Novel coal mining method for open-air well-to-well worker

Abstract

The invention provides a novel coal mining method for an open-air well-to-well worker. The novel coal mining method comprises the following steps: stoping by a slope coal mining machine; filling a mining cave, determining a filling process, selecting one of pumping filling, waste rock throwing machine filling or side upper part drill hole conveying filling in the filling process, and selecting filling materials according to a ratio of waste rock to concrete; carrying out slope stability calculation and analysis and slope monitoring, and carrying out mechanical analysis and calculation by adopting a limit equilibrium method and a finite element method. The invention provides a mining process system and complete equipment, including automation of coal mining and transportation, realization of automatic operation and connection of coal, mining and transportation equipment, improvement of coal mining efficiency and efficiency of a filling system, and realization of key technologies and processes of efficient paste filling, and provides an overlying strata stability monitoring control technology and equipment. The intelligent mining site is realized, the scientific and reasonable cooperation of mining, filling and slope stability monitoring is realized, and the connection is orderly and efficient.

Description

Technical Field

[0001] The invention relates to the technical field of coal mining, in particular to a new type of coal mining method for open-pit to underground workers. Background Art

[0002] Sidewall coal is referred to as sidewall coal. It refers to the unmined part of the open-pit coal mine that is covered by the mining process during the production process. It is the result of the traditional open-pit stripping mining process and is a sporadic resource left over from production. A large number of sporadic resources have been buried for a long time, which not only causes huge waste, but also poses safety hazards such as landslides and spontaneous combustion. The sidewall coal mining process appeared earlier in foreign countries. Due to the limitations of technical equipment, the process has a small production capacity, low efficiency, and the actual application effect is not ideal. Later, a combined coal mining machine for mining open-pit sidewalls and outcropping coal was developed, and the current production process is mature.

[0003] There is a large amount of coal compression in the Ordos area of ​​Inner Mongolia. The coal compression in the deep part of the open-pit mine and the sidewall of the mining site can be removed by the sidewall coal mining machine, and the coal resources that are not suitable for open-pit mining can be mined by the sidewall coal mining machine, so as to recover the resources. The present invention provides a new coal mining method for open-pit to underground workers. Summary of the invention

[0004] The invention aims to provide a novel coal mining method for open-pit workers.

[0005] To achieve the above object, the present invention proposes the following technical solution: a new open-pit coal mining method, comprising the following process:

[0006] Process S1, side coal mining machine recovery, process S1 includes: process S1.1, determined mining technology and transportation method, before the side coal recovery begins, the slope stability analysis and verification of the recovery section should be carried out in combination with the current situation of open-pit mining, and the side coal recovery operation can be carried out only when it is in a stable state, and the recovery parameters should be determined;

[0007] Process S1.2, calculate the failure movement form of the coal seam roof, obtain the value of the mining width L and the maximum overhang span L0 of the roof rock layer, calculate the bending and tensile failure process and mechanical conditions of the rock layer, obtain the stress state of the embedded beam and the simply supported beam to obtain the bending and tensile mechanical conditions, and predict the mechanical process and conditions of the overhanging rock layer from bending to failure;

[0008] Process S1.3, determination of mining parameters and coal pillar width;

[0009] Process S2, mining tunnel filling, process S2 includes, process S2.1, determining the filling process, the filling process is selected from one of pumping filling, dumping machine filling or side wall upper drilling and conveying filling;

[0010] Process S2.2, filling material selection, based on the coal mine filling rate, the filling material ratio is gangue: concrete, and the filling ratio is about 8:2;

[0011] Process S3, slope stability calculation and analysis and slope monitoring, wherein the slope stability calculation and analysis includes determining the composition of the slope strata and using the limit equilibrium method and finite element method for mechanical analysis and calculation;

[0012] Slope monitoring includes the establishment of a monitoring network and the selection of monitoring equipment. The layout of the monitoring network is determined according to the terrain conditions of the observation area. The layout of the monitoring network is selected from one of the square grid, arbitrary square grid, cross grid, ray grid and baseline intersection grid. The monitoring equipment includes surface deformation monitoring equipment, slope stress monitoring equipment and groundwater monitoring equipment.

[0013] Furthermore, in the present invention, process S1.1 also includes that the side coal mining machine is placed on the bottom plate of the corresponding recovered coal seam, the coal seam will be mined by the side coal mining machine, and the coal will be transported by the belt conveyor. The unloading point will be mined by the front loader, and the coal will be loaded by the front loader into the dump truck from the coal yard, and the dump truck will be transported to the surface coal storage yard of the open-pit mine;

[0014] When there are multiple coal seams within the mining range of the side coal mining machine, the recovery of the covered coal seams shall be carried out in a bottom-up order according to the production progress of the open-pit mine and the demand for internal backfilling. That is, while ensuring the safe production of the open-pit mine, the recovery of the side coal is gradually carried out. After the recovery of the lower coal seam, the internal backfilling is immediately carried out. When the backfilling reaches the elevation of the bottom plate of the upper coal seam, the upper layer of coal is recovered. In this way, the side coal covering of each coal seam is gradually recovered.

[0015] When tracking the inner discharge in the direction of advancement of the open-pit mine, when the upper and lower coal seams are both capable of recovery, the design determines that a side-wall coal mining machine will be used to recover the lower coal seam first according to the number of selected equipment models and the recoverable length of the exposed side wall. After the recoverable mining tunnels of the lower coal seam are mined, the upper coal seam that meets the operating conditions will be recovered; that is, only one side-wall coal mining machine is allowed to operate in the same time period, so that the inner discharge can be followed up after the lower coal seam is recovered, and the recovery space of the upper coal seam is expanded;

[0016] It is designed to divide 10 mining chambers into one group along the direction of advancement of the open-pit mine, with one supporting coal pillar left between every two mining chambers and one isolating coal pillar left between every ten mining chambers. The mining chambers in each group are numbered 1#, 2#...10# in sequence, and the mining chambers numbered 1#, 2#...10# are mined in sequence during side-wall coal mining. It is designed that after the mining chambers are recovered, the mined mining chambers will be filled as soon as possible. Before the mining of the second group of mining chambers is started, the filling of the first group of mining chambers must begin, and before the mining of the third group of mining chambers is completed, the filling of the first group of mining chambers must be completed. During the mining-filling process, it is necessary to ensure that there is at least one coal pillar as a supporting coal pillar between the excavation mining chamber and the filling mining chamber.

[0017] Furthermore, in the present invention, the process S1.2 also includes that, under the action of the overlying uniformly distributed load and its own deadweight, the cracking condition of point O in the middle of the rock beam is that its bending moment reaches a value that causes the tensile stress to exceed the limit, that is:

[0018]

[0019] Where: o —Actual tensile stress at point O;

[0020] M0—bending moment at point O;

[0021] W—section modulus of rock beam;

[0022] For the embedded beam, the bending moments at the ends and the middle are

[0023]

[0024] For a simply supported beam, the bending moments at the ends and the middle are

[0025] M A =0;

[0026]

[0027] From the above formula, it can be seen that the sum of the bending moments at the ends and the middle of the embedded beam is equal to the bending moment in the middle of the simply supported beam. After the end of the beam cracks, the bending moment at the end is transferred to the middle. Therefore, as long as the ends of the beam are pulled apart, the support conditions are quickly transformed to simply supported beams, and the pulling apart of the middle part will inevitably lead to bending and tensile failure of the rock beam. The mechanical process and conditions of the development of the overhanging rock layer from bending to failure can be summarized as:

[0028] (1) When the working face advances to the rock beam overhang span limit value L0, the tensile stress at the beam end is

[0029]

[0030] At this time, since the overhanging rock layer is separated from the upper rock layer after bending and sinking, it is not affected by the gravity of the upper rock layer. Therefore, when the upper part of the overhanging rock layer is weaker than the upper rock layer, the rock layer is only affected by its own gravity, and the tensile stress σ at the end of the fracture is A for

[0031]

[0032] When there is a weaker rock layer above the overhanging rock layer, the rock layer is only affected by its own gravity, and the tensile stress σ at the end of the fracture A for

[0033]

[0034] Where: m—the thickness of the lower support layer with high strength, m;

[0035] mi—thickness of the upper weaker rock layer that moves simultaneously with the supporting layer, m,

[0036] (2) During the cracking process of the rock beam end, as the bending moment at the end decreases, the bending moment in the middle gradually increases, and the supporting force transforms to that of a simply supported beam. The numerical development of

[0037] (3) During the transformation from an embedded beam to a simply supported beam, when the tensile stress in the middle of the rock beam achieve

[0038] When the middle part is pulled apart, the rock beam will develop into a collapse or remain a "pseudo-plastic rock beam"

[0039] state,

[0040] (4) The mechanical conditions for cracking at the ends and middle of the rock beam are: At this time, the maximum span of the rock beam L0 is

[0041]

[0042] when That is, when a single rock layer is bent and destroyed, the expression of L0 is:

[0043]

[0044] Obviously, the L0 value varies with the thickness of the rock beam m, and the allowable tensile strength [σ t ] increases with the increase of the soft rock thickness on the supporting layer. decreases with the increase of .

[0045] Furthermore, in the present invention, the process S1.3 also includes:

[0046] 1. Determine the width of the mining tunnel;

[0047] According to the formula The maximum exposed span L0 of the direct roof of the mining tunnel during mining of each coal seam can be obtained, which is the width of the mining tunnel.

[0048] 2. Determine the width of the coal pillar;

[0049] According to the force analysis of the coal pillar, the pressure on the supporting coal pillar is half of the rock pressure above the coal pillar and half of the rock pressure above the mining tunnels on both sides of the coal pillar. The calculation formula for the width of the coal pillar is:

[0050] a=γH(a+L) / P

[0051] P-vertical stress borne by the coal pillar (kN / m2);

[0052] γ-average bulk density of overlying rock (kN / m3);

[0053] H-mining depth (m); the mining depth is determined according to the surface elevation of the borehole near the side coal recovery area and the elevation of the coal seam floor;

[0054] a-Width of coal pillar (m);

[0055] L-Width of mining shaft (m).

[0056] Furthermore, in the present invention, in the process S3, the slope monitoring includes ground rock movement monitoring, establishing rock movement observation points on the ground around the mine, implementing regular observations, and timely grasping the slope dynamics; flat plate rock movement monitoring in the mining area, arranging observation points on the working flat plate of the mine, forming a network distribution together with the ground observation points, regularly observing, grasping the rock movement at any time, and temporary rock movement monitoring of key areas; setting temporary observation points for key areas, observing on a periodic basis, monitoring local deformation, and making deformation or landslide forecasts in a timely manner; setting surface monitoring points on the ground to monitor surface movement and subsidence, and the monitoring period should be no less than half a year,

[0057] Deep displacement monitoring is used to understand the deformation dynamics of deep rock mass. Underground rock mass displacement deformation monitoring holes are established. After the drilling rig forms a hole, a polyethylene pipe with a grooved slideway is installed in the hole. A mobile inclinometer is used for regular monitoring, thereby realizing the observation of the deformation dynamics of deep rock mass and making deformation predictions in a timely manner.

[0058] Manual monitoring is coordinated with ground rock movement monitoring, and professional personnel are arranged to patrol different areas to check the deformation of surface cracks or buildings so as to detect abnormal deformation at any time and take timely countermeasures.

[0059] Furthermore, in the present invention, in the process S3, the slope monitoring also includes a sensor system, a data communication subsystem, a data processing and control system, a lightning protection system, and an early warning system;

[0060] The sensor system includes Beidou monitoring unit, crack collection unit, and groundwater collection unit. The purpose of the unit is to use Beidou technology to reflect the real-time three-dimensional changes of the monitored object;

[0061] The Beidou antenna of the data communication subsystem communicates with the Beidou host via coaxial cable; the Beidou host and other sensors communicate with the control center using wireless communication, crack monitoring uses wireless communication, and the groundwater collection unit uses wireless communication;

[0062] The data processing and control system receives and processes the data collected by the workstation system in real time, and displays the original data and processed data, and performs online evaluation and early warning.

[0063] The lightning protection system is used to protect the safety of equipment. It includes two parts: protection against direct lightning and protection against inductive lightning. Lightning rods are used to protect against direct lightning, and surge protectors are used to protect against inductive lightning.

[0064] When the data calculated by the software unit of the early warning system exceeds a certain current value, or when a sudden change occurs in the monitoring system, the early warning information is displayed in the form of a text message or on the monitoring server.

[0065] Furthermore, in the present invention, in the process S3, slope monitoring also includes a slope monitoring point arrangement method, which is selected at the deformation-sensitive parts of the slope. According to the slope type, the monitoring points are arranged near the trailing edge cracks, the leading edge slope foot, the leading edge ridges and other locking points with obvious stress concentration or controlled sliding. There are no less than 3 monitoring points on each monitoring line, and the spacing between them is 20 to 40 m. 1 to 2 monitoring points are set outside the perimeter of the slope. The monitoring technical methods adopt Beidou monitoring system, radar system, rainfall monitoring, borehole inclinometer and crack displacement meter for monitoring.

[0066] Beneficial effects: The technical solution of this application has the following technical effects:

[0067] The present invention provides a mining process system and a complete set of equipment, including the automation of coal mining and its transportation, realizing the automatic operation and connection of coal and mining and transportation equipment, improving the efficiency of coal mining and the efficiency of the filling system, realizing the key technology and process of efficient filling of paste, and providing the overburden stability monitoring and control technology and equipment to realize the intelligence of the mining site, realize the scientific and reasonable coordination of mining, filling and slope stability monitoring, and the connection is orderly and efficient.

[0068] It should be appreciated that all combinations of the foregoing concepts, as well as additional concepts described in greater detail below, may be considered to be part of the inventive subject matter of the present disclosure, provided such concepts are not mutually inconsistent.

[0069] The foregoing and other aspects, embodiments and features of the present invention can be more fully understood from the following description in conjunction with the accompanying drawings. Other additional aspects of the present invention, such as the features and / or beneficial effects of the exemplary embodiments, will be apparent from the following description or learned from the practice of the specific embodiments according to the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0070] The drawings are not intended to be drawn to scale. In the drawings, each identical or nearly identical component shown in various figures may be represented by the same reference numeral. For clarity, not every component is labeled in every figure. Embodiments of various aspects of the present invention will now be described by way of example and with reference to the accompanying drawings, in which:

[0071] Figure 1 It is a schematic diagram of the process of the novel coal mining method of the present invention.

[0072] Figure 2 It is a schematic diagram of the process of the novel coal mining method of the present invention.

[0073] Figure 3 It is a schematic diagram of the process of the novel coal mining method of the present invention.

[0074] Figure 4 It is a schematic diagram of the process of the novel coal mining method of the present invention.

[0075] Figure 5 It is a schematic diagram of the process of the novel coal mining method of the present invention.

[0076] Figure 6 It is a schematic diagram of the process of the novel coal mining method of the present invention.

[0077] Figure 7 It is a schematic diagram of the process of the novel coal mining method of the present invention.

[0078] Figure 8 It is a schematic diagram of the process of the novel coal mining method of the present invention.

[0079] Fig. 9 It is a schematic diagram of the process of the novel coal mining method of the present invention.

[0080] Fig.10 It is a schematic diagram of the mining sequence of the present invention.

[0081] Fig.11 This is a step operation diagram of the side coal mining machine of the present invention.

[0082] Fig.12 It is a diagram of the advancing work of the sidewall coal mining machine of the present invention.

[0083] Fig.13 This is a working diagram of the side coal mining machine cutting grooves of the present invention.

[0084] Fig.14 This is a bottom pulling working diagram of the side coal mining machine of the present invention.

[0085] Fig.15 This is a top sweeping working diagram of the side coal machine of the present invention.

[0086] Fig.16 It is the supporting condition and bending moment diagram of the rock beam in the embedded state of the present invention.

[0087] Fig.17 It is the supporting condition and bending moment diagram of the rock beam in the simply supported state of the present invention.

[0088] Fig.18 This is the force diagram of the coal pillar of the present invention.

[0089] Fig.19 It is a schematic diagram of the filling process arrangement of the gangue throwing machine of the present invention.

[0090] Fig. 20 This is the slope model diagram of the present invention.

[0091] Fig.21 This is the displacement cloud map of the present invention.

[0092] Fig. 22 This is the stress-strain cloud diagram of the present invention.

[0093] Fig.23 This is the limit equilibrium calculation diagram of the present invention.

[0094] Fig.24 This is the overall framework diagram of the monitoring system of the present invention.

[0095] Fig.25 This is the overall hardware framework diagram of the monitoring system of the present invention. DETAILED DESCRIPTION

[0096] In order to better understand the technical content of the present invention, specific embodiments are cited and described as follows in conjunction with the accompanying drawings. Various aspects of the present invention are described in this disclosure with reference to the accompanying drawings, in which many illustrative embodiments are shown. The embodiments of the present disclosure are not necessarily defined to include all aspects of the present invention. It should be understood that the various concepts and embodiments introduced above, as well as those described in more detail below, can be implemented in any of many ways, because the concepts and embodiments disclosed in the present invention are not limited to any implementation. In addition, some aspects disclosed in the present invention can be used alone, or in any appropriate combination with other aspects disclosed in the present invention.

[0097] This embodiment provides a new type of coal mining method for open-pit to underground workers, such as Figure 1-9 As shown, the process includes the following:

[0098] Process S1, side coal mining, process S1 includes: process S1.1, determined mining technology and transportation method. Before the side coal recovery begins, the slope of the recovery section should be analyzed and verified for stability in combination with the current situation of open-pit mining. Only when it is in a stable state can the side coal recovery operation be implemented and the recovery parameters be determined.

[0099] Specifically, in the design, the equipment stands on the bottom plate of each recovered coal seam, and its working platform width needs to be at least 80m, and the side safety platform is generally reserved for 20m.

[0100] The side coal mining machine is placed on the bottom plate of the corresponding recovered coal seam. At the end of the coal seam below 6m, no separate coal step is left, and steps are formed together with the upper rock. The side safety platform is not less than 5m, and the width of the cleaning platform is not less than 15m; for the coal seam above 6m and the step formed by the upper rock, the height is not more than 15m, and at the same time, the design slope angle or slope stability requirements are met. According to the determined mining process and transportation method, the coal seam will be mined by the side coal mining machine, transported by belt conveyor, and loaded by front loader at the unloading point. The front loader loads the raw coal from the coal yard into dump trucks, which are then transported to the surface coal storage yard of the open-pit mine.

[0101] When there are multiple coal seams within the mining range of the side coal mining machine, the recovery of the covered coal seams is generally carried out in a bottom-up order according to the production progress of the open-pit mine and the demand for internal backfilling. That is, while ensuring the safe production of the open-pit mine, the recovery of the covered coal on the side walls is carried out step by step. After the recovery of the lower coal seam, the internal backfilling is carried out immediately. When the backfill reaches the bottom plate elevation of the previous coal seam, the upper layer of coal is recovered. This process is repeated and the amount of covered coal on the side walls of each coal seam is gradually recovered.

[0102] When tracking the inner drainage in the direction of advancement of the open-pit mine, when the upper and lower coal seams meet the conditions for recovery at the same time, although the mining chambers of the upper and lower coal seams are staggered due to the inner dumping platform, according to the number of selected equipment models and the recoverable length of the exposed side walls, the design determines that one side wall coal mining machine will be used to recover the lower coal seam first, and after the recoverable mining chambers of the lower coal seam are mined, the upper coal seam that meets the operating conditions will be recovered; that is, only one side wall coal mining machine is allowed to operate in the same time period, so that after the lower coal seam is recovered, the inner drainage can be followed up, and the recovery space of the upper coal seam is expanded. This is also convenient for personnel management and equipment maintenance, and reduces the impact of side wall mining on the stripping working face and the inner dumping field working face.

[0103] At the same time, the recovery of side coal is carried out under the condition that the slope where the recovery section is located is in a stable state. Therefore, before the recovery of side coal begins, the stability analysis and verification of the slope of the recovery section should be carried out in combination with the current situation of open-pit mining. The side coal recovery operation can only be implemented when it is in a stable state. During the recovery process, the management and monitoring of the side slopes should also be strengthened.

[0104] Therefore, the design determines that the recovery order of each coal seam on the side of Manlailiang Coal Mine is from bottom to top, and only one side coal mining machine can operate in the same time period.

[0105] The design divides the open pit into 1 group of 10 mining holes along the direction of advancement, with a supporting coal pillar between every 2 mining holes and an isolation coal pillar between every 10 mining holes. The mining holes in each group are numbered 1#, 2#...10# in sequence, and the mining holes numbered 1#, 2#...10# are mined in sequence during sidewall coal mining.

[0106] After the mining tunnels are recovered, the mined tunnels should be filled as soon as possible. Before the second group of mining tunnels are mined, the first group of mining tunnels must start filling. Before the third group of mining tunnels are mined, the first group of mining tunnels must be filled. Warning signs should be set up to prevent coal seam spontaneous combustion and slope collapse from causing casualties. Fig.10 During the mining-filling process, it is necessary to ensure that there is at least one coal pillar as a supporting coal pillar between the excavation mining tunnel and the filling mining tunnel.

[0107] In the process of recovering resources from the sidewall, the equipment needs to ensure that the minimum width of the mining working step is 80m. If the width is larger, it will be more ideal. In the production area, the width of the flat plate can be widened by partially raising it to meet the needs of the sidewall coal mining machine. In the unmined area, the sidewall coal mining machine working flat plate can be reserved and completely removed after the upper coal seam is mined. For details, see the sidewall coal mining machine step operation Fig.11 , side coal mining machine advancement work Fig.12 , side coal mining machine slotting work Fig.13 , side coal mining machine bottom pulling work Fig.14 , side coal machine top sweeping work Fig.15 .

[0108] Process S1.2 calculates the failure movement form of the coal seam roof, obtains the values ​​of the mining width L and the maximum overhang span L0 of the roof rock layer, calculates the bending and tensile failure process and mechanical conditions of the rock layer, obtains the stress state of the embedded beam and the simply supported beam to obtain the mechanical conditions of bending and tension, and predicts the mechanical process and conditions of the overhanging rock layer from bending to failure.

[0109] Specifically, when the roof rock layer is not supported, the maximum overhang span L0 of the roof rock layer determines the width L of each side-wall coal mining tunnel. Based on the theory of mine rock mechanics, the bending and pulling failure movement form and the shear (cutting) failure movement form of the coal seam roof are analyzed. Combined with the actual situation of side-wall coal mining, the failure movement form of the side-wall coal mining tunnel roof is designed to be bending and pulling failure movement. Therefore, the failure process and mechanical conditions of the bending and pulling failure movement form are used to simulate the mining tunnel roof, and the relationship between the mining tunnel width L and the maximum overhang span L0 of the roof rock layer is analyzed.

[0110] The mechanical process of rock stratum bending and tensile failure is the process of development from embedded beam to simply supported beam under its constraint conditions. Because the inclined length of the working face is usually much larger than the ultimate span of the overhanging rock stratum under normal circumstances, the overhanging rock stratum can be simplified into a beam with two ends embedded, one end supported by the coal body of the working face and the other end supported by the boundary coal pillar, such as Figure 16-17 As shown in the figure. The weight of the overlying rock strata can be transferred to the supporting points at both ends (coal bodies in front and behind the working face) through the beam. Therefore, the mechanical conditions of bending and tension can be obtained by analyzing the stress state of the above two types of beams.

[0111] Under the action of the overlying uniformly distributed load and its own deadweight, the cracking condition of point O in the middle of the rock beam is that its bending moment reaches the value that makes the tensile stress exceed the limit, that is:

[0112]

[0113] Where: o —Actual tensile stress at point O;

[0114] M0—bending moment at point O;

[0115] W—section modulus of rock beam;

[0116] For the embedded beam, the bending moments at the ends and the middle are

[0117]

[0118] For a simply supported beam, the bending moments at the ends and the middle are

[0119] M A =0;

[0120]

[0121] From the above formula, we can know that the sum of the bending moments at the ends and the middle of the embedded beam is equal to the bending moment in the middle of the simply supported beam. After the end of the beam cracks, the bending moment at the end is transferred to the middle. Therefore, as long as the ends of the beam are pulled apart, the support conditions will quickly transform to a simply supported beam, and the pulling apart of the middle will inevitably lead to bending and tensile failure of the rock beam. The mechanical process and conditions of the development of the overhanging rock layer from bending to failure can be summarized as:

[0122] (1) When the working face advances to the rock beam overhang span limit value L0, the tensile stress at the beam end is

[0123]

[0124] At this time, since the overhanging rock layer is separated from the upper rock layer after bending and sinking, it is not affected by the gravity of the upper rock layer. Therefore, when the upper part of the overhanging rock layer is weaker than the upper rock layer, the rock layer is only affected by its own gravity, and the tensile stress σ at the end of the fracture is A for

[0125]

[0126] When there is a weaker rock layer above the overhanging rock layer, the rock layer is only affected by its own gravity, and the tensile stress σ at the end of the fracture A for

[0127]

[0128] Where: m—the thickness of the lower support layer with high strength, m;

[0129] m i —Thickness of the upper weaker rock layer that moves simultaneously with the supporting layer, m.

[0130] (2) During the cracking process of the rock beam end, as the bending moment at the end decreases, the bending moment in the middle gradually increases, and the supporting force transforms to that of a simply supported beam. numerical development.

[0131] (3) During the transformation from an embedded beam to a simply supported beam, when the tensile stress in the middle of the rock beam achieve

[0132] When the middle part is pulled apart, the rock beam will develop into a collapse or remain a "pseudo-plastic rock beam"

[0133] state.

[0134] (4) The mechanical conditions for cracking at the ends and middle of the rock beam are: At this time, the maximum span of rock beam exposure L0 is

[0135]

[0136] when That is, when a single rock layer is bent and destroyed, the expression of L0 is:

[0137]

[0138] Obviously, the L0 value varies with the thickness of the rock beam m, and the allowable tensile strength [σ t ] increases with the increase of the soft rock thickness on the supporting layer. decreases with the increase of .

[0139] Process S1.3, determination of mining parameters and coal pillar width;

[0140] Specifically, (1) the width of the mining tunnel is determined.

[0141] Taking a certain mine field as an example, according to the geological report, the coal seam in the mine field is mainly composed of sandy mudstone, the minimum rock layer thickness m is 5.0m, and the tensile strength [σ t ] is 4.34MPa, and the bulk density γ is 2300N / m 3The second direct roof of the coal seam is mainly composed of fine-grained sandstone, the rock layer thickness m is the minimum 4.5m, and the tensile strength [σ t ] is 5.25MPa, and the bulk density γ is 2650N / m 3 .

[0142] According to the formula The maximum exposed span L0 of the direct roof of the mining tunnel during mining of each coal seam can be obtained:

[0143] Coal seam 1:

[0144] That is: L3≤4.34;

[0145] Coal seam 2:

[0146] That is: L4≤4.22;

[0147] According to the above calculations, the maximum span L3 of the direct roof of the first coal seam is less than or equal to 4.34m; the maximum span L4 of the direct roof of the second coal seam is less than or equal to 4.22m.

[0148] According to the experience of side coal mining in other coal mines, if the design uses the EML340-26 / 45 side coal mining machine, the maximum width of the equipment is 3.3m. Therefore, the design determines that the width of the side coal recovery mining tunnel for coal seam one and coal seam two is 3.3m.

[0149] (2) Coal pillar width

[0150] After the mining, the mining-coal pillar distribution pattern is formed. At this time, the coal pillar is under the greatest stress. According to the shallow ground pressure theory, assuming that the supporting coal pillar bears all the rock stress above the coal seam, the stress of the coal pillar is as follows: Fig.18 .

[0151] According to the force analysis of the coal pillar, the pressure on the supporting coal pillar is half of the rock pressure above the coal pillar and half of the rock pressure above the mining tunnels on both sides of the coal pillar. Therefore, the calculation formula for the vertical stress on the coal pillar is:

[0152] P = γH(a+L) / a;

[0153] P-vertical stress of coal pillar, kN / m 2 ;

[0154] γ-average bulk density of overlying rock, kN / m 3 According to a geological report of a mine field, 2.4t / m 3 =24kN / m 3 .

[0155] H-mining depth, m; the mining depth is determined by the surface elevation of the borehole near the side coal recovery area and the elevation of the coal seam floor. Due to different recovery areas, the mining depth is different. According to the geological report, the maximum burial depth of coal seam 1 is 65m, and the maximum burial depth of coal seam 2 is 100m.

[0156] a-coal pillar width, m;

[0157] L-Width of mining tunnel, m. Based on the experience of surrounding coal mines, the EML340-26 / 45 sidewall coal mining machine is designed for coal seams 1 and 2, and the width of the mining tunnel is determined to be 3.3 m.

[0158] According to geological report data, the compressive strength of coal seams P S 10.6MPa, converted to stress, 10.6MPa = 10600kN / m 2 .

[0159] Assuming that after the mining of the two sides of the coal pillar is completed, the coal pillar is in a limit equilibrium state, then P = P S , then the width of the coal pillar is:

[0160] a Ⅲ-2煤 =γHL / (P S -γH)

[0161] =24×65×3.3 / (10600-24×65)=0.57m;

[0162] a Ⅳ-2煤 =γHL / (P S -γH)

[0163] =24×100×3.3 / (10600-24×100)=0.97m;

[0164] According to the above formula, when the coal pillar is in the limit equilibrium state, when the width of the coal seam 1 mining shaft is 3.3m, the width of the coal pillar is 0.57m; when the width of the coal seam 2 mining shaft is 3.3m, the width of the coal pillar is 0.97m.

[0165] In order to ensure the safety of side coal mining, the safety factor K should be considered in the design of coal pillars. The value of K is 1.3 to 1.5 according to the development degree of coal seam joints and fissures.

[0166] Therefore, a Ⅲ-2煤 =0.57×1.5=0.86m;

[0167] a Ⅳ-2煤 =0.97×1.5=1.46m;

[0168] In summary, the width of the mining shafts in Coal Seam 1 and Coal Seam 2 designed this time is 3.3m, and the width of the coal pillars is determined to be 2.2m; an isolation coal pillar is set every 10 mining shafts, and its width is determined to be 5.0m based on 2 to 3 times the width of the supporting coal pillar.

[0169] Process S2, mining tunnel filling, process S2 includes, process S2.1, determining the filling process, the filling process is to select one of pumping filling, dumping machine filling or side wall upper drilling and conveying filling;

[0170] The specific processes of the three solutions are as follows:

[0171] (1) Pumping filling solution

[0172] This plan combines the backfilling plan within the mining pit and arranges a mobile filling station at a suitable location within the mining pit. The filling station consists of a gangue crushing station, a belt conveyor, a raw material warehouse, a mobile mixing station, a filling pump, etc.

[0173] After the gangue is crushed (particle size is less than 20mm), it is lifted to the mixing tank by an elevator. The cement and water in the raw material bin are transported to the mixing tank through the pipeline at the bottom of the bin. The filling body formed after mixing with the crushed gangue is transported to the mining shaft through the pipeline by a filling pump for filling.

[0174] At the same time, in order to shorten the solidification time of the filling body, improve the early strength of the filling body and the top connection rate, a certain proportion of quick-setting agent and chemical expansion agent is added when the filling body is filled into the mining tunnel. The quick-setting agent and chemical expansion agent are transported to the mining tunnel through a dedicated pipeline through a self-propelled pipeline filling vehicle, and mixed with the filling body conveying pipeline at the discharge port before being filled into the mining tunnel. After filling, the pipeline is flushed with clean water and an air compressor to prevent pipe blockage.

[0175] In order to ensure the top connection rate and compaction rate of the filling body, a retractable steel slurry baffle is installed at the front of the self-propelled pipeline filling vehicle. Holes with the same diameter as the filling body conveying pipeline and the admixture conveying pipeline are reserved in the middle and upper part of the slurry baffle, which is convenient for the later installation of the filling pipeline into the mining tunnel for filling. Seamless steel pipes are installed on the filling holes reserved on the slurry baffle.

[0176] After the mining is completed, the mining equipment withdraws from the mining tunnel. Each filling pipeline enters the mining tunnel through the self-moving pipeline filling vehicle for backward filling. In order to facilitate the withdrawal of the filling pipeline from the filling body at a later stage, the filling pipelines in front of the slurry retaining plate are made of seamless steel pipes, and they enter the front filling area 2.5m through the filling hole reserved on the slurry retaining plate; in order to facilitate the withdrawal of the filling pipeline from the mining tunnel, the filling pipelines behind the slurry retaining plate are made of seamless steel pipes.

[0177] The paste delivery pipeline from the filling station to the area in the mining pit adopts seamless steel pipes; the filling pipelines in the mining tunnel adopt seamless steel pipes. In order to facilitate the withdrawal from the mining tunnel in the later stage, the seamless steel pipes are connected by flanges every 10m; the filling pipeline for conveying filling aggregates has a diameter of Ф159×4.5mm. As the mining tunnel is filled from the inside to the outside, the filling pipeline withdraws from the mining tunnel with the self-moving pipeline filling vehicle, and is dismantled every 10m outside the mining tunnel.

[0178] It is designed that filling is carried out every 5m in the mining tunnel. When the paste within 5m is full, the filling pipeline will retreat with the self-propelled pipeline filling vehicle and continue filling until the mining tunnel is completely filled.

[0179] Since the mine is a blind alley, personnel are prohibited from entering. The filling equipment is manually controlled outside the mine. During filling, a visual system is installed inside the mine to monitor the filling situation in real time. The relevant monitoring lines are laid along the self-moving pipeline filling vehicle that lays the filling pipeline.

[0180] (2) Filling of the waste dumper

[0181] This method uses a rock dumper to fill the mine. In order to ensure the strength and top connection rate of the filling body, the remaining space after rock dumping is filled with concrete slurry.

[0182] The filling system consists of a gangue crushing station, a belt conveyor, a mining concrete pump, a feeder, a gangue thrower, etc. The specific process flow is as follows:

[0183] After the mining is completed, the gangue stripped from the open-pit mine is used as filling material. The gangue is transported to the crushing station outside the mining tunnel by truck. After the gangue is crushed and sorted by the screening feeder, the gangue of appropriate size (particle size less than 150mm) is transported by truck to the temporary gangue storage site on the ground near the mining tunnel. The gangue is then transported to the gangue buffer bin above the belt conveyor by a forklift, and the gangue is transported to the mining tunnel by the belt, and then thrown by the gangue thrower for filling.

[0184] Concrete slurry is used in the existing concrete mixing station of the mine. The concrete slurry is transported to the outside of the mining tunnel by a mixer truck and transported to the mining tunnel through a pipeline by a mining concrete delivery pump for spraying and filling. The filling concrete slurry pipeline is laid along the gangue conveyor belt and the drying machine to enter the mining tunnel for backward spraying and filling. The concrete strength should reach at least C15.

[0185] The specific process is to use a gangue thrower to carry out gangue filling and observe it using a visual system. After the gangue is filled to a certain extent, the gangue throwing is stopped and spraying is carried out to ensure the strength of the filling body and the top connection rate. After the spraying is completed, retreat and continue the above process. The specific retreat step distance can be determined according to the specific parameters of the gangue thrower.

[0186] Each filling pipeline in the mining tunnel uses a flexible hose with a diameter of DN108. In order to facilitate the withdrawal from the mining tunnel in the later stage, the flexible hose is connected with flanges every 20m. As the mining tunnel is filled from the inside to the outside, the filling pipeline exits the mining tunnel with the gangue conveyor belt and is dismantled every 20m outside the mining tunnel.

[0187] In order to ensure the filling rate, the design uses the back step of the gangue thrower (1000mm) to measure the filling material, that is, according to the volume of the mining tunnel, the gangue thrower fills the mining tunnel length of 3m, and then the grouting is carried out. The measurement of the gangue can be controlled by the number of loader buckets. For example, the cross-sectional area of ​​the 6-2 coal mining tunnel is designed to be 14.59m 2 , then the volume of a 1m long tunnel is 14.59m 3 , one bucket of loader is about 3m 3 The initial design requirement for this time is that the filling rate of the mining tunnel after filling should not be less than 90%, that is, using the dumping machine to fill 43m 3 (When the length is 3m) filling material, about 14 buckets are used before spraying filling; according to the filling ratio of gangue and concrete 8:2, it can be known that about 10.8m of concrete is needed to fill the 3m mining tunnel. 3 , the metering of concrete can be controlled by a mixing tank truck.

[0188] In order to ensure the compaction rate and top contact rate of the filling body, the shotcrete system and filling pump system are used, and the camera observation method is used to spray and re-fill the filled body every 5m in the mining tunnel.

[0189] The filling equipment is manually controlled outside the mine. During filling, a visual system is installed inside the mine to monitor the filling situation in real time. The relevant monitoring lines are laid along the gangue conveyor belt. The filling volume is calculated according to the filling time; the image data recorded during the filling process shall be kept for no less than 6 months.

[0190] (3) Drilling and filling holes on the upper side of the side

[0191] This plan arranges a filling station at a suitable position on the upper side of the wall. The filling station consists of a gangue crushing station, a belt conveyor, a raw material bin, a mixing tank, a filling pump, etc.

[0192] After the gangue is crushed (the particle size is less than 20mm), it is lifted to the mixing tank by the elevator. The cement and water in the raw material bin are transported to the mixing tank through the bottom pipe of the bin to mix with the crushed gangue and admixture to form a filling body. The filling body is transported to the mining tunnel by the filling pump through the drilled pipe constructed on the side wall for self-falling filling. The gravity and speed of the falling filling body are used as the power to crush the paste. At the same time, the last filling part is the top plate of the mining tunnel from top to bottom, and the top connection rate is relatively high.

[0193] It is designed to fill the tunnel every 5m. When the paste within 5m is full, in order to ensure the compaction rate and top connection rate of the filling body, the slurry retaining plate is used to squeeze the filled body, and then the self-moving pipeline filling vehicle retreats and continues filling until the tunnel is completely filled.

[0194] Since the mining tunnel is a blind alley, personnel cannot enter. The filling equipment is remotely controlled by humans outside the mining tunnel. During filling, a visual system is installed inside the mining tunnel to monitor the filling situation in real time. The relevant monitoring lines enter the mining tunnel along the self-moving slurry retaining device.

[0195] Based on the analysis of the above three filling schemes, the technical analysis comparison of each scheme is shown in the following table:

[0196]

[0197] Since the stability of the sidewall has high requirements on the top contact rate and compaction rate of the filling, and the sidewall coal compaction in this embodiment is only used for filling in the mining tunnel without recovering the coal pillar, from the perspective of the difficulty and cost of the process, this embodiment adopts the second scheme, that is, no coal pillar is recovered, and a dumper is used for filling in the mining tunnel. The filling operation of the mining tunnel (except for the crusher) can be completed on the working plate of the sidewall coal mining machine, and the designed width of the mining tunnel filling operation plate is not less than 80m. Fig.19 .

[0198] Process S2.2, filling material selection, based on the coal mine filling rate, the filling material ratio is gangue: concrete, and the filling ratio is about 8:2;

[0199] Process S3, slope stability calculation and analysis and slope monitoring, wherein the slope stability calculation and analysis includes determining the composition of the slope strata and using the limit equilibrium method and finite element method for mechanical analysis and calculation;

[0200] Specifically, this embodiment uses the limit equilibrium method and the finite element method to analyze and calculate the displacement, stress strain and stability of the slope of the mining area of ​​a certain mining field after mining.

[0201] The slope stability analysis and calculation selected the slope profile to establish the model. The slope height is 90m, and the final slope angle of the recovery area is 35°, which meets the requirements of slope stability after the side coal is recovered. According to the displacement stress cloud map, it can be seen that the displacement of the middle part of the top of the slope is large, and there is a certain tensile stress on the rear edge. The most dangerous sliding surface is searched, and the stability coefficient Bi shop method is calculated to be 1.188>1.1, and the overall slope is in a stable state. Specific analysis is as follows Figure 20-23 As shown, through the above analysis, it can be seen that after the side coal of the mine is mined, its slope stability is still in a stable state.

[0202] Slope monitoring includes the establishment of a monitoring network and the selection of monitoring equipment. The layout of the monitoring network is determined according to the terrain conditions of the observation area. The layout of the monitoring network is selected from one of the square grid, arbitrary square grid, cross grid, ray grid and baseline intersection grid. The monitoring equipment includes surface deformation monitoring equipment, slope stress monitoring equipment and groundwater monitoring equipment.

[0203] Specifically, in the process S3, the slope monitoring includes ground rock movement monitoring, establishing rock movement observation points on the ground around the mine, carrying out regular observations, and timely grasping the dynamics of the slope; flat plate rock movement monitoring in the mining area, arranging observation points on the working flat plate of the mine, forming a network distribution together with the ground observation points, regular observations, keeping track of rock movement at any time, and temporary rock movement monitoring of key areas; setting up temporary observation points for key areas, observing them periodically, monitoring local deformation, and making deformation or landslide forecasts in time; setting up surface monitoring points on the ground to monitor surface movement and subsidence, and the monitoring period should be no less than half a year.

[0204] Deep displacement monitoring is used to understand the deformation dynamics of deep rock mass. Underground rock mass displacement deformation monitoring holes are established. After the drilling rig forms a hole, a polyethylene pipe with a grooved slideway is installed in the hole. A mobile inclinometer is used for regular monitoring, thereby realizing the observation of the deformation dynamics of deep rock mass and making deformation predictions in a timely manner.

[0205] Manual monitoring is coordinated with ground rock movement monitoring, and professional personnel are arranged to patrol different areas to check the deformation of surface cracks or buildings so as to detect abnormal deformation at any time and take timely countermeasures.

[0206] In the process S3, Figure 24-25 ,Slope monitoring also includes sensor systems, data communication subsystems, data processing and control systems, lightning protection systems, and early warning systems;

[0207] The sensor system includes Beidou monitoring unit, crack collection unit, and groundwater collection unit. The purpose of the unit is to use Beidou technology to reflect the real-time three-dimensional changes of the monitored object;

[0208] The Beidou antenna of the data communication subsystem communicates with the Beidou host via coaxial cable; the Beidou host and other sensors communicate with the control center using wireless communication, crack monitoring uses wireless communication, and the groundwater collection unit uses wireless communication;

[0209] The data processing and control system receives and processes the data collected by the workstation system in real time, and displays the original data and processed data, and performs online evaluation and early warning.

[0210] The lightning protection system is used to protect the safety of equipment. It includes two parts: protection against direct lightning and protection against inductive lightning. Lightning rods are used to protect against direct lightning, and surge protectors are used to protect against inductive lightning.

[0211] When the data calculated by the software unit of the early warning system exceeds a certain current value, or when a sudden change occurs in the monitoring system, the early warning information is displayed in the form of a text message or on the monitoring server.

[0212] In the process S3, slope monitoring also includes a slope monitoring point arrangement method, which is selected at the deformation-sensitive parts of the slope. According to the slope type, the monitoring points are arranged near the trailing edge cracks, the leading edge slope foot, the leading edge ridges and other locking points with obvious stress concentration or controlled sliding. There are no less than 3 monitoring points on each monitoring line, with a spacing of 20 to 40 m. 1 to 2 monitoring points are set outside the slope perimeter. The monitoring technical methods adopt the Beidou monitoring system, radar system, rainfall monitoring, borehole inclinometer and crack displacement meter for monitoring.

[0213] Although the present invention has been disclosed as above with preferred embodiments, it is not intended to limit the present invention. A person with ordinary knowledge in the technical field to which the present invention belongs may make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, the protection scope of the present invention shall be determined by the definition of the claims.

Claims

1. A new type of coal mining method for open-pit mining, characterized in that: The process includes the following: Process S1, side coal mining machine recovery, process S1 includes: process S1.1, determined mining technology and transportation method, before the side coal recovery begins, the slope stability analysis and verification of the recovery section should be carried out in combination with the current situation of open-pit mining, and the side coal recovery operation can be carried out only when it is in a stable state, and the recovery parameters should be determined; Process S1.2, calculate the failure movement form of the coal seam roof, obtain the value of the mining width L and the maximum overhang span L0 of the roof rock layer, calculate the bending and tensile failure process and mechanical conditions of the rock layer, obtain the stress state of the embedded beam and the simply supported beam to obtain the bending and tensile mechanical conditions, and predict the mechanical process and conditions of the overhanging rock layer from bending to failure; Process S1.3, determination of mining parameters and coal pillar width; Process S2, mining tunnel filling, process S2 includes, process S2.1, determining the filling process, the filling process is to select one of pumping filling, dumping machine filling or side wall upper drilling and conveying filling; Process S2.2, filling material selection, based on the coal mine filling rate, the filling material ratio is gangue: concrete, and the filling ratio is about 8:2; Process S3, slope stability calculation and analysis and slope monitoring, wherein the slope stability calculation and analysis includes determining the composition of the slope strata and using the limit equilibrium method and finite element method for mechanical analysis and calculation; Slope monitoring includes the establishment of a monitoring network and the selection of monitoring equipment. The layout of the monitoring network is determined according to the terrain conditions of the observation area. The layout of the monitoring network is selected from one of the square grid, arbitrary square grid, cross grid, ray grid and baseline intersection grid. The monitoring equipment includes surface deformation monitoring equipment, slope stress monitoring equipment and groundwater monitoring equipment.

2. A new type of coal mining method for open-pit underground mining according to claim 1, characterized in that: Process S1.1 also includes that the side coal shearer is placed on the bottom plate of the corresponding recovered coal seam, the coal seam will be mined by the side coal shearer, and the coal will be transported by the belt conveyor. The unloading point will be loaded by the front loader, and the coal will be loaded by the front loader into the dump truck from the coal pile, and the dump truck will be transported to the surface coal storage yard of the open-pit mine; When there are multiple coal seams within the mining range of the side coal mining machine, the recovery of the covered coal seams shall be carried out in a bottom-up order according to the production progress of the open-pit mine and the demand for internal backfilling. That is, while ensuring the safe production of the open-pit mine, the recovery of the side coal is gradually carried out. After the recovery of the lower coal seam, the internal backfilling is immediately carried out. When the backfilling reaches the elevation of the bottom plate of the upper coal seam, the upper layer of coal is recovered. In this way, the side coal covering of each coal seam is gradually recovered. When tracking the inner discharge in the direction of advancement of the open-pit mine, when the upper and lower coal seams are both capable of recovery, the design determines that a side-wall coal mining machine will be used to recover the lower coal seam first according to the number of selected equipment models and the recoverable length of the exposed side wall. After the recoverable mining tunnels of the lower coal seam are mined, the upper coal seam that meets the operating conditions will be recovered; that is, only one side-wall coal mining machine is allowed to operate in the same time period, so that the inner discharge can be followed up after the lower coal seam is recovered, and the recovery space of the upper coal seam is expanded; It is designed to divide 10 mining chambers into one group along the direction of advancement of the open-pit mine, with one supporting coal pillar left between every two mining chambers and one isolating coal pillar left between every ten mining chambers. The mining chambers in each group are numbered 1#, 2#...10# in sequence, and the mining chambers numbered 1#, 2#...10# are mined in sequence during side-wall coal mining. It is designed that after the mining chambers are recovered, the mined mining chambers will be filled as soon as possible. Before the mining of the second group of mining chambers is started, the filling of the first group of mining chambers must begin, and before the mining of the third group of mining chambers is completed, the filling of the first group of mining chambers must be completed. During the mining-filling process, it is necessary to ensure that there is at least one coal pillar as a supporting coal pillar between the excavation mining chamber and the filling mining chamber.

3. A new type of coal mining method for open-pit underground mining according to claim 1, characterized in that: The process S1.2 also includes that, under the action of the overlying uniformly distributed load and its own deadweight, the cracking condition of point O in the middle of the rock beam is that its bending moment reaches a value that causes the tensile stress to exceed the limit, that is: Where: o —Actual tensile stress at point O; M0—bending moment at point O; W—section modulus of rock beam; For the embedded beam, the bending moments at the ends and the middle are For a simply supported beam, the bending moments at the ends and the middle are M A ＝0； From the above formula, it can be seen that the sum of the bending moments at the ends and the middle of the embedded beam is equal to the bending moment in the middle of the simply supported beam. After the end of the beam cracks, the bending moment at the end is transferred to the middle. Therefore, as long as the ends of the beam are pulled apart, the support conditions are quickly transformed to simply supported beams, and the pulling apart of the middle part will inevitably lead to bending and tensile failure of the rock beam. The mechanical process and conditions of the development of the overhanging rock layer from bending to failure can be summarized as: (1) When the working face advances to the rock beam overhang span limit value L0, the tensile stress at the beam end is At this time, since the overhanging rock layer is separated from the upper rock layer after bending and sinking, it is not affected by the gravity of the upper rock layer. Therefore, when the upper part of the overhanging rock layer is weaker than the upper rock layer, the rock layer is only affected by its own gravity, and the tensile stress σ at the end of the fracture is A for When there is a weaker rock layer above the overhanging rock layer, the rock layer is only affected by its own gravity, and the tensile stress σ at the end of the fracture A for Where: m—the thickness of the lower support layer with high strength, m; mi—thickness of the upper weaker rock layer that moves simultaneously with the supporting layer, m, (2) During the cracking process of the rock beam end, as the bending moment at the end decreases, the bending moment in the middle gradually increases, and the supporting force transforms to that of a simply supported beam. The numerical development of (3) During the transformation from an embedded beam to a simply supported beam, when the tensile stress in the middle of the rock beam achieve When the middle part is pulled apart, the rock beam will develop into a collapse or remain in a "pseudo-plastic rock beam" state. (4) The mechanical conditions for cracking at the ends and middle of the rock beam are: At this time, the maximum span of rock beam exposure L0 is when That is, when a single rock layer is bent and destroyed, the expression of L0 is: Obviously, the L0 value varies with the thickness of the rock beam m, and the allowable tensile strength [σ t ] increases with the increase of the soft rock thickness on the supporting layer. decreases with the increase of .

4. A new type of coal mining method for open-pit underground mining according to claim 1, characterized in that: The process S1.3 also includes:

1. Determine the width of the mining tunnel; According to the formula The maximum exposed span L0 of the direct roof of the mining tunnel during mining of each coal seam can be obtained, which is the width of the mining tunnel.

2. Determine the width of the coal pillar; According to the force analysis of the coal pillar, the pressure on the supporting coal pillar is half of the rock pressure above the coal pillar and half of the rock pressure above the mining tunnels on both sides of the coal pillar. The calculation formula for the width of the coal pillar is: a=γH(a+L) / P P-vertical stress borne by the coal pillar (kN / m2); γ-average bulk density of overlying rock (kN / m3); H-mining depth (m); the mining depth is determined according to the surface elevation of the borehole near the side coal recovery area and the elevation of the coal seam floor; a-Width of coal pillar (m); L-Width of mining shaft (m).

5. A new type of coal mining method for open-pit underground mining according to claim 3, characterized in that: In the process S3, the slope monitoring includes ground rock movement monitoring, which includes setting up rock movement observation points on the ground around the mine pit, carrying out regular observations, and timely grasping the dynamics of the slope; flat plate rock movement monitoring in the mining area, arranging observation points on the working flat plate of the mine pit, forming a network distribution together with the ground observation points, and conducting regular observations to grasp the rock movement at any time, and temporary rock movement monitoring of key areas; setting up temporary observation points for key areas, observing them periodically, monitoring local deformation, and making deformation or landslide forecasts in time; setting up surface monitoring points on the ground to monitor surface movement and subsidence, and the monitoring period should be no less than half a year. Deep displacement monitoring is used to understand the deformation dynamics of deep rock mass. Underground rock mass displacement deformation monitoring holes are established. After the drilling rig forms a hole, a polyethylene pipe with a grooved slideway is installed in the hole. A mobile inclinometer is used for regular monitoring, thereby realizing the observation of the deformation dynamics of deep rock mass and making deformation predictions in a timely manner. Manual monitoring is coordinated with ground rock movement monitoring, and professional personnel are arranged to patrol different areas to check the deformation of surface cracks or buildings so as to detect abnormal deformation at any time and take timely countermeasures.

6. A new type of coal mining method for open-pit underground mining according to claim 4, characterized in that: In the process S3, the slope monitoring also includes a sensor system, a data communication subsystem, a data processing and control system, a lightning protection system, and an early warning system; The sensor system includes Beidou monitoring unit, crack collection unit, and groundwater collection unit. The purpose of the unit is to use Beidou technology to reflect the real-time three-dimensional changes of the monitored object; The Beidou antenna of the data communication subsystem communicates with the Beidou host via coaxial cable; the Beidou host and other sensors communicate with the control center using wireless communication, crack monitoring uses wireless communication, and the groundwater collection unit uses wireless communication; The data processing and control system receives and processes the data collected by the workstation system in real time, and displays the original data and processed data, and performs online evaluation and early warning. The lightning protection system is used to protect the safety of equipment. It includes two parts: protection against direct lightning and protection against inductive lightning. Lightning rods are used to protect against direct lightning, and surge protectors are used to protect against inductive lightning. When the data calculated by the software unit of the early warning system exceeds a certain current value, or when a sudden change occurs in the monitoring system, the early warning information is displayed in the form of a text message or on the monitoring server.

7. A new type of coal mining method for open-pit underground mining according to claim 5, characterized in that: In the process S3, slope monitoring also includes a slope monitoring point arrangement method, which is selected at the deformation-sensitive parts of the slope. According to the slope type, the monitoring points are arranged near the trailing edge cracks, the leading edge slope foot, the leading edge ridges and other locking points with obvious stress concentration or controlled sliding. There are no less than 3 monitoring points on each monitoring line, with a spacing of 20 to 40 m. 1 to 2 monitoring points are set outside the slope perimeter. The monitoring technical methods adopt the Beidou monitoring system, radar system, rainfall monitoring, borehole inclinometer and crack displacement meter for monitoring.

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