Bottom structure optimization method for abnormal area of stope

Abstract

The invention discloses a method for optimizing a bottom structure of an abnormal area of a stope. The method comprises the following steps: calculating a break angle and a height of a peach-shaped ore pillar; a stope ore removal roadway and an ore removal access support are designed, wherein an anchor rod, metal net and sprayed concrete combined support mode is adopted; the support design method comprises the steps of support pressure calculation, anchor rod length calculation, anchor rod distance calculation, anchor rod diameter calculation, tray size calculation, anchoring agent selection, metal net and double-rib parameter selection, sprayed concrete parameter selection and grouting anchor cable parameter selection. The method has the advantages that the stability is better, and the safety is improved.

Description

Technical Field

[0001] The invention relates to the technical field of ore dressing, and in particular to a method for optimizing the bottom structure of an abnormal area in a stope. Background Art

[0002] The Secretary Gou Iron Mine is located in Zhangerkouzi Village, two kilometers west of Xiaoshetai Town, Urad Front Banner, Bayannur City, Inner Mongolia Autonomous Region. The geographical coordinates of the center of the mining area are: longitude: 109°28′30″, latitude: 41°09′46″; the iron ore bodies in the mining area are located in the gneiss section of the Serteng Mountain Group, and the main lithology is plagioclase amphibolite gneiss and mixed rock plagioclase. The mining area is divided into four abnormal areas, Ⅰ, Ⅱ, Ⅲ, and Ⅳ. Among them, the mining of ore bodies in abnormal areas Ⅰ and Ⅱ shares a production system, numbered as mining area 1; the mining of ore bodies in abnormal areas Ⅲ and Ⅳ shares a production system, numbered as mining area 2. The production systems of mining areas 1 and 2 are relatively independent. All are being mined, with ore bodies ranging in elevation from 1360m to 780m. The ore bodies in abnormal areas III and IV are nearly east-west in direction, with a total east-west length of about 1270m and a north-south width of about 530m. The second mining area is dominated by thick ore bodies, with medium-thick and thin ore bodies accounting for a smaller proportion, and are steeply inclined ore bodies. The mine design determines that thick ore bodies (thickness > 15m) will adopt the segmented rock drilling and segmented empty site subsequent filling mining method perpendicular to the ore body direction, and medium-thick ore bodies (thickness <15m) will adopt the segmented rock drilling and segmented empty site subsequent filling mining method along the ore body direction.

[0003] The thick ore body adopts the open-field and subsequent filling mining method, and the bottom mining structure adopts the form of a collection trench. The first-step mine room uses the collection tunnel of the second-step mine room to mine the ore, and tailings are used for cementation and filling after the first-step ore block mining is completed. After the filling body is stabilized, the second-step mine room is mined, and the second-step mine room uses the collection tunnel of the first-step mine room to mine the ore, and tailings are used for filling after the second-step ore block mining is completed. This results in the need for the mining tunnel of the second-step mine room to be excavated in the collection tunnel that has been filled in the first-step mine room. Due to the large amount of residual ore in the first-step collection tunnel, secondary excavation is difficult, the tunnel stability is poor, the support cost is high, and the safety is poor.

[0004] The mine then optimized and adjusted the location of the mine's exit tunnel and the bottom structure parameters, and arranged the exit tunnel inside the peach-shaped column. Taking the middle section of 975m-1030m as an example, the mine bottom exit structure design adopts the form of a collection trench, and the Simba1254 rock drilling rig is used to drill fan-shaped medium-deep holes to form a collection trench. The mine-collecting tunnel is arranged in the center of the mine room, and the vein-penetrating tunnel is used as the exit tunnel. The vein-penetrating tunnel is arranged in the center of the first-step mine room and the second-step mine room, and the stability of the vein-penetrating tunnel is maintained by leaving peach-shaped mine pillars.

[0005] Although the optimized bottom structure of the mine avoids tunneling inside the filling body, the ore-collecting tunnel is arranged in the center of the mine room, resulting in a low height of the peach-shaped pillar. There is a lack of basis for determining the size of the peach-shaped pillar on site. Under the impact of the ore above, the stability and integrity of the peach-shaped pillar structure are difficult to guarantee. Therefore, it is urgent to study the structural parameters, layout form and stability of the peach-shaped pillar under impact load, so as to increase the ore output while ensuring production safety. Summary of the invention

[0006] The invention discloses a method for optimizing the bottom structure of an abnormal area of ​​a stope, so as to solve the defects of the prior art mentioned in the background technology.

[0007] To achieve the above object, the present invention provides the following technical solution: a method for optimizing the bottom structure of an abnormal stope area, comprising the following steps:

[0008] (1) Calculate the breaking angle and height of the peach-shaped pillar;

[0009] (2) Support design of mine exit tunnels and access roads: adopt the combined support method of anchor rods, metal mesh and shotcrete;

[0010] (3) Support design method: The engineering analogy method is used to calculate the support pressure, anchor length, anchor spacing, anchor diameter, tray size, anchor agent selection, metal mesh and double reinforcement parameter selection, shotcrete parameter selection, and grouting anchor cable parameter selection.

[0011] Preferably, the peach-shaped pillar has a slope angle of 60° and a total height of 18m.

[0012] Preferably, the bottom structure is designed in a sprayed anchor net combined support form based on resin anchor rods.

[0013] Preferably, the anchor rod body is made of threaded steel with a diameter of 24 mm, the rod body is 2.4 m long, the tail thread length is 90 mm, the tray size is 140 mm×140 mm×8 mm, the resin anchor agent roll has a diameter of 28 mm and a length of 700 mm.

[0014] Preferably, the metal mesh is welded with Φ6mm steel bars, the mesh size is 50×50mm, and the mesh shape is diamond.

[0015] Preferably, the double reinforcement bar is formed by welding two parallel Φ8mm steel bars, with a size of 50mm×2400mm including the overlapped part, and a spraying thickness of 50mm.

[0016] Preferably, grouting anchor support is added to the top plate, with an anchor length of 6.0m and an anchor mesh of 1.5m×1.5m.

[0017] The beneficial effects of adopting the above technical solution are:

[0018] In this application, the mining collection tunnel is arranged on one side of the mine room, and the mining exit tunnel is arranged at the junction of the first-step and second-step mine rooms, which can reduce the mining workload and increase the height of the peach-shaped pillar, thereby effectively protecting the stability of the mining exit tunnel and the mining access road. Since the two mine rooms share one peach-shaped pillar, the ore loss caused by the increase in the height of the pillar can be reduced to a certain extent. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is a schematic diagram of the optimized peach-shaped pillar arrangement in the present invention. DETAILED DESCRIPTION

[0020] Embodiments of the present invention are described in detail below:

[0021] The embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0022] A method for optimizing the bottom structure of an abnormal stope area comprises the following steps:

[0023] (1) Peach-shaped pillar parameter setting: In actual production, when a peach-shaped pillar with a bottom ore-discharging structure is formed, a large amount of ore will fall from the top of the peach-shaped pillar. Under the impact of the ore above, the stability and integrity of the peach-shaped pillar structure will directly affect the safety and economic benefits of mining production. Therefore, the stability of the peach-shaped pillar under impact load is studied in order to increase the ore output while ensuring production safety. The masses of the collapsed ore and the peach-shaped pillar are m1 and m2, respectively, the radii are R1 and R2, the elastic moduli are E1 and E2, the Poisson's ratios are μ1 and μ2, the corresponding velocity of the ore before the collision is v1, and the normal velocity of the ore after the collision is v2. The collision process can be divided into two stages: from the beginning of contact to the relative velocity being reduced to 0 m / s, this process is called the compression stage; then the two objects begin to recover the deformation until the two objects separate, this process is called the recovery stage. According to Hertz theory, when two objects collide, the time required for the compression stage t1 and the time required for the recovery stage t2 are:

[0024]

[0025] Where: T is the total contact time of the collision process; n is the contact stiffness coefficient u is the mass exchange coefficient, K1 and K2 are parameters related to the steel ball material. er is the collision recovery coefficient, er=v2 / v1.

[0026] The collision restitution coefficient is widely used. At present, there is no unified definition of the collision restitution coefficient. Most of them are obtained through field tests or based on experience. This paper uses the normal restitution coefficient calculation formula based on quasi-static contact mechanics theory to solve the impact force:

[0027]

[0028] Where: σd is the yield stress of the buffer rock mass; ρ is the density of falling rocks.

[0029] Related research shows that during rockfall, the curve of impact force changing with time can be approximately expressed as a sine or cosine function. The maximum impact force Pmax is calculated as

[0030]

[0031] According to the rock crushing situation on site after blasting, a cubic ore with a side length of 0.5m is selected as the impact ore body. Combining equations (1) to (5), the maximum impact force Pmax generated by the collapse ore body hitting the peach-shaped ore is calculated.

[0032] After blasting, the ore will impact on the surface of the peach-shaped pillar. By decomposing the force on the slope of the peach-shaped pillar, the force perpendicular to the slope can be obtained. According to this model, the force analysis of the peach-shaped pillar is carried out, and the rectangular cross-section unit is selected. The material mechanics calculation formula is used to calculate the force of the pillar:

[0033]

[0034] In the formula: σ is the compressive stress at the boundary point of the pillar section; Mmax is the maximum bending moment of the section; Iz is the moment of inertia of the pillar section; b is the width of the rectangular section, b=1m.

[0035] Using equations (6) and (7), taking σ as the ultimate tensile strength of the pillar, the minimum thickness of the tunnel protective layer can be obtained. The calculation shows that the peach-shaped pillar with a slope angle of 60° and a total height of 18m is the best design solution, and the greater the slope of the peach-shaped pillar, the better the stability of the tunnel and the less affected by the impact of the ore.

[0036] (2) Support design method: using engineering analogy method

[0037] Support pressure:

[0038] Since the mine tunnels and mine access roads are mainly arranged inside the ore body, and the lithology is mainly magnetite quartzite, the roof support pressure of the mine tunnels and mine access roads can be calculated.

[0039]

[0040] Anchor length

[0041] The calculation formula for estimating the length of rock bolts is based on the excavation support ratio ESR. The excavation support ratio (ESR) reflects the support demand and safety of the excavation space. Barton et al. gave an ESR range of 0.8 to 5. This study took 2. The length of the bolt Lb is determined by the roof width (B) or wall height (H) of the tunnel. The formula is as follows:

[0042] Lb=2+(0.15B or H / ESR)(5.16)

[0043] Where: Lb—anchor length, m; B—shaft span, m;

[0044] H—excavation height, m; ESR—excavation support ratio.

[0045] Length of roof anchor bolts in mine exit tunnel and mine access road: Length of anchor bolts on both sides of the mine tunnel and the mine access road: Taking into account the calculation results of the two formulas and the actual situation on site, the anchor rod length is taken as 2.4m.

[0046] Anchor spacing

[0047] The spacing between anchors should not be greater than half of the length of the anchors. Considering the service life of the mine tunnel and the mine access road, the spacing between anchors is determined to be 1.0m. When encountering faults or broken zones, the support parameters should be appropriately reduced according to the surrounding rock conditions.

[0048] Anchor diameter

[0049] According to the stability of the tunnel surrounding rock, which is moderately stable to extremely unstable, the anchor diameter is 18, 20, 22, and 24. Considering the relationship between the diameter of the unreinforced left-handed threaded steel anchor and the yield load and breaking load, the diameter is selected as 24mm based on engineering practice experience.

[0050] tray

[0051] Anchor tray material: Made of 8mm thick steel plate; tray specifications: length × width × thickness = 140 × 140 × 8mm.

[0052] Anchoring agent

[0053] The anchoring force of the anchor rod is determined according to national standards and specifications. The anchoring agent for anchor support uses two types of resin rolls: fast and medium-speed (fast roll solidifies in about 40 to 60 seconds, medium-speed roll solidifies in about 90 to 120 seconds), the diameter of the roll is 28mm, and the length is 700mm, so as to ensure that the anchoring length after the anchor rod is installed is not less than 1000mm.

[0054] Metal mesh and double ribs

[0055] The purpose of configuring metal mesh and double reinforcement bars in shotcrete is to increase the bending and shear strength of the sprayed layer and improve the bearing capacity between anchor rods. The metal mesh adopts Φ6mm diamond galvanized metal mesh, and the mesh size of the diamond galvanized metal mesh is 50mm×50mm; the double reinforcement bar is welded from two parallel Φ8mm steel bars, and its size is 50mm×2400mm (including the overlap part).

[0056] Shotcrete

[0057] Sprayed concrete 50mm thick.

[0058] Grouting anchor cable

[0059] Considering the service life and importance of the mine tunnels and access roads, it is necessary to add grouting anchor support to the roof. The anchor length is 6.0m and the anchor mesh is 1.5m×1.5m.

[0060] The design arranges the mining tunnel on one side of the mine room, and the mining tunnel at the junction of the first-step and second-step mine rooms. This can reduce the mining workload and increase the height of the peach-shaped pillar, thereby effectively protecting the stability of the mining tunnel and the mining access road. Since the two mine rooms share one peach-shaped pillar, the ore loss caused by the increase in the pillar height can be reduced to a certain extent.

[0061] Calculations show that the best design is a peach-shaped pillar with a slope angle of 60° and a total height of 18m. The greater the slope of the peach-shaped pillar, the better the stability of the tunnel and the less affected by the impact of ore.

[0062] The bottom structure is designed with a sprayed anchor net combined support form based on resin anchors. The spacing between anchors is 1m. When encountering faults or broken zones, the support parameters should be appropriately reduced according to the surrounding rock conditions. The anchor rod body is made of 24mm diameter threaded steel, the rod body is 2.4m long, the tail thread length is 90mm, the tray size is 140mm×140mm×8mm, the resin anchor drug roll diameter is 28mm, and the length is 700mm. The metal mesh is welded with Φ6mm steel bars, the grid size is 50×50mm, and the grid shape is diamond. The double reinforcement is welded with two parallel Φ8mm steel bars, the size is 50mm×2400mm (including the overlap part), and the thickness of the spraying is 50mm. Considering the service life and importance of the mine roadway and the mine access road, it is necessary to add grouting anchor cable support to the roof, the anchor cable length is 6.0m, and the anchor cable mesh is 1.5m×1.5m.

[0063] The above is only a preferred embodiment of the present invention. It should be pointed out that a person skilled in the art can make several modifications and improvements without departing from the inventive concept of the present invention, which all fall within the protection scope of the present invention.

Claims

1. A method for optimizing the bottom structure of an abnormal stope area, characterized in that: The following steps are included (1) Calculate the breaking angle and height of the peach-shaped pillar; (2) Support design of mine exit tunnels and access roads: adopt the combined support method of anchor rods, metal mesh and shotcrete; (3) Support design method: calculation of support pressure, anchor length, anchor spacing, anchor diameter, tray size, anchor selection, metal mesh and double reinforcement parameter selection, shotcrete parameter selection, and grouting anchor cable parameter selection.

2. A method for optimizing the bottom structure of an abnormal stope according to claim 1, characterized in that: The slope angle of the peach-shaped pillar is 60° and the total height is 18m.

3. The method for optimizing the bottom structure of an abnormal stope area according to claim 2, characterized in that: The bottom structure design is a sprayed anchor mesh combined support form based on resin anchor rods.

4. A method for optimizing the bottom structure of an abnormal stope area according to claim 3, characterized in that: The anchor rod body is made of 24mm diameter threaded steel, the rod body is 2.4m long, the tail thread length is 90mm, the tray size is 140mm×140mm×8mm, the resin anchor agent roll has a diameter of 28mm and a length of 700mm.

5. A method for optimizing the bottom structure of an abnormal stope area according to claim 4, characterized in that: The metal mesh is welded with Φ6mm steel bars, the mesh size is 50×50mm, and the mesh shape is diamond.

6. A method for optimizing the bottom structure of an abnormal stope area according to claim 5, characterized in that: The double reinforcement is welded from two parallel Φ8mm steel bars, with a size of 50mm×2400mm including the overlapped part, and a shotcrete thickness of 50mm.

7. A method for optimizing the bottom structure of an abnormal stope area according to claim 6, characterized in that: Add grouting anchor support to the top plate, the anchor length is 6.0m, and the anchor mesh is 1.5m×1.5m.

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