A method for predicting the collapse height of overburden rock in tectonic stress metal mines

Abstract

The present invention provides a method for predicting the collapse height of overburden rock in a tectonic stress type metal mine, which is suitable for predicting the collapse height of overburden rock in goaf areas of tectonic stress type metal mines. The method mainly includes the following steps: establishing a spatial geometric model of the metal mine strata, designing a stratified mining plan for the ore body, and determining the boundary position of the stratified goaf area; analyzing the structural type and distribution characteristics of the surrounding rock of the upper and lower plates of the goaf area, establishing a calculation model for the destruction and instability of the rock mass of the upper and lower plates of the composite structure, and obtaining the destruction width of the surrounding rock of the upper and lower plates of the goaf area, thereby determining the maximum potential span of overburden rock collapse in the goaf area of ​​tectonic stress type metal mines; establishing a calculation model for the height of the overburden rock falling arch in the goaf area under rainfall infiltration conditions, and predicting the collapse height of the overburden rock in the goaf area after the ore body mining is completed. This method can accurately predict the development of the collapse height of overburden rock in the goaf area of ​​tectonic stress type metal mines, providing a strong guarantee for mine mining design and safe and efficient production.

Description

Technical Field

[0001] The invention relates to the technical field of metal mine caving mining, in particular to a method for predicting the caving height of overburden in a tectonic stress type metal mine. Background Art

[0002] The caving method is widely used in the mining of metal mines with steep ore bodies. Steep ore bodies refer to ore deposits with a large inclination angle (usually greater than 45°, and sometimes even close to vertical). This type of ore body presents a steep angle as it extends from the surface to the underground. Through the upward fan-shaped deep hole caving drilled by the self-entry route, the collapsed ore is transported from the end of the route to the chute using trackless equipment under the cover of the collapsed rock, and the covering rock following the descent of the ore fills the goaf. However, the collapse of the overburden will not only cause dynamic impact on the surrounding rock of the mining area below, thereby inducing the occurrence of rock burst events in the mining area or nearby tunnels; it will also cause a huge change in the stress distribution of the surrounding rock of the mining area, causing serious deformation and damage to the nearby tunnels. In addition, if Figure 1 As the mining of the ore body continues to extend deeper, the overburden collapse gradually expands upward and eventually penetrates the surface covering soil layer, causing the surface collapse of the mining area. Therefore, overburden collapse in metal mines is an important hidden danger to the stability of the mining area. Accurately grasping the evolution law of overburden collapse and predicting the vertical distance of the overburden stratum damage and movement after the ore body is mined, that is, the overburden collapse height, is crucial to the scientific design of mining plans and to ensure safe and efficient mining.

[0003] Metal mines are often located in mountainous areas. The structure of their surrounding rock is significantly influenced by tectonic movements before and after mineralization, resulting in high horizontal tectonic stresses within the surrounding rock. Consequently, most mines are classified as tectonic stress-induced. The closer to the ore body, the more developed the surrounding rock joints are. Joints in the ore body are densely developed and less regular. Steeply dipping structural surfaces are prominent in rock bodies farther from the ore body. The formation of extremely high goafs can lead to a significant release of horizontal tectonic stresses within the hanging and hanging wall rock masses, causing severe movement and damage in the hanging and hanging wall rock masses. This damage can expand the horizontal extent of overburden collapses. Therefore, determining the structural characteristics of the hanging and hanging wall rock masses (the hanging wall above or laterally above the ore body, and the footwall below or laterally below the ore body) in advance and revealing the mechanism of movement and failure driven by horizontal tectonic stresses is crucial for accurately predicting the height of overburden collapses in steeply dipping metal mines. Furthermore, these steeply dipping structural surfaces provide convenient pathways for downward rainwater infiltration. This infiltration significantly reduces the effective stress in the overburden rock mass, significantly weakening its stability and increasing the likelihood of overburden collapses after summer rainfall.

[0004] Existing methods for predicting the height of overburden collapse in mining are mainly concentrated in the field of coal mining technology. Since coal mine overburden is mostly distributed in a horizontal layered structure, the calculation method based on the mechanical theory of beams and plates can well predict the collapse of layered overburden. However, there is currently a lack of reliable theoretical prediction methods for determining the collapse height of overburden in tectonic stress-type metal mines. Summary of the Invention

[0005] In view of the problems in the prior art, the present invention provides a method for predicting the collapse height of overburden in tectonic stress metal mines, comprising the following steps:

[0006] Step 1. Based on the mine geological exploration data and the geological profile of the steeply inclined ore body metal mine, establish a spatial distribution model of the mining area strata and collect the physical parameters of the ore body layered goaf area and the physical parameters of the mining area strata; based on the geometric spatial distribution of the ore body and the ore body layered mining plan, determine the boundary position of the ore body layered goaf area and the spatial distribution data of the mining area strata, and divide the ore body into the hanging wall and the footwall;

[0007] Step 2. Analyze the development of the surrounding rock structures of the hanging wall and footwall of the ore body respectively based on the geological profile, draw auxiliary lines on the geological profile, calculate the damage widths L1 and L2 of the ore body's hanging wall and footwall surrounding rock near the ore catastrophic structure rock mass at the level of the goaf roof, determine the width and narrowness of the development of the ore body's hanging wall and footwall surrounding rock near the ore catastrophic structure rock mass, determine the span of the goaf overburden collapse on the hanging wall and footwall sides based on the development of the ore body's hanging wall and footwall surrounding rock structures and the width and narrowness, calculate the sum of the spans of the goaf overburden collapse on the hanging wall and footwall sides, and obtain the maximum potential span 2B for the occurrence of goaf overburden collapse;

[0008] Step 3. Determine the overburden collapse height when rainfall fully infiltrates the overburden fissures based on the preset calculation formula for the overburden collapse arch height of a steeply inclined metal mine:

[0009]

[0010] Among them, h0 is the height of overburden collapse, K0 is the lateral pressure coefficient of the mining area stress, c is the cohesion of the overburden rock mass, is the friction angle of the overburden rock mass, γ is the bulk density of the overburden rock mass, and γ w is the groundwater density in the mining area, 2B is the potential maximum span of overburden collapse, P0 is the gravity load of the covering soil layer under rainwater infiltration conditions, and z is the depth of the goaf roof; P0 = 2Bγ b h b ; γ b is the saturated bulk density of the soil layer above the overburden in the goaf, h b It is the thickness of the soil layer above the overburden in the goaf.

[0011] The boundary position of the ore body layered goaf includes: the horizontal span B3 of the first sub-level goaf, the goaf height hc after the sub-level ore body mining of the goaf floor, the goaf upper wall boundary inclination θ1, the goaf lower wall boundary inclination θ2, the goaf collapse and broken rock depth z0, and the goaf roof depth z;

[0012] The spatial distribution data of the strata in the mining area include: the buried depth of the hanging wall rock layer z1, the dip angle of the steep layer of the hanging wall rock mass β1, the thickness of the cantilever beam rock layer in the steep structure rock mass far from the mine in the hanging wall h1, and the dip angle of the steep layer of the footwall rock mass β2;

[0013] h1=h c / sinβ1;

[0014] The physical parameters of the ore body layered goaf include: the mining area ground stress lateral pressure coefficient K0, the mining area groundwater density γ w , bulk density of rock collapse in goaf γ0, internal friction angle of rock collapse in goaf The equivalent concentrated force position coefficients of horizontal stress of the cantilever beam rock layer on the goaf side and the other side, the bulk density γ of the overburden layer, the cohesion c, and the internal friction angle of the overburden layer are: χ0∈(0,1),χ1∈(0,1);

[0015] The physical parameters of the mining area include: the bulk density of the surrounding rock mass of the upper plate and the mine is γ1, the tensile strength of the surrounding rock strata of the upper plate and the mine is σ t , the internal friction angle of the cantilever beam rock layer in the surrounding rock mass of the upper plate far mine Friction coefficient of steep surface The friction angle of the surrounding rock near the ore body is The friction angle of the rock mass near the ore body in the footwall surrounding rock is The bulk density γ2 of the rock mass in the footwall of the mine and the elastic modulus E of the rock formation.

[0016] Further, the step 2 includes:

[0017] Step 21: Analyze the development of the surrounding rock structures of the hanging wall and footwall of the ore body according to the geological profile:

[0018] If the most prominent position of the upper and lower wall boundaries of the goaf is not adjacent to the corresponding upper and lower wall steeply inclined rock mass far from the mine, then the upper and lower wall surrounding rocks of the mining area have developed cataclastic structures near the mine; otherwise, the upper and lower wall surrounding rocks of the mining area have no developed cataclastic structures near the mine;

[0019] Step 22: Draw auxiliary lines on the geological section map:

[0020] If the surrounding rock of the upper and lower walls of the mining area is developed near the ore, start from the bottom corner of the upper and lower walls of the goaf on the geological section map and Draw the sliding surface of the rock mass of the surrounding rock near the mine upwards, and draw the sliding surface of the surrounding rock mass near the mine upwards. Draw the sliding surface of the cataclastic structure rock mass near the mine in the footwall surrounding rock upwards, and observe the intersection of the sliding surface of the cataclastic structure rock mass near the mine in the upper and footwall surrounding rock and the horizontal extension line of the goaf roof. If the intersection is located inside the steeply inclined structure rock mass area far from the mine in the upper and footwall surrounding rock, the cataclastic structure rock mass near the mine in the upper and footwall surrounding rock is relatively narrow. If not, the cataclastic structure rock mass near the mine in the upper and footwall surrounding rock is relatively wide.

[0021] When the fragmented structure of the surrounding rock mass near the mine is relatively wide, the calculation formula for its damage width at the level of the goaf roof is:

[0022] Where θ1 is the inclination angle of the line connecting the top angle of the hanging wall and the bottom angle of the hanging wall of the goaf;

[0023] When the rock mass of the footwall surrounding rock near the mine is relatively wide, the calculation formula for its failure width at the level of the goaf roof is:

[0024] Where θ2 is the inclination angle of the line connecting the top angle and the bottom angle of the footwall of the goaf;

[0025] If the upper and lower wall surrounding rock mass near the mine is narrow, its damage width L1 and L2 at the level of the goaf roof are the distances between the upper and lower wall steeply inclined rock mass far from the mine and the boundary of the first goaf respectively;

[0026] If the surrounding rock of the upper and lower walls of the mining area is not well developed near the ore, draw an auxiliary line parallel to the steeply inclined rock layer of the upper wall through the most prominent position of the boundary between the upper and lower walls of the goaf on the geological section map, and determine the intersection of the auxiliary line and the horizontal line of the goaf roof. The distance between the intersection and the top corners of the upper and lower walls of the goaf is L1 and L2.

[0027] Step 23: If the fragmented rock mass near the mine in the upper and lower wall surrounding rocks is relatively wide, the spans of the overburden collapse in the goaf on the upper and lower wall sides are:

[0028] If the upper and lower wall surrounding rocks have a narrow fractured structure near the mine, the spans of the overburden collapse in the goaf on the upper and lower wall sides are:

[0029] If the fragmentation structure of the surrounding rock near the upper and lower walls of the mining area is not developed, the spans of the overburden collapse in the goaf on the upper and lower walls are: And B1=0, B2=0;

[0030] B3 is the horizontal span of the segmented goaf;

[0031] Step 24: Based on the cantilever beam theory and the limit equilibrium calculation method, the failure width B1 of the steeply inclined rock mass in the upper wall far from the mine at the level of the goaf roof can be derived to obtain the mechanical equation for the failure and instability of the steeply inclined rock mass in the upper wall far from the mine.

[0032] (σ t +γ1h1sinβ1)B1 2 +3(μ0p0h1+σ1p1h1―γ1h1 2 cosβ1)B1―6(χ1p1h1 2 ―χ0p0h1 2 )=0

[0033] in, p1=K0γ1z1, p0 is the horizontal tectonic stress of the cantilever beam layer on the goaf side, and p1 is the horizontal tectonic stress of the cantilever beam layer on the other side;

[0034] The failure width B2 of the steeply inclined rock mass in the footwall far from the mine at the level of the goaf roof is calculated based on the energy principle and the calculation formula for the failure width of the steeply inclined rock mass in the footwall far from the mine at the level of the goaf roof is derived;

[0035]

[0036] in, It is the critical length of the steeply dipping rock layer in the footwall when it collapses and fails.

[0037] The beneficial effects of the present invention are: it can reasonably prevent and control various mine ground pressure disasters caused by overburden collapse in tectonic stress-type metal mines, is suitable for steeply inclined metal mines formed by violent tectonic movements, and can accurately predict the evolution law of overburden collapse height from the initial stage of ore body mining to the entire stage of surface collapse in the mining area under rainfall infiltration conditions. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 This is a schematic diagram of block cave mining;

[0039] Figure 2 This is a model diagram for calculating the arch height of overburden caving in the goaf area of ​​the present invention;

[0040] Figure 3 This is a schematic diagram of the equivalent concentrated force position of horizontal stress in the cantilever beam rock layer in the steeply inclined rock mass of the upper wall far mine;

[0041] Figure 4 This is a stress analysis diagram of overburden in goaf area with micro-element thickness under rainfall infiltration conditions in the present invention;

[0042] Figure 5 A schematic diagram of a typical geological profile of a mine and the distribution of overburden caving arches provided in an embodiment of the present invention;

[0043] Figure 6 This is a state diagram of the present invention when the rock mass of the surrounding rock and the mine fragmentation structure near the upper and lower walls are both relatively wide;

[0044] Figure 7 This is a state diagram when the rock masses of the surrounding rock and the mine fragmentation structure near the upper and lower walls of the present invention are both relatively narrow. DETAILED DESCRIPTION

[0045] In order to make the purpose, technical solutions and advantages of the embodiments disclosed in the present invention clearer, the technical solutions of the embodiments disclosed in the present invention will be clearly and completely described below in conjunction with the drawings of the embodiments disclosed in the present invention. Obviously, the described embodiments are part of the embodiments disclosed in the present invention, not all of the embodiments. Based on the described embodiments disclosed in the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection disclosed in the present invention.

[0046] Explanation of terms

[0047] Mine geological exploration data refers to original geological data, result geological data and physical geological data such as rock and mineral cores, various specimens, thin sections, samples, etc. in the form of text, charts, audio and video, electromagnetic media, etc., which are obtained through geological surveys, exploration, observation, cataloging and comprehensive analysis at various stages of mine construction, production and closure, on the mine geological structure, ore-bearing rock series, ore layers and mineral quality change patterns, and various geological factors affecting the normal and safe production and construction of mines.

[0048] Geological cross-sections can provide the following information about the goaf and the rock masses in the footwalls and wall:

[0049] The shape, size and spatial position of the goaf, including the length, width, height and relative position of the goaf to other geological structures.

[0050] The rock structure of the upper and lower walls of the goaf, including information such as the thickness, dip, lithology and bedding of the rock layers.

[0051] Stress distribution in rock mass.

[0052] Geological survey reports and exploration data usually contain information on rock mass mechanical parameters.

[0053] The height of the goaf refers to the vertical distance from the bottom plate to the top plate of the mining area after mining is completed.

[0054] The overburden collapse height refers to the vertical height to which the overburden strata are broken and collapsed due to mining activities.

[0055] Overburden refers to all rock and soil layers above the target ore body or mining area.

[0056] The hanging wall refers to the rock layer above the steeply inclined ore body.

[0057] The footwall refers to the rock layer below the steeply inclined ore body.

[0058] The lateral pressure coefficient of ground stress in a mining area (usually represented by K0) refers to the ratio of horizontal stress to vertical stress.

[0059] The burial depth of the hanging wall rock stratum refers to the vertical distance from the ground surface to the bottom of the hanging wall rock stratum of the ore body.

[0060] The position coefficient of the equivalent concentrated force of horizontal stress on the left and right sides of the cantilever beam rock formation refers to the ratio of the distance from the point of action of the equivalent concentrated force of horizontal stress to the fixed end of the cantilever beam to the length of the cantilever beam. This ratio can be calculated according to the principle of force equivalence. When the horizontal stress on both sides of the cantilever beam is a uniformly distributed load, the point of action of the equivalent concentrated force is exactly at the midpoint of the side of the cantilever beam, that is, the position coefficient of the equivalent concentrated force of horizontal stress on the left and right sides of the cantilever beam rock formation χ0 = χ1 = 0.5.

[0061] The internal friction angle of the overburden reflects the degree of interlocking and friction between rock or soil particles and is measured by rock shear test.

[0062] The cantilever beam layer on the goaf side refers to the cantilever beam-like structure formed by the rock layer on the side of the goaf due to the loss of support after the ore body is mined during underground mining.

[0063] Example 1

[0064] Below, in conjunction with the accompanying drawings, a specific embodiment of the present invention is described in detail by taking an iron mine in Daye, Hubei Province after the horizontal segmented ore body of the -312m goaf floor is mined as an example:

[0065] Step 1: Based on the mine geological exploration data, Figure 5 The geological profile of a metal mine with a steep ore body mined by the caving method in Daye, Hubei Province is shown. A spatial distribution model of the strata in the mining area is established. According to the geometric spatial distribution of the ore body and the stratified mining plan of the ore body, the boundary position of the stratified goaf of the ore body and the spatial distribution data of the strata in the mining area are determined.

[0066] The boundary positions of the stratified goaf of the ore body include: the horizontal span of the first segmented goaf B3 = 39m, the goaf height hc = 56m after the horizontal segmented ore body mining of the -312m goaf floor is completed, the overburden collapse height is equal to hc, the inclination angle of the upper wall boundary of the goaf is θ1 = 70°, the inclination angle of the lower wall boundary of the goaf is θ2 = 87°, the buried depth of the collapsed rock in the goaf is z0 = 362m, and the buried depth of the goaf roof is z = 306m.

[0067] The spatial distribution data of the strata in the mining area include: the buried depth of the hanging wall rock layer z1 = 362m, the inclination angle of the steep surface of the hanging wall rock mass is β1 = 70°, the thickness of the cantilever beam rock layer in the steep structure rock mass far from the mine in the hanging wall is h1, h1 = h c / sinβ1=59.6m; the width L2 of the footwall rock mass near the ore is 15~35m, with an average value of 25m; the dip angle β2 of the steeply inclined plane of the footwall rock mass is 83°;

[0068] The physical parameters of the ore body layered goaf include: the mining area ground stress lateral pressure coefficient K0 = 1.5, the mining area groundwater density γ w =9.8kN / m 3 The bulk density of rock fragments in the goaf is γ0 = 19.7 kN / m 3 The internal friction angle of the collapsed rock in the goaf was measured by the laboratory rock shear test. like Figure 3 As shown, the equivalent concentrated force coefficient of horizontal stress on the cantilever beam rock layer on the goaf side and the other side is χ0 = χ1 = 0.5. The overburden of the goaf is mainly densely jointed shale, and the bulk density of the overburden layer is γ = 25.1kN / m 3 , cohesion c = 0.3 MPa, and the internal friction angle of the overburden layer was measured by the laboratory rock shear test.

[0069] The physical parameters of the mining area include: the surrounding rock of the upper wall far from the ore body is mainly hornfels, the steeply dipping rock layer of the upper wall is inclined away from the direction of the ore body, and this kind of rock structure is called a steeply dipping anti-dip structure. The bulk density of the surrounding rock of the upper wall far from the ore body is γ1 = 25.1kN / m 3 , tensile strength of surrounding rock formations of the upper plate far mine σ t =3MPa, the internal friction angle of the cantilever beam rock layer in the surrounding rock mass of the upper plate far mine was measured by laboratory structural surface shear test The friction coefficient of the steep surface μ1 = 0.67, and the friction angle of the surrounding rock near the ore body is The rock mass near the ore in the footwall is a fault fracture zone. The friction angle of the rock mass near the ore in the footwall is measured by the laboratory rock shear test. The rock mass of the footwall far ore is igneous rock with a steeply inclined and down-dipping structure. The rock mass of the footwall far ore has a bulk density of γ2 = 27kN / m 3 , the elastic modulus of the rock layer is E = 9.0GPa.

[0070] Step 2: Determine the development of the cataclastic structure of the surrounding rock near the ore in the upper (lower) wall of the mining area based on the geological profile, draw auxiliary lines on the geological profile, and calculate the failure width L1 of the cataclastic structure of the surrounding rock near the ore at the level of the goaf roof according to different working conditions; and calculate the failure width L2 of the cataclastic structure of the surrounding rock near the ore at the level of the goaf roof;

[0071] Determine the maximum potential span 2B of overburden collapse in the goaf according to various working conditions:

[0072] Due to the shear slip instability failure of the near-mine fragmentation structure, the different working conditions are divided into three cases:

[0073] Case 1: If the most prominent position of the upper (lower) wall boundary of the goaf is not adjacent to the upper (lower) wall steeply inclined rock mass far from the mine, the surrounding rock of the upper (lower) wall of the mining area will develop a fragmented structure near the mine. On the geological section, starting from the bottom corner of the upper (lower) wall of the goaf, the upper wall side is inclined at an angle of Draw the sliding surface of the rock mass of the surrounding rock near the mine upwards, and draw the sliding surface of the surrounding rock mass near the mine upwards. Draw the sliding surface of the rock mass with cataclastic structure near the mine in the lower wall upward. When the rock mass with cataclastic structure near the mine in the upper wall is relatively wide, the intersection of the sliding surface of the rock mass with cataclastic structure near the mine in the upper wall and the horizontal extension line of the goaf roof is located inside the rock mass with cataclastic structure near the mine in the upper wall. In this case, the distance between the intersection of the sliding surface of the rock mass with cataclastic structure near the mine in the upper wall and the horizontal extension line of the goaf roof and the boundary of the first goaf is the destruction width L1 of the rock mass with cataclastic structure near the mine in the upper wall, as shown in Figure 1. Figure 6 As shown;

[0074] The L1 calculation formula is:

[0075] Where θ1 is the inclination angle of the goaf hanging wall boundary (the line connecting the top angle of the goaf hanging wall and the bottom angle of the hanging wall);

[0076] When the rock mass with cataclastic structure near the mine in the lower wall surrounding rock is relatively wide, the intersection of the sliding surface of the rock mass with cataclastic structure near the mine in the lower wall surrounding rock and the horizontal extension line of the goaf roof is located inside the rock mass with cataclastic structure near the mine in the lower wall surrounding rock. In this case, the distance between the intersection of the sliding surface of the rock mass with cataclastic structure near the mine in the lower wall surrounding rock and the horizontal extension line of the goaf roof and the boundary of the first goaf is the failure width L2 of the rock mass with cataclastic structure near the mine in the lower wall surrounding rock.

[0077] The L2 calculation formula is: Where θ2 is the inclination angle of the footwall boundary of the goaf (the line connecting the top angle and the bottom angle of the footwall of the goaf);

[0078] If the surrounding rock mass of the upper wall has a relatively wide fracture structure near the mine, the span of the overburden collapse in the goaf on the upper wall side is:

[0079] If the rock mass of the surrounding rock mass near the mine is relatively wide, the span of the overburden collapse in the goaf on the footwall side is:

[0080] The maximum potential span 2B of the overburden collapse in the goaf is the sum of the spans of the overburden collapse in the goaf on the hanging wall side and the footwall side;

[0081] Figure 6 The rock masses with cataclastic structures near the mine in the middle and upper wall surrounding rocks are relatively wide;

[0082] 2L=L1+L2+B3

[0083] Among them, B3 is the horizontal span of the first segmented goaf and the destruction width of various types of rock structures in the upper and lower wall surrounding rocks at the level of the goaf roof.

[0084] Case 2: If the most prominent position of the upper (lower) wall boundary of the goaf is not adjacent to the upper (lower) wall steeply inclined rock mass far from the mine, the surrounding rock of the upper (lower) wall of the mining area will develop a fragmented structure near the mine. On the geological section, starting from the bottom corner of the upper (lower) wall of the goaf, the upper wall side is inclined at an angle of Draw the sliding surface of the rock mass of the surrounding rock near the mine upwards, and draw the sliding surface of the surrounding rock mass near the mine upwards. Draw the sliding surface of the rock mass with fragmented structure near the mine in the footwall upward. When the rock mass with fragmented structure near the mine in the hanging wall is narrow, the intersection of the sliding surface of the rock mass with fragmented structure near the mine in the hanging wall and the horizontal extension line of the goaf roof is located inside the area of ​​the rock mass with steep structure far from the mine in the hanging wall. In this case, the rock mass with fragmented structure near the mine in the hanging wall and the rock mass with steep structure far from the mine in the hanging wall of the entire width will slide and fail. Therefore, the span of the overburden collapse in the goaf on the hanging wall side is: like Figure 7 As shown;

[0085] When the rock mass with fragmented structure near the mine in the footwall surrounding rock is narrow, the intersection of the sliding surface of the rock mass with fragmented structure near the mine in the footwall surrounding rock and the horizontal extension line of the goaf roof is located inside the rock mass with steep structure far from the mine in the footwall. In this case, the rock mass with fragmented structure near the mine in the footwall surrounding rock and the rock mass with steep structure far from the mine in the footwall surrounding rock of the entire width will be damaged by sliding. Therefore, the span of the overburden collapse in the goaf on the footwall side is: like Figure 7 As shown;

[0086] The maximum potential span 2L of goaf overburden collapse is the sum of the spans of goaf overburden collapse on the hanging wall side and the footwall side;

[0087] Figure 7 The rock masses with cataclasite structures near the mine in the middle and upper wall surrounding rocks are relatively narrow;

[0088] 2L=L1+L2+L1+B2+B3;

[0089] Case 3: If the most prominent position of the upper (lower) wall boundary of the goaf is adjacent to the steeply dipping rock mass of the upper (lower) wall far from the mine, the cataclastic structure of the upper (lower) wall near the mine in the mining area is not developed;

[0090] When the surrounding rock mass of the hanging wall near the mine is not developed, draw an auxiliary line parallel to the steeply inclined structural rock layer of the hanging wall through the most prominent position of the boundary of the hanging wall of the goaf on the geological section map, and determine the intersection of the auxiliary line and the horizontal line of the goaf roof. The distance between the intersection and the top corner of the hanging wall of the goaf is L1. The span of the overburden collapse of the goaf on the hanging wall side is:

[0091] When the fragmented rock mass near the mine in the footwall surrounding rock is not developed, draw an auxiliary line parallel to the steeply inclined rock layer of the footwall through the most prominent position of the footwall boundary of the goaf on the geological section map, and determine the intersection of the auxiliary line and the horizontal line of the goaf roof. The distance between the intersection and the top corner of the goaf footwall is L2. The span of the goaf overburden collapse on the footwall side is:

[0092] When the rock mass with fragmented structure near the mine and the surrounding rock of the upper and lower walls is not developed;

[0093] 2B=L1+L2+B1+B2+B3;

[0094] As Figure 5 For example, the fragmentation structure of the surrounding rock near the mine in the upper wall of the mining area is not developed, which belongs to the working condition type of the above-mentioned situation 3. The corresponding method is used to determine that the damage width L1 of the rock mass in this area at the level of the goaf roof is 12.6m.

[0095] The fragmentation structure of the surrounding rock near the ore body in the footwall of the mining area is developed. The fragmentation structure of the surrounding rock near the ore body in the footwall of the mining area is a fault fracture zone with a fragmentation structure. When the mining working face advances to the boundary of the footwall of the ore body, severe ground pressure will be generated. The fragmentation structure of the surrounding rock near the ore body in the footwall loses the lateral support of the original ore body and undergoes overall sliding failure towards the goaf. Figure 5 As shown in the figure, after the horizontal segmented ore body mining of the -312m goaf floor is completed, the bottom corner of the footwall of the goaf floor is formed at an inclination angle on the footwall side. Draw the sliding surface of the rock mass with fragmented structure near the mine in the footwall surrounding rock upwards. The sliding surface of the rock mass with fragmented structure near the mine in the footwall surrounding rock first intersects with the horizontal plane of the goaf roof. The intersection point is located inside the rock mass with fragmented structure near the mine in the footwall surrounding rock, which belongs to the working condition type 1 mentioned above. The distance between the intersection point and the boundary of the first-layer goaf is the failure width L2 of the rock mass with fragmented structure near the mine in the footwall surrounding rock. The failure width of the rock mass with fragmented structure near the mine in the footwall surrounding rock can be calculated as L2 = 32.0m. Figure 5 shown.

[0096] Figure 5 The maximum potential span 2B for overburden collapse in the goaf is:

[0097] 2B=L1+L2+B1+B2+B3;

[0098] For the above working conditions:

[0099] The failure width B1 of the steeply inclined rock mass in the upper wall at the level of the goaf roof is calculated based on the cantilever beam theory and the limit equilibrium calculation method, and the mechanical equation for the failure and instability of the steeply inclined rock mass in the upper wall is derived.

[0100] The failure width B2 of the steeply inclined rock mass in the footwall far from the mine at the level of the goaf roof is calculated based on the energy principle and the calculation formula for the failure width of the steeply inclined rock mass in the footwall far from the mine at the level of the goaf roof is derived;

[0101] by Figure 5 For example, the steeply inclined rock mass of the upper plate of the mine is close to the goaf. After the horizontal segmented ore body of the -312m goaf floor was mined, it collapsed towards the goaf. First, we can calculate p1=K0γ1z1=14MPa. On this basis, the quadratic equation of the failure width B1 of the steeply inclined rock mass in the upper wall far from the mine is constructed:

[0102] (σ t +γ1h1sinβ1)B1 2 +3(μ0p0h1+μ1p1h1―γ1h1 2 cosβ1)B1―6(χ1p1h1 2 ―χ0p0h1 2 )=0 (I)

[0103] in, p1=K0γ1z1, p0 is the horizontal tectonic stress of the cantilever beam layer on the goaf side, p1 is the horizontal tectonic stress of the cantilever beam layer on the other side, χ0 is the action position coefficient of the equivalent concentrated force of the horizontal tectonic stress of the cantilever beam layer on the goaf side, χ1 is the action position coefficient of the equivalent concentrated force of the horizontal tectonic stress of the cantilever beam layer on the other side, χ0∈(0,1), χ1∈(0,1);

[0104] Solving equation (I) can obtain the value of rock mass failure width B1.

[0105] We can get B1=42.1m, such as Figure 5 shown.

[0106] The calculation of the destruction width L2 of the catastrophic rock mass near the mine in the footwall surrounding rock of the mining area at the level of the goaf roof is as follows: Case 3, L2 = 32.0m. At this time, the actual width of the catastrophic rock mass near the mine in the footwall rock mass at the level of the goaf roof is L2 = 32.0m. Figure 5As shown in the figure, the shear slip failure surface of the catastrophic rock mass of the footwall surrounding rock near the mine is only developed in the catastrophic rock mass of the footwall surrounding rock near the mine (fault fracture zone), and does not reach the interface between the catastrophic rock mass of the footwall surrounding rock near the mine and the steeply inclined rock mass of the footwall far from the mine, and then develops to the area of ​​the steeply inclined rock mass of the footwall far from the mine (igneous rock). Therefore, the steeply inclined rock mass of the footwall far from the mine remains stable under the lateral support of the catastrophic rock mass near the mine, and no buckling failure occurs. When the catastrophic rock mass of the footwall surrounding rock near the mine is not developed, the failure width B2 of the steeply inclined rock mass of the footwall far from the mine at the level of the goaf roof is 0.

[0107] If the shear slip failure of the cataclastic rock mass near the footwall surrounding rock develops to the steeply inclined rock mass far from the footwall, that is, the cataclastic rock mass near the footwall surrounding rock is relatively narrow, the calculation formula for the failure width of the steeply inclined rock mass far from the footwall at the level of the goaf roof can be deduced based on the energy principle: Where E is the elastic modulus of the rock formation, l is the critical length of the steeply dipping rock formation at the footwall when it collapses and fails, where h c The height of the goaf can be obtained by measuring the height difference between the top plate of the first goaf and the bottom plate of the bottom goaf.

[0108] By calculating in step 2, Figure 5 The horizontal span of the first sub-section goaf is B3 = 39.0m, and the potential maximum span of the goaf overburden collapse is 2B:

[0109] 2B=L1+L2+B1+B2+B3=125.7m

[0110] Among them, B3 is the horizontal span of the first segmented goaf and the destruction width of various types of rock structures in the upper and lower wall surrounding rocks at the level of the goaf roof.

[0111] Step 3: Due to the high development of overburden cracks in the goaf of this mine, after considering the full infiltration of rainwater into the overburden cracks, according to the vertical effective lateral friction force on the overburden in the goaf of the micro-element thickness, the gravity of the overburden in the goaf of the micro-element thickness, and the vertical force on the upper and lower planes of the overburden in the goaf of the micro-element thickness, the vertical stress equilibrium differential equation of the overburden in the goaf of the micro-element thickness at a depth of z from the ground surface can be expressed as:

[0112]

[0113] Among them, Figure 4 As shown in the figure, 2Bγdz is the gravity of the overburden in the goaf with micro-element thickness; 2B(σ V′ +dσ V′ ) is the total uniform load on the lower surface of the overburden in the goaf with micro-element thickness; 2Bσ V′is the total uniform load on the upper surface of the overburden in the goaf of the micro-element thickness, 2cdz represents the cohesion of the overburden in the goaf of the micro-element thickness, 2K0σ V′ dz represents the lateral pressure of the overburden in the goaf of the micro-element thickness; where 2B is the potential maximum span of overburden collapse, γ is the bulk density of the overburden rock mass, c is the cohesion of the overburden rock mass, K0 is the lateral pressure coefficient of the ground stress in the mining area, σ v ' is the vertical effective relaxation pressure of the overburden rock mass;

[0114] The general solution of the vertical stress equilibrium differential equation of the overburden in the goaf area with the above microelement thickness is:

[0115]

[0116] Where A is the integration constant to be solved.

[0117] like Figure 4 According to the stress boundary condition of the upper surface of the overlying rock layer in the goaf, when z = 0, σ V′ =P0, we can find A in formula (III). We can find:

[0118]

[0119] P0 is the overburden load on the top surface of the overburden rock in the goaf after rainfall has fully infiltrated, that is, the gravity load of the covering soil layer after rainwater has fully infiltrated: P0 = 2Bγ b h b ;

[0120] γ b is the saturated bulk density of the soil layer above the overburden in the goaf, h b The thickness of the soil layer above the overburden in the goaf;

[0121] Substituting into formula (III), the vertical effective relaxation pressure of the overburden rock mass can be calculated as:

[0122]

[0123] When rainfall fully penetrates the overburden cracks, the crack water pressure u at the depth z in the overburden is w z, and then according to the vertical effective relaxation pressure σ of the overburden rock mass v ', overburden fracture water pressure u, overburden rock mass vertical total relaxation pressure σ v The mathematical relationship between V′ =σ V ―u, the bulk density of groundwater in the mining area is γ w Based on this, the total vertical relaxation pressure of the overburden rock mass can be calculated as:

[0124]

[0125] Rainwater seeps downward along the cracks in the overburden, reducing the horizontal thrust on both sides of the overburden in the goaf. Consequently, the vertical frictional resistance decreases as the overburden slides downward, causing the overburden in the goaf to gradually loosen and eventually collapse. Based on Terzaghi's principle for calculating vertical earth pressure, dividing both sides of the above equation by γ yields the formula for calculating the overburden arch height:

[0126]

[0127] Among them, B is half of the potential maximum span of overburden collapse, γ is the bulk density of overburden rock mass, c is the cohesion of overburden rock mass, K0 is the lateral pressure coefficient of mining area stress, σ v ' is the vertical effective relaxation pressure of the overburden rock mass, u is the overburden fracture water pressure, σ v is the total vertical relaxation pressure of the overburden rock mass, γ w is the bulk density of groundwater in the mining area;

[0128] Under rainfall conditions, the gravity load P0 of the mining area's covering soil layer refers to the gravity load on the top surface of the underlying overburden when the mining area's covering soil layer reaches a saturated state after sufficient rainfall infiltration. Figure 4 , there is no covering soil layer on the surface above the goaf, so P0=0.

[0129] When z is the depth of the goaf roof, that is, z = 306 m, and P0 = 0 and z = 306 m are substituted into formula (IV), the vertical effective relaxation pressure of the overburden rock mass when the mine is mined to the level of -312 m can be determined as:

[0130]

[0131] Substitute P0=0, z=306m into formula (V),

[0132] Substitute P0=0 and z=306m into formula (VI):

[0133]

[0134] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

Claims

1. A method for predicting the height of overburden collapse in a tectonic stress metal mine, characterized in that: The method comprises the following steps: Step 1. According to the geological exploration data of the mine and the geological profile of the steeply inclined metal mine, establish the spatial distribution model of the strata in the mining area, and collect the physical parameters of the strata in the strata of the ore body and the physical parameters of the strata in the mining area; according to the geometric spatial distribution form of the ore body and the stratified mining plan of the ore body, determine the boundary position of the strata in the strata of the ore body and the spatial distribution data of the strata in the mining area, and divide the upper wall and the lower wall of the ore body; Step 2. Analyze the development of the surrounding rock structure of the upper plate and the lower plate of the ore body respectively according to the geological profile, draw auxiliary lines on the geological profile, calculate the destruction width L1 and L2 of the surrounding rock near the ore of the upper plate and the lower plate of the ore body at the level of the top plate of the goaf, judge the width of the development of the surrounding rock near the ore of the upper plate and the lower plate of the ore body, determine the span of the overburden collapse of the goaf on the upper and lower plate sides according to the development of the surrounding rock structure of the upper plate and the lower plate of the ore body and the width, calculate the sum of the spans of the overburden collapse of the goaf on the upper and lower plate sides, and obtain the maximum potential span 2B of the overburden collapse of the goaf; Step 3. According to the preset calculation formula for the overburden collapse arch height of steeply inclined metal mines, determine the overburden collapse height when rainfall fully infiltrates the overburden cracks: Among them, h0 is the height of overburden collapse, K0 is the lateral pressure coefficient of ground stress in the mining area, c is the cohesion of overburden rock mass, is the friction angle of the overburden rock mass, γ is the bulk density of the overburden rock mass, and γ w is the density of groundwater in the mining area, 2B is the potential maximum span of overburden collapse, P0 is the gravity load of the covering soil layer under rainwater infiltration conditions, and z is the depth of the roof of the goaf; P0 = 2Bγ b h b ; γ b is the saturated bulk density of the soil layer above the overburden in the goaf, h b It is the thickness of the soil layer covering the overburden in the goaf.

2. The method according to claim 1, characterized in that The boundary position of the stratified goaf of the ore body includes: the horizontal span B3 of the first segmented goaf, the height hc of the goaf after the horizontal segmented ore body mining of the goaf floor, the inclination angle θ1 of the goaf upper wall boundary, the inclination angle θ2 of the goaf lower wall boundary, the buried depth z0 of the collapsed rock in the goaf, and the buried depth z of the goaf roof; The spatial distribution data of the strata in the mining area include: the buried depth of the hanging rock layer z1, the dip angle of the steeply inclined surface of the hanging rock mass β1, the thickness of the cantilever beam rock layer in the steeply inclined structure rock mass far from the mine in the hanging rock mass h1, and the dip angle of the steeply inclined surface of the footwall rock mass β2; h1=h c / sinβ1; The physical parameters of the stratified goaf of the ore body include: the lateral pressure coefficient of the ground stress in the mining area K0, the bulk density of the groundwater in the mining area γ w , bulk density of rock collapse in goaf area γ0, internal friction angle of rock collapse in goaf area The equivalent concentrated force position coefficients of horizontal stress of the cantilever beam rock layer on the goaf side and the other side, the bulk density γ of the overburden layer, the cohesion c, and the internal friction angle of the overburden layer are: χ0∈(0,1),χ1∈(0,1); The physical parameters of the strata in the mining area include: the bulk density of the surrounding rock mass of the upper plate far mine is γ1, the tensile strength of the surrounding rock strata of the upper plate far mine is σ t , the internal friction angle of the cantilever beam rock layer in the surrounding rock mass of the upper plate far mine Friction coefficient of steep surface The friction angle of the surrounding rock near the ore body is The friction angle of the rock mass near the ore in the footwall is The rock mass bulk density γ2 and the elastic modulus E of the rock formation in the lower plate far from the mine.

3. The method according to claim 1, characterized in that The step 2 comprises: Step 21: Analyze the development of the surrounding rock structure of the upper and lower walls of the ore body according to the geological profile: If the most prominent position of the upper and lower wall boundaries of the goaf is not adjacent to the corresponding upper and lower wall steeply inclined rock mass far from the mine, the upper and lower wall surrounding rock near the mine will have developed cataclasite structures; otherwise, the upper and lower wall surrounding rock near the mine will not have developed cataclasite structures; Step 22: Draw auxiliary lines on the geological section map: If the surrounding rock of the upper and lower walls of the mining area is well developed near the ore, start from the bottom corner of the upper and lower walls of the goaf on the geological section map and Draw the sliding surface of the rock mass of the surrounding rock near the mine on the upper wall upwards, and draw the sliding surface of the rock mass of the surrounding rock near the mine on the lower wall with an inclination angle Draw the sliding surface of the rock mass with fragmented structure near the mine in the lower wall upwards, and observe the intersection of the sliding surface of the rock mass with fragmented structure near the mine in the upper and lower walls and the horizontal extension line of the roof of the goaf. If the intersection is located inside the steeply inclined rock mass area far from the mine in the upper and lower walls, the rock mass with fragmented structure near the mine in the upper and lower walls is narrower. If not, the rock mass with fragmented structure near the mine in the upper and lower walls is wider. When the surrounding rock mass near the mine is relatively wide, the calculation formula for the destruction width at the level of the goaf roof is: Where θ1 is the inclination angle of the line connecting the top angle of the upper wall and the bottom angle of the upper wall of the goaf; When the rock mass of the surrounding rock mass near the mine is relatively wide, the calculation formula for the destruction width at the level of the goaf roof is: Where θ2 is the inclination angle of the line connecting the top angle of the footwall of the goaf and the bottom angle of the footwall; If the upper and lower wall surrounding rock near the mine fragmentation structure rock mass is relatively narrow, its damage width L1 and L2 at the level of the goaf roof are the distances between the upper and lower wall far mine steep structure rock mass and the boundary of the first goaf respectively; If the surrounding rock near the mine in the upper and lower walls of the mining area is not well developed, draw an auxiliary line parallel to the steeply inclined rock layer of the upper wall through the most prominent position of the boundary between the upper and lower walls of the goaf on the geological section map, and determine its intersection with the horizontal line of the goaf roof. The distance between this intersection and the top angle of the upper and lower walls of the goaf is L1 and L2. Step 23: If the surrounding rock mass near the mine in the upper and lower walls is relatively wide, the spans of the overburden collapse in the goaf area on the upper and lower walls are: If the surrounding rock mass of the upper and lower walls is narrow near the mine, the spans of the overburden collapse in the goaf area on the upper and lower walls are: If the fragmentation structure of the surrounding rock near the upper and lower walls of the mining area is not developed, the spans of the overburden collapse in the goaf area on the upper and lower walls are: And B1=0, B2=0; B3 is the horizontal span of the segmented goaf; Step 24: Based on the cantilever beam theory and the limit equilibrium calculation method, the failure width B1 of the steeply inclined rock mass in the upper plate far from the mine at the level of the goaf roof can be derived to obtain the mechanical calculation equation for the failure and instability of the steeply inclined rock mass in the upper plate far from the mine; (s t +γ1h1sinβ1)B1 2 +3(μ0p0h1+μ1p1h1―γ1h1 2 cosβ1)B1―6(χ1p1h1 2 ―χ0p0h1 2 )=0 in, p1=K0γ1z1, p0 is the horizontal structural stress of the cantilever beam layer on the goaf side, and p1 is the horizontal structural stress of the cantilever beam layer on the other side; The failure width B2 of the steeply inclined rock mass far from the lower wall at the level of the roof of the goaf is calculated by the calculation formula of the failure width of the steeply inclined rock mass far from the lower wall at the level of the roof of the goaf based on the energy principle; in, It is the critical length of the steeply dipping rock strata in the footwall when it collapses and fails.

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