Water resource protection and utilization method under mining variation of different double-aquifer structures

Abstract

The invention provides a water resource protection and utilization method under mining variation of different double aquifer structures, and belongs to the technical field of mining engineering. Firstly, according to stratum conditions and parameters obtained on site, in combination with the spatial position relation of main key stratums and aquifers, three types of double aquifer structures including an upper main key stratum-lower group vulnerable type structure, a middle main key stratum-upper and lower unidirectional type structure and a lower main key stratum-upper group protection type structure are provided; secondly, based on different variation characteristics of double aquifer structures caused by mining activities, comparing the height h of a water guide channel after mining, the distance D3 from a main key layer to a coal seam, the thickness d3 of the main key layer, the thicknesses d1 and d2 of an upper protective layer and a lower protective layer, and the distances D1 and D2 from the double aquifers to the coal seam; five water resource protection and utilization methods including upper storage-lower storage, upper resistance-lower storage, upper protection-lower storage, upper resistance-lower resistance and upper resistance-lower protection are provided, and coordinated development of mining area coal resource development and water resource comprehensive protection and utilization is achieved.

Description

Technical Field

[0001] The present invention relates to the technical field of mining engineering, and in particular to a method for protecting and utilizing water resources under the variation of mining in different double-aquifer structures. Background Art

[0002] During the coal resource extraction process, mining activities cause damage to the overlying rock, reduce the roof stability, and break the rock strata, thereby generating water-conducting channels, causing the variation of the aquifer structure, resulting in the loss of groundwater resources and the decline of the groundwater level. Further, it causes the vegetation relying on groundwater to wither due to water shortage, leading to a sharp reduction in biodiversity, soil erosion, and land desertification.

[0003] During the development of the Huanglong Jurassic coalfield, it is found that there are two double aquifers with different buried depths above the working face of this coalfield, namely the Zhiluo Formation of the Jurassic System and the Luohe Formation of the Cretaceous System. This geological feature has long posed a threat to safe coal mining and at the same time brought high costs to enterprises in terms of water resource protection.

[0004] The Chinese invention patent with the patent publication number CN103513281A discloses a method for predicting the development height of the water-conducting fissure zone in overlying strata of solid filling coal mining. The method for predicting the development height of the water-conducting fissure zone in overlying strata of solid filling coal mining of this invention is based on engineering geological condition information and rock mechanics experiments, and adopts a method combining numerical simulation and multiple regression analysis to obtain the relationship expression between the filling rate, mining height and the development height of the water-conducting fissure zone. Then, according to the actual engineering parameters of filling coal mining, that is, the designed filling rate and the actual mining height, the development height of the water-conducting fissure zone in overlying strata is calculated.

[0005] The Chinese invention patent with the patent publication number CN118705007A discloses a method and device for protecting groundwater in coal mining areas. Based on the groundwater movement speed and the extraction time, this invention determines the transfer and storage area from the target layer, so as to ensure that within the extraction time, mine water does not flow into the mine to form mine water inrush, and thus does not affect the mine extraction production.

[0006] The above existing technologies have the following problems:

[0007] First, other influencing factors on the aquifer except for water-conducting fissures are not considered;

[0008] Second, only considering protecting the aquifer by filling the goaf, this general protection method often causes waste of funds;

[0009] Third, the goaf formed by mining is not utilized as the storage space of the aquifer;

[0010] Fourth, only regarding the two aquifers as a whole for protection, and no classified protection measures are taken for aquifers with different buried depths. Summary of the Invention

[0011] The object of the present invention is to provide a method for protecting and utilizing water resources under the mining-induced variation of different double-aquifer structures, realizing the coordinated development of coal resource development and comprehensive water resource protection and utilization in mining areas.

[0012] To achieve the above object, the present invention provides a method for protecting and utilizing water resources under the mining-induced variation of different double-aquifer structures, including the following steps:

[0013] Step S1: In view of the geological characteristics that there are two aquifers, namely the Zhiluo Formation of the Jurassic System and the Luohe Formation of the Cretaceous System, above the longwall coal mining face during the development of the Huanglong Jurassic coalfield, obtain the mining height M of the coal mining face, the distance D1 from the upper aquifer to the coal seam, and the distance D2 from the lower aquifer to the coal seam. Among them, in the double-aquifer of the strata, the aquifer with a smaller distance from the aquifer to the surface is defined as the upper aquifer, and the aquifer with a larger distance from the aquifer to the surface is defined as the lower aquifer; obtain the physical parameters of the coal body and each layer of rock through rock mechanics tests, and measure the original rock stress σ of the rock by the hydraulic fracturing method;

[0014] Among them, the physical parameters of the coal body and each layer of rock include rock density ρ, shear modulus G, bulk modulus K, and compressive strength σ c ;

[0015] Step S2: Based on the data obtained in Step S1, establish a three-dimensional numerical simulation model in the 3DEC numerical simulation software to obtain the height h of the water-conducting channel generated from bottom to top in the overlying strata of the working face; calculate the protective layer thickness d1 of the upper aquifer and the protective layer thickness d2 of the lower aquifer by using the protective layer thickness calculation formula in the Code for Pillar Setting and Coal Mining under Buildings, Water Bodies, Railways and Main Roadways;

[0016] Step S3: Based on the physical parameters of the coal body and each layer of rock in Step S1, with the help of the key layer discrimination software KSPB, obtain the distance D3 from the main key layer to the coal seam, and obtain the thickness d3 of the main key layer by using the stratigraphic columnar section;

[0017] Compare D1, D2, and D3 to determine the positional relationship between the main key layer structure and the upper and lower aquifers, including the following three types:

[0018] When D1 < D3, it is an upper main key layer - lower group vulnerable double-aquifer structure, that is, the main key layer is located above the upper aquifer and has no protective effect on both double-aquifers;

[0019] When D1 > D3 > D2, it is a middle main key layer - upper and lower unidirectional double-aquifer structure, that is, the main key layer is located between the upper and lower aquifers and has a unidirectional protective effect on the upper aquifer and no protective effect on the lower aquifer;

[0020] When D3 < D2, it is a lower main key stratum - upper group protection type double aquifer structure, that is, the main key stratum is located below the lower aquifer and has a protective effect on both aquifers;

[0021] Step S4: According to the different spatial position relationships and protection methods between the aquifer and the main key stratum, design the following five water resource protection and utilization methods:

[0022] Upper storage - lower storage method: The height of the water - conducting channel is greater than the thickness of the protective layer. The upper and lower aquifers are penetrated by the water - conducting channel. Build artificial dams and coal pillar dams to block the goaf, making the goaf form an underground reservoir, and use the water - conducting channel to divert water flow into the underground reservoir for storage;

[0023] Upper resistance - lower storage method: The water - conducting channel penetrates the lower aquifer but does not affect the upper aquifer. Use the water - impermeability of the upper protective layer to block the loss of water in the upper aquifer, and at the same time use the water - conducting channel to divert the water flow in the lower aquifer into the underground reservoir for storage;

[0024] Upper protection - lower storage method: The water - conducting channel develops into the protective layer of the upper aquifer. Fill the goaf with gangue to protect the upper aquifer by reducing the water - conducting channel, and at the same time use the water - conducting channel to divert the water flow in the lower aquifer into the underground reservoir for storage;

[0025] Upper resistance - lower protection method: The water - conducting channel develops into the protective layer of the lower aquifer and does not affect the upper aquifer. Use the water - impermeability of the upper protective layer to block the loss of water in the upper aquifer, and at the same time fill the goaf with gangue to protect the lower aquifer by reducing the water - conducting channel;

[0026] Upper resistance - lower resistance method: The water - conducting channel does not affect the stability of the upper and lower aquifers. Use the water - impermeability of the upper and lower protective layers to prevent water loss;

[0027] Step S5: Determine the specific protection method according to the main key stratum structure type, the height h of the water - conducting channel, and the thicknesses d1 and d2 of the upper and lower protective layers;

[0028] In the case of the upper main key stratum - lower group vulnerable type double aquifer structure, the protection method is determined as follows:

[0029] When D1 < h, the water - conducting channel caused by mining activities develops above the upper aquifer, that is, penetrates both the upper and lower aquifers, and the upper storage - lower storage method is adopted;

[0030] When D1 > h > D1 - d1, the water - conducting channel caused by mining activities develops inside the protective layer of the upper aquifer and affects the protective layer of the upper aquifer, and the upper protection - lower storage method is adopted;

[0031] When D2 < h < D1 - d1, the water-conducting channel caused by mining activities develops between the protective layer of the lower aquifer and the upper aquifer, and the method of upper resistance - lower storage is adopted;

[0032] When D2 > h > D2 - d2, the water-conducting channel caused by mining activities affects the protective layer of the lower aquifer, and the method of upper resistance - lower protection is adopted;

[0033] When h < D2 - d2, the water-conducting channel caused by mining activities develops below the protective layer of the lower aquifer, and the protection method of upper resistance - lower resistance is adopted;

[0034] In the case of the middle main key stratum - upper and lower unidirectional double aquifer structure, the determination of the protection method is as follows:

[0035] When D3 + d3 < h, the water-conducting channel caused by mining activities penetrates the main key stratum, and the main key stratum cannot serve as a bearing structure to protect the upper aquifer, and the method of upper storage - lower storage is adopted;

[0036] When D3 + d3 > h > D1 - d1, the water-conducting channel caused by mining activities develops inside the protective layer of the upper aquifer, and the main key stratum has not broken and still has a bearing function, and the method of upper protection - lower storage is adopted;

[0037] When D2 < h < D1 - d1, the water-conducting channel develops between the protective layer of the upper aquifer and the lower aquifer. The upper aquifer uses the protective layer to separate the water-conducting channel from the aquifer, and the lower aquifer uses the underground reservoir for water storage, and the method of upper resistance - lower storage is adopted;

[0038] When D2 > h > D2 - d2, the water-conducting channel develops inside the protective layer of the lower aquifer, and the method of upper resistance - lower protection is adopted;

[0039] When h < D2 - d2, the water-conducting channel develops below the protective layer of the lower aquifer, and the method of upper resistance - lower resistance is adopted;

[0040] In the case of the lower main key stratum - upper group protection type double aquifer structure, the determination of the protection method is as follows:

[0041] When h > D3 + d3, the water-conducting channel caused by mining activities penetrates the main key stratum, and the main key stratum cannot serve as a bearing structure, and the method of upper storage - lower storage is adopted;

[0042] When D2 - d2 < h < D3 + d3, the water-conducting channel develops inside the protective layer of the lower aquifer, and the main key stratum has not broken and still has a bearing function, and the method of upper resistance - lower protection is adopted;

[0043] When D2 - d2 > h, the water-conducting channel develops below the protective layer of the lower aquifer. The protective layer is used to block the loss of water to achieve the protection of groundwater, and the method of upper block - lower block is adopted.

[0044] Therefore, the present invention adopts the above-mentioned method for protecting and utilizing water resources under the mining variation of a different dual-aquifer structure, and the beneficial technical effects are as follows:

[0045] (1) According to the different distances between the aquifer and the ground surface, a precise classification protection method is adopted for the dual aquifers, making the method for protecting the underground aquifer more refined, more scientific, and with lower costs;

[0046] (2) The goaf formed by coal mining is utilized, which can reduce the harm brought by the spontaneous combustion of the remaining coal in the goaf to the working face and reduce the cost in terms of fire prevention and extinguishment;

[0047] (3) From originally only considering one criterion of water-conducting fissures to considering multiple criteria such as the thickness of the protective layer, the protection method becomes more refined, and the effect after protection is more reliable and safe. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] Figure 1 It is a schematic flow chart of the method for protecting and utilizing water resources under the mining variation of a different dual-aquifer structure of the present invention;

[0049] Figure 2 It is a stratigraphic cross-section when the upper main key stratum is present;

[0050] Figure 3 It is a stratigraphic cross-section when the middle main key stratum is present;

[0051] Figure 4 It is a stratigraphic cross-section when the lower main key stratum is present;

[0052] REFERENCE SIGNS

[0053] 1. Upper aquifer; 2. Main key stratum; 3. Lower aquifer; 4. Water-conducting channel; 5. Goaf; 6. Coal seam. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0054] The technical solutions of the present invention will be further described below with reference to the drawings and embodiments.

[0055] Unless otherwise defined, the technical terms or scientific terms used in the present invention shall have the ordinary meanings understood by those of ordinary skill in the art to which the present invention pertains.

[0056] Such as Figure 1As shown in the figure, in view of the geological characteristics of two aquifers, namely the Zhiluo Formation of the Jurassic and the Luohe Formation of the Cretaceous, existing above the longwall coal mining face during the development of the Huanglong Jurassic coalfield, and the water resource loss and ecological environment problems caused by improper groundwater protection methods in this area, the present invention proposes a method for protecting and utilizing water resources under different double-aquifer structure mining variations. The method includes the following steps:

[0057] Step S1: First, obtain the mining height M of the coal mining face, the distance D1 between the upper aquifer and the coal seam, and the distance D2 between the lower aquifer and the coal seam. Among them, in the double-aquifer of the strata, the aquifer with a smaller distance between the aquifer and the surface is defined as the upper aquifer, and the aquifer with a larger distance between the aquifer and the surface is defined as the lower aquifer;

[0058] Secondly, obtain the physical parameters of the coal body and each layer of rock by means of rock mechanics tests, including rock density ρ, shear modulus G, bulk modulus K, and compressive strength σ c , and measure the original rock stress σ of the rock by means of the hydraulic fracturing method.

[0059] Step S2: Based on the mining height M of the working face, the distances D1 and D2 between the double aquifers and the coal seam respectively, and the physical and mechanical parameters of the coal and rock mass obtained in Step S1, establish a three-dimensional numerical simulation model in the 3DEC numerical simulation software to obtain the water-conducting channels generated from bottom to top in the overlying strata of the working face, and record their height as h; at the same time, in order to determine the penetration distance of water in the pores of the rock strata, use the calculation formula for the protective layer thickness in the "Code for the Setting of Coal Pillars for Buildings, Water Bodies, Railways and Main Roadways and Coal Mining under Pressure" to calculate the protective layer thickness d1 of the upper aquifer and the protective layer thickness d2 of the lower aquifer, that is, the penetration distance of water in the upper aquifer is d1, and the penetration distance of water in the lower aquifer is d2.

[0060] Step S3: Based on the physical parameters of the coal body and each layer of rock in Step S1, and with the help of the key layer discrimination software KSPB, obtain the distance D3 between the main key layer and the coal seam and obtain the thickness d3 of the main key layer by using the stratigraphic columnar section; at the same time, by comparing D1, D2, and D3 obtained in Step S1, the following three position relationships between the main key layer structure and the upper and lower two aquifers can be obtained, which are respectively:

[0061] When D1 < D3, it is called the upper main key layer - lower group vulnerable double-aquifer structure, that is, the main key layer is located above the upper aquifer and has no protective effect on both aquifers;

[0062] When D1 > D3 > D2, it is called the middle main key layer - upper and lower one-way double-aquifer structure, that is, the main key layer is located between the upper and lower two aquifers and has a one-way protective effect on the upper aquifer and no protective effect on the lower aquifer;

[0063] When D3 < D2, it is called the lower main key stratum - upper group protection type double aquifer structure, that is, the main key stratum is located below the lower aquifer and has a protective effect on both aquifers.

[0064] Step S4: Based on the different spatial position relationships and protection methods between the aquifer and the main key stratum, design 5 specific protection methods: ① upper storage - lower storage method, ② upper barrier - lower storage method, ③ upper protection - lower storage method, ④ upper barrier - lower protection method, ⑤ upper barrier - lower barrier method.

[0065] The upper storage - lower storage method means that the height of the water - conducting channel is greater than the thickness of the protective layer, that is, both the upper and lower aquifers are penetrated by the water - conducting channel, and the water - proof property of the protective layer cannot be used to block the loss of water. First, design the parameters of the underground reservoir according to the overlying rock characteristics, and then build artificial dams and coal - pillar dams to seal the goaf, so that the water flows through the water - conducting channel and is diverted into the underground reservoir for storage, achieving the purpose of lower storage protection for both the upper and lower aquifers.

[0066] The upper barrier - lower storage method means that the water - conducting channel penetrates the lower aquifer, and the water - proof layer of the lower aquifer cannot be used to block the loss of water, while the upper aquifer is not affected by the water - conducting channel and its protective layer can be used to block the loss of water. The upper aquifer uses the water - proof property of the upper protective layer to block the loss of water in the upper aquifer, thereby achieving the purpose of upper barrier protection for the upper aquifer. At the same time, design the parameters of the underground reservoir for the lower aquifer according to the overlying rock characteristics, and then build artificial dams and coal - pillar dams to seal the goaf, so that the water flows through the water - conducting channel and is diverted into the underground reservoir for storage, achieving the purpose of lower storage for the lower aquifer.

[0067] The upper protection - lower storage method means that the water - conducting channel develops into the protective layer of the upper aquifer, the lower aquifer is penetrated, and the protective layer of the upper aquifer is affected. The upper aquifer first uses the protective layer thickness calculation formula in the "Code for the Setting of Coal Pillars for Buildings, Water Bodies, Railways and Main Roadways and Coal Mining under Pressure" to calculate the thickness of the upper protective layer and deduce the height threshold of the water - conducting channel, then uses the 3DEC numerical simulation software to simulate the height of the water - conducting channel under different packing rates, compares the height threshold of the water - conducting channel with the height of the water - conducting channel under different packing rates to obtain the critical packing rate, and finally fills the goaf with gangue under the condition of the critical packing rate, thereby achieving the purpose of upper protection for the upper aquifer. At the same time, design the parameters of the underground reservoir for the lower aquifer according to the overlying rock characteristics, and then build artificial dams and coal - pillar dams to seal the goaf, so that the water flows through the water - conducting channel and is diverted into the underground reservoir for storage, achieving the purpose of lower storage protection for the lower aquifer.

[0068] The upper-blocking and lower-protecting method means that the water-conducting channel develops between the upper-layer aquifer protection layer and the lower-layer aquifer, the lower-layer aquifer is penetrated, and the upper-layer aquifer is not affected. The upper-layer aquifer utilizes the water-blocking property of the upper-layer protection layer to block the loss of water in the upper-layer aquifer, thereby achieving the purpose of upper-blocking protection for the upper-layer aquifer. At the same time, the lower-layer aquifer first uses the calculation formula for the thickness of the protection layer in the "Code for Pillar Setting and Coal Mining with Pressure Relief for Buildings, Water Bodies, Railways and Main Roadways" to calculate the thickness of the lower-layer protection layer and deduce the height threshold of the water-conducting channel, and then uses the 3DEC numerical simulation software to simulate the height of the water-conducting channel under different filling rates. By comparing the height threshold of the water-conducting channel with the height of the water-conducting channel under different filling rates, the critical filling rate is obtained. Finally, the gob is filled with gangue under the condition of the critical filling rate, thereby achieving the purpose of lower-protecting the lower-layer aquifer.

[0069] The upper-blocking and lower-blocking method means that the development of the water-conducting channel does not affect the stability of the upper and lower aquifers. Therefore, both the upper and lower aquifers utilize the water-blocking property of the corresponding protection layers to prevent the loss of water, thereby achieving the purpose of upper-blocking and lower-blocking protection for the upper and lower aquifers.

[0070] Step S5: In the structure of the upper main key stratum - lower vulnerable double aquifers, that is, when the main key stratum is above the upper-layer aquifer, the main key stratum as the bearing structure cannot protect the double aquifers. Compare the distances D1 and D2 of the double aquifers from the coal seam respectively, the height h of the water-conducting channel, and the thicknesses d1 and d2 of the protection layers to determine the corresponding protection method.

[0071] When D1 < h, the water-conducting channel caused by mining activities develops above the upper-layer aquifer, that is, both the upper and lower aquifers are penetrated, and the upper-storage and lower-storage protection method is adopted;

[0072] When D1 > h > D1 - d, the water-conducting channel caused by mining activities develops inside the protection layer of the upper-layer aquifer and affects the protection layer of the upper-layer aquifer, and the upper-protecting and lower-storage protection method is adopted;

[0073] When D2 < h < D1 - d1, the water-conducting channel caused by mining activities develops between the lower-layer aquifer and the protection layer of the upper-layer aquifer, and the upper-blocking and lower-storage protection method is adopted;

[0074] When D2 > h > D2 - d2, the water-conducting channel caused by mining activities affects the protection layer of the lower-layer aquifer, and the upper-blocking and lower-protecting protection method is adopted;

[0075] When h < D2 - d2, the water-conducting channel caused by mining activities develops below the protection layer of the lower layer, and the upper-blocking and lower-blocking protection method is adopted.

[0076] When the middle key stratum has a one-way double-aquifer structure in the upper and lower directions, that is, the main key stratum is located between the upper and lower aquifers. At this time, the key stratum as the bearing structure can maintain the stability of the upper aquifer. At this time, compare the thicknesses of the protective layers d1 and d2, the height of the water-conducting channel h, the distance D3 from the main key stratum to the coal seam, and the thickness d3 of the main key stratum to determine whether the water-conducting channel will penetrate the aquifer and determine the corresponding protection method;

[0077] When D3 + d3 < h, the water-conducting channel caused by mining activities penetrates the main key stratum, and the main key stratum cannot serve as a bearing structure to protect the upper aquifer. The upper-storage and lower-storage protection method is adopted;

[0078] When D3 + d3 > h > D1 - d1, the water-conducting channel caused by mining activities develops inside the protective layer of the upper aquifer, and the main key stratum has not broken and still has a bearing function. The upper-protection and lower-storage protection method is adopted;

[0079] When D2 < h < D1 - d1, the water-conducting channel develops between the protective layer of the upper aquifer and the lower aquifer. The upper aquifer uses the protective layer to separate the water-conducting channel from the aquifer, and the lower aquifer stores water using the underground reservoir. The upper-blocking and lower-storage protection method is adopted;

[0080] When D2 > h > D2 - d2, the water-conducting channel develops inside the protective layer of the lower aquifer. The upper-blocking and lower-protection protection method is adopted;

[0081] When h < D2 - d2, the water-conducting channel develops below the protective layer of the lower aquifer. The upper-blocking and lower-blocking protection method is adopted.

[0082] When the lower main key stratum has an upper-group protective double-aquifer structure, that is, the main key stratum is located below the lower aquifer. The main key stratum as the bearing structure controls the stability of the upper and lower aquifers and the development height of the water-conducting channel. At this time, compare the height of the water-conducting channel h, the distance D3 from the main key stratum to the coal seam, and the thickness d3 of the main key stratum to determine the protection method.

[0083] When h > D3 + d3, the water-conducting channel caused by mining activities penetrates the main key stratum, and the main key stratum cannot serve as a bearing structure. The upper-storage and lower-storage protection method is adopted;

[0084] When D2 - d2 < h < D3 + d3, the water-conducting channel develops inside the protective layer of the lower aquifer, and the main key stratum has not broken and still has a bearing function. The upper-blocking and lower-protection protection method is adopted;

[0085] When D2 - d2 > h, the water-conducting channel develops below the protective layer of the lower aquifer. Use the protective layer to block the loss of water to achieve the protection of groundwater. The upper-blocking and lower-blocking protection method is adopted.

[0086] Example 1

[0087] The stratigraphic profile structure of the mining area in this example is as Figure 2 shown in the stratigraphic profile of the upper main key stratum. From top to bottom, they are: main key stratum 2, upper aquifer 1, lower aquifer 3, water-conducting channel 4, goaf 5, coal seam 6.

[0088] As Figure 3 shown in the stratigraphic profile of the middle main key stratum. From top to bottom, they are: upper aquifer 1, main key stratum 2, lower aquifer 3, water-conducting channel 4, goaf 5, coal seam 6.

[0089] As Figure 4 shown in the stratigraphic profile of the lower main key stratum. From top to bottom, they are: upper aquifer 1, lower aquifer 3, main key stratum 2, water-conducting channel 4, goaf 5, coal seam 6.

[0090] Step S1: Obtain the mining height M = 4m of the working face in the mining area, the original rock stress σ = 11 Mpa of the mining area, the distance D1 = 54.2m between the upper aquifer and the coal seam, and the distance D2 = 20m between the lower aquifer and the coal seam.

[0091] Collect coal and rock samples from the mining area, and use rock mechanics experiments to test the bulk modulus K, shear modulus G, compressive strength σ c , and rock density ρ of the coal and rock samples to be measured, which are the physical parameters of the coal body and each layer of rock stratum as shown in Table 1.

[0092] Table 1 Physical parameters of the coal body and each layer of rock stratum

[0093]

[0094] Step S2: Based on the mining height M = 4m of the working face obtained in Step S1 and the physical parameters of the coal body and each layer of rock stratum in Table 1, and with the help of 3DEC numerical simulation software, establish a numerical simulation model for the development of the water-conducting channel, and obtain the height h = 47m of the water-conducting channel generated from bottom to top in the overlying strata of the working face; use the calculation formula for the protective layer thickness in the "Code for the Reservation of Coal Pillars for Buildings, Water Bodies, Railways and Main Shaft Roadways and Coal Mining under Pressure" to calculate the protective layer thickness. Among them, the rock stratum below the upper aquifer in Table 1 is a medium-hard rock stratum, and the thickness of the cohesive soil layer at the bottom of the loose layer is greater than the mining height M = 4m, so the protective layer thickness is calculated using d = 3M, and the seepage distance d1 = 12m of the water in the upper aquifer is obtained; the rock stratum below the lower aquifer is a medium-hard rock stratum, and the thickness of the cohesive soil layer at the bottom of the loose layer is less than the mining height M = 4m, so the protective layer thickness is calculated using d = 4M, and the penetration distance d2 = 16m of the water in the lower aquifer is obtained.

[0095] Step S3: Based on the physical parameters of the coal body and each layer of rock in Table 1, and with the help of the key stratum discrimination software KSPB, it is obtained that the distance D3 from the main key stratum to the coal seam is 35.6 m, and the thickness of the main key stratum is d3 = 10.5 m. Compare the distance D3 from the main key stratum to the coal seam with the distances D1 and D2 from the upper and lower aquifers to the coal seam. Among them, D1 = 54.2 m, D2 = 20 m, D3 = 25.3 m. It is obtained that the distance D3 from the main key stratum to the coal seam is greater than the distance D2 from the upper aquifer to the coal seam and less than the distance D1 from the upper aquifer to the coal seam, that is, D2 < D3 < D1. Determine that the main key stratum and the double-aquifer structure are the middle main key stratum - upper and lower unidirectional double-aquifer structure.

[0096] Step S4: Based on the physical parameters of the coal body and each layer of rock in Table 1, compare the height of the water-conducting channel with the distance from the upper aquifer to the coal seam, the distance from the main key stratum to the coal seam, and the parameters of the thickness of the main key stratum. Among them, h = 47 m, D1 = 54.2 m, D2 = 20 m, D3 = 35.6 m, d3 = 15.5 m, d1 = 12 m. It is obtained that the height of the water-conducting channel is greater than the distance from the main key stratum to the coal seam and greater than the distance from the lower aquifer to the coal seam, and less than the distance from the upper aquifer to the coal seam, that is, D3 + d3 > h > D1 - d1. Furthermore, determine to adopt the protection method of upper protection - lower storage.

[0097] Subtract the thickness d1 of the protective layer of the upper aquifer from the distance D1 from the upper aquifer to the coal seam to obtain the water-conducting channel threshold h1, that is, h1 = D1 - d1 = 42.2 m.

[0098] Based on the mining height M = 4 m and the physical parameters of the rock strata in Table 1, and with the help of the 3DEC numerical simulation software, establish a development model of the water-conducting channel in the overlying strata under different packing rates, and obtain the development height of the water-conducting channel under different packing rates, as shown in Table 2.

[0099] Table 2 Development height of water-conducting channel under different packing rates

[0100]

[0101] According to the development height of the water-conducting channel under different packing rates in Table 2, the linear relationship between the packing rate and the height of the water-conducting channel is y = 0.8744 - 0.00673x, where y is the packing rate and x is the water-conducting channel threshold h. Substitute the water-conducting channel threshold h1 = 42.2 into y = 0.8744 - 0.00673x to obtain the optimal packing rate of 59%.

[0102] Therefore, the present invention adopts the above-mentioned method for protecting and utilizing water resources under the mining variation of different double-aquifer structures, realizing the coordinated development of coal resource development and comprehensive water resource protection and utilization in the mining area.

[0103] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit them. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions of the present invention or make equivalent replacements, and these modifications or equivalent replacements cannot make the modified technical solutions deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A method for protecting and utilizing water resources under mining variations of different double aquifer structures, characterized in that: The following steps are involved: Step S1, according to the geological characteristics of the two aquifers of the Jurassic Zhiluo Formation and the Cretaceous Luohe Formation above the longwall coal mining working face during the development of the Huanglong Jurassic coalfield, the mining height M of the coal mining working face, the distance D1 of the upper aquifer from the coal seam, and the distance D2 of the lower aquifer from the coal seam are obtained, wherein, in the double aquifers of the formation, the aquifer with a smaller distance from the aquifer to the surface is defined as the upper aquifer, and the aquifer with a larger distance from the aquifer to the surface is defined as the lower aquifer; the physical parameters of the coal body and each rock layer are obtained by rock mechanics test, and the original rock stress σ of the rock is measured by hydraulic fracturing method; Among them, the physical parameters of the coal body and each rock layer include rock density ρ, shear modulus G, bulk modulus K and compressive strength σ c ; Step S2, based on the data obtained in step S1, a three-dimensional numerical simulation model is established in the 3DEC numerical simulation software to obtain the height h of the water-conducting channel generated from bottom to top in the overlying rock formation of the working face; the protective layer thickness d1 of the upper aquifer and the protective layer thickness d2 of the lower aquifer are calculated using the protective layer thickness calculation formula in the "Specifications for Coal Pillar Retention and Coal Compressed Mining of Buildings, Water Bodies, Railways and Main Wells and Lanes"; Step S3, based on the physical parameters of the coal body and each rock layer in step S1, with the help of key layer identification software KSPB, obtain the distance D3 between the main key layer and the coal seam, and use the stratigraphic columnar diagram to obtain the thickness d3 of the main key layer; By comparing D1, D2 and D3, the positional relationship between the main key layer structure and the upper and lower aquifers is determined, including the following three types: When D1<D3, it is an upper main key layer-lower group vulnerable double aquifer structure, that is, the main key layer is located above the upper aquifer and has no protective effect on the double aquifer; When D1>D3>D2, it is a median main key layer-upper and lower unidirectional double aquifer structure, that is, the main key layer is located between the upper and lower aquifers, and plays a unidirectional protective role for the upper aquifer, but has no protective effect on the lower aquifer; When D3<D2, it is a lower main key layer-upper group protective double aquifer structure, that is, the main key layer is located below the lower aquifer and has a protective effect on both aquifers; Step S4: According to the spatial relationship between the aquifer and the main key layer and the different protection methods, the following five water resource protection and utilization methods are designed: Upper storage-lower storage method: The height of the water channel is greater than the thickness of the protective layer. The upper and lower aquifers are connected by the water channel. An artificial dam and a coal pillar dam are built to block the goaf, so that the goaf is constructed into an underground reservoir, and the water channel is used to divert water to the underground reservoir for storage; Upper blocking-lower storage method: The water diversion channel penetrates the lower aquifer without affecting the upper aquifer. The water-blocking property of the upper protective layer is used to block the loss of water in the upper aquifer. At the same time, the water diversion channel is used to divert the water flow of the lower aquifer to the underground reservoir for storage. Upper protection and lower storage method: The water channel is developed to the inner part of the protective layer of the upper aquifer, and the goaf is filled with waste rock to protect the upper aquifer by lowering the water channel. At the same time, the water channel is used to divert the water from the lower aquifer to the underground reservoir for storage; Upper blocking-lower protection method: The water channel is developed to the inside of the protective layer of the lower aquifer, without affecting the upper aquifer. The water barrier of the upper protective layer is used to block the loss of water in the upper aquifer, and gangue is used to fill the goaf, so as to protect the lower aquifer by lowering the water channel; Upper-lower blocking method: The water channel does not affect the stability of the upper and lower aquifers, and the water-blocking properties of the upper and lower protective layers are used to prevent water loss; Step S5, determining a specific protection method according to the main key layer structure type, the water channel height h, and the thicknesses d1 and d2 of the upper and lower protective layers; In the case of the upper main key layer-lower group vulnerable double aquifer structure, the protection method is determined as follows: When D1<h, the water-conducting channel caused by mining activities develops above the upper aquifer, that is, the upper and lower aquifers are connected, and the upper storage-lower storage method is adopted; When D1>h>D1-d1, the water channel caused by mining activities develops inside the protective layer of the upper aquifer and spreads to the protective layer of the upper aquifer, and the upper protection-lower storage method is adopted; When D2<h<D1-d1, the water conduction caused by mining activities develops between the lower aquifer and the upper aquifer protection layer, and the upper blocking-lower storage method is adopted; When D2>h>D2-d2, the water channel caused by mining activities affects the protective layer of the lower aquifer, and the upper resistance-lower protection method is adopted; When h<D2-d2, the water conduction caused by mining activities develops below the lower protective layer, and the upper resistance-lower resistance protection method is adopted; In the case of the median main key layer - upper and lower unidirectional double aquifer structure, the protection method is determined as follows: When D3+d3<h, the water channel caused by mining activities will penetrate the main key layer, and the main key layer cannot be used as a bearing structure to protect the upper aquifer. The upper storage-lower storage method is adopted; When D3+d3>h>D1-d1, the water channel caused by mining activities develops inside the protective layer of the upper aquifer, and the main key layer is not broken and still has a bearing function, so the upper protection-lower storage method is adopted; When D2<h<D1-d1, the water channel develops between the upper aquifer protection layer and the lower aquifer. The upper aquifer uses the protection layer to block the water channel and the aquifer, and the lower aquifer uses the underground reservoir to store water, adopting the upper blocking-lower storage method. When D2>h>D2-d2, the water-conducting channel develops to the inside of the protective layer of the lower aquifer, and the upper-blocking-lower-protecting method is adopted; When h<D2-d2, the water channel develops below the lower protective layer, and the upper resistance-lower resistance method is adopted; In the case of a lower main key layer-upper protective double aquifer structure, the protection method is determined as follows: When h>D3+d3, the water channel caused by mining activities penetrates the main key layer, and the main key layer cannot be used as a bearing structure, so the upper storage-lower storage method is adopted; When D2-d2<h<D3+d3, the water channel develops to the inside of the protective layer of the lower aquifer, and the main key layer is not broken and still has a bearing function, so the upper resistance-lower protection method is adopted; When D2-d2>h, the water-conducting channel develops below the protective layer of the lower aquifer, and the protective layer is used to block water loss to achieve groundwater protection, using the upper-lower-blocking method.

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