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Article

Study on the Effect of Ore-Drawing Shear Factor on Underground Debris Flow in the Block Caving Method

by
Xiangdong Niu
1,2,3,
Yalei Zhe
1,2,3,*,
Huafen Sun
1,2,
Kepeng Hou
1,2 and
Jun Jiang
1,2
1
Faculty of Land and Resources Engineering, Kunming University of Science and Technology, Kunming 650093, China
2
Yunnan Key Laboratory of Sino-German Blue Mining and Utilization of Special Underground Space, Kunming 650093, China
3
Yunnan Yarong Mining Technology Co., Ltd., Kunming 650000, China
*
Author to whom correspondence should be addressed.
Water 2023, 15(20), 3563; https://doi.org/10.3390/w15203563
Submission received: 16 August 2023 / Revised: 6 October 2023 / Accepted: 9 October 2023 / Published: 12 October 2023
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Abstract

:
The shear factor of ore drawing is an important factor affecting the formation of underground debris flows. The aim of this study was to investigate the effect of the mining shear factor on underground debris flows in natural caving. The research background was the underground debris flow in the Plan copper mine, and we analyzed the characteristics of the slurry material structure of the underground debris flow, as well as the influence of the ore-drawing shear factor on the formation mechanism of the underground debris flow. The results showed that the slurry of the underground debris flow in the Plan mine is both a pseudoplastic and thixotropic fluid. Shearing force induced in drawing deforms the slurry and decreases its viscosity with the increase in shear rate and time. The shear force produced by the flow of ore particles first produces shear action on the paste in the shear boundary region of the ore drawing, reducing the paste viscosity while increasing its fluidity. Consequently, the “activation” makes the paste flowable, which flows along with the bulk ore flowing through the drawing mouth. The continuous ore-drawing process continuously shears the new moraine slurry in the ore-drawing channel and continuously “activates” the moraine slurry in the ore-drawing channel. Finally, destructive underground debris flow accident of a certain scale occurs. To our knowledge, this study thoroughly investigated the effect of the ore-drawing shear factor on the formation mechanism of underground debris flows, which not only broadens the research field of debris flow but also covers the deficiency of systematic research on underground debris flows, providing theoretical guidance for the prevention and control of underground debris flows.

1. Introduction

Natural caving is a mining method with high mechanization, good safety, high production efficiency, and low cost. It is the only low-cost underground mining method comparable to open-pit mining. Natural caving has been widely used in different countries, but it is increasingly being used locally [1,2]. Some caving mines contain fine moraine or granular materials on the ground surface. Because of the small-sized particles in the upper covering layer of the caving ore, the existence of fine particles in the mine production area causes unconventional disasters during mine production. The Plan copper mine, for example, is a natural caving mine with fine moraine on the surface. As the mining depth increases, the scope of surface subsidence continuously expands. During the flood season, the mine easily experiences underground debris flow accidents, as the debris (moraine) overlying the stope is mixed with the rainwater and enters the stope through various channels [3,4,5]. Since 2019–2022, more than 10 underground debris flow accidents have occurred in the mine. The occurrence of an underground debris flow is extremely destructive because it is accompanied by bursts, which may carry high energy. The debris flow not only restricts the production capacity of the mine but also threatens the safety and efficiency of the mine [2,6,7].
In a narrow sense, an underground debris flow can be categorized as a mine debris flow. Mine debris flows occur in mountainous areas where mineral resources are concentrated. A debris flow induced by the change in the original topography and geological conditions due to man-made mining is also called a “man-made debris flow” [8,9]. Essential differences exist between mine debris flows and natural surface landslides, tunnel debris flows, and other geological disasters [10,11,12,13]. Although a debris flow is the source, topography (channel), rainfall, and other factors contribute to the non-synergistic variation in the coupling effect. However, the difference between an underground debris flow and a surface debris flow is that an underground debris flow is hidden and invisible because it occurs underground. The invisibility characteristic makes it difficult for researchers to study underground debris flow disasters. Currently, only a few local and foreign scholars have studied underground debris flows.
The formation and occurrence of an underground debris flow involve typical interactions between discontinuous and continuous media, and the solid–liquid two-phase fluid contains a large number of sediments, rocks, and boulders. The fluid is in a state of viscous laminar flow or dilute turbulent flow [14]. Because a debris flow is a two-phase fluid flow that includes solid and liquid phases, and the PFC3D (version 6.0) numerical simulation software uses the discrete element method to calculate the particle–particle interaction of the fluid, the software can effectively simulate the movements and interactions of solid particles in the debris flow; the CFD fluid module in the software can simulate the effect of water on solid particles in the debris flow [15]. Therefore, most scholars currently use the PFC particle flow software to conduct numerical simulation research on debris flow. Niu et al. [16] studied the start-up mechanism of underground moraine recharge debris flows under different rainfall intensities in the Plan copper mine. The study was conducted by field investigations and laboratory simulation experiments. The results showed that heavy rainfall provides hydrodynamic conditions for the formation of downhole moraine recharge debris flows. During pure ore drawing, it is difficult for surface moraine to form a channel in the ore bed, making it difficult for underground debris flow accidents to occur under different rainfall intensities. The formation of a flow passage for ground moraine in the ore bed is the precondition for the formation of underground debris flow. Deng [17] applied the accident-causing theory to analyze mud-bursting accidents in coal mines by considering factors such as human behavior, material state, management level, and environmental conditions. The author reported that mud-bursting accidents result from a combination of several factors, including inducing factors such as frequent production blasting as well as the vibration of trackless transportation and loading equipment. Basic principles and methods for preventing and controlling mud-bursting accidents were subsequently proposed. Song et al. [18] used the analytic hierarchy process (AHP-RRB) and expert questionnaire to study the index system of influencing factors of underground debris flows in the Chengchao iron mine. The results showed that the main influencing factors include rainfall and duration, thickness and property of surface loess layer, surface subsidence, mining activity, and artificial discharge of surface water. The authors found that the water source condition is the most important factor for controlling the underground debris flow, followed by the formation of a surface subsidence pit. By using the PFC3D particle flow numerical simulation software, Du et al. [19] studied the mechanism of underground debris flow in the Chengchao iron mine. They found that the mechanical essence of the formation of underground debris flow is the surface cracking and subsidence caused by caving mining, which leads to the accumulation of a large amount of viscous fluid composed of rock debris, mud sand, and water mixture on the goaf surface. Owing to the influence of mining activities such as drawing and blasting, when the overburden thickness is too thin to resist the debris flow pressure, disaster occurs by the sudden explosion and rapid flow under the action of gravity. Silalahi et al. [20] investigated the factors that influence debris flow. They reported that the long-distance movement of the ore can change the shape and size of the particles, which become fine and loose particles. In addition, the debris flow material is composed of small (diameter < 5 cm), saturated loose particles and water. Ouyang et al. [21] used seismic engineering simulation technology to perform OPENSEES finite element numerical simulation analysis on the relationship between blasting dynamic load and debris flow. The results showed that the dynamic loading of blasting has a great influence on the formation of a debris flow. After the loose covering over the caving ore is saturated with water during the rainy season, some liquefaction occurs to an extent under the influence of production blasting, which floods the mining site, inducing an underground debris flow accident. Krzysztof et al. [22] reviewed and summarized some experiences of underground deposit exploitation cases in Poland and Chile, and they observed that the block caving method is often used in large underground deposit exploitation in Chile. According to Khanal et al. [23], subsidence prediction analyses of mines in the Gunnedah Basin are found to be generally better than those of the Sydney Basin. These results presented here are based on limited data available in the public domain and although more data are needed to prove or disprove the discussed hypotheses, we consider that there is value in extending EIS requirements.
The action of ore drawing in a caved mine produces continuous shearing on the mud body (mud inclusion of moraine in the Plan mine) mixed into the ore bed, and the shear effect of ore drawing is a crucial factor influencing the formation of an underground debris flow. Only a few studies on underground debris flow disasters have identified inducing factors affecting the formation of underground debris flows, which mainly include mining activity, blasting vibration, and ore-drawing vibration. However, no study has reported the effect of ore-drawing shear on underground debris flows. Therefore, considering the complexity of the underground debris flow disaster as well as the urgency of determining effective prevention and control measures, this study investigated the impact of ore-drawing shear factors on the underground debris flow to minimize the probability of occurrence. This study was conducted on the underground debris flow in the Plan copper mine. The findings of this study are expected to address the deficiency of systematic research on underground debris flows and enrich the research on mine debris flows.

2. Analysis of Influence of Ore-Drawing Shear Factor

The Plan copper mine, which is owned by Yunnan Diqing Non-ferrous Metal Co., Ltd. (located in Shangri-la, China), is mined by natural caving; see Figure 1. The annual mining production scale is 12 million tons. The mine uses the one-shot blasting method with a medium-length hole and a hole depth of 8 m to 12 m. The ore loss rate of the mining method is 15–30%. An underground mine that adopts the natural caving method inevitably experiences surface material collapse during mining. The subsided material is the source condition of inducing underground debris flow. At the end of mining, underground mines will face the risk of an underground debris flow. Unlike surface natural debris flows, the underground debris flows are often more sudden, hidden, and highly destructive. Because an underground debris flow mainly occurs in a limited, enclosed space, it has a stronger destructive force. Thus, small-scale debris flows may cause serious disasters and accidents, which cause great invisible danger to the safety of mine production and technical personnel.
As a result of the relatively thick quaternary (Q) loose moraine cover on the surface of the mining area, which is shown in Figure 2, the mine has a large amount of quaternary loose granular material on the surface. Because of the existence of loose particles in the ground moraine, underground debris flow accidents are easily induced in the mine during the rainy season, which seriously threatens the safety of mine production. More than 10 underground debris flow accidents have occurred in the Plan copper mine since 2019, as shown in Table 1 and Figure 3.
Table 1 presents details of underground debris flow accidents at the Plan mine between 2019 and 2022. During the period of 2019–2022, at least 7 of the 10 underground debris flow accidents occurred under the influence of drawing shear without the influence of blasting vibration. Therefore, drawing shear is an important factor affecting the formation of underground debris flows, indicating that mine operators and researchers should pay more attention to drawing shear. This study investigated the effect of drawing shear on underground debris flows during drawing ore in mine production.
In addition, it should be noted that the remaining 30% of the underground debris flows were not recorded in the field because of the shock of the personnel on-site at the time of their occurrence; thus, it was difficult to determine whether they were related to the mining. To maintain the rigor of the analysis of this study, the 30% were not considered. However, the underground debris flow occurs in the natural caving mining underground mine. Because the ore has already collapsed, the mining pressure of natural caving mining mainly refers to the pressure of the falling ore in the range of the balance arch, which is relatively small in general. According to the information of 10 cases of underground debris flow in Table 1, 7 of them are affected by ore-drawing shear. Only ore drawing took place and none of the other mining activities took place. It shows that the effect of drawing shear factor on underground debris flow is great, but the effect of mining pressure on underground debris flow is negligible.

3. Analysis of Paste Structure Characteristics

3.1. Material Source of Debris Flow Slurry

During natural caving production in the Plan copper mine, the ore is inevitably depleted because of a continuous release. Based on the actual geometric size of the mine site, we used a 1:100 similarity ratio to simulate the formation of moraine channels in the caving ore bed. The fine moraine material on the surface of the quaternary system enters the caving ore bed, and the uneven ore drawing aids the formation of an ore bed channel storage for a large amount of moraine, as shown in Figure 4. During the rainy season, the atmospheric rainfall and surface runoff in the subsidence pit of the mine continually penetrate the ore layer, making the moraine fully absorb water and saturate. The moraine then exists in the ore layer in the form of moraine mud inclusion and slurry, as shown in Figure 5. As the ore is drawn during mine production, continuous shearing is induced on the moraine mud inclusion and slurry. The direct object of ore-drawing shear is the moraine mud inclusion and slurry stored in the caving ore bed. To perform laboratory rheological tests and thixotropic tests for moraine mud inclusions and pastes, field sampling of moraine slurry was conducted, as shown in Figure 6.

3.2. Analysis of Slurry Composition of Debris Flow

We determined the mineral composition of the original surface moraine and the slurry of the underground debris flow in the Plan copper mine. We also compared and analyzed the mineral composition of the surface moraine before and after the underground debris flow. These tasks were performed through an X-ray diffraction analysis of one group of primordial surface moraine and three groups of underground debris flow slurry samples [24,25], as shown in Table 2 and Figure 7.
Table 2 and Figure 7 show that the mineral composition of the moraine on the original surface of the Plan copper deposit is approximately the same as that of the slurry of the underground debris flow. The minerals are quartz, plagioclase, mica, potassium feldspar, chlorite, and amphibole. Thus, all the mud-rock flow slurry materials originate from the surface moraine, and no other external material is included.

3.3. Rheological Characteristics of Debris Flow Slurry

A high-precision soft solid rheometer, as shown in Figure 8, was used to test the rheological parameters (e.g., yield stress, viscosity) of the debris flow slurry under different concentrations [26]. The rheological equation was obtained, and the key factors affecting the rheological parameters of debris flow were analyzed.
The rheological properties of three concentrations (moisture content) under the conditions of the underground debris flow slurry samples are described below. The moisture contents of Samples 1, 2, and 3 were 63.81%, 71.07%, and 78.11%, respectively. The rheological curves of Samples 1, 2, and 3 of the underground debris flow are shown in Figure 9. The relationship between the shear stress and shear rate of the specimen at three concentrations (moisture content) is illustrated in Table 3 and Figure 10. Table 4 shows the statistical information of the shear stress and shear rate test results.
According to Figure 10 and Table 4, the relationship between the shear stress and shear rate of slurry Samples 1, 2, and 3 of the underground debris flow follows a power law, which is in accordance with the plastic fluid constitutive model.
A plastic fluid has a rheological curve: when the shear stress is less than τ0, the fluid will not flow; beyond τ, the fluid flows. A pseudoplastic fluid also has a rheological curve: the fluid flows once force is applied to it, and its viscosity decreases with the increase in shear rate [27,28,29,30]. For a Newtonian fluid, the rheological curve of shear stress against shear rate is a straight line starting from the origin. The swelling fluid also has a rheological curve: the fluid flows when an external force is applied to it, and the viscosity increases with the increase in shear rate [31,32,33]. The various rheological curves for different types of fluids are shown in Figure 11.
According to Table 4, the rheological indexes of Samples 1, 2, and 3 are all less than 1. In addition, according to Figure 11, Samples 1, 2, and 3 of an underground debris flow are all pseudoplastic fluids.

3.4. Analysis of Thixotropy of Mud-Rock Flow Slurry

At a constant temperature and constant shear rate, the shear stress and apparent viscosity of the fluid decrease with time. That is, the rheological properties are influenced by the time of stress action. This fluid is called a thixotropic fluid. Most time-dependent fluids are thixotropic, and a structure is formed between particles in a thixotropic fluid. The structure is destroyed when the fluid flows but restored when the flow stops. However, the destruction and restoration of the structure occur at different times. Therefore, the flow properties of thixotropic fluids are time-dependent. More precisely, if the viscosity of a slurry is temporarily reduced under shear deformation, the slurry is thixotropic.
The thixotropic tests of slurry Samples 1, 2, and 3 of the Plan mine underground debris flow were performed using a thixotropic fluid model [34]. The thixotropy curves are shown in Figure 12.
According to the flow characteristics of thixotropic fluid, the viscosity and shear stress of debris flow Samples 1, 2, and 3 in the Plan copper mine decreased with time. Therefore, Samples 1, 2, and 3 were thixotropic fluids.

4. Effect Mechanism and Preventive Measures

4.1. Effect of Ore-Drawing Shear on Underground Debris Flow

Debris flow materials move in the form of a slurry, which is a complex non-Newtonian fluid. According to the analysis of the rheology and thixotropy of a slurry, the debris flow slurry in the Plan copper mine is not only a pseudoplastic fluid but also a thixotropic fluid. The analyses indicate that when the shear force of drawing acts on the slurry, the slurry viscosity decreases with the increase in shear rate and time, finally becoming flowable.
During ore drawing in mine production, bulk ore is continually released at the ore-drawing mouth. Thus, the inclusions and pastes of moraine mud in the caving ore bed are sheared by the flow of bulk ore during the rainy season. The slurry of an underground debris flow is a pseudoplastic and thixotropic fluid. During ore drawing, the shear force produced by the flow of ore particles shears the slurry in the area of the drawing shear boundary (the contact interface between moraine slurry and ore particle), as shown in Figure 13. When the viscosity of the slurry in the ore-drawing shear boundary decreases, the slurry fluidity increases and the slurry becomes flowable. The slurry is finally released with the bulk ore through the ore-drawing mouth. In addition, because ore drawing is a continuous process, the shear force produced by the flow of ore particles continuously produces shear action on the new moraine slurry in the ore-drawing channel. Consequently, the moraine slurry in the ore-drawing channel is continuously “activated” and continually released, as shown in Figure 13. Because the slurry of an underground debris flow is the surface moraine slurry, the surface moraine slurry provides an abundant material source for the underground debris flow slurry, eventually forming a certain scale of destructive underground debris flow disaster.

4.2. Preventive Measures and Recommendations

This study shows that the ore-drawing shear factor has a critical influence on the formation of underground debris flow; this study also clarifies the influence mechanism. According to the characteristics of the effect of the ore-drawing shear factor on the underground debris flow slurry, we recommend the following preventive measures:
(1) In the drawing process, a strong relationship exists between the ore-drawing shear force and the ore-drawing velocity. In general, the larger the ore-drawing speed is, the larger the ore-drawing shear force is [35,36]. Therefore, during drawing in the rainy season, the underground debris flow can be prevented and controlled by reducing the ore-drawing speed as much as possible, which weakens the effect of the ore-drawing shear on the underground debris flow and reduces the occurrence probability of the underground debris flow.
(2) To reach the annual production capacity of the mine, we suggest mine operators adopt the dynamic drawing management system of “More ore in dry season and less ore in rainy season”. Because ore production reduces during the rainy season, the shear effect of drawing shear on mud inclusions can be reduced, the mud “Activation” can be prevented, and the viscosity and fluidity can be reduced. Thus, the occurrence of underground debris flows can be prevented and controlled. On the one hand, this recommendation can help the mine reach its annual production capacity; on the other hand, it can reduce the difficulty of preventing and controlling underground debris flows during the rainy season.
(3) We recommend that the monitoring and forecasting of surface rainfall should be strengthened during the rainy season in order to provide timely rainfall information for downhole mine drawing. In addition, the in situ measurements of the moisture content of the particulate matter at the mine outlet should be strengthened to obtain the status of the material at the mine outlet the first time. This would provide a primary source for the prediction and evaluation of underground debris flows, enabling timely and targeted prevention and circumvention measures.

5. Discussions and Future Developments

5.1. Discussions

The shear factor of ore drawing is an important factor affecting the formation of underground debris flows. The slurry of the underground debris flow in the Plan mine is both a pseudoplastic and thixotropic fluid. Shearing force induced in drawing deforms the slurry and decreases its viscosity with the increase in shear rate and time. The shear force produced by the flow of ore particles first produces shear action on the paste in the shear boundary region of the ore drawing, reducing the paste viscosity while increasing its fluidity. Consequently, the “activation” makes the paste flowable, which flows along with the bulk ore flowing through the drawing mouth. The continuous ore-drawing process continuously shears the new moraine slurry in the ore-drawing channel and continuously “activates” the moraine slurry in the ore-drawing channel. Finally, destructive underground debris flow accident of a certain scale occurs.

5.2. Future Developments

Natural caving is a mining method with characteristics of high mechanization, good safety, high production efficiency, and low cost. It is the only low-cost downhole mining method comparable to open-pit mining. Currently, natural caving is widely used in other countries, and the domestic application is a rising trend. This study showed that the ore-drawing shear factor is a key factor affecting the formation of underground debris flows and has an important contribution to the formation of underground debris flows. The natural caving method inevitably produces ore-drawing shear forces through the continuous release of the loose ore, and the ore-drawing shear force continuously shears the slurry, which induces frequent underground debris flow accidents. Although previous researchers have investigated the underground debris flow, they have not considered the impact of the mining shear factor on the underground debris flow. Our research results and other results from extensive analyses reveal the influence mechanism of the ore-drawing shear factor on the formation of underground debris flows, providing a theoretical basis for the prevention and control measures for underground debris flow. Therefore, compared with the previous research results, the research results of this study have high application prospects and wider applicability. In addition, the findings of this study are applicable not only to the case of natural caving mining, but also to the case of open-pit mining and underground mining.

5.3. Limitations

The interaction forces between particles are highly complex in the flow of granular systems. In this study, the effect of the ore-drawing shear factor on underground debris flows was examined from many aspects. However, because the interaction forces between particles in the ore-drawing process cannot be accurately measured from a technical perspective, the interaction forces between particles were not considered in this study, as well as the impact of the shear force of ore-drawing shear force on the underground debris flow. In addition, the research background of this study is the underground debris flows of the Plan copper mine. However, the same problem is encountered in natural caving mining. Hence, the results of this study have a certain universality and adaptability. However, this paper does not discuss the potential changes in ore properties, mining technology, and geological factors, which is also a limitation of the work. Therefore, we will make necessary adjustments in future studies to obtain more comprehensive findings.

6. Conclusions

In caving mining, the shearing action of drawing produces a continuous shearing action on the mud body in the loose ore body (mud inclusion of moraine in the Plan mine), which is an important factor influencing the formation of underground debris flows. Using the underground debris flow in the Plan copper mine, this study investigated the effect of the ore-drawing shear factor on an underground debris flow. The main conclusions drawn are as follows:
(1) As more than 10 underground debris flow accidents occurred in the Plan copper mine from 2019 to 2022, many underground debris flow accidents are affected by ore-drawing shear, which is an important factor affecting the formation of underground debris flow. Thus, the ore-drawing shear factor is a key factor affecting the formation of underground debris flow.
(2) Analyses of slurry rheology and thixotropy showed that the slurry of the underground debris flow in the Plan copper mine is both a pseudoplastic and thixotropic fluid. When the shear force of drawing is “activated,” the viscosity of the slurry decreases with the increase in shear rate and time, making the slurry flowable. The relationship between the viscosity and shear stress of the debris flow samples with different humidity values is as follows: Sample 1: τ = 59.141γ0.166, R2 = 0.951; Sample 2: τ = 16.661γ0.238, R2 = 0.930; Sample 3: τ = 4.318γ0.336, R2 = 0.955.
(3) Considering the structural characteristics, rheology, and thixotropy of the slurry of the underground debris flow in the Plan copper mine, we analyzed the influence of drawing shear on the formation mechanism of the underground debris flow. The shear force produced by the flow of ore particles first produces shear action on the paste in the shear boundary region of the ore drawing, decreasing the slurry viscosity while enhancing the fluidity. Thus, the slurry is activated and becomes a flowable paste that flows with the bulk ore flowing through the ore mouth. The continuous ore-drawing process continuously shears the new moraine slurry in the ore-drawing channel, which is continuously shear-activated and continuously discharged. Finally, a certain scale and destructive underground debris flow accident is formed.

Author Contributions

Conceptualization, X.N. and K.H.; methodology, X.N. and K.H.; software, Y.Z. and H.S.; validation, Y.Z. and H.S.; writing—original draft preparation, X.N.; investigation, X.N. and J.J.; data curation, Y.Z. All authors have read and agreed to the published version of the manuscript.

Funding

This research received no external funding.

Data Availability Statement

The basic data supporting the research results are all in the article.

Acknowledgments

The authors would like to thank all the reviewers for providing English editing services during the preparation of this manuscript.

Conflicts of Interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

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Water 15 03563 g001
Figure 1. A regional map and mining method map (unit: m). (a) A regional map of the mining area. (b) Mining method map of the Plan copper mine.
Figure 1. A regional map and mining method map (unit: m). (a) A regional map of the mining area. (b) Mining method map of the Plan copper mine.
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Figure 2. Quaternary (Q) loose moraine on surface of Plan copper deposit. (a) Profile of moraine thickness distribution. (b) Field map of Moraine in area of mining subsidence pit.
Figure 2. Quaternary (Q) loose moraine on surface of Plan copper deposit. (a) Profile of moraine thickness distribution. (b) Field map of Moraine in area of mining subsidence pit.
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Figure 3. Map of underground debris flow accident in Plan copper mine.
Figure 3. Map of underground debris flow accident in Plan copper mine.
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Figure 4. Formation process of moraine material flow channel under the condition of uneven ore drawing.
Figure 4. Formation process of moraine material flow channel under the condition of uneven ore drawing.
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Figure 5. Diagram of mud inclusion forms in collapsed ore bed.
Figure 5. Diagram of mud inclusion forms in collapsed ore bed.
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Figure 6. Field sampling of debris from the Plan mine.
Figure 6. Field sampling of debris from the Plan mine.
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Figure 7. Histogram of mineral composition of moraine and mud-rock flow in the original surface of the Plan copper mine.
Figure 7. Histogram of mineral composition of moraine and mud-rock flow in the original surface of the Plan copper mine.
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Water 15 03563 g008
Figure 8. High-precision soft solid rheological testing instrument.
Figure 8. High-precision soft solid rheological testing instrument.
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Figure 9. Rheological curve of slurry samples with different water contents. (a) 63.81% moisture content. (b) 71.07% moisture content. (c) 78.11% moisture content.
Figure 9. Rheological curve of slurry samples with different water contents. (a) 63.81% moisture content. (b) 71.07% moisture content. (c) 78.11% moisture content.
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Figure 10. Relationship between shear stress and shear rate of three samples with different moisture contents.
Figure 10. Relationship between shear stress and shear rate of three samples with different moisture contents.
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Figure 11. Rheological curves of different types of fluids.
Figure 11. Rheological curves of different types of fluids.
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Figure 12. Thixotropic curve of slurry sample of downhole debris flow (shear rate 90/s). (a) 63.81% moisture content. (b) 71.07% moisture content. (c) 78.11% moisture content.
Figure 12. Thixotropic curve of slurry sample of downhole debris flow (shear rate 90/s). (a) 63.81% moisture content. (b) 71.07% moisture content. (c) 78.11% moisture content.
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Figure 13. Mechanism of ore-drawing shear factor on underground debris flow.
Figure 13. Mechanism of ore-drawing shear factor on underground debris flow.
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Table 1. Statistics of underground debris flow accidents in Plan copper mine from 2019 to 2022.
Table 1. Statistics of underground debris flow accidents in Plan copper mine from 2019 to 2022.
Date of OccurrenceTime of OccurrenceMine Outlet of OccurrenceDebris Flow Volume (m3)Influencing Factors of Debris Flow Occurrence
25 July 201901:15S6-E161300The adjacent outlet is in drawing operation.
1 August 201900:10S8-E212200The adjacent outlet is in drawing operation.
18 August 201900:20S7-E13280The adjacent outlet is in drawing operation.
20 August 201921:10S6-E11120The adjacent outlet is in drawing operation.
9 September 201923:00S8-E14500No record.
11 October 201922:30S7-E18, S8-E13500No record.
17 August 202000:40S6-E27, S5-E281400The adjacent outlet is in drawing operation.
30 September 202013:30S5-E291500No record.
5 September 202103:20S1-E2810,000The adjacent outlet is in drawing operation.
2 July 202216:12N1-W21984The opposite outlet is in the process of ore drawing.
Table 2. X-ray diffraction mineral composition table of slurry material of underground debris flow in Plan copper mine.
Table 2. X-ray diffraction mineral composition table of slurry material of underground debris flow in Plan copper mine.
Name of MineralAverage Mineral Content (%)
Primordial Surface Moraine SamplesUnderground Debris Flow Sample 1Underground Debris Flow Sample 2Underground Debris Flow Sample 3
Quartz44.250.560.050.0
Chlorite20.87.57.09.0
Potassium feldspar14.25.38.511.0
Plagioclase12.521.212.014.0
Mica5.312.58.513.0
Amphibole3.03.04.03.0
Table 3. Table of relationship between shear stress and shear rate of samples with different concentrations.
Table 3. Table of relationship between shear stress and shear rate of samples with different concentrations.
Sample NumberNumber of Revolutions (r/min)60030020010063
Shear Rate γ (s−1)1021.8510.9340.6170.310.225.11
Sample 1Number of cells413329241716
Shear stress τ (Pa)209.51168.63148.19122.6486.8781.76
Sample 2Number of cells211412965
Shear stress τ (Pa)107.3171.5461.3245.9930.6625.55
Sample 3Number of cells1175421.5
Shear stress τ (Pa)56.2135.7725.5520.4410.227.665
Table 4. Statistical table of experimental results of shear stress and shear rate of specimens with different concentrations.
Table 4. Statistical table of experimental results of shear stress and shear rate of specimens with different concentrations.
Sample NumberMoisture Content wConstitutive Equation of FluidRheological Index nConsistency Index K
Sample 163.81%τ = 59.141γ0.166, R2 = 0.9510.16659.141
Sample 271.07%τ = 16.661γ0.238, R2 = 0.9300.23816.661
Sample 378.11%τ = 4.318γ0.336, R2 = 0.9550.3364.318
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Niu, X.; Zhe, Y.; Sun, H.; Hou, K.; Jiang, J. Study on the Effect of Ore-Drawing Shear Factor on Underground Debris Flow in the Block Caving Method. Water 2023, 15, 3563. https://doi.org/10.3390/w15203563

AMA Style

Niu X, Zhe Y, Sun H, Hou K, Jiang J. Study on the Effect of Ore-Drawing Shear Factor on Underground Debris Flow in the Block Caving Method. Water. 2023; 15(20):3563. https://doi.org/10.3390/w15203563

Chicago/Turabian Style

Niu, Xiangdong, Yalei Zhe, Huafen Sun, Kepeng Hou, and Jun Jiang. 2023. "Study on the Effect of Ore-Drawing Shear Factor on Underground Debris Flow in the Block Caving Method" Water 15, no. 20: 3563. https://doi.org/10.3390/w15203563

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