Broken ore body stoping method

Abstract

The invention discloses a broken ore body stoping method, relates to the technical field of mineral exploitation, and aims to improve the safety and efficiency of broken ore body exploitation. The method comprises the following steps that firstly, the trend, dip angle, thickness and rock mass integrity coefficient Kv of an ore body are obtained by combining three-dimensional seismic exploration with drilling CT scanning, independent mining units are divided according to the trend, dip angle, thickness and rock mass integrity coefficient Kv, safety isolation jambs are arranged, and then weak, medium and strong crushing subareas are divided according to the Kv value; secondly, pre-stressed anchor cables are constructed in the trend of the ore body to form a main bearing frame, and a corresponding supporting scheme is adopted in each sub-area; then, blast holes are arranged parallel to the trend of the ore body, the explosive loading amount is adjusted according to the crushing degree, segmented detonation is conducted, and the thin ore body is mechanically sawn for ore breaking; and finally, three-dimensional laser scanning monitoring points are arranged, tailings are cemented and filled immediately after the strong crushing area is mined out, and surrounding rock natural caving is triggered after the middle and weak crushing area is mined out temporarily and adjacent units are stoped. According to the method, differentiated mining and supporting are achieved, safety is guaranteed, and the resource utilization rate is increased.

Description

Technical Field

[0001] This invention relates to the field of mineral mining technology, specifically a method for mining broken ore bodies. Background Technology

[0002] In the field of mineral mining, fractured ore bodies have always been a key focus and challenge in mining operations due to the development of joints and fissures in the rock mass and their poor integrity. In particular, when there are multiple ore bodies with different orientations and heavy fractures in the area to be mined, traditional mining methods face many technical bottlenecks.

[0003] Existing mining strategies for fractured ore bodies often employ a single-mode approach, lacking targeted planning based on the spatial distribution characteristics of ore bodies with multiple strikes. Due to the varying stress transmission paths across different strikes, the traditional "one-size-fits-all" stope layout easily leads to localized stress concentrations, causing roof collapses, wall spalling, and other safety accidents, seriously threatening the safety of workers and equipment. Furthermore, traditional support systems often use a uniform full-section support model, which cannot adapt to the stability requirements of areas with varying degrees of fracture: insufficient support in highly fractured areas easily leads to collapse, while excessive support in less fractured areas results in material waste and increased costs. Moreover, the overlapping and interference between support and mining operations significantly reduces mining efficiency.

[0004] In the ore extraction process, traditional blasting methods fail to differentiate control based on the ore body's strike and degree of fragmentation. The direction of the blast holes does not match the ore body's strike, and the charge quantity lacks precise control. This not only easily exacerbates rock fragmentation due to the combined effects of blasting vibrations but also leads to uncontrolled ore extraction—some ore bodies are excessively fragmented and mixed with waste rock, resulting in a persistently high ore dilution rate; some marginal ore bodies are abandoned due to their high mining difficulty, leading to a resource loss rate exceeding 15%. Furthermore, in terms of goaf management, traditional monitoring methods rely heavily on single-point displacement meters, making it difficult to achieve dynamic monitoring of the entire irregular goaf area formed by multi-strike ore body mining. This hinders timely warnings of risks such as roof displacement and surrounding rock convergence, and the goaf treatment methods are simplistic, further exacerbating the difficulty of ground pressure management.

[0005] As mineral resource development extends to deeper areas and the proportion of complex ore bodies increases year by year, the demand for mining fractured ore bodies with multiple orientations is becoming increasingly prominent. The industry urgently needs a mining method that can achieve precise zoning, differentiated support, and ore drop control to address the shortcomings of traditional technologies in terms of safety, resource recovery, and mining efficiency, and to promote the upgrading and development of mining technologies for complex fractured ore bodies. Summary of the Invention

[0006] To address the shortcomings of existing technologies, this invention provides a method for mining fractured ore bodies.

[0007] To achieve the above objectives, the present invention provides the following technical solution: a method for mining fractured ore bodies, comprising the following steps:

[0008] Step 1: Using 3D seismic exploration technology combined with borehole CT scanning, the strike angle, dip angle, thickness, and rock mass integrity coefficient Kv of each ore body are obtained; the mining area is divided into multiple independent mining units based on the strike of the ore body as the core classification basis, and independent safety isolation pillars are set up; each mining unit is divided into weakly fractured, mediumly fractured, and strongly fractured sub-regions according to the Kv value.

[0009] Step 2: Construct prestressed anchor cables along the ore body strike of each mining unit to form the main load-bearing frame; weakly fractured sub-areas use "anchor bolt + shotcrete" support, mediumly fractured sub-areas use "anchor bolt + metal mesh + shotcrete" support, and strongly fractured sub-areas use "pipe roof + grouting + anchor bolt" combined support.

[0010] Step 3: The direction of the blast holes is parallel to the strike of the ore body. The amount of explosive charge is adjusted according to the degree of fragmentation of the sub-area. Millisecond delay detonators are used for segmented detonation. For thin ore body mining units with a thickness of less than 2m, mechanical sawing is used to cut the ore.

[0011] Step 4: Deploy three-dimensional laser scanning monitoring points in each mining unit to collect real-time displacement data of the goaf; after the strong fractured sub-area is mined out, immediately fill it with tailings cementation; after the medium and weak fractured sub-area is mined out, leave it temporarily, and trigger the natural collapse of the surrounding rock after the adjacent mining unit is mined out.

[0012] Preferably, the deviation of the ore body within each mining unit does not exceed ±10°.

[0013] Preferably, the crushing is weak (Kv>0.6), medium (0.3≤Kv≤0.6), and strong (Kv<0.3).

[0014] Preferably, in step 1, the width of the safety isolation pillar is not less than 1.5 times the maximum thickness of the ore body.

[0015] Preferably, in step 2, the prestressed anchor cable has a diameter of 22-25mm, a length that is 2-3 times the thickness of the ore body, a pre-tightening force of not less than 150kN, and a construction interval of 5-8m.

[0016] Preferably, in step 3, the hole depth is 0.8-1.0 times the thickness of the ore body, the hole spacing is 1.0-1.5m, and the row spacing is 1.2-1.8m; the linear charge density in the weakly fractured sub-area is 0.3-0.4kg / m, in the mediumly fractured sub-area it is 0.2-0.3kg / m, and in the strongly fractured sub-area it is 0.1-0.2kg / m, and the detonation time difference between adjacent sections is not less than 50ms.

[0017] Compared with the prior art, the present invention provides a method for mining fractured ore bodies, which has the following beneficial effects:

[0018] 1. By accurately delineating sub-regions based on the degree of fracture through 3D seismic exploration and borehole CT scanning, targeted support schemes such as "anchor bolt + shotcrete" and "pipe roof + grouting + anchor bolt" are adopted. Combined with the prestressed anchor cable main load-bearing frame and safety isolation pillars, the deformation of the surrounding rock can be effectively controlled. Real-time 3D laser scanning monitors the displacement of the goaf, and tailings cementing and backfilling are carried out in a timely manner in highly fractured areas, which greatly reduces the safety risks of collapse and spalling, and ensures the safety of workers and equipment.

[0019] 2. Independent mining units are divided according to the strike of the ore body. The layout of blast holes is parallel to the strike of the ore body. The charge amount is dynamically adjusted according to the degree of fracturing. Millisecond delay detonators are used for segmented detonation to reduce ore dilution. Thin ore bodies are cut off by mechanical sawing to avoid excessive damage to the ore body by blasting. In medium and weakly fractured areas, goafs are temporarily reserved to trigger natural collapse, simplifying the operation process and improving the overall mining efficiency and resource utilization rate. Detailed Implementation

[0021] The technical solution of this invention will be described in detail below using a case study of mining a complex and fractured ore body in a large iron ore mine. This iron ore mine is a sedimentary metamorphic deposit. The area to be mined contains four fractured ore bodies with different orientations. The ore bodies are stable, but the rock mass is fractured, meeting the application condition of this invention: "multiple fractured ore bodies with different orientations." The specific implementation steps are as follows:

[0022] Step 1: Three-dimensional exploration and zoning of ore bodies. High-precision three-dimensional seismic exploration technology was used to conduct full-area exploration of the mining area. Simultaneously, an exploration borehole was laid every 10m along the strike of each ore body. CT scanning of the boreholes was used to obtain the rock integrity coefficient Kv and ore body parameters. The exploration results showed: Ore body 1 strike 25°, dip angle 65°, average thickness 8m; Ore body 2 strike 55°, dip angle 62°, average thickness 6m; Ore body 3 strike 85°, dip angle 60°, average thickness 7m; Ore body 4 strike 115°, dip angle 58°, average thickness 5m; the Kv values ​​of each ore body were distributed in the range of 0.2-0.55. Based on the strike of the ore bodies as the core classification criterion, the four ore bodies were divided into four independent mining units. The strike deviation within each unit was controlled within ±9°; safety isolation pillars with a width of 12m were set between units (maximum ore body thickness 8m, 12m ≥ 8 × 1.5). The regions are further divided according to the Kv value: weakly fragmented sub-regions with Kv > 0.6 (5% in this example), moderately fragmented sub-regions with Kv ≤ 0.6 (65%), and strongly fragmented sub-regions with Kv < 0.3 (30%).

[0023] Step 2: Construction of the differentiated support system for each mining unit. Along the ore body of each mining unit, a row of prestressed anchor cables is constructed at 7m intervals: 24mm diameter high-strength low-relaxation steel strands are selected, with a length of 20m (2.8 times the average thickness of the ore body of 7m), and resin anchoring agent is used for anchoring. The pre-tightening force is applied to 170kN to form the main load-bearing frame at the top of the unit. The weakly fractured sub-area uses "anchor bolt + shotcrete" support: the anchor bolts are Φ22mm threaded steel, 3m long, spaced 1.5×1.5m apart, and the shotcrete is C30 concrete, 100mm thick. The moderately fractured sub-area uses "anchor bolt + metal mesh + shotcrete" support: the anchor bolt parameters are the same as in the weakly fractured sub-area, the metal mesh is Φ8mm steel woven, the mesh size is 150×150mm, and the shotcrete thickness is 140mm. The strongly fractured sub-area uses "pipe roof + grouting + anchor bolt" combined support: the pipe roof is Φ89mm seamless steel pipe, 8m long, with a circumferential spacing of 300mm, the grouting material is cement-water glass double-liquid grout (cement grout concentration 40%, water glass concentration 38°Be′, volume ratio 1:0.8), the grouting pressure is 2.0MPa, and Φ22mm anchor bolts are installed after grouting.

[0024] Step 3: The blast hole layout for ore cutting is parallel to the strike of the ore body, with a hole depth of 6.5m (0.93 times the average ore body thickness of 7m), a hole spacing of 1.4m, and a row spacing of 1.6m. The charge density is adjusted according to sub-regions: 0.35kg / m² for weakly fractured sub-regions, 0.28kg / m² for moderately fractured sub-regions, and 0.18kg / m² for strongly fractured sub-regions. Non-electric millisecond delay detonators are used for segmented detonation, with a time difference of 55ms between adjacent segments to avoid excessive damage to the iron ore rock mass from blasting vibrations. For the locally thin ore body section with a thickness of 1.8m in ore body 4, a hydraulic circular saw is used to cut along the strike, with a cutting depth of 0.7m each time. Manual cleaning is performed after sawing to reduce ore dilution.

[0025] Step 4: Dynamic Monitoring and Collaborative Processing of Goaf Areas. Three-dimensional laser scanning monitoring points are deployed at a density of 40m² / point within each mining unit to collect real-time data on roof displacement and surrounding rock convergence in the goaf area. The data is transmitted to the mine's ground pressure monitoring center. An audible and visual warning is automatically triggered when the displacement rate exceeds 5mm / d. In the strongly fractured sub-areas, tailings cemented backfilling is carried out within 6 hours after goaf extraction: the backfill material is iron ore tailings + ordinary Portland cement (mass ratio 10:1), and the cemented body achieves a 28-day compressive strength of 3.5MPa. In the moderately and weakly fractured sub-areas, goaf extraction is temporarily suspended until all four mining units are fully recovered. Controlled blasting is then conducted through pre-set Φ110mm blasting holes in the isolation pillars to trigger natural collapse of the surrounding rock, forming a buffer layer between the collapsed body and the goaf area.

[0026] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Anyone skilled in the art can readily implement the present invention according to the above description. However, any modifications, alterations, or equivalent changes made by those skilled in the art without departing from the scope of the present invention using the disclosed technical content are equivalent embodiments of the present invention. Furthermore, any modifications, alterations, or equivalent changes made to the above embodiments based on the essential technology of the present invention are still within the protection scope of the present invention.

Claims

1. A method for mining a fractured ore body, characterized in that, Includes the following steps: Step 1: Using 3D seismic exploration technology combined with borehole CT scanning, the strike angle, dip angle, thickness, and rock mass integrity coefficient Kv of each ore body are obtained; the mining area is divided into multiple independent mining units based on the strike of the ore body as the core classification basis, and independent safety isolation pillars are set up; each mining unit is divided into weakly fractured, mediumly fractured, and strongly fractured sub-regions according to the Kv value. Step 2: Construct prestressed anchor cables along the ore body strike of each mining unit to form the main load-bearing frame; weakly fractured sub-areas use "anchor bolt + shotcrete" support, mediumly fractured sub-areas use "anchor bolt + metal mesh + shotcrete" support, and strongly fractured sub-areas use "pipe roof + grouting + anchor bolt" combined support. Step 3: The direction of the blast holes is parallel to the strike of the ore body. The amount of explosive charge is adjusted according to the degree of fragmentation of the sub-area. Millisecond delay detonators are used for segmented detonation. For thin ore body mining units with a thickness of less than 2m, mechanical sawing is used to cut the ore. Step 4: Deploy three-dimensional laser scanning monitoring points in each mining unit to collect real-time displacement data of the goaf; after the strong fractured sub-area is mined out, immediately fill it with tailings cementation; after the medium and weak fractured sub-area is mined out, leave it temporarily, and trigger the natural collapse of the surrounding rock after the adjacent mining unit is mined out.

2. The method for mining a fractured ore body according to claim 1, characterized in that: The deviation of the ore body within each mining unit shall not exceed ±10°.

3. The method for mining a fractured ore body according to claim 1, characterized in that: The terms are: weak crushing (Kv > 0.6), medium crushing (0.3 ≤ Kv ≤ 0.6), and strong crushing (Kv < 0.3).

4. The method for mining a fractured ore body according to claim 1, characterized in that: In step 1, the width of the safety isolation pillar shall not be less than 1.5 times the maximum thickness of the ore body.

5. The method for mining a fractured ore body according to claim 1, characterized in that: In step 2, the prestressed anchor cable has a diameter of 22-25mm, a length that is 2-3 times the thickness of the ore body, a pre-tightening force of not less than 150kN, and a construction interval of 5-8m.

6. The method for mining a fractured ore body according to claim 1, characterized in that: In step 3, the borehole depth is 0.8-1.0 times the ore body thickness, the hole spacing is 1.0-1.5m, and the row spacing is 1.2-1.8m; the linear charge density in the weakly fractured sub-area is 0.3-0.4kg / m, in the mediumly fractured sub-area it is 0.2-0.3kg / m, and in the strongly fractured sub-area it is 0.1-0.2kg / m, and the detonation time difference between adjacent sections is not less than 50ms.