An experimental apparatus and method for simulating the damage characteristics of layered surrounding rock between boreholes.

Abstract

This invention provides an experimental device and method for simulating the damage characteristics of layered surrounding rock between blast holes. The device includes a support frame with Hopkinson rods at both ends. A rock mass sample is placed between the two Hopkinson rods, and a rock sample blast hole is located on one side of the sample. A baffle is placed on the blast hole, and fluid is supplied between the blast hole and the baffle. One of the Hopkinson rods strikes the blast hole, and the rock mass sample is cast using a casting mold. The device calculates the required radial and circumferential stresses, as well as the uniaxial compressive and tensile strengths, under different explosive charges, charge diameters, blast hole diameters, and distances from the calculation point to the charge center. Based on the obtained parameters, the device simulates the action of the explosive load during blast hole blasting. The device analyzes the damage characteristics of the rock sample under different blasting conditions using the calculated parameters, thereby achieving comprehensive and effective monitoring and measurement of the damage characteristics of layered surrounding rock between blast holes under blasting conditions. This method is suitable for widespread use.

Description

Technical Field

[0001] This invention relates to the field of blasting engineering, and in particular to a test apparatus and test method for simulating the damage characteristics of layered surrounding rock between blast holes. Background Technology

[0002] Drill-and-blast method, as an economical and efficient excavation method, is still widely used in deep rock excavation processes in hydropower, mining, and transportation projects in China. The destructive effect of blasting on the rock mass directly affects the quality and efficiency of blasting construction. The enormous energy generated by the explosion of explosives, while breaking up the rock mass and throwing fragments, inevitably causes direct damage and vibrational destruction to the remaining rock mass, leading to deterioration of the rock mass's mechanical properties, reduced strength, and decreased integrity, thus threatening the safety and stability of the project. Studying the rock-breaking mechanism and damage characteristics of blasting is of great significance for controlling the quality of blasting construction. Most existing blasting dynamic response simulation devices and methods use small doses of explosives in enclosed spaces, making it difficult to effectively and accurately control the blasting dynamics. On the other hand, some simulation methods that do not use explosives cannot reflect the effect of blasting loads. Therefore, we propose an experimental device and method to simulate the damage characteristics of layered surrounding rock between boreholes to solve the above problems. Summary of the Invention

[0003] The technical problem to be solved by the present invention is that most existing blasting dynamic response simulation devices and methods use small doses of explosives to conduct experiments in a closed space, which makes it difficult to effectively and accurately control the blasting dynamics. On the other hand, some simulation methods that do not use explosives fail to reflect the effect of blasting loads.

[0004] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is: a test device for simulating the damage characteristics of layered surrounding rock between blast holes, including a support, Hopkinson rods at both ends of the support, a rock mass sample between the two Hopkinson rods, a rock sample blast hole on one side of the rock mass sample, a baffle on the rock sample blast hole, and fluid between the rock sample blast hole and the baffle.

[0005] One of the Hopkinson rods was used to strike the rock sample borehole, and the rock sample was cast using a casting mold.

[0006] In the preferred embodiment, the two Hopkinson rods are arranged coaxially. The Hopkinson rod that strikes the rock sample borehole includes the incident rod. The rock sample borehole has a hemispherical structure, and the diameter of the rock sample borehole is slightly larger than the diameter of the incident rod of the Hopkinson rod. The rock sample borehole has a cylindrical path.

[0007] In the preferred embodiment, one side of the baffle is conical, and the fluid is a fluid with a bulk modulus of not less than 2.18 GPa.

[0008] In the preferred embodiment, the casting mold includes end molds at both ends, a U-shaped retaining template between the two end molds, a partition plate on the retaining template, a side film between the two end molds, and an arc plate on the side film.

[0009] In the preferred embodiment, strain gauges are installed on both Hopkinson bars, and the two strain gauges are connected to a dynamic signal acquisition instrument, which is connected to a computer. A high-speed camera and an infrared velocimeter are installed on one side of the rock mass sample.

[0010] A test method for a test device simulating the damage characteristics of layered surrounding rock between blast holes, the method comprising the following steps: S1, Pre-experiment preparation: Align two Hopkinson rods, each Hopkinson rod including an incident rod and a transmission rod, prepare a rock mass sample, with the Hopkinson rod of the incident rod facing the blast hole of the rock sample and in close contact with the hole opening baffle, and the other Hopkinson rod in close contact with the other side of the rock mass sample.

[0011] S2. Install the infrared velocimeter, adjust the height so that the infrared velocimeter is mounted on the bracket, adjust the instrument angle so that the high-speed camera is facing the rock sample, and record the deformation characteristics of the surrounding rock under dynamic load.

[0012] S3. Calculate the longitudinal wave velocity and damage variables of the rock mass sample, and calculate the relationship between the damage variables and the acoustic wave velocity of the rock mass before and after damage.

[0013] S4. The standard for judging the impact of blasting on rock mass samples is based on changes in wave velocity through borehole acoustic observation method.

[0014] S5. Calculate the shock wave pressure and detonation pressure required for macroscopic failure of a point at any distance from the center of the borehole in the rock mass sample; obtain the damage characteristics of the rock mass sample under blasting conditions.

[0015] S6. When the critical damage variables are different, determine the farthest explosion center distance at a certain location in the rock sample where macroscopic damage occurs under different explosive types, charge diameters, and borehole diameters.

[0016] In the preferred embodiment, in S3, according to wave theory, the longitudinal wave velocity propagating in a continuous, homogeneous, isotropic elastic medium can be expressed as:

[0017] (1);

[0018] middle: The longitudinal wave velocity of the rock mass. The dynamic elastic modulus of the rock mass. The density of the rock mass, The dynamic Poisson's ratio;

[0019] When the dominant characteristic dimensions of rock mass structural planes are much smaller than the wavelength of stress waves, the rock is generally considered to be an isotropic damaged material. Assuming that damage development leads to a decrease in the rock's elastic modulus, the damage variable is calculated as follows:

[0020] (2);

[0021] In the formula: D is the damage variable; To damage the dynamic elastic modulus; The dynamic elastic modulus of the undamaged rock;

[0022] Dynamic Poisson's ratio of rock mass Since the density ρ remains constant before and after the blast, substituting equation (2) into equation (1) yields: (3);

[0023] In the formula: The acoustic velocity of the rock mass after being affected by blasting;

[0024] Equation (3) yields the following relationship between the damage variable of the rock mass and the acoustic wave velocity of the rock mass before and after damage:

[0025] (4);

[0026] In the preferred scheme, in S4, a wave velocity change rate of no more than 15% has no effect or a negligible effect; a wave velocity change rate greater than 10% but not greater than 15% has a slight effect; and a wave velocity change rate greater than 15% has an effect. Based on equations (3) and (4), the two critical values ​​affected by the blast can be calculated, i.e., when the wave velocity change rate is 10%, the critical damage variable is D. lim When the wave velocity change rate is 15%, the critical damage variable D lim2 ;

[0027] In the preferred scheme, in S5, near the explosion source, the radial and circumferential stress amplitudes of the single-hole explosion stress wave in the rock mass sample (11) attenuate with distance according to the following formula:

[0028] (5);

[0029] (6);

[0030] In the formula: and These are the maximum radial dynamic stress and the maximum circumferential dynamic stress, respectively. The initial pressure of the shock wave penetrating into the rock; This is the distance from the center of the borehole. The radius of the borehole; For a shock wave, the pressure attenuation coefficient is... ; The lateral stress wave coefficient of the rock In the area affected by the shock wave, , ;

[0031] Depending on the stress state, it may exhibit tensile failure or compressive-shear failure. When the effective stress in the rock exceeds the rock's failure strength, macroscopic deformation failure will occur, producing crushed zones and fractured zones. The crushed zones and fractured zones satisfy the following conditions:

[0032] (Compression area) (7);

[0033] (fractured zone) (8);

[0034] In the formula: and These are the maximum effective stresses in the radial and circumferential directions, respectively. and These are the uniaxial dynamic compressive strength and dynamic tensile strength of the rock, respectively.

[0035] According to the acoustic approximation principle, the pressure of transmitted shock waves in rocks for:

[0036] (13);

[0037] Detonation pressure of the borehole for: (14);

[0038] In the formula: The density of the explosive; For the detonation velocity of the explosive; The isentropic exponent is the isentropic exponent of explosives. ; This is the pressure increase factor when the explosive products expand and collide with the borehole wall; it is generally taken as... ; This is the axial coefficient of the charge, generally taken as... ; The radial decoupling coefficient of the propellant charge. , The radius of the blast hole and the radius of the explosive charge are respectively.

[0039] In the preferred scheme, S6 is derived from formula ( )and( We can obtain: D lim and D lim2 Substitute ( )to( From the formula, we can obtain:

[0040] In the preferred scheme, S6 is obtained from equations (13) and (14): D lim and D lim2 Substituting into equations (5) and (8), we get:

[0041] D lim hour, (15);

[0042] (16);

[0043] D lim2 hour, (17);

[0044] (18);

[0045] Formulas (15) to (18) above are used to calculate the critical damage variables D. lim and D lim2 When different types of explosives, charge diameters, and borehole diameters are determined, the farthest distance from the blast center where macroscopic damage occurs at a certain location in a rock sample is ( ). ), to obtain the damage characteristics of rock samples under blasting conditions.

[0046] This invention provides an experimental apparatus and method for simulating the damage characteristics of layered surrounding rock between blast holes, utilizing a Hopkinson bar test device, rock samples, and a rock damage monitoring system. The Hopkinson bar test device applies dynamic loads to the rock samples while simultaneously monitoring their impact velocity using an infrared velocimeter, thereby enabling control over different impact forces. The rock samples are fabricated using concrete casting molds with nearly hemispherical blast holes filled with fluid and sealed with baffles at the hole openings. The dimensions of the rock samples and the radius of the blast holes can be altered as needed by changing the size of the mold. The rock damage monitoring system includes a high-definition camera, an acoustic wave detector, strain gauges, a dynamic signal acquisition device, and a computer.

[0047] Using the calculation method provided by the experiment, the required radial and circumferential stresses, as well as uniaxial compressive and tensile strengths, were calculated under different conditions of explosives, charge diameters, borehole diameters, and distances from the calculation point to the charge center. Subsequently, based on the obtained parameters, a Hopkinson bar was used to apply the required, numerically identical or similar dynamic load to the rock sample. The bar impacted the baffle sealing the borehole, applying pressure to the fluid inside the borehole. The load was transferred to the rock sample through the sealing baffle and the fluid, simulating the action of the explosive load during borehole blasting. Finally, an acoustic wave detector was used again to test the rock sample to obtain the acoustic wave velocity after the rock sample was damaged. Based on the relevant parameters calculated under different blasting conditions, a Hopkinson bar is used to apply the required, numerically identical or similar dynamic load to the rock sample to simulate the blasting load on the rock sample. At the same time, strain gauges are used to measure the strain of the rock sample, and an acoustic wave detector is used to measure the change in wave velocity before and after the rock sample is damaged, so as to analyze the damage characteristics of the rock sample under different blasting conditions. This enables comprehensive and effective monitoring and measurement of the damage characteristics of the inter-hole layered surrounding rock under blasting conditions, and is suitable for widespread use. Attached Figure Description

[0048] The present invention will be further described below with reference to the accompanying drawings and embodiments:

[0049] Figure 1 This is a schematic diagram of the overall structure of the present invention;

[0050] Figure 2 This is a cross-sectional view of the casting mold of the present invention;

[0051] Figure 3 This is a cross-sectional view of the rock mass sample of the present invention;

[0052] In the figure: Computer 1; Dynamic signal acquisition instrument 2; High-speed camera 3; Hopkinson bar 4; Infrared velocimeter 5; Casting mold 6; End mold 601; Enclosure mold 602; Partition 603; Side membrane 604; Arc plate 605; Strain gauge 7; Rock sample borehole 8; Baffle 9; Fluid 10; Rock mass sample 11; Support 12. Detailed Implementation

[0053] Example 1:

[0054] like Figures 1-3 In the present invention, a test device for simulating the damage characteristics of layered surrounding rock between blast holes includes a support 12, Hopkinson rods 4 at both ends of the support 12, a rock mass sample 11 between the two Hopkinson rods 4, a rock sample blast hole 8 on one side of the rock mass sample 11, a baffle 9 on the rock sample blast hole 8, and a fluid 10 between the rock sample blast hole 8 and the baffle 9.

[0055] One of the Hopkinson rods 4 strikes the rock sample borehole 8, and the rock sample 11 is cast using a casting mold 6. With this structure, the Hopkinson rod experimental device is used to apply dynamic loads to the rock sample 11, while an infrared velocimeter 5 monitors its impact velocity, thereby achieving control over different impact forces. The rock sample is made using a concrete casting mold 6, which has a nearly hemispherical rock sample borehole 8. Fluid 10 is injected into the borehole 8, and a baffle 9 is installed at the orifice for sealing. The size of the rock sample and the radius of the borehole can be changed as needed by altering the size of the mold. The rock damage monitoring system includes a high-speed camera 3, an acoustic wave detector, a strain gauge 7, a dynamic signal acquisition instrument 2, and a computer 1.

[0056] A rock sample 11 is fixed between two Hopkinson bars 4. Strain gauges 7 are installed on the incident rod of one Hopkinson bar 4 and the transmission rod of the other Hopkinson bar 4. The strain gauges 7 are connected in sequence to a dynamic signal acquisition instrument 2 and a waveform storage computer 1. A high-speed camera 3 is installed on a support 12 to record the observable external damage to the rock sample at the moment of impact. An acoustic wave detector is used to perform acoustic wave testing on the rock sample to obtain the acoustic velocity of the undamaged rock sample. Using the calculation method provided by the experiment, the values ​​of different explosives, charge diameters, and boreholes are calculated. Given the diameter, distance from the calculation point to the charge center, and other conditions, the required radial and circumferential stresses, as well as uniaxial compressive and tensile strengths, are determined. Based on these parameters, a Hopkinson bar is used to apply a similar or identical dynamic load to the rock sample. The bar impacts a baffle sealing the borehole, pressurizing the fluid within the borehole. The load is transferred to the rock sample through the baffle and fluid, simulating the blast load process during borehole blasting. Finally, an acoustic wave detector is used to test the rock sample again, obtaining the acoustic wave velocity after damage. Based on the parameters calculated under different blasting conditions, a Hopkinson bar is used to apply a similar or identical dynamic load to the rock sample to simulate the blast load. Strain gauges are used to measure the strain of the rock sample, and an acoustic wave detector measures the change in wave velocity before and after damage. This allows for the analysis of the damage characteristics of the rock sample under different blasting conditions, thus achieving comprehensive and effective monitoring and measurement of the damage characteristics of layered surrounding rock in blasting environments.

[0057] In the preferred embodiment, two Hopkinson rods 4 are arranged coaxially. The Hopkinson rod 4 that strikes the rock sample borehole 8 includes an incident rod. The rock sample borehole 8 has a hemispherical structure, and its diameter is slightly larger than the diameter of the incident rod of the Hopkinson rod 4. The rock sample borehole 8 has a cylindrical path. With this structure, rock sample boreholes 8 are opened on the rock mass sample 11. The blasted rock sample borehole 8 is roughly hemispherical, and a very short cylindrical path is set at the entrance of the rock sample borehole 8 so that the baffle can be displaced into the rock sample borehole 8 by a very small amount when it is impacted by the Hopkinson rod, thereby compressing the fluid 10.

[0058] In the preferred embodiment, one side of the baffle 9 is conical, and the fluid 10 is a fluid with a bulk elastic modulus of not less than 2.18 GPa. With this structure, the volume shrinkage rate of water with a bulk elastic modulus of 2.18 GPa at room temperature is 0.5%, which can be approximated as incompressible; therefore, the fluid inside the hole is a fluid with a bulk elastic modulus of not less than 2.18 GPa.

[0059] In the preferred embodiment, the pouring mold 6 includes end molds 601 at both ends, a U-shaped retaining template 602 between the two end molds 601, a partition plate 603 on the retaining template 602, a side film 604 between the two end molds 601, and an arc plate 605 on the side film 604.

[0060] In the preferred embodiment, strain gauges 7 are provided on both Hopkinson rods 4, and the two strain gauges 7 are connected to the dynamic signal acquisition instrument 2. The dynamic signal acquisition instrument 2 is connected to the computer 1, and a high-speed camera 3 and an infrared velocimeter 5 are provided on one side of the rock mass sample 11.

[0061] Example 2:

[0062] Further explanation based on Example 1: A test method for a test device simulating the damage characteristics of layered surrounding rock between blast holes includes the following steps: S1, Pre-experiment preparation: Align two Hopkinson rods 4, each of which includes an incident rod and a transmission rod. Prepare a rock mass sample 11. The Hopkinson rod 4 of the incident rod is directly facing the blast hole 8 of the rock sample and is in close contact with the hole baffle 9. The other Hopkinson rod 4 is in close contact with the other side of the rock mass sample 11.

[0063] S2. Install the infrared velocimeter 5, adjust its height so that the infrared velocimeter 5 is in the position where the impact rod impacts the incident rod, measure the impact speed, install the high-speed camera 3 on the bracket 12, adjust the instrument angle so that the high-speed camera 3 is facing the rock sample, and record the deformation characteristics of the surrounding rock under dynamic load.

[0064] S3. Calculate the longitudinal wave velocity and damage variable of rock mass sample 11, and calculate the relationship between the damage variable and the acoustic wave velocity of the rock mass before and after damage.

[0065] S4. Using the borehole acoustic observation method, the standard for judging the impact of blasting on rock mass sample 11 is determined based on the change in wave velocity.

[0066] S5. Calculate the shock wave pressure and detonation pressure required for macroscopic failure of a point at any distance from the center of the borehole in rock mass sample 11; obtain the damage characteristics of rock mass sample 11 under blasting conditions.

[0067] S6. When the critical damage variables are different, determine the farthest explosion center distance at a certain location in the rock sample where macroscopic damage occurs under different explosive types, charge diameters, and borehole diameters.

[0068] In the preferred embodiment, in S3, according to wave theory, the longitudinal wave velocity propagating in a continuous, homogeneous, isotropic elastic medium can be expressed as:

[0069] (1);

[0070] middle: The longitudinal wave velocity of the rock mass. The dynamic elastic modulus of the rock mass. The density of the rock mass, The dynamic Poisson's ratio;

[0071] When the dominant characteristic dimensions of rock mass structural planes are much smaller than the wavelength of stress waves, the rock is generally considered to be an isotropic damaged material. Assuming that damage development leads to a decrease in the rock's elastic modulus, the damage variable is calculated as follows:

[0072] (2);

[0073] In the formula: D is the damage variable; To damage the dynamic elastic modulus; For the dynamic elastic modulus of undamaged rock:

[0074] Dynamic Poisson's ratio of rock mass Since the density ρ remains constant before and after the blast, substituting equation (2) into equation (1) yields: (3);

[0075] In the formula: The acoustic velocity of the rock mass after being affected by blasting;

[0076] Equation (3) yields the following relationship between the damage variable of the rock mass and the acoustic wave velocity of the rock mass before and after damage:

[0077] (4).

[0078] In the preferred scheme, in S4, a wave velocity change rate of no more than 15% has no effect or a negligible effect; a wave velocity change rate greater than 10% but not greater than 15% has a slight effect; and a wave velocity change rate greater than 15% has an effect. Based on equations (3) and (4), the two critical values ​​affected by the blast can be calculated, i.e., when the wave velocity change rate is 10%, the critical damage variable is D. lim When the wave velocity change rate is 15%, the critical damage variable D lim2 ;

[0079] In the preferred scheme, in S5, near the explosion source, the radial and circumferential stress amplitudes of the single-hole explosion stress wave in the rock mass sample (11) attenuate with distance according to the following formula:

[0080] (5);

[0081] (6);

[0082] In the formula: and These are the maximum radial dynamic stress and the maximum circumferential dynamic stress, respectively. The initial pressure of the shock wave penetrating into the rock; This is the distance from the center of the borehole. The radius of the borehole; For a shock wave, the pressure attenuation coefficient is... ; The lateral stress wave coefficient of the rock In the area affected by the shock wave, ;

[0083] Depending on the stress state, it may exhibit tensile failure or compressive-shear failure. When the effective stress in the rock exceeds the rock's failure strength, macroscopic deformation failure will occur, producing crushed zones and fractured zones. The crushed zones and fractured zones satisfy the following conditions:

[0084] (Compression area) (7);

[0085] (fractured zone) (8);

[0086] In the formula: and They are respectively divided into radial and circumferential maximum effective stresses; and These are the uniaxial dynamic compressive strength and dynamic tensile strength of the rock, respectively.

[0087] When the surrounding rock is affected by blasting and reaches two thresholds, we can obtain the following from equations (5), (6), (7), and (8):

[0088] , (9);

[0089] (10);

[0090] , (11);

[0091] (12);

[0092] After a columnar explosive charge detonates in rock, it applies an impact load to the rock. Under uncoupled charge conditions, based on the acoustic approximation principle, the pressure of the transmitted shock wave in the rock is... for:

[0093] (13);

[0094] Detonation pressure of the borehole for: (14);

[0095] In the formula: The density of the explosive; To match the detonation velocity of the explosive; The isentropic exponent is the isentropic exponent of explosives. ; This is the pressure increase factor when the explosive products expand and collide with the borehole wall; it is generally taken as... ; This is the axial coefficient of the charge, generally taken as... ; The radial decoupling coefficient of the propellant charge. , The radius of the blast hole and the radius of the explosive charge are respectively.

[0096] In the preferred scheme, in S6, we can obtain from equations (13) and (14): D lim and D lim2 Substituting into equations (9) and (10), we get:

[0097] hour, (15);

[0098] (16);

[0099] hour, (17);

[0100] (18);

[0101] Formulas (15) to (18) above are used to calculate the critical damage variables D. lim and D lim2 Under the conditions of different explosive types, charge diameters, and borehole diameters, the farthest detonation center distance (r) at a certain location in a rock sample where macroscopic damage occurs is determined, and the damage characteristics of the rock sample under blasting conditions are obtained. The shock wave pressure and detonation pressure required for macroscopic damage to occur at any point in the rock sample at a distance of r from the borehole center are calculated.

[0102] Based on the obtained parameters, a Hopkinson bar can be used to apply a dynamic load, which is numerically the same or similar, to the rock sample to simulate the blasting load on the rock sample, thereby obtaining the damage characteristics of the rock sample in a blasting environment.

[0103] The above embodiments are merely preferred technical solutions of the present invention and should not be considered as limitations on the present invention. The embodiments and features described in these embodiments can be arbitrarily combined without conflict. The scope of protection of the present invention should be limited to the technical solutions described in the claims, including equivalent substitutions of the technical features described in the claims. That is, equivalent substitutions and improvements within this scope are also within the scope of protection of the present invention.

Claims

1. A test method for a test apparatus simulating the damage characteristics of layered surrounding rock between boreholes, characterized by: The following test apparatus was used for the test. The test apparatus includes a support (12), with Hopkinson rods (4) at both ends of the support (12), a rock mass sample (11) between the two Hopkinson rods (4), a rock sample borehole (8) on one side of the rock mass sample (11), a baffle (9) on the rock sample borehole (8), and fluid (10) between the rock sample borehole (8) and the baffle (9). One side of the baffle (9) is conical. One of the Hopkinson rods (4) strikes the rock sample borehole (8), and the rock sample (11) is cast using a casting mold (6); The method includes the following steps: S1, Preparatory work before the experiment: Align two Hopkinson rods (4), each of the two Hopkinson rods (4) includes an incident rod and a transmission rod, prepare a rock mass sample (11), with the Hopkinson rod (4) of the incident rod facing the rock sample borehole (8) and closely attached to the borehole baffle (9), and the other Hopkinson rod (4) closely attached to the other side of the rock mass sample (11); S2. Install the infrared velocimeter (5), adjust the height so that the infrared velocimeter (5) is in the position where the impact rod impacts the incident rod, measure the impact speed, install the high-speed camera (3) on the bracket (12), adjust the instrument angle so that the high-speed camera (3) is facing the rock sample (11), and record the deformation characteristics of the surrounding rock under dynamic load. S3. Calculate the longitudinal wave velocity and damage variable of rock mass sample (11) and calculate the relationship between the damage variable and the acoustic wave velocity of rock mass sample (11) before and after damage. S4. By using the borehole acoustic observation method, the standard for judging the impact of blasting on rock mass sample (11) is determined based on the change in wave velocity; S5. Calculate the shock wave pressure and detonation pressure required for macroscopic damage to occur at any distance from the center of the borehole in the rock mass sample (11), so as to obtain the damage characteristics of the rock mass sample (11) under the blasting environment. S6. When the critical damage variables are different, determine the farthest blast center distance at a certain location in a rock sample where macroscopic damage occurs under different explosive types, charge diameters, and borehole diameters. In S3, according to wave theory, the longitudinal wave velocity propagating in a continuous, homogeneous, isotropic elastic medium can be expressed as: （1）； middle: The longitudinal wave velocity of rock mass sample (11) is... Let be the dynamic elastic modulus of the rock mass sample (11). The density of the rock mass, For dynamic Poisson's ratio; When the dominant characteristic dimension of the structural plane of the rock mass sample (11) is much smaller than the wavelength of the stress wave, the rock mass sample (11) is regarded as an isotropic damaged material. Damage development leads to a decrease in the elastic modulus of the rock mass sample (11), and the damage variable is calculated as follows: （2）； In the formula: D is the damage variable; The dynamic elastic modulus of the rock mass sample (11) is the damage modulus. Dynamic Poisson's ratio of rock mass Since the density ρ remains constant before and after the blast, substituting equation (2) into equation (1) yields: (3); In the formula: The acoustic wave velocity of rock mass sample (11) after being affected by blasting; Equation (3) yields the following relationship between the damage variable of rock mass sample (11) and the acoustic wave velocity of rock mass sample (11) before and after damage: （4）。 2. The test method of the test apparatus for simulating the damage characteristics of layered surrounding rock between boreholes according to claim 1, characterized in that: Two Hopkinson rods (4) are arranged coaxially. The Hopkinson rod (4) that strikes the rock sample borehole (8) includes the incident rod. The rock sample borehole (8) has a hemispherical structure. The diameter of the rock sample borehole (8) is slightly larger than the diameter of the incident rod of the Hopkinson rod (4). The rock sample borehole (8) has a cylindrical path.

3. The test method of the test apparatus for simulating the damage characteristics of layered surrounding rock between boreholes according to claim 1, characterized in that: The fluid (10) is a fluid with a bulk modulus of not less than 2.18 GPa.

4. The test method of the test apparatus for simulating the damage characteristics of layered surrounding rock between boreholes according to claim 1, characterized in that: The casting mold (6) includes end molds (601) at both ends, a U-shaped retaining template (602) between the two end molds (601), a partition plate (603) on the retaining template (602), a side film (604) between the two end molds (601), and an arc plate (605) on the side film (604).

5. The test method of the test apparatus for simulating the damage characteristics of layered surrounding rock between boreholes according to claim 1, characterized in that: Strain gauges (7) are provided on both Hopkinson rods (4). The two strain gauges (7) are connected to the dynamic signal acquisition instrument (2). The dynamic signal acquisition instrument (2) is connected to the computer (1). A high-speed camera (3) and an infrared velocimeter (5) are provided on one side of the rock mass sample (11).

6. The method according to claim 1, wherein in S4, the wave velocity variation rate is not more than 10%, having no or little influence; the wave velocity variation rate is more than 10% but not more than 15%, having slight influence; and the wave velocity variation rate is more than 15%, having influence, and two critical values influenced by blasting are calculated according to formula (3) and (4), i.e. when the wave velocity variation rate is 10%, the critical damage variable is D lim , and when the wave velocity variation rate is 15%, the critical damage variable is D lim2 . lim lim2 ​​ 7. The test method of the test apparatus for simulating the damage characteristics of layered surrounding rock between boreholes as described in claim 6, characterized in that: S5 When near the blast source, the radial and circumferential stress amplitudes of the single-hole blast stress wave in rock mass sample (11) attenuate with distance according to the following formula: （5）； （6）； In the formula: and These are the maximum radial dynamic stress and the maximum circumferential dynamic stress, respectively. The transmitted shock wave pressure in the rock mass sample (11); The distance from the center of the borehole. The radius of the borehole; For a shock wave, the pressure attenuation coefficient is... ; The lateral stress wave coefficient of the rock In the area affected by the shock wave, ; Depending on the stress state, it may exhibit tensile failure or compressive-shear failure. When the effective stress in the rock exceeds the rock's failure strength, macroscopic deformation failure will occur, producing crushed zones and fractured zones. The crushed zones and fractured zones satisfy the following conditions: (Crushing area) (7); (fractured zone) (8); In the formula: and These are the maximum effective stresses in the radial and circumferential directions, respectively. and These are the uniaxial dynamic compressive and dynamic tensile strengths of rock mass sample (11), respectively. According to the acoustic approximation principle, the transmitted shock wave pressure in the rock mass sample (11) for: （13）； Detonation pressure of the borehole for: (14); In the formula: The density of the explosive; For the detonation velocity of the explosive; is the isentropic exponent, and the isentropic exponent is 1; The pressure increase factor when the explosive products expand and collide with the borehole wall is taken as... =6; This is the axial coefficient of the charge, generally taken as... ; The radial decoupling coefficient of the propellant charge. , The radius of the blast hole and the radius of the explosive charge are respectively.

8. The test method of the test apparatus for simulating the damage characteristics of layered surrounding rock between boreholes as described in claim 7, characterized in that: S6 From equations (13) and (14), we obtain: According to the formula From formulas (5) to (8), we can obtain that D lim hour, (15); （16）； D lim2 hour, (17); （18）； Formulas (15) to (18) above are used to calculate the critical damage variables D. lim and D lim2 When different types of explosives, charge diameters, and borehole diameters are determined, the distance r from the center of the borehole to a certain location in the rock mass sample (11) where macroscopic damage occurs is obtained, and the damage characteristics of the rock mass sample (11) under the blasting environment are acquired.

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