Influence of rock and rock stability on mining method selection of gently inclined medium thick ore body

        1 Overview

The gently inclined medium-thick ore body generally refers to an ore body with a thickness of 5-20 m and an inclination angle of 5-30°. It is recognized as a difficult-to-mine body in the mining industry [1], and there are still many unsolved theoretical and technical problems [2]. . Mainly manifested in: the ore body is gently inclined, the ore can not slip, need to use mechanical handling or manual transport; the height of the open top of the stope is high, the roof management is difficult [3]; the amount of mining is large, the cutting ratio is high, resulting in The production capacity is small and the mining cost is high. In addition, the ore stability, ore value, ore body size and dip angle of this type of ore body are directly related to production safety, mining intensity, production cost, production efficiency and ore depletion index and mining quantity [4 ].
        2 describes the ratio Qian Xi copper ore mine southeast
        The southeast mining area of ​​the Chambishi copper mine is located in the copper belt province of Zambia, Africa, and the N1 ore body mainly mined in the southeast mining area. The ore body is in a set of shallow metamorphic muddy and sandy slate , which is layered and produced. It is subjected to wrinkle effect together with the surrounding rock, and the whole direction is northwest, which is basically consistent with the axial direction of the fold structure and tends to the northeast. The N1 ore body is 2700m long along the strike, and the trend is 569~1237m wide. The ore body is more stable along the strike and trend. In the horizontal direction, the plane projection pattern of the ore body is continuously distributed in an irregular strip shape. In the vertical direction, the ore body shape is layered, the ore body depth is 506~1067m, and the inclination angle is 5°-20°, as shown in Fig. 1. The average thickness of the ore body is 9.63m, the average grade of TCu is 2.31%, and the average grade of Co is 0.117%. The ore is a single type of sulfide ore and belongs to the primary ore.

        The surrounding rock of the ore body is mainly a set of shallow metamorphic rock layers with argillaceous quartzite as the main karst rock. The rock structure is dense, hard, stable and complete. Orebody footwall surrounding rock and quartz conglomerate rock, rock disc at all hard, stable and complete. Ore hardness coefficient: f = 6 ~ 8, hardness coefficient of surrounding rock: f = 10 ~ 12. The ore body itself is moderately stable.
The N1 ore body in the southeast mining area is currently in the infrastructure stage, with a designed production capacity of 10,000 t/d. The mine is expected to be completed and put into production by the end of 2017.
        In view of the occurrence conditions of the ore body, mining method research is underway. At present, the two tentative mining methods are stripe continuous recovery filling method and panel continuous recovery filling method. The mining processes of the two mining methods are briefly described and compared below.
        3-piece continuous recovery filling method
        3.1 stope structure parameters
        The stope is arranged along the strike. The length of the stope is 60m and the stage height is 100m. The stages are divided into sections according to the direction of inclination. The section height is 12m. If the inclination angle of the ore body is 15°, one section can be divided into 4 strips for mining. The stripe width is 12m (see Figure 2). The columns are reserved along the direction of the stope, leaving no inclination to the column. In order to improve the utilization rate of the ore block, the way of the ore body tends to adopt the "step alternate" bottom-up interval. In actual production, the segment height, strip width and quantity can be adjusted according to the change of the inclination angle of the ore body.

        3.2 mining cutting engineering layout
        A section of the outer slope of the ore body is constructed along the lower part of the plate, and a section of the alley is constructed along the slope of the slope. The stopway and the filling road are separately constructed from the sectioned roadway to the sides of the stope. Each stopway and filling roadway service adjacent to the two stopes, of which the filling roadway of the middle section is used as the top filling roadway of the lower section.
Along the lower part of the ore body, along the vein rock drilling roadway, the mining and excavation roadway is constructed between the rock drilling roadway, and the cutting patio is constructed in the middle of the mining field (see Figure 3). The stope of the stope is filled in time to prevent the large area of ​​the goaf from falling after the stop of the stope.

        3.3 Rock drilling and blasting
        The cutting groove is formed by the blasting of the free-faced porch in the central cutting patio of the stope. The construction is oriented toward the fan-shaped middle deep hole, and the cutting groove is used as the free surface.
        3.4 stope ventilation
        The fresh air flow enters the sectioned alley from the outer pulse slope, enters the stope through the stopway of the stope, and after the cleaning of the working surface, the dirty wind returns to the upper section and fills the returning smooth roadway, and is discharged to the return air well through the upper section. .
        3.5 Stope mining and filling
        The mining is carried out with a 4m3 scraper, which is loaded from the ore exit, through the stopway of the stope, and the sectioned transport lane is transported to the sectioned slip.

For the residual ore remaining in the stope, it can be considered to use the remote-controlled scraper to clean up, to avoid direct entry of personnel into the stope.
Each step of the stope shall be filled in time, and the filling pipeline shall be introduced into the stope from the top filling roadway. The retaining wall shall be set at the end of the ore-mining roadway and the rock-bearing roadway to prevent running sand. The gob area shall be all sand-blasted. With a 1:20 cementation filling, the self-standing can meet the production requirements, which maximizes the recovery of the ore body, but the cementing filling cost is relatively high.
        4-panel continuous recovery filling method
        4.1 stope structure parameters
        The arrangement of the mining houses along the strike will increase the number of mines without increasing the span of the mines, which is very beneficial to improve the production capacity of the mining areas. To this end, the design concept of “large-panel area and small-section” is proposed for the gently inclined medium-thick ore body. Specifically, the length of the panel is 500-800 m, the height of the middle section is 80-100 m, and the height of the section is 12-16 m.
        4.2 Mining engineering layout
        For the N1 ore body, an out-of-pulse return-type ramp is arranged at the central position of the panel to connect the upper and lower middle sections, and the sub-section and the intra-pulse section are laid at intervals of 16m vertical opening in the quasi-slope. The lanes are connected, and the length of the sectioned roadway is about 120m. Then, according to the inclination angle of the ore body, the slopes of the sections are inclined to the boundary of the panel along the slope of 10%~15% respectively. In the pseudo vertical height 8m inclined to the sides of the opening pulse drilling roadway construction, the final width of 16m is formed every mountain height of the vertical thickness of lead ore, stope length of 60m (see FIG. 4).

        The segmented ore chute is arranged on one side of the end of the segmented roadway, and the filling return air duct is located at the end of the panel to serve the adjacent panel.
        4.3 Blasting and mining
        After the end of the stope is grooved, the fan-shaped medium-deep hole is divided and retracted, and the scraper directly enters the stope for mining. When the distance from the mine point to the ore slip is greater than the reasonable transport distance of the scraper is 150m, the shovel is used. The transport mode of the truck is reversed, otherwise the scraper can directly drain the well. The ore is transported again to the main ore chute at the bottom of the middle section.
        4.4 stope ventilation
        The fresh air flow enters the sectioned alley from the slope of the panel, and then enters the stopway through the pseudo-sloping uphill and the stopway. After cleaning the working surface, the dirty wind is filled into the upper middle section and filled back by the filling back to the upper section. Alley.
        4.5 filling
        Overall, the mining and filling sequence of the panel is bottom-up. First, the stopway is closed, and the filling is transported to the stopway by laying the pipeline filled in the upper return airway and filling the return air well. Due to the tendency to fill along the ore body, the filling material can flow better by the action of gravity, which is favorable for filling and compacting, thereby improving the filling strength.
        5 mining methods comparison
        Advantages and disadvantages of 5.1 strip continuous recovery filling method
        The method has the advantages that the bottom structure of the trench is formed after the blasting, the way of the mine is discharged, the mining efficiency is high, and the operation is safe. There is no tendency for the pillars in the stope, and the stope is filled with cement, which can recover the strike column to the greatest extent. The ore loss rate is small, and the continuous recovery and filling of the stope is realized.
        Most of the cutting and cutting projects are arranged in the surrounding rock due to the continuous stripping and filling method, resulting in a small amount of by-product ore. Moreover, the method has a large amount of engineering and a long time for the formation of the stope, and it is difficult to ensure the balance of the third-grade ore.
        5.2 panel continuous recovery filling method advantages and disadvantages
        The advantage of this method is that the mining quantity is small, the cutting ratio is low, and the time required to form the stope is short. Once the panel mining is formed, the number of production yards can be produced at the same time, and the production capacity is large [5]. In addition, except for the slopes and slides in the panel, the other mining projects are arranged in the veins, with a large amount of by-products and minerals, and the mines are easy to reach production and stable production.
        However, the key to the successful implementation of this mining method depends on the stability of the ore body. The influence of ore body stability on the mining method is mainly manifested in two aspects [6]. Firstly, most of the mining methods are arranged in the vein and the service time is long, such as segmented roadway and pseudo-inclined uphill service. In a sub-stage production; secondly, the scraper directly enters the mining area to discharge the mine. The maximum exposed space in the open space can reach nearly 1000m2. If the traditional personnel is used to control the scraper to enter the mining area, there will be a large safety risk. . In this regard, the video control remote-controlled scraper can be used to enter the mining site for mining, and the personnel can operate in a safe area, which can fundamentally ensure the safety of the operator [7].
        Therefore, if the stability of the ore body and the surrounding rock is poor, the safety of the intra-pulse mining project during the service period will not be guaranteed. Even if the remote-controlled scraper is used, the scraper itself will face great risks. The mining method will Difficult to implement.
        6 conclusion
        The continuous mining and filling method of the panel requires the remaining pillars to have a panel along the top pillar, the segmented alley and the pseudo-inclined uphill protection pillar and the stop point column. The pillar has a large amount of ore. Therefore, how to safely and reasonably recover these mines (columns) and maximize the recovery of this part of mineral resources is a subject in production [8]. Therefore, when the ore body is exposed in the infrastructure stage, the research of the mining method should be carried out as soon as possible in a representative section. In the early stage, the stability of the ore body can be tested, and the exposed space equivalent to the size of the design stope can be blasted in the ore body. In the case of unsupported, observe and record the fall of the stope over time, and provide basic data for the selection and design of mining methods.
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