A method for mining open-pit mines with combined open-pit and underground mining of the lower coal seam at the end wall
Through hierarchical control technology and surrounding rock grading control, the problem of underground surrounding rock instability in open well joint mining has been solved, and efficient recovery of coal at the open-pit mine end is achieved, which has improved resource yield and economic benefits.
Patent Information
- Application Number
- CN202210335252.4
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2022-03-31
- Publication Date
- 2025-08-26
- Estimated Expiration
- 2042-03-31
AI Technical Summary
In open-pit joint mining technology, how to solve the problem of underground surrounding rock instability caused by the disturbance of the mine pressure slope between the complex systems composed of open-pit mine slopes-inner soil discharge sites-well industries and mines, especially how to recover the coal at the open-pit mine end to help press and stagnate coal and improve the resource yield rate.
Graded control technology is adopted to classify the surrounding rock based on the effective safety distance in excavation operations, combined with the hierarchical management of open-pit mines and underground mining, including the propulsion speed control and support measures of the inner discharge site to ensure the stability of the surrounding rock.
It effectively solved the problem of underground surrounding rock instability in open well joint mining technology, improved coal recovery rate, enhanced the stability of end-gathering slopes, reduced the impact of mining disturbances, and improved economic benefits.
Smart Images
Figure CN114704258B_ABST
Abstract
Description
Technical Field
[0001] The invention relates to the technical field of open-pit coal mining, in particular to an open-pit mine end wall lower coal seam open-pit mine joint mining process. Background Art
[0002] Open-pit coal production in my country accounts for approximately 15%-17% of the nation's total coal output. In 2020, the top ten coal mines in my country had a total approved annual production capacity of 280 million tons of raw coal. These 10 mines, including eight open-pit mines, have a combined capacity of 220 million tons per year. Due to safety concerns and mining process limitations, China's open-pit coal mines have relatively gentle slopes, resulting in a significant amount of coal being trapped on the side slopes. This trapped coal cannot be recovered after internal drainage and reclamation work is completed, resulting in significant resource waste. With dwindling coal resources and continuous advancements in mining technology, my country's coal mining trend is shifting from easily minable resources to more complex and difficult-to-mine resources. The recovery of trapped and residual coal from open-pit side slopes is gaining increasing attention. Combined open-pit and underground mining, which uses underground mining methods to recover trapped coal from open-pit side slopes, has become a key solution to this problem due to its high resource recovery rate, short dumping distances, low initial investment, and minimal land damage.
[0003] The current difficulty in applying open-pit and underground mining technology lies in the mine pressure slope disturbance between the complex system composed of the open-pit mine side wall, internal spoil dump and underground mining. How to solve the problem of underground surrounding rock instability caused by the manifestation of mine pressure under the conditions of open-pit and underground mining has become an important research topic. Summary of the Invention
[0004] In view of the problems existing in the prior art, the present invention provides a process for combined mining of open-pit mine end wall lower coal seam and open-pit mine.
[0005] The present invention is achieved through the following technical solutions:
[0006] A process for combined mining of open-pit mine end ridge lower coal seam and underground well mining comprises the following steps:
[0007] Step 1: Divide the mining area into underground and open-pit mining areas based on the mining area development plan, geological exploration report, plan and task book, open-pit and underground coal production costs, and geological environmental conditions. The underground mining industrial square in the underground and open-pit mining area is located above the spoil dump of the original open-pit mine, and the mining area includes the coal seam area below the original open-pit mine end wall that cannot be mined.
[0008] Step 2: Conduct preliminary design of open pit and underground mining according to the open pit and underground mining operation area of the mining area and determine the mining system;
[0009] Step 3: Determine the underground mining construction cycle according to the mining system, determine the impact section of the combined disturbance of underground mining and the open-pit mine dump pressure in combination with the open-pit mine production task progress and the internal dump advancement schedule, and control the excavation and coal mining operations according to the effective safety distance level; when mining, provide secondary support for the coal mining working face and surrounding rock.
[0010] Preferably, the mining system includes mining technology, mining procedures, development and transportation systems, underground mining face coal mining methods and well field development methods; wherein, the mining technology, mining procedures and development and transportation systems are determined according to the open-pit mine production specifications, and the underground mining face coal mining methods and well field development methods are determined according to the geological conditions of the coal seam.
[0011] Preferably, in step three, during mining, the open-pit mining method is semi-continuous mining combined with a single-bucket truck transportation process.
[0012] Preferably, during the open-pit mining process, the open-pit working wall slope moves back to the goaf, the inner spoil dump follows to fill the goaf, and the exposed end wall slope in the stope moves toward the goaf.
[0013] Preferably, when entering the open pit and well mining operation area, the advancement speed of the inner dump is greater than the advancement speed of the open pit working side; when leaving the open pit and well mining operation area, the advancement speed of the inner dump is less than the advancement speed of the open pit working side.
[0014] Preferably, in step three, the underground mining and open-pit mining areas are both developed using the inclined shaft single-level mining area method; when mining coal, the underground mining and open-pit mining areas are both developed using the backward longwall mining method.
[0015] Preferably, during coal mining, mine pressure monitoring of the mining face and whole-tunnel support work are performed on the mining face.
[0016] Preferably, the mining operation is subject to hierarchical management, and the specific steps are as follows: the bottom line of the bottom slope of the spoil dump in the open-pit mine is set as the observation reference line O, the front end of the working face during the excavation process is set as the observation point A, the effective safety distance from the front end of the working face to the observation reference projection point is first set, and the mining operation is hierarchically controlled according to the 0A distance; the effective safety distance is greater than or equal to 105m.
[0017] Preferably, the OA distance is divided into four levels according to 1000m, 500m, 300m and 105m for management and control.
[0018] Preferably, the specific operations of the control process are as follows:
[0019] When OA>1000m, the shaft, pit bottom parking lot, and permanent transport tunnel are arranged within this area, and the fourth level of risk rating management is implemented;
[0020] When 500m<OA≤1000m, the development working face with long service life of stage transport tunnel and stage return air tunnel shall be arranged in this area, and the three-level risk rating management shall be implemented; at the same time, the density of mine pressure monitoring base stations shall be increased, and full-time personnel shall be assigned to record and compile statistics;
[0021] When 300m<OA≤500m, mining working faces with short service life, such as working faces with air intake and return, are arranged in this area and secondary risk rating management is implemented; technical measures to strengthen support are formulated; these technical measures mainly include improving support methods, reducing support spacing, supplementing and strengthening support, and limiting the excavation progress per round shift;
[0022] When 105m<OA≤300m, the working face gas extraction tunnel of the first type, which has a short service life and does not require pedestrians after completion, shall be arranged in this area. The first-level risk rating management shall be implemented and support shall be further strengthened; the strengthened support mainly includes lengthening the length of anchor rods and cables, setting up U-shaped steel metal sheds, and limiting the excavation progress of each small shift.
[0023] Compared with the prior art, the present invention has the following beneficial effects:
[0024] The present invention adopts a hierarchical control technology for the open-pit mine end-wall lower coal seam combined mining process. This technology implements hierarchical control of the surrounding rock based on the effective safety distance during excavation operations, providing a technical approach for combined mining mine management. The effective safety distance and hierarchical control concepts are proposed, and based on this concept, a new method can be proposed to solve the problem of slope stability in the spoil dump within the combined open-pit mining. This also ensures the stability of the surrounding rock in the combined open-pit mining, resolving the technical difficulties faced by the application of the combined open-pit mining technology. This provides technical support for the large-scale application of the combined open-pit mining technology, recovering a large amount of coal compressed under the slope, improving the coal recovery rate, and achieving good economic benefits.
[0025] Furthermore, backfilling the inner dump prevents the end slope from shifting and increases its anti-slip properties. For the underground working face, backfilling the slope increases the load on the upper base of the working face, increasing horizontal sliding friction and suppressing horizontal displacement of the working face, contributing to its stability.
[0026] Furthermore, when entering the open-pit and underground mining area, the internal dump advances faster than the open-pit working wall, accelerating internal dumping and maintaining end wall stability. When leaving the open-pit and underground mining area, the internal dump advances slower than the open-pit working wall, alleviating the problem of tight internal dumping space in the open-pit mine.
[0027] Furthermore, the coal seams in the open-pit and underground mining areas are thick and gently inclined near the horizontal level, which is suitable for area-based development. The coal seams in the underground mining area are shallow, and the inclined shaft development technology is the most economical and simple. Affected by the disturbance of open-pit mining, single-level development is the safest and most reliable. When mining coal seams under such geological conditions, the longwall mining method has obvious economic and technical advantages, and the backward mining method can reduce the impact of open-pit slope disturbance on subsequent mining faces.
[0028] Furthermore, as the coal mining face retreats, the mining face is affected by the coupled disturbance of the open-pit mine slope and the coal mining face. The stress on the mining face is aggravated and the damage is serious. Therefore, during the mining process, it is necessary to always strengthen the mining pressure monitoring of the mining face and the re-support work of the entire tunnel.
[0029] Furthermore, the degree of disturbance caused by the open-pit mine's end wall to underground excavation varies under different levels of control. When OA is greater than 1000m, the impact of the open-pit mine's end wall on underground excavation is minimal, and risk rating level 4 management is implemented. When 500m is less than OA ≤ 1000m, the disturbance of the open-pit mine's end wall on underground excavation is initially apparent, and risk rating level 3 management is implemented. When 300m is less than OA ≤ 500m, the disturbance of the open-pit mine's end wall on underground excavation is more significant, and risk rating level 2 management is implemented. When 105m is less than OA ≤ 300m, the disturbance of the open-pit mine's end wall on underground excavation is severe, and risk rating level 1 management is implemented. BRIEF DESCRIPTION OF THE DRAWINGS
[0030] Figure 1 A schematic diagram of the opencast and well mining method provided by the present invention;
[0031] Figure 2 A schematic diagram of the effective safety distance provided by the present invention. DETAILED DESCRIPTION
[0032] The present invention will be further described in detail below with reference to specific embodiments, which are intended to explain the present invention rather than to limit it.
[0033] The present invention discloses a method for mining open pit mine bottom coal seam by open pit mining. Figure 1 , including the following steps:
[0034] Step 1: Divide the mining area into underground and open-pit mining areas according to the mining area development plan, geological exploration report, plan and task book, open-pit and underground mining coal production costs and geological environmental conditions; the underground mining industrial square in the underground and open-pit mining area is arranged on the upper part of the spoil dump in the original open-pit mine, and the mining range includes the coal seam area that cannot be mined at the lower end of the original open-pit mine.
[0035] Step 2: Conduct a preliminary design for open-pit and underground mining based on the combined open-pit and underground mining areas of the mining area and determine the mining system. The mining system includes mining technology, mining procedures, development and transportation systems, underground mining face coal mining methods, and wellfield development methods. The mining technology, mining procedures, and development and transportation systems are determined based on the open-pit mine production specifications, while the underground mining face coal mining methods and wellfield development methods are determined based on the coal seam geological conditions.
[0036] Step 3: Determine the underground mining construction cycle according to the mining system, determine the impact section of the combined disturbance of underground mining and the open-pit mine dump pressure in combination with the open-pit mine production task progress and the internal dump advancement schedule, and control the excavation and coal mining operations according to the effective safety distance level; when mining, provide secondary support for the coal mining working face and surrounding rock.
[0037] A hierarchical management system is implemented for mining operations. The specific steps are as follows: the bottom line of the bottom slope of the spoil dump in the open-pit mine is set as the observation reference line O, the front end of the working face during excavation is set as the observation point A, the effective safety distance from the front end of the working face to the observation reference projection point is first set (the effective safety distance is greater than or equal to 105m), and the OA distance is divided into four levels according to 1000m, 500m, 300m and 105m for management and control.
[0038] The specific operations of the control and treatment are as follows: When OA>1000m, the open-pit mine end wall has little impact on the underground excavation project. The shaft, bottom pit parking lot, and permanent transport tunnel are arranged in this area, and the fourth-level risk rating management is implemented;
[0039] When 500m<OA≤1000m, the disturbance of the open-pit mine end wall to the underground excavation project begins to appear. In this area, the development working face with long service life of the stage transportation tunnel and stage return air tunnel is arranged, and the three-level risk rating management is implemented. At the same time, the density of mine pressure monitoring base stations is increased, and full-time personnel are assigned to record and compile data.
[0040] When 300m<OA≤500m, the open-pit mine sidewalls significantly disturb the underground excavation project. In this area, mining working faces with short service life, such as the working face intake and return air working face, are arranged and implemented with secondary risk rating management. Strengthening support technical measures are formulated. Support technical measures mainly include improving support methods, reducing support spacing, supplementing and strengthening support, and limiting the excavation progress per round shift.
[0041] When 105m<OA≤300m, the end wall of the open-pit mine has a severe disturbance impact on the underground excavation project. The working face gas extraction tunnel arranged in this area has a short service life and does not require pedestrians after completion. The first-level risk rating management is implemented and support is further strengthened; strengthening support mainly includes lengthening the length of anchor rods and cables, supporting U-shaped steel metal sheds, and limiting the excavation progress of each small shift.
[0042] During mining, the open-pit mine adopts a semi-continuous mining method combined with single-bucket truck transportation. Development is carried out using a single-level mining area in an inclined shaft, and a backward-strike longwall mining method is employed. During the open-pit mining process, the slope of the open-pit working wall moves away from the goaf, and the internal dump follows to fill the goaf. The slope of the exposed end wall within the stope moves toward the goaf. When entering the open-pit and well combined mining area, the advancement speed of the internal dump is greater than that of the open-pit working wall; when leaving the open-pit and well combined mining area, the advancement speed of the internal dump is less than that of the open-pit working wall.
[0043] During coal mining, the mining pressure of the mining face is monitored and the whole tunnel support work is carried out on the mining face.
[0044] For underground mining, the single-level mining area is developed by inclined shaft; for coal mining, the backward longwall mining method is adopted.
[0045] This invention utilizes a hierarchical control technology for the open-pit mine combined mining process in the lower coal seam of the open-pit mine end wall. This technology implements hierarchical control of the surrounding rock based on the effective safety distance during excavation operations, providing a technical solution for combined mining management. Furthermore, the proposed effective safety distance and hierarchical control concept can be used to develop a new method to address the slope stability issues of the spoil dump within the combined mining process. This concept also ensures the stability of the surrounding rock during combined mining, resolving the technical challenges faced by the application of combined mining technology.
Claims
1. A process for combined mining of open pit mine end wall lower coal seam, characterized in that: The following steps are involved: Step 1: Divide the mining area into underground and open-pit mining areas based on the mining area development plan, geological exploration report, plan and task book, open-pit and underground coal production costs, and geological environmental conditions. The underground mining industrial square in the underground and open-pit mining area is located above the spoil dump of the original open-pit mine, and the mining area includes the coal seam area below the original open-pit mine end wall that cannot be mined. Step 2: Conduct preliminary design of open pit and underground mining according to the open pit and underground mining operation area of the mining area and determine the mining system; Step 3: Determine the underground mining construction cycle based on the mining system. Combined with the open-pit mine production task schedule and the internal dump advance schedule, determine the impact section of the combined disturbance of underground mining and open-pit mine dump pressure. Control excavation and coal mining operations in a graded manner based on effective safety distances. During coal mining, provide secondary support for the coal mining face and surrounding rock. The specific steps of graded control excavation are as follows: set the bottom line of the bottom plate slope of the spoil dump in the open-pit mine as the observation reference line O, set the front end of the working face during excavation as the observation point A, first set the effective safety distance from the front end of the working face to the observation reference projection point, and perform graded control on the mining operation according to the effective safety distance OA; the effective safety distance is greater than or equal to 105m.
2. The open-pit mine end wall lower coal seam combined mining process according to claim 1, characterized in that: The mining system includes mining technology, mining procedures, development and transportation system, underground mining face coal mining methods and well field development methods; among them, the mining technology, mining procedures and development and transportation system are determined according to the open-pit mine production specifications, and the underground mining face coal mining methods and well field development methods are determined according to the geological conditions of the coal seam.
3. The open-pit mine end wall lower coal seam combined mining process according to claim 1, characterized in that: In step three, during mining, the open-pit mining method is semi-continuous mining combined with single-bucket truck transportation technology.
4. The open-pit mine end wall lower coal seam combined mining process according to claim 3, characterized in that: During the open-pit mining process, the working slope of the open-pit mine moves back to the goaf, the internal spoil dump follows to fill the goaf, and the slope of the exposed end wall in the mining area moves toward the goaf.
5. The open-pit mine end wall lower coal seam combined mining process according to claim 4, characterized in that: When entering the open-pit and underground mining operation area, the advancement speed of the inner dump is greater than the advancement speed of the open-pit working side; when leaving the open-pit and underground mining operation area, the advancement speed of the inner dump is less than the advancement speed of the open-pit working side.
6. The open-pit mine end wall lower coal seam combined mining process according to claim 1, characterized in that: In step three, the underground mining and open-pit mining areas are both developed using the inclined shaft single-level mining area method; when mining coal, the underground mining and open-pit mining areas are both developed using the backward longwall mining method.
7. The open-pit mine end wall lower coal seam combined mining process according to claim 6, characterized in that: During coal mining, the mining pressure of the mining face is monitored and the whole tunnel support work is carried out on the mining face.
8. The open-pit mine end wall lower coal seam combined mining process according to claim 1, characterized in that: The effective safety distance OA is divided into four levels according to 1000m, 500m, 300m and 105m for management and control.
9. The open-pit mine end wall lower coal seam combined mining process according to claim 8, characterized in that: The specific operations of the control processing are as follows: When the effective safety distance OA is greater than 1000m, the shaft, pit bottom parking lot, and permanent transport tunnel will be arranged within this area, and the risk rating level 4 management will be implemented; When 500m < effective safety distance OA ≤ 1000m, the development working face with long service life of stage transport tunnel and stage return air tunnel shall be arranged in this area, and the three-level risk rating management shall be implemented; at the same time, the density of mine pressure monitoring base stations shall be increased, and full-time personnel shall be assigned to record and compile statistics; When 300m < effective safety distance OA ≤ 500m, a mining face with a shorter service life of the air intake and return working face is arranged in this area, and the second-level risk rating management is implemented; technical measures to strengthen support are formulated; these technical measures mainly include improving support methods, reducing the spacing between support rows, supplementing and strengthening support, and limiting the excavation progress per round shift; When 105m<effective safety distance OA≤300m, the working face gas extraction tunnel of the first type, which has a short service life and does not require pedestrians after completion, shall be arranged in this area. The first-level risk rating management shall be implemented and support shall be further strengthened; the strengthened support mainly includes lengthening the length of anchor rods and cables, setting up U-shaped steel metal sheds, and limiting the excavation progress of each small shift.