Karst water-rich metal deposit roof single-layer control dewatering method

Abstract

The application discloses a karst water-rich metal deposit roof single-layer control dewatering method, which comprises the following steps: S1, roof hydrogeological condition exploration; S2, drilling and grouting on the structural fissure zone and water-conducting fault; S3, leaving a waterproof ore pillar and avoiding water on the structural fissure zone and water-conducting fault; S4, carrying out stope dewatering; and S5, adopting the filling method for mining. The application utilizes the natural blocking effect of the water-resisting layer, combines the active prevention and control measures of grouting reconstruction and dewatering, and inhibits the occurrence of disasters, so that the water pressure cannot break through the artificial block such as the grouting curtain, or in the new balance state, the water pressure release cannot cause damage, thereby achieving the effective control of the underground water, and the application is very suitable for the case that the deposit hydrogeological conditions are relatively complex and the aquifer (zone) structure has certain differences in space.

Description

Technical Field

[0001] This invention relates to the field of single-layer controlled drainage technology for the roof of mineral deposits, and in particular to a single-layer controlled drainage method for the roof of karst water-rich metal deposits. Background Technology

[0002] Water inrush hazards induced by mining in karst mines where the ore body itself or the roof is an aquifer seriously threaten production and the lives of miners. The most widely used and successful water control method in metal mines is dewatering. This method involves draining groundwater from the aquifer to lower the water level below the mining level, eliminating the water hazard and allowing mining to proceed. Three main water control schemes are available: surface dewatering, underground dewatering, and a combination of surface and underground dewatering.

[0003] Surface dewatering: In the early stages of infrastructure construction, numerous specialized dewatering boreholes are drilled around the ore deposit, extending beyond the mid-mining zone. Deep well pumps are installed inside the boreholes to pump water, and the groundwater level is required to drop below the mid-mining zone before mining operations can commence. This method is simple in process, but the drilling costs are high, management is difficult, and long-term drainage expenses are substantial.

[0004] Underground dewatering: During the infrastructure construction phase, pre-grouting is mainly used to prevent groundwater intrusion and ensure the excavation of tunnels. After the underground drainage system is established, specialized dewatering tunnels and drainage holes are constructed. Mining operations resume once the groundwater level drops below the middle of the mining area. This scheme is simple in process and convenient in managing underground drainage projects, but due to the large drainage head, long-term drainage costs are high.

[0005] Combined dewatering: This involves a combination of surface and underground dewatering. Typically, surface dewatering holes are used initially to ensure smooth well excavation and remove large amounts of static water from the aquifer, saving time on subsequent underground drainage. Later, underground dewatering is the primary method for releasing groundwater. This approach is simple and convenient for both well excavation and underground drainage management, but it results in higher dewatering costs, difficulties in surface management, and long-term high drainage expenses.

[0006] The above three methods involve enormous amounts of mine drainage (350,000 m³ at the Konkola copper mine in Zambia). 3 / d, Chambishi copper mine 60,000 m³ 3 / d, Jinchuan International Musonny Mine, Democratic Republic of Congo, 40,000 m³ 3 / d, Jinshengda Mine 50,000 m³ 3 The drainage costs are high and the dewatering time is long. It can be seen that the traditional dewatering scheme is costly, has poor controllability, and does not make good use of favorable hydrogeological structures in the treatment of mine groundwater environment. Summary of the Invention

[0007] The purpose of this invention is to address the shortcomings of existing technologies by providing a single-layer controlled drainage method for the roof of karst water-rich metal deposits, which, under the premise of ensuring mining safety, controls the drainage of groundwater, minimizes or delays the drainage of groundwater, and aims to prevent flooding of wells, reduce drainage costs, protect groundwater resources, and control ground subsidence.

[0008] The present invention provides a method for controlling the dewatering of a single layer in the roof of a karst water-rich metal deposit, comprising the following steps:

[0009] S1, Hydrogeological Conditions Exploration of the Roof Plate

[0010] Conduct hydrogeological and engineering geological exploration of the mine, identify the hydrogeological characteristics of the deposit, determine the location and composition of the first aquitard above the deposit and the second aquitard below the deposit, determine the location and composition of the shallow aquifer above the first aquitard, determine the location and composition of the lower ore body, clarify the vertical differences in the aquifers in the upper roof of the deposit, determine the location and composition of the structural fracture zone and water-conducting fault that connects the shallow aquifer and the roof aquifer, and predict the height of overlying rock damage caused by mining.

[0011] S2. Grouting of structural fracture zones and water-conducting faults.

[0012] Using the development tunnels left over from the infrastructure construction phase, deep-hole drilling rigs are used to construct grouting holes in a cluster or fan shape in the structural fracture zone and water-conducting fault within the first aquitard. Grouting reinforcement material is then injected under high pressure into the structural fracture zone and water-conducting fault exposed by the grouting holes.

[0013] S3. Install waterproof pillars to prevent water from entering structural fracture zones and water-conducting faults.

[0014] Based on the data in step S1, through advanced regional exploration, waterproof pillars are left on the side of the ore body that is in direct contact with water-conducting faults or structural fracture zones to avoid structural fracture zones and water-conducting faults on the upper or side of the ore body, thus ensuring the safety of mining the ore body under or on the side of the roof aquifer.

[0015] S4. Perform dewatering of the mining area.

[0016] For the top aquifer, drainage holes are used to pre-drain or intercept the lateral recharge outside the development influence area and the vertical recharge within the development area.

[0017] S5. Mining using the backfilling method.

[0018] In step S4, the specific steps for dewatering the mining area are as follows: Dewatering chambers are constructed in the development roadways of the hanging wall of each intermediate ore body. Then, in the dewatering chambers, deep-hole drilling rigs are used to construct drainage holes distributed in a cluster or fan shape to the aquifer on the roof. Each drainage hole is arranged at an upward angle. High-pressure valves are installed at the openings of the drainage holes. When the water inflow of a single hole is greater than 50 m³ / h, grouting is used to plug the water. When the water inflow of a single hole is less than 50 m³ / h, the high-pressure valves are used to control the water release. At the same time, the water inflow of each intermediate section is controlled not to exceed the mine's underground drainage capacity, and a certain safety drainage margin is appropriately reserved.

[0019] Based on the analysis of the water-bearing characteristics of the ore-bearing strata revealed by the development project, dewatering chambers were arranged at intervals of 50m.

[0020] Each drainage chamber is equipped with three drainage holes, with a borehole diameter of φ108mm and a final borehole diameter of φ91mm.

[0021] In step S2, the grouting reinforcement material is a mixture of cement and clay.

[0022] Compared with the prior art, the present invention has the following advantages:

[0023] 1. By grouting, the integrity of the water-conducting rock mass is increased, the hydraulic slope of the rock mass is increased, and a stable water-impermeable layer is formed between the top aquifer and the shallow aquifer. This artificially creates two layers of water as a whole, thereby achieving the purpose of protecting water resources in the mining area and preventing ground subsidence.

[0024] 2. By leaving waterproof pillars in the ore body, the aquifer above or to the side of the roof is avoided, ensuring the safety of mining under or to the side of the aquifer; thereby reducing the amount of water inflow into the mine and controlling the range of ground subsidence.

[0025] 3. When a fracture zone and a water-conducting fault connect the top aquifer, the water head pressure at the opening drops sharply to 0, and the hydraulic gradient increases dramatically, leading to water inrush. However, using drainage holes can reduce the initial water head of the top aquifer before mining, thereby reducing the actual hydraulic gradient after the fracture and karst connect, and avoiding water inrush accidents.

[0026] 4. The filling mining method can reduce or eliminate the collapse zone and significantly reduce the height of the structural fracture zone and water-conducting fault; it can also reduce the damage to farmland and surface buildings, and has good environmental benefits; limiting the mining height can reduce the damage to the overlying strata, so as to retain a protective layer of reasonable size and prevent water inrush.

[0027] This invention utilizes advanced regional exploration and grouting treatment measures to block the water-conducting channels connecting upper and lower aquifers, reasonably avoiding structural aquifers, and ultimately achieving the purpose of controlling drainage and pressurized mining. After implementation, it can achieve the purpose of proactively preventing water hazards without damaging the groundwater resources of shallow aquifers, thus protecting water resources.

[0028] This invention mainly utilizes the natural barrier effect of the aquitard layer, combined with grouting modification and active prevention and control measures such as dewatering to suppress the occurrence of disasters. This prevents water pressure from breaking through artificial barriers such as grouting curtains, or, in the process of creating a new equilibrium state, prevents water pressure release from causing damage, thereby achieving effective control of groundwater. It is very suitable for situations where the hydrogeological conditions of the deposit are complex and the aquifer (zone) structure has certain spatial differences. Attached Figure Description

[0029] Figure 1 This is a schematic diagram of the process of the present invention.

[0030] Figure 2 This is a schematic diagram of the structure of Embodiment 1 of the present invention.

[0031] 1. First waterproof layer;

[0032] 2. Second waterproof layer;

[0033] 3. Shallow aquifer; 31. Shallow aquifer water level;

[0034] 4. Ore body;

[0035] 5. Aquifer in the roof; 51. Water level in the aquifer in the roof;

[0036] 6. Structural fracture zone;

[0037] 7. Water-conducting fault;

[0038] 8. Open up tunnels;

[0039] 9. Grouting holes;

[0040] 10. Waterproof mine pillars;

[0041] 11. Drainage chamber;

[0042] 12. Drain hole;

[0043] 13. Quaternary weathering layer. Detailed Implementation

[0044] like Figure 1 As shown, the present invention provides a single-layer controlled dewatering method for the roof of a karst water-rich metal deposit, comprising the following steps:

[0045] S1, Hydrogeological Conditions Exploration of the Roof Plate

[0046] Conduct hydrogeological and engineering geological exploration of the mine, identify the hydrogeological characteristics of the deposit, determine the location and composition of the first aquitard 1 above the deposit and the second aquitard 2 below the deposit, determine the location and composition of the shallow aquifer 3 above the first aquitard 1, determine the location and composition of the lower ore body 4 of the deposit, clarify the vertical differences of the roof aquifer 5 above the deposit, determine the location and composition of the structural fracture zone 6 and the water-conducting fault 7 that connect the shallow aquifer 3 and the roof aquifer 5, and predict the height of overburden damage caused by mining.

[0047] S2. Drilling and grouting are performed on structural fracture zone 6 and water-conducting fault 7.

[0048] Using the development roadway 8 left from the infrastructure phase, a deep hole drilling rig is used to construct grouting holes 9 in a cluster or fan shape in the structural fracture zone 6 and water-conducting fault 7 within the first water-proof layer 1. Grouting reinforcement material is injected under high pressure into the structural fracture zone 6 and water-conducting fault 7 exposed by the grouting holes 9.

[0049] S3. Install waterproof mine pillars 10 to protect the structural fracture zone 6 and water-conducting fault 7 from water.

[0050] Based on the data in step S1, through advanced regional exploration, a waterproof pillar 10 is left on the side of the ore body 4 that is in direct contact with the water-conducting fault 7 or the structural fracture zone 6, so as to avoid the structural fracture zone 6 and the water-conducting fault 7 on the upper part or side of the ore body 4, and ensure the safety of mining the ore body below or on the side of the roof aquifer 5.

[0051] S4. Perform dewatering of the mining area.

[0052] When the infrastructure drainage cannot meet the initial water level drop rate, a cluster of drainage holes is used to drain the roof aquifer 5. This allows for advance drainage or interception of lateral recharge outside the development area and vertical recharge within the development area. The specific steps are as follows: The development roadways 8 in the hanging wall of each intermediate ore body are used as drainage and interception roadways. Based on the water-bearing characteristics of the ore-bearing layer revealed by the development project, drainage chambers 11 are arranged in the development roadways 8 at 50m intervals. Three drainage holes 12, arranged in a cluster or fan shape, are drilled into the aquifer 5 of the roof using a deep-hole drilling rig inside chamber 11. High-pressure valves are installed at the openings of the drainage holes 12. When the water inflow of a single drainage hole 12 is greater than 50 m³ / h, grouting is used to plug the water. When the water inflow of a single drainage hole 12 is less than 50 m³ / h, the high-pressure valves are used to control the water release. At the same time, the water inflow of each intermediate section is controlled not to exceed the underground drainage volume of the mine, and an appropriate safety drainage margin is reserved.

[0053] S5. Mining using the backfilling method.

[0054] In step S2, the grouting reinforcement material is a mixture of cement and clay.

[0055] In this invention, each drain hole 12 is arranged at an upward angle, and the drilling opening diameter of each drain hole 12 is φ108mm and the final hole diameter is φ91mm.

[0056] In this invention, the drain hole 12 can also serve as a grouting hole.

[0057] Taking the mining of the deep ore body of the Kamoya copper-cobalt mine in the Democratic Republic of Congo as an example, this deep ore body occurs within the Luoan Group ore-bearing geological body. The R2 strata of the mining subgroup have well-developed water-bearing fissures, water-conducting structures, and karst caves, making it a complex hydrogeological deposit with direct water filling through karst fissures. The maximum groundwater head in the mining area reaches 4 MPa, and the predicted normal water inflow in the middle section of the mine pit is 41,963 m³. 3 / d, with a maximum inflow of 51874m³. 3 / d is a typical large-scale water-bearing mine. Before the mining design, the mine area underwent hydrogeological and engineering geological exploration, which basically clarified the hydrogeological characteristics of the deposit: The deposit includes the ore body 4 located in the lower part and the roof aquifer 5 located in the upper part. The roof aquifer 5 is a karst fissure aquifer. The first aquitard 1 above the deposit is a layered dolomite aquitard with an average thickness of more than 100m. The second aquitard 2 below the deposit is a water-bearing tectonic breccia and Ks group siltstone. The shallow aquifer 3 above the first aquitard 1 is a dolomite karst fissure aquifer of CMN group. The Quaternary weathered layer 13 is distributed above the shallow aquifer 3.

[0058] Research has found that, under the premise of using backfill mining to prevent large deformation and movement of the roof, relying on the water-blocking effect of the first aquifer 1 and the second aquifer 2, the shallow aquifer 3 can be prevented from flowing into the stope or roadway. During the mine infrastructure construction phase, the infrastructure development roadways and preparatory roadways can be used as dewatering projects to directly dewater the weak aquifers in the SDS, SDB, RSC, and RSF karst fissures of the ore body floor and the interstitial water of the shallow aquifer 3. Although the dewatering project volume is small and the long-term drainage cost is low, the process is relatively complex. It requires the investigation of the hydraulic connections of each aquifer zone underground. At the same time, safety technical measures such as groundwater monitoring, underground water release and shut-off tests, three-dimensional numerical simulation, local detection, and local grouting should be adopted, which has certain technical difficulties. Therefore, this invention is needed for controlled dewatering, which includes the following steps:

[0059] S1, Hydrogeological Conditions Exploration of the Roof Plate

[0060] Prior to the mining design, hydrogeological and engineering geological explorations were conducted in the mining area, which basically clarified the hydrogeological characteristics of the deposit. The deposit was determined to consist of the lower ore body 4 and the upper roof aquifer 5. The roof aquifer 5 is a karst fissure aquifer. The first aquitard 1 above the deposit is a layered dolomite aquitard with an average thickness exceeding 100m. The second aquitard 2 below the deposit consists of aquitard tectonic breccia and Ks-form siltstone. The shallow aquitard above the first aquitard 1... Aquifer 3 is a dolomite karst fissure aquifer of the CMN group. The Quaternary weathered layer 13 is distributed on the upper side of the shallow aquifer 3. The Quaternary weathered layer 13 and the ore body 4 have good water connectivity. It is determined that the complete section of the first aquitard 1 can block or weaken the connection between the upper and lower aquifers. The vertical difference of the top aquifer 5 is clarified. The location of the structural fracture zone 6 and the water-conducting fault 7 that connect the shallow aquifer 3 and the top aquifer 5 is determined. The height of the overlying rock damage caused by mining is predicted.

[0061] S2. Drilling and grouting are performed on structural fracture zone 6 and water-conducting fault 7.

[0062] Using the development roadway 8 left from the infrastructure construction phase, a deep hole drilling rig is used to construct grouting holes 9 in a cluster or fan shape in the structural fracture zone 6 and water-conducting fault 7 within the first water-proof layer 1. Grouting reinforcement material is injected under high pressure into the structural fracture zone 6 and water-conducting fault 7 exposed by the grouting holes 9.

[0063] S3. Install waterproof mine pillars 10 to protect the structural fracture zone 6 and water-conducting fault 7 from water.

[0064] Based on the data in step S1, through advanced regional exploration, a waterproof pillar 10 is left on the side of the ore body 4 that is in direct contact with the water-conducting fault 7 or the structural fracture zone 6. This avoids the structural fracture zone 6 and the water-conducting fault 7 on the upper or side of the ore body 4, prevents communication between the upper and lower aquifers from causing a water inrush accident, and ensures the safety of mining the ore body below or on the side of the roof aquifer 5.

[0065] S4. Perform dewatering of the mining area.

[0066] When the infrastructure drainage cannot meet the initial water level drop rate, a cluster of drainage holes is used to drain the roof aquifer 5. This allows for advance drainage or interception of lateral recharge outside the development area and vertical recharge within the development area. The specific steps are as follows: The development roadways 8 in the hanging wall of each intermediate ore body are used as drainage and interception roadways. Based on the water-bearing characteristics of the ore-bearing layer revealed by the development project, drainage chambers 11 are arranged in the development roadways 8 at 50m intervals. Three drainage holes 12, arranged in a cluster or fan shape, are drilled into the aquifer 5 of the roof using a deep-hole drilling rig inside chamber 11. High-pressure valves are installed at the openings of the drainage holes 12. When the water inflow of a single drainage hole 12 is greater than 50 m³ / h, grouting is used to plug the water. When the water inflow of a single drainage hole 12 is less than 50 m³ / h, the high-pressure valves are used to control the water release. At the same time, the water inflow of each intermediate section is controlled not to exceed the underground drainage volume of the mine, and an appropriate safety drainage margin is reserved.

[0067] S5. Mining using the backfilling method.

[0068] This invention fully utilizes the water-blocking function of the first aquitard 1, and uses grouting to cut off the channel in the structural fracture zone 6 and water-conducting fault 7 section. It also adopts a backfilling mining method to ensure that the roof does not deform, without draining the water in the shallow aquifer 3. It uses the drainage project on the hanging wall of the ore body to drain and intercept the groundwater in the ore-bearing layer and the lateral recharge. At the same time, it uses the local waterproof pillar 10 to block the vertical recharge of the upper aquifer to the ore-bearing layer. Only the groundwater in the roof aquifer 5 is drained, so that mining and backfilling operations can be carried out under waterless or low water conditions, reducing the drainage volume and improving the economic benefits of the mine.

[0069] Practice has proven that using traditional dewatering methods, the mine water inflow will reach over 41,000 m³ / d; however, when using this invention, when the groundwater level of the top aquifer 5 drops to about 1,000 m elevation, the mine water inflow is only 22,000 m³ / d, reducing drainage by 19,000 m³ / d, a reduction of 46%. Furthermore, this method improves the efficiency of mine dewatering, enabling the mine to be put into operation within 5 years of infrastructure construction.

[0070] This invention utilizes the spatial distribution of aquifers (or impermeable layers) in upper and lower layers, and takes into account the principles of groundwater dynamics and the mining progress of the mine, in order to minimize, reduce, or delay the discharge of groundwater while ensuring the safe development of shafts and mining projects. This aims to prevent sudden flooding of wells, reduce drainage costs, and protect groundwater resources.

[0071] The hydrogeological structure is a complex system composed of lithology, tectonics, and groundwater. Due to various geological reasons, the aquifers above the ore body are often discontinuous and exhibit regular variations in cross-section. There is often a multi-layered structure with varying strengths between the ore body's top layer and the shallow aquifers. This multi-layered structure makes it possible to create artificial dual water levels in both the shallow and deep sections during ore body mining. This invention is particularly suitable for safe mining with such dual water levels.

[0072] Mining-induced overburden damage is the root cause of water inrush. Therefore, taking appropriate mining measures to reduce the degree of overburden damage induced by mining and reduce the impact range of the collapse zone and water-conducting fracture zone are also important water inrush prevention and control measures.

Claims

1. A method for controlled dewatering of a single layer in the roof of a karst water-rich metal deposit, characterized in that, Includes the following steps: S1, Hydrogeological Conditions Exploration of the Roof Plate Conduct hydrogeological and engineering geological exploration of the mine, identify the hydrogeological characteristics of the deposit, determine the location and composition of the first aquitard (1) above the deposit and the second aquitard (2) below the deposit, determine the location and composition of the shallow aquifer (3) above the first aquitard, determine the location and composition of the lower ore body (4) of the deposit, clarify the vertical differences in the aquifer (5) above the deposit, determine the location and composition of the structural fracture zone (6) and water-conducting fault (7) that connect the shallow aquifer and the aquifer, and predict the height of overburden damage caused by mining. S2. Grouting of structural fracture zones and water-conducting faults. Using the development roadway (8) left from the infrastructure construction phase, a deep hole drilling rig is used to construct grouting holes (9) distributed in a cluster or fan shape in the structural fracture zone and water-conducting fault within the first water-resistant layer. The grouting reinforcement material is injected into the structural fracture zone and water-conducting fault exposed by the grouting holes under high pressure. S3. Install waterproof pillars to prevent water from entering structural fracture zones and water-conducting faults. Based on the data in step S1, through advanced regional exploration, waterproof pillars (10) are left on the side of the ore body that is in direct contact with water-conducting faults or structural fracture zones to avoid structural fracture zones and water-conducting faults on the upper or side of the ore body, and to ensure the safety of mining the ore body under or on the side of the roof aquifer. S4. Perform dewatering of the mining area. For the top aquifer, drainage holes are used to pre-drain or intercept the lateral recharge outside the development influence area and the vertical recharge within the development area. S5. Mining using the backfilling method.

2. The single-layer controlled dewatering method for the roof of a karst water-rich metal deposit according to claim 1, characterized in that, In step S4, the specific steps for dewatering the mining area are as follows: Dewatering chambers (11) are constructed in the development roadways of the hanging wall of each intermediate ore body. Then, in the dewatering chambers, deep-hole drilling rigs are used to construct drainage holes (12) distributed in a cluster or fan shape to the aquifer on the roof. Each drainage hole is arranged at an upward angle. High-pressure valves are installed at the openings of the drainage holes. When the water inflow of a single hole is greater than 50 m3 / h, grouting is used to plug the water. When the water inflow of a single hole is less than 50 m3 / h, the high-pressure valve is used to control the water release. At the same time, the water inflow of each intermediate section is controlled not to exceed the mine's underground drainage volume, and a certain safety drainage margin is appropriately reserved.

3. The single-layer controlled dewatering method for the roof of a karst water-rich metal deposit according to claim 2, characterized in that: Based on the analysis of the water-bearing characteristics of the ore-bearing strata revealed by the development project, dewatering chambers were arranged at intervals of 50m.

4. The single-layer controlled dewatering method for the roof of a karst water-rich metal deposit according to claim 2, characterized in that: Each drainage chamber is equipped with three drainage holes, with a borehole diameter of φ108mm and a final borehole diameter of φ91mm.

5. The single-layer controlled dewatering method for the roof of a karst water-rich metal deposit according to claim 1, characterized in that, In step S2, the grouting reinforcement material is a mixture of cement and clay.

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