Perforating charge size selection method for coal mine dynamic and static coupling blasting method

Abstract

The invention discloses a perforating charge size selection method for a coal mine dynamic and static coupling blasting method, and belongs to the technical field of coal mining blasting. Firstly, a coal seam three-dimensional fracture network model is constructed by adopting drilling rock core sampling and geological radar scanning, and geological parameters such as compressive strength and fracture structures of a coal seam are obtained; then estimating the required blasting energy based on the blasting requirement of the coal mine, and defining a perforating bullet model and a jet velocity formula; the optimal perforating bullet size is finally selected by estimating the critical penetration depth and the stress field of blasting force transmission and combining factors such as target blasting force and dynamic compressive strength, so that the optimal blasting effect is achieved. The precision and efficiency of dynamic and static coupling blasting of the coal mine are effectively improved, and unnecessary coal seam damage and resource waste are reduced.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of coal mining blasting, and particularly relates to a method for selecting the size of a perforating bomb in a coal mine dynamic-static coupling blasting method. BACKGROUND

[0002] In the process of coal mining, dynamic-static coupling blasting technology is an important means to improve blasting efficiency and reduce mining cost. As a commonly used tool in blasting, the size of the perforating bomb has a decisive influence on the blasting effect. However, the traditional method for selecting the size of the perforating bomb lacks systematic analysis of geological parameters and blasting requirements, resulting in unstable blasting effect. In order to optimize the blasting effect, it is necessary to consider many factors such as the geological characteristics of the coal seam, the blasting energy requirement and the jet flow dynamics.

[0003] In recent years, many scholars have explored the selection of the size of the perforating bomb, and based on different mathematical and mechanical models, some methods for selecting the size of the perforating bomb have been proposed. However, the current related theories are still not perfect, and the size of the perforating bomb cannot be accurately selected.

[0004] Therefore, there is an urgent need for a method for accurately selecting the size of the perforating bomb. SUMMARY

[0005] In order to achieve the above purpose, the present application adopts the following technical solutions:

[0006] A method for selecting the size of a perforating bomb in a coal mine dynamic-static coupling blasting method, comprising the following steps:

[0007] S1, using drilling core sampling and geological radar scanning of the coal seam to construct a three-dimensional fracture network model of the coal seam, obtaining the geological conditions of the mine, and measuring the fracture fractal dimension D f and the permeability K p ;

[0008] The fracture fractal dimension D f is measured by box counting method, and the calculation method of the permeability K p :

[0009]

[0010] In the formula, Q is the gas flow, m 3 / s; μ is the dynamic viscosity of the gas, Pa·s; L is the core length m; A is the core cross-sectional area m 2 ; P1 is the inlet pressure Pa, P2 is the outlet pressure Pa; P atm is the atmospheric pressure, P atm = 101325 Pa;

[0011] S2, according to the blasting requirements of coal mining, obtaining the required blasting energy Eb ; define the blasting energy E b The formula is as follows:

[0012] E b =∫ V [P0e -βt +ασ d (t)]·η(K P ,D f )dV

[0013] In the formula, E b is the blasting energy J; P0 is the initial pressure of the blasting wave Pa; β is the pressure attenuation coefficient s -1 ; σ d (t) is the dynamic stress component Pa; α is the dynamic stress coupling coefficient, calibrated by experiment, and usually takes a value range of 0.5-1.2; V is the volume to be blasted; η is the energy efficiency factor;

[0014] The energy efficiency factor η is defined as follows:

[0015]

[0016] Wherein, K p is the seepage rate, K ref is the reference permeability;

[0017] S3, define the perforating bomb model, define the jet velocity v j Formula;

[0018] The perforating bomb DP36RDX25 model is defined as the jet model;

[0019] The mass ratio of the liner to the explosive needs to meet certain conditions, i.e. less than 0.3; the calculation method of the mass ratio of the liner to the explosive is as follows:

[0020]

[0021] In the formula, δ is the average thickness of the liner, mm; ρ c is the density of the liner material, kg / m 3 ; D is the detonation velocity of the explosive, m / s; D0 is the reference detonation velocity, m / s; h e is the charge height, mm; ρ e is the density of the explosive, kg / m 3 ;

[0022] The formula of the jet velocity v j is as follows:

[0023]

[0024] In the formula, δ is the average thickness of the liner, mm; ω is the half-cone angle of the liner, °; dc is the average height of explosive, mm; v c is the Poisson's ratio;

[0025] S4, estimate the critical penetration depth L c ;

[0026] Define the critical penetration depth L c , the formula is as follows:

[0027]

[0028] In the formula, L c is the critical penetration depth m; m j is the jet mass kg; v j is the jet velocity m / s; θ is the cone angle of the shaped charge °; v c is the Poisson's ratio of coal, generally 0.2-0.35; E c is the elastic modulus Pa; ρ m is the density of coal kg / m 3 ; K is the jet fracture correction coefficient, that is, dimensionless; σ y is the dynamic compressive strength Pa; A j is the jet cross-sectional area m 2 ; v s is the longitudinal wave speed of coal m / s;

[0029] In which, the jet mass m j is defined as follows:

[0030] m j = η p · ρ j · π(d j / 2) 2 L j

[0031] In the formula, η p is the jet participation coefficient, L j is the jet length m; d j is the jet diameter m; ρ j is the density of jet material kg / m 3 ;

[0032] The jet fracture correction coefficient K is determined by high-speed photography test:

[0033] L / d j >8 is continuous jet: K=0.8-1.2;

[0034] L / d j <5 is broken jet: K=1.2-2.0;

[0035] Define the jet cross-sectional area where d j is the jet diameter, m;

[0036] S5, estimating the stress field of blasting force propagation;

[0037] If the blasting force propagates along the coal seam during blasting, the calculation method of the stress field of blasting force propagation is:

[0038]

[0039] where x is the radial distance from the blasting center, m;

[0040] t0 is the reference time, s;

[0041] σ0 is the initial stress amplitude, Pa, ζ is the fitting coefficient, Q is the charge amount kg, r0 is the charge radius m;

[0042] Γ is the geological deterioration factor, dimensionless, D f is the fracture fractal dimension, K p is the seepage rate, K ref is the reference permeability;

[0043] Ψ is the elastic wave propagation term, m 2 / s 2 , γ is the empirical fitting coefficient, E c is the elastic modulus Pa, ρ m is the medium density kg / m 3 ;

[0044] Φ is the viscoplastic attenuation term, dimensionless, σ y is the dynamic compressive strength Pa, ρ m is the rock density kg / m 3 , v0 is the reference velocity m / s;

[0045] λ is the time attenuation coefficient, s -1 ;

[0046] Δε p is the plastic strain damage factor, dimensionless;

[0047] ε cr is the critical failure strain, dimensionless;

[0048] m is the damage index, dimensionless;

[0049] S6, combining the target blasting force F target , the dynamic compressive strength σ y , and the geological correction factor g(D f, K p ) and elastic modulus E c and Poisson's ratio V c , select the appropriate perforating bullet size d optimal ;

[0050] Perforating bullet size d optimal Calculation method:

[0051]

[0052] In the formula, d optimal is the optimal diameter of the perforating bullet m; F target is the target blasting force N; p m is the medium density kg / m 3 ; g(D f , K p ) is the geological correction factor, that is, dimensionless;

[0053] Wherein, the calculation method of the geological correction factor g(D f , K p ):

[0054]

[0055] In the formula, D f is the fracture fractal dimension; K p is the permeability, K ref is the reference permeability.

[0056] Beneficial effects:

[0057] The application provides a coal mine dynamic-static coupling blasting method perforating bullet size selection method, which is used for selecting the perforating bullet size of the coal mine dynamic-static coupling blasting method. First, the drilling core sampling and the geological radar scanning are adopted to construct a coal seam three-dimensional fracture network model, and the geological parameters such as the compressive strength and the fracture structure of the coal seam are obtained. Then, the required blasting energy is estimated based on the blasting requirements of the coal mine, and the perforating bullet model and the jet velocity formula are defined. By estimating the critical penetration depth and the stress field of the blasting force propagation, combined with factors such as the target blasting force and the dynamic compressive strength, the optimal perforating bullet size is finally selected to realize the best blasting effect. The precision and efficiency of the coal mine dynamic-static coupling blasting are effectively improved, unnecessary coal seam damage and resource waste are reduced, the energy consumption in the blasting process is reduced, and the coal mining is more economical, efficient and environmentally friendly. BRIEF DESCRIPTION OF DRAWINGS

[0058] Figure 1 The application is a perforating bullet DP36RDX25 model; DETAILED DESCRIPTION

[0059] The specific embodiments of the present application will be described in detail in this part, the preferred embodiments of the present application are shown in the drawings, the role of the drawings is to supplement the description of the text part with figures, so that people can intuitively and visually understand each technical feature and the overall technical scheme of the present application, but it cannot be understood as a limitation on the protection scope of the present application.

[0060] In the description of the present application, it should be understood that the orientation description, such as the orientation or position relationship indicated by up, down, front, back, left, right and the like, is based on the orientation or position relationship shown in the drawings, only for the convenience of describing the present application and simplifying the description, and is not intended to indicate or imply that the device or element referred to must have a particular orientation, be constructed and operated in a particular orientation, therefore it cannot be understood as a limitation on the present application.

[0061] In the description of the present application, several meanings are one or more, and multiple meanings are more than two, greater than, less than, more than and the like are not included in the number, above, below, within and the like are included in the number. If it is described as first, second, it is only for the purpose of distinguishing technical features, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of indicated technical features or implicitly indicating the sequence of indicated technical features.

[0062] In the description of the present application, unless otherwise explicitly limited, the words such as setting, installing, connecting and the like should be understood in a broad sense, and the person skilled in the art can reasonably determine the specific meaning of the above words in the present application in combination with the specific content of the technical scheme.

[0063] Example 1

[0064] Reference Figure 1 A coal mine dynamic-static coupling blasting method perforating bullet size selection method, comprising the following steps:

[0065] S1, using drilling core sampling and geological radar scanning coal seam, constructing coal seam three-dimensional fracture network model, obtaining the geological conditions of the mine, and measuring the fracture fractal dimension D f And permeability K p .

[0066] Fracture fractal dimension D f Determined by box counting method, the calculation method of permeability K p :

[0067]

[0068] In the formula, Q is the gas flow m 3 / s; μ is the dynamic viscosity of gas Pa·s; L is the core length m; A is the core cross-sectional area m 2 ; P1 is the inlet pressure Pa, P2 is the outlet pressure Pa; P atmAt atmospheric pressure, P atm =101325Pa;

[0069] In this embodiment, the sampling interval of the borehole core is ≤0.5m, and the frequency of the ground-penetrating radar scan is 100MHz-1GHz, which obtains the geological conditions of the mine, including the thickness of the coal seam, compressive strength, fracture structure, etc.

[0070] In this embodiment, the coal seam thickness of the working face was measured to be 1.5m, and the coal density ρ was... m =1.4g / cm 3 Target blasting depth L target =1.4m, fracture fractal dimension D f =1.82, penetration rate K p =2.3mD, Poisson's ratio v c =0.26, dynamic compressive strength σ y =16MPa.

[0071] S2. Based on the blasting requirements of coal mining, obtain the required blasting energy E. b .

[0072] Define the blast energy E b The formula is as follows:

[0073] E b =∫ V [P0e -βt +ασ d (t)]·η(K P D f )dV

[0074] In the formula, E b P0 is the blast energy (J); P0 is the initial blast wave pressure (Pa); β is the pressure attenuation coefficient (s). -1 ;σ d (t) represents the dynamic stress component Pa; α is the dynamic stress coupling coefficient, which is experimentally calibrated and typically ranges from 0.5 to 1.2; V is the volume to be blasted; η is the energy efficiency factor.

[0075] The energy efficiency factor η is defined as follows:

[0076]

[0077] Among them, K p K is the permeability. ref The baseline penetration rate is used.

[0078] In this embodiment, the explosive type RDX is selected, P0 = 30 GPa, β = 0.005 s. -1 α=0.8, K ref =10mD;

[0079] Volume to be blasted V = 1.5 x π x 0.6 2 = 1.7 m 3 ;

[0080] Efficiency factor

[0081] Blasting energy E b = [30 x 10 9 ·e -0.005×0.1 + 0.8 x 50 x 10 6 ] x 0.60 x 1.7 = 2.15 x 10 10 J.

[0082] S3, define the perforating charge model, define the jet velocity v j formula.

[0083] Define the perforating charge DP36RDX25 model as the jet model.

[0084] The mass ratio of the liner to the explosive needs to meet certain conditions, i.e. less than 0.3; the calculation method of the mass ratio of the liner to the explosive is as follows:

[0085]

[0086] In the formula, δ is the average thickness of the liner, mm; ρ c is the density of the liner material, kg / m 3 ; D is the detonation velocity of the explosive, m / s; D0 is the reference detonation velocity, m / s; h e is the charge height, mm; ρ e is the density of the explosive, kg / m 3 ;

[0087] The formula of the jet velocity v j is as follows:

[0088]

[0089] In the formula, δ is the average thickness of the liner, mm; ω is the half-cone angle of the liner, °; d c is the average height of the explosive, m; v c is the Poisson's ratio.

[0090] In this embodiment, δ = 2.5 mm, h e = 120 mm, ρ c = 8900 kg / m 3 , ρ e = 1800 kg / m 3 , D = 4100 m / s, D0 = 4000 m / s, v c = 0.26, ω = 11.5 °.

[0091] Satisfy the economic constraints.

[0092]

[0093] S4, estimate the critical penetration depth L c .

[0094] Definition of critical penetration depth L c , the formula is as follows:

[0095]

[0096] In the formula, L c is the critical penetration depth m; m j is the jet mass kg; v j is the jet velocity m / s; θ is the cone angle of the shroud °; v c is the Poisson's ratio of coal, generally 0.2-0.35; E c is the elastic modulus Pa; ρ m is the density of coal kg / m 3 ; K is the jet fracture correction coefficient, that is, dimensionless; σ y is the dynamic compressive strength Pa; A j is the jet cross-sectional area m 2 ; v s is the longitudinal wave speed of coal m / s.

[0097] In which, the definition of jet mass m j as follows:

[0098] m j = η p · ρ j · π(d j / 2) 2 L j

[0099] In the formula, η p is the jet participation coefficient, L j is the jet length m; d j is the jet diameter m; ρ j is the density of jet material kg / m 3 .

[0100] Jet fracture correction coefficient K is determined by high-speed photography test:

[0101] L / d j >8 is continuous jet: K=0.8-1.2;

[0102] L / d j <5 is broken jet: K=1.2-2.0;

[0103] Definition of jet cross-sectional area where d j is the jet diameter, m.

[0104] In this engineering case, the liner material is chosen to be copper, p j = 8900 kg / m 3 , d j = 45 mm, L j = 0.3 m. In a typical 45 mm copper liner, 0.1% - 0.5% of the mass at the front end forms a high-speed continuous jet, so take η p = 0.001; the jet mass m j = 0.001 x 8900 x π(0.0225) 2 x 0.3 = 4.25 g; the jet cross-sectional area A The liner cone angle θ = 54°; the dynamic compressive strength σ y = 1.6 x 10 7 Pa; the coal body longitudinal wave speed v s = 1400 m / s; the jet length-diameter ratio L / d j = 6.67, take K = 1.0.

[0105]

[0106] So L c ≈ 1.39 m

[0107] Error (meets the requirement of ≤8%).

[0108] S5, estimate the stress field of blast force propagation;

[0109] If the blast force propagates along the coal seam during blasting, the calculation method of the stress field of blast force propagation is:

[0110]

[0111] where x is the radial distance from the blast center, m;

[0112] t0 is the reference time, s.

[0113] σ0 is the initial stress amplitude, Pa, ζ is the fitting coefficient, Q is the charge mass, kg, r0 is the charge radius, m;

[0114] Γ is the geological deterioration factor, dimensionless, D f is the fracture fractal dimension, K p is the seepage rate, K ref is the reference permeability.

[0115] Ψ is the elastic wave propagation term, m 2 / s 2 , γ is an empirically fitted coefficient, E c is the elastic modulus Pa, ρ m is the medium density kg / m 3 ;

[0116] Φ is the visco-plastic attenuation term, dimensionless, σ y is the dynamic compressive strength Pa, ρ m is the rock mass density kg / m 3 , v0 is the reference velocity m / s;

[0117] λ is the time attenuation coefficient, s -1 ;

[0118] Δε p is the plastic strain damage factor, dimensionless;

[0119] ε cr is the critical failure strain, dimensionless;

[0120] m is the damage exponent, dimensionless.

[0121] In the present embodiment, the reference data are as follows:

[0122] D f = 1.82, K p = 2.3 mD, E c = 2.84 GPa, v c = 0.26, ρ m = 1400 kg / m 3 , σ y = 16 MPa,

[0123] Q = 12 kg, r0 = 0.3 m, x = 1.0 m, t0 = 1 s, t = 2 ms, K ref = 10 mD

[0124] γ = 1.71, v0 = 59.165 m / s, λ = 28.57 s -1 , Δε p = 0.00001, ε cr = 0.031, m = 2.31

[0125] The initial stress amplitude is then

[0126] The geological degradation factor is

[0127] Elastic wave propagation term

[0128] Visco-plastic attenuation term

[0129] Time attenuation coefficient λ = 28.57 s -1 ;

[0130] Damage factor Δε p = 0.00001, ε cr = 0.031, m = 2.31.

[0131] The final stress is predicted as:

[0132]

[0133] Target blasting force inversion: F target = σ × A = 343 × 10 6 × π (1.0) 2 = 1.08 × 10 9 N

[0134] S6, combined with target blasting force F target , dynamic compressive strength σ y , geological correction factor g (D f , K p ) and elastic modulus E c and Poisson's ratio V c , select the appropriate perforating bullet size d optimal ;

[0135] The calculation method of perforating bullet size d optimal :

[0136]

[0137] In the formula, d optimal is the optimal diameter of the perforating bullet m; F target is the target blasting force N; ρ m is the medium density kg / m 3 ; g (D f , K p ) is the geological correction factor, that is, dimensionless;

[0138] Wherein, the calculation method of geological correction factor g (D f , K p ):

[0139]

[0140] In the formula, D f is the fractal dimension of the fracture; K p is the permeability, Kref Reference permeability.

[0141] In this embodiment, the correction function is as follows:

[0142]

[0143] The optimal perforating bullet diameter is:

[0144]

[0145] The above merely describes the preferred embodiments of the present application, and is not intended to limit the technical scope of the present application in any way. Any slight modification, equivalent change, and modification made to the above embodiments according to the technical essence of the present application still falls within the scope of the technical solutions of the present application.

Claims

1. A method for selecting the size of a perforating charge for a coal mine dynamic-static coupling blasting method, characterized in that, The method comprises the following steps: S1, adopt drilling core sampling and geological radar scanning coal seam, construct coal seam three-dimensional fracture network model, get the geological conditions of mine, and determine the fracture fractal dimension D f and permeability K p ; Fractal dimension D of fissures f Permeability K measured by box counting method p Method of calculation: where Q is the gas flow rate, m 3 s; μ is the gas dynamic viscosity, Pa-s; L is the core length, m; A is the core cross-sectional area, m 2 ; P1 is the inlet pressure, Pa, P2 is the outlet pressure, Pa; P atm atmospheric pressure, P atm = 101325 Pa; S2, according to the blasting requirements of coal mining, the required blasting energy E is obtained b ; define the blasting energy E b The formula is as follows: E b = ∫ V [Po -βt + αs d (t)] · η(K P , D f )dV where E b is the explosion energy, J; P0is the initial pressure of the explosion wave, Pa; β is the pressure decay coefficient, s -1 ; σ d (t) is the dynamic stress component, Pa; a is the dynamic stress coupling coefficient, calibrated by experiment, usually in the range of 0.5-1.2; V is the volume to be blasted; η is the energy efficiency factor; The energy efficiency factor η is defined as follows: where K p is the permeability, K ref is the reference permeability; S3, define the perforating charge model, define the jet velocity v j Equation; The perforating charge DP36RDX25 model is defined as a jet model; Mass ratio m of the liner and the explosive c / m e The conditions must be met, that is, less than 0.3; the calculation method of the mass ratio m of the liner and the explosive: where δ is the average liner thickness in mm; p c is the liner material density in kg / m 3 ; D is the explosive detonation velocity in m / s; D0 is the reference detonation velocity in m / s; h e is the charge height in mm; p e is the explosive density in kg / m 3 ; Jet velocity v j The formula is as follows: In the formula, δ is the average thickness of the liner, mm; ω is the half-cone angle of the liner, °; d c is the average height of the explosive, mm; v c is the Poisson's ratio; S4, estimating the critical penetration depth L c ; Definition of critical penetration depth L c The formula is as follows: In the formula, L c is the critical penetration depth m; m j is the jet mass kg; v j is the jet velocity m / s; θ is the cone angle of the liner °; v c is the coal Poisson's ratio, generally taken as 0.2-0.35; E c is the elastic modulus Pa; ρ m is the coal density kg / m 3 ; K is the jet fracture correction coefficient, i.e. dimensionless; σ y is the dynamic compressive strength Pa; A j is the jet cross-sectional area m 2 ; v s is the coal longitudinal wave speed m / s; where the jet mass m is defined as j as follows: m j = η p · ρ j · π(d j / 2) 2 L j where η p is the jet participation coefficient, L j is the jet length m; d j is the jet diameter m; p j is the jet material density kg / m 3 ; The jet fracture correction coefficient K is determined through a high-speed photography test: L / d j >8 is continuous jet: K = 0.8 - 1.2; L / d j <5 is a broken jet: K = 1.2-2.0; Defining the jet cross-sectional area where d j is the jet diameter m; S5, estimating the stress field of the blasting force propagation; If the blasting force propagates along the coal seam during the blasting, the calculation method of the stress field of the blasting force propagation is as follows: In the formula, x is the radial distance from the blasting center, m; t0 is a reference time, s; σ0 is the initial stress amplitude, Pa, ζ is a fitting coefficient, Q is the charge mass, kg, and r0 is the charge radius, m. Γ is a geologic deterioration factor, dimensionless, D f D is a fracture fractal dimension, K p K is a permeability, K ref K is a reference permeability; Ψ is the elastic wave propagation term, m 2 / s 2 , γ is an empirically fitted coefficient, E c is the elastic modulus Pa, ρ m is the medium density kg / m 3 ; Φ is a viscoplastic decay term, dimensionless, σ y is the dynamic compressive strength Pa, p m is the rock density kg / m 3 v0 is the reference velocity m / s; λ is the time decay coefficient, s -1 ; Δε p plastic strain damage factor, dimensionless; ε cr εc is the critical strain, dimensionless; and ε cr εc is the critical strain, dimensionless; and ε m is a damage index, dimensionless; S6, the target blasting force F target , dynamic compressive strength σ y , geological correction factor g (D f , K p ) and elastic modulus E c and Poisson's ratio V c , select the appropriate perforating bullet size d optimal ; Perforator bullet size d optimal Method of calculation: where d optimal is the optimal perforating charge diameter m; F target is the target burst force N; p m is the medium density kg / m 3 ; g(D f , K p ) is the geological correction factor, dimensionless Wherein, the geological correction factor g(D f , K p ) calculation method: where D f is the fracture fractal dimension; K p is the permeability, K ref is the baseline permeability.

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