Method for analyzing influence of large-section rock drilling chamber ore pillar on stability of roof

Abstract

The invention relates to a method for analyzing the influence of large-section rock drilling chamber jambs on the stability of a roof, and belongs to the technical field of metal mine mining methods. According to the technical scheme, a rock drilling chamber ore pillar stability calculation model is constructed based on the Platt earth pressure theory and the Kathner equation, and rock drilling chamber ore pillar stability under the action of all influence factors is analyzed; carrying out influence factor sensitivity and interaction analysis by adopting a curved surface design method; when numerical simulation software is used for carrying out multi-step chamber mining, the stability of the roof of the rock drilling chamber is compared, analyzed and verified, and the size of the rock drilling chamber and the size of ore pillars reserved in the rock drilling chamber are further optimized. A new thought is provided for the method for analyzing the influence of the large-section rock drilling chamber jambs on the stability of the roof in the stope with subsequent stages, a theoretical basis is provided for size optimization of the rock drilling chamber and the jambs reserved in the chamber, and safe and efficient production of mines is guided.

Description

Technical Field

[0001] The invention relates to an analysis method for the influence of a large-section rock drilling chamber pillar on the stability of a roof, and belongs to the technical field of metal ore mining methods. Background Art

[0002] In the mining of complex and broken ore bodies, problems such as roof collapse and pillar damage are prone to occur, which not only threaten the safety of operators and equipment property, but may even cause great and unpredictable disasters. A stable mining site is a prerequisite for continuous mining in mines.

[0003] The empty field and subsequent filling mining method in the large-diameter deep hole rock drilling lateral caving stage is widely used in mines due to its advantages of large production capacity, less mining and cutting engineering, and high safety, especially in the mining of iron ore resources. Generally, in order to increase the production capacity of the mining field of this mining method and to ensure safety, a certain number of pillars are left in the rock drilling chamber to control the stability of the roof. However, during the ore-falling process, the pillars left in the chamber are mined together with the ore body, which has a great impact on the stability of the roof. Therefore, it is of great practical significance to explore the analysis method of the influence of the pillars in the rock drilling chamber of the subsequent mining field on the stability of the roof, further analyze the instability mechanism of the mining field, and then determine the reasonable size of the rock drilling chamber and the size of the pillars left in the chamber, which is of great practical significance for ensuring safe and efficient mining.

[0004] In the existing technology, scholars have studied the stability of the mining site or the optimization of the mining site structure parameters. Zhang Qinli et al. conducted a stability analysis of the mining site based on the cusp mutation theory and mechanical model, and found that the main factors leading to the instability of the mining site system are the strain softening and stiffness ratio of the pillars; Wang Xiaojun et al. analyzed the compressive performance of artificial pillars in deep ore bodies based on the Protzsprung's ground pressure theory, constructed a bearing capacity model and concluded that the mining span and depth are important factors affecting the width of artificial pillars; Guo Yang et al. used ABAQUS to carry out simulation experiments in the case of different stress distribution conditions in different mining sites, and believed that the excavation safety of the mining site is higher when the lateral pressure coefficient tends to 1; Xu Wenbin et al. used the orthogonal analysis theory based on the Voronoi diagram theory to study the sensitivity order of factors affecting the safety of the pillars, and put forward corresponding suggestions on how to maintain stability in the mining site; Liu Jianpo et al. carried out a joint acoustic emission monitoring and analysis of the surrounding rock of the ore body in the deep mining environment, and used the characteristics of the acoustic emission signal changes to obtain the time required for the ore rock to recover stability after the impact load.

[0005] The above research shows that the existing technology mainly focuses on the influence of stope structural parameters on the stability of the stope roof and the stability of the pillars left between the stopes. However, there are few research methods on the influence of the pillars left in the rock drilling chamber before mining in the large-diameter deep hole rock drilling lateral caving stage on the stability of the roof. Therefore, it is very necessary to design an analysis method for the influence of the pillars in the large-section rock drilling chamber on the stability of the roof, and then determine the reasonable size of the rock drilling chamber and the size of the pillars left in the chamber, so as to put forward reasonable suggestions for safe and efficient mining in mines. Summary of the invention

[0006] The purpose of the present invention is to provide an analysis method for the influence of the pillars of a large-section rock drilling chamber on the stability of the roof. By constructing a calculation model for the stability of the pillars of the rock drilling chamber based on the Protzsprung's ground pressure theory and the Kastner equation, the stability of the pillars of the rock drilling chamber under the action of various influencing factors is analyzed; the sensitivity and interaction analysis of the influencing factors are carried out by using a curved surface design method; when multi-step mine room mining is carried out using numerical simulation software, the stability of the roof of the rock drilling chamber is compared and analyzed and verified, the size of the rock drilling chamber and the pillars left in the chamber is further optimized, the safe and efficient mining of the mine is guided, and the above-mentioned problems existing in the background technology are effectively solved.

[0007] The technical solution of the present invention is: a method for analyzing the influence of pillars in a large-section rock drilling chamber on the stability of the roof, comprising the following steps:

[0008] (1) The calculation model of the stability of the pillars in the rock drilling chamber of the subsequent mining field in the construction stage is constructed based on the actual mining field, the Protz ground pressure theory and the Kastner equation. The main influencing factors of the stability of the pillars in the rock drilling chamber are determined, including: the width of the rock drilling chamber, the height of the rock drilling chamber, the internal friction angle of the surrounding rocks on both sides of the rock drilling chamber, and the rock strength coefficient of the roof of the rock drilling chamber;

[0009] (2) Based on the actual situation of the mining site and the stability calculation model, the influence of different influencing factors on the pressure concentration of the chamber roof is analyzed;

[0010] (3) Analysis of the sensitivity and interaction of influencing factors, using the BOX-BEHNKEN response surface design in the response surface methodology to explore the comprehensive impact of influencing factors on the pressure concentration of the top plate of the rock drilling chamber;

[0011] (4) Numerical simulation analysis and verification: A mine chamber model was established using numerical simulation software, and a multi-step mine chamber mining simulation analysis was carried out. The stability of the chamber roof was compared and analyzed under two schemes: leaving no pillars in the chamber and leaving pillars first and then collapsing with the ore body. Based on the analysis results, the parameters of the chamber and the pillars left in the chamber were further optimized.

[0012] In the step (1), assuming that the internal friction angle of the surrounding rocks on both sides of the stope length direction is φ, the slip angle θ of the surrounding rocks is: 45°+φ / 2, and the calculation formula for the span B1 of the natural equilibrium arch of the roof rock is:

[0013] B1=B+2Hctgθ

[0014] Where: B1 is the span of the natural balance arch of the rock in the stope roof, m; B is the width of the rock drilling chamber in the stope, m; H is the height of the stope, m; θ is the slip angle of the surrounding rock, °; φ is the internal friction angle of the surrounding rock, °;

[0015] The calculation formula for the height b1 of the natural equilibrium arch is:

[0016] b1=B1 / (2f)=(B / 2+Hctgθ) / f

[0017] Where: b1 is the height of the natural equilibrium arch, m; B is the width of the rock drilling chamber in the stope, m; H is the height of the stope, m; θ is the slip angle of the surrounding rock, °; f is the solidity coefficient of the roof rock;

[0018] The stress range of the pillar is the gravity of the roof rock mass, which has little to do with the rock mass outside the plastic zone. Therefore, the rock mass pressure distribution in the upper plastic zone can be approximately regarded as a uniform state. The calculation formula for the roof pressure concentration is:

[0019] q d =γgb1B1

[0020] Where: q d is the concentration of roof pressure in the mine, N / m; γ is the weight of ore, kg / m 3 ; g is the acceleration of gravity, N / kg; b1 is the height of the natural equilibrium arch, m; B1 is the span of the natural equilibrium arch of the rock on the roof of the mining area, m;

[0021] The formula for calculating the roof pressure over the entire mining space span is:

[0022] Q d =q d L

[0023] Where: Q d is the roof pressure of the mining area, N; q d is the roof pressure concentration in the mining area, N / m; L is the length of the drilling chamber, m.

[0024] In the step (2), the influence of different influencing factors on the pressure concentration of the chamber roof includes the influence of the width of the drilling chamber on the pressure concentration of the chamber roof, the influence of the height of the drilling chamber on the pressure concentration of the chamber roof, the influence of the internal friction angle of the surrounding rock on both sides of the drilling chamber on the pressure concentration of the chamber roof, and the influence of the rock strength coefficient of the drilling chamber roof on the pressure concentration of the chamber roof.

[0025] In the step (3), the comprehensive influence of the influencing factors on the pressure concentration of the top plate of the drilling chamber includes the comprehensive influence of the width of the drilling chamber and the height of the drilling chamber on the pressure concentration of the top plate of the chamber, the comprehensive influence of the width of the drilling chamber and the internal friction angle of the surrounding rock on both sides of the drilling chamber on the pressure concentration of the top plate of the chamber, the comprehensive influence of the width of the drilling chamber and the rock strength coefficient of the top plate of the drilling chamber on the pressure concentration of the top plate of the chamber, the comprehensive influence of the height of the drilling chamber and the internal friction angle of the surrounding rock on both sides of the drilling chamber on the pressure concentration of the top plate of the chamber, and the comprehensive influence of the internal friction angle of the surrounding rock on both sides of the drilling chamber and the rock strength coefficient of the top plate of the drilling chamber on the pressure concentration of the top plate of the chamber.

[0026] In the step (4), the comparative analysis includes comparative analysis of top plate stress, comparative analysis of side wall stress, comparative analysis of top plate plastic zone and comparative analysis of side wall plastic zone under two schemes.

[0027] The beneficial effects of the present invention are as follows: by constructing a calculation model for the stability of the pillars in the rock drilling chamber based on the Protz ground pressure theory and the Kastner equation, the stability of the pillars in the rock drilling chamber under the influence of various influencing factors is analyzed; the sensitivity and interaction analysis of the influencing factors are carried out by using the surface design method; when using numerical simulation software to carry out multi-step mine room mining, the stability of the roof of the rock drilling chamber is compared and analyzed and verified, the size of the rock drilling chamber and the pillars left in the chamber are further optimized, and safe and efficient mining of mines is guided. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 is a flow chart of the method of the present invention;

[0029] Figure 2 It is a force analysis diagram of the upper part and both sides of the stope in the embodiment of the present invention;

[0030] Figure 3 is a graph showing the relationship between roof pressure concentration and rock drilling chamber width in an embodiment of the present invention;

[0031] Figure 4 is a graph showing the relationship between the roof pressure concentration and the height of the rock drilling chamber in an embodiment of the present invention;

[0032] Figure 5 is a graph showing the relationship between top plate pressure concentration and internal friction angle in an embodiment of the present invention;

[0033] Figure 6 is a graph showing the relationship between roof pressure concentration and rock strength coefficient in an embodiment of the present invention;

[0034] Figure 7 is an interaction diagram of the factors affecting the width of the rock drilling chamber and the height of the rock drilling chamber in the embodiment of the present invention;

[0035] Figure 8 is an interaction diagram between factors affecting the width of the rock drilling chamber and the internal friction angle in an embodiment of the present invention;

[0036] Fig. 9 is an interaction diagram between factors affecting the rock drilling chamber width and the roof rock solidity coefficient in an embodiment of the present invention;

[0037] Fig.10 is an interaction diagram between factors affecting the rock drilling chamber height and the internal friction angle in an embodiment of the present invention;

[0038] Fig.11 is an interaction diagram between factors affecting the rock drilling chamber height and the roof rock solidity coefficient in an embodiment of the present invention;

[0039] Fig.12 is an interaction diagram between the factors affecting the internal friction angle and the roof rock strength coefficient in the embodiment of the present invention;

[0040] Fig.13 This is a roof stress cloud diagram of a mining length of 45m in Scheme 1 of the embodiment of the present invention;

[0041] Fig.14 This is a roof stress cloud diagram of a mining length of 60m in Scheme 1 of the embodiment of the present invention;

[0042] Fig.15 This is a roof stress cloud diagram of a mining length of 27m in Scheme 2 of the embodiment of the present invention;

[0043] Fig.16 This is a roof stress cloud diagram of a mining length of 36m in Scheme 2 of the embodiment of the present invention;

[0044] Fig.17 1 is a diagram showing the stress variation of the top plate in scheme 1 and scheme 2 according to the embodiment of the present invention;

[0045] Fig.18 This is a side wall stress cloud diagram of a mining length of 27m in Scheme 1 of the embodiment of the present invention;

[0046] Fig.19 This is a side wall stress cloud diagram of a mining length of 36m in Scheme 1 of the embodiment of the present invention;

[0047] Fig. 20 This is a side wall stress cloud diagram of the mining length of 18m in Scheme 2 in the embodiment of the present invention;

[0048] Fig.21 This is a side wall stress cloud diagram of the mining length of 27m in Scheme 2 of the embodiment of the present invention;

[0049] Fig. 22 It is a diagram of the stress variation of the side wall in scheme 1 and scheme 2 in the embodiment of the present invention;

[0050] Fig.23 This is a cloud diagram of the plastic zone of the roof with a mining length of 36m in Scheme 1 of the embodiment of the present invention;

[0051] Fig.24 This is a cloud diagram of the plastic zone of the roof with a mining length of 45m in Scheme 1 of the embodiment of the present invention;

[0052] Fig.25 This is a cloud diagram of the plastic zone of the roof with a mining length of 27m in Scheme 2 of the embodiment of the present invention;

[0053] Fig.26 This is a cloud diagram of the plastic zone of the roof with a mining length of 36m in Scheme 2 in the embodiment of the present invention;

[0054] Fig. 27 This is a cloud diagram of the plastic zone of the side wall with a mining length of 36m in Scheme 1 of the embodiment of the present invention;

[0055] Fig.28 This is a cloud diagram of the plastic zone of the side wall with a mining length of 45m in Scheme 1 of the embodiment of the present invention;

[0056] Fig.29 This is a cloud diagram of the plastic zone of the side wall with a mining length of 27m in Scheme 2 of the embodiment of the present invention;

[0057] Fig.30 This is a cloud diagram of the plastic zone of the side wall with a mining length of 36m in Scheme 2 in the embodiment of the present invention;

[0058] Fig.31 is a plan view of a rock drilling chamber in a stope according to an embodiment of the present invention;

[0059] In the figure: deformation zone of the rock drilling chamber roof 1, the rock drilling chamber 2, the pillar 3 left in the rock drilling chamber, the pillar 4, the mine room 5, and the slip angle 6 of the surrounding rock. DETAILED DESCRIPTION

[0060] In order to make the purpose, technical solutions and advantages of the invention implementation cases clearer, the technical solutions in the implementation cases of the present invention will be clearly and completely described below in conjunction with the drawings in the implementation cases. Obviously, the implementation cases described are only a small part of the implementation cases of the present invention, rather than all the implementation cases. Based on the implementation cases in the present invention, all other implementation cases obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0061] A method for analyzing the influence of pillars in a large-section rock drilling chamber on roof stability comprises the following steps:

[0062] (1) The calculation model of the stability of the pillars in the rock drilling chamber of the subsequent mining field in the construction stage is constructed based on the actual mining field, the Protz ground pressure theory and the Kastner equation. The main influencing factors of the stability of the pillars in the rock drilling chamber are determined, including: the width of the rock drilling chamber, the height of the rock drilling chamber, the internal friction angle of the surrounding rocks on both sides of the rock drilling chamber, and the rock strength coefficient of the roof of the rock drilling chamber;

[0063] (2) Based on the actual situation of the mining site and the stability calculation model, the influence of different influencing factors on the pressure concentration of the chamber roof is analyzed;

[0064] (3) Analysis of the sensitivity and interaction of influencing factors, using the BOX-BEHNKEN response surface design in the response surface methodology to explore the comprehensive impact of influencing factors on the pressure concentration of the top plate of the rock drilling chamber;

[0065] (4) Numerical simulation analysis and verification: A mine chamber model was established using numerical simulation software, and a multi-step mine chamber mining simulation analysis was carried out. The stability of the chamber roof was compared and analyzed under two schemes: leaving no pillars in the chamber and leaving pillars first and then collapsing with the ore body. Based on the analysis results, the parameters of the chamber and the pillars left in the chamber were further optimized.

[0066] In the step (1), assuming that the internal friction angle of the surrounding rocks on both sides of the stope length direction is φ, the slip angle θ of the surrounding rocks is: 45°+φ / 2, and the calculation formula for the span B1 of the natural equilibrium arch of the roof rock is:

[0067] B1=B+2Hctgθ

[0068] Where: B1 is the span of the natural balance arch of the rock in the stope roof, m; B is the width of the rock drilling chamber in the stope, m; H is the height of the stope, m; θ is the slip angle of the surrounding rock, °; φ is the internal friction angle of the surrounding rock, °;

[0069] The calculation formula for the height b1 of the natural equilibrium arch is:

[0070] b1=B1 / (2f)=(B / 2+Hctgθ) / f

[0071] Where: b1 is the height of the natural equilibrium arch, m; B is the width of the rock drilling chamber in the stope, m; H is the height of the stope, m; θ is the slip angle of the surrounding rock, °; f is the solidity coefficient of the roof rock;

[0072] The stress range of the pillar is the gravity of the roof rock mass, which has little to do with the rock mass outside the plastic zone. Therefore, the rock mass pressure distribution in the upper plastic zone can be approximately regarded as a uniform state. The calculation formula for the roof pressure concentration is:

[0073] q d =γgb1B1

[0074] Where: q d is the concentration of roof pressure in the mining area, N / m; γ is the weight of the ore, kg / m3; g is the acceleration of gravity, N / kg; b1 is the height of the natural equilibrium arch, m; B1 is the span of the natural equilibrium arch of the rock in the mining area roof, m;

[0075] The formula for calculating the roof pressure over the entire mining space span is:

[0076] Q d =q d L

[0077] Where: Q d is the roof pressure of the mining area, N; q d is the roof pressure concentration in the mining area, N / m; L is the length of the drilling chamber, m.

[0078] In the step (2), the influence of different influencing factors on the pressure concentration of the chamber roof includes the influence of the width of the drilling chamber on the pressure concentration of the chamber roof, the influence of the height of the drilling chamber on the pressure concentration of the chamber roof, the influence of the internal friction angle of the surrounding rock on both sides of the drilling chamber on the pressure concentration of the chamber roof, and the influence of the rock strength coefficient of the drilling chamber roof on the pressure concentration of the chamber roof.

[0079] In the step (3), the comprehensive influence of the influencing factors on the pressure concentration of the top plate of the drilling chamber includes the comprehensive influence of the width of the drilling chamber and the height of the drilling chamber on the pressure concentration of the top plate of the chamber, the comprehensive influence of the width of the drilling chamber and the internal friction angle of the surrounding rock on both sides of the drilling chamber on the pressure concentration of the top plate of the chamber, the comprehensive influence of the width of the drilling chamber and the rock strength coefficient of the top plate of the drilling chamber on the pressure concentration of the top plate of the chamber, the comprehensive influence of the height of the drilling chamber and the internal friction angle of the surrounding rock on both sides of the drilling chamber on the pressure concentration of the top plate of the chamber, and the comprehensive influence of the internal friction angle of the surrounding rock on both sides of the drilling chamber and the rock strength coefficient of the top plate of the drilling chamber on the pressure concentration of the top plate of the chamber.

[0080] In the step (4), the comparative analysis includes comparative analysis of top plate stress, comparative analysis of side wall stress, comparative analysis of top plate plastic zone and comparative analysis of side wall plastic zone under two schemes.

[0081] In practical application, the present invention comprises the following steps:

[0082] The first step is to construct a calculation model for the stability of the pillars in the rock drilling chambers of the subsequent mining field. Combined with the actual mining field, the calculation model for the stability of the pillars in the rock drilling chambers of the subsequent mining field is constructed based on the Protz ground pressure theory and the Kastner equation; the main influencing factors of the stability of the pillars in the rock drilling chambers are determined, including: the width of the rock drilling chamber, the height of the rock drilling chamber, the internal friction angle of the surrounding rocks on both sides of the rock drilling chamber, and the solidity coefficient of the rock on the top of the rock drilling chamber.

[0083] During the excavation of the ore body to form a chamber, the stress of the roof is redistributed. The pillars left in the chamber are subjected to the pressure exerted by the overlying rock strata, playing the main bearing capacity, and working together with the ore rocks on both sides of the chamber to balance the stress of the chamber roof, forming a small pressure-free arch to ensure the stability of the roof. When the pillars left in the chamber collapse along with the ore body, the original stress balance system is broken, and the range of the pressure-free arch gradually merges and expands to form a whole, presenting a plastic zone structure. The surrounding rock of the chamber roof relies on the ore rocks on both sides to reach stress balance again, forming a large area of ​​Pusch arch, thereby playing the role of bearing the stress of the surrounding rock in the plastic zone.

[0084] Assume that the internal friction angle of the surrounding rock on both sides of the length direction of the mining area is φ, and the slip angle θ of the surrounding rock is: 45°+φ / 2. The calculation formula for the span B1 of the natural balance arch of the roof rock is:

[0085] B1=B+2Hctgθ (1)

[0086] Where: B1 is the span of the natural balance arch of the rock in the mining area roof, m; B is the width of the rock drilling chamber in the mining area, m; H is the height of the mining area, m; θ is the slip angle of the surrounding rock, °; φ is the internal friction angle of the surrounding rock, °.

[0087] The calculation formula for the height b1 of the natural equilibrium arch is:

[0088] b1=B1 / (2f)=(B / 2+Hctgθ) / f (2)

[0089] Where: b1 is the height of the natural equilibrium arch, m; B is the width of the rock drilling chamber in the mining area, m; H is the height of the mining area, m; θ is the slip angle of the surrounding rock, °; f is the strength coefficient of the roof rock.

[0090] The stress range of the pillar is the gravity of the roof rock mass, which has little to do with the rock mass outside the plastic zone. Therefore, the rock mass pressure distribution in the upper plastic zone can be approximately regarded as a uniform state. The calculation formula for the roof pressure concentration is:

[0091] q d =γgb1B1 (3)

[0092] Where: q d is the pressure concentration of the mine roof, N / m; γ is the weight of the ore, kg / m3; g is the acceleration of gravity, N / kg; b1 is the height of the natural equilibrium arch, m; B1 is the span of the natural equilibrium arch of the mine roof rock, m.

[0093] The formula for calculating the roof pressure over the entire mining space span is:

[0094] Q d =q d L (4)

[0095] Where: Q d is the roof pressure of the mining area, N; q d is the roof pressure concentration in the mining area, N / m; L is the length of the drilling chamber, m.

[0096] The second step is to analyze the influence of different factors on the stability of the rock drilling chamber roof. Combined with the actual situation of the mining site, according to the stability calculation model, the influence of different rock drilling chamber widths, rock drilling chamber heights, internal friction angles of surrounding rocks on both sides of the rock drilling chamber, and the strength coefficient of the rock on the rock drilling chamber roof on the pressure concentration of the chamber roof is analyzed.

[0097] The third step is to analyze the sensitivity and interaction of influencing factors. The BOX-BEHNKEN response surface design in the response surface method is used to explore the comprehensive influence of variables such as the width of the rock drilling chamber, the height of the rock drilling chamber, the internal friction angle of the surrounding rock on both sides of the rock drilling chamber, and the solidity coefficient of the rock on the top of the rock drilling chamber on the pressure concentration of the top of the rock drilling chamber.

[0098] The fourth step is numerical simulation analysis and verification. The mine model is established using numerical simulation software, and a multi-step mine mining simulation analysis is carried out to compare the stability of the rock drilling chamber roof under two schemes: leaving no pillars in the rock drilling chamber and leaving pillars first and then collapsing with the ore body. This includes comparative analysis of roof stress, side wall stress, roof plastic zone, and side wall plastic zone under the two schemes. Based on the results, the parameters of the rock drilling chamber and the pillars left in the chamber are further optimized.

[0099] Example:

[0100] The ore body of Zhongguan Iron Mine is a gently inclined and extremely thick ore body. Most of the ore rocks have developed joints and fissures, and the overall stability is poor. The southern area of ​​Zhongguan Iron Mine is the first mining section of the mine. The mining method adopted is the large-diameter deep hole rock drilling and lateral caving stage empty field and subsequent filling mining method. The ore blocks are arranged vertically to the ore body. The ore blocks are 60m high, 15m wide, and 50m to 60m long. The rock drilling chamber is arranged on the top of the mine room. The rock drilling chamber is 50m to 60m long, 15m wide, and 4m high. In order to ensure the safety of rock drilling operations, a strip ore pillar with a width of 3m is left in the chamber (see Fig.30 ). After the rock drilling and charging work is completed, the strip pillars left in the chamber collapse together with the ore body of the mine room for mining. The first leaving of the pillars in the rock drilling chamber and then mining has a great impact on the stability of its roof. Therefore, it is necessary to clarify the reasonable parameters of the rock drilling chamber and the parameters of the pillars left in the chamber to improve the stability of the mine roof and ensure safe operation and efficient mining.

[0101] (1) Construction stage: The calculation model of the stability of the rock drilling chamber pillars in the subsequent mining field. Combined with the actual mining field, the calculation model of the stability of the rock drilling chamber pillars was constructed based on the Protz ground pressure theory and the Kastner equation.

[0102] During the excavation of the ore body to form a chamber, the stress of the roof is redistributed. The pillars left in the chamber are subjected to the pressure exerted by the overlying rock strata, playing the main bearing capacity, and working together with the ore rocks on both sides of the chamber to balance the stress of the chamber roof, forming a small pressure-free arch to ensure the stability of the roof. When the pillars left in the chamber collapse along with the ore body, the original stress balance system is broken, and the range of the pressure-free arch gradually merges and expands to form a whole, presenting a plastic zone structure. The surrounding rock of the chamber roof relies on the ore rocks on both sides to reach stress balance again, forming a large area of ​​Pusch arch, thereby playing the role of bearing the stress of the surrounding rock in the plastic zone.

[0103] Assume that the internal friction angle of the surrounding rock on both sides of the length direction of the mining area is φ, and the slip angle θ of the surrounding rock is: 45°+φ / 2. The calculation formula for the span B1 of the natural balance arch of the roof rock is:

[0104] B1=B+2Hctgθ (1)

[0105] Where: B1 is the span of the natural balance arch of the rock in the mining area roof, m; B is the width of the rock drilling chamber in the mining area, m; H is the height of the mining area, m; θ is the slip angle of the surrounding rock, °; φ is the internal friction angle of the surrounding rock, °.

[0106] The calculation formula for the height b1 of the natural equilibrium arch is:

[0107] b1=B1 / (2f)=(B / 2+Hctgθ) / f (2)

[0108] Where: b1 is the height of the natural equilibrium arch, m; B is the width of the rock drilling chamber in the mining area, m; H is the height of the mining area, m; θ is the slip angle of the surrounding rock, °; f is the strength coefficient of the roof rock.

[0109] The stress range of the pillar is the gravity of the roof rock mass, which has little to do with the rock mass outside the plastic zone. Therefore, the rock mass pressure distribution in the upper plastic zone can be approximately regarded as a uniform state. The calculation formula for the roof pressure concentration is:

[0110] q d =γgb1B1 (3)

[0111] Where: q d is the pressure concentration of the mine roof, N / m; γ is the weight of the ore, kg / m3; g is the acceleration of gravity, N / kg; b1 is the height of the natural equilibrium arch, m; B1 is the span of the natural equilibrium arch of the mine roof rock, m.

[0112] The formula for calculating the roof pressure over the entire mining space span is:

[0113] Q d =q dL (4)

[0114] Where: Q d is the roof pressure of the mining area, N; q d is the roof pressure concentration in the mining area, N / m; L is the length of the drilling chamber, m.

[0115] The main influencing factors for determining the stability of the pillars in the rock drilling chamber include: the width of the rock drilling chamber, the height of the rock drilling chamber, the internal friction angle of the surrounding rocks on both sides of the rock drilling chamber, and the solidity coefficient of the rock on the top of the rock drilling chamber.

[0116] (2) Analysis of the influence of different factors on the stability of the rock drilling chamber roof. Combined with the actual situation of the mining site, according to the stability calculation model, the influence of different rock drilling chamber widths, rock drilling chamber heights, internal friction angles of the surrounding rocks on both sides of the rock drilling chamber, and the strength coefficient of the rock on the rock drilling chamber roof on the rock drilling chamber roof pressure concentration was analyzed. Among them, the ore weight is taken as 3.9kg / m 3 , the acceleration due to gravity is 9.8N / kg.

[0117] 1) Influence of drilling chamber width on roof pressure concentration

[0118] Figure 3 is the relationship between the roof pressure concentration and the width of the rock drilling chamber. It can be seen from the figure that the roof pressure concentration gradually increases with the increase of the width of the rock drilling chamber, and the two are in an exponential relationship. According to the design size of the rock drilling chamber in the mine, a strip pillar with a width of 3m is left in the chamber, and the width of the rock drilling chamber is 6m. With the backward mining of the ore body, the strip pillar collapses with the ore body, and the width of the rock drilling chamber becomes 15m. According to the calculation results, when the width of the rock drilling chamber is 6m, the roof pressure concentration is 1313.96KN / m, and the roof stress is 0.13MPa; when the width of the rock drilling chamber is 15m, the roof pressure concentration is 4674.22KN / m, and the roof stress is 0.24MPa.

[0119] 2) The influence of the drilling chamber height on the roof pressure concentration

[0120] Figure 4 The figure shows the relationship between the roof pressure concentration and the height of the rock drilling chamber. It can be seen from the figure that the roof pressure concentration gradually increases with the increase of the height of the rock drilling chamber, and the two are approximately linear. When the width of the rock drilling chamber is 6m, the roof pressure concentration changes with the increase of the height of the rock drilling chamber in the range of 1000KN / m~1500KN / m, and the roof stress changes in the range of 0.11MPa~0.13MPa; when the width of the rock drilling chamber is 15m, the roof pressure concentration changes with the increase of the height of the rock drilling chamber in the range of 4000KN / m~5000KN / m, and the roof stress changes in the range of 0.23MPa~0.25MPa.

[0121] 3) Influence of the internal friction angle of the surrounding rock on both sides of the drilling chamber on the roof pressure concentration

[0122] Figure 5 The figure shows the relationship between the roof pressure concentration and the internal friction angle of the surrounding rock on both sides of the rock drilling chamber. It can be seen from the figure that the roof pressure concentration gradually decreases with the increase of the internal friction angle. When the width of the rock drilling chamber is 6m, the roof pressure concentration varies with the increase of the internal friction angle in the range of 1400KN / m~800KN / m, and the roof stress varies in the range of 0.13MPa~0.10MPa; when the width of the rock drilling chamber is 15m, the roof pressure concentration varies with the increase of the internal friction angle in the range of 4700KN / m~3500KN / m, and the roof stress varies in the range of 0.24MPa~0.22MPa.

[0123] 4) Influence of rock strength coefficient of the drilling chamber roof on the roof pressure concentration

[0124] Figure 6 Figure 1 is the relationship between the roof pressure concentration and the rock strength coefficient of the roof of the rock drilling chamber. It can be seen from the figure that the roof pressure concentration gradually decreases with the increase of the roof rock strength coefficient. When the width of the rock drilling chamber is 6m, the roof pressure concentration changes with the increase of the roof rock strength coefficient in the range of 2000KN / m~394KN / m, and the roof stress changes in the range of 0.19MPa~0.04MPa; when the width of the rock drilling chamber is 15m, the roof pressure concentration changes with the increase of the roof rock strength coefficient in the range of 7000KN / m~1400KN / m, and the roof stress changes in the range of 0.37MPa~0.07MPa.

[0125] From the above analysis, it can be seen that the strip pillars left in the rock drilling chamber will cause the roof pressure to increase rapidly and the increase is large when the ore body is mined, which has a great impact on the stability of the rock drilling chamber roof.

[0126] (3) Analysis of sensitivity and interaction of influencing factors. The BOX-BEHNKEN response surface design in the response surface method was used to explore the comprehensive effects of variables such as the width of the rock drilling chamber, the height of the rock drilling chamber, the internal friction angle of the surrounding rock on both sides of the rock drilling chamber, and the rock strength coefficient of the rock drilling chamber roof on the pressure concentration of the rock drilling chamber roof.

[0127] Figure 7 to Figure 12 The calculation results show that the order of sensitivity of roof pressure concentration to various factors is: rock strength coefficient of the roof of the rock drilling chamber > width of the rock drilling chamber > internal friction angle of the surrounding rock on both sides of the rock drilling chamber > height of the rock drilling chamber. Among them, the influence of the roof rock strength coefficient and the width of the rock drilling chamber on the roof pressure concentration is extremely significant, and the influence of the internal friction angle of the surrounding rock on both sides of the rock drilling chamber and the height of the rock drilling chamber on the roof pressure concentration is not significant. The interaction between the factors is shown in Fig.13The interaction between the width of the drilling chamber and the strength coefficient of the roof rock is extremely significant, the interaction between the internal friction angle of the surrounding rock on both sides of the drilling chamber and the strength coefficient of the roof rock is significant, the interaction between the width and height of the drilling chamber, the width of the drilling chamber and the internal friction angle of the surrounding rock on both sides of the drilling chamber, and the height of the drilling chamber and the strength coefficient of the roof rock are not significant, and the interaction between the height of the drilling chamber and the internal friction angle of the surrounding rock on both sides of the drilling chamber is extremely insignificant.

[0128] (4) Numerical simulation analysis and verification. Using FLAC3D numerical simulation software, a mine model with a length of 60m, a height of 60m, and a width of 15m was established. A multi-step mine mining simulation analysis was carried out to compare the stability of the rock drilling chamber roof under two schemes: no pillars left in the rock drilling chamber (Scheme 1) and leaving pillars first and then collapsing with the ore body (Scheme 2). This includes comparative analysis of roof stress, side wall stress, roof plastic zone, and side wall plastic zone under the two schemes. Based on the results, the parameters of the rock drilling chamber and the pillars left in the chamber are further optimized.

[0129] 1) Comparative analysis of roof stress. Figure 13 to Figure 16 They are the top plate stress cloud diagrams of Scheme 1 and Scheme 2 respectively. Fig.17 The change characteristics of compressive stress and tensile stress in the top plate of Scheme 1 and Scheme 2. Figure 13-14 and Fig.17 It can be seen that when no pillars are left in the rock drilling chamber, when the mining length of the mine chamber is less than 45m, as the mining of the mine chamber proceeds, the compressive stress of the roof changes slightly, and the tensile stress decreases significantly when the mining length increases from 18m to 27m, and then remains within a certain range, indicating that when no pillars are left, the roof of the rock drilling chamber can remain stable when the mining length is less than 45m. When the mining length exceeds 45m, the compressive stress of the roof suddenly decreases, the stability weakens, and the probability of collapse increases.

[0130] Combination Figure 15-16 and Fig.17 It can be seen that when the rock drilling chamber is first left with a pillar and then the ore body is collapsed together, as the mining length of the mine room increases, when the excavation is below 27m, the roof stability is good, the tensile and compressive stresses increase, and after the mining length increases from 27m to 36m, the tensile and compressive stresses both decrease, indicating that the roof has a large stress concentration and release phenomenon before and after the support of the pillar, that is, after the pillar is excavated, the stability of the roof can no longer be maintained, the stress is redistributed, and the risk of roof instability and falling is significantly increased.

[0131] From the above analysis, it can be seen that when the mining length of the mine room is less than 27m, the roof stability of Scheme 1 and Scheme 2 is better; when the length is 27m~45m, the risk of roof instability is greater in Scheme 2, which first leaves a pillar and then collapses with the ore body with the pillar; when the length exceeds 45m, both Scheme 1 and Scheme 2 have the risk of roof instability, and Scheme 2 has a greater risk.

[0132] 2) Comparative analysis of side stress. Figure 18 to Figure 21 These are the stress cloud diagrams of the side walls after mining in Scheme 1 and Scheme 2. Fig. 22 The variation characteristics of the side tensile stress of Scheme 1 and Scheme 2 are shown in Figure 2. Figure 18-19 and Fig. 22 It can be seen that when no pillars are left in the rock drilling chamber, the tensile stress distribution of the side walls gradually extends to both sides as the excavation proceeds. When the mining length exceeds 27m, the tensile stress of the side walls increases with a large variation range, indicating that the side walls are at risk of shear failure at this time.

[0133] Combination Figure 20-21 and Fig. 22 It can be seen that when the ore pillars are left in the drilling chamber first and then the ore body is collapsed together, the tensile stress of the side wall continues to increase with the increase of mining length, and when the mining length increases from 18m to 27m, the tensile stress of the side wall decreases significantly, indicating that the stress concentration phenomenon of the side wall is significant, and there is a risk of shear collapse failure of the side wall.

[0134] Based on the above results, it can be seen that when pillars are left in the rock drilling chamber before the ore body is collapsed, the stability of the side walls will be greatly hidden dangers, the stress concentration phenomenon will be significant, and the risk of instability and damage of the side walls will be higher than when no pillars are left in the rock drilling chamber.

[0135] 3) Comparative analysis of roof plastic zone. Figure 23 to Figure 26 The plastic zone cloud diagrams of the top plate of Scheme 1 and Scheme 2 are shown respectively. Figure 23 to Figure 26 It can be seen that when no pillars are left in the rock drilling chamber, as the mining proceeds, when the mining length is less than 36m, the plastic zone of the roof does not change much, and shear failure is mainly at the free surface. When the mining length reaches 45m, the shear failure area of ​​the roof increases, and there is a tendency to penetrate, and tensile failure occurs at the same time, and the stability of the roof is weakened. Figure 25-26 It shows that when a pillar is left in the drilling chamber and then collapses with the ore body, the roof will suffer from mixed shear and tensile failure after the mining length is greater than 27m. At this time, when some of the pillars are mined, the roof is affected by stress concentration, inducing instability and collapse, and there is a great risk of instability for the roof.

[0136] 4) Comparative analysis of the plastic zone of the side walls. Figure 27 to Figure 30 These are the cloud diagrams of the plastic zone of the sidewalls of Scheme 1 and Scheme 2 respectively. Figure 27-28It can be seen that when no pillars are left in the rock drilling chamber, when the mining length is greater than 36m, the side walls are mainly damaged by shear, and the shear area gradually increases with the increase of mining length, indicating that due to the increase in the exposed area of ​​the side walls after excavation, the side walls can no longer maintain stability under the shear action, and the side walls show through-type shear slip instability. Figure 29-30 It can be seen that when the ore pillars were first left in the drilling chamber and then collapsed along with the ore body, when the mining length reached 27m, a large-scale shear damage area appeared in the side wall. When the mining length continued to increase to 36m, the side wall was damaged due to the shear effect, and the shear area suddenly decreased, indicating that the ore pillars left in the early stage improved the stability of the side wall to a certain extent, but when they collapsed along with the ore body, the stress of the side wall suddenly increased, resulting in large-scale shear damage after continued excavation and serious instability of the side wall.

[0137] 5) According to the above analysis results, it can be seen that when a pillar is first left in the rock drilling chamber and then collapses with the ore body, it will cause stress concentration and multiple redistribution of the roof and side walls. When the pillar is left and collapses with the ore body, there is an accelerated stress release process in the roof and side walls, and the risk of instability of the roof and side walls is relatively high; when no pillar is left in the rock drilling chamber, the stress release and redistribution of the roof and side walls are relatively stable during the mining process of the mine, and the destruction time is relatively delayed.

[0138] 6) Based on the above analysis results, mining recommendations are put forward. Recommendation 1: In order to improve mining efficiency, when the stability of the ore rock is medium or above, when the large-diameter deep hole mining method is adopted, it is necessary to pre-support the roof that is in contact with the pillars left in the rock drilling chamber to ensure the stability of the large-section rock drilling chamber during the ore falling process. It is recommended that the width of the rock drilling chamber be 15m, the length ≤50m, and the height be 4m. After leaving a strip pillar with a width of 3 to 4m in the chamber, it will collapse with the ore body for mining. In order to ensure the stability of the roof and the safety of the operation, the pre-control top support of the roof of the rock drilling chamber should be strengthened during the implementation process. Recommendation 2: When the stability of the ore rock is unstable, it is beneficial to the stability of the roof to appropriately reduce the width of the rock drilling chamber and not leave pillars in the chamber.

[0139] In summary, the present invention combines the actual situation of the mining field, and constructs a calculation model for the stability of the pillars in the rock drilling chamber based on the Protz ground pressure theory and the Kastner equation. The calculation model is more in line with reality, and analyzes the stability of the pillars in the rock drilling chamber under the influence of various influencing factors; and uses the surface design method to carry out sensitivity and interaction analysis of influencing factors, and studies the comprehensive influence of influencing variables on the pressure concentration of the roof of the rock drilling chamber; at the same time, numerical simulation software is used to carry out numerical simulation analysis and verification in the multi-step mining process. The verification results show that the research results can further optimize the size of the rock drilling chamber and the pillars left in the chamber, which has engineering guidance significance. The present invention provides a new idea for the analysis method of the influence of the pillars of the rock drilling chamber on the stability of the roof in the subsequent stage of the mining field, provides a theoretical basis for the optimization of the size of the rock drilling chamber and the pillars left in the chamber, and guides the safe and efficient production of mines.

Claims

1. A method for analyzing the influence of large-section rock drilling chamber pillars on roof stability, characterized in that The following steps are involved: (1) The calculation model of the stability of the rock drilling chamber pillars in the subsequent mining field is constructed in the construction stage. Combined with the actual mining field, the calculation model of the stability of the rock drilling chamber pillars in the subsequent mining field is constructed based on the Protz ground pressure theory and the Kastner equation; The main factors affecting the stability of the pillars in the rock drilling chamber include: the width of the rock drilling chamber, the height of the rock drilling chamber, the internal friction angle of the surrounding rocks on both sides of the rock drilling chamber, and the rock strength coefficient of the rock drilling chamber roof; (2) Based on the actual situation of the mining site and the stability calculation model, the influence of different influencing factors on the pressure concentration of the chamber roof is analyzed; (3) Analysis of the sensitivity and interaction of influencing factors, using the BOX-BEHNKEN response surface design in the response surface methodology to explore the comprehensive impact of influencing factors on the pressure concentration of the top plate of the rock drilling chamber; (4) Numerical simulation analysis and verification: A mine chamber model was established using numerical simulation software, and a multi-step mine chamber mining simulation analysis was carried out. The stability of the chamber roof was compared and analyzed under two schemes: leaving no pillars in the chamber and leaving pillars first and then collapsing with the ore body. Based on the analysis results, the parameters of the chamber and the pillars left in the chamber were further optimized.

2. The method for analyzing the influence of pillars in a large-section rock drilling chamber on roof stability according to claim 1, characterized in that: In the step (1), assuming that the internal friction angle of the surrounding rocks on both sides of the stope length direction is φ, the slip angle θ of the surrounding rocks is: 45°+φ / 2, and the calculation formula for the span B1 of the natural equilibrium arch of the roof rock is: B1=B+2Hctgθ Where: B1 is the span of the natural balance arch of the rock in the stope roof, m; B is the width of the rock drilling chamber in the stope, m; H is the height of the stope, m; θ is the slip angle of the surrounding rock, °; φ is the internal friction angle of the surrounding rock, °; The calculation formula for the height b1 of the natural equilibrium arch is: b1=B1 / (2f)=(B / 2+Hctgθ) / f Where: b1 is the height of the natural equilibrium arch, m; B is the width of the rock drilling chamber in the stope, m; H is the height of the stope, m; θ is the slip angle of the surrounding rock, °; f is the solidity coefficient of the roof rock; The stress range of the pillar is the gravity of the roof rock mass, which has little to do with the rock mass outside the plastic zone. Therefore, the rock mass pressure distribution in the upper plastic zone can be approximately regarded as a uniform state. The calculation formula for the roof pressure concentration is: q d =γgb1B1 Where: qd is the concentration of roof pressure in the mining area, N / m; γ is the weight of the ore, kg / m3; g is the acceleration of gravity, N / kg; b1 is the height of the natural equilibrium arch, m; B1 is the span of the natural equilibrium arch of the rock in the mining area roof, m; The formula for calculating the roof pressure over the entire mining space span is: Q d =q d L Where: Q d is the roof pressure of the mining area, N; q d is the roof pressure concentration in the mining area, N / m; L is the length of the drilling chamber, m.

3. The method for analyzing the influence of pillars on roof stability in a large-section rock drilling chamber according to claim 1, characterized in that: In the step (2), the influence of different influencing factors on the pressure concentration of the chamber roof includes the influence of the width of the drilling chamber on the pressure concentration of the chamber roof, the influence of the height of the drilling chamber on the pressure concentration of the chamber roof, the influence of the internal friction angle of the surrounding rock on both sides of the drilling chamber on the pressure concentration of the chamber roof, and the influence of the rock strength coefficient of the drilling chamber roof on the pressure concentration of the chamber roof.

4. The method for analyzing the influence of pillars in a large-section rock drilling chamber on roof stability according to claim 1, characterized in that: In the step (3), the comprehensive influence of the influencing factors on the pressure concentration of the top plate of the drilling chamber includes the comprehensive influence of the width of the drilling chamber and the height of the drilling chamber on the pressure concentration of the top plate of the chamber, the comprehensive influence of the width of the drilling chamber and the internal friction angle of the surrounding rock on both sides of the drilling chamber on the pressure concentration of the top plate of the chamber, the comprehensive influence of the width of the drilling chamber and the rock strength coefficient of the top plate of the drilling chamber on the pressure concentration of the top plate of the chamber, the comprehensive influence of the height of the drilling chamber and the internal friction angle of the surrounding rock on both sides of the drilling chamber on the pressure concentration of the top plate of the chamber, and the comprehensive influence of the internal friction angle of the surrounding rock on both sides of the drilling chamber and the rock strength coefficient of the top plate of the drilling chamber on the pressure concentration of the top plate of the chamber.

5. The method for analyzing the influence of pillars in a large-section rock drilling chamber on roof stability according to claim 1, characterized in that: In the step (4), the comparative analysis includes comparative analysis of top plate stress, comparative analysis of side wall stress, comparative analysis of top plate plastic zone and comparative analysis of side wall plastic zone under two schemes.

Images