Mine safety isolation layer design method and mine safety isolation layer
By using three-dimensional numerical simulation and constitutive models of strain-softened rock masses, the problem of difficulty in assessing the strength and thickness in the design of mine safety isolation layers was solved, thereby improving the self-stability and engineering safety of the safety isolation layers and ensuring the safe transition of the mine.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- BEIJING MINING & METALLURGICAL TECH GRP CO LTD
- Filing Date
- 2025-12-26
- Publication Date
- 2026-04-21
AI Technical Summary
Existing technologies lack systematic simulations of three-dimensional geological conditions, dynamic mining processes, and nonlinear material responses when designing mine safety isolation layers. This makes it difficult to accurately assess the strength and thickness of the isolation layers, which can easily lead to structural instability or cost waste. Furthermore, traditional methods ignore complex geological factors and are difficult to predict chain reactions of disasters.
A three-dimensional numerical simulation method was used to construct a model that includes geological bodies, mining areas, and multi-state stockpiles. A constitutive model of strain-softened rock mass was used to describe the rock mass damage evolution process. The strength of the safety isolation layer was determined based on the multi-state stockpile load, and the critical caving height was determined through numerical simulation. The thickness of the safety isolation layer was designed to be greater than any critical caving height to achieve self-stability.
By accurately determining the strength and thickness parameters of the safety isolation layer, the reliability of the design and the safety of the project were improved, effectively preventing the isolation layer from being damaged or collapsing, and ensuring the safety of the mine and its resource continuity.
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Figure CN121897404A_ABST
Abstract
Description
Technical Field
[0001] This application relates to the field of mine safety technology, and in particular to a design method for a mine safety isolation layer and a mine safety isolation layer. Background Technology
[0002] With the development of mining technology, many open-pit mines have transitioned to underground mining after resource depletion, forming a combined open-pit-to-underground mining model. The original open-pit mines often retain large amounts of loose gravel and sediment deposits, and may accumulate rainwater or groundwater, creating a complex loading environment. Simultaneously, the redistribution of surrounding rock stress and the propagation of rock fractures caused by underground mining activities further exacerbate the instability of the overlying strata.
[0003] To ensure the safe operation of underground mining sites, a safety isolation layer is usually set up between the bottom of the open pit and the underground goaf area. This layer serves as a key engineering barrier to prevent surface disasters (such as landslides, debris flows, and floods) from being transmitted downwards and to resist the impact of underground mining activities.
[0004] Currently, traditional methods for designing safety buffer layers rely on empirical formulas (such as the limit equilibrium method) or simplified models. These methods lack systematic simulation of three-dimensional geological conditions, dynamic mining processes, and nonlinear material responses, making it difficult to quantitatively assess the scientific validity of buffer layer parameters. Empirical methods cannot accurately analyze the load distribution of the ore body and the collaborative bearing mechanism between artificial structures and primary pillars, easily leading to redundant or insufficient buffer layer strength, causing structural instability or cost waste. Furthermore, traditional models neglect complex geological factors such as faults and geostress fields, making it difficult to predict cascading disaster reactions. Therefore, a quantitative method based on three-dimensional numerical simulation is urgently needed to achieve dynamic optimization of the strength and thickness of safety buffer layers, filling this technological gap. Summary of the Invention
[0005] In view of this, this application provides a design method for a mine safety isolation layer and a mine safety isolation layer, with the aim of solving one of the technical problems in the prior art.
[0006] To achieve the above objectives, the technical solution adopted in this application is as follows: In a first aspect, the present invention provides a method for designing a mine safety isolation layer, comprising: A three-dimensional numerical simulation model was constructed, which included the geological body, the mining area, the multi-state stockpile, and the proposed safety isolation layer. The rock mass damage evolution process was described by a rock mass constitutive model based on strain softening. The strength of the safety isolation layer is determined based on the load applied to the multi-state stack to prevent the safety isolation layer from being damaged and collapsing; Along the outline of the primary ore strata, multiple unstable mining areas were selected to excavate spaces of predetermined spans. Numerical simulations were used to determine the critical collapse height at each location. The thickness of the safety isolation layer was designed to be greater than any critical collapse height, so that the safety isolation layer could achieve self-stabilization.
[0007] In an optional implementation, the safety isolation layer includes the primary ore layer, and the stope is located below the primary ore layer; The initial thickness range of the primary ore strata is obtained by using empirical formulas, limit equilibrium methods, proportional span methods, or by comparing with similar mines at home and abroad.
[0008] In an optional implementation, the method for optimizing the thickness of the primary ore-bearing rock layer is as follows: Define the pit bottom and sidewalls of the primary ore-bearing rock strata; First, optimize the thickness of the primary ore layer at the bottom of the pit, and then determine the thickness of the primary ore layer at the sidewalls. Numerical models were established for the thickness of primary ore layers at different pit bottoms and sidewalls. The damage degree and safety factor distribution of the primary ore layer calculation unit during underground mining were calculated under different thickness values to determine whether the primary ore layer meets the self-stability condition. Then, by comparing the displacement change law of the key point position under different thickness values, the optimized thickness of the primary ore layer was determined.
[0009] In an optional embodiment, the safety isolation layer further includes a high-strength artificial structure layer disposed on top of the primary ore layer and a low-strength artificial structure layer disposed on top of the high-strength artificial structure layer. The strength of the high-strength artificial structure layer and the low-strength artificial structure layer is such that when the open pit is filled with multi-state stockpile, the in-situ stress state of the high-strength artificial structure layer and the low-strength artificial structure layer as a whole should be below the overall strength envelope curve of the high-strength artificial structure layer and the low-strength artificial structure layer, so that the high-strength artificial structure layer and the low-strength artificial structure layer as a whole are not destroyed by the multi-state stockpile.
[0010] In an optional implementation, the in-situ stress state of the high-strength artificial structure layer and the low-strength artificial structure layer is obtained by calculating the results of a three-dimensional numerical simulation model, and the maximum principal stress and minimum principal stress of the layer region are extracted from the calculation results. The strength envelopes of the high-strength and low-strength artificial structures were determined by fitting the triaxial compression test data of the 28-day standard-cured specimens of the construction materials.
[0011] In an optional implementation, a predetermined span of exposed space is excavated at the stope where the roof is most unstable in the primary ore layer at the bottom of the pit, and numerical simulation is used to determine the critical collapse height in the high-strength artificial structure layer. The design thickness of the high-strength artificial structure layer is then calculated by multiplying the critical height by a safety factor.
[0012] In an optional implementation, a predetermined span of exposed space is excavated at the highest point of the primary ore layer on the sidewall, and numerical simulation is used to determine the critical collapse height within the low-strength artificial structure layer. The top elevation benchmark value of the low-strength artificial structure layer is calculated by multiplying the critical collapse height by a safety factor. Finally, the design thickness of the low-strength artificial structure layer is determined by calculating the vertical distance between the benchmark value and the top surface of the high-strength artificial structure layer.
[0013] In an optional implementation, numerical simulation is used to simulate the entire process of underground mining and backfilling according to the mining process. After excavating the calculated high-stress primary ore layer, the collapse simulation of the excavated roof is carried out to obtain the collapse height of the high-strength artificial structure layer or the low-strength artificial structure layer. Alternatively, physical simulation can be used to simulate the entire process of underground mining and backfilling according to the mining process. After excavating and monitoring the original rock structure with large deformation, the collapse of high-strength or low-strength artificial structures can be simulated to obtain the height of the collapse of high-strength or low-strength artificial structures. The maximum value of collapse of the high-strength or low-strength artificial structure layer is determined by comparing numerical simulation and physical simulation, and the thickness of the high-strength or low-strength artificial structure layer is calculated based on the collapse height.
[0014] Secondly, the present invention provides a mine safety isolation layer, comprising, arranged sequentially from bottom to top: The primary ore strata, located at the bottom and below the side walls of the open pit, serve to bear the upper load and isolate the open pit from the underground mining area; A high-strength artificial structure layer is laid on top of the primary mineral rock layer; A low-strength artificial structure layer is laid on top of the high-strength artificial structure layer, with its upper surface extending to the sidewall area of the open pit and bearing the pressure from the multi-state pile body inside the open pit.
[0015] In an optional embodiment, the thickness of the primary ore layer is: 15-30 meters at the bottom of the pit and 20-40 meters at the side walls; The thickness of the high-strength artificial structure layer is 15-30 meters; The thickness of the low-strength artificial structure layer is 20-60 meters; The strength of the high-strength artificial structure layer is ≥4MPa; The strength of the low-strength artificial structure layer is ≥1.5MPa.
[0016] Compared to existing technologies, the advantages of this application are as follows: This application proposes a design method for mine safety isolation layers, which includes constructing a three-dimensional numerical simulation model comprising a geological body, a stope, a multi-state stockpile, and a proposed safety isolation layer; employing a strain-softening-based rock mass constitutive model to describe the rock mass damage evolution process; determining the strength of the safety isolation layer based on the loads applied to the multi-state stockpile to prevent its destruction and collapse; selecting multiple unstable stopes along the contour of the primary ore strata to excavate predetermined spans of exposed space, using numerical simulation to determine the critical collapse height at each location, and designing the thickness of the safety isolation layer to be greater than any critical collapse height, thus enabling the safety isolation layer to achieve self-stability. This method encompasses three-dimensional numerical simulation, safety isolation layer strength and thickness design, and by establishing a realistic numerical model under complex geological and mining conditions, combined with experimental and simulation results, accurately determining the strength and thickness parameters of the safety isolation layer, effectively improving the design reliability and engineering safety of the safety isolation layer. Attached Figure Description
[0017] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of this application and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.
[0018] Figure 1 The present application shows schematic diagrams of the structure of a mine in some embodiments; Figure 2 The flowcharts of the mine safety isolation layer design method in some embodiments of this application are shown; Figure 3 The following are schematic diagrams illustrating the design structure of the mine safety isolation layer in some embodiments of this application; Figure 4 The diagram illustrates the strength envelope curves and principal stress distribution values of high-strength and low-strength artificial structures in some embodiments of this application. Detailed Implementation
[0019] The embodiments of this application are described in detail below. Examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain this application, and should not be construed as limiting this application.
[0020] In the description of this application, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc., indicating the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this application.
[0021] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this application, "multiple" means two or more, unless otherwise explicitly specified.
[0022] In this application, unless otherwise expressly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances.
[0023] In this application, unless otherwise expressly specified and limited, "above" or "below" the second feature can mean that the first feature is in direct contact with the second feature, or that the first feature is in indirect contact with the second feature through an intermediate medium. Furthermore, "above," "on top of," and "over" the second feature can mean that the first feature is directly above or diagonally above the second feature, or simply that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature can mean that the first feature is directly below or diagonally below the second feature, or simply that the first feature is at a lower horizontal level than the second feature.
[0024] like Figure 1 As shown, the mine's safety isolation layer consists only of the primary ore layer, which includes the primary ore layer at the bottom of the pit and the primary ore layer at the sides. The primary ore layer at the bottom of the pit is located at the bottom of the open pit, while the primary ore layer at the sides is located at the bottom and sides of the open pit. Below the safety isolation layer are multiple underground mining areas, and above the safety isolation layer is a multi-state stockpile, which includes artificially deposited waste (tailings, waste rock) and water, rock, mud, and sand that have naturally slid down from the open pit due to slope instability.
[0025] like Figure 2 As shown, embodiments of this application provide a method for designing mine safety isolation layers, primarily used to accurately set the strength and thickness parameters of the safety isolation layer by combining three-dimensional numerical simulation. The mine safety isolation layer design method includes: Step S10: Construct a three-dimensional numerical simulation model that includes the geological body, the mining area, the multi-state stockpile, and the proposed safety isolation layer. Use a rock mass constitutive model based on strain softening to describe the rock mass damage evolution process.
[0026] In one embodiment, the three-dimensional numerical simulation model can employ a rock mass constitutive model based on strain softening, such as the IMASS constitutive model, which can simulate the degree of damage to the surrounding rock caused by mining rock mass excavation.
[0027] First, a three-dimensional geological model is constructed, which includes the original surface model of the open pit, the current surface model of the open pit, the stratigraphic model, the fault model, the ore body model, and other three-dimensional geological models.
[0028] Then, a three-dimensional model of the mining boundary contour is established. This three-dimensional model of the mining boundary contour includes the boundary contour of the open-pit excavation in stages, the boundary contour of the underground mining dividing the mining area and pillars, the boundary contour of the safety isolation layer of the primary ore rock layer with different thickness schemes, and the boundary contour of the safety isolation layer of the artificial structure layer with different thicknesses.
[0029] The safety isolation layer also adopts a rock mass constitutive model based on strain softening. Subsequent thickness calculations and optimizations are all processed by the rock mass constitutive model based on strain softening, and the primary ore layer is set with Mohr-Coulomb constitutive parameters.
[0030] A constitutive model of rock mass based on strain softening is used to characterize the progressive failure process of rock mass during loading, especially the strength degradation characteristics of the surrounding rock and the rock mass. Various states of rock masses (such as loose deposits, semi-consolidated bodies, and fractured bodies) naturally formed or artificially deposited in open pits are included, which exert dynamic non-uniform loads on the underlying structure.
[0031] Rock mass constitutive model parameters based on strain softening, including uniaxial compressive strength σ c GSI and m i The three parameters were obtained through experiments and field investigations, among which the uniaxial compressive strength σ c Based on indoor test results, and GSI's judgment based on field investigations and experience, m i The values are obtained from empirical values based on lithology tables or by fitting triaxial test data.
[0032] Step S20: Determine the strength of the safety isolation layer based on the load applied to the multi-state stack to prevent the safety isolation layer from being damaged and collapsing.
[0033] By using numerical simulation results, the stress distribution transmitted to the isolation layer by the multi-state reactor under different working conditions is analyzed. Based on this, the minimum compressive strength or minimum shear strength that the safety isolation layer must have is determined to prevent it from being crushed or sheared.
[0034] Step S30: Along the outline of the primary ore strata, select multiple unstable mining areas to excavate the predetermined span of exposed space, use numerical simulation to determine the critical collapse height at each location, and design a safety isolation layer with a thickness greater than any critical collapse height to enable the safety isolation layer to achieve self-stabilization.
[0035] For several representative unstable mining areas, numerical simulation was used to find the "critical collapse height" at each location by gradually increasing the exposure height. This means that the surrounding rock will become unstable and collapse after the height is exceeded.
[0036] The thickness of the safety isolation layer is designed to be greater than or equal to the maximum critical drop height to achieve self-stability. The thickness of the safety isolation layer is designed to be greater than the maximum critical drop height at all predicted locations, thereby ensuring that the layer itself possesses sufficient structural stiffness and load-bearing capacity to achieve long-term self-stability without additional support.
[0037] The safety isolation layer design method of this application covers three-dimensional numerical simulation, safety isolation layer strength and thickness design. By establishing a realistic numerical model under complex geological and mining conditions, and combining experimental and simulation results, the strength and thickness parameters of the safety isolation layer are accurately determined, which effectively improves the design reliability and engineering safety of the safety isolation layer.
[0038] In some embodiments, such as Figure 3 As shown, the safety isolation layer includes the primary ore layer, and the mining area is located below the primary ore layer.
[0039] The initial thickness range of the primary ore strata is obtained by using empirical formulas, limit equilibrium methods, proportional span methods, or by comparing with similar mines at home and abroad.
[0040] The initial thickness of the primary ore layer is generally 15m-40m. In numerical simulation, different model calculation schemes are set according to the initial range, such as the initial thickness of the primary ore layer being 15m, 20m, 25m, 30m, 35m, 40m, etc.
[0041] Among them, empirical formula calculation methods include, but are not limited to, Rubeneit theory, fixed beam theory, engineering calculation method, Protodyakonov arch theory, and other methods.
[0042] The formula for calculating the reasonable thickness of the roof support pillar using the Rubeneit theory is as follows:
[0043] In the formula: The thickness of the pillar is in meters (m). For safety factor; The bulk density of the ore pillar is N / m³. 3 ; The unit weight of the rock stratum, N / m³ 3 ; The span of the pillar is in meters (m). The overburden load on the pillar is MPa; The ultimate strength of the top plate under bending conditions, in MPa. , =7%-10%, =2-3, is the ultimate strength of rock under bending conditions, in MPa.
[0044] The formula for calculating the reasonable thickness of the roof support pillar using the fixed beam theory is as follows:
[0045] The formula for calculating the reasonable thickness of the roof support pillar using engineering calculation methods is as follows:
[0046] In the formula: For safety reasons, =4-8; denoted as the tensile strength of the rock, in MPa.
[0047] The calculation formula for Protodyakonov's arch theory is as follows:
[0048] In the formula: h The height of the fall arch; The internal friction angle of the rock; This represents the rock hardness coefficient; other symbols have the same meaning as before.
[0049] The limit equilibrium method needs to consider the loads exerted by the multi-state mass on the primary ore and rock strata within the open pit. The specific calculation formula is as follows.
[0050]
[0051] in, For the limit equilibrium safety factor, and Shear strength of the primary ore rock strata; z This refers to the thickness of the primary ore-bearing rock layer; x The length of the primary ore strata exposed in the mining area; yThe width of the exposed primary ore strata in the mining area; q This is due to the overlying load and the self-weight of the exposed primary mineral rock layer.
[0052] In some embodiments, the method for optimizing the thickness of the primary ore layer is as follows: Define the bottom and sidewalls of the primary ore strata.
[0053] First, optimize the thickness of the primary ore layer at the bottom of the pit, and then determine the thickness of the primary ore layer at the side slope.
[0054] Numerical models were established for the thickness of primary ore layers at different pit bottoms and sidewalls. The damage degree and safety factor distribution of the primary ore layer calculation unit during underground mining were calculated under different thickness values to determine whether the primary ore layer meets the self-stability condition. Then, by comparing the displacement change law of the key point position under different thickness values, the optimized thickness of the primary ore layer was determined.
[0055] The optimal primary ore layer thickness is determined by setting the displacement variation law at key point locations. The key location is set as the center point of the primary ore layer. The displacement of the key point is calculated as a function of the primary ore layer thickness under the condition of self-stability. The value of the inflection point in the curve is determined as the optimal primary ore layer thickness.
[0056] In some embodiments, the damage index of the rock mass constitutive model based on strain softening is calculated. Its value range is [1,-1] and it is divided into four stages to evaluate the degree of fracture and damage of the rock mass. Damage degree = 1 represents no damage, 0 < damage degree < 1 represents crack damage, -1 < damage degree < 0 represents unit failure, and damage degree = -1 represents collapse.
[0057] In some embodiments, the calculation method for the safety factor of the computing unit is as follows:
[0058] in, The maximum principal stress of the element. The minimum principal stress of the element. The uniaxial compressive strength in a rock mass constitutive model based on strain softening. m b , a and s Depends on the properties of the rock mass; m b This is an empirical constant that controls the confining pressure sensitivity of the rock mass; it is generally the software default value. a and s The software automatically calculates the parameters based on the constitutive model input parameters.
[0059] Based on the distribution law of damage degree and unit safety factor of the primary ore stratum calculation unit, when the cell with damage degree less than 0 or the cell with unit safety factor less than 1 does not form an overall vertical connection in the primary ore stratum, it satisfies the self-stability condition.
[0060] In some embodiments, such as Figure 4 As shown, the safety isolation layer also includes a high-strength artificial structure layer and a low-strength artificial structure layer. The strength of the high-strength artificial structure layer and the low-strength artificial structure layer is such that when the open pit is filled with multi-state material, the in-situ stress state of the high-strength artificial structure layer and the low-strength artificial structure layer as a whole should be below the strength envelope curve of the artificial structure layer, so that the high-strength artificial structure layer and the low-strength artificial structure layer as a whole are not destroyed by the multi-state material.
[0061] See also Figure 3 The initial design of both the high-strength and low-strength artificial structures is no less than 20m thick, with the upper surface of the low-strength artificial structure located above the side mining area.
[0062] The initial design specifies that the strength of the high-strength artificial structure layer should be no less than 4 MPa, and the strength of the low-strength artificial structure layer should be no less than 2 MPa.
[0063] In some embodiments, the in-situ stress state of the high-strength artificial structure layer and the low-strength artificial structure layer is obtained by calculating the results of a three-dimensional numerical simulation model, and the maximum principal stress and minimum principal stress of the layer region are extracted from the calculation results.
[0064] In some embodiments, the strength envelopes of the high-strength and low-strength artificial structures are determined by fitting the triaxial compression test data of the 28-day standard-cured specimens of their construction materials.
[0065] In one embodiment, the strength parameters of the high-strength artificial structure layer and the low-strength artificial structure layer are obtained as follows: Step S31: Conduct strength and flowability tests on samples of high-strength and low-strength artificial building layers with different concentrations and ratios: Determine the reasonable concentration of high-strength and low-strength artificial building layer materials based on the strength and flowability results, and obtain triaxial strength data for various ratios at the same concentration, and obtain the strength envelope based on the triaxial strength data. Step S32: Establish a large-scale three-dimensional numerical simulation model: a rock mass constitutive model based on strain softening is adopted. The model includes geological structural units such as the surface of the open pit, strata, ore body, and faults, as well as mining structures such as primary ore rock structure and underground mining area. At the same time, the preliminary strength and thickness of high-strength artificial structure layer and low-strength artificial structure layer are set. The open pit is filled with multi-state piles formed naturally or artificially. The grid cells are named by grouping and the underground mining sequence is set. Step S33: Perform stress balance calculation and extract in-situ stress of high-strength artificial structure layer and low-strength artificial structure layer: Apply initial ground stress to equilibrium state based on the original landform model, simulate excavation to the surface of open pit and reach new stress balance, add high-strength artificial structure layer and low-strength artificial structure layer and multi-state pile in open pit in layered simulation and calculate equilibrium, and extract in-situ stress data of different parts of the final calculation results. Step S34: Based on the comparison between the strength envelope and the in-situ stress results, determine the strength requirements of the high-strength artificial structure layer and the low-strength artificial structure layer: Fit the strength envelope based on the triaxial strength data obtained in step S31, and combine it with the in-situ stress state in step S33 to ensure that the stress state is below the strength envelope, thereby determining the required design strength of the high-strength artificial structure layer and the low-strength artificial structure layer.
[0066] In some embodiments, a predetermined span of exposed space is excavated at the stope where the roof is most unstable at the original ore layer at the bottom of the pit, and numerical simulation is used to determine the critical collapse height in the high-strength artificial structure layer. The design thickness of the high-strength artificial structure layer is calculated by multiplying the critical height by a safety factor, and the safety factor is greater than or equal to 1.3.
[0067] The predetermined excavation span and exposed space size are generally for a single stope; the excavation location is near the primary ore and rock structure above the most dangerous stope in the underground mining simulation, and the most dangerous stope is one of several stopes in the stress concentration area of the mining section.
[0068] The critical collapse height is determined based on the damaged collapse zone. The damaged collapse zone can be determined by calculating the damage index of the grid cells. Cells with a damage index < 0 are defined as collapse zones.
[0069] In some embodiments, a predetermined span of exposed space is excavated at the highest point of the primary ore layer on the sidewall, and numerical simulation is used to determine the critical collapse height within the low-strength artificial structure layer. The value obtained by multiplying the critical collapse height by a safety factor is used to calculate the top elevation benchmark of the low-strength artificial structure layer. Finally, the design thickness of the low-strength artificial structure layer is determined by calculating the vertical distance between the benchmark value and the top surface of the high-strength artificial structure layer, with a safety factor greater than or equal to 1.3.
[0070] The predetermined excavation span and exposed space size are generally for a single stope; the excavation location is near the primary ore and rock structure above the most dangerous stope in the underground mining simulation, and the most dangerous stope is one of several stopes in the stress concentration area of the mining section.
[0071] The critical collapse height is determined based on the damaged collapse zone. The damaged collapse zone can be determined by calculating the damage index of the grid cells. Cells with a damage index < 0 are defined as collapse zones.
[0072] The following specific embodiment illustrates the process of determining high-strength and low-strength artificial structures: In this embodiment, the stope plane size is 90m×15m (length×width). Each stope is mined for a length of about 45m each time. After the cementation and curing of the first mining area is completed, the remaining 45m long stope will be mined. The maximum exposed area of the ore body is 45m×15m (length×width).
[0073] By excavating cavities of 45m × 15m (length × width) into the original ore rock structure at the bottom of multiple mining areas where stress is concentrated, the collapse height of the high-strength artificial structure layer was calculated, simulated, and delineated as 12m. Multiplying this by a safety factor of 1.5, the thickness of the high-strength artificial structure layer was obtained as 18m.
[0074] In this embodiment, by excavating the exposed space of the primary ore strata corresponding to the side slope of the mining area with a plane size of 45m×18m (length×width), the collapse height of the low-strength artificial structure layer is calculated, simulated, and delineated as 6m. Taking a safety factor of 1.5, the top elevation of the low-strength artificial structure layer is -372m, and the bottom elevation of the open-pit mine is -350m. From the above, it can be easily derived that the top elevation of the high-strength artificial structure layer is -332m, and the thickness of the low-strength artificial structure layer is calculated to be 45m.
[0075] In some embodiments, numerical simulation is used to simulate the entire process of underground mining and backfilling according to the mining process. After excavating the calculated high-stress primary ore layer, the collapse simulation is performed on the excavated roof to obtain the collapse height of the high-strength artificial structure layer or the low-strength artificial structure layer.
[0076] In one embodiment, the specific steps for obtaining the caving thickness using numerical simulation are as follows: Step S411: Based on the set underground mining sequence, simulate the entire process of underground mining and backfilling, and calculate and obtain the corresponding high-stress pit bottom primary ore and rock structure and high-stress side primary ore and rock structure area in the underground mining and the entire process. Step S412, simulate the collapse of the original ore and rock structure at the bottom of the pit and determine the collapse height of the high-strength artificial structure layer: excavate a predetermined span of exposed space in the high stress area of the original ore and rock structure at the bottom of the pit, that is, assign the material of the space unit to null, and at the same time apply reverse balancing forces (simulate surrounding rock constraints) to the surrounding and bottom plate units. After calculating the balance, determine the collapse height of the high-strength artificial structure layer. Step S413: Simulate the collapse of the original rock structure of the slab and determine the collapse height of the low-strength artificial structure layer: Excavate a predetermined span of exposed space at the highest point of the original rock structure of the slab, that is, assign the material of the space unit to null, and at the same time apply reverse balancing forces (simulate surrounding rock constraints) to the surrounding and bottom plate units. After calculating the balance, determine the collapse height of the low-strength artificial structure layer.
[0077] In some embodiments, physical simulation is used to simulate the entire process of underground mining and backfilling according to the mining process. The original rock structure with large deformation is excavated and monitored to simulate the collapse of high-strength artificial structure layer or low-strength artificial structure layer, and to obtain the height of collapse of high-strength artificial structure layer or low-strength artificial structure layer. The maximum value of collapse of the high-strength or low-strength artificial structure layer is determined by comparing numerical simulation and physical simulation, and the thickness of the high-strength or low-strength artificial structure layer is calculated based on the collapse height.
[0078] In one embodiment, the specific steps for obtaining the caving thickness using physical simulation are as follows: Step S421: Determine the similarity ratio based on the test dimensions of the similar simulation model and the actual size of the open-pit pit in the simulation area; Step S422: Based on the rock mass mechanics parameters, the strength mechanics parameters of the high-strength artificial structure layer and the low-strength artificial structure layer and the similarity ratio, conduct a material proportioning experiment to determine the strength proportion number of the similar simulated rock mass that meets the conditions. The material mix designation used in the similarity simulation test was determined through multiple sets of material mix design experiments based on the rock mechanics parameters and similarity ratio, and it meets the requirements of the similarity ratio. Step S423, Casting and Test Preparation: Screen and dry river sand, mix river sand, gypsum, putty powder and water according to the preset similar strength ratio; lay a friction-reducing layer (oil paper-lubricating oil-oil paper) on the test platform and set a height benchmark; according to the geological structure design outline, build the mixture in layers to simulate rock strata and ore bodies, use mica powder to simulate weak surfaces, and embed strain bricks; connect the strain bricks to the data acquisition system and zero it; set settlement monitoring points on the model surface; spray matte speckle and calibrate the DIC system, and use DIC digital speckle technology to monitor the strain data of the entire field; The DIC digital speckle technology is employed, which involves spraying speckle onto the surface of the specimen, acquiring images using a high-speed camera, and calculating displacement and strain using image processing technology. Step S424: Conduct a similar simulation test. Based on the mining design, simulate the entire process of underground mining and backfilling. After the excavation of a single stope is completed, collect surface settlement, stress, and strain data for 20 minutes. Then, backfill the goaf of this step. After backfilling, continue to collect data for 10 minutes. After the backfill body stabilizes, proceed to the next cycle of mining.
[0079] Step S425 involves processing the collected surface subsidence data, stress evolution data, and DIC full-field strain data to analyze the evolution law of the overburden stress field and determine the primary ore rock structure with high stress and large deformation during excavation monitoring.
[0080] Step S426: After completing all designed ore body mining and backfilling cycles, excavate the primary ore rock structure at the bottom and the primary ore rock structure at the side of the pit with larger deformation in sequence, measure the collapse size of the artificial safety layer constructed after excavation, and calculate the actual collapse size through similarity ratio.
[0081] This application provides a mine safety isolation layer, comprising, from bottom to top, a primary ore layer, a high-strength artificial structure layer, and a low-strength artificial structure layer.
[0082] like Figure 3 As shown, the primary ore layer is located at the bottom and below the sidewalls of the open pit, serving to bear the upper load and isolate the open pit from the underground mining area; the high-strength artificial structure layer is laid on the primary ore layer and is made of cementitious sand or concrete; the low-strength artificial structure layer is laid on the high-strength artificial structure layer, with its upper surface extending to the sidewall area of the open pit and bearing the pressure from the multi-state stockpile inside the pit.
[0083] In some embodiments, the high-strength artificial structure layer and the low-strength artificial structure layer are composed of different proportions of cementitious sand or concrete.
[0084] It is worth mentioning that in some embodiments, the mine safety isolation layer only includes the primary ore layer, but the thickness of the primary ore layer is relatively large, which reduces the mining efficiency. In some embodiments, the mine safety isolation layer includes the primary ore layer and a high-strength artificial structure layer. Compared with this structure, in this application, a low-strength artificial structure layer is used to replace part of the high-strength artificial structure layer. By reducing the strength, the overall thickness of the safety isolation layer is increased, and the overall structural stability of the mine safety isolation layer is improved. At the same time, the cost of the high-strength artificial structure layer is higher than that of the low-strength artificial structure layer. By setting the low-strength artificial structure layer, the manufacturing cost of the safety isolation layer is reduced while improving the structural stability of the mine safety isolation layer, making the mine safety isolation layer of this application more practical.
[0085] In some embodiments, the thickness of the primary ore layer is: 15-30 meters at the bottom of the pit, such as 15 meters, 16 meters, ... 25 meters, 26 meters, 27 meters, 28 meters, 29 meters, 30 meters, etc., not limited to the example values; and 20-40 meters at the side walls, such as 20 meters, 21 meters, ... 30 meters, 31 meters, 32 meters, 33 meters, 34 meters, 35 meters, etc., not limited to the example values.
[0086] The thickness of the high-strength artificial structure layer is 15-30 meters, such as 15 meters, 16 meters... 19 meters, 20 meters, 21 meters, 22 meters, 30 meters, etc., not limited to the values in the examples.
[0087] The thickness of low-strength artificial structure layers ranges from 20 to 60 meters, such as 20 meters, 21 meters... 40 meters, 41 meters, 42 meters, 43 meters, 44 meters, 45 meters, 46 meters, 47 meters, 48 meters, 49 meters, 50 meters, 51 meters, 52 meters, 53 meters, 54 meters, 55 meters... 60 meters, etc., and is not limited to the values shown in the examples.
[0088] The strength of the high-strength artificial structure layer is ≥4MPa; the strength of the low-strength artificial structure layer is ≥1.5MPa. This application's mine safety isolation layer, through a scientifically designed structure (primary ore layer + high-strength artificial structure layer + low-strength artificial structure layer), systematically solves the problem of cascading disasters caused by insufficient strength and unreasonable thickness of the safety isolation layer in traditional methods. It ensures a dual isolation effect between open-pit pressure and underground mining disturbance, significantly improving mine safety and resource continuity, and providing reliable technical support for a safe and efficient transition from open-pit to underground mining.
[0089] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.
[0090] Although embodiments of this application have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting this application. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of this application.
Claims
1. A design method for a mine safety isolation layer, characterized in that, include: A three-dimensional numerical simulation model was constructed, which included the geological body, the mining area, the multi-state stockpile, and the proposed safety isolation layer. The rock mass damage evolution process was described by a rock mass constitutive model based on strain softening. The strength of the safety isolation layer is determined based on the load applied to the multi-state stack to prevent the safety isolation layer from being damaged and collapsing; Along the outline of the primary ore strata, multiple unstable mining areas were selected to excavate spaces of predetermined spans. Numerical simulations were used to determine the critical collapse height at each location. The thickness of the safety isolation layer was designed to be greater than any critical collapse height, so that the safety isolation layer could achieve self-stabilization.
2. The mine safety isolation layer design method according to claim 1, characterized in that, The safety isolation layer includes the primary ore layer, and the stope is located below the primary ore layer; The initial thickness range of the primary ore strata is obtained by using empirical formulas, limit equilibrium methods, proportional span methods, or by comparing with similar mines at home and abroad.
3. The mine safety isolation layer design method according to claim 2, characterized in that, The method for optimizing the thickness of the primary ore-bearing rock layer is as follows: Define the pit bottom and sidewalls of the primary ore-bearing strata; First, optimize the thickness of the primary ore layer at the bottom of the pit, and then determine the thickness of the primary ore layer at the sidewalls. Numerical models were established for the thickness of primary ore layers at different pit bottoms and sidewalls. The damage degree and safety factor distribution of the primary ore layer calculation unit during underground mining were calculated under different thickness values to determine whether the primary ore layer meets the self-stability condition. Then, by comparing the displacement change law of the key point position under different thickness values, the optimized thickness of the primary ore layer was determined.
4. The mine safety isolation layer design method according to claim 3, characterized in that, The safety isolation layer also includes a high-strength artificial structure layer set on top of the primary ore layer and a low-strength artificial structure layer set on top of the high-strength artificial structure layer. The strength of the high-strength artificial structure layer and the low-strength artificial structure layer is such that when the open pit is filled with multi-state mass, the in-situ stress state of the high-strength artificial structure layer and the low-strength artificial structure layer as a whole should be below the overall strength envelope curve of the high-strength artificial structure layer and the low-strength artificial structure layer, so that the high-strength artificial structure layer and the low-strength artificial structure layer as a whole are not destroyed by the multi-state mass.
5. The mine safety isolation layer design method according to claim 4, characterized in that, The in-situ stress state of the high-strength and low-strength artificial structures was obtained by establishing a three-dimensional numerical simulation model and extracting the maximum and minimum principal stresses of the layer region from the calculation results. The strength envelopes of the high-strength and low-strength artificial structures were determined by fitting the triaxial compression test data of the 28-day standard-cured specimens of the construction materials.
6. The mine safety isolation layer design method according to claim 4, characterized in that, By excavating a predetermined span of exposed space at the most unstable stope in the primary ore layer at the bottom of the pit, and using numerical simulation to determine the critical collapse height in the high-strength artificial structure layer, the design thickness of the high-strength artificial structure layer is calculated by multiplying the critical height by the safety factor.
7. The mine safety isolation layer design method according to claim 6, characterized in that, By excavating a predetermined span of exposed space at the highest point of the primary ore layer on the sidewall, and using numerical simulation to determine the critical collapse height within the low-strength artificial structure layer, the elevation benchmark value of the top of the low-strength artificial structure layer is calculated by multiplying the critical collapse height by a safety factor. Finally, the design thickness of the low-strength artificial structure layer is determined by calculating the vertical distance between this benchmark value and the top surface of the high-strength artificial structure layer.
8. The mine safety isolation layer design method according to claim 7, characterized in that, Using numerical simulation, the entire process of underground mining and backfilling is simulated according to the mining process. The high-stress primary ore and rock layers are excavated and calculated. The collapse simulation of the excavated roof is carried out to obtain the collapse height of the high-strength artificial structure layer or the low-strength artificial structure layer. Alternatively, physical simulation can be used to simulate the entire process of underground mining and backfilling according to the mining process. After excavating and monitoring the original rock structure with large deformation, the collapse of high-strength or low-strength artificial structures can be simulated to obtain the height of the collapse of high-strength or low-strength artificial structures. The maximum value of collapse of the high-strength or low-strength artificial structure layer is determined by comparing numerical simulation and physical simulation, and the thickness of the high-strength or low-strength artificial structure layer is calculated based on the collapse height.
9. A mine safety isolation layer, characterized in that, Including those set from bottom to top: The primary ore strata, located at the bottom and below the side walls of the open pit, serve to bear the upper load and isolate the open pit from the underground mining area; A high-strength artificial structure layer is laid on top of the primary mineral rock layer; A low-strength artificial structure layer is laid on top of the high-strength artificial structure layer, with its upper surface extending to the sidewall area of the open pit and bearing the pressure from the multi-state pile body inside the open pit.