Process and effect evaluation method for top section of modified Ordovician limestone confined aquifer

Abstract

The invention discloses a process and effect evaluation method for a top section of a modified Ordovician limestone confined aquifer, and the method comprises the steps: analyzing, studying and judging the hydrogeological conditions of a mine, analyzing the water disaster factors of a treatment range or region, and calculating a water inrush coefficient, so as to facilitate the arrangement of a scheme; a water-bearing layer of the project is thoroughly modified into a water-resisting layer, so that the laneway project located at the layer is in a water-free state; a full-coverage three-dimensional arrangement mode that multiple layers of horizontal holes and top-lifting layer-penetrating holes are combined is adopted, an upper layer and a lower layer are staggered and distributed in a plum blossom shape, drilled holes are formed in multiple layers in a three-dimensional mode, and multiple layers of bedding horizontal holes and layer-penetrating inclined holes are formed in a combined mode. The technical method and route for modifying the top layer of the high-pressure-bearing Ordovician aquifer into the water-resisting layer through full-space complete grouting are achieved, the production technical problem is solved, and the domestic technical blank is filled up.

Description

Technical Field

[0001] The present invention belongs to the technical field of coal mine floor water hazard prevention and control, and more specifically relates to a process for modifying the top section of an Ordovician limestone confined aquifer and a method for evaluating its effect. Background Art

[0002] The hydrogeological conditions in various regions vary greatly, and the mining methods are unique. There are also significant differences in the purpose of treatment, specific requirements and quality standards. In the past, the prerequisite for grouting reinforcement and modification was about 20 meters even if the coal seam floor aquifer was thin. It was mainly aimed at coal-bearing limestone aquifers with thin aquifer thickness. The reinforcement of the Ordovician limestone aquifer was mainly to eliminate the water-conducting channel. Even if it was used as an aquifer, it would still be an aquifer after reinforcement, and at most it could only reach the level of a weak aquifer or an extremely weak aquifer, and it could not meet the standards of an aquifer at all. In addition, the modified thickness is usually around 30 meters. Especially under the condition of an extremely thin aquifer, the shaft and tunnel engineering is even directly arranged in the rock layer after grouting reinforcement and modification. After the effectiveness of similar domestic projects has been tested, the target layer can basically only be modified into a weak aquifer, and usually multiple injections are required to achieve a single-hole water yield of less than 10m 3 / h standard. Most projects only need to reach less than 10m 3 / h standard can meet the needs of engineering and safe mining. However, this patent not only meets the safety requirements, but also arranges the well and tunnel engineering in the target layer, completely realizing the aquiclude standard.

[0003] Therefore, the quality requirements for grouting modification are relatively higher. Some previous specifications and standards stipulated that the water inflow of the underground verification borehole after reinforcement should not exceed 10m 3 / h is sufficient. Clearly, neither engineering nor quality standards meet the current needs of some mines. Although the national industry standard (KA / T2-2023) was released in 2023 to provide a basis for the application of regional remediation technologies, the evaluation criteria for regional remediation effectiveness have yet to be established in a clear and systematic system. The evaluation of some projects is still insufficient and does not meet the needs of actual production.

[0004] It's easy to analyze that some mining areas have proposed evaluation methods based on permeability or single-hole water inflow. However, a single metric often fails to fully reflect the effectiveness and quality of regional flood control, potentially leading to biased evaluation results that lack comprehensiveness, rigor, and scientific accuracy. More seriously, insufficient attention to evaluation criteria can pose significant safety risks to mining. Given that the effectiveness and quality of regional control are directly linked to mine safety, we must prioritize the evaluation of surface-level control effectiveness and quality.

[0005] In summary, to date, there is a technical gap in the domestic deployment of shaft and tunnel engineering within the top section of the Ordovician limestone aquifer, which has been reinforced and modified by grouting. Some quality standards for regional governance are also relatively crude. There is a lack of clear and unified evaluation indicators and standards for achieving higher-quality, accurate evaluation. There is an urgent need to overcome the technical difficulties of deploying shaft and tunnel engineering within the top section of the Ordovician limestone aquifer, or other aquifers, after complete grouting reinforcement and modification. Furthermore, there is a need to improve the evaluation standards and indicators for the effectiveness and quality of surface governance, and to develop a comprehensive, scientific, and rational evaluation system to provide a scientific basis for coal mine water hazard management and ensure the technical support for mining safety. Summary of the Invention

[0006] In view of this, the present invention provides a process for modifying the top section of an Ordovician limestone confined aquifer and a method for evaluating its effect.

[0007] In order to achieve the above object, the present invention adopts the following technical solutions: A process for modifying the top section of an Ordovician limestone confined aquifer comprises the following steps: Step S1: Analyze and determine the hydrogeological conditions of the mine, analyze the water hazard factors in the treatment area or region, and calculate the water inrush coefficient to facilitate the scheme layout; Step S2: Completely transform the project's own aquifer into an aquiclude, rendering the shafts and tunnels water-free. Step S3: adopt a full coverage three-dimensional arrangement method combining multiple layers of horizontal holes with top-penetrating holes, with the upper and lower layers staggered in a plum blossom shape, multiple layers of three-dimensional drilling arrangement, and multiple layers of horizontal holes along the layers combined with inclined holes through the layers.

[0008] Furthermore, in step S1, water hazard factors include: water source, channel, and water volume; water source factors are the root cause of water hazards, mainly thin limestone aquifers and Ordovician limestone aquifers; channel factors mainly include three types: faults, collapse columns, and fissures; water volume factors are related to factors such as the thickness, burial depth, water richness, recharge conditions, and water level of the water hazard aquifer; and the water inrush coefficient of the mined coal seam or project is calculated.

[0009] Furthermore, in step S2, it is necessary to ensure that the top and bottom plates and surrounding areas of the project are not threatened by the Ordovician limestone pressure water, and the top and bottom plates and surrounding areas of the project are correspondingly reinforced and modified to form a safe aquifer; grouting modification technology is used to inject cement, fly ash, and clay slurry into the Ordovician limestone fissures and karst runoff channels where raw water is stored, completely displacing the water and transforming the water-rich aquifer into an aquifer; at the same time, an aquifer curtain of a certain thickness is constructed outside the project to ensure that the project is protected from the threat of the Ordovician limestone pressure aquifer.

[0010] Furthermore, the Ordovician limestone confined aquifer is completely or thoroughly grouted into an aquiclude, clay slurry is selected as the grouting material and the corresponding grouting process is used, and the layer spacing and hole spacing are determined according to the thickness of the safe aquiclude and the slurry diffusion radius.

[0011] Furthermore, a small hole spacing arrangement method is adopted with a horizontal branch hole spacing of 20 to 30 meters and a vertical layer spacing of 20 to 30 meters, and the arrangement orientation is perpendicular to or obliquely crosses the development orientation of the main structure of the project.

[0012] Furthermore, the vertical layers are set to three layers, the first layer is 15 to 20 meters away from the top surface of the Aohui, the second layer is 35 to 45 meters away from the top surface of the Aohui, and the third layer is 60 to 70 meters away from the top surface of the Aohui.

[0013] Furthermore, the grouting process is as follows: using a low-density slurry with a specific gravity of 1.1~1.5, and the grouting pressure is 2~3 times the hydrostatic pressure of the Ordovician ash aquifer; using a ground grouting station process, performing three-stage mixing and three-stage 150-mesh sieve filtration, and selecting a grouting process with small and medium pump volumes.

[0014] Furthermore, it also includes full-process and full-space three-dimensional grouting modification and process effect verification, as follows: The water pressure test and top hole drilling method are combined to verify the process effect of grouting modification quality; The distance between the through-layer top-lifting holes is 200~250 meters for the bottom layer, and 100~150 meters for the second and third layers. Verification distance: A short distance of 50 to 100 meters is used for verification, and a water pressure test is conducted. A water pressure test is conducted every 100 meters for the bottom layer, and every 50 to 80 meters for the middle layer and the top layer. The water pressure test time is not less than 4 hours to ensure the high quality of the grouting modification. Water pressure test: When the test pressure is not less than 2 to 3 times the hydrostatic pressure of the Ordovician ash aquifer, and the stabilization time is not less than 30 minutes, and the water pressure pump volume reaches 30 to 60 L / min, the calculated water absorption rate of the injection section is q < 0.01 L / (min·m·m), it is qualified, otherwise grouting is carried out.

[0015] A method for evaluating the effect of a process for modifying the top section of an Ordovician lime confined aquifer includes the following four aspects: (1) Changes in aquifer permeability, as measured by the hydraulic conductivity and permeability of the target aquifer; (2) Changes in aquifer water levels; (3) Changes in the water-richness of the aquifer; (4) Increase in the thickness of the aquiclude.

[0016] Furthermore, the evaluation of the modification effect also includes the evaluation of two treatment methods: ground and underground; the underground evaluation indicators include single-hole water yield, water level and permeability coefficient; the ground standard evaluation indicators include permeability, unit water yield and water level.

[0017] The beneficial effects of the present invention are: This invention pioneered the technical method and route for converting the top layer of a highly pressurized Ordovician limestone aquifer into an impermeable layer through full-space grouting, overcoming production technical difficulties and filling a domestic technological gap. It provides a systematic technical construction method for converting thick, water-rich aquifers into a completely impermeable layer, setting a viable and illustrative example for similar projects in China.

[0018] Secondly, the core principles and technical essence of regional remediation technology are revealed: remediation objectives are achieved by reducing and radically modifying the permeability, water-richness, and water level of aquifers. This cleverly transforms the evaluation of the effectiveness and quality of regional remediation technology into a determination of aquifer permeability and water-richness, clarifying regional remediation evaluation criteria, simplifying the technical evaluation process, and improving the evaluation system. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are merely embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying any creative work.

[0020] Figure 1 Flow chart of the method of the present invention.

[0021] Figure 2 It is the vertical level layout diagram of the present invention.

[0022] Figure 3 This is a schematic diagram of the layer-by-layer verification and annotation of the present invention.

[0023] Figure 4 Schematic diagram of comprehensive grouting modification in the entire space from the top of the Ordovician gray aquifer to 74 meters below. DETAILED DESCRIPTION

[0024] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0025] refer to Figure 1 The present invention discloses a process for modifying the top section of an Ordovician limestone confined aquifer, comprising the following steps: Step S1: Analyze and assess the hydrogeological conditions of the mine, analyze the water hazard factors within the control area or region, and calculate the water inrush coefficient to facilitate planning. Water hazard factors include water source, channel, and water volume. Water source factors are the root cause of water hazards and are primarily thin limestone aquifers and Ordovician limestone aquifers. Channel factors primarily include faults, collapse columns, and fissures. Water volume factors are related to the thickness, depth, water richness, recharge conditions, and water level of the water-hazard aquifer. The water inrush coefficient for the mining coal seam or project is calculated.

[0026] Step S2: The project is arranged 20-30 meters below the top of the Ordovician ash confined aquifer. The project is threatened by Ordovician ash confined water on all sides and the top and bottom six sides, and is subject to Ordovician ash water pressure of 4.45MPa. The project's own aquifer is completely modified into an aquiclude, so that the shaft itself is in a water-free state; to ensure that the project's top plate, surroundings and bottom plates are not threatened by Ordovician ash confined water, the top, bottom and surrounding areas of the project are reinforced and modified accordingly to form a safe aquiclude with a thickness of 54 meters; in order to protect the surrounding area of ​​the project from water threats, the entire space from the top of the Ordovician ash aquifer to 74 meters below is fully grouting modified to ensure that the project is free from the threat of the Ordovician ash aquifer. See Figure 4 .

[0027] Grouting modification technology is used to inject cement, fly ash, clay slurry and other slurries into the Ordovician ash fissures and karst runoff channels where raw water is stored, completely replacing the water and transforming the water-rich aquifer into an impermeable layer; at the same time, an impermeable layer curtain of a certain thickness is constructed outside the project to ensure that the project is protected from the threat of the Ordovician ash pressure aquifer.

[0028] Step S3: adopt a full coverage three-dimensional arrangement method combining multiple layers of horizontal holes with top-penetrating holes, with the upper and lower layers staggered in a plum blossom shape, multiple layers of three-dimensional drilling arrangement, and multiple layers of horizontal holes along the layers combined with inclined holes through the layers.

[0029] Adopt full-space multi-layer three-dimensional modification technology, accurately control the layer position and trajectory throughout the whole process, implement three-dimensional high-quality process management throughout the whole cycle, ensure quality layer by layer, implement three-dimensional fine grouting modification, and apply three-dimensional differentiated grouting technology to achieve integrated operations of exploration, modification, verification and replenishment.

[0030] Engineering technical parameter selection and influencing factors: ⑴ Based on the comprehensive analysis of engineering geological and hydrogeological conditions, the water-hazard aquifer and its water hazard factors are identified, the water inrush coefficient is calculated, the treatment layer, the thickness of the modified aquifer, the hole spacing, the grouting material, the grouting process and the grouting parameters are determined, and the scheme is arranged.

[0031] The main water hazard factors of this project are the thick Ordovician limestone confined aquifer as the water source, as well as the cracks developed in the Ordovician limestone strata and the interconnected karst runoff channels.

[0032] The water pressure on the project's baseplate was calculated based on the project's elevation and the water level of the Ordovician ash aquifer. The required safety barrier thickness around the project and on the baseplate was calculated using the water inrush coefficient formula (M=P / Ts), with the water inrush coefficient (Ts) set at 0.06. Considering the characteristics, fissure development, and pressure of the Ordovician ash aquifer, the aquifer needed to be completely or thoroughly grouted into an aquiclude. Clay slurry was selected as the grouting material, along with the appropriate grouting process. The interlayer and hole spacing was determined based on the safety barrier thickness and the slurry diffusion radius.

[0033] The selection of strata is related to the following factors: the floor elevation of the designed coal seam, coal thickness, coal seam burial depth, aquifer water level, aquifer thickness, aquifer water richness, aquiclude thickness, water inrush coefficient, mining method, engineering quality requirements, grouting materials and processes, etc.

[0034] The determination of hole spacing is affected by the following factors: aquifer thickness, water richness, water level, aquiclude thickness, grouting material, type and scale of exposed structures in the area, complexity of mine hydrogeological conditions, engineering properties and quality requirements.

[0035] A full-coverage, three-dimensional arrangement combining multiple layers of horizontal holes with top-penetrating holes is adopted, with the upper and lower layers staggered in a plum blossom-like arrangement. The design employs a small hole spacing arrangement with a horizontal branch hole spacing of 20 to 30 meters and a vertical layer spacing of 20 to 30 meters. The arrangement is oriented perpendicularly or obliquely through the main structural development of the project. This three-dimensional arrangement, combining multiple layers of horizontal holes with top-penetrating holes, takes into account the advantages of both horizontal and inclined holes, achieving complementary advantages and effectively resolving the difficult problem of blind spots in grouting reinforcement and modification, such as horizontal and vertical cracks between different horizontal layers and between horizontal branch holes on the same layer, as well as subtle and isolated cracks. This creates a three-dimensional, multi-layer, three-dimensional grouting reinforcement and modification effect with full coverage without blind spots.

[0036] This design enhances the precise and detailed control of layer positions and drilling trajectories (only the top hole needs to be constructed in the top layer), and improves the grouting reinforcement effect to ensure high-quality modification of the project.

[0037] The specific layout is as follows: the first layer is 15~20 meters away from the top of the Aohui, the second layer is 35~45 meters away from the top of the Aohui, and the third layer is 60~70 meters away from the top of the Aohui. Figure 2 The bottom layer mainly solves the problem of sealing large cracks and curtain interception; the second layer not only fills and reinforces cracks, but also focuses on the treatment of small cracks and effect inspection; the third layer of holes is mainly used for verification and refilling, achieving a layer-by-layer progressive effect, see Figure 3 and Figure 4 .

[0038] Through-layer top-selecting hole: construct a top-selecting through-layer verification hole 200~250 meters at the bottom layer, and construct a through-layer top-selecting verification hole every 100~150 meters on the second and third layers, and supplement grouting modification, and carefully control the treatment layer position, drilling trajectory and modification quality.

[0039] Grouting materials should be clay cement slurries with excellent permeability, fluidity, stability, impermeability, durability, and environmental friendliness. Slurry selection must ensure it can penetrate and completely fill small cracks, ensuring proper slurry diffusion and grouting modification quality.

[0040] The grouting process of the present invention is as follows: a low-specific-gravity slurry with a specific gravity of 1.1-1.5 is used, and a grouting pressure is 2-3 times the hydrostatic pressure of the Ordovician ash aquifer; a ground grouting station process is adopted, three-stage stirring and three-stage 150-mesh sieve filtration are performed, and a grouting process with a small to medium pump volume (500-90 L / min) is selected.

[0041] The present invention also includes full-process and full-space three-dimensional grouting modification and process effect verification, as follows: The grouting modification and process verification technology, combining through-layer top drilling with short-section water pressure testing, constitutes a truly innovative and exceptional combination. This technology integrates filling grouting reinforcement, supplementary grouting reinforcement modification, and verification. It effectively addresses the challenges of previous work, such as poor filling reinforcement quality due to micro-cracks and poor connectivity, reinforcement modification of horizontal and vertical cracks, and the easy omission of hidden, isolated, and closely connected micro-water-conducting channels.

[0042] The water pressure test and top hole drilling method are combined to verify the process effect of grouting modification quality; The distance between the through-layer top-lifting holes is 200~250 meters for the bottom layer, and 100~150 meters for the second and third layers. Verification distance: A short distance of 50 to 100 meters is used for verification, and a water pressure test is conducted. A water pressure test is conducted every 100 meters for the bottom layer, and every 50 to 80 meters for the middle layer and the top layer. The water pressure test time is not less than 4 hours to ensure the high quality of the grouting modification. Water pressure test: When the test pressure is not less than 2 to 3 times the hydrostatic pressure of the Ordovician ash aquifer and the stabilization time is not less than 30 minutes, and the water pressure pump volume reaches 30 to 60 L / min, the calculated water absorption rate of the injection section is q < 0.01 L / (min·m·m), it is qualified, otherwise grouting is carried out.

[0043] The high-quality, high-precision, high-standard multi-coordinated grouting modification technology for extremely thick aquifers is adopted. The construction and technical requirements are as follows: Construction Sequence: To ensure modification quality, horizontal branch holes in different layers should be constructed from the bottom up, starting with the lowest layer, then gradually moving up to the upper layers, and finally to the top layer. Horizontal branch holes in the same layer should be constructed at intervals. The upper layer holes serve as both grouting modification holes and as a test and supplementary injection hole for the grouting effect of the lower layer. Progressive reinforcement and verification are performed layer by layer to ensure overall modification quality.

[0044] Grouting Process and Parameter Control: For the bottommost hole, grouting should be performed at a medium to high pump rate (above 520 L / min), initially to quickly seal large cracks. For the upper two holes and the three surrounding holes, medium to low pump rates (390-90 L / min) and low specific gravity (1.1-1.6) should generally be used to thoroughly fill the small and micro-cracks that require grouting. In the case of large cracks, the pump rate and specific gravity can be adjusted based on the specific circumstances.

[0045] Differentiated countermeasures are adopted for the spacing between general sections and abnormal sections: on the basis of ensuring the normal hole spacing in general sections, measures are taken to double-encrypt the plane and section hole spacing in areas with dense structural development, the axis of the anticline, areas with significant steep changes in inclination, contour line bends, and areas prone to grouting during grouting.

[0046] Quality process control and final hole control complement each other. Loss grouting, water pressure grouting, verification and reinforcement grouting, final hole grouting and grouting in key areas are combined and supplemented with each other, and key grouting is implemented in key areas: we must pay attention to the refined management of the grouting process and the precise control of the final hole of drilling.

[0047] The construction and grouting of branch holes strictly adhere to a meticulous approach of "one hole, one design, one hole, one summary, and one analysis," ensuring rapid analysis and efficient problem resolution when encountering unique situations. Given the complex fissures in the tectonic zone, grouting results in small fissures are often unsatisfactory. Therefore, grouting operations should begin with a low pumping rate and be maintained for at least 72 hours. Based on this, pumping rates can be flexibly adjusted based on actual site conditions. After drilling is completed, a comprehensive analysis and summary must be conducted to provide valuable reference and lessons for subsequent branch hole construction.

[0048] Through detailed analysis of process data, including key indicators such as rock powder identification, gamma value determination, drilling speed recording, drilling time monitoring, leakage and water level changes, we ensure that fine, high-quality and high-precision quality control standards are achieved.

[0049] Combining process effect verification with specialized effect verification: Verification is not only an important means of testing the quality and effectiveness of grouting modification, but also the primary basis for evaluating its quality and effectiveness. It also serves as an extension and supplement to grouting modification. Effectiveness verification primarily involves routine process verification, specialized effectiveness verification, and stope verification. Stope verification is the most objective, convincing, and final, most effective method. However, due to the inherent risk of water inrush, which leaves no escape route or remedial options, verification during the stope phase is not recommended. Therefore, routine process verification and specialized effectiveness verification are particularly important and indispensable.

[0050] Daily process verification utilizes a variety of methods, including water pressure testing before and after grouting, interval construction of branch holes within the same layer, verification of the upper layer against the lower layer between upper and lower layers, verification of the rear section of the same branch hole against the front section, rock dust identification, and verification of top-penetrating holes at specified intervals. Furthermore, dedicated verification holes are constructed for pumping tests or downhole drilling to further verify construction quality and perform necessary supplemental grouting and modification. These comprehensive measures enable real-time performance inspection and specialized verification throughout the entire process and space, enabling timely identification and resolution of quality issues.

[0051] The selection of special effect verification areas covers the following situations: ① located in the area of ​​the anticline axis and the area where the rock formation dip changes steeply; ② the area with abnormal gamma value; ③ the area with large grouting volume and low elevation; ④ the area without leakage for a long distance; ⑤ the area with dense structural intersection; ⑥ the area with hydrogeological anomalies (covering the known structural areas and the structural anomalies discovered by exploration); ⑦ the area where the bottom plate bulges or the stratum is broken during the grouting process; ⑧ the area with hydrological anomalies such as high water level and high water temperature.

[0052] In summary, through meticulous design of technical parameters such as technical thinking, layout, hole spacing, grouting layer location, grouting material selection, grouting process, grouting density, and grouting pressure, combined with collaborative grouting modification technologies across multiple aspects, including layer location control, process control, effect verification, and grouting process control, we achieved precise and accurate control throughout the entire cycle, space, and process. With high quality, high precision, and high standards as the core, we conducted a comprehensive and thorough grouting modification of the extremely thick aquifer (70 meters), ensuring significant results in every grouting modification step.

[0053] The present invention also provides a method for evaluating the effect of the process of modifying the top section of the Ordovician limestone confined aquifer. The principle and essence of regional grouting modification lies in grouting modification and reinforcement of the bottom plate aquifer. Specifically, through grouting technology, the grouting liquid replaces the water in the aquifer, thereby strengthening the weak areas in the rock formation and transforming the incomplete section into a complete section. At the same time, the hydrogeological conditions also become clear from being vague. With the help of regional governance technology, the aquifer can be modified into a weak aquifer, or even a relatively impermeable layer, and ideally it can even be completely transformed into an impermeable layer. From the perspective of hydrogeology, this process is mainly reflected in: (1) Changes in the permeability of the aquifer, which is measured by the permeability coefficient and water permeability of the target aquifer. After modification and reinforcement, the permeability of the rock layer is significantly reduced, the hydraulic connection of the aquifer changes from tight to loose, the water runoff condition changes from smooth to poor, and even completely blocks the water runoff, reaching a state of no runoff. The water blocking effect is significant and the hydraulic connection is extremely poor.

[0054] (2) Changes in aquifer water level: Due to grouting reinforcement and modification, the water permeability resistance of the aquifer increases significantly, the vertical and lateral recharge conditions become extremely poor, and the runoff process consumes a lot of energy. After grouting modification and reinforcement, the aquifer water level (water pressure) is significantly lower than before modification, and even the water level (water pressure) is mostly or completely reduced. The water level is significantly different from the original water level of the target layer. The aquifer changes from a unified hydraulic connection and water level (water pressure) to a lack of unified hydraulic connection. The water level varies in different sections within the modified area.

[0055] (3) Changes in the water-richness of the aquifer; the aquifer changes from a water-rich state to a water-poor state, or even a waterless and adiabatic state.

[0056] (4) The thickness of the waterproof layer increases, and the thickness of the waterproof layer increases after modification.

[0057] The effects of the full set of technical processes in the ground area also include: (5) the integrity and strength of the aquiclude are strengthened and improved.

[0058] The aquiclude is transformed from incomplete to complete, eliminating potential water-conducting structural channels, while strengthening the integrity and strength of the aquiclude and improving its ability to resist water pressure.

[0059] Through in-depth analysis of the principles of regional grouting modification, we can clearly observe that regional treatment or base grouting modification primarily manifests as significant changes in aquifer permeability and water-yielding properties. The modified aquifer's permeability is significantly weakened, hydraulic connections become poor or even completely severed, and water-yielding properties are correspondingly weakened or even completely eliminated. A uniform hydraulic connection no longer exists, and water level differences become noticeable or disappear completely. Therefore, the effectiveness and quality evaluation indicators of regional treatment or base grouting modification primarily focus on the assessment of aquifer permeability, water-yielding properties, and water level.

[0060] The evaluation criteria are based on the permeability and water yield of aquifers. Hydraulic indicators for aquifer permeability include the permeability coefficient or permeability rate, as well as water level (water pressure), while indicators for aquifer water yield are unit yield and per-pore yield. Therefore, the evaluation indicators for regional remediation effectiveness can be summarized into the following three aspects: permeability; water level; and water yield. The evaluation criteria include permeability coefficient or permeability rate, unit yield or per-pore yield, and aquifer water level.

[0061] Based on hydrogeological conditions such as the elevation of the mined coal seam, the thickness of the aquiclude, and the water level (water pressure) of the aquifer, water hazard management can be divided into two categories: one is when the water inrush coefficient is between 0.06 and 0.1, and the other is when the water inrush coefficient is greater than 0.1. For the first category, the focus of management and modification is to detect and reinforce the aquifer that affects coal seam mining, as well as the potential hidden water-conducting structures between the mined coal seam and the aquifer, and the potential weak zones in the rock formation during the mining process through grouting. This aims to eliminate potential water inrush risks, improve the integrity and compressive strength of the aquiclude between the mined coal seam and the aquifer, reduce the permeability and water-richness of the aquifer, and thus transform the aquifer into a weak aquifer or even an aquiclude.

[0062] In the second case, a more comprehensive aquifer modification and treatment is required. In this case, the thickness of the modified aquifer, transformed into an impermeable layer, must be included in the total aquitard thickness, and the aquifer's properties must be completely transformed into an impermeable layer. Some wells and tunnels may even need to be located within this layer. Clearly, the modification and treatment requirements for the second case are more stringent than those for the first. Of course, in either case, the higher the quality of the reinforcement, the safer the mining process.

[0063] Therefore, the standards are subdivided into these two cases, and each case is further subdivided into two treatment methods: surface and underground. The underground evaluation indicators include the water inflow per single hole, water level, and permeability coefficient; while the surface standard evaluation indicators include the water permeability rate (i.e., the permeability coefficient), the unit water inflow, and the water level. The evaluation indicators have changed from single indicators to multiple comprehensive indicators, and the evaluation criteria have changed from a single evaluation point to the evaluation of the entire treatment area. Whether in terms of treatment indicators or evaluation methods, a more perfect, scientific, and reasonable improvement has been achieved.

[0064] For the evaluation criteria, see Table 1: Table 1 For the case where the water inrush coefficient 0.06 < Ts < 0.1 Surface standard: (1) The water permeability rate is less than 0.01 L / min.m.m (1 lu) or the permeability coefficient is less than 10 -5 cm / s (slightly permeable); (2) The unit water inflow is less than 0.1 L / s.m (extremely weak water-richness); (3) The water level should be much lower than the water level of the treatment horizon, with a significant water level difference and different water levels in boreholes at each section.

[0065] Underground standard: (1) The water inflow per single hole is less than 10 m 3 / h or the unit water inflow is less than 0.1 L / s.m (extremely weak water-richness); (2) The water level should be much lower than the water level of the treatment horizon, with a significant water level difference and different water levels in boreholes at each section; (3) The permeability coefficient 10 -6 ≤ k < 10 -5 (slightly permeable).

[0066] For the case where the water inrush coefficient Ts > 0.1 Surface standard: (1) The water permeability rate is less than 0.001 L / min.m.m (0.1 lu) or the permeability coefficient is less than 10 -6 cm / s (extremely slightly permeable); (2) The unit water inflow is less than 0.001 L / s.m (extremely weak water-richness - impermeable layer); (3) The water level should be much lower than the water level of the treatment horizon, with an extremely significant water level difference and different water levels in boreholes at each section or even no water and no water level.

[0067] Underground standard: (1) The water inflow per single hole is less than 6 m 3 / h or there is no water or the unit water inflow is less than 0.001 L / s.m (extremely weak water-richness - impermeable layer); (2) The water level should be much lower than the water level of the treatment horizon, with a significant water level difference and different water levels in boreholes at each section or even no water and no water level. (3) The permeability coefficient is less than 10 -6 cm / s (extremely slightly permeable).

[0068] After grouting reinforcement and modification, whether conducted through surface or underground verification, three key criteria must be met: water level, permeability coefficient (water permeability), and specific water yield (single-hole water yield). These three criteria complement and reinforce each other, forming a unified and interconnected standard system. Failure to meet any of these criteria indicates problems with the effectiveness and quality of regional remediation. First, the water level after modification should be significantly different from that before modification. If evaluation is based solely on single-hole water yield, specific water yield, or water permeability, and no significant water level drop is observed, this is not only inconsistent with actual conditions but also indicates that grouting reinforcement and modification has failed to effectively reduce water pressure, leading to unsatisfactory grouting reinforcement and modification results. Conversely, if the reinforcement and modification are effective, a significant drop in the water level will be the most direct indicator. Second, the water permeability after modification should meet or exceed the micro-permeability standard, or the permeability coefficient should meet or exceed the micro-permeability standard. Finally, the water-richness after modification should be extremely weak or even absent (aquiclude).

[0069] This standard system fundamentally, comprehensively, scientifically and rationally solves the problems of lack and singleness of evaluation standards for ground area management of coal mine water hazards.

[0070] This invention pioneered the technical method and route for converting the top layer of a highly pressurized Ordovician limestone aquifer into an impermeable layer through full-space grouting, overcoming production technical difficulties and filling a domestic technological gap. It provides a systematic technical construction method for converting thick, water-rich aquifers into a completely impermeable layer, setting a viable and illustrative example for similar projects in China.

[0071] Secondly, the core principle and technical essence of regional grouting modification technology are revealed: namely, achieving treatment goals by reducing and thoroughly modifying the permeability, water-richness, and water level of the aquifer. The study cleverly transforms the quality evaluation of regional grouting modification technology into a determination of the permeability and water-richness of the aquifer, clarifying the regional treatment quality evaluation criteria, simplifying the technical evaluation process, and improving the evaluation system.

[0072] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the various embodiments of the present invention.

Claims

1. A process for modifying the top section of an Ordovician limestone confined aquifer, characterized in that: The steps include: Step S1: Analyze and determine the hydrogeological conditions of the mine, analyze the water hazard factors in the treatment area or region, and calculate the water inrush coefficient to facilitate the scheme layout; Step S2: Completely transform the project's own aquifer into an aquiclude, rendering the shafts and tunnels water-free. Step S3: adopt a full coverage three-dimensional arrangement method combining multiple layers of horizontal holes with top-penetrating holes, with the upper and lower layers staggered in a plum blossom shape, multiple layers of three-dimensional drilling arrangement, and multiple layers of horizontal holes along the layers combined with inclined holes through the layers.

2. The process for modifying the top section of an Ordovician limestone confined aquifer according to claim 1, characterized in that: In step S1, water hazard factors include: water source, channel, and water volume; water source factors are the root cause of water hazards, mainly thin limestone aquifers and Ordovician limestone aquifers; channel factors mainly include three types: faults, collapse columns, and fissures; water volume factors are related to factors such as the thickness, burial depth, water richness, recharge conditions, and water level of the water hazard aquifer; calculate the water inrush coefficient of the mined coal seam or project.

3. The process for modifying the top section of an Ordovician limestone confined aquifer according to claim 2, characterized in that: In step S2, it is necessary to ensure that the top and bottom plates and the surrounding areas of the project are not threatened by the Ordovician limestone pressure water, and the top and bottom plates and the surrounding areas of the project are reinforced and modified accordingly to form a safe aquifer; using grouting modification technology, cement, fly ash, and clay slurry are injected into the Ordovician limestone fissures and karst runoff channels where raw water is stored, completely displacing the water and transforming the water-rich aquifer into an aquifer; at the same time, a certain thickness of aquifer curtain is constructed outside the project to ensure that the project is protected from the threat of the Ordovician limestone pressure aquifer.

4. The process for modifying the top section of an Ordovician limestone confined aquifer according to claim 3, characterized in that: The Aohui confined aquifer is completely or thoroughly grouting transformed into an aquiclude, clay slurry is selected as the grouting material and the corresponding grouting process is used, and the layer spacing and hole spacing are determined according to the thickness of the safe aquiclude and the slurry diffusion radius.

5. The process for modifying the top section of an Ordovician limestone confined aquifer according to claim 4, characterized in that: The horizontal branch hole spacing is 20~30 meters, and the vertical branch hole spacing is 20~30 meters. The arrangement direction is perpendicular to or obliquely crosses the development direction of the main structure of the project.

6. The process for modifying the top section of an Ordovician limestone confined aquifer according to claim 5, characterized in that: The vertical layers are set to three layers, the first layer is 15~20 meters away from the top surface of the Aohui, the second layer is 35~45 meters away from the top surface of the Aohui, and the third layer is 60~70 meters away from the top surface of the Aohui.

7. The process for modifying the top section of an Ordovician limestone confined aquifer according to claim 6, characterized in that: The grouting process is as follows: use a low-density slurry with a specific gravity of 1.1~1.5, and the grouting pressure is 2~3 times the hydrostatic pressure of the Ordovician ash aquifer; use a ground grouting station process, perform three-stage mixing and three-stage 150-mesh sieve filtration, and select a grouting process with small and medium pump volumes.

8. The process for modifying the top section of an Ordovician limestone confined aquifer according to claim 7, characterized in that: It also includes full-process and full-space three-dimensional grouting modification and process effect verification, as follows: The water pressure test and top hole drilling method are combined to verify the process effect of grouting modification quality; The distance between the through-layer top-lifting holes is 200~250 meters for the bottom layer, and 100~150 meters for the second and third layers. Verification distance: A short distance of 50 to 100 meters is used for verification, and a water pressure test is conducted. A water pressure test is conducted every 100 meters for the bottom layer, and every 50 to 80 meters for the middle layer and the top layer. The water pressure test time is not less than 4 hours to ensure the high quality of the grouting modification. Water pressure test: When the test pressure is not less than 2 to 3 times the hydrostatic pressure of the Ordovician ash aquifer, and the stabilization time is not less than 30 minutes, and the water pressure pump volume reaches 30 to 60 L / min, the calculated water absorption rate of the injection section is q < 0.01 L / (min·m·m), it is qualified, otherwise grouting is carried out.

9. A method for evaluating the effect of a process for modifying the top section of an Ordovician limestone confined aquifer, characterized in that: It includes the following four aspects: (1) Changes in aquifer permeability, as measured by the hydraulic conductivity and permeability of the target aquifer; (2) Changes in aquifer water levels; (3) Changes in the water-richness of the aquifer; (4) Increase in the thickness of the aquiclude.

10. The method for evaluating the effect of a process for modifying the top section of an Ordovician lime confined aquifer according to claim 9, characterized in that: The aquifer also includes the evaluation of two treatment methods: surface and underground; the underground evaluation indicators include single hole water yield, water level and permeability coefficient; the surface standard evaluation indicators include permeability, unit water yield and water level.

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