = a + b x c x

[0036] Wherein: y is the groundwater loss, x is the aquiclude thickness, b, c are fitting parameters, and a is a constant;

[0037] The derivative of both sides of formula two is obtained, that is, dy / dx = bc x ln c.

[0038] When dy / dx = -0.75, the aquiclude thickness x is the optimal aquiclude thickness. The optimal aquiclude thickness x is obtained by transforming formula two:

[0039]

[0040] Step S2, based on the aquiclude thickness M2 data of each exploration drilling, draw the aquiclude thickness isopleth distribution map of the area, and delineate the area where the water conducting fractured zone has not entered the aquiclude and the original aquiclude thickness is less than the optimal aquiclude thickness x. It is considered that the area needs to be pre-reformed for the high porosity aquifer;

[0041] Step S3, sample the aquiclude, test and obtain the mineral composition and mechanical parameters of the aquiclude, and obtain the grouting material similar to the properties of the aquiclude through proportioning test;

[0042] Step S4, based on regional exploration drilling data, the formula is used to calculate the development height H of the water-conducting fractured zone in the region, and the water-conducting fractured zone top interface contour map is drawn, and the horizontal directional drilling is constructed from the ground downward, and the horizontal directional drilling terminal hole layer position is kept at 15-20m below the bottom boundary of the aquiclude;

[0043] Step S5, the slurry is transported to the high-porosity aquifer between the water-conducting fractured zone top boundary and the aquiclude bottom boundary by the horizontal directional drilling through the grouting pump to form the grouting stone body;

[0044] Step S6, after the grouting process is completed, the vertical inspection hole is constructed on the ground, the grouting layer position core is sampled, the slurry diffusion distance L is observed and measured, and the water pressure test is carried out to test the permeability coefficient of the grouting layer position, when the sum of the slurry diffusion distance L and the aquiclude thickness M2 is greater than the optimal aquiclude thickness x, and the ratio of the permeability coefficient of the grouting layer position tested by the water pressure test to the aquiclude permeability coefficient is less than 0.8, it is considered that the transformation requirement is met, if the requirement is not met, the grouting needs to be carried out again until the requirement is met.

[0045] It should be noted that in some mines in the northwest region, as shown in Figure 2 , the lower part of the target protection aquifer is an aquiclude, and there is a high-porosity aquifer below the aquiclude, and the lower part of the high-porosity aquifer is a bedrock aquifer, and the lower part of the bedrock aquifer is a coal seam. The high-porosity aquifer and the bedrock aquifer form a water-conducting fractured zone boundary, and the upper part of the water-conducting fractured zone boundary is the water-conducting fractured zone top boundary.

[0046] The embodiment of the application seeks to transform space in the aquiclude below the target protection aquifer before coal mining, and uses the grouting process to transform the upper section of the high-porosity aquifer into an aquiclude, thereby increasing the thickness of the aquiclude below the target protection aquifer, reducing the entry of groundwater in the target protection aquifer into the mining space caused by coal mining disturbance, reducing the groundwater loss of the target protection aquifer overlying the aquiclude, and achieving the protection of the groundwater resources of the target protection aquifer.

[0047] As shown in Figure 3 , the relationship between different aquiclude thicknesses and target protection aquifer groundwater loss is shown, and it can be seen that the thicker the aquiclude, the smaller the groundwater loss of the target protection aquifer. As shown in Figure 4 , the high-porosity aquifer transformation area is shown, which is 15-20m below the bottom boundary of the aquiclude.

[0048] Further, in step S2, as shown in Figure 1As shown, if the water conducting fracture zone enters the aquifuge, and the distance between the top boundary of the water conducting fracture zone and the top boundary of the aquifuge is greater than the optimal aquifuge thickness x, normal mining is performed, if the distance between the top boundary of the water conducting fracture zone and the top boundary of the aquifuge is less than the optimal aquifuge thickness x, filling mining or height-limited mining is performed. If the water conducting fracture zone does not enter the aquifuge, and the original aquifuge thickness is greater than the optimal aquifuge thickness x, normal mining is performed.

[0049] In some embodiments, in step S3, the grouting material comprises clay, cement and water, the mass ratio of the clay and the cement is 8:2, and the solid-liquid ratio of the water is 1:1.

[0050] It should be noted that, since the components of the aquifuge are generally clay and sub-clay, the grouting material for transforming the high-porosity aquifer is mainly clay. In order to improve the mechanical parameters of the grouting stone, an appropriate amount of cement is added to the clay slurry.

[0051] In some embodiments, in step S5, the grouting final pressure is 2.5 times the hydrostatic pressure of the high-porosity aquifer, and the grouting pressure stabilizing time is 30 minutes.

[0052] The application will be further described below through specific embodiments.

[0053] Embodiment 1

[0054] Taking a typical working face in the Ordos Basin as an example, the advanced transformation method of the high-porosity aquifer based on the protection of groundwater resources comprises the following steps:

[0055] Step one: collect the measured data of the regional water conducting fracture zone (Table 1), respectively count the development height (H) of the water conducting fracture zone, the mining thickness (M) of the coal seam, the mining depth (D) of the coal seam, and the width (B) of the coal mining working face, and obtain the height empirical formula of the water conducting fracture zone by using the multiple regression analysis method:

[0056] H = 20.266 x M + 0.094 x B + 13.817 x ln S - 88.443 (R 2 = 0.788)

[0057] Table 1: measured data of the regional water conducting fracture zone

[0058]

[0059]

[0060] Step two: construct a groundwater loss model of the coal seam mining, and obtain the relationship between the different aquifuge thicknesses and the groundwater loss amount of the target protection aquifer. The groundwater loss amount of the target protection aquifer and the aquifuge thickness present a power exponential relationship, which is shown in the following formula.

[0061] y = 215.34 + 114.28 x 0.95 x (R 2 = 0.9945)

[0062] In the formula: y is the amount of groundwater loss (m 3 / h), x is the thickness of the aquiclude (m).

[0063] When d(y) / d(x) = -0.75, the thickness of the aquiclude x is the optimal aquiclude thickness. At this time, the optimal aquiclude thickness x is obtained by the following formula:

[0064]

[0065] Step three: Based on the above given empirical formula of the height of the water flowing fractured zone, it is judged that the working face water flowing fractured zone has not entered the aquiclude (15-20m away from the bottom boundary of the aquiclude), and the original aquiclude thickness in most areas is less than 40m. It is considered that the area with original aquiclude thickness less than 40m needs to be modified in advance for high porosity aquifer.

[0066] Step four: The aquiclude is sampled, and the mineral composition and mechanical parameters of the aquiclude are tested and obtained. On this basis, the grouting material similar to the properties of the aquiclude is obtained through proportioning test. Since the aquiclude is generally composed of clay and sub-clay, the grouting material for modifying the high porosity aquifer is mainly clay. In order to improve the mechanical parameters of the grouting stone, a proper amount of cement can be added to the clay slurry. Since there is a large amount of loess (a kind of clay) around the coal mine, in the specific implementation, the grouting material uses a mixture of loess and cement, and the proportion is 8:2, and the water-solid ratio of the slurry is 1:1.

[0067] Step five: Based on the exploration drilling data of the working face, the height of the water flowing fractured zone is calculated using the empirical formula of the height of the water flowing fractured zone, and the contour map of the top boundary of the water flowing fractured zone is drawn. The horizontal directional drilling hole is constructed, and the final hole layer position is maintained at 15-20m below the bottom boundary of the aquiclude.

[0068] Step six: The slurry is delivered to the high porosity aquifer between the top boundary of the water flowing fractured zone and the bottom boundary of the aquiclude by the horizontal directional drilling hole using the grouting pump. The hydrostatic pressure of the high porosity aquifer in the working face is 1MPa, and the grouting final pressure is 2.5 times the hydrostatic pressure of the high porosity aquifer, so the grouting final pressure is set to 2.5MPa; the grouting pressure holding time is 30min.

[0069] Step seven: after the completion of the grouting process, vertical inspection holes are constructed downward from the ground, and the grouting layer core is sampled and water pressure test is carried out. The results show that the slurry diffusion distance L is more than 30 m, the original water-resisting layer thickness M2 is generally greater than 10 m, the sum of the slurry diffusion distance and the water-resisting layer thickness is greater than the optimal water-resisting layer thickness 40 m, and the thickness requirement is met. The grouting layer permeability coefficient is 0.04 m / d, the water-resisting layer permeability coefficient is 0.034 m / d, and the ratio of the two is less than 0.8, which is considered to meet the permeability coefficient requirement of the reconstruction.

[0070] In the description of the present application, it should be understood that the terms "center", "longitudinal", "transverse", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential" and the like indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the devices or elements referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as limiting the present application.

[0071] In addition, the terms "first", "second" are only for descriptive purposes, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the technical features indicated. Therefore, the features defined with "first", "second" can explicitly or implicitly include at least one of the features. In the description of the present application, the meaning of "a plurality of" is at least two, such as two, three, etc., unless otherwise specifically limited.

[0072] In the present application, unless otherwise specifically defined and limited, the terms "mounting", "connection", "connection", "fixing" and the like should be broadly understood, for example, it can be fixedly connected, or it can be detachably connected, or it can be integrated; it can be mechanically connected, or it can be electrically connected or in communication with each other; it can be directly connected, or it can be indirectly connected through an intermediate medium; it can be the internal communication or interaction relationship of two elements, unless otherwise specifically limited. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0073] In the present application, unless specifically stated and limited otherwise, a first feature "on" or "under" a second feature can be directly in contact with the second feature, or indirectly in contact with the second feature through an intermediate medium. Also, a first feature "over", "above" and "on top of" a second feature can be directly above or obliquely above the second feature, or simply means that the first feature is horizontally higher than the second feature. A first feature "under", "below" and "underneath" a second feature can be directly below or obliquely below the second feature, or simply means that the first feature is horizontally lower than the second feature.

[0074] In the present application, the terms "one embodiment", "some embodiments", "an example", "a specific example", or "some examples" mean that a particular feature, structure, material, or characteristic being described is included in at least one embodiment or example of the present application. The illustrative appearances of the above-mentioned terms in various places in the specification are not necessarily intended to refer to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics can be combined in any suitable manner in one or more embodiments or examples. Moreover, the terms "first", "second", "third", etc. are used herein merely as identifiers for different elements, regions, layers, or sections, and are not intended to denote a spatial or chronological priority or sequence.

[0075] Although the embodiments of the present application have been shown and described above, it is understood that the above-described embodiments are exemplary, and are not to be interpreted as limiting the present application, and that changes, modifications, substitutions and variations can be made by those skilled in the art without departing from the scope of the present application.

Claims

1. A method for advance reconstruction of high-porosity aquifer based on groundwater resource protection, characterized by, It comprises the following steps: Step S1, collecting the measured data of the regional water-conducting fractured zone, respectively counting the water-conducting fractured zone development height H, the coal seam mining thickness M, the coal seam mining depth D, the coal mining working face width B, and using the multiple regression analysis method to obtain the water-conducting fractured zone height empirical formula: Formula one: H = a x M + b x B + g x ln(D) + C Wherein: a, b, g are fitting parameters, C is a constant, D = M1 + M2 + M3 + M4, M1 is the target protective aquifer thickness, M2 is the aquifuge thickness, M3 is the high porosity aquifer thickness, M4 is the bedrock aquifer thickness, M1, M2, M3, M4 are obtained by looking up regional geological exploration drilling data; At the same time, the bulk density, elastic modulus, cohesion, internal friction angle, Poisson's ratio, porosity and permeability coefficient of the target protective aquifer, aquifuge and high porosity aquifer and coal seam are obtained by testing, and on this basis, the COMSOL multi-physical field coupling analysis software is used as the simulation platform to build a coal seam mining groundwater loss model, and the relationship between the groundwater loss and the aquifuge thickness and the target protective aquifer under the conditions of the average coal seam thickness and the average coal seam depth is analyzed, and the following formula is obtained: Equation two: y = a + b x c x Wherein: y is the groundwater loss, x is the aquifuge thickness, b, c are fitting parameters, a is a constant; When d(y) / d(x) = -0.75, the aquifuge thickness x is the optimal aquifuge thickness, the optimal aquifuge thickness x is obtained by the following formula: Equation Three: Step S2, based on the aquifuge thickness M2 data of each exploration drilling, the regional aquifuge thickness contour distribution map is drawn, the area where the water-conducting fractured zone does not enter the aquifuge and the original aquifuge thickness is less than the optimal aquifuge thickness x is circled, and it is considered that the area needs to be pre-reformed for the high porosity aquifer; Step S3, sampling the aquifuge, testing and obtaining the mineral composition and mechanical parameters of the aquifuge, and obtaining the grouting material similar to the properties of the aquifuge through the proportioning test; Step S4, based on the regional exploration drilling data, the water-conducting fractured zone development height H of the region is calculated by formula one, and the water-conducting fractured zone top interface contour map is drawn, and the horizontal directional drilling is constructed from the ground downward, and the horizontal directional drilling terminal hole position is kept at 15-20m below the aquifuge bottom boundary; Step S5, the slurry is transported to the high porosity aquifer between the water-conducting fractured zone top boundary and the aquifuge bottom boundary by the horizontal directional drilling through the grouting pump; Step S6, after the grouting process is completed, the vertical inspection hole is constructed on the ground, the grouting layer position core is sampled, the slurry diffusion distance L is observed and measured, and the water pressure test is carried out, and the permeability coefficient of the grouting layer position is tested, when the sum of the slurry diffusion distance L and the aquifuge thickness M2 is greater than the optimal aquifuge thickness x, and the ratio of the permeability coefficient of the grouting layer position tested by the water pressure test to the aquifuge permeability coefficient is less than 0.8, it is considered that the requirements are met; if the requirements are not met, grouting needs to be carried out again until the requirements are met.

2. The groundwater resource protection based high porosity aquifer pre- construction method according to claim 1, characterized in that, In the step S3, the grouting material comprises clay, cement and water, the mass ratio of clay and cement is 8:2, and the solid-liquid ratio of water is 1:

1.

3. The groundwater resource protection based high porosity aquifer pre- construction method according to claim 1, characterized in that, In the step S5, the grouting final pressure is 2.5 times of the hydrostatic pressure of the high porosity aquifer, and the grouting pressure maintaining time is 30 minutes.

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