Determination method of pre-splitting hole blasting parameters of pre-splitting blasting

Abstract

The invention discloses a method for determining blasting parameters of a pre-splitting hole in pre-splitting blasting. The method comprises the steps that the blast hole diameter, the charge non-coupling coefficient, the charge density, the blast hole density coefficient and the blast hole length of the pre-splitting hole are determined; according to the blast hole diameter of the pre-splitting hole and the charge non-coupling coefficient, the charge diameter of the pre-splitting hole is obtained; according to the charging diameter and the charging density of the pre-split hole, the linear charging density of the pre-split hole is obtained; according to the linear charge density of the pre-splitting hole and the length of the blast hole, the single-hole charge amount of the pre-splitting hole is obtained; according to the single-hole explosive charge / linear charge density of the pre-split holes, the pitch of the pre-split holes is obtained based on the blast hole density coefficient and the pre-split blasting unit consumption; and the filling length and the charging structure of the pre-split holes are obtained according to the pitch of the pre-split holes. By means of the calculation method, the design threshold of presplitting hole parameters in presplitting blasting is lowered, and the blasting success rate of primary design (or one-time engineering) is remarkably increased.

Description

Technical Field

[0001] This invention relates to the field of engineering blasting technology, and specifically to a method for determining the blasting parameters of pre-splitting holes in pre-splitting blasting. Background Technology

[0002] Pre-splitting blasting refers to the practice of creating a through-crack of a certain width along the designed outline before the main blasting zone during rock excavation. This serves to buffer and reflect the vibration waves from the excavation blast, controlling their destructive impact on the preserved rock mass and resulting in a smoother excavation profile. The effectiveness of this method directly affects the integrity of the preserved rock mass and the smoothness of the excavation surface.

[0003] In existing technologies, the calculation methods for pre-splitting blasting parameters (mainly linear charge density and hole spacing) are mainly divided into two categories: theoretical formulas and empirical formulas. The theoretical formula for linear charge density is generally as follows: This formula only considers the relationship between the ultimate compressive strength of rock, the explosive heat of detonation, and the linear charge density, without fully considering the relationship between the borehole diameter D and the hole spacing a and the linear charge density. In actual construction, the larger the borehole diameter, the higher the reasonable linear charge density; the larger the hole spacing, the higher the linear charge density required to form pre-cracks. Therefore, the calculation results obtained from this theoretical formula are not very instructive for actual construction. A general empirical formula for linear charge density is... In the formula, K, α, β, and γ are all coefficients. The Yangtze River Scientific Research Institute assigns the following values ​​to the coefficients: The Gezhouba Engineering Bureau uses the following values ​​for the coefficients: The Wuhan University of Hydraulic and Electric Engineering uses the following values ​​for the coefficients: As can be seen, the values ​​of coefficients K, α, β, and γ vary from research institution to research institution, making it difficult for general engineering technicians to select them accurately. The design process relies on personal experience, and the parameter selection is somewhat blind.

[0004] The theoretical formula for calculating the general hole spacing is: The formula states that the pre-splitting hole spacing is proportional to the borehole diameter. According to relevant literature, this formula can only be used after calculating the "optimal linear charge density" using the aforementioned theoretical formula for linear charge density. However, when using this theoretical hole spacing formula, the linear charge density has no direct relationship with the hole diameter or hole spacing, contradicting the practical experience in engineering that "when the linear charge density is fixed, the larger the hole diameter, the smaller the hole spacing." While some literature records empirical formulas for calculating hole spacing as a=(7~12)D, others as a=(8~12)D, these formulas are generally applicable to projects with high requirements for pre-splitting blasting. They are too small for semi-permanent slopes and permanent slopes in open-pit mines, and since they have no direct relationship with linear charge density, they cannot accurately guide actual engineering projects.

[0005] In summary, the formulas for determining pre-splitting blasting parameters mentioned above require several uncommon parameters in practice, and the calculation results are questionable, thus offering little practical guidance for engineering projects. Summary of the Invention

[0006] To address the aforementioned problems in the prior art, this invention provides a method for determining the blasting parameters of pre-splitting holes in pre-splitting blasting. The technical problem to be solved by this invention is achieved through the following technical solution:

[0007] A method for determining the blasting parameters of pre-splitting holes in pre-splitting blasting includes the following steps.

[0008] S1: Determine the borehole diameter, charge decoupling coefficient, charge density, borehole density coefficient, and borehole length for the pre-splitting borehole;

[0009] S2: Based on the borehole diameter of the pre-splitting hole and the charge decoupling coefficient, the charge diameter of the pre-splitting hole is obtained;

[0010] S3: Based on the charge diameter and charge density of the pre-splitting hole, obtain the linear charge density of the pre-splitting hole;

[0011] S4: The charge amount per pre-splitting hole is obtained based on the linear charge density and borehole length of the pre-splitting hole;

[0012] S5: The hole spacing of the pre-splitting holes is obtained based on the single hole charge / line charge density of the pre-splitting hole and the borehole density coefficient and the pre-splitting blasting unit consumption.

[0013] S6: The pre-splitting hole filling length and charge structure are obtained based on the pre-splitting hole spacing.

[0014] Furthermore, in S1, the charge decoupling coefficient of the pre-splitting hole is 2~5, and the borehole density coefficient of the pre-splitting hole is 0.5~0.7.

[0015] Furthermore, in step S2, the formula for calculating the charge diameter of the pre-splitting hole is:

[0016] In the formula, d is the diameter of the pre-splitting hole charge; D is the diameter of the pre-splitting hole borehole; and η is the charge decoupling coefficient of the pre-splitting hole.

[0017] Furthermore, in step S3, the formula for calculating the linear charge density of the pre-cracked hole is:

[0018] In the formula, The charge density of the pre-cracked hole. This refers to the charge density of the explosive used.

[0019] Furthermore, in step S4, the formula for calculating the charge amount per pre-splitting hole is as follows:

[0020] In the formula, L represents the charge amount per pre-splitting hole; L represents the length of the pre-splitting hole.

[0021] Furthermore, in step S5, the formula for calculating the pre-cracked hole spacing is:

[0022] In the formula, a is the spacing between pre-cracked holes; , This refers to the amount of explosive used when the effective range of action is a unit radius within a borehole of unit length upon detonation; while The rectangular range that is equivalent to the effective range of the circle.

[0023] Furthermore, in step S5, the formula for calculating the pre-cracked hole spacing is:

[0024] In the formula, a is the spacing between pre-cracked holes; , This refers to the amount of explosive used when the effective range of action is a unit radius within a borehole of unit length upon detonation; while The rectangular range that is equivalent to the effective range of the circle.

[0025] Furthermore, the aforementioned The The unit consumption for loosening and blasting.

[0026] Furthermore, in step S6, the formula for calculating the pre-cracked hole filling length is:

[0027] In the formula, This refers to the filling length of the pre-cracked hole.

[0028] The beneficial effects of this invention are:

[0029] 1. This invention simplifies the pre-splitting blasting design method through this process, avoiding the use of complex rock mechanics parameters such as rock tensile strength and Poisson's ratio, which are difficult to obtain accurately, thus lowering the design threshold and enabling the same geological conditions to achieve... Commonly used in engineering The hook provides a clear and reliable basis for parameter selection, significantly improving the success rate of blasting in initial design (or one-time project);

[0030] 2. By considering the decoupling coefficient, borehole density coefficient, and unit consumption... The core parameters such as aperture, aperture spacing, and charge amount were scientifically mathematically correlated, which changed the situation where parameter selection relied on experience in the traditional method and made the design results more in line with engineering practice.

[0031] 3. Integrate the pre-splitting blasting design method with the bench blasting design method to make the entire blasting engineering design more systematic and coordinated.

[0032] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0033] Figures 1-2 This is a schematic diagram illustrating the stress analysis and borehole density coefficient analysis process under stress wave action after pre-splitting hole detonation.

[0034] Figures 3-4 This is a schematic diagram illustrating the stress analysis and borehole density coefficient analysis process under quasi-static action after pre-splitting hole detonation.

[0035] Figure 5 This is a schematic diagram illustrating the analysis process of comprehensive stress, effective range, and borehole density coefficient in pre-splitting blasting.

[0036] Figure 6 This is a schematic diagram showing the equivalent of a circular effective range and a rectangular effective range. Detailed Implementation

[0037] The present invention will be further described in detail below with reference to specific embodiments, but the implementation of the present invention is not limited thereto.

[0038] This invention discloses a method for determining the blasting parameters of pre-splitting holes in pre-splitting blasting, specifically including the following methods:

[0039] S1: Determine the borehole diameter, charge decoupling coefficient, charge density, borehole density coefficient, and borehole length for the pre-splitting borehole;

[0040] Specifically, the diameter of the pre-splitting hole is selected according to the engineering needs and the drilling machinery that can be dispatched, the charge density is determined according to the required explosive type and charging process, and the length of the hole is determined according to the slope angle and step height. The embodiments of the present invention are not specifically limited here.

[0041] Specifically, in practical engineering applications, the decoupling coefficient of the charge in the pre-cracked hole The specific decoupling coefficient needs to be selected based on the type of project. When the protection of slope (surrounding rock) is strict Choose the larger value, and vice versa, depending on the specific project type.

[0042] Specifically, the borehole density coefficient m of the pre-splitting hole is 0.5~0.7.

[0043] Specifically, the stress analysis and borehole density coefficient analysis process under stress wave action after pre-splitting hole detonation are as follows:

[0044] Let the borehole diameter be D, the charge diameter be d, the decoupling coefficient be η, and the effective borehole length be L, then we have:

[0045]

[0046]

[0047]

[0048] This refers to the volume of the pre-splitting borehole. This represents the volume of explosives inside the pre-splitting hole.

[0049] As can be seen from the above formula, no matter how the aperture changes, as long as the charge coupling coefficient remains unchanged, the ratio of the pre-splitting borehole volume to the explosive volume remains unchanged.

[0050] In a less rigorous context, based on the ideal gas equation, it can be assumed that the peak pressure of the gas generated by the explosive detonation in the pre-splitting borehole remains constant. That is, if the decoupling coefficient of the charge is chosen appropriately, the borehole wall can be guaranteed to be free from compressive stress damage. The initial parameters of the borehole wall due to the blast shock wave remain unchanged, the pressure inside the hole is determined, and the pressure is proportional to the surface area of ​​the borehole.

[0051] The compressive stress on the rock surrounding the borehole deviates from its equilibrium position, causing tangential tensile stress on the rock. Ideally, this tangential tensile stress is inversely proportional to the distance from the mass point to the borehole and directly proportional to the pressure inside the borehole.

[0052] In the formula, F1 is the tangential tensile stress on the rock surrounding the borehole; P is the pressure inside the borehole; r is the borehole diameter; and R is the distance from the mass point to the center of the borehole. Figures 1-2 As shown, when the distance between a mass point and a pre-splitting hole is R1, the tangential tensile stress at that mass point is exactly half the tensile strength of the rock. When the distance between two adjacent pre-splitting holes is ≤2R1, the resultant force of the tangential tensile stress generated at the midpoint of the line connecting them is ≥ the tensile strength of the rock, and the stress wave action can directly form pre-cracks; when the distance between two adjacent pre-splitting holes is >2R1, the radial cracks on the line connecting the two adjacent pre-splitting holes will be more developed than in other directions, but the cracks cannot penetrate.

[0053] The effective range R1 can be qualitatively described by the initial state of the shock wave inside the borehole as being proportional to the initial state of the shock wave inside the borehole. The overlap of the effective range R1 can be described by the borehole density coefficient as the ratio of half the distance between two adjacent pre-splitting holes to the effective range R1, i.e.

[0054] In the formula, m1 is the stress wave intensity coefficient after the pre-splitting hole is detonated; R1 is the distance between the centers of the two pre-cracked holes under the premise of stress wave action analysis; R1 is the effective radius of the stress wave action range.

[0055] Among them, when When the effective range of the stress wave from two adjacent pre-cracked holes completely overlaps, The effective range of stress waves from two adjacent pre-cracked holes does not overlap at all.

[0056] Effective range of action: When two adjacent blast holes are detonated simultaneously, the combined force can cause the rock between the two blast holes to crack and form a gap. The range of action is called the effective range of action.

[0057] Quasi-static action analysis after pre-splitting hole initiation:

[0058] When the stress wave has passed and the rock fissures have not yet fully developed and no significant displacement has occurred, the pressure inside the borehole tends to stabilize. At this time, each pre-splitting hole is in a quasi-static action stage.

[0059] Let F2 be the radial force acting on a particle at a distance R2 from the pre-splitting hole. The component of this radial force perpendicular to the line connecting the two boreholes is F2ˊ = F2 × sinα. Figures 3-4 As shown.

[0060] The overlap ratio of two adjacent pre-cracked holes can be described as:

[0061] In the formula, m2 is the density coefficient of the quasi-static action range of the explosive gas after the pre-splitting hole is detonated; R2 is the distance between the centers of the two pre-cracked holes under the premise of quasi-static action analysis; R2 is the effective radius of the quasi-static action range.

[0062] As can be seen from the image, there are...

[0063] when If F2ˊ is greater than or equal to half the tensile strength of the rock, then pre-cracks can be formed; otherwise, pre-cracks cannot be formed.

[0064] When α = 45°~60°, i.e. m2 = 0.5~0.7, it is more conducive to forming a larger resultant force at the midpoint of the line connecting adjacent pre-splitting holes, perpendicular to the direction of the hole connection, and the number of holes will not be too large. Under this condition, a smaller amount of explosive and a moderate number of holes can be used to complete the pre-splitting blasting. Taking a smaller value of m2 is conducive to ensuring the success rate of the blasting design. It can be appropriately enlarged according to the blasting effect to improve economic benefits.

[0065] Comprehensive force analysis:

[0066] When m1 < 1, the actual charge exceeds the amount of explosive required for pre-splitting blasting. That is, although the pre-splitting blasting effect can be achieved, the bedrock damage is greater and the blasting control effect is poor.

[0067] When m2 < 1, pre-cracks can form. Without considering stress wave effects, a larger value requires more explosives but fewer boreholes. When the value approaches 1, the required explosives approach infinity; conversely, a smaller value requires less explosives but more boreholes. Extreme values ​​are not suitable for engineering purposes. A value between 0.5 and 0.7 balances blasting effectiveness and engineering economy.

[0068] As mentioned above, the formation of pre-cracks is not dominated by stress waves. The value of the borehole density coefficient m actually conforms to m2. However, the crack development is more complete in the direction of the connection between two boreholes than in other directions, which actually reduces the tensile strength of the rock in the direction of the connection between the two boreholes.

[0069] like Figure 5 As shown, under the combined action of stress wave and quasi-static force, the effective range of the pre-splitting hole is R, the hole spacing is a, and the hole density coefficient is m. Then the following relationship holds:

[0070] In the formula, .

[0071] S2: The charge diameter of the pre-splitting hole is obtained based on the borehole diameter and the charge decoupling coefficient.

[0072] Specifically, the formula for calculating the charge diameter of the pre-splitting hole is as follows:

[0073] In the formula, d is the charge diameter of the pre-splitting hole; D is the borehole diameter of the pre-splitting hole; and η is the charge decoupling coefficient of the pre-splitting hole.

[0074] S3: Based on the charge diameter and charge density of the pre-splitting hole, obtain the linear charge density of the pre-splitting hole;

[0075] The formula for calculating the linear charge density of pre-cracked holes is:

[0076] In the formula, The charge density of the pre-cracked hole. This refers to the charge density of the explosive used.

[0077] S4: The charge amount per pre-splitting hole is obtained based on the linear charge density and borehole length of the pre-splitting hole.

[0078] Specifically, the formula for calculating the charge amount per pre-splitting hole is as follows:

[0079] In the formula, L represents the charge amount per pre-splitting hole; L represents the length of the pre-splitting hole.

[0080] S5: The pre-splitting hole spacing is obtained based on the single-hole charge amount / linear charge density of the pre-splitting hole and the borehole density coefficient and the pre-splitting blasting unit consumption.

[0081] Specifically, the effective range of the pre-cracked hole In the formula: This refers to the amount of explosive used when the effective range of action is a unit radius in a borehole of unit length.

[0082] The effective range of the pre-cracked hole is equal to Then there is

[0083]

[0084] according to , and thus Then there is

[0085]

[0086] make

[0087]

[0088] like Figure 6 As shown, The rectangular range is equivalent to the effective range of the circle. The long side of the rectangular range is 2R, and the short side is a. a is equal to the distance between the centers of two connected pre-cracked holes, that is, the hole spacing of the pre-cracked holes.

[0089] but

[0090]

[0091] therefore,

[0092] Therefore, the formula for calculating the pre-cracked hole spacing 'a' can be obtained as follows:

[0093]

[0094] or

[0095]

[0096] Furthermore, through practical experience, we have concluded that... The This discovery greatly facilitates practical applications by reducing the unit consumption of loosening blasting.

[0097] S6: The pre-splitting hole filling length and charge structure are obtained based on the pre-splitting hole spacing.

[0098] Specifically, the formula for calculating the pre-cracked hole filling length is as follows:

[0099] In the formula, This refers to the filling length of the pre-cracked hole.

[0100] Finally, the amount of propellant in the filling section is loaded into the bottom of the borehole to form a charging structure with reinforced propellant charge at the bottom of the borehole.

[0101] The above description, in conjunction with specific preferred embodiments, provides a further detailed explanation of the present invention. It should not be construed that the specific implementation of the present invention is limited to these descriptions. For those skilled in the art, various simple deductions or substitutions can be made without departing from the concept of the present invention, and all such modifications and substitutions should be considered within the scope of protection of the present invention.

Claims

1. A method for determining the blasting parameters of pre-splitting holes in pre-splitting blasting, characterized in that, include: S1: Determine the borehole diameter, charge decoupling coefficient, charge density, borehole density coefficient, and borehole length for the pre-splitting borehole; S2: Based on the borehole diameter of the pre-splitting hole and the charge decoupling coefficient, the charge diameter of the pre-splitting hole is obtained; S3: Based on the charge diameter and charge density of the pre-splitting hole, obtain the linear charge density of the pre-splitting hole; S4: The charge amount per pre-splitting hole is obtained based on the linear charge density and borehole length of the pre-splitting hole; S5: The hole spacing of the pre-splitting holes is obtained based on the single hole charge / line charge density of the pre-splitting hole and the borehole density coefficient and the pre-splitting blasting unit consumption. S6: The pre-splitting hole filling length and charge structure are obtained based on the pre-splitting hole spacing.

2. The method for determining the blasting parameters of pre-splitting holes in pre-splitting blasting according to claim 1, characterized in that, In S1, the charge decoupling coefficient of the pre-splitting hole is 2~5, and the borehole density coefficient of the pre-splitting hole is 0.5~0.

7.

3. The method for determining the blasting parameters of pre-splitting holes in pre-splitting blasting according to claim 1, characterized in that, In step S2, the formula for calculating the charge diameter of the pre-splitting hole is: ； In the formula, d is the charge diameter of the pre-splitting hole; D is the borehole diameter of the pre-splitting hole; and η is the charge decoupling coefficient of the pre-splitting hole.

4. The method for determining the blasting parameters of pre-splitting holes in pre-splitting blasting according to claim 1, characterized in that, In step S3, the formula for calculating the linear charge density of the pre-cracked hole is: ； In the formula, The charge density of the pre-cracked hole. This refers to the charge density of the explosive used.

5. The method for determining the blasting parameters of pre-splitting holes in pre-splitting blasting according to claim 4, characterized in that, In step S4, the formula for calculating the charge amount per pre-splitting hole is as follows: ； In the formula, L represents the charge amount per pre-splitting hole; L represents the length of the pre-splitting hole.

6. The method for determining the blasting parameters of pre-splitting holes in pre-splitting blasting according to claim 4, characterized in that, In step S5, the formula for calculating the pre-cracked hole spacing is: ； In the formula, a is the spacing between pre-cracked holes; , This refers to the amount of explosive used when the effective range of action is a unit radius within a borehole of unit length upon detonation; while The rectangular range that is equivalent to the effective range of the circle.

7. The method for determining the blasting parameters of pre-splitting holes in pre-splitting blasting according to claim 5, characterized in that, In step S5, the formula for calculating the pre-cracked hole spacing is: ； In the formula, a is the spacing between pre-cracked holes; , This refers to the amount of explosive used when the effective range of action is a unit radius within a borehole of unit length upon detonation; while The rectangular range that is equivalent to the effective range of the circle.

8. The method for determining the blasting parameters of pre-splitting holes in pre-splitting blasting according to claim 6 or 7, characterized in that, The The The unit consumption for loosening and blasting.

9. The method for determining the blasting parameters of pre-splitting holes in pre-splitting blasting according to claim 8, characterized in that, In step S6, the formula for calculating the pre-cracked hole filling length is: ； In the formula, This refers to the filling length of the pre-cracked hole.

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