Safe and efficient mining method for medium to thick large ore body beneath quaternary overburden

Abstract

A safe and efficient mining method for a medium to thick large ore body beneath a quaternary overburden, comprising: dividing an ore body into a sublevel I, a sublevel II, a sublevel III and a sublevel IV from bottom to top in a vertical direction; reserving a crown pillar / rock pillar (3) at the top of the sublevel IV; reserving a horizontal isolation pillar (2) of a certain thickness every 2 or 3 sublevels (1); reserving vertical inter-pillars (4) at certain intervals in the sublevels (1); providing ore passes (12) at intervals of 40-150 m on one side of each ore drawing drift (11); and dividing the sublevel IV into 3-5 sub-stopes (15), providing a rock drilling drift (17) at the bottom of each sub-stope (15), forming a central slot raise (16) in the middle of the rock drilling drift (17), and forming fan-shaped medium-depth holes (18) in the rock drilling drift (17). Compared with conventional solutions, the production capacity of stopes is increased by 50% or more, and the mining cost per ton of ore is reduced by nearly 20%, resulting in significant economic benefits and achieving safe mining of medium to thick large ore bodies beneath a quaternary overburden.

Description

A safe and efficient mining method for medium-thick to thick large ore bodies in the Quaternary period. Technical Field

[0001] This invention belongs to the field of underground mining technology, specifically relating to a safe and efficient mining method for medium-thick to thick large ore bodies in the Quaternary period, which can be widely used in underground mining of solid minerals such as ferrous, non-ferrous, gold, chemical, and coal mines. Background Technology

[0002] With the decreasing availability of shallow, high-quality, and high-grade iron ore resources in my country, the development and utilization of deep-buried, poorly-located, and low-grade iron ore resources has become an urgent priority. Therefore, most of the mines recently developed or about to be developed in my country are large, thick Quaternary lower deposits.

[0003] Quaternary medium-thick to thick ore bodies refer to ore bodies with a thickness of over 5 meters and an overlying Quaternary layer of a certain thickness. Since the Quaternary system is mostly composed of sandy soil, silty clay, silty sand, and interbedded sandy soil, it generally contains porous aquifers, has a relatively loose structure, and low supporting strength; at the same time, the ore body thickness is medium to thick, allowing for large-scale mining. This type of ore body is widely distributed in central and eastern my country, with proven iron ore resources exceeding 5 billion tons, including areas such as Huoqiu and Zhunbei in Anhui, Zibo and Weifang in Shandong, and Xuchang in Henan.

[0004] The massive Quaternary lower deposits typically have flat surface terrain, mostly consisting of farmland and paddy fields. Ensuring the surface does not collapse or subside, or at least mitigating subsidence, is a critical issue when mining these deposits. Therefore, selecting and determining the appropriate mining methods is of paramount importance in addressing this challenge.

[0005] Currently, it is difficult to simultaneously achieve both safety and low-cost mining in this type of ore body. This is mainly manifested in:

[0006] (1) The traditional fan-shaped medium-deep hole or downward large hole mining method has a large exposed area and long exposure time in the mining area. Although it can achieve large-scale mining, it is easy to cause the surrounding rock of the mining area to collapse, which in turn leads to the influx of the overlying Quaternary and groundwater into the empty area, affecting the safety of underground production.

[0007] (2) If small-scale mining structure parameters are selected and a large number of pillars are left, the stability of the surrounding rock of the mining area can be guaranteed. However, the mining area has drawbacks such as large mining and cutting work, long preparation time, low production efficiency, low mining recovery rate, and serious waste of resources. This leads to excessive mining costs, which are difficult for mining enterprises to bear.

[0008] The article "Practice of Quaternary Confined Aqueous Mining in the Open-Pit Mine of Gushan Iron Deposit," published in the December 2011 issue of *Metal Mines*, describes a semi-enclosed, embedded, controllable double-liquid grouting curtain technology to seal the confined water in the deep Quaternary gravel and pebble layer. This successfully sealed the confined water in the lower gravel and pebble layer. A combination of pumping wells and channeling was used to control water drainage within the curtain. Combined with Quaternary slope stripping and layered advancement, replacement, slope protection, controlled blasting, and timely internal drainage and covering protection, this comprehensive technical approach effectively and safely mines Quaternary gravel and pebble confined aqueous ore bodies, successfully solving the production problems of open-pit mines in large water-filled areas. However, this technical solution has high mining costs and is not suitable for the safe and efficient mining of Quaternary underground ore bodies.

[0009] It is evident that there is currently no safe and efficient mining method for medium-thick to thick large ore bodies in the Quaternary system.

[0010] Summary of the Invention

[0011] The purpose of this invention is to address the problems of unsafe operation, large pillar loss, low production efficiency and high mining costs faced in mining medium to thick large ore bodies in the Quaternary system. This invention provides a safe and efficient mining method for medium to thick large ore bodies in the Quaternary system. Under the premise of ensuring safety, this mining method aims to maximize the ore recovery rate and stope production capacity while reducing mining costs, taking into account the technical conditions of mining medium to thick large ore bodies in the Quaternary system.

[0012] When the ore body thickness is less than 25m, the stope is arranged along the strike of the ore body; when the ore body thickness is greater than 25m, the stope is arranged perpendicular to the strike of the ore body. This invention addresses the technical challenges of medium-thick to thick ore bodies below the Quaternary strata, where the stope is arranged along the strike of the ore body. The upper part of the ore body is Quaternary, containing porous aquifers, with a relatively soft structure and low support strength, posing safety hazards and presenting significant mining difficulties, low mining efficiency, and low recovery rates. The following technical solution is adopted for implementation:

[0013] 1) Based on the thickness of the ore body, it is divided into several intermediate sections along the vertical direction of the ore body, which are intermediate section I, intermediate section II, intermediate section III and intermediate section IV from bottom to top; the intermediate sections are mined in a bottom-up order, and the empty areas are filled by tailings cementing after the mining of each intermediate section is completed.

[0014] 2) A protective pillar / rock pillar with a thickness of 10-30m is left at the top of the uppermost middle section—middle section IV to prevent Quaternary and its internal groundwater from flowing into the void during mining.

[0015] 3) Leave a horizontal isolation pillar of a certain thickness in every 2 to 3 intermediate sections to reduce the impact of the cumulative settlement and compression of the filling body on the upper roof support pillar / rock pillar and the Quaternary system.

[0016] 4) Vertical pillars are left at regular intervals in the middle section to support the upper roof pillars / rock pillars and the horizontal isolation pillars.

[0017] 5) The intermediate section I, intermediate section II, and intermediate section III mining areas adopt high-efficiency downward large-hole mining to improve the production capacity of the mining area and reduce mining costs. Top drilling chambers are located at the top of sections I, II, and III, while ore extraction roadways are located at the bottom of these sections. Ore passes are arranged every 40–150 m along one side of the ore extraction roadways, and loading and unloading routes are excavated every 10–15 m into the footwall of the ore body within the ore extraction roadways. A trench is excavated at the end of the loading and unloading routes, and fan-shaped medium-deep holes are arranged within the trench to form a bottom cutting groove. Downward large holes are arranged within the top drilling chambers. Blasting is performed using a stepped blasting method with the bottom cutting groove as the free face. The collapsed ore falls into the trench and is unloaded into the ore passes via the loading and unloading roadways using a loader. After the ore transportation in the stope is completed, all passages in the empty areas are sealed, and the empty areas are filled with tailings cemented to form a backfill body of a certain strength.

[0018] 6) Repeat step 5) to mine the remaining lower section II and section III mining areas until the end.

[0019] 7) Within the uppermost middle section—middle section IV—divide the area into 3 to 5 sub-mining areas. Use fan-shaped medium-deep holes for sub-mining to reduce the exposed area of ​​the mining area and shorten the mining time, further reducing the impact of mining on the safety of the upper Quaternary strata. Arrange drilling roadways at the bottom of the sub-mining areas, forming a central cutting groove in the middle of the drilling roadways. Arrange fan-shaped medium-deep holes in the drilling roadways, with the central cutting groove as the free surface for retreat mining on both sides. The collapsed ore falls into the drilling roadways and is unloaded into the ore pass through the loading and unloading roadways using a loader. After the ore transportation in the mining area is completed, seal all passages in the empty area and use tailings to cement and fill the empty area to form a backfill body of a certain strength.

[0020] 8) Install ramps in the footwall of the ore body to connect the middle sections and the top drilling chambers and ore extraction roadways within the middle sections, so as to facilitate the movement of trackless equipment and personnel.

[0021] Experimental studies have shown that a mid-section height of 50–100 m is preferred, and a sub-mining height of 10–25 m is suitable.

[0022] Furthermore, the length of each segmented mining area is 40–100 m.

[0023] Furthermore, the ore extraction roadways are arranged along the strike of the ore body, 10-20m away from the footwall of the ore body in sections I, II, and III.

[0024] Furthermore, the thickness of the horizontal isolation pillar is 10-20m; the width of the inter-pillar is 10-20m; and the ore pass is arranged every 50-100m on one side of the ore extraction roadway.

[0025] This invention discloses a safe and efficient mining method for medium-thick to thick large ore bodies in the Quaternary system. By employing roof pillars / rock pillars, horizontal isolation pillars, and inter-pillars, the method mitigates the disturbance impact of cumulative settlement and compression of the backfill body on the upper Quaternary strata. Simultaneously, it utilizes a combination of downward large-hole and fan-shaped medium-deep-hole mining methods, achieving safe and efficient mining. Specifically, it exhibits the following positive effects:

[0026] (1) The method of the present invention firstly leaves a certain thickness of roof support pillars / rock pillars in the upper part of the mining area to prevent Quaternary and groundwater from flowing into the void during the mining process; secondly, a certain thickness of horizontal isolation pillars is reserved every 2 to 3 intermediate sections to reduce the impact of cumulative settlement and compression of the backfill on the upper roof support pillars / rock pillars; at the same time, vertical inter-pillars are reserved at certain intervals in the intermediate sections to support the upper roof support pillars / rock pillars and the horizontal isolation pillars in each intermediate section, thus ensuring mining safety.

[0027] (2) The method of the present invention reduces the disturbance of the upper Quaternary by the cumulative settlement and compression of the backfill body on the premise of ensuring the recovery rate by leaving a certain size of roof support pillar, horizontal isolation pillar and inter-pillar, and reduces the impact of ore body mining on the upper Quaternary.

[0028] (3) The method of the present invention adopts downward large holes for mid-level mining in each of the lower mid-level mining areas (mid-level I, mid-level II and mid-level III), which greatly improves the production capacity of the mining area and reduces the mining cost. Meanwhile, the uppermost mid-level fan-shaped medium-deep holes are used for segmented mining, which reduces the exposed area of ​​the mining area and shortens the mining time, further reducing the impact of mining disturbance on the stability of the roof pillar / rock pillar, and realizing safe and efficient mining of the Quaternary lower medium-thick to thick large ore bodies.

[0029] (4) The method of the present invention divides the uppermost middle section into several sub-mining areas, selects fan-shaped medium-deep holes to carry out sub-mining from bottom to top, reduces the exposed area of ​​the mining area and shortens the mining time, further reduces the impact of mining on the upper Quaternary, thereby achieving safe and efficient mining of medium-thick to thick large ore bodies under the Quaternary.

[0030] Industrial test results show that, after adopting the above-mentioned technical solution, the mining recovery rate of the method of the present invention is reduced by 2-3% compared with the traditional solution, but the production capacity of the mining site is increased by more than 50%, and the mining cost per ton of ore is reduced by nearly 20%, resulting in significant economic benefits. At the same time, it realizes the safe mining of medium-thick to thick large ore bodies in the Quaternary system. Attached Figure Description

[0031] Figure 1 is a front view of the structural layout of a safe and efficient mining method for medium-thick to thick large ore bodies in the Quaternary system according to the present invention.

[0032] Figure 2 is a right view of the structural layout of a safe and efficient mining method for medium-thick to thick large ore bodies in the Quaternary system according to the present invention.

[0033] Figure 3 is a top view of the structural layout of a safe and efficient mining method for medium-thick to thick large ore bodies in the Quaternary system according to the present invention.

[0034] Figure 4 is a production process flow diagram of a safe and efficient mining method for medium-thick to thick large ore bodies in the Quaternary system according to the present invention.

[0035] The attached diagram is labeled as follows: 1—Mid-section; 2—Horizontal isolation pillar; 3—Roof pillar / rock pillar; 4—Interstitial pillar; 5—Inclined ramp; 6—Bottom cutting groove; 7—Top drilling chamber; 8—Downward large hole; 9—Trenching trench; 10—Ore loading entrance; 11—Ore extraction roadway; 12—Pass; 13—Backfill body; 14—Quaternary; 15—Subgrade stope; 16—Mid-section cutting groove; 17—Drilling roadway; 18—Fan-shaped medium-deep hole. Detailed Implementation

[0036] To better describe the present invention, the safe and efficient mining method for medium-thick to thick large ore bodies in the Quaternary system of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0037] As shown in Figure 4, and in conjunction with Figures 1, 2, and 3, the production process flow diagram of the safe and efficient mining method for medium-thick to thick large ore bodies in the Quaternary system of the present invention, indicates that in this embodiment, the upper part of the ore body is Quaternary 14. To ensure mining safety, the safe and efficient mining method for medium-thick to thick large ore bodies in the Quaternary system of the present invention is implemented using the following technical solution:

[0038] 1) Based on the thickness of the ore body, the ore body is divided into several intermediate sections 1 along the vertical direction, namely intermediate section I, intermediate section II, intermediate section III and intermediate section IV from bottom to top; the intermediate sections 1 are mined in a bottom-up order, and the empty areas are filled by tailings cementing after the mining of each intermediate section 1 is completed; the height of intermediate section 1 is 50-100m.

[0039] 2) A protective pillar / rock pillar 3 is left at the top of the uppermost middle section 1 to middle section IV. The thickness of the protective pillar / rock pillar 3 is 10 to 30m to prevent the Quaternary 14 and its internal groundwater from flowing into the void during the mining process.

[0040] 3) Horizontal isolation pillars 2 of a certain thickness are left for every 2 to 3 intermediate sections 1. The thickness of the horizontal isolation pillars 2 is 10 to 20 m, so as to reduce the impact of the cumulative settlement and compression of the filling body on the roof support pillar / rock pillar 3 and the Quaternary 14.

[0041] 4) Vertical interstitial pillars 4 are left at certain intervals in the middle section 1. The width of the interstitial pillars 4 is 10-20m, which are used to support the upper roof support pillars / rock pillars 3 and the horizontal isolation pillars 2.

[0042] 5) High-efficiency downward drilling is used for mining in the intermediate sections I, II, and III, which can improve the production capacity of the mining area and reduce mining costs. Firstly, a top drilling chamber 7 is installed at the top of each of the intermediate sections I, II, and III. Mining roadways 11 are installed at the bottom of each of the intermediate sections I, II, and III, arranged 10-20m away from the footwall of the ore body along the strike of the ore body. Ore passes 12 are arranged every 40-150m on one side of the mining roadway 11, preferably every 50-100m. Furthermore, a loading roadway 1 is excavated every 10-15m into the footwall of the ore body within the mining roadway 11. 0; A trench 9 is dug at the end of the ore loading access road 10, and a fan-shaped medium-deep hole is arranged in the trench 9 to form a bottom cutting groove 6; a large downward hole 8 is arranged in the top drilling chamber 7; blasting is carried out in a step-like manner with the bottom cutting groove 6 as the free surface, and the collapsed ore falls into the trench 9. It is then unloaded into the ore pass 12 by a loader through the ore loading access road 10 and the ore exit roadway 11; after the ore transportation in the mining area is completed, the passages in the empty area are sealed, and the empty area is filled with tailings cemented to form a filling body 13 with a certain strength;

[0043] 6) Repeat step 5) to mine the remaining lower intermediate section II and intermediate section III mining areas until the end;

[0044] 7) Divide the uppermost middle section 1 to middle section IV into 3 to 5 sub-mining areas 15, and adopt a sub-mining method to reduce the exposed area of ​​the mining area and shorten the mining time, further reducing the impact of mining on the upper roof pillar / rock pillar 3 and Quaternary 14. The height of the sub-mining area 15 is 10 to 25 m, and the length of the sub-mining area 15 is 40 to 100 m. First, a drilling roadway 17 is arranged at the bottom of the sub-mining area 15. A central cutting groove 16 is formed in the middle of the drilling roadway 17. Fan-shaped medium-deep holes 18 are arranged in the drilling roadway 17. The central cutting groove 16 is used as the free surface for retreat mining on both sides. The collapsed ore falls into the drilling roadway 17 and is unloaded into the ore pass 12 by a loader through the loading roadway 10 and the ore exit roadway 11. After the ore transportation in the mining area is completed, the passages in the empty area are also sealed, and the empty area is filled with tailings cemented to form a filling body 13 with a certain strength.

[0045] 8) An inclined ramp 5 is arranged in the footwall of the ore body to connect each intermediate section 1 and the top drilling chamber 7 and the ore extraction roadway 11 in the intermediate section 1, so as to facilitate the movement of trackless equipment and personnel.

[0046] This invention reduces the impact of ore body mining on the safety of the upper Quaternary strata by leaving roof pillars / rock pillars of a certain specification 3, horizontal isolation pillars 2, and interstitial pillars 4, while ensuring the recovery rate. The lower intermediate sections (intermediate section I, intermediate section II, and intermediate section III) adopt high-efficiency downward large-hole mining for intermediate section mining, which greatly improves the production capacity of the mining area and reduces the mining cost. The uppermost intermediate section adopts a medium-deep hole segmented mining method to reduce the exposed area of ​​the mining area and shorten the mining time, further reducing the impact of mining disturbance on the stability of the roof pillars, thus solving the problem of safe and efficient mining of medium-thick to thick ore bodies in the lower Quaternary strata.

[0047] This invention has been successfully applied in several underground iron mines in Anhui Province. Field verification has shown that although the recovery rate is 2-3% lower than that of traditional methods, the production capacity of the mining area has increased by more than 50%, and the cost per ton of ore has been reduced by nearly 20%, resulting in significant economic benefits. At the same time, it has enabled the safe mining of medium-thick to thick ore bodies in the Quaternary period.

Claims

1. A safe and efficient mining method for a medium-thick to thick ore body in the Quaternary system, wherein the upper part of the ore body is Quaternary (14), characterized in that... The following technical solutions will be adopted for implementation: 1) Based on the thickness of the ore body, several intermediate sections (1) are divided along the vertical direction of the ore body, which are intermediate section I, intermediate section II, intermediate section III and intermediate section IV from bottom to top; the intermediate sections (1) are mined in a bottom-up order, and the empty areas are filled by tailings cementing after the mining of each stope in the intermediate section (1) is completed. 2) A protective pillar / rock pillar (3) is left at the top of the uppermost middle section (1) to the middle section IV. The thickness of the protective pillar / rock pillar (3) is 10-30m to prevent the Quaternary (14) and its internal groundwater from flowing into the void during the mining process. 3) Leave a horizontal isolation pillar of a certain thickness for every 2 to 3 intermediate sections (1); 4) Vertical pillars (4) are set at regular intervals in the middle section (1) to support the upper roof pillars / rock pillars (3) and the horizontal isolation pillars (2); 5) The intermediate sections I, II, and III are mined using high-efficiency downward large-hole mining. A top drilling chamber (7) is provided at the top of each of the intermediate sections I, II, and III, and an ore extraction roadway (11) is provided at the bottom of each of the intermediate sections I, II, and III. A chute (12) is arranged every 40-150m along one side of the ore extraction roadway (11), and a loading roadway (10) is excavated every 10-15m into the footwall of the ore body within the ore extraction roadway (11). A trench (9) is excavated at the end of the loading roadway (10). In the trench (9), fan-shaped medium-deep holes are arranged to form a bottom cutting groove (6); in the top rock drilling chamber (7), downward large holes (8) are arranged; the bottom cutting groove (6) is used as the free surface for blasting in the inverted step manner, and the collapsed ore falls into the trench (9). The ore is unloaded into the pass (12) by a loader through the loading roadway (10) and the ore exit roadway (11); after the ore transportation in the mining area is completed, the passages in the empty area are sealed, and the empty area is filled with tailings cemented to form a filling body of a certain strength (13). 6) Repeat step 5) to mine the remaining lower intermediate section II and intermediate section III mining areas until the end; 7) Divide the uppermost middle section (1) to the middle section IV into 3 to 5 sub-mining areas (15), arrange rock drilling roadways (17) at the bottom of the sub-mining areas (15), form a central cutting groove (16) in the middle of the rock drilling roadways (17), and arrange fan-shaped medium-deep holes (18) in the rock drilling roadways (17). With the central cutting groove (16) as the free face, mining is carried out on both sides; the collapsed ore falls into the rock drilling roadway (17), and is unloaded into the ore pass (12) by a loader through the loading roadway (10) and the ore exit roadway (11); after the ore transportation in the mining area is completed, the passages in the empty area are sealed in the same way, and the empty area is filled with tailings cemented to form a filling body (13) of a certain strength; 8) A ramp (5) is arranged in the footwall of the ore body to connect each middle section (1) and the top drilling chamber (7) and ore extraction roadway (11) in the middle section (1).

2. The safe and efficient mining method for medium-thick to thick large ore bodies in the Quaternary system as described in claim 1, characterized in that: The height of the middle section (1) is 50-100m, and the height of the segmented mining area (15) is 10-25m.

3. The safe and efficient mining method for medium-thick to thick large ore bodies in the Quaternary system as described in claim 2, characterized in that: The length of each segmented mining area (15) is 40 to 100 m.

4. The safe and efficient mining method for medium-thick to thick large ore bodies in the Quaternary system as described in claim 1, characterized in that: The mining roadway (11) is arranged along the strike of the ore body, 10-20m away from the footwall of the ore body in the middle sections I, II, and III.

5. A safe and efficient mining method for a medium-thick to thick large ore body in the Quaternary system as described in claims 1, 2, 3 or 4, characterized in that: The thickness of the horizontal isolation pillar (2) is 10-20m.

6. A safe and efficient mining method for medium-thick to thick large ore bodies in the Quaternary system as described in claim 6, characterized in that: The width of the intercolumn (4) is 10-20m.

7. A safe and efficient mining method for medium-thick to thick large ore bodies in the Quaternary system as described in claim 6, characterized in that: The ore pass (12) is arranged every 50 to 100 m on one side of the ore exit roadway (11).

8. The safe and efficient mining method for medium-thick to thick large ore bodies in the Quaternary system as described in claim 3, characterized in that: The ore extraction roadway (11) is arranged 10-20m away from the footwall of the ore body in the middle section I, middle section II and middle section III along the strike of the ore body; the thickness of the roof support pillar / rock pillar (3) is 10-30m, the thickness of the horizontal isolation pillar (2) is 10-20m, and the width of the inter-pillar (4) is 10-20m; the ore pass (12) is arranged every 50-100m on one side of the ore extraction roadway (11).

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