Prediction method for tectonic stress type metal mine overlying strata caving height

Abstract

The invention provides a method for predicting the caving height of overlying strata of a tectonic stress type metal mine. The method is suitable for predicting the caving height of the overlying strata in a goaf of the tectonic stress type metal mine. The method mainly comprises the following steps that a metal mine stratum space geometric model is established, an ore body layered mining scheme is designed, and the boundary position of a layered goaf is determined; analyzing goaf upper and lower wall surrounding rock structure types and distribution characteristics, establishing a composite structure upper and lower wall rock mass failure instability calculation model, obtaining goaf upper and lower wall surrounding rock failure widths, and further determining the maximum potential span of tectonic stress type metal mine goaf overlying strata caving; a goaf overlying strata caving arch height calculation model under the rainfall infiltration condition is established, and the goaf overlying strata caving height after ore body mining is finished is predicted. By means of the method, the tectonic stress type metal mine goaf overburden caving height development can be accurately predicted, and a powerful guarantee is provided 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, and in particular to a method for predicting the caving height of overburden rock 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-access route, the collapsed ore is transported from the end of the access route to the chute using trackless equipment under the cover of the collapsed rock, and the covering rock that follows the descent of the ore is used to fill the goaf. However, the collapse of the overburden rock will not only cause dynamic impact to 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 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 strata in the mining area. Accurately grasping the evolution law of overburden collapse and predicting the vertical distance of the overburden stratum being destroyed and moved after the mining of the ore body, that is, the overburden collapse height, is crucial to the scientific design of mining plans and to ensure safe and efficient mining of mines.

[0003] Metal mines are mostly found in mountainous areas. The surrounding rock structure of the mines is significantly affected by the geological tectonic movement before and after mineralization. There is a high horizontal tectonic stress inside the surrounding rock, so most of them belong to tectonic stress type mines. The surrounding rock joints closer to the ore body are more developed, the ore body joints are densely developed and less regular, and the steeply inclined structural surface of the distant ore body is obviously developed. The formation of extremely high goafs will lead to a large release of horizontal tectonic stress inside the upper and lower plate rock bodies, which will cause serious movement and damage of the upper and lower plate surrounding rocks. These damages will expand the horizontal extension range of overburden collapse. Therefore, it is important to determine the structural characteristics of the upper and lower plate rock bodies in advance (the upper plate is above or above the ore body, and the lower plate is below or below the ore body) and reveal its movement and damage mechanism driven by horizontal tectonic stress. It is an important prerequisite for accurately predicting the height of overburden collapse in steep ore body metal mines. In addition, these steeply inclined structural surfaces provide convenient channels for rainwater to seep downward. The infiltration of rainwater greatly reduces the effective stress in the overburden rock mass, significantly weakens the stability of the overburden rock, and greatly increases the possibility of overburden collapse 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 the overburden in coal mines 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 height of overburden collapse in a tectonic stress type metal mine, comprising the following steps:

[0006] 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;

[0007] 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;

[0008] 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:

[0009]

[0010] Among them, h0 is the collapse height of the overburden rock, K0 is the lateral pressure coefficient of the ground stress in the mining area, 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 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.

[0011] 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;

[0012] 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;

[0013] h1=h c / sinβ1;

[0014] 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);

[0015] 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 surrounding rock near the ore body in the footwall is The bulk density γ2 of the rock mass in the lower plate and the elastic modulus E of the rock formation.

[0016] Further, the step 2 comprises:

[0017] 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:

[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, 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;

[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 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.

[0021] When the fragmented structure of the surrounding rock near the mine is relatively wide, the calculation formula for the 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 upper wall and the bottom angle of the upper wall of the goaf;

[0023] 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:

[0024] 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;

[0025] 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;

[0026] 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.

[0027] 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:

[0028] 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:

[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 area 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 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;

[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 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;

[0034] 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;

[0035]

[0036] in, It is the critical length of the steeply dipping rock strata 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 It 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 plate far mine;

[0041] Figure 4 It is a stress analysis diagram of overburden rock 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 near the mine with fragmented structure in the upper and lower walls is relatively wide;

[0044] Figure 7 This is a state diagram when the rock mass 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 solution and advantages of the embodiments disclosed in the present invention clearer, the technical solution 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., 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 layer and mineral quality change laws, and various geological factors affecting the normal and safe production and construction of mines.

[0048] The geological cross section can provide the following information about the goaf and the rock mass in the upper and lower walls:

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

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

[0051] Stress distribution in rock mass.

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

[0053] The goaf height 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 the 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 rock strata refers to the vertical distance from the surface to the bottom of the hanging rock strata of the ore body.

[0060] The position coefficient of 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 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 equivalent force. When the horizontal stress on both sides of the cantilever beam is a uniformly distributed load, the point of action of equivalent concentrated force is exactly at the midpoint of the side of the cantilever beam, that is, the position coefficient of 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 mutual engagement 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 stratum on the side of the goaf due to loss of support after the ore body is mined during underground mining.

[0063] Example 1

[0064] The following is a detailed description of the specific implementation methods of the present invention by taking a Hubei Daye iron mine after the horizontal segmented ore body of the -312m goaf floor is mined as an example in conjunction with the accompanying drawings:

[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 an iron ore mine in Daye, Hubei Province is shown, and a spatial distribution model of the strata in the mining area is established; based on the geometric spatial distribution form of the ore body and the stratified mining plan of the ore body, the boundary position of the stratified goaf area 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 upper plate strata z1 = 362m, the inclination angle of the steeply inclined surface of the upper plate rock mass is β1 = 70°, the thickness of the cantilever beam strata in the steeply inclined structure rock mass far from the upper plate is h1, h1 = h c / sinβ1=59.6m; the width of the rock mass near the ore in the footwall L2 is 15~35m, with an average value of 25m, and the inclination angle of the steeply inclined surface of the rock mass in the footwall β2=83°;

[0068] 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 = 1.5, the bulk density of the groundwater in the mining area 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 rock collapse in the goaf was measured by laboratory rock shear test. like Figure 3 As shown in the figure, 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 overlying rock layer in the goaf area is mainly densely jointed horn shale, and the overlying rock layer bulk density γ=25.1kN / m 3 , cohesion c = 0.3MPa, and the internal friction angle of the overburden layer measured by laboratory rock shear test is

[0069] The physical parameters of the strata in the mining area include: the surrounding rock of the upper plate far from the mine is mainly hornfels, the inclination of the steeply dipping rock layer in the upper plate deviates from the direction of the ore body, and this kind of rock structure is called a steeply dipping reverse dipping structure. The bulk density of the surrounding rock of the upper plate far from the mine is γ1=25.1kN / m 3 , tensile strength of surrounding rock strata of 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 the 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 lower plate is igneous rock with a steeply inclined and down-dipping structure. The rock mass of the lower plate is γ2 = 27 kN / m 3 , rock layer elastic modulus E = 9.0GPa.

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

[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 steeply inclined rock mass far from the upper (lower) wall, the surrounding rock near the mine in the upper (lower) wall of the mining area will develop a fragmented structure. Starting from the bottom angle of the upper (lower) wall of the goaf on the geological profile, 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 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 shattered structure near the mine in the lower wall upward. When the rock mass with shattered structure near the mine in the upper wall is relatively wide, the intersection of the sliding surface of the rock mass with shattered structure near the mine in the upper wall and the horizontal extension line of the top plate of the goaf is located inside the rock mass with shattered 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 shattered structure near the mine in the upper wall and the horizontal extension line of the top plate of the goaf and the boundary of the first goaf is the destruction width L1 of the rock mass with shattered structure near the mine in the upper wall, as shown in Figure 6 As shown;

[0074] The L1 calculation formula is:

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

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

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

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

[0079] If the rock mass of the surrounding rock near the mine in the footwall 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 fragmented structures near the mine in the middle and upper walls 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 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 steeply inclined rock mass far from the upper (lower) wall, the surrounding rock near the mine in the upper (lower) wall of the mining area will develop a fragmented structure. Starting from the bottom angle of the upper (lower) wall of the goaf on the geological profile, 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 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 upward. When the rock mass with fragmented structure near the mine in the upper wall is narrow, the intersection of the sliding surface of the rock mass with fragmented structure near the mine in the upper wall and the horizontal extension line of the roof of the goaf is located inside the steeply inclined rock mass far from the mine in the upper wall. In this case, the rock mass with fragmented structure near the mine in the upper wall and the steeply inclined rock mass far from the mine in the upper wall of the entire width are subjected to sliding failure. Therefore, the span of the overburden collapse in the goaf on the upper wall is: like Figure 7 As shown;

[0085] When the fragmented structure rock mass near the mine in the lower wall surrounding rock is relatively narrow, the intersection of the sliding surface of the fragmented structure rock mass near the mine in the lower wall surrounding rock and the horizontal extension line of the goaf roof is located inside the steeply inclined structure rock mass far from the mine in the lower wall. In this case, the fragmented structure rock mass near the mine in the lower wall surrounding rock and the steeply inclined structure rock mass far from the mine in the lower wall of the entire width are subjected to sliding failure. Therefore, the span of the overburden collapse in the goaf on the lower wall side is: like Figure 7 As shown;

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

[0087] Figure 7 The rock masses with fragmented structures near the mine in the middle and upper walls are relatively narrow;

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

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

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

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

[0092] When the surrounding rock mass near the mine and the upper and lower walls have no developed fractured structure;

[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=12.6m of the rock mass in this area at the level of the roof of the goaf.

[0095] The fragmentation structure of the surrounding rock near the ore in the footwall of the mining area is developed. The fragmentation structure of the surrounding rock near the ore 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 in the footwall loses the lateral support of the original ore body and undergoes overall sliding failure toward the goaf. Figure 5 As shown in the figure, after the horizontal segmented ore body mining of the -312m goaf floor is completed, from the bottom corner of the footwall of the goaf floor, the inclination angle Draw the sliding surface of the rock mass with fragmented structure near the mine in the lower wall upwards. The sliding surface of the rock mass with fragmented structure near the mine in the lower wall first intersects with the horizontal plane of the top plate of the goaf. The intersection point is located inside the rock mass area with fragmented structure near the mine in the lower wall, which belongs to the working condition type of case 1 mentioned above. The distance between the intersection point and the boundary of the first goaf is the destruction width L2 of the rock mass with fragmented structure near the mine in the lower wall. The destruction width of the rock mass with fragmented structure near the mine in the lower wall surrounding rock can be calculated as L2=32.0m, such as Figure 5 shown.

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

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

[0098] For the above conditions:

[0099] The damage width B1 of the steeply inclined rock mass in the upper plate far from the mine at the level of the goaf roof is derived based on the cantilever beam theory and the limit equilibrium calculation method to obtain the mechanical calculation equation for the damage and instability of the steeply inclined rock mass in the upper plate far from the mine.

[0100] 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;

[0101] by Figure 5 For example, the steeply inclined structural 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 toward the goaf. First, we can calculate p1=K0γ1z1=14MPa. On this basis, the quadratic equation of the failure width B1 of the steeply inclined structural rock mass in the upper plate 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 rock mass of the surrounding rock near the mine in the lower wall 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 rock mass of the rock mass near the mine in the lower wall at the level of the goaf roof is L2 = 32.0m. Figure 5As shown in the figure, the shear-slip failure surface of the shattered rock mass of the surrounding rock near the mine in the footwall is only developed in the shattered rock mass of the surrounding rock near the mine in the footwall (fault fracture zone), and has not reached the interface between the shattered rock mass of the surrounding rock near the mine in the footwall and the steeply inclined rock mass of the far mine in the footwall, and then developed to the steeply inclined rock mass area (igneous rock) far mine in the footwall. Therefore, the steeply inclined rock mass of the far mine in the footwall remains stable under the lateral support of the shattered rock mass near the mine, and no buckling failure occurs. When the shattered rock mass of the surrounding rock near the mine in the footwall is not developed, the failure width B2=0 of the steeply inclined rock mass of the far mine in the footwall at the level of the roof of the goaf.

[0107] If the shear-slip damage of the shattered rock mass near the mine in the footwall surrounding rock develops to the steeply inclined rock mass area far from the mine in the footwall, that is, the shattered rock mass near the mine in the footwall surrounding rock is relatively narrow, the calculation formula for the damage width of the steeply inclined rock mass far from the mine in the footwall at the roof level of the goaf is derived 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 surrounding rocks at the level of the goaf roof.

[0111] Step 3: As the overburden cracks in the goaf of the mine are highly developed, after considering that rainwater fully infiltrates 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 balance 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 sum of uniformly distributed loads on the upper surface of the overburden in the goaf of micro-element thickness, 2cdz represents the cohesion of the overburden in the goaf of micro-element thickness, 2K0σ V′ dz represents the lateral pressure of the overburden in the goaf with micro-element thickness; where 2B is the potential maximum span of overburden collapse, γ is the bulk density of overburden rock, c is the cohesion of overburden rock, K0 is the lateral pressure coefficient of 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 balance differential equation of the overburden in the goaf area with the above micro-element thickness is:

[0115]

[0116] Where A is the integral 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 the rainfall has fully infiltrated, that is, the gravity load of the covering soil layer after the 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 It is 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 infiltrates the cracks of the overburden rock, the fracture water pressure u at depth z in the overburden rock 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 which 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, causing the horizontal thrust on both sides of the overburden in the goaf to decrease, and then the vertical friction resistance decreases when the overburden slides down, and the overburden in the goaf gradually relaxes and eventually collapses. According to Terzaghi's vertical earth pressure calculation principle, dividing both sides of the above formula by γ can obtain the formula for calculating the arch height of the overburden:

[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 ground stress in the mining area, 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] The gravity load P0 of the mining area's covering soil layer under rainfall conditions 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 = 306m, substituting P0 = 0 and z = 306m into formula (IV), the vertical effective relaxation pressure of the overburden rock mass when the mine is mined to the level of -312m can be determined as:

[0130]

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

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

[0133]

[0134] Although 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 the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present 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 collapse height of the overburden rock, K0 is the lateral pressure coefficient of the ground stress in the mining area, 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 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 bulk density γ2 of the rock mass in the lower plate and the elastic modulus E of the rock formation.

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 fragmented structure of the surrounding rock near the mine is relatively wide, the calculation formula for the damage 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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