Method for determining the length of the air column and the length of the explosive column in axial spaced charge columns for rock blasting

Abstract

The application discloses a method for determining lengths of rock blasting axial interval charging explosive columns and air columns, and belongs to the technical field of engineering blasting. The application adopts the method of determining the dynamic compressive strength of rock mass under the original rock stress condition according to the field explosive parameters and engineering geological data and sampling the rock, determining the minimum hole wall peak pressure caused by different explosive columns and air column lengths by using theory, preliminarily screening the effective explosive column and air column length in combination with the dynamic compressive strength of the rock, verifying the screening result by using numerical simulation and physical model test, determining the reasonable air column length under the condition of different explosive column lengths, and finally determining the lengths of the explosive column and the air column of the axial interval charging blasting according to the field construction condition, so that the best effect of the axial air interval charging blasting can be achieved, the theoretical calculation method is adopted, the influence of the experience value on the blasting charging structure is reduced, and the selection of the blasting charging structure for various complex environments is more accurate.

Description

Technical Field

[0001] This invention belongs to the field of engineering blasting technology, specifically involving a method for determining the length of the axially spaced explosive column and air column in rock blasting. Background Technology

[0002] Currently, the increasingly complex engineering blasting environment and the ever-higher requirements for blasting effects mean that existing blasting theory research is far from meeting the needs of blasting engineering practice. In the fields of smooth blasting, pre-splitting blasting, and ultra-deep hole blasting, axial air-gap charging is widely used. Under air-gap charging conditions, the presence of the air layer can effectively reduce the average pressure on the borehole wall and prolong the interaction time with the borehole wall. Three shock wave fronts are formed successively in the borehole: the shock wave front of the explosive gas, and the shock wave front reflected from the bottom of the hole and the plugging end. Its rock-breaking effect is better than that of continuous coupled charging blasting. The presence of the air layer in air-gap charging reduces the amount of explosive, which can reduce the initial peak pressure of the explosive on the rock around the borehole, making the explosion pressure in the hole more evenly distributed along the borehole axis. This effectively avoids over-explosion in the surrounding rock near the charge and under-explosion in the surrounding rock far away, thereby improving the effective utilization rate of explosive energy during blasting. Furthermore, because air-gap charging reduces the unit consumption of explosives, it also reduces the hazards caused by blasting vibration.

[0003] Currently, when using axial air-spaced explosive blasting, it is necessary to provide a method for determining the length of the axial-spaced explosive column and the air column based on the geological parameters of the rock being blasted. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to overcome the shortcomings of the prior art and provide a method for determining the length of the axially spaced explosive column and air column in rock blasting.

[0005] The technical solution adopted to solve the above-mentioned technical problems is: a method for determining the length of the axially spaced explosive charge column and air column in rock blasting, including the following steps:

[0006] S1. To gain a preliminary understanding of the explosive parameters and geological parameters of the blasting rocks at the blasting site, and to take samples of the blasting rocks;

[0007] S2, Determine the dynamic compressive strength of the blasted rock mass under the original rock stress condition based on the rock sampled in step S1.

[0008] S3, determine the minimum peak pressure at the borehole wall under different explosive column lengths and different air column lengths;

[0009] S4. Based on the dynamic compressive strength of the blasted rock mass under the original rock stress condition in step S2 and the minimum peak pressure of the borehole wall under different explosive column lengths and different air column lengths obtained in step S3, the cracking conditions of the blasted rock mass are obtained, and the explosive column length and air column length of multiple sets of axially spaced explosive blasting are preliminarily screened.

[0010] S5. The minimum peak pressure of the borehole wall caused by the combination of explosive column length and air column length is simulated by numerical simulation to verify the explosive column length and air column length of multiple axially spaced explosive detonations in the screening step S4, and to further screen effective combinations of explosive column and air column lengths.

[0011] S6. Use a physical model to test and verify the lengths of the explosive column and air column selected in steps S4 and S5, and determine the reasonable length of the air column under different explosive lengths.

[0012] S7. Based on the on-site construction conditions, the lengths of the explosive column and air column for axially spaced explosive blasting in step S6 are finally determined.

[0013] Furthermore, the explosive parameters at the blasting site in step S1 include explosive density and detonation velocity, and the geological parameters of the blasted rock include rock burial depth, density, longitudinal wave propagation velocity, elastic modulus, and Poisson's ratio.

[0014] Furthermore, the method for determining the dynamic compressive strength of the blasted rock mass under the original rock stress condition in step S2 is as follows: a true triaxial dynamic load test is used.

[0015] Furthermore, the original rock stress includes the vertical stress and the horizontal stress of the original rock, and the calculation formulas for the vertical stress and the horizontal stress of the original rock are as follows:

[0016] σ v =ρgH (1)

[0017]

[0018] In formula (1) and formula (2), σ v σ represents the vertical stress of the original rock. h ρ is the horizontal stress of the original rock, g is the gravitational acceleration, H is the rock burial depth, and μ is the Poisson's ratio of the rock.

[0019] Furthermore, the formula for calculating the minimum peak pressure at the orifice wall in step S3 is as follows:

[0020]

[0021] α=2+μ / (1-μ) (4)

[0022] d r=2D a t s (5)

[0023]

[0024] In the above formula, P min This represents the minimum peak pressure at the orifice wall in the air column.

[0025] ρ is the density of the rock.

[0026] C p The speed of sound in rocks,

[0027] ρ0 is the density of the explosive.

[0028] D J The detonation velocity of the explosive in the rock.

[0029] l e The length of the explosive charge.

[0030] l a The length of the air column.

[0031] α is the detonation wave attenuation coefficient.

[0032] μ is the Poisson's ratio of the rock.

[0033] d r The length of the region where the peak values ​​of the detonation waves are superimposed.

[0034] D a The velocity of the detonation wave front in the air.

[0035] t s The duration of the detonation wave.

[0036] K is the volumetric compressibility modulus of the rock.

[0037] To compare distances,

[0038] Q represents the amount of explosive charge.

[0039] Furthermore, the cracking condition of the blasted rock mass in step S4 is as follows: the relationship between the dynamic compressive strength of the blasted rock mass under the original rock stress condition in step S2 and the minimum peak pressure of the borehole wall under different explosive column lengths and different air column lengths obtained in step S3 is:

[0040] P min ≥S C (7)

[0041] In the above formula, P min S represents the minimum peak pressure at the orifice wall in the air column. CIt represents the dynamic compressive strength of the rock mass under the original rock stress conditions.

[0042] The beneficial effects of the present invention are as follows: (1) The present invention adopts the method of determining the dynamic compressive strength of the rock mass under the original rock stress condition by taking samples of the rock based on the on-site explosive parameters and engineering geological data, using theory to determine the minimum peak pressure of the hole wall caused by different explosive column and air column lengths, combining the dynamic compressive strength of the rock to preliminarily screen out the effective explosive column and air column lengths, using numerical simulation and physical model testing to verify the screening results, determining the reasonable air column length under different explosive column length conditions, and finally determining the explosive column and air column lengths for axial interval charge blasting based on the on-site construction conditions, which can achieve the best effect of axial air interval charge blasting.

[0043] (2) The present invention adopts a theoretical calculation method, which reduces the influence of empirical values ​​on the explosive charge structure, and can quantitatively analyze the blasting effect with data, making the selection of explosive charge structure for various complex environments more accurate.

[0044] (3) This invention adopts the influence of different explosive section lengths and different air column lengths on the minimum peak pressure of the borehole wall in the explosive charge structure. At the same time, based on the rock blasting theory and the physical and mechanical properties parameters of the blasting rock, the effective explosive column and air column lengths are determined, thereby finding a more optimized explosive charge structure. Combined with the on-site construction conditions, the actual feasible explosive column length and air column length are selected. Attached Figure Description

[0045] Figure 1 This is a schematic diagram of a structural embodiment of the axial air-spaced charge of the present invention.

[0046] Figure 2 This is a schematic diagram of a numerical model for axially spaced explosive charges.

[0047] Figure 3 This is a photograph of a concrete thick-walled cylindrical model. Detailed Implementation

[0048] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0049] A schematic diagram of an axially spaced explosive charge, as shown below. Figure 1 As shown, the method for determining the length of the axially spaced explosive charge and air column in rock blasting includes the following steps:

[0050] S1: To gain a preliminary understanding of the explosive parameters and geological parameters of the blasting rocks at the blasting site, and to take samples of the blasting rocks.

[0051] The explosive parameters at the blasting site include explosive density and detonation velocity, while the geological parameters of the blasted rock include rock burial depth, density, longitudinal wave propagation velocity, elastic modulus, and Poisson's ratio.

[0052] S2, determine the dynamic compressive strength of the blasted rock mass under the original rock stress condition based on the rock sampled in step S1.

[0053] The stress in the original rock includes the vertical stress and the horizontal stress of the original rock. The formulas for calculating the vertical stress and the horizontal stress of the original rock are as follows:

[0054] σ v =ρgH (1)

[0055]

[0056] In formula (1) and formula (2), σ v σ represents the vertical stress of the original rock. h ρ is the horizontal stress of the original rock, g is the gravitational acceleration, H is the rock burial depth, and μ is the Poisson's ratio of the rock.

[0057] The method for determining the dynamic compressive strength of blasted rock mass under the original rock stress condition is to use a true triaxial dynamic load test.

[0058] S3, determine the minimum peak pressure of the borehole wall under different explosive column lengths and different air column lengths.

[0059] The formula for calculating the minimum peak pressure at the orifice wall is:

[0060]

[0061] α=2+μ / (1-μ) (4)

[0062] d r =2D a t s (5)

[0063]

[0064] In the above formula, P min This represents the minimum peak pressure at the orifice wall in the air column.

[0065] ρ is the density of the rock.

[0066] C p The speed of sound in rocks,

[0067] ρ0 is the density of the explosive.

[0068] D J The detonation velocity of the explosive in the rock.

[0069] l e The length of the explosive charge.

[0070] l a The length of the air column.

[0071] α is the detonation wave attenuation coefficient.

[0072] μ is the Poisson's ratio of the rock.

[0073] d r The length of the region where the peak values ​​of the detonation waves are superimposed.

[0074] D a The velocity of the detonation wave front in the air.

[0075] t s The duration of the detonation wave.

[0076] K is the volumetric compressibility modulus of the rock.

[0077] To compare distances,

[0078] Q represents the amount of explosive charge.

[0079] S4. Based on the dynamic compressive strength of the blasted rock mass under the original rock stress condition in step S2 and the minimum peak pressure of the borehole wall under different explosive column lengths and different air column lengths obtained in step S3, the cracking conditions of the blasted rock mass are obtained, and the explosive column length and air column length of multiple sets of axially spaced explosive blasting are preliminarily screened.

[0080] The cracking condition of the blasted rock mass is as follows: The relationship between the dynamic compressive strength of the blasted rock mass under the original rock stress condition in step S2 and the minimum peak borehole pressure under different explosive column lengths and different air column lengths obtained in step S3 is as follows:

[0081] P min ≥S C (7)

[0082] In the above formula, P min S represents the minimum peak pressure at the orifice wall in the air column. C It represents the dynamic compressive strength of the rock mass under the original rock stress conditions.

[0083] S5. The minimum peak pressure of the borehole wall caused by the combination of explosive column length and air column length is simulated by numerical simulation to verify the explosive column length and air column length of multiple axially spaced explosive detonations in the screening step S4, and to further screen effective combinations of explosive column and air column lengths.

[0084] S6. Use a physical model to test and verify the lengths of the explosive column and air column selected in steps S4 and S5, and determine the reasonable length of the air column under different explosive lengths.

[0085] The resistance signal is converted into a voltage signal using experimental instruments, and the output voltage is displayed using a display instrument. Finally, the stress value of the model is calculated.

[0086]

[0087] In the above formula, P represents the stress experienced by the model.

[0088] U is the output voltage.

[0089] E is the elastic modulus of the model.

[0090] k is the sensitivity coefficient of the instrument.

[0091] U0 is the instrument bridge voltage.

[0092] n is the number of strain gauges measured.

[0093] G represents the instrument gain.

[0094] S7. Based on the on-site construction conditions, the lengths of the explosive column and air column for axially spaced explosive blasting in step S6 are finally determined.

[0095] Example 1

[0096] A certain underground mine in Shanxi Province is designed to mine a porphyry gold ore body. The ore body is generally pocket-shaped, "inverted Y" shaped, and thick vein-like, often containing interbedded rocks. The ore body dips almost vertically, with a strike length of approximately 450m and a width of approximately 300m. The river bend porphyry ore body is vertically located between elevations of 425 and 900m, while the surface elevation of the mining area is approximately 1300m. The ore body is buried relatively deep and will be mined underground.

[0097] Based on the ore body morphology, occurrence conditions, and engineering geological conditions, the plan adopts the large-diameter deep-hole stage open-hole subsequent backfilling method. To achieve the established mining scale, this plan adopts dual-section mining, and in conjunction with the selection of mining methods, the 770m section of the first mining area and the 660m section of the second mining area are designated as the first mining section.

[0098] The standard ore block size in the stope is 30m×50m. It is divided into a stope and a pillar and mined in two steps. The stope and pillar are both 15m wide and 60m high in the middle section. The diameter of the blast hole is 120mm. Granular ammonium nitrate explosives are used for blasting on site.

[0099] Selecting the aforementioned underground stope, a method for determining the length of the axially spaced air column for rock blasting is implemented, comprising the following steps:

[0100] (1) To gain a preliminary understanding of the explosive parameters and engineering geological parameters of the rock mass at the blasting site, the density of granular ammonium nitrate fuel oil explosive is known to be 0.9 g / cm³. 3 The detonation velocity was 3000 m / s, the stope was buried at a depth of approximately 600 m, and the rock density was 2510 kg / m³. 3 The longitudinal wave propagation velocity of the rock was 3553 m / s, the rock elastic modulus was 16.2 GPa, and the rock Poisson's ratio was 0.21. Rock samples were taken at the mine site.

[0101] (2) Using the sampled rock, its physical and mechanical properties are determined through rock mechanics tests. The dynamic compressive strength of the blasted rock mass under its original rock stress conditions can be measured through true triaxial dynamic load tests. If the on-site original rock stress measurement conditions are insufficient, it can be calculated by the following formula:

[0102] σ v =ρgH=2510×9.8×600=14.76MPa

[0103]

[0104] The dynamic compressive strength S of blasted rock mass under in-situ stress conditions can be measured through true triaxial dynamic load tests. C =591.7MPa.

[0105] (3) The minimum peak pressure at the borehole wall under different explosive column lengths and different air column lengths is determined using the detonation wave theory. During axial air interval detonation, the minimum peak pressure at the borehole wall can be calculated by the following formula:

[0106]

[0107] α = 2 + μ / (1 - μ)

[0108] d r =2D a t s

[0109]

[0110] The minimum peak pressure at the borehole wall under different explosive column lengths and different air column lengths can be obtained, as shown in Table 1.

[0111] Table 1. Minimum peak pressure at the borehole wall under different explosive charge lengths and different air column lengths.

[0112]

[0113]

[0114] (4) Combining the dynamic compressive strength of the rock mass under the original rock stress condition and the minimum peak pressure of the borehole wall under different charge structures, the cracking conditions of the blasted rock mass are obtained, and multiple effective combinations of explosive column length and air column length are selected. The cracking conditions are as follows:

[0115] P min ≥S C =591.7 MPa

[0116] The effective combinations of explosive column length and air column length selected are shown in Table 2.

[0117] Table 2 Effective Combinations of Explosive Column Length and Air Column Length

[0118]

[0119] As can be seen from Table 2, all effective combinations are concentrated at and below the dividing line, which is roughly distributed along the diagonal.

[0120] (5) In order to verify the minimum peak pressure of the hole wall caused by the effective combination of explosive column length and air column length selected, numerical simulation is required.

[0121] Several numerical models containing single boreholes were established, such as... Figure 2 As shown, a multi-segmented charge structure is adopted, with 6 sections of explosive columns of equal length and 5 sections of air columns of equal length set inside the hole, and both ends are appropriately blocked. The height of the model is adjusted according to the length of the borehole and the charge structure.

[0122] To monitor the peak pressure on the borehole wall, a row of elements on the borehole wall along the borehole axis from the bottom to the opening was selected as stress monitoring points. To reduce simulation calculation errors and avoid the end effect caused by the reflection of explosives at the bottom and opening, the borehole wall elements of the three air columns in the middle of the entire borehole were selected as effective measuring points, and the calculation results of stress monitoring points at the same location were averaged.

[0123] To save simulation attempts and account for errors, only the effective combination boundary line and the combination that is taken one grid above it were verified. The numerical simulation verification results are shown in Table 3.

[0124] Table 3 Numerical simulation verification results

[0125]

[0126] As shown in Table 3, the relative error between the numerical simulation verification results and the theoretically calculated minimum peak pressure of the borehole wall is within 10%. The verification results of the effective combinations all meet the cracking conditions. The combination with the boundary line taken one grid upward basically does not meet the cracking conditions. The screening results meet the numerical simulation verification and can all be used as the predetermined combination of explosive column length and air column length.

[0127] (6) In order to verify the minimum peak pressure of the hole wall caused by the combination of the predetermined explosive column length and the air column length, it is also necessary to use physical model testing for verification.

[0128] Physical model testing employs dynamic stress-strain measurement technology, such as... Figure 3 As shown, according to the design, an axially spaced charge structure is adopted. The strain gauge measuring points are arranged at equal intervals inside the concrete model as designed. The peak pressure of the borehole wall at each position during the explosion of the axially spaced charge model is monitored. The same charge structure is blasted twice, and the average value of the test results is taken.

[0129] To save on physical model testing costs, only combinations at the top of the predetermined combination boundary are verified.

[0130] The resistance signal is converted into a voltage signal using experimental instruments, and the output voltage is displayed using a display instrument. Finally, the stress value of the model is calculated.

[0131]

[0132] In the above formula, P represents the stress experienced by the model.

[0133] U is the output voltage.

[0134] E is the elastic modulus of the model.

[0135] k is the sensitivity coefficient of the instrument.

[0136] U0 is the instrument bridge voltage.

[0137] n is the number of strain gauges measured.

[0138] G represents the instrument gain.

[0139] The results of the physical model test are shown in Table 4.

[0140] Table 4. Test and verification results of the physical model

[0141]

[0142]

[0143] As shown in Table 4, the relative errors between the physical model test verification results and the minimum peak pressure of the borehole wall calculated by theory and numerical simulation are all within 10%. The verification results all meet the cracking conditions, and the predetermined combination satisfies the physical model test verification.

[0144] Therefore, the air column length is determined as follows: when the explosive column length is 1.0m or more, the air column length is 0.4m; when the explosive column length is 1.2m or more, the air column length is 0.6m; when the explosive column length is 2.0m or more, the air column length is 0.8m; when the explosive column length is 3.0m or more, the air column length is 1.0m; and when the explosive column length is 4.0m or more, the air column length is 1.2m.

[0145] (7) Based on the on-site construction conditions, bulk granular ammonium nitrate explosives were used and explosives were loaded using a loading vehicle. The length of the blast hole was 50m. Considering that there were too many times of segmented loading and the construction was complicated, the length of the explosive column should not be too short. In addition, the mine currently has a 1m air separator. Based on the predetermined combination of explosive column length and air column length, the final loading structure was selected as a 3m explosive column and a 1m air column.

[0146] The above description is merely a preferred embodiment of the present invention and is not intended to limit the scope of protection of the present invention.

Claims

1. A method for determining the lengths of axially spaced explosive columns and air columns in rock blasting, characterized in that, Includes the following steps: S1. To gain a preliminary understanding of the explosive parameters and geological parameters of the blasting rocks at the blasting site, and to take samples of the blasting rocks; S2, Determine the dynamic compressive strength of the blasted rock mass under the original rock stress condition based on the rock sampled in step S1. S3, determine the minimum peak pressure at the borehole wall under different explosive column lengths and different air column lengths; the formula for calculating the minimum peak pressure at the borehole wall in step S3 is: （3） （4） （5） （6） In the above formula, This represents the minimum peak pressure at the orifice wall in the air column. For the density of the rock, The speed of sound in rocks, The density of the explosive, The detonation velocity of the explosive in the rock. The length of the explosive charge. The length of the air column. The detonation wave attenuation coefficient is... Poisson's ratio of the rock The length of the region where the peak values ​​of the detonation waves are superimposed. The velocity of the detonation wave front in the air. The duration of the detonation wave. The volumetric compressibility modulus of the rock. To compare distances, This refers to the amount of explosives loaded. S4. Based on the dynamic compressive strength of the blasted rock mass under the original rock stress condition in step S2 and the minimum peak pressure of the borehole wall under different explosive column lengths and different air column lengths obtained in step S3, the cracking conditions of the blasted rock mass are obtained, and the explosive column length and air column length of multiple sets of axially spaced explosive blasting are preliminarily screened. S5. The minimum peak pressure of the borehole wall caused by the combination of explosive column length and air column length is simulated by numerical simulation to verify the explosive column length and air column length of multiple axially spaced explosive detonations in the screening step S4, and to further screen effective combinations of explosive column and air column lengths. S6. Use a physical model to test and verify the lengths of the explosive column and air column selected in steps S4 and S5, and determine the reasonable length of the air column under different explosive lengths. S7. Based on the on-site construction conditions, the lengths of the explosive column and air column for axially spaced explosive blasting in step S6 are finally determined.

2. The method for determining the length of the axially spaced explosive charge column and air column in rock blasting according to claim 1, characterized in that: The explosive parameters at the blasting site in step S1 include explosive density and detonation velocity, and the geological parameters of the blasted rock include rock burial depth, density, longitudinal wave propagation velocity, elastic modulus, and Poisson's ratio.

3. The method for determining the length of the axially spaced explosive column and air column in rock blasting according to claim 1, characterized in that: The method for determining the dynamic compressive strength of the blasted rock mass under the original rock stress condition in step S2 is as follows: a true triaxial dynamic load test is used.

4. The method for determining the length of the axially spaced explosive charge and air column in rock blasting according to claim 1 or 3, characterized in that: The original rock stress includes the vertical stress and the horizontal stress of the original rock. The formulas for calculating the vertical stress and the horizontal stress of the original rock are as follows: （1） （2） In formulas (1) and (2), The vertical stress of the original rock. The horizontal stress of the original rock, The density of the overlying rock, It is the acceleration due to gravity. Due to the depth of the rock burial, is the Poisson's ratio of the rock.

5. The method for determining the length of the axially spaced explosive column and air column in rock blasting according to claim 1, characterized in that, The cracking condition of the blasted rock mass in step S4 is as follows: the relationship between the dynamic compressive strength of the blasted rock mass under the original rock stress condition in step S2 and the minimum peak borehole wall pressure under different explosive column lengths and different air column lengths obtained in step S3 is as follows: （7） In the above formula, This represents the minimum peak pressure at the orifice wall in the air column. It represents the dynamic compressive strength of the rock mass under the original rock stress conditions.

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