Cavern blasting cut thickness determination method based on ground stress redistribution

Abstract

The invention provides a cavern blasting cut thickness determination method based on ground stress redistribution. The method comprises the following steps: measuring and recording original ground stress and rock mechanical parameters of an underground cavern blasting excavation project; establishing a stress analysis model with a central hole according to the measured crustal stress and cut blasting pre-design; performing crustal stress unloading calculation of the central hole on the stress analysis model, and establishing a crustal stress redistribution model; constructing an explosion stress wave propagation model according to the rock material parameters and the explosive material parameters, and analyzing the stress state of the explosion stress wave propagating to the edge of the empty hole; whether radial cracks can be generated on the edge of the hollow hole or not is judged according to the coupling effect of circumferential pressure stress generated by ground stress redistribution caused by the central hollow hole and circumferential tensile stress caused by explosion stress waves on the edge of the hollow hole, and therefore the reasonable slotting thickness is determined.

Description

Technical Field

[0001] This invention relates to the field of rock blasting engineering technology, specifically to a method for determining the thickness of a blasting cut in a tunnel based on the redistribution of ground stress. Background Technology

[0002] In underground cavern blasting excavation, cut blasting is a crucial step in forming the initial free face and creating conditions for subsequent collapse blasting. The rational design of the cut thickness (i.e., the rock mass thickness between the cut center cavity and the cut borehole) directly determines the energy transfer efficiency of the blast, the crack propagation path, and the final excavation profile quality. Especially in high-stress rock environments, pre-set cavities can trigger severe stress unloading and redistribution, significantly altering the surrounding rock stress state and thus affecting the propagation of blast stress waves and crack initiation and propagation behavior.

[0003] Traditional cut thickness design often relies on engineering analogies or static mechanical assumptions, failing to fully consider the coupling effect of dynamic redistribution of ground stress and blast stress waves. For example, empirical formulas often determine the cut thickness based on multiples of the borehole diameter (e.g., 30-50 times), which, while simple and easy to implement, does not quantify the inhibitory effect of ground stress on blast cracks. Under high ground stress conditions, ground stress redistribution creates a circumferential compressive stress field around the borehole, significantly weakening the circumferential tensile stress induced by the blast stress wave at the borehole edge. If the cut thickness is still designed using traditional methods, excessive thickness can easily lead to insufficient blast energy to generate radial cracks at the borehole edge, resulting in cut failure or insufficient progress. Conversely, insufficient thickness may cause excessive energy concentration, expanding the damage area of ​​the surrounding rock and even triggering over-excavation or local collapse.

[0004] While some existing research has focused on the interaction between blast crack propagation and in-situ stress, most studies concentrate on optimizing borehole spacing or predicting crack paths, failing to systematically address the quantitative design problem of cut thickness. For example, patent CN117329941A optimizes borehole layout through a multi-level cut structure, but does not establish quantitative criteria for in-situ stress redistribution and crack initiation at the borehole edge; patent CN119514255A predicts crack propagation paths based on coupled stress field analysis, but its method relies on complex numerical simulations and programming calculations, resulting in a cumbersome and time-consuming process, making it difficult to apply for rapid on-site adjustments and optimizations.

[0005] Therefore, there is an urgent need for a method to determine the cut thickness that can quantify the coupling effect of ground stress redistribution and explosive load and is applicable to high ground stress environments, so as to achieve scientific, accurate and efficient blasting design. Summary of the Invention

[0006] The purpose of this invention is to provide a method for determining the cut thickness in tunnel blasting based on the stress redistribution caused by a central void, thereby solving the problem of inaccurate cut thickness design using traditional empirical methods in high-stress environments. This invention precisely determines the radial crack initiation conditions by quantitatively analyzing the static circumferential compressive stress field generated by the stress redistribution caused by the central void and the dynamic circumferential tensile stress field generated by the blast at the edge of the void. This allows for the derivation of a scientifically sound and reasonable cut thickness, ensuring efficient utilization of blasting energy and the formation of a regular initial free face.

[0007] To achieve the above-mentioned technical features, the objective of this invention is as follows: A method for determining the thickness of a tunnel blasting cut based on ground stress redistribution, comprising the following steps: Step 1: Measure and record the original geostress and rock mechanics parameters of the underground cavern blasting excavation project. Step 2: Based on the measured ground stress and the pre-design of the cut-out blasting, establish a stress analysis model with a central void. Step 3: Perform stress redistribution calculations on the stress analysis model at the center cavity and establish a stress redistribution model; Step 4: Construct an explosion stress wave propagation model based on rock material parameters and explosive material parameters, and analyze the stress state of the explosion stress wave propagating to the edge of the cavity; Step 5: Based on the coupling effect of the circumferential compressive stress caused by the redistribution of ground stress due to the central void and the circumferential tensile stress caused by the explosion stress wave at the edge of the void, determine whether radial cracks can be generated at the edge of the void, thereby determining the reasonable cut thickness.

[0008] Preferably, step 1 specifically includes: The original in-situ stress of the surrounding rock was measured, and the measured original in-situ stress in the vertical direction was set as... s v The original horizontal stress is set as s h The density of the rock was obtained by conducting material parameter calibration tests on the rock samples from the site. r 岩 Longitudinal wave velocity of rocks C 岩 Poisson's ratio of rocks m 岩 Dynamic tensile strength of rock s t Record the density of the explosives used. r 炸 The detonation velocity of explosives D 炸 Detonation isentropic index c Borehole wall pressure increase coefficient n ; lateral pressure coefficient calculated based on original geostress. A The calculation formula is: (1)

[0009] Preferably, when measuring the original in-situ stress of the surrounding rock in step 1, professional equipment and methods should be used to ensure that the in-situ stress measurement is accurate.

[0010] Preferably, step 2 specifically includes: Let the radius of the central void in the on-site cut-and-blast design be denoted as R 空 The cut thickness is S The thickness of the rock mass between the hollow hole at the center of the slotting blasting design and the slotting blast hole; the radius of the blast hole is set as... r Based on the above parameters, a stress analysis model including the central cavity and the borehole is constructed to analyze and calculate the redistribution of the ground stress field. In step 2, the borehole spacing, borehole radius, and central hole radius are based on the actual blasting design parameters, while the cut thickness is calculated and analyzed as a preset design parameter.

[0011] Preferably, step 3 specifically includes: Establish a polar coordinate system with the center of the void as the origin and the horizontal direction as the polar axis, and calculate the circumferential stress on the rock element at any void edge according to formula (2). s 空孔环 size; (2) in, i Polar angles are different angles in a polar coordinate system established with the center of the central hole as the origin and the radius in the horizontal direction as the polar axis.

[0012] Preferably, the stress redistribution model described in step 3 is based on the theory of elasticity and takes into account the stress redistribution after the pore is unloaded.

[0013] Preferably, step 4 specifically includes: First, calculate the explosive load generated by the explosive on the borehole wall according to formula (3). P 孔壁 : (3) In the formula, The diameter of the propellant charge; The rock element near the borehole experiences the least blasting force when it is furthest from any of the boreholes. Therefore, it is necessary to consider whether the rock at this location will fracture due to the blast. The distance of this rock element from the center of the borehole is also important. L for: (4) The rock element near the central borehole experiences radial compressive stress due to the action of a single borehole. s 径 for: (5) Then the circumferential tensile stress s 环 for: (6) In the formula, The attenuation coefficient is... l The lateral stress coefficient, l = m a / (1- m a ),and m a =0.8 m 岩 ; m a The dynamic Poisson's ratio for rocks.

[0014] Preferably, the attenuation coefficient in step 4 The value is determined based on the rock type and wave impedance, and ranges from 1.5 to 2.0.

[0015] Preferably, step 5 specifically includes: Circumferential tensile stress generated by the explosion at the edge of the central cavity rock element s 环 and the circumferential stress generated by the redistribution of ground stress s 空孔环 The combined effect of these factors leads to the determination of crack formation based on formula (7): (7) According to criterion formula (7), and in conjunction with formulas (1) to (6), the groove thickness is obtained. S for: (8) By substituting the measured parameters on site, the maximum cut thickness that can satisfy the radial crack at the edge of the void is calculated. The criterion formula (7) described in step 5 ensures that the circumferential tensile stress overcomes the dynamic tensile strength of the rock, thereby forming a radial crack.

[0016] Preferably, the method further includes step 6: calculating the maximum cut thickness according to formula (8) and performing on-site verification and optimization.

[0017] The present invention has the following beneficial effects: 1. Breaking through the limitations of traditional empirical design, this invention achieves the scientific and quantitative determination of cut thickness. Traditional methods rely on empirical formulas and do not consider the stress redistribution caused by pre-set voids in high-stress environments and its inhibitory effect on explosive cracking. This invention establishes a dynamic coupling model between stress redistribution and explosive stress waves, achieving for the first time the theoretical calculation and quantitative design of cut thickness, overcoming the problems of poor adaptability and large design deviations of traditional methods in high-stress areas.

[0018] 2. Significantly improves the reliability of blasting joint formation and the quality of excavation and crushing. By accurately calculating the interaction between the circumferential compressive stress generated by the redistribution of ground stress and the circumferential tensile stress induced by the blast load at the edge of the void, it ensures that within the designed cut thickness range, the blast energy is sufficient to generate effective radial cracks at the edge of the void, thereby reliably forming the initial free face. This effectively avoids "cutting failure" or insufficient advance due to excessive thickness, as well as excessive damage to the surrounding rock and over-excavation due to insufficient thickness, ensuring the smoothness and stability of the excavation profile.

[0019] 3. Highly efficient calculation process, suitable for rapid on-site optimization and adjustment. This invention establishes a complete closed-loop calculation framework based on a clear mechanical model and analytical formulas. The calculation time for a single working condition is short (controllable within 20 minutes), far faster than existing methods that rely on complex numerical simulations (which require several hours). This enables it to quickly respond to changes in geological conditions and stress fields at the tunnel face, providing a powerful technical tool for the dynamic optimization of on-site blasting parameters, especially suitable for projects with fast construction paces such as deep mines and long tunnels.

[0020] The present invention has the following advantages: For the first time, a dynamic coupling analysis of the stress redistribution field in cavities and the mechanical process of explosive stress wave propagation to the cavities was conducted, revealing the key mechanism by which circumferential compressive stress inhibits crack initiation, thus overcoming the technical limitations of traditional static assumptions and decoupled analysis. A quantitative index system was established, including key parameters such as rock dynamic tensile strength, stress anisotropy coefficient, and explosive load attenuation coefficient, ensuring the scientific nature of the design process and the reliability of the results. The method of this invention has clear logic and well-defined steps; all required parameters can be obtained through field testing or experiments, without relying on complex numerical software or programming skills, making it easy for field engineers to master and apply. It has wide applicability in high-stress cavern blasting projects in fields such as water conservancy, mining, and transportation. By accurately determining the cut thickness, the disturbance and damage to the surrounding rock can be minimized while ensuring the blasting effect, thereby reducing support costs, improving construction efficiency, and effectively controlling construction safety risks. Attached Figure Description

[0021] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0022] Figure 1 This is a design drawing of the layout of blast holes for slotting blasting under high ground stress according to the present invention.

[0023] Figure 2 This is a diagram of the stress redistribution analysis model for the central void in this invention.

[0024] Figure 3 This is a diagram of the coupled analysis model of explosive load and geostress for the central hollow rock unit of this invention.

[0025] Figure 4 This is a flowchart illustrating the implementation steps of the present invention.

[0026] Figure 5 This is a comparison diagram of the explosion effects of different methods of the present invention.

[0027] Legend: 1-Surrounding rock, 2-Central cavity, 3-Slot hole, 4-Horizontal stress, 5-Vertical stress, 6-Central cavity radius, 7-Slot thickness, 8-Rock element, 9-Circumferential stress s 空孔环 , 10-Explosion circumferential stress. Detailed Implementation

[0028] The present invention will be further described in detail below through specific embodiments. These embodiments are intended to enable those skilled in the art to gain a more comprehensive understanding of the present invention, but do not limit the invention in any way.

[0029] Example 1: This invention provides a method for determining the thickness of a tunnel cut during blasting based on ground stress redistribution, comprising the following steps: Step 1, Field measurement and acquisition of geostress and rock dynamic parameters: In the blasting excavation area, reliable in-situ testing methods such as hydraulic fracturing or stress relief methods are used to accurately measure the original in-situ stress of the rock mass ahead of the tunnel face. The measured vertical original in-situ stress is set as... s v The original horizontal stress is set as s h Complete rock cores were drilled on-site, and a series of tests were conducted in the laboratory to obtain the following parameters: the density of the rock was obtained through a standard density test. r 岩 The longitudinal wave velocity of the rock was obtained through ultrasonic pulse testing. C 岩 The Poisson's ratio of the rock was calculated by strain measurement in a uniaxial compression test. m 岩 The dynamic tensile strength of rock was obtained using the Hopkinson bar compression test (SHPB) or a modified Brazilian splitting test. s tDepending on the selected explosive type, obtain the following key performance parameters from its technical specifications or blasting manual: explosive density. r 炸 The detonation velocity of explosives D 炸 Detonation isentropic index c Borehole wall pressure increase coefficient n .

[0030] lateral pressure coefficient calculated based on original geostress. A The calculation formula is: (1) Step 2: Construct a stress analysis model for the blasting cut-out, including a central void. The actual blasting design scheme is abstracted into a physical model capable of mechanical analysis. Based on the blasting design drawings, the geometric parameters of the model are determined, including: the preset radius of the central hole. R 空 , radius of the blast hole r And the cut thickness to be analyzed and optimized. S This refers to the minimum rock mass thickness between the wall of the central void and the wall of the adjacent slotted blast hole. A stress analysis model incorporating the central void is established, with sufficiently large boundary boundaries to eliminate boundary effects. The original geostress measured in step 1 is applied to the far-field boundary of the model.

[0031] Step 3, Stress unloading analysis and redistribution model establishment in the central void: To accurately analyze the stress state around the void, a polar coordinate system is established with the center of the central void as the origin and the horizontal direction as the polar axis. Based on the theory of elasticity, after the formation of the central void, the circumferential stress experienced by any rock element on the edge of its wall is... s 空孔环 size.

[0032] (2) Step 4, Construction of the explosion stress wave propagation model and analysis of the dynamic stress state at the edge of the void: An explosion stress wave propagation model was constructed based on rock material parameters and explosive material parameters to analyze the stress state of the explosion stress wave propagating to the edge of the cavity. Specifically, this includes: firstly, calculating the explosive load generated on the borehole wall by the explosive according to formula (3). P 孔壁 : (3) In the formula, The diameter of the propellant charge; The rock element near the borehole experiences the least blasting force when it is furthest from any of the boreholes. Therefore, it is necessary to consider whether the rock at this location will fracture due to the blast. The distance of this rock element from the center of the borehole is also important. L for: (4) The rock element near the central borehole experiences radial compressive stress due to the action of a single borehole. s 径 for: (5) Then the circumferential tensile stress s 环 for: (6) In the formula, The attenuation coefficient is... l The lateral stress coefficient, l = m a / (1- m a ),and m a =0.8 m 岩 ; m a The dynamic Poisson's ratio of the rock; Step 5, Coupled analysis of composite stress field and quantitative determination of cut thickness: At the instant of the explosion, the rock elements at the edge of the central cavity simultaneously bear two types of stress: circumferential compressive stress generated by the redistribution of geostress (…). s 空孔环 (to suppress cracks) and the circumferential tensile stress generated by the explosion stress wave ( s 环 (Promoting crack formation). Whether a crack can be formed depends on the net effect of both. Therefore, a crack initiation criterion is established as shown in formula (7): only when the resultant circumferential tensile stress exceeds the dynamic tensile strength of the rock can an effective radial crack be ensured.

[0033] (7) Substitute the aforementioned formulas (1) to (6) into the crack initiation criterion formula (7) in turn. Through mathematical derivation and simplification, this criterion can be transformed into a formula concerning the cut thickness. S The explicit or implicit equation, i.e., formula (8): (8) Substituting all the field-measured parameters and design parameters obtained in step 1 into formula (8), and solving the problem, we can obtain the maximum allowable cut thickness that can ensure radial cracks at the edge of the void under specific geological and blasting conditions. S This thickness value is the scientific and reasonable cut thickness determined by this invention. This design avoids both insufficient blasting energy and cut failure due to excessive thickness, and excessive damage to the surrounding rock and over-excavation due to insufficient thickness.

[0034] Furthermore, when measuring the original in-situ stress of the surrounding rock in step 1, professional equipment and methods are required to ensure that the in-situ stress measurement is accurate. Furthermore, in step 2, the borehole spacing, borehole radius, and central hole radius are based on the actual blasting design parameters, while the cut thickness is calculated and analyzed as a preset design parameter. Furthermore, the stress redistribution model in step 3 is based on the theory of elasticity and takes into account the stress redistribution after the pore is unloaded; Furthermore, the attenuation coefficient in step 4 α The value is determined based on the rock type and wave impedance, and ranges from 1.5 to 2.0. Furthermore, the criterion formula (7) in step 5 ensures that the circumferential tensile stress overcomes the dynamic tensile strength of the rock, thereby forming a radial crack; Furthermore, the method also includes step 6: calculating the maximum cut thickness according to formula (8) and performing on-site verification and optimization.

[0035] Example 2: Step 1: Measurement of in-situ stress and rock parameters. The vertical in-situ stress is obtained based on the in-situ stress measurement of the surrounding rock 1. s v The horizontal stress is 10 MPa. s h For 10 MPa, such as Figure 1 As shown; the density of the rock was obtained by material parameter calibration tests on the rock samples from the field. r 岩 The longitudinal wave velocity of the rock is 2700 kg / m³. C 岩 The Poisson's ratio of the rock is 5400 m / s. m 岩 The dynamic tensile strength of the rock is 0.23. s t The pressure is 10 MPa; the density of the explosive used is... r 炸 The detonation velocity of the explosive is 1050 kg / m³. D 炸 The adiabatic index is 4500 m / s. c The value is 2.8. The lateral pressure coefficient can be calculated using formula (1). A The value is 1.

[0036] (1) Step 2: Establish the stress analysis model for the central void 2, and determine the radius of the central void in the field. R 空 The radius of the slotted blast hole is 0.05 m. r The depth is 0.02 m, and the cut thickness is S .

[0037] Step 3, calculate the redistribution of geostress. Establish a polar coordinate system with the center of the central cavity 2 as the origin and the horizontal direction as the polar axis. Calculate the circumferential stress on the rock element 8 at the edge of the central cavity 2 according to formula (2). s 空孔环 size.

[0038] (2) Step 4: Construct an explosion stress wave propagation model. First, calculate the explosion load generated by the explosive on the borehole wall according to formula (3). P 孔壁 Then, the attenuation coefficient is obtained based on relevant literature. α Simultaneously calculate the lateral stress coefficient. l The circumferential tensile stress experienced by rock element 8 at the edge of the central cavity s 环 Equation (4).

[0039] (3) (4) Step 5, Coupled analysis of composite stress field: The radial cracks in rock element 8 at the edge of the central cavity are caused by the circumferential tensile stress generated by the explosion. s 环 and the circumferential stress generated by the redistribution of ground stress s 空孔环 The combined effect of these factors controls the circumferential tensile stress. s 环 Circumferential stress generated by ground stress redistribution s 空孔环 The resultant force must be greater than the dynamic tensile strength of the rock. s t Then the condition for the formation of radial cracks in rock element 8 at the edge of the central pore is given by equation (5).

[0040] (5) Step 6, optimize the calculation. Based on the equation given in Step 5 and combined with the various physical parameter data measured on site, calculate the maximum thickness of the radial crack that satisfies the central pore rock unit (8) to form a crack of 0.2 m.

[0041] Example 3: The traditional empirical formula uses a cut thickness of 20 × 0.02 m = 0.4 m. However, considering the suppression of ground stress, this invention calculates the maximum cut thickness to be 0.2 m. For example... Figure 5 As shown, compared to traditional methods, the slot thickness calculated by this method effectively solves the problem that radial cracks cannot penetrate from the blast hole to the empty hole, thus achieving a good excavation and crushing effect. Furthermore, this method takes 20 minutes to calculate, while patent CN119514255A takes 6 hours to calculate the hole spacing based on the obtained ground stress, rock material, and explosive material, significantly longer than this invention, demonstrating its higher computational efficiency.

[0042] Although the preferred embodiments of the present invention have been described above in conjunction with the accompanying drawings, the present invention is not limited to the specific embodiments described above. The specific embodiments described above are merely illustrative and not restrictive. Those skilled in the art can make many specific modifications under the guidance of the present invention without departing from the spirit of the invention and the scope of protection of the claims, and these modifications all fall within the scope of protection of the present invention.

Claims

1. A method for determining the thickness of a tunnel blasting cut based on ground stress redistribution, characterized in that, Includes the following steps: Step 1: Measure and record the original geostress and rock mechanics parameters of the underground cavern blasting excavation project. Step 2: Based on the measured ground stress and the pre-design of the cut-out blasting, establish a stress analysis model with a central void. Step 3: Perform stress redistribution calculations on the stress analysis model at the center cavity and establish a stress redistribution model; Step 4: Construct an explosion stress wave propagation model based on rock material parameters and explosive material parameters, and analyze the stress state of the explosion stress wave propagating to the edge of the cavity; Step 5: Based on the coupling effect of the circumferential compressive stress caused by the redistribution of ground stress due to the central void and the circumferential tensile stress caused by the explosion stress wave at the edge of the void, determine whether radial cracks can be generated at the edge of the void, thereby determining the reasonable cut thickness.

2. The method for determining the thickness of a tunnel blasting cut based on ground stress redistribution according to claim 1, characterized in that, Step 1 specifically includes: The original in-situ stress of the surrounding rock was measured, and the measured original in-situ stress in the vertical direction was set as... σ v The original horizontal stress is set as σ h The density of the rock was obtained by conducting material parameter calibration tests on the rock samples from the site. ρ 岩 Longitudinal wave velocity of rocks C 岩 Poisson's ratio of rocks μ 岩 Dynamic tensile strength of rock σ t Record the density of the explosives used. ρ 炸 The detonation velocity of explosives D 炸 Detonation isentropic index γ Borehole wall pressure increase coefficient n ; lateral pressure coefficient calculated based on original geostress. A The calculation formula is: （1）。 3. The method for determining the thickness of a tunnel blasting cut based on ground stress redistribution according to claim 2, characterized in that, When measuring the original in-situ stress of the surrounding rock in step 1, professional equipment and methods are required to ensure that the in-situ stress measurement is accurate.

4. The method for determining the thickness of a tunnel blasting cut based on ground stress redistribution according to claim 2, characterized in that, Step 2 specifically includes: Let the radius of the central void in the on-site cut-and-blast design be denoted as R 空 The cut thickness is S The thickness of the rock mass between the hollow hole at the center of the slotting blasting design and the slotting blast hole; the radius of the blast hole is set as... r Based on the above parameters, a stress analysis model including the central cavity and the borehole is constructed to analyze and calculate the redistribution of the ground stress field. In step 2, the borehole spacing, borehole radius, and central hole radius are based on the actual blasting design parameters, while the cut thickness is calculated and analyzed as a preset design parameter.

5. The method for determining the thickness of a tunnel blasting cut based on ground stress redistribution according to claim 4, characterized in that, Step 3 specifically includes: Establish a polar coordinate system with the center of the void as the origin and the horizontal direction as the polar axis, and calculate the circumferential stress on the rock element at any void edge according to formula (2). σ 空孔环 size; （2） in, θ Polar angles are different angles in a polar coordinate system established with the center of the central hole as the origin and the radius in the horizontal direction as the polar axis.

6. The method for determining the thickness of a tunnel blasting cut based on ground stress redistribution according to claim 4, characterized in that, The stress redistribution model described in step 3 is based on the theory of elasticity and takes into account the stress redistribution after the pore is unloaded.

7. The method for determining the thickness of a tunnel blasting cut based on ground stress redistribution according to claim 4, characterized in that, Step 4 specifically includes: First, calculate the explosive load generated by the explosive on the borehole wall according to formula (3). P 孔壁 : （3） In the formula, The diameter of the propellant charge; The rock element near the borehole experiences the least blasting force when it is furthest from any of the boreholes. Therefore, it is necessary to consider whether the rock at this location will fracture due to the blast. The distance of this rock element from the center of the borehole is also important. L for: （4） The rock element near the central borehole experiences radial compressive stress due to the action of a single borehole. σ 径 for: （5） Then the circumferential tensile stress σ 环 for: （6） In the formula, The attenuation coefficient is... λ The lateral stress coefficient is... λ = μ a / (1- μ a ),and μ a =0.8 μ 岩 ; μ a The dynamic Poisson's ratio for rocks.

8. The method for determining the thickness of a tunnel blasting cut based on ground stress redistribution according to claim 4, characterized in that, The attenuation coefficient mentioned in step 4 The value is determined based on the rock type and wave impedance, and ranges from 1.5 to 2.

0.

9. The method for determining the thickness of a tunnel blasting cut based on ground stress redistribution according to claim 7, characterized in that, Step 5 specifically includes: Circumferential tensile stress generated by the explosion at the edge of the central cavity rock element σ 环 and the circumferential stress generated by the redistribution of ground stress σ 空孔环 The combined effect of these factors leads to the determination of crack formation based on formula (7): （7） According to criterion formula (7), and in conjunction with formulas (1) to (6), the groove thickness is obtained. S for: （8） By substituting the measured parameters on site, the maximum cut thickness that can satisfy the radial crack at the edge of the void is calculated. The criterion formula (7) described in step 5 ensures that the circumferential tensile stress overcomes the dynamic tensile strength of the rock, thereby forming a radial crack.

10. The method for determining the thickness of a tunnel blasting cut based on ground stress redistribution according to claim 9, characterized in that, It also includes step 6: calculate the maximum cut thickness according to formula (8), and perform on-site verification and optimization.

Images