Study on Gob Area Treatment and Residual Mine Recovery Scheme in a Mine

For a long time, due to the extensive development of China's mining industry, some mining enterprises have abandoned the abandonment of poverty and chaotic excavation. Over time, the underground is irregular and difficult to handle the goaf and a large amount of ore is difficult to recover. A mining area has not been harvested in an orderly manner according to the planned three-level ore, and the underground mined area has not been treated in time, resulting in the loss of residual ore.
In the goaf, there have been different degrees of collapse. In order to prevent large-scale caving caused by further collapse of the goaf, and fully and effectively develop and utilize resources, a complete empty area treatment and residual mine recovery plan has been formulated.
1 Overview of the mining area
A mining area is located in the Yangzi quasi-station, the lower Yangtze platform pleat belt, the northeastern part of the Qinshui volcanic basin, the northern part of the Aijingshan-Lushan ring fault structure, and the northeastern margin of the Xiajiabian-Hanhu village resurrection volcano. The weak interlayer is relatively developed near the ore body. The ore body has a large difference in compressive strength due to the grade and kaolin strength, with an average of 317-495 kg/cm2, which is a semi-hard rock. At present, the mining is divided into -30, -70, -110, -150m4 middle sections. The mining methods and stope parameters of different middle sections are not the same. See Table 1 for details.

2 Overview of the goaf
2.1 Goaf detection
Commonly used methods for physical detection of underground goaf include high-density resistivity method, seismic mapping method, ground penetrating radar method and laser method [1]. This time, the laser method of space detection system CMS is used for -110m uncollapsed 3 The airspace is detected. The measured three airspace sections and planes are shown in Figure 1 and Figure 2.

According to the measured three-dimensional map, the basic parameters of the stoppage area of ​​404-406 in the middle section of -110m (Table 2) are obtained, and the actual goaf area above -110m is about 21,632m3.

It can be seen from the actual detection and on-site investigation that the shape of the column and the top column of the goaf formed by the original mining is irregular, but the residual ore is more and has a greater recycling value.
At present, seven empty areas in the middle section of -30m (two of which are mined by the sublevel caving method) and seven empty areas of -70m (two of which are mined by the sublevel caving method) have partially collapsed and collapsed. It is connected to the bottom of the open pit. Among the six empty areas of -110m, the 401-403 empty area has collapsed to some extent, and the 404-406 empty area has not collapsed.
In the middle section of -30m, the excavation lane of the stoppage of 201-204 is collapsed. According to the surveyed mining map and the investigation of the on-site access area, the 200 stope only has a partial bottoming, the stope area is 37.6m2; the 201 stope area is 258.9m2, the widest 8.1m, the longest 36.4m; the 202 stope area is 108.7m2, the widest 5m, the longest 24m; the 203 stope area is 100.6m2, the widest 6.3m, the longest 20.6m; 204 has no formal mining, but has carried out local shallow mining; 205 stope area is 77.11m2, the maximum width is 4.8m, the longest is 15m; 206 stope only has the bottoming operation, no mining; 208 The stope area is 57.31m2, the maximum width is 4m, and the longest is 15m.
The -70m middle section of the stope is fully filled, and the on-site pits are intact. According to the mining survey map, the 301 stope area is 125.8m2, the widest is 5m, the longest is 128m; the 302 stope area is 132.7m2, the widest 4.9m, the longest 42.5m; 303 stope area is 140.1m2, the widest 4.8m, the longest 43.6m; 304 stope area is 237.3m2, the widest 9.4m, the longest 30.9m; 305 stop length 23.17m At the northern end of the stope, the bottom and the falling mine (10m high) have been taken down, and only one outflow approach has been constructed; the 306 and 307 stope are mined by the sublevel caving method, the surrounding rock collapses, and there is no goaf. The columns between 301 and 305 are 5.8, 8.4, 20.8, and 9.1 m wide.
In the middle section of the -110m section, the section along the vein lane is intact, and the 404-406 stope is only partially collapsed. According to the mining survey map and the investigation of the site accessible area, the 401 stope adopts the small-section caving method, which has been collapsed and filled; The field area is 220m2, the widest is 7m, the longest is 38m; the 403 stope area is 287m2, the widest is 9m, the longest is 35m; the 404 stope area is 253m2, the widest is 7m, the longest is 32m; the 405 stope area is 235m2, The widest 7m, the longest 35m; 406 stop area is 168m2, the widest 5.8m, the longest 30m; the 402-404 stop between the columns are 5.4, 5.8m wide.
-150m middle section of the lower section along the vein lane is intact, basically mining according to the design, currently 501 is not mining; 502 ~ 504 completed mining, 502 stope area is 230m2, the widest 6.8m, the longest 33m; 503 stope area is 335.7m2 The maximum width is 9.6m and the longest is 35m; the 504 stope area is 328m2, the maximum width is 9.8m, and the longest is 33.2m; the 505 stope only has a bottoming and a small amount of mining operations; 506 is not mined. The columns between 502 and 505 are 6.5, 7.3, and 5.8 m wide respectively.
2.2 Types of goafs
The goaf treatment area is above -150m. The mined area has been formed. According to the basic data provided by the mine, on-site investigation and mining, the volume (area) of the goaf is not large as a whole, but the occurrence state is extremely complicated. The controllable degree of the empty area can be divided into the following two states:
(1) It is known that the goaf (Class A) includes visible mined areas that have not collapsed and invisible goafs that have collapsed but have documented empty areas, such as the middle section of 404-406 and -150m in the middle section of -110m. Gobs such as 502-504.
(2) Unidentified goaf (Type B), including visible goafs that have collapsed or indicate that there is a goaf in some place but the shape and distribution of the previous area are not clear, such as -70m or more The collapsed goaf.
2.3 Stability analysis of goaf
At present, except for the vacancies of the 404-406 empty area of ​​the -110m level, the other empty areas have collapsed to varying degrees. According to the investigation and analysis of these collapsed areas, it can be judged that the collapse is due to the ore body (empty area). The weak interlayer is developed nearby, and the highly unstable ore body is characterized by the fracture, softness and alteration of the kaolinite crystallized tuff , while the top pillars of the three unslowed areas in the middle of the -110m are intact. When the rock mass in the empty area is smashed, the 5m thick top column left in the mining process can withstand the impact of the collapse of the surrounding rock and the self-weight of the overlying rock after the collapse. At present, the overall occurrence environment of the three un-falling empty areas at -110m level is similar to that of other empty areas. The width, exposed area and actual volume of the empty area are relatively larger than other empty areas, except that there is a direct surface above the 405 stope. The rock is not mined, and the upper and lower rock masses (especially the upper rock mass) are relatively good and temporarily stable, but the continued mining disturbance of the lower -150m ore body may break the equilibrium state, therefore, the cementation is adopted. The filling method effectively treats the existing empty area in the middle section of -150m to ensure the safety of deep mining.
3 Gob area management
The goaf treatment methods include filling, isolation, permanent pillar support, caving surrounding rock and comprehensive treatment. This time, the sub-cavity surrounding rock is used to fill the ore-segmentation stage and the mining method is used to return to the mining column.
The 404~406 empty area in the middle section of -110m is basically intact. It adopts two modes: sub-level collapse and stage collapse. The -110m top column is collapsed and recovered according to the underground production status.
In order to fully recover the residual ore body while processing in the empty area, the -150m or more is divided into three stages and three levels, that is, -70m or more as the first recovery stage and the recovery level, and -110m or more as the second recovery stage. And the level of recovery, -150m or more as the third recovery stage and recovery level. Remnant of the last stage
The ore body can be partially recovered in the next stage.
This empty area is processed from top to bottom:
(1) After the filling of the -110m horizontal 405 empty area, the 206 stope will be recovered, and the ore mining can be discharged to the -70m level through the slip well, and then the 305 stope is recovered. After the end of the mining of 206 and 305, the pillars that have not collapsed from the north to the south retreat - above 70m, so that the rock mass that has collapsed before -33m will fall down by itself and fill the goaf. At this time, the empty area above -70m will be mixed with waste rock and ore, and the ore at the original ore column will be piled up. Due to the serious collapse of the goaf in the middle section of -70m, the stability of the surrounding rock in the stope is poor. The ore of the middle and above collapsed and collapsed is mined out in the original ore roadway at -70m level, and the right amount is recovered during the second and third steps. When the second step is carried out, it can be ensured that the empty area above -70 m is filled with waste rock.
(2) According to the mining method of ore body filling method below -150m, the cemented filling area of ​​the formed -150m horizontal goaf is firstly cemented, and then the top pillars of 401, 402, 403, 404 and 406 are collapsed from north to south. After each stope is filled with ore and waste rock, the column between the two empty areas is collapsed. At this time, because the mine is filled with waste rock, the pillar is only subjected to the weight of the overlying loose ore, so the pillar is more than the stop. The force condition before the top column collapses is much better. The pillar is collapsed in the middle section using the medium-deep hole bottomless column (or the mining method in the sublevel caving stage), and the collapse step from the upper plate to the lower plate is 2 to 3 m. It gradually collapses back into the mining column from the receding (when the sub-level collapses, the upper section is advanced and the lower section). At this time, it is equivalent to the high-end wall of the bottomless column caving method, and the ore is recovered as much as possible. At the same time as the 110m pillar mineral amount, the first layer of ore collapse or natural collapse can be recovered.
(3) According to the recovery of -150m and the residual ore recovery of -110m and the treatment progress of the empty area, the 501, 505, 506 stope is returned to the mining column from the north to the south by the upward stratified cementation filling method or the empty field å—£ filling method. .
4 residual mine recovery
According to geological data, production prospecting and empty area survey data, the residual mineral amount of -70m level and above is about 99,000 tons (including 20,000 tons of surface residual ore), and the residual mineral amount of -110m level is about 50,000t, -150m middle section. The top and the inter-columns of the 502-504 are about 32,000 tons. According to the occurrence of residual ore and the recoverable conditions, the actual recoverable ore is more than 90,000 tons. The residual ore amount above -150m is shown in Table 3.

4.1 top column collapse
Through the original patio when mining the pillars, the rock chamber is arranged at -67m horizontally. The size of the chamber is 3m×3m×2.2m. The horizontal deep hole is drilled by the SKZ-120A drilling rig in the rock drilling chamber. The hole diameter is 100mm, the bottom distance of the hole is 4.5m, only one row of blastholes is arranged for the roof collapse. Each of the two mines and one pillar is used as a caving unit. The length of each blasting hole is 38m, and the total length of the blasthole is about 274m, -110m. In the three recovery units, the total amount of deep holes in the top column collapsed was about 822 m.
4.2 column mining and engineering layout
According to the condition of the pillar and the rock mass of the upper and lower plates, the pillar can adopt two methods of stage rock drilling stage collapse and section rock drilling sublevel caving. When the rock condition is not good, the former is adopted, and vice versa.
Stage rock drilling stage caving plan: the pillar mining is fully utilized -110m existing project, using the SKZ-120A type down-the-hole drilling rig to drill the medium-deep hole in the vein of the -110m horizontal pillar, the hole diameter is 100mm, the row spacing is 2m The bottom distance of the hole is 4.5m, calculated according to the design of the pillar 6m wide, the maximum hole depth is 40m, the total length of each row of blastholes is 145m, each row of 4 rows of deep holes, the total length is about 580m, and the step of the collapse is 2m. Each row of blastholes will be mined to the cut-off grade. Since both sides of the pillars are filled with waste rock during the recovery of the pillars, the cutting wells (2m×2m) need to be arranged on the upper plate before mining.

Sectional rock drilling sublevel caving plan: make full use of the contact track when mining the column, the total length of each row of blastholes is about 58m, each column is divided into 3 layers, 5 rows of blastholes per layer, the total length of the blasthole is about 870m, when the plane collapses, the upper row is about 3m ahead of the lower row. Mineralization can be carried out in each stratification according to the site conditions, which is conducive to ore recovery and reduction of depletion, ensuring safe recovery.
5 safety technical requirements
(1) Before the empty area is treated, the surface collapse pit should be backfilled to the 18m level.
(2) The processing of the empty area is divided into three stages and three levels of processing, and the caving should be carried out in strict accordance with the order from top to bottom. Before the second stage of the collapse, the filling operation of the existing goaf of -150m is completed. -150m middle section bottom column (-205m middle section top column above) cementing isolation belt should be strictly designed and constructed according to filling mining design to ensure safe recovery.
(3) In the process of empty area treatment and ore body mining, all abandoned shafts connected with the goaf should be closed in time; personnel on-site inspection should be strengthened to timely understand the status of the goaf. Strengthen the monitoring and management of surface subsidence areas and underground empty areas, set up the goal, prevent personnel from entering the gobs and subsidence areas, and timely block the abandoned abandoned roads and empty areas.
(4) In the case of medium-deep hole blasting, the upward drilling of the larger diameter should be used, and the blasting should be carried out as soon as possible. The use of millisecond blasting reduces the impact of shock waves on the surroundings.
(5) Establish underground monitoring stations for underground and surface rock movements, and set up special personnel to monitor them regularly, make detailed monitoring records, analyze the monitoring results in time, and take corresponding safety measures.
(6) In view of the characteristics of mining column mining and empty area processing, it is required that technicians and safety personnel should follow the guidance and inspection during the construction of this empty area project, especially during the collapse of the pillars above - 110 m. Withdraw immediately and continue to work after you have determined your safety.

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