A filling method for underground multi-layer one-step mining

Abstract

The present invention relates to the field of underground mining filling, and relates to an underground multi-layer one-step mining filling method, comprising the following steps: establishing a comparative filling scheme according to the mechanical characteristics of a filling body; the mechanical characteristics of the filling body include the strength of the filling body; the comparative filling scheme includes a homogeneous filling scheme and a zonal filling scheme; the homogeneous filling scheme includes the setting of filling strength; using numerical simulation software Flac3D to perform simulation calculations in combination with the actual situation of the mine, and performing comparative analysis on the results to obtain a final filling scheme. The present application reduces the ash-sand ratio, reduces costs, increases the tailings filling volume, and reduces the subsequent tailings processing and stacking volume on the basis of ensuring that the one-step mining filling meets the safety requirements of the two-step mining.

Description

Technical Field

[0001] The invention relates to the field of underground mining and filling, and in particular to an underground multi-layer one-step mining and filling method. Background Art

[0002] The underground stope recovery is divided into one-step recovery, two-step recovery and three-step recovery. The recovery order is first one-step recovery, then two-step recovery, and finally recovery. After the first-step recovery, it is necessary to fill the filling body as the roof support column before the second-step recovery. The filling method and strength of the first-step recovery are very important. If the filling strength is not enough, the filling body of the first-step recovery will collapse, causing safety hazards. In addition, the filling body is mixed into the stope, and it is easy to block the chute when the ore is discharged. There will be a phenomenon of running muddy in the ore dressing link, which will lead to difficulties in ore dressing and directly affect the production of concentrate. If the filling strength of the first-step recovery is too large, the ash-sand ratio will inevitably be large and the cost will be high. At present, the commonly used filling method for the first-step recovery is the homogeneous filling of 2MPa with a strength of 28 days in the first-step recovery. The first-step recovery adopted by the prior art adopts homogeneous filling, and the filling strength of 2MPa is required for 28 days. Its filling strength can meet the requirements, but its ash-sand ratio is high. When the filling concentration is 62%, the ash-sand ratio is generally above 1:8, so the demand for binder materials is large and the cost is high. The underground filling tailings are used less, resulting in an increase in the amount of surface tailings treatment, which is not conducive to tailings treatment. The amount of tailings piled in the tailings pond increases, which is not conducive to environmental protection. Summary of the invention

[0003] The purpose of the present invention is to provide a filling method for underground multi-layered one-step mining. On the basis of ensuring that the one-step mining filling meets the safety requirements of the two-step mining, the lime-sand ratio is reduced, that is, the ratio of the cementing material and the tailings is reduced, the amount of cementing material used will be reduced, and the cost will be reduced. The reduction of the lime-sand ratio will lead to an increase in the amount of underground tailings filling, thereby reducing the amount of surface tailings, reducing the surface stacking site, and is beneficial to environmental protection. Here, the filling material is mainly composed of cementing materials and tailings. The decrease in the lime-sand ratio refers to a decrease in the filling ratio of the cementing material and the tailings, which will lead to a decrease in the use of cementing materials and an increase in the use of tailings filling; after the lime-sand ratio is reduced, the use of filling cementing materials will be reduced, and the use of underground filling tailings will increase, resulting in less tailings to be stacked and processed on the surface.

[0004] To achieve the above object, the present invention proposes the following technical solution: a filling method for underground multi-layered one-step mining, comprising the following steps:

[0005] A comparative filling scheme is established according to the mechanical characteristics of the filling body; the mechanical characteristics of the filling body include the strength of the filling body; the comparative filling scheme includes a homogeneous filling scheme and a zonal filling scheme; the homogeneous filling scheme includes the setting of the filling strength; the zonal filling scheme includes sequentially designing the lower filling zone, the lower reinforcement belt, the waist reinforcement belt, the upper filling zone and the top reinforcement belt; and planning the position of each zone or belt and the lime-sand ratio of each zone or belt to ensure the actual strength of each zone or belt;

[0006] The numerical simulation software Flac3D was used to carry out simulation calculations in combination with the actual situation of the mine, and the results were compared and analyzed to obtain the final filling plan.

[0007] As an improved technical solution of the present application, the numerical simulation software Flac3D is used to perform simulation calculations in combination with the actual conditions of the mine, including:

[0008] Obtaining rock mechanics parameters required for numerical simulation software Flac3D calculations;

[0009] Design boundary conditions for numerical simulation software Flac3D to verify the rationality of numerical simulation;

[0010] The judgment criteria used in numerical simulation are as follows: the main indicators are shear safety factor, tensile stress size and distribution, and the secondary indicators include maximum compressive stress, maximum roof subsidence, and maximum horizontal displacement; after numerical simulation, the larger the shear safety factor, the better the safety, and the smaller the tensile stress failure depth, the better the safety. In addition, the failure position and depth of tensile stress can provide a basis for the layout of the filling zone; the final judgment result is based on the main indicators, and the secondary indicators are for reference only;

[0011] Through the numerical simulation software Flac3D, combined with the actual situation of the mine, a plane strain model was established for simulation calculation, and the results were compared and analyzed to obtain the final filling plan.

[0012] As an improved technical solution of this application, the rock mechanical parameters include filler lime-sand ratio, density, cohesion (c), internal friction angle The elastic modulus (E) and Poisson's ratio (u) of the filling, as well as the tensile strength.

[0013] As an improved technical solution of the present application, the boundary conditions used in the design numerical simulation software Flac3D include: for the theoretical boundary, the Flac3D displacement and stress boundary conditions are directly applied; the vertical displacement of the filling body is observed. If the displacement reaches 1.0 cm, it means that the calculated plane strain model is closer to the actual underground site, and the empirical boundary is no longer applied at this time; otherwise, the empirical boundary is applied, and the initial command built into Flac3D is re-adopted to initialize the stresses in the x, y, and z directions inside the grid to perform calculations at this stage; wherein the empirical boundary is the displacement of the filling body in the z direction, which is set to 1.0 cm; the theoretical boundary is a plane strain model, which constrains the horizontal displacement of the boundaries on both sides of the model, the vertical displacement of the lower boundary, and the normal displacement of the entire model, and also includes the arrangement of uniform loads on the upper part of the model.

[0014] As an improved technical solution of the present application, the zone-type filling solution includes a common filling zone and a reinforcement zone, wherein the reinforcement zone is located at the lower part (bottom), upper part (top), and waist (middle) of the empty zone.

[0015] As an improved technical solution of the present application, for underground multi-layered one-step mining areas with a height of between 25m and 45m, a two-zone two-belt mode is adopted, namely, a bottom filling zone, an upper filling zone, a bottom reinforcement zone, and a top reinforcement zone.

[0016] As the improved technical solution of this application, the bottom filling area is mainly filled with the mine trench, the filling height is from the bottom of the stope to 1.5m below the mine trench, and the 28-day strength is 0.7MPa; filling ratio: lime-sand ratio 1:15, concentration 62% to 63%; actual strength 0.7 to 0.9Mpa;

[0017] The upper filling area is located above the bottom reinforcement belt and below the upper reinforcement belt. The filling height is determined according to the actual situation of the mining site. The 28-day strength is 1.2MPa; the filling ratio: ash-sand ratio is 1:12, the concentration is 62%~63%; the actual 28-day strength is 1.2~1.24MPa.

[0018] As an improved technical solution of the present application, the bottom reinforcement belt is located above the bottom common filling area, the filling height is from the bottom reinforcement belt to the top of the second layered rock drilling tunnel, and the 28-day strength is 2.0MPa; the filling ratio is: lime-sand ratio 1:8, concentration 62% to 63%; the actual 28-day strength is 2.0 to 2.1MPa;

[0019] Top reinforcement belt top filling: located above the upper filling area, with a height of not less than 7.5m, which can be adjusted according to the actual situation of the mining site, with a 28-day strength of 2.0MPa; filling ratio: ash-sand ratio 1:8, concentration 62%~63%; actual 28-day strength 2.0~2.1MPa.

[0020] As an improved technical solution of the present application, for underground multi-layered one-step mining areas with a height of between 40m and 50m, a three-zone three-belt mode is adopted, namely, bottom filling area, middle filling area, upper filling area, bottom reinforcement belt, middle reinforcement belt, and top reinforcement belt.

[0021] As an improved technical solution of the present application, the zone elevation position can be controlled in the actual filling by the following three methods: by theoretically calculating the volume of different zones, the zone elevation position can be controlled by controlling the filling volume during filling; the position of some zones is just at the bottom or top of the closed wall. When the filling slurry is filled to this position, the sealing wall will be damp, and even water will seep out, thereby realizing the control of the zone elevation position; when the upper part of some mining areas is not closed, stones are tied with marked ropes and thrown into the empty area, so that the filling progress can be judged, thereby realizing the control of the zone elevation position. The above three methods can be used in combination in actual filling.

[0022] Beneficial effects:

[0023] It can be seen from the above technical solutions that the advantages of the technical solutions of the present invention are as follows:

[0024] 1. Compared with the ordinary method, the zone filling method has improved safety.

[0025] 2. Reduce the lime-sand ratio and reduce filling costs. Taking a mine in Anhui as an example, the average amount of cementitious materials used in one-step filling is reduced by 33.4% compared with the 2.0MPa homogeneous filling solution, and the economic benefits are very considerable. The lime-sand ratio means the ratio of cementitious materials to tailings. This technology can reduce the lime-sand ratio. For example, the lime-sand ratios of the bottom filling area and the upper filling area are very low. After the lime-sand ratio is reduced, it means that the amount of cementitious materials used will be reduced, and the amount of tailings used will increase. The increase in the use of tailings means that the utilization of tailings is improved. More tailings are used for underground filling, so there is no need to pile a large amount of tailings into the tailings pond. Tailings are polluting to the environment, so less tailings are piled on the surface to protect the surface environment.

[0026] 3. Increase the amount of tailings filling and reduce the amount of subsequent tailings processing. Tailings need to be stored in tailings ponds, and the tailings ponds need to be monitored for safety, environment, and maintenance. The reduction of tailings can reduce the use and maintenance of tailings ponds, thereby reducing costs and better protecting the environment.

[0027] 4. Through numerical simulation, comparative filling schemes can be designed, and the stress-displacement change patterns of the ore body and after filling and mining can be found very intuitively, as well as the areas that are prone to damage. By combining the actual damage conditions on site as verification, it is helpful to guide the design of underground filling schemes.

[0028] It should be appreciated that all combinations of the foregoing concepts, as well as additional concepts described in greater detail below, may be considered to be part of the inventive subject matter of the present disclosure, provided such concepts are not mutually inconsistent.

[0029] The foregoing and other aspects, embodiments and features of the present invention can be more fully understood from the following description in conjunction with the accompanying drawings. Other additional aspects of the present invention, such as the features and / or beneficial effects of the exemplary embodiments, will be apparent from the following description or learned from the practice of the specific embodiments according to the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] The drawings are not intended to be drawn to scale. In the drawings, each identical or nearly identical component shown in various figures may be represented by the same reference numeral. For clarity, not every component is labeled in every figure. Embodiments of various aspects of the present invention will now be described by way of example and with reference to the accompanying drawings, in which:

[0031] Figure 1 Cross-section diagram of filling arrangement in zone 2 of a mine;

[0032] Figure 2 Schematic diagram of filling in the 24401 mining area.

[0033] In the figure, 1: first layer rock drilling tunnel, 2: mine exit trench, 3: second layer rock drilling tunnel, 4: third layer rock drilling tunnel, 5: profile direction, 6: elevation, 7: mining site name, 8: ore body boundary, 9: top reinforcement belt, 10: upper filling area, 11: bottom reinforcement belt, 12: bottom filling area. DETAILED DESCRIPTION

[0034] In order to make the purpose, technical solution and advantages of the embodiment of the present invention clearer, the technical solution of the embodiment of the present invention will be clearly and completely described below in conjunction with the drawings of the embodiment of the present invention. Obviously, the described embodiment is a part of the embodiment of the present invention, not all of the embodiments. Based on the described embodiment of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention. Unless otherwise defined, the technical terms or scientific terms used herein should be the common meanings understood by people with ordinary skills in the field to which the present invention belongs.

[0035] Figure 1 Cross-section diagram of filling arrangement in zone 2 of a mine;

[0036] Figure 2 Schematic diagram of filling in the 24401 mining area.

[0037] In the figure, the first-layer rock drilling tunnel 1, the mine cut ditch 2, the second-layer rock drilling tunnel 3, the third-layer rock drilling tunnel 4, the profile direction 5, the elevation 6, the mining area name 7, the ore body boundary 8, the top reinforcement belt 9, the upper filling area 10, the bottom reinforcement belt 11, and the bottom filling area 12.

[0038] A filling method for underground multi-layer one-step mining comprises the following steps:

[0039] (a) Establish comparative filling schemes based on the mechanical characteristics of the filling body:

[0040] The mechanical characteristics of the filling body include the strength of the filling body; the comparative filling scheme includes a homogeneous filling scheme and a zonal filling scheme; the homogeneous filling scheme includes the setting of the filling strength; the zonal filling scheme includes sequentially designing the trench filling area, the lower reinforcement belt, the lower filling area, the waist reinforcement belt, the upper filling area and the top reinforcement belt, and planning the position of each area or belt and the ash-sand ratio of each area or belt to ensure the actual strength of each area or belt; the zonal filling scheme includes a common filling area and a reinforcement belt, wherein the reinforcement belt is located at the lower part (bottom), upper part (top), and waist (middle) of the empty area.

[0041] In actual filling, the zone elevation position can be controlled by the following three methods: by theoretically calculating the volume of different zones, the zone elevation position can be controlled by controlling the filling volume during filling; the location of some zones is just at the bottom or top of the closed wall. When the filling slurry is filled to this position, the closed wall will be damp, and even water will seep out, thereby achieving the control of the zone elevation position; when the upper part of some mining areas is not closed, stones are tied with marked ropes and thrown into the empty area, so as to judge the filling progress and then achieve the control of the zone elevation position. The above three methods can be used in combination in actual filling.

[0042] (b) The numerical simulation software Flac3D is used to perform simulation calculations based on the actual situation of the mine, and the results are compared and analyzed to obtain the final filling plan.

[0043] The numerical simulation software Flac3D is used to simulate the actual situation of the mine, including:

[0044] (1) Obtaining rock mechanical parameters required for numerical simulation software Flac3D calculation; the rock mechanical parameters include filler lime-sand ratio, density, cohesion (c), internal friction angle The elastic modulus (E) and Poisson's ratio (u) of the filling, as well as the tensile strength.

[0045] (2) Designing boundary conditions for numerical simulation software Flac3D to verify the rationality of numerical simulation; the boundary conditions for numerical simulation software Flac3D include: for theoretical boundaries, directly using Flac3D displacement and stress boundary conditions to apply; observing the vertical displacement of the filling body, if the displacement reaches 1.0 cm, it means that the calculated plane strain model is close to the actual underground site, and no empirical boundary is applied at this time; otherwise, the empirical boundary is applied, and the initial command built into Flac3D is used again to initialize the stress in the x, y, and z directions of the grid to perform calculations at this stage; wherein the empirical boundary is the displacement of the filling body in the z direction, which is set to 1.0 cm; the theoretical boundary is a plane strain model, which constrains the horizontal displacement of the boundaries on both sides of the model, the vertical displacement of the lower boundary, and the normal displacement of the entire model, and also includes arranging a uniform load on the upper part of the model.

[0046] (3) The judgment criteria used in numerical simulation are: the main indicators are shear safety factor (Fs), tensile stress size and distribution, and the secondary indicators are maximum compressive stress, maximum roof subsidence, and maximum horizontal displacement. After numerical simulation, the larger the safety factor, the better the safety; the smaller the tensile stress failure depth, the better the safety; in addition, the tensile stress failure position and depth can provide a basis for the layout of the filling zone; the final judgment result is based on the main indicators, and the secondary indicators are only for reference. Regardless of whether the filling body is destroyed or not, there will always be a potential shear failure surface, that is, a potential sliding surface, and a corresponding shear safety factor Fs (safety factor). Using Fs as the judgment standard, the stability of the filling body can be better evaluated, and the whole process from the generation to the penetration of the potential sliding surface can be obtained. However, Fs also has shortcomings. Using the size of Fs as the judgment standard can reflect the shear strength of the filling body, but cannot reflect the stability of the filling body under tensile stress, that is, the filling body will be partially subjected to tensile stress and produce tensile failure. Therefore, this simulation also monitors the tensile stress of the filling body, including the distribution range and value, which complements Fs as a criterion for determining the stability of the filling body. At the same time, there are also indicators such as maximum compressive stress, maximum roof subsidence, and maximum horizontal displacement.

[0047] The steps to obtain the safety factor are as follows:

[0048] (1) Using the built-in fish language of Flac3D, the lower limit of the safety factor is set to 1 and the upper limit is set to 8.

[0049] (2) Use the binary method to continuously adjust the upper and lower limits. First, set the maximum shear strength to calculate until convergence, record the number of running steps N, then restore normal parameters and use strength reduction. If it can converge within N calculation steps, it means that the reduction degree is small, then increase the lower limit of the reduction factor, otherwise reduce the upper limit of the reduction factor.

[0050] (3) Obtain the safety factor. The accuracy value is preset to 0.02, that is, when the difference between the upper and lower limits of the updated safety factor is less than 0.02, the current value of the folding coefficient can be regarded as the safety factor.

[0051] (4) The larger the safety factor, the more beneficial it is to the empty area of ​​the mining area.

[0052] The method of obtaining indicators such as tensile stress size and distribution, maximum compressive stress, maximum roof subsidence, and maximum horizontal displacement is as follows:

[0053] (1) Using the built-in history function of Flac3D, monitoring points can be arranged at appropriate locations to monitor displacement and stress, such as monitoring the subsidence of the top plate in the excavation area. After the calculation is completed, the historical record curve of stress-displacement changes can be exported through the plot command.

[0054] (2) Through the plot command, you can also export stress, displacement and plastic zone cloud maps, which can clearly show the stress distribution, displacement changes and plastic zone distribution (destruction zone), and can read the maximum and minimum values ​​through the cloud map.

[0055] Through the numerical simulation software Flac3D, combined with the actual situation of the mine, a plane strain model was established for simulation calculation, and the results were compared and analyzed to obtain the final filling plan.

[0056] In actual application, for underground multi-layered one-step mining, the height reaches between 25m and 45m. At this time, the mining field generally reaches three layers, and a two-zone two-belt mode is adopted, namely the bottom filling zone, the upper filling zone, the bottom reinforcement zone and the top reinforcement zone. Because according to the results of numerical simulation, the zone filling method has a higher safety factor than the homogeneous filling method, a smaller tensile stress damage depth, and more advantages for the stability of the empty area. The self-sustaining stability of the one-step filling body mainly has three weak links: the top, the bottom and a certain area of ​​the waist. Improving the strength of a certain area of ​​these three parts can significantly improve the stability of the filling body. Since the bottom is the mine trench, there are trench pillars to protect the filling body, so the filling strength does not need to be too high, and it is set as the bottom filling area; the upper area of ​​the bottom filling area is a weak link. According to numerical simulation, tensile stress failure occurs in a small local area between 8-15m above the bottom plate, so the filling strength of a certain range in the upper part of the bottom filling area should be large, and it is arranged as a bottom reinforcement belt; tensile stress failure occurs at the top, so the top area needs to have a large filling strength and is arranged as a top reinforcement belt. The bottom filling area is mainly filled with the mine trench, and the filling height is from the bottom of the mining field to 1.5m below the mine trench, with a 28-day strength of 0.7MPa±0.1MPa; filling ratio: ash-sand ratio 1:15, concentration 62%~63%; actual strength 0.7~0.9Mpa.

[0057] The upper filling area is located above the bottom reinforcement belt and below the upper reinforcement belt. The filling height is determined according to the actual situation of the mining site. The 28-day strength is 1.2MPa; the filling ratio: ash-sand ratio is 1:12, the concentration is 62%~63%; the actual 28-day strength is 1.2~1.24MPa.

[0058] The bottom reinforcement belt is located above the bottom ordinary filling area. The filling height is from the bottom reinforcement belt to the top of the second layered rock drilling tunnel, with a 28-day strength of 2.0MPa; filling ratio: ash-sand ratio 1:8, concentration 62%~63%; actual 28-day strength 2.0~2.1MPa.

[0059] Top reinforcement belt top filling: located above the upper filling area, with a height of not less than 7.5m, which can be adjusted according to the actual situation of the mining site, with a 28-day strength of 2.0MPa; filling ratio: ash-sand ratio 1:8, concentration 62%~63%; actual 28-day strength 2.0~2.1MPa.

[0060] For underground multi-layered one-step mining sites, the height reaches between 40m and 50m, and the three-zone three-belt mode is adopted, namely the bottom filling zone, the middle filling zone, the upper filling zone, the bottom reinforcement zone, the middle reinforcement zone and the top reinforcement zone. Because according to the numerical simulation results, the zone filling method has a higher safety factor than the homogeneous filling method, and the tensile stress failure depth is small. The self-supporting stability of the one-step filling body mainly has three weak links: the top, the bottom and a certain area of ​​the waist. Improving the strength of a certain area of ​​these three parts can significantly improve the stability of the filling body. Since the bottom part belongs to the mining trench and there are trench pillars to protect the filling body, the filling strength does not need to be too high and is set as the bottom filling area. The upper area of ​​the bottom filling area is the weak link. According to numerical simulation, tensile stress damage occurs in a very small local area between 8-15m above the bottom plate. Therefore, the filling strength of a certain range above the bottom filling area should be large and is arranged as a bottom reinforcement belt. Tensile stress damage occurs at the top, so the top area needs to have a large filling strength and is arranged as a top reinforcement belt. In the simulation, 25-30m is the middle reinforcement belt. In order to enhance the effect, the thickness of the middle reinforcement belt is arranged to be 7.5m.

[0061] The present invention is aimed at one-step mining of multiple segmented stopes and performs zonal filling, and the specific steps include: establishing a comparative filling plan.

[0062] The specific steps are as follows:

[0063] 1. Establish comparative filling schemes based on the mechanical characteristics of the filling body

[0064] According to the mechanical characteristics of the filling body, 4 comparative filling schemes (can also be 2, 3, 5 or more) are established, and simulation analysis is performed through simulation software (Flac3D). In this comparative scheme, the homogeneous filling schemes are A1 and A2, and the zonal filling schemes are B1 and B2, as shown in the following table:

[0065] Table 1 Filling scheme

[0066]

[0067] Table 2 Strength requirements of B1 scheme

[0068] Zonal classification high 28 days required strength Lime-sand ratio concentration Actual strength Trench filling area 0-9m 0.7MPa 1：15 62％-63％ 0.7-0.9MPa Lower reinforcement belt 9-14m 2MPa 1：8 62％-63％ 2.0-2.1MPa Lower filling area 14-25m 1.2MPa 1：12 62％-63％ 1.2-1.24MPa Waist reinforcement belt 25-30m 2MPa 1：8 62％-63％ 2.0-2.1MPa Upper filling area 30-42m 1.2MPa 1：12 62％-63％ 1.2-1.24MPa Top reinforcement belt 42-50m 2MPa 1：8 62％-63％ 2.0-2.1MPa

[0069] Table 3 Strength requirements of B2 solution

[0070] Zonal classification high 28 days required strength Lime-sand ratio concentration Actual strength Trench filling area 0-9m 0.7MPa 1：15 62％-63％ 0.7-0.9MPa Lower reinforcement belt 9-14m 2MPa 1：8 62％-63％ 2.0-2.1MPa Lower filling area 14-25m 1.2MPa 1：12 62％-63％ 1.2-1.24MPa Waist reinforcement belt 25-30m 2.5MPa 1：6 62％-63％ 2.46-2.49MPa Upper filling area 30-42m 1.2MPa 1：12 62％-63％ 1.2-1.24MPa Top reinforcement belt 42-50m 2.5MPa 1：6 62％-63％ 2.46-2.49MPa

[0071] 2. Collect and determine mechanical parameters

[0072] Numerical simulation calculations require the use of rock mechanics parameters, including the density, elastic modulus, Poisson's ratio, cohesion, internal friction angle, shear strength parameters of the filling body, tensile strength, etc. of the upper wall surrounding rock, lower wall surrounding rock, and ore body, which can be comprehensively determined by the following methods:

[0073] (1) Some mechanical parameters are included in the preliminary design and the previous goaf filling test report, including the density, elastic modulus, Poisson's ratio, cohesion, internal friction angle, and tensile strength of the hanging wall surrounding rock, the footwall surrounding rock, and the ore body;

[0074] (2) The values ​​of the backfill shear strength parameters (c) and tensile strength (a) can be obtained from existing test reports or from indoor tests. By interpolating the test data, the backfill parameter values ​​corresponding to each compressive strength can be obtained.

[0075] (3) The elastic modulus (E) and Poisson's ratio (u) of the filling body can be obtained from existing test reports or from indoor test results. The elastic modulus of the filling body is generally between 0.2-12 GPa, and the Poisson's ratio is between 0.20-0.35. If the data measured in the test is too different from the general law, it will be discarded and the test data will be repeated. If the data is reasonable, the average value will be taken to determine it.

[0076] In addition, although the proportions of the filling bodies are different, the measured density of the filling bodies is not much different, such as Figure 1 As shown, taking a certain mine as an example, all of them are between 1800-1850kg / m 2 Within the range, it can be taken as 1830kg / m 2 The specific rock mechanical parameter values ​​of a certain mine are shown in Table 4 below.

[0077] Table 4 Specific rock mechanical parameters of a mine

[0078]

[0079] 3. Determination of boundary conditions

[0080] After underground blasting mining, a void will be formed in the mining area, and deformation will occur on the top and both sides of the void. Ideally, the deformation can be calculated and predicted more accurately using relevant theoretical calculations. However, a notable feature of engineering construction is uncertainty. Taking the top descent as an example, there are many factors affecting the top descent, including its own lithology, the lithology of the surrounding rock mass, the existence of natural joints inside the excavation, the specific geological structure in the excavation range, the excavation depth, the stope structure, the excavation sequence and other factors. Therefore, the deformation and force of the top of the void are very complex. Therefore, in engineering practice, construction experience and its empirical model are sometimes particularly important.

[0081] The solution of the above process can only be achieved by determining the boundary conditions. In this simulation, the combination of on-site engineering experience and the general law of rock mass deformation is fully considered. That is, the combination of "theoretical boundary" and "empirical boundary". The details are as follows:

[0082] (1) Theoretical boundary. This is a plane strain model, which constrains the horizontal displacement of the two side boundaries of the model, the vertical displacement of the lower side boundary, and the normal displacement of the entire model. In addition, considering that the ore body is 400m deep, a uniform load is arranged on the upper part of the model. The specific method is to use the built-in function fix of Flac3D to set the normal direction velocity of all points on the lower boundary of the model boundary and all points on the two side boundaries to 0, and use the built-in function apply of Flac3D to apply a downward vertical force on the upper surface of the model to replace the gravity of the upper rock layer.

[0083] (2) Empirical boundary. It refers to the boundary conditions determined based on experience. It is an artificial boundary imposed to understand the stress and deformation state of a specific structure. Due to the bleeding and solidification shrinkage of the slurry, even if measures are taken to ensure the filling and tapping top, there will be a certain gap between the filling pillars and the top plate after solidification. This gap is mainly related to the height and concentration of the last filling. Combined with the actual filling of a certain mine and the model grid division, 1.0 cm is taken in this calculation.

[0084] (3) Implementation method. For the theoretical boundary, the displacement and stress boundary conditions of Flac3D are directly applied. Specifically, the built-in function fix of Flac3D is used to set the normal velocity of all points on the lower boundary and all points on the two sides of the model boundary to 0. The built-in function apply of Flac3D is used to apply a downward vertical force on the upper surface of the model to replace the gravity of the upper rock layer. In a specific calculation stage, the vertical displacement of the filling body is observed. If the displacement reaches 1.0 cm, it means that the calculation model is close to the actual situation on site. At this time, the empirical boundary is no longer applied; otherwise, the empirical boundary is applied and the calculation of this stage is repeated. The specific implementation method is to use the initialization command of Flac3D itself to apply the empirical boundary, that is, through initial, the initial stress in the x, y, and z directions is set for the internal grid of the model.

[0085] In summary, this simulation calculation uses theoretical boundaries to determine the solution conditions of the model, uses empirical boundaries to consider the actual working conditions on site, and uses reasonable methods to process it, which can not only reflect the actual working conditions of the mining site, but also make the simulation more efficient.

[0086] 4. Determination of the basis for judgment

[0087] In this simulation calculation, it is necessary to determine the failure conditions applicable to the filling body, that is, the basis for judgment. The constitutive model used in this simulation is the MC model (Mohr-Coulomb criterion), combined with the strength reduction method for judgment.

[0088] According to the strength reduction method theory, whether the filling body is destroyed or not, there will always be a potential shear failure surface, that is, a potential sliding surface, and a corresponding safety factor Fs. Taking Fs as the judgment standard, the stability of the filling body can be better evaluated, and the whole process from the generation to the penetration of the potential sliding surface can be obtained. However, Fs also has shortcomings. Taking the size of Fs as the judgment standard can reflect the shear strength of the filling body, but it cannot reflect the stability of the filling body under tensile stress, that is, the filling body will be partially subjected to tensile stress and produce tensile failure. Therefore, this simulation also monitors the tensile stress of the filling body, including the distribution range and numerical value, which complements Fs as a criterion for determining the stability of the filling body.

[0089] The steps to obtain the safety factor are as follows:

[0090] (1) Using the built-in fish language of Flac3D, the lower limit of the safety factor is set to 1 and the upper limit is set to 8.

[0091] (2) Use the binary method to continuously adjust the upper and lower limits. First, set the maximum shear strength to calculate until convergence, record the number of running steps N, then restore normal parameters and use strength reduction. If it can converge within N calculation steps, it means that the reduction degree is small, then increase the lower limit of the reduction factor, otherwise reduce the upper limit of the reduction factor.

[0092] (3) Obtain the safety factor. The accuracy value is preset to 0.02, that is, when the difference between the upper and lower limits of the updated safety factor is less than 0.02, the current value of the folding coefficient can be regarded as the safety factor.

[0093] (4) The larger the safety factor, the more beneficial it is to the empty area of ​​the mining area.

[0094] How to obtain indicators such as the magnitude and distribution of tensile stress, maximum compressive stress, maximum roof subsidence, and maximum horizontal displacement;

[0095] (1) Using the built-in history function of Flac3D, monitoring points are arranged at appropriate locations to monitor displacement and stress, such as monitoring the subsidence of the top plate in the excavation area. After the calculation is completed, the historical record curve of stress-displacement changes can be exported through the plot command.

[0096] (2) Through the plot command, you can export stress, displacement and plastic zone cloud maps, which can clearly show the stress distribution, displacement changes and plastic zone distribution (destruction area), and can read the maximum and minimum values ​​through the cloud map.

[0097] In summary, the judgment criteria used in this simulation are: ① Shear safety factor; ② Tensile stress magnitude and distribution. In addition, we should also pay attention to indicators such as maximum compressive stress, maximum roof subsidence, and maximum horizontal displacement.

[0098] 5. Calculation results and analysis

[0099] Through the simulation software (Flac3D), the simulation calculation was carried out in combination with the actual situation of the mine, and the results were compared and analyzed. The results are shown in Table 5.

[0100] Table 5 Comparison of calculation results of four schemes

[0101]

[0102]

[0103] The calculation results are analyzed as follows:

[0104] (1) In general, the zone filling method has more advantages in terms of void zone stability;

[0105] (2) In terms of tensile failure, the tensile stress failure depth of the zone filling is less than that of the homogeneous filling. In addition, the zone filling arrangement can make the tensile stress mainly concentrated on the top, waist, and bottom, indicating that the zone filling arrangement can better bear the transfer stress, thereby reducing the overall deformation of the filling body and ensuring the overall stability of the filling body;

[0106] (3) The compressive stress of the filling body changes slightly. Without considering the local stress concentration, it is basically the self-weight stress. The maximum compressive stress is located at the bottom, which is about 1.45MPa±0.1MPa.

[0107] (4) In terms of deformation, regardless of the form of the filling body, the maximum vertical displacement is near the top area. The difference is that for the zonal filling structure, compression deformation also occurs on the non-air-facing side inside, which is determined by the special structure of the zonal structure. In general, the zonal filling structure slows down the stress release process of the surrounding rock, or transfers the surrounding rock stress to a deeper depth, thereby reducing its own deformation.

[0108] (5) In terms of safety performance, the mechanical properties of the filling body of the zonal filling structure are better than those of the homogeneous filling method;

[0109] (6) There are three main weak links in the self-supporting stability of a step filling body: the top, the bottom and a certain area of ​​the waist. Improving the strength of these three areas can significantly improve the stability of the filling body.

[0110] 6. Specific filling plan for the first-step mining site

[0111] According to the simulation results and the actual situation of the on-site filling body collapse, the zonal filling is superior to the homogeneous filling mode. The focus of the zonal filling is to arrange the three weak links of the one-step filling body, namely the top, bottom and waist area. The zonal filling needs to be divided into ordinary filling area and reinforcement belt, where the reinforcement belt is located at the bottom, top and waist of the empty area.

[0112] For mining areas with a height of 30m±0.1MPa to 40m±0.1MPa, the mining areas are generally divided into three layers, and a two-zone two-belt mode can be adopted, namely, bottom filling area, upper filling area, bottom reinforcement belt, and top reinforcement belt.

[0113] Since the bottom of the mining area is the mining trench and is protected by pillars, it is divided into the bottom ordinary filling area, which is mainly used to fill the mining trench. The filling height is from the bottom of the mining area to 1.5m below the mining trench. The 28-day strength is 0.7MPa±0.1MPa; filling ratio: ash-sand ratio 1:15, concentration 62%~63%; actual strength 0.7~0.9MPa.

[0114] The bottom reinforcement belt is located above the bottom common filling area, and the filling height is from the bottom reinforcement belt to the top of the second layered rock drilling tunnel, with a 28-day strength of 2.0MPa; filling ratio: lime-sand ratio 1:8, concentration 62% to 63%; actual 28-day strength 2.0 to 2.1MPa;

[0115] The upper filling area is located above the bottom reinforcement belt and below the upper reinforcement belt. The filling height is determined according to the actual situation of the mining site, with a 28-day strength of 1.2MPa; filling ratio: ash-sand ratio 1:12, concentration 62%~63%; actual 28-day strength 1.2~1.24MPa.

[0116] Top reinforcement belt top filling: located above the upper filling area, with a height of not less than 7.5m, which can be adjusted according to the actual situation of the mining site, with a 28-day strength of 2.0MPa; filling ratio: ash-sand ratio 1:8, concentration 62%~63%; actual 28-day strength 2.0~2.1MPa.

[0117] For the mining area with a height of 40m to 50m, a three-zone three-belt mode can be adopted, namely the bottom filling area, the middle filling area, the upper filling area, the bottom reinforcement belt, the middle reinforcement belt, and the top reinforcement belt. According to the numerical simulation results and the actual collapse of the mining area, the collapse of the empty area will form a big belly area, which is generally located in a certain range above the middle. Only when the collapse of the big belly area is large enough, the top of the empty area is easy to collapse. Therefore, the middle reinforcement belt starts from the third layer bottom plate and is arranged upward for about 7.5m. The specific height can be adjusted according to the actual height of the on-site layer and the collapse situation. The other zones and belts are the same as the two-zone two-belt method. In order to increase the effect, the 28-day strength of the middle reinforcement belt and the bottom reinforcement belt can be arranged to be 2.5MPa.

[0118] 6. Control method of elevation position in different zones

[0119] The zone elevation position can be controlled in the actual filling process in the following three ways:

[0120] 1. The volume of different zones is calculated theoretically, and the zone elevation position is controlled by controlling the filling volume during filling;

[0121] 2. The location of some zones is just at the bottom or top of the closed wall. When the filling slurry is filled to this location, the closed wall will be damp, and even water will seep out, so that the zone elevation position can be controlled;

[0122] 3. When the upper part of some mining areas is not closed, some stones can be tied with a marked rope and thrown into the empty area, so as to judge the filling progress and realize the control of the zone elevation position;

[0123] The above three methods can be used in combination in actual filling.

[0124] Specific applications:

[0125] The height of the 24401 stope in a mine in Anhui exceeds 30m, and it is divided into three layers. A 2-zone 2-area filling structure scheme is adopted, such as Figure 2 As shown, the details are as follows:

[0126] Bottom Fill Area

[0127] Mainly fill the mine trench, the filling height is about 8.0m, the filling volume is about 2867m 3 Designed 28-day strength 0.7MPa±0.1MPa; Filling ratio: lime-sand ratio 1:15, concentration 62%~63%; Actual strength 0.7~0.9MPa. Bottom reinforcement belt

[0128] The filling height is 7.3m, reaching the top level of the -355m segmented rock drilling tunnel, and the filling volume is about 5904m 3 Designed 28-day strength 2.0MPa; Filling ratio: lime-sand ratio 1:8, concentration 62% to 63%; Actual 28-day strength 2.0 to 2.1MPa;

[0129] Upper filling area

[0130] The filling height is 20m, reaching the level of 7.2m above the top of the -342.5m rock drilling tunnel, and the filling volume is about 18470m 3 The designed 28-day strength is 1.2MPa; filling ratio: lime-sand ratio 1:12, concentration 62% to 63%; the actual 28-day strength is 1.2 to 1.24MPa.

[0131] Top reinforcement belt

[0132] Top filling: average height is about 7.8m, filling volume is about 8367m 3 The designed 28-day strength is 2.0MPa; filling ratio: lime-sand ratio 1:8, concentration 62% to 63%; the actual 28-day strength is 2.0 to 2.1MPa.

[0133] 24401 Stope zone filling parameters

[0134] Filling structure Thickness(m) Design strength(MPa) Lime-sand ratio concentration(%) Actual strength (MPa) <![CDATA[Filling volume (m 3 )]]> Bottom Fill Area 8.0 0.7 1:15 62～63 0.7～0.9 2867 Bottom reinforcement belt 7.3 2.0 1:8 62～63 2.0～2.1 5904 Upper filling area 20.0 1.2 1:12 62～63 1.2～1.24 18470 Top reinforcement belt 7.8 2.0 1:8 62～63 2.0～2.1 8367

[0135] The total filling volume is calculated to be 35608m 3 The filling volume of high-strength reinforcement belt is 14271m 3 , accounting for 40% of the total filling volume, and the ordinary filling area accounts for about 60% of the total filling volume, which can significantly reduce costs. The filling material is mainly composed of cementing materials and tailings. The decrease in the lime-sand ratio refers to the decrease in the filling ratio of cementing materials and tailings, which will lead to a decrease in the use of cementing materials and an increase in the use of tailings filling, which can reduce the stacking of tailings and is beneficial to environmental protection.

[0136] Although the present invention has been disclosed as above with preferred embodiments, it is not intended to limit the present invention. A person with ordinary knowledge in the technical field to which the present invention belongs may make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, the protection scope of the present invention shall be determined by the definition of the claims.

Claims

1. A filling method for underground multi-layer one-step mining, It is characterized in that The steps include: A comparative filling scheme is established according to the mechanical characteristics of the filling body; the mechanical characteristics of the filling body include the strength of the filling body; the comparative filling scheme includes a homogeneous filling scheme and a zonal filling scheme; the homogeneous filling scheme includes the setting of the filling strength; the zonal filling scheme includes sequentially designing the trench filling area, the lower reinforcement belt, the lower filling area, the waist reinforcement belt, the upper filling area and the top reinforcement belt, and planning the position of each area or belt and the lime-sand ratio of each area or belt to ensure the actual strength of each area or belt; The numerical simulation software Flac3D was used to conduct simulation calculations in combination with the actual situation of the mine, and the results were compared and analyzed to obtain the final filling plan; The simulation calculation using numerical simulation software Flac3D combined with the actual situation of the mine includes: Obtaining rock mechanics parameters required for numerical simulation software Flac3D calculations; Design boundary conditions for numerical simulation software Flac3D to verify the rationality of numerical simulation; The judgment criteria used in numerical simulation are as follows: the main indicators are shear safety factor, tensile stress size and distribution, and the secondary indicators include maximum compressive stress, maximum roof subsidence, and maximum horizontal displacement; after numerical simulation, the larger the shear safety factor, the better the safety, and the smaller the tensile stress failure depth, the better the safety. In addition, the failure position and depth of tensile stress can provide a basis for the layout of the filling zone; the final judgment result is based on the main indicators, and the secondary indicators are for reference only; Through the numerical simulation software Flac3D, combined with the actual situation of the mine, a plane strain model was established for simulation calculation, and the results were compared and analyzed to obtain the final filling plan.

2. A filling method for underground multi-layered one-step mining according to claim 1, It is characterized in that The rock mechanics parameters include filler body ash-sand ratio, density, cohesion, internal friction angle, elastic modulus and Poisson's ratio of the filler body, and tensile strength.

3. A filling method for underground multi-layered one-step mining according to claim 1, It is characterized in that The boundary conditions used in the design numerical simulation software Flac3D include: for the theoretical boundary, directly using the Flac3D displacement and stress boundary conditions to apply; observing the vertical displacement of the filling body, if the displacement reaches 1.0 cm, it means that the calculated plane strain model is closer to the actual underground site, and the empirical boundary is no longer applied at this time; otherwise, the empirical boundary is applied, and the built-in initial command of Flac3D is re-adopted to initialize the stresses in the x, y, and z directions inside the grid to perform calculations at this stage; wherein the empirical boundary is the displacement of the filling body in the z direction, which is set to 1.0 cm; the theoretical boundary is a plane strain model, which constrains the horizontal displacement of the boundaries on both sides of the model, the vertical displacement of the lower boundary, and the normal displacement of the entire model, and also includes arranging a uniform load on the upper part of the model.

4. A filling method for underground multi-layered one-step mining according to claim 1, It is characterized in that The zone filling scheme includes a common filling zone and a reinforcement zone, wherein the reinforcement zone is located at the lower part, the upper part, and the waist of the empty zone.

5. A filling method for underground multi-layered one-step mining according to claim 1, It is characterized in that For underground multi-layered one-step mining areas with a height of 25m to 45m, a two-zone two-belt mode is adopted, namely, the bottom filling zone, the upper filling zone, the bottom reinforcement zone, and the top reinforcement zone.

6. A filling method for underground multi-layered one-step mining according to claim 5, It is characterized in that The bottom filling area is mainly filled with the mine trench, and the filling height is from the bottom of the stope to 1.5m below the mine trench. The 28-day strength is 0.7MP; filling ratio: lime-sand ratio 1:15, concentration 62%~63%; actual strength 0.7~0.9Mpa; The upper filling area is located above the bottom reinforcement belt and below the upper reinforcement belt. The filling height is determined according to the actual situation of the mining site, with a 28-day strength of 1.2MPa; filling ratio: ash-sand ratio 1:12, concentration 62%~63%; actual 28-day strength 1.2~1.24MPa.

7. A filling method for underground multi-layered one-step mining according to claim 5, It is characterized in that The bottom reinforcement belt is located above the bottom common filling area. The filling height is from the bottom reinforcement belt to the top of the second layered rock drilling tunnel. The 28-day strength is 2.0MPa. The filling ratio is 1:8 for lime-sand ratio and the concentration is 62% to 63%. The actual 28-day strength is 2.0 to 2.1MPa. Top reinforcement belt top filling: located above the upper filling area, with a height of not less than 7.5m, which can be adjusted according to the actual situation of the mining site, with a 28-day strength of 2.0MPa; filling ratio: ash-sand ratio 1:8, concentration 62%~63%; actual 28-day strength 2.0~2.1MPa.

8. A filling method for underground multi-layered one-step mining according to claim 1, It is characterized in that For underground multi-layered one-step mining areas with a height of 40m to 50m, a three-zone three-belt mode is adopted, namely, the bottom filling area, the middle filling area, the upper filling area, the bottom reinforcement belt, the middle reinforcement belt and the top reinforcement belt.

9. A filling method for underground multi-layered one-step mining according to claim 1, It is characterized in that The zone elevation position can be controlled in actual filling by the following three methods: by theoretically calculating the volume of different zones, the zone elevation position can be controlled by controlling the filling volume during filling; the position of some zones happens to be at the bottom or top of the closed wall. When the filling slurry is filled to this position, the closed wall will be damp, and even water will seep out, thereby achieving the control of the zone elevation position; when the upper part of some mining areas is not closed, stones are tied with marked ropes and thrown into the empty area, so that the filling progress can be judged, thereby achieving the control of the zone elevation position; the above three methods can be used in combination in actual filling.

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