An effective way to achieve low-depletion ore deposit without sub-column sublevel caving

No pillar sublevel caving has a simple structure, without leaving pillar, safe mining operations, mining strength and high efficiency, low cost, high labor productivity, nugget production capacity, etc., at home and abroad has been widely metal mines Applications. In recent years, with the continuous development of rock drilling and mining equipment, the structural parameters of the stopless sublevel caving mining method are gradually increasing, and its advantages are more obvious, and the promotion and application prospects are broad [1].
At the same time, the mining law has problems, mainly due to the high depletion rate of ore, which has been plaguing production mines. Most of the production mines use the cut-off method controlled by the cut-off grade to carry out the mining operation under the loose rock cover, which results in the loss of ore and the depletion. The ore loss rate and the depletion rate are usually maintained at 15%-25. %.
For a long time, for the problem of high depletion rate of sublevel caving without pillars, domestic and foreign mining science and technology personnel have done a lot of theoretical research and field test work, and their direction mainly focuses on the "ellipsoid ore mining theory" and "random medium." Based on the theory of ore-mining and the theory of ore-like blasting, the flow characteristics and movement laws of the caving rock are studied. In the practice of the mine, many researches have been carried out on the structural parameters of the stope and the management of the mining. Improvement, but most methods have had little effect [1]. On the basis of fully analyzing the movement law of caving rock during ore mining, Professor Liu Xingguo of Northeastern University officially proposed the theory of “no depletion ore” in 1991, and 25a came to test successfully in several mines, which was widely recognized by the industry. .

Iron Mountain Mine Jiuquan mirror Huashugou mine-free pillar sublevel caving, the design production capacity of 5 million t / a, the height of the segment 15m, approach distance of 12m, the Eastern 2640m, 2880m or less in the region, The West District II ore body is below 3015m, and the West District V ore body is below 2940m with a spacing of 18m. The upward fan-shaped deep hole blasting is used, the diameter of the blasthole is 76,100mm, and the step of the collapse is 2.2m.
The Huashugou mining area originally used the cut-off grade ore management method. Due to the low geological grade of the deposit, it is generally 35% to 37%, and the recovery grade after mining and depletion is only 28% to 33%; the ore is transported to a distance of 78km. Mineral processing in the metallurgical plant area, due to the high depletion rate of the ore, has a greater impact on the overall efficiency of the company. In order to solve the problem of high depletion rate and low grade of ore mining, Jingtieshan Mine has been experimenting, practicing and exploring for many years and achieved good results.
1 The ore mining situation in the Huashugou mining area
The Huashugou mining area used the traditional cut-off grade mining method before 2003. In order to ensure the selection effect and economic benefits, the company's planning department requires that the average grade of ore selected should not be lower than 32.5%. In actual production, the mine quality management department stipulates that the conditions for the mining of the face to stop mining are that the rock mixing rate is reached. 40%. This has kept the depletion rate and recovery rate of the Huashugou mining area at a low level (Table 1).

The traditional cut-off grade ore mining is based on the “independent ore-concentrating unit, and the ore is fully recovered as much as possible”. The ore with a single collapse step is fully recovered as the research object. Production practice and experimental research show that, with the traditional cut-off grade method, some pure ore is usually produced after a step blast, which accounts for about 30% of the ore discharge. With the advancement of the mining work, the ore is poor. The gradual increase, the interface of the rock and rock ruptures, and a large amount of rock is released from the rupture. The multiple incorporation of a large amount of waste rock is the root cause of the high depletion rate of the ore-free sublevel caving method and the low output grade. To this end, in 1993, the research team of Northeastern University conducted a non-depleted ore-concentration test in the ore body of the Birchou mining area on the basis of the completion of the study of the theory and laboratory of the depleted ore-free ore.
The difference between non-depleted ore and low-depleted ore deposits has been discussed [2]. I believe that the theoretical basis of the two methods is consistent. In the laboratory, each time the ore is released to the overburden and reaches the ore discharge, the rock stops the ore release, the depleted ore is not released, and the pure ore is released, which is called non-depleted ore. It is impossible to accurately identify the rock just to the ore discharge port, and it is necessary to put a small amount of rock into the explosion pile to be easily identified. Therefore, it is more reasonable and appropriate to refer to the non-depleted ore discharge in practice. Hereinafter referred to herein as low depleted ore.
The essence of the low-depletion ore-concentrating process is to realize the ore discharge under the ore cover layer and reduce the mixing of rocks during the ore-extraction process, thereby achieving the purpose of reducing the depletion rate. The low-depleted ore-concentration test in the Huashugou mining area was completed in four stages, and the first to second sections of the non-depleted ore-mining method were implemented. In addition to the significant decrease in the depletion rate index, the ore recovery rate also decreased. The fractional ore recovery rate will be close to or exceed the recovery rate at the cut-off grade and will remain stable, ie 75% to 80%. In 1993, in the II ore body test, the first stage of work was completed by 1995. From the test indicators, the ore grade of the II ore body increased by 1% to 1.2%, and the output grade of the whole mine increased by 0.5%. The test achieved expectations. The effect (Table 2), the non-depleted ore-concentration test was successfully promoted in the I ore body in 1996 after the success of the II ore body [3].

In the early stage of application, the low-depletion ore-mining method requires low recovery rate of the first two sections of ore, resulting in a significant decrease in ore production, a sharp increase in mining costs, and an increase in the short-term effect of mining lanes and deep hole consumption. Application promotion has caused great difficulties. Although Professor Liu Xingguo and Professor Zhang Zhigui have conducted detailed and comprehensive research, it is suggested that for the production mines using traditional cut-off ore mining methods, according to their actual conditions, they can choose “one step in place” and “quality transition” (gradually increase the mine discharge deadline). Grades and “quantity transition” (gradual expansion of the scope of use) and other specific ways to implement non-depleted ore mining [4], but the domestic mine receptor system and ideas and other constraints and restrictions, low depletion ore mining process is not very good Promotion and application. There are some problems in the promotion and application of low-depletion ore deposit in Jingtieshan Mine. First, it requires a lot of investment in the early stage. The management work is relatively complicated because it is different from the cut-off grade. The second is the low-depletion mine management. A long-term work cannot sacrifice the overall benefits for the current production interests, and must be strictly controlled in accordance with the low-poor ore-mining indicators. At the end of the test, the Jingtieshan Mine was not in place for the management of the mine, especially the implementation of the sampling and on-site management supervision responsibility system, which brought many adverse negative effects to the continuous and effective operation of the low-depletion work. The test results were promoted and applied.
2 Problems and analysis of low-depleted ore deposits
The factors that cause depletion in the sublevel caving mining method include the structural parameters of the stope, the method of mining, and the management of the ore. For the production mines with the determined structural parameters of the stope, reasonable mining methods and mine management are important means to improve resource utilization and mine efficiency.

Low-depleted ore-mining requirements require low-depletion ore-mining methods in addition to the final segmentation of the final segment. When a step is completed, a mixture of ore and rock is formed at this time; after several sections have been mined, due to the continuity of the movement of the collapsed ore, a certain thickness of ore is deposited on the upper part of the explosion (mineral mixture ), and with the decline of the segmentation, the proportion of ore in the rock mixture gradually increases. At this time, the interface of the rock is becoming more and more complete, and at the same time, the continuity of the moving space of the ore is utilized, and the front and the back are adopted. The method of throwing and picking below to improve the ore recovery rate [5]. Based on the production practice, the applicability conditions and problems of the low-depletion ore-boring method in the Huashugou mining area are combed (Table 3).

According to the analysis, the phenomenon of “suspension” and “pushing” after blasting is usually related to the influence of engineering geology on blasting, insufficient blasting compensation space, poor deep hole quality, insufficient charge density or poor explosive quality; The phenomenon of mineral rock mixing or early rock leakage is related to factors such as mining method and bucket width, and also related to the physical properties such as compaction, moisture, grain size, natural repose angle and adhesion. These factors will affect the effect of low-depleted ore. In particular, the initial preparation period is long, resulting in a decline in production and rising costs, making it difficult for the company's planning and finance departments to accept; in addition, some of the mining production outside the Huashugou is outsourced, and the outsourcing team is driven by economic interests, and it is difficult for workers to follow the poverty. The ore-mining indicators control the mining, which makes it necessary to explore the mining methods that can improve the recovery rate, reduce the depletion rate, and stabilize the ore grade.
Through the understanding of the theory and law of low-depletion ore-mining, it is considered that “the way to stop ore mining when the waste rock appears to be discharged immediately” is an external manifestation; after several stages of stepping out of the mine Afterwards, due to the spatial continuity of the collapsed ore, a certain thickness of ore (mineral mixture) is deposited in the upper part of the explosion to ensure that the ore is discharged under the cover of the ore (mineral mixture) rather than under the overburden. The essence of low depletion ore. Based on this, on the basis of summarizing and analyzing the past cut-off grade ore and low-depletion ore-boring practice in the Huashugou mining area, from the perspective of the method of ore-mining and ore-mining management, the bold cut-off of the grade and the total output of the mine is proposed. Combined mining method.
Mechanism analysis of the combination of cut-off grade and total amount of ore-mining
The method of combining the cut-off grade with the total amount of ore-mining control is to use the adjacent approach parallel mining and multi-funnel mining, which has not been required in the traditional cut-off grade ore and low-depletion ore-mining process. This is the key to the new approach.
The movement of the ore residue and the rock interface in the collapse step is mainly related to the mining method and sequence of the funnel. After a certain amount of ore is released by the adjacent approach, the ellipsoid height is far less than the height of the collapsed ore layer, and the adjacent ellipsoids are tangent to each other. The adjacent loose ellipsoid and the discharge funnel intersect in the range of the caving ore layer, and the upper and lower caving rocks interact and interact with each other, so that the ore contact surface is kept horizontally lowered, and the ore cover layer on the upper part of the explosion pile is uniformly reduced; The adjacent roads are retracted in parallel, and at the same time, the blasting and blasting are tangent. The two approaches are separated from the other channels in the ore. The ore between the funnels can be recovered better. Since the adjacent funnels perform the same amount of uniform ore-concentration, the mutual influence between adjacent funnels is basically the same, the contact surface of the ore is the smallest, and the loss of ore loss caused by ore mining under normal conditions is small [6]. When the recovery rate of individual approaching ore mining in the Huashugou mining area is as high as 110%-120%, the depletion rate remains below 10%, which reflects the consistency of the theory and practice of parallel feeding and multi-funnel mining in adjacent roads.
4 Application of cut-off grade and total output control combined with mining method
The ore-extracting method combining the cut-off grade and the total amount of ore-mining control has been described in detail in the literature [6] from the aspects of mechanism, mining process points and technical management system. The key points of this technology are as follows:
(1) Ensure that at least 4 access roads of each ore block are simultaneously withdrawn to facilitate the distribution of mines.
(2) Ensure that each approach is longitudinally in a line and simultaneously retracted in parallel.
(3) When the longitudinal direction of the access road in the ore block is not in a line, the long approach is taken first, and the second long approach is used for ore mining according to the method of this method. At this time, the approach of the miner may be Less than four; when the longitudinal direction of each way in the ore block is in a line, the mining is strictly carried out according to the technical points and technical management system.
(4) The adjacent steps in the ore block alternately match the ore amount and balance the ore.
(5) When the accumulated mined amount of the step has reached the target recovery rate, the mine can be terminated to prevent over-exploitation and over-excavation.
(6) When the condition (2) is satisfied, the adjacent two approaches are simultaneously blasted, and the ore is separated at intervals, and the cover layer is uniformly lowered.
Condition (6) is a new achievement obtained by using the mining method in the production practice of the past 2 years, and is carried out when there are many routes that require simultaneous parallel withdrawal, or when there are few routes, but there are simultaneous blasting conditions due to special circumstances. At this time, the adjacent approaches are simultaneously blasted, and the blasting bulk is tangent. The two approaches are separated from other access roads in the ore block to prevent the upper cover layer mineral mixture from advancing in advance, and the tangent part can be non-depleted. The effect, which greatly reduces the depletion rate of ore. If there are many mining routes in the ore block (the general ideal state is 8) and the condition (2) is satisfied, the adjacent two adjacent roads will be blasted at the same time, and the other adjacent blasting in the ore block may be mined. Good effect.
The ore-extracting method combining the cut-off grade and the total amount of ore-mining control was tested in the II ore body in September 2003. On this basis, the formation of the ore-mining management system was piloted in the I-II ore body. In 2004, it was applied to various mines. Body; for the problems found in practice continue to summarize, improve, improve, has now formed a relatively complete technical management system. This method has been used so far to not only improve the recovery rate, stabilize the grade of the ore, but also reduce the depletion rate (Table 4). Because the geological quality of the V ore body mined in recent years is only about 26%, it is currently in the experimental stage of the mining method, so it is not counted.
The I-II ore body in the Huashugou mining area is the operation of the employees in the mine. Over the years, the output accounted for more than half of the total output of the mining area, and other ore bodies were outsourced. In contrast, the I-II ore body performs cut-off grade and total ore output control. The combined ore mining system is better. Through the comparative analysis of the mining index of I-II ore bodies in recent years, the depletion rate has generally declined.
The I-II ore body has fully applied this method of mining from the 2730m level, and the ore depletion rate has been significantly reduced from the 2685m level in the fourth segment, achieving the effect of reducing the depletion rate (Table 5). Due to the downturn in the domestic steel market in recent years, the Jingtieshan Mine has reduced costs and increased efficiency. Some teams have over-extracted and over-excavated phenomena. If these factors are removed, the depletion rate of I-II ore bodies is around 8%. .

The method of demarcation combined with the cut-off grade and the total amount of ore-mining control is a form of ore-mining between the cut-off grade control and the low-depleted ore. In the current state of the mining site in the Huashugou mining area, if the economy allows, you can use the "quality transition" proposed by Professor Liu Xingguo and Professor Zhang Zhigui (gradually increase the cut-off grade of the ore discharge).
In the implementation plan, the depletion rate will be further reduced.

5 Conclusion
(1) The method of ore-mining combined with the cut-off grade and the total amount of ore-mining control has achieved the improvement of ore recovery rate and the stability of ore quality. After three stages of use, it has achieved low-depleted ore-reduction and reduced ore depletion rate. The expected effect.
(2) The method of ore-mining combined with the cut-off grade and the total amount of ore-mining control is a kind of ore-extracting form that transitions from the traditional cut-off grade ore-mining method to the low-depleted ore-mining. The ore-delivery effect is better than the traditional cut-off grade ore deposit. Compared with the standard low-depletion method, it is easy to promote and apply.
(3) The method of ore-mining combined with the cut-off grade and the total amount of ore-mining control is an effective supplement to the specific implementation methods of “one-step”, “quality transition” and “quantity transition” of low-depleted ore-mining. An effective way to reduce the effect of low-depletion ore mining without sub-column sublevel caving.

references
[1] Guo Lei, Xiong Yuhui. Status and development trend of sublevel caving without pillars [J]. China Mining Engineering, 2010 (6): 44-48.
[2] Zhang Zhigui. Analysis of "no depleted ore" and "low depleted ore" [J]. Metal Mine, 2004 (S1): 142-146.
[3] Zhang Zhigui, Liu Xingguo. Preliminary practice of low-depleted ore deposit in Jingtieshan Iron Mine [J]. Metal Mine, 1996 (10): 6-9.
[4] Zhang Zhigui, Liu Xingguo. Some problems concerning the application of non-depleted ore in the mine [J]. Chemical Mining Technology, 1995 (4): 18-22.
[5] Zhang Zhigui, Liu Xingguo, Yu Guoli. Sublevel caving without pillars without depletion ore [M]. Shenyang: Northeastern University Press, 2007.
[6] Lu Xiangdong, Yang Zuohua. Practice of the method of ore depositing by the sub-column sublevel caving method in Jingtieshan Mine [J]. Metal Mine, 2010 (2): 46-50.
Article source: "Modern Mining"; 2017.2
Author: Lv Xiangdong; Jiuquan Iron and Steel Group Company Copyright:

Semi Gantry Crane

Advantages of Semi Gantry Crane: