CN116840082A - Test device and test method for simulating damage characteristics of interlayer-shaped surrounding rock of blasthole - Google Patents
Test device and test method for simulating damage characteristics of interlayer-shaped surrounding rock of blasthole Download PDFInfo
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- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N3/00—Investigating strength properties of solid materials by application of mechanical stress
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- G01N2203/02—Details not specific for a particular testing method
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Abstract
The application provides a test device and a test method for simulating the damage characteristics of lamellar surrounding rock among blastholes, comprising a bracket, hopkinson bars at two ends of the bracket, wherein a rock sample is arranged between the two Hopkinson bars, one side of the rock sample is provided with a rock sample blasthole, a baffle is arranged on the rock sample blasthole, and fluid is arranged between the rock sample blasthole and the baffle; one of the Hopkinson bars hits a rock sample blast hole, and a rock mass sample is poured by a pouring die. Calculating the radial and circumferential stress and uniaxial compressive and tensile strength required under the conditions of different explosive, charging diameter, blast hole diameter and distance from a calculation point to the charging center; simulating the action process of explosion load during blast hole blasting according to the obtained related parameters; according to the relevant parameters calculated under different blasting conditions, the damage characteristics of rock samples under different blasting conditions are analyzed, so that the comprehensive and effective monitoring and measuring of the damage characteristics of the interlayer-shaped surrounding rock under the blasting environment are realized, and the method is suitable for popularization and use.
Description
Technical Field
The application relates to the field of blasting engineering, in particular to a test device and a test method for simulating the damage characteristics of interlayer-shaped surrounding rock of a blast hole.
Background
The drilling and blasting method is used as an economic and efficient excavation mode, and is still widely applied to deep rock mass excavation processes of domestic hydropower, mine, traffic and other projects at present. The blasting effect directly influences the quality and efficiency of blasting construction on rock mass, the huge energy generated by explosive explosion inevitably causes direct damage and vibration damage to reserved rock mass while breaking the rock mass and throwing fragments, so that the mechanical property of the rock mass is deteriorated, the strength is reduced and the integrity is poor, thereby threatening the safety and stability of engineering, and the research on the rock breaking mechanism and the breaking characteristics of blasting has important significance for controlling the blasting construction quality. Most of the existing blasting power response simulation devices and methods adopt small-dose explosive to test in a closed space, so that effective and accurate control of blasting power is difficult, and the effect of blasting load is difficult to embody without adopting an explosive simulation means. Therefore, a test device and a test method for simulating the damage characteristics of the inter-borehole layer surrounding rock are provided for solving the problems.
Disclosure of Invention
The application aims to solve the technical problems that the existing blasting power response simulation device and method mostly adopt small-dose explosive to test in a closed space, so that the blasting power is difficult to effectively and accurately control, and the action of the blasting load is difficult to embody without adopting an explosive simulation means.
In order to solve the technical problems, the application adopts the following technical scheme: the test device for simulating the damage characteristics of the interlayer-shaped surrounding rock of the blasthole comprises a bracket, hopkinson rods at two ends of the bracket, a rock sample is arranged between the two Hopkinson rods, a rock sample blasthole is arranged on one side of the rock sample, a baffle is arranged on the rock sample blasthole, and fluid is arranged between the rock sample blasthole and the baffle;
one of the Hopkinson bars hits a rock sample blast hole, and a rock mass sample is poured by a pouring die.
In the preferred scheme, two hopkinson bars are coaxially arranged, the hopkinson bars striking the rock sample blast holes comprise incident bars, the rock sample blast holes are hemispherical in structure, the diameter of each rock sample blast hole is slightly larger than that of each incident bar of each hopkinson bar, and each rock sample blast hole is provided with a section of cylindrical path.
In a preferred scheme, one side of the baffle is conical, and the fluid is a fluid with a bulk modulus of elasticity of not less than 2.18 GPa.
In the preferred scheme, the watering mould includes the end mould at both ends, is equipped with the surrounding template of U type structure between two end moulds, is equipped with the baffle on the surrounding template, is equipped with the side membrane between two end moulds, is equipped with the circular arc board on the side membrane.
In the preferred scheme, strain gauges are arranged on two Hopkinson bars, the two strain gauges are connected with a dynamic signal acquisition instrument, the dynamic signal acquisition instrument is connected with a computer, and a high-speed camera and an infrared velocimeter are arranged on one side of a rock mass sample.
A test method of a test device for simulating the damage characteristics of a shell rock in a shell layer of a blast hole comprises the following steps: the method comprises the following steps: s1, preparation before experiment: aligning two Hopkinson bars, wherein the two Hopkinson bars respectively comprise an incident bar and a transmission bar, a rock mass sample is manufactured, the Hopkinson bar of the incident bar is opposite to a rock sample blast hole and is clung to an orifice baffle, and the other Hopkinson bar is clung to the other side of the rock mass sample;
s2, installing an infrared velocimeter, adjusting the height, enabling the infrared velocimeter to be installed on a bracket, adjusting the angle of the instrument, enabling a high-speed camera to be opposite to a rock sample, and recording deformation characteristics of surrounding rock under the action of load;
s3, calculating the longitudinal wave velocity in the rock mass sample and the damage variable of the rock mass sample, and calculating the relation between the damage variable and the acoustic wave velocity of the rock mass before and after damage;
s4, judging the standard of the rock mass sample affected by blasting according to the wave speed change by a drilling acoustic observation method;
s5, calculating the shock wave pressure and detonation pressure required by macroscopic damage of a point which is located at any distance from the center of the blast hole in the rock mass sample; acquiring damage characteristics of a rock mass sample in a blasting environment;
and S6, determining the farthest explosive distance of macroscopic damage at a certain position in the rock sample under the conditions of different explosive types, charging diameters and blast hole diameters when the critical damage variables are different.
In a preferred embodiment, in S3, according to the wave theory, the wave velocity of the longitudinal wave propagating in the continuous, uniform, isotropic elastic medium can be expressed as:
in (a): v (V) p Is the longitudinal wave velocity of rock mass E d Is the dynamic elastic modulus of the rock mass, ρ is the density of the rock mass, v d Is a dynamic poisson ratio;
rock is generally considered an isotropically damaged material when the dominant feature size of the rock mass structural face is much smaller than the stress wave wavelength. Assuming that the damage development results in a decrease in the elastic modulus of the rock, the damage variable is calculated as:
wherein: d is injury; e (E)d is the damage dynamic elastic modulus;is the dynamic elastic modulus of the lossless rock;
the dynamic poisson ratio vd and the density ρ of the rock mass are kept unchanged before and after blasting, and the formula (2) is substituted into the formula (1) to obtain:
wherein: v (V) p The sonic wave velocity of the rock mass after being affected by the blasting;
the relation between the damage variable of the rock mass and the sonic wave velocity of the rock mass before and after damage is obtained by the formula (3):
in the preferred scheme, in S4, the wave speed change rate is not more than 15%, and the influence is not or little; the wave speed change rate is more than 10% but not more than 15%, the influence is slight, and the wave speed change rate is more than 15%, and the influence is caused. From equations (3) and (4), two critical values affected by blasting, namely, a critical damage variable D when the wave velocity change rate is 10%, can be calculated lim The method comprises the steps of carrying out a first treatment on the surface of the When the wave velocity change rate is 15%, the critical damage variable D lim2 ；
In the preferred scheme, in S5, when the rock mass sample (11) is near an explosion source, the radial and circumferential stress amplitude of a single Kong Baozha stress wave meets the following formula along with the distance attenuation law:
(σ r ) max ＝P(r/r d ) -α (5)；
wherein: (sigma) r ) max Sum (sigma) r ) max Radial maximum dynamic stress and circumferential maximum dynamic stress are respectively; p is the initial pressure of the shock wave transmitted into the rockForce; r is the distance from the center of the blast hole, r d The radius of the blast hole; alpha is the pressure decay coefficient, alpha is approximately 3 for the shock wave;lateral coefficient of stress wave for rock->In the region of action of the shock wave, < >>
Depending on the stress conditions, either tensile failure or compressive shear failure may be exhibited, and when the effective stress in the rock exceeds the failure strength of the rock, macroscopic deformation failure phenomena will occur, yielding crush zones and fracture zones that satisfy the following conditions:
(σ′ r ) max ≥(σ r ) max /(1-D lim )＝σ cd (compression zone) (7);
-(σ′ θ ) max ≥-(σ θ ) max /(1-D lim )＝σ td (fissure zone) (8);
wherein: (sigma' r ) max And- (sigma ')' θ ) max The method is divided into radial and annular maximum effective stress respectively; sigma (sigma) cd Sum sigma td The uniaxial dynamic compression strength and the dynamic tensile strength of the rock are respectively;
according to the principle of acoustic approximation, the transmitted shock wave pressure P in the rock is:
detonation pressure P of blast hole 0 The method comprises the following steps:
wherein: ρ 0 Is the density of the explosive; d is the detonation velocity of the explosive; gamma rayThe isentropic index of the explosive is isentropic index gamma=3; n is the pressure increase coefficient when the explosive explosion product expands and collides with the wall of the gun hole, and n=10 is generally taken; l (L) e For axial coefficient of charge, take l in general e =1 to 1.41; k is the radial uncoupled coefficient of the charge,r d ，r c the radius of the blast hole and the radius of the medicine bag are respectively.
In a preferred embodiment, S6 is obtained by formulas (13) and (14):D lim and D lim2 Substitution of formulas (5) to (8) yields:
D lim in the time-course of which the first and second contact surfaces,
D lim2 in the time-course of which the first and second contact surfaces,
the above formulas (15) to (18) calculate that the critical damage variables are D respectively lim And D lim2 And when the type, the charging diameter and the blast hole diameter of different explosives are determined, the furthest explosion center distance (r) of macroscopic damage to a certain position in the rock sample is obtained, and the damage characteristic of the rock sample in the explosion environment is obtained.
The application provides a test device and a test method for simulating the damage characteristics of a surrounding rock in a layer shape of a blast hole. The Hopkinson bar experimental device is used for applying dynamic load to the rock sample, and simultaneously, an infrared velocimeter is used for monitoring the impact speed of the rock sample, so that the control of different impact powers is realized; the rock sample is manufactured by using a concrete pouring die, a nearly hemispherical blast hole is formed in the rock sample, fluid is filled in the hole, a baffle is arranged at the hole opening for sealing, and the size of the rock sample and the radius of the blast hole can be changed by changing the size of the die according to the requirement; the rock damage monitoring system comprises a high-definition camera, an acoustic wave detector, a strain gauge, a dynamic signal acquisition instrument and a computer.
Calculating the radial and circumferential stress and uniaxial compressive and tensile strength required under the conditions of different explosive, charging diameter, blast hole diameter and distance from a calculation point to the charging center by a calculation method provided by a test; then, according to the obtained related parameters, a required dynamic load with the same or similar value can be applied to the rock sample by using a Hopkinson bar, the bar impacts a baffle plate of a sealing orifice to apply pressure to a Kong Naliu body, the load is transferred to the rock sample through the sealing baffle plate and fluid, and the action process of explosion load during blast hole blasting is simulated; and finally, carrying out acoustic testing on the rock sample by using an acoustic detector again to obtain the acoustic wave velocity after the rock sample is damaged. According to the relevant parameters calculated under different blasting conditions, the Hopkinson bar is used for applying the required dynamic load with the same or similar numerical value to the rock sample so as to simulate the blasting load action of the rock sample, meanwhile, the strain of the rock sample is measured by using the strain gauge, the change of wave velocity before and after the rock sample is damaged is measured by using the acoustic wave detector, and the damage characteristics of the rock sample under different blasting conditions are analyzed, so that the comprehensive and effective monitoring and measurement of the damage characteristics of the interlayer surrounding rock under the blasting environment are realized, and the method is suitable for popularization and use.
Drawings
The application is further illustrated by the following examples in conjunction with the accompanying drawings:
FIG. 1 is a schematic diagram of the overall structure of the present application;
FIG. 2 is a cross-sectional view of the casting mold of the present application;
FIG. 3 is a cross-sectional view of a rock mass specimen of the present application;
in the figure: a computer 1; a dynamic signal acquisition instrument 2; a high-speed camera 3; hopkinson bar 4; an infrared velocimeter 5; pouring a mold 6; an end die 601; a surrounding template 602; a partition 603; a side film 604; a circular arc plate 605; a strain gage 7; a rock sample blast hole 8; a baffle 9; a fluid 10; a rock mass sample 11; a bracket 12.
Detailed Description
Example 1:
as shown in fig. 1 to 3, a test device for simulating the damage characteristics of a surrounding rock in a layer shape of a blasthole comprises a bracket 12, hopkinson bars 4 at two ends of the bracket 12, a rock sample 11 is arranged between the two Hopkinson bars 4, a rock sample blasthole 8 is arranged on one side of the rock sample 11, a baffle 9 is arranged on the rock sample blasthole 8, and a fluid 10 is arranged between the rock sample blasthole 8 and the baffle 9;
one of the hopkinson bars 4 strikes a rock sample blast hole 8, and a rock sample 11 is poured by a pouring die 6. The Hopkinson bar experimental device is used for applying dynamic load to the rock mass sample 11, and simultaneously, the infrared velocimeter 5 is used for monitoring the impact speed of the rock mass sample, so that the control of different impact powers is realized; the rock sample is manufactured by using a concrete pouring die 6, a nearly hemispherical rock sample blast hole 8 is formed in the rock sample blast hole 8, fluid 10 is injected into the rock sample blast hole 8, a baffle 9 is arranged at an orifice for sealing, and the size of the rock sample and the radius of the blast hole can be changed by changing the size of the die according to the requirement; the rock damage monitoring system comprises a high-speed camera 3, an acoustic wave detector, a strain gauge 7, a dynamic signal acquisition instrument 2 and a computer 1.
A rock mass sample 11 is fixed between two Hopkinson bars 4, a strain gauge 7 is arranged on an incident bar of one Hopkinson bar 4 and a transmission bar of the other Hopkinson bar 4, the strain gauge 7 is sequentially connected with a dynamic signal acquisition instrument 2 and a waveform storage computer 1, a high-speed camera 3 is arranged on a bracket 12 to record the observable damage condition of the exterior of the rock sample at the moment of impact, and a sound wave detector is used for carrying out sound wave test on the rock sample to obtain the sound wave speed of the nondestructive rock sample; calculating the radial and circumferential stress and uniaxial compressive and tensile strength required under the conditions of different explosive, charging diameter, blast hole diameter and distance from a calculation point to the charging center by a calculation method provided by a test; then, according to the obtained related parameters, a required dynamic load with the same or similar value can be applied to the rock sample by using a Hopkinson bar, the bar impacts a baffle plate of a sealing orifice to apply pressure to a Kong Naliu body, the load is transferred to the rock sample through the sealing baffle plate and fluid, and the action process of explosion load during blast hole blasting is simulated; and finally, carrying out acoustic testing on the rock sample by using an acoustic detector again to obtain the acoustic wave velocity after the rock sample is damaged. According to the relevant parameters calculated under different blasting conditions, the Hopkinson bar is used for applying the required dynamic load with the same or similar numerical value to the rock sample so as to simulate the blasting load action of the rock sample, meanwhile, the strain of the rock sample is measured by using the strain gauge, the change of wave velocity before and after the rock sample is damaged is measured by using the acoustic wave detector, and the damage characteristics of the rock sample under different blasting conditions are analyzed, so that the comprehensive and effective monitoring and measuring of the damage characteristics of the interlayer surrounding rock under the blasting environment are realized.
In the preferred scheme, two hopkinson bars 4 are coaxially arranged, the hopkinson bars 4 striking the rock sample blast holes 8 comprise incidence bars, the rock sample blast holes 8 are hemispherical in structure, the diameter of the rock sample blast holes 8 is slightly larger than the diameter of the incidence bars of the hopkinson bars 4, and the rock sample blast holes 8 are provided with a section of cylindrical path. With this structure, the rock sample hole 8 is formed in the rock sample 11, the blasted rock sample hole 8 is approximately hemispherical, and an extremely short cylindrical path is formed at the entrance of the rock sample hole 8, so that the baffle plate can displace extremely little in the rock sample hole 8 when being impacted by the hopkinson rod, and the fluid 10 is compressed.
In a preferred embodiment, the baffle 9 has a conical shape on one side, and the fluid 10 has a bulk modulus of not less than 2.18 GPa. With this structure, the volume reduction rate of the water having a bulk modulus of 2.18GPa at normal temperature is 0.5%, which can be regarded as being approximately incompressible; thus the fluid in the hole has a bulk modulus of not less than 2.18 GPa.
In the preferred scheme, the pouring die 6 comprises end dies 601 at two ends, a surrounding die plate 602 with a U-shaped structure is arranged between the two end dies 601, a baffle 603 is arranged on the surrounding die plate 602, a side film 604 is arranged between the two end dies 601, and an arc plate 605 is arranged on the side film 604.
In the preferred scheme, strain gauges 7 are arranged on two Hopkinson bars 4, the two strain gauges 7 are connected with a dynamic signal acquisition instrument 2, the dynamic signal acquisition instrument 2 is connected with a computer 1, and a high-speed photographic instrument 3 and an infrared velocimeter 5 are arranged on one side of a rock mass sample 11.
Example 2:
further description in connection with example 1: a test method of a test device for simulating the damage characteristics of a shell rock in a shell-hole layer comprises the following steps: s1, preparation before experiment: aligning two Hopkinson bars 4, wherein the two Hopkinson bars 4 respectively comprise an incident bar and a transmission bar, a rock sample 11 is manufactured, the Hopkinson bars 4 of the incident bar are opposite to a rock sample blast hole 8 and are clung to an orifice baffle 9, and the other Hopkinson bar 4 is clung to the other side of the rock sample 11;
s2, installing an infrared velocimeter 5, adjusting the height to enable the infrared velocimeter 5 to be positioned at the position of an impact rod impacting an incident rod, measuring the impact speed, installing a high-speed camera 3 on a bracket 12, adjusting the angle of the instrument to enable the high-speed camera 3 to be opposite to a rock sample, and recording deformation characteristics of surrounding rock under the action of load;
s3, calculating the longitudinal wave velocity in the rock mass sample 11 and the damage variable of the rock mass sample 11, and calculating the relation between the damage variable and the acoustic wave velocity of the rock mass before and after damage;
s4, judging the standard of the rock mass sample 11 affected by blasting according to the wave speed change by a drilling acoustic observation method;
s5, calculating the shock wave pressure and detonation pressure required by macroscopic damage of a point which is located at any distance from the center of the blast hole in the rock mass sample 11; acquiring damage characteristics of the rock mass sample 11 in a blasting environment;
and S6, determining the farthest explosive distance of macroscopic damage at a certain position in the rock sample under the conditions of different explosive types, charging diameters and blast hole diameters when the critical damage variables are different.
In a preferred embodiment, in S3, according to the wave theory, the wave velocity of the longitudinal wave propagating in the continuous, uniform, isotropic elastic medium can be expressed as:
in (a): v (V) p Is the longitudinal wave velocity of rock mass E d Is the dynamic elastic modulus of the rock mass, ρ is the density of the rock mass, v d Is a dynamic poisson ratio;
rock is generally considered an isotropically damaged material when the dominant feature size of the rock mass structural face is much smaller than the stress wave wavelength. Assuming that the damage development results in a decrease in the elastic modulus of the rock, the damage variable is calculated as:
wherein: d is injury; ed is the dynamic elastic modulus of the injury;is the dynamic elastic modulus of the lossless rock;
the dynamic poisson ratio vd and the density ρ of the rock mass are kept unchanged before and after blasting, and the formula (2) is substituted into the formula (1) to obtain:
wherein: v (V) p The sonic wave velocity of the rock mass after being affected by the blasting;
the relation between the damage variable of the rock mass and the sonic wave velocity of the rock mass before and after damage is obtained by the formula (3):
in the preferred scheme, in S4, the wave speed change rate is not more than 15%, and the influence is not or little; the wave speed change rate is more than 10% but not more than 15%, the influence is slight, and the wave speed change rate is more than 15%, and the influence is caused. From equations (3) and (4), two critical values affected by blasting, namely, a critical damage variable D when the wave velocity change rate is 10%, can be calculated lim The method comprises the steps of carrying out a first treatment on the surface of the Critical damage when the wave velocity change rate is 15%Variable D 1im2 ；
In the preferred scheme, in S5, when the rock mass sample (11) is near an explosion source, the radial and circumferential stress amplitude of a single Kong Baozha stress wave meets the following formula along with the distance attenuation law:
(σ r ) max ＝P(r/r d ) -α (5)；
wherein: (sigma) r ) max Sum (sigma) r ) max Radial maximum dynamic stress and circumferential maximum dynamic stress are respectively; p is the initial pressure of the shock wave transmitted into the rock; r is the distance from the center of the blast hole, r d The radius of the blast hole; alpha is the pressure decay coefficient, alpha is approximately 3 for the shock wave;lateral coefficient of stress wave for rock->In the region of action of the shock wave, < >>
Depending on the stress conditions, either tensile failure or compressive shear failure may be exhibited, and when the effective stress in the rock exceeds the failure strength of the rock, macroscopic deformation failure phenomena will occur, yielding crush zones and fracture zones that satisfy the following conditions:
(σ′ r ) max ≥(σ r ) max /(1-D lim )＝σ cd (compression zone) (7);
-(σ′ θ ) max ≥-(σ θ ) max /(1-Dl im )＝σ td (fissure zone) (8);
wherein: (sigma' r ) max And- (sigma ')' θ ) max Is respectively divided into radial and annular directionsMaximum effective stress; sigma (sigma) cd Sum sigma td The uniaxial dynamic compression strength and the dynamic tensile strength of the rock are respectively;
when the surrounding rock reaches two thresholds under the influence of blasting, the following formulas (5), (6), (7) and (8) can be obtained:
①D lim ＝0.19，(σ′ r ) max ≥1.23P(r d /r) 3 ＝σ cd (9)；
-(σ′ θ ) max ≥1.23P(r d /r) 3 ＝σ td (10)；
②D lim ＝0.28(σ′ r ) max ≥1.39P(r d /r) 3 ＝σ cd (11)；
-(σ′ θ ) max ≥1.39P(r d /r) 3 ＝σ td (12)；
after the cylindrical explosive charges in the rock explode, impact load is applied to the rock, and under the uncoupled explosive charge condition, the transmitted impact wave pressure P in the rock is as follows according to the approximate acoustic principle:
detonation pressure P of blast hole 0 The method comprises the following steps:
wherein: ρ 0 Is the density of the explosive; d is the detonation velocity of the explosive; gamma is an isentropic index, and the isentropic index of the explosive gamma=3; n is the pressure increase coefficient when the explosive explosion product expands and collides with the wall of the gun hole, and n=10 is generally taken; l (L) e For axial coefficient of charge, take l in general e =1 to 1.41; k is the radial uncoupled coefficient of the charge,r d ，r c the radius of the blast hole and the radius of the medicine bag are respectively.
In a preferred embodiment, in S6, the compounds of formulae (13) and (14) areTo obtain:D lim and D lim2 Substitution of formulas (9) to (10) yields:
①D lim when the value of the ratio is =0.19,
②D lim when the value of the ratio is =0.28,
the above formulas (15) to (18) calculate that the critical damage variables are D respectively lim And D lim2 And when the type, the charging diameter and the blast hole diameter of different explosives are determined, the furthest explosion center distance (r) of macroscopic damage to a certain position in the rock sample is obtained, and the damage characteristic of the rock sample in the explosion environment is obtained. And calculating the shock wave pressure and detonation pressure required by macroscopic damage of any point of the rock sample, which is located at the center of the blast hole.
According to the obtained relevant parameters, a required dynamic load with the same or similar numerical value can be applied to the rock sample by using the Hopkinson bar so as to simulate the blasting load action of the rock sample, thereby obtaining the damage characteristics of the rock sample in the blasting environment.
The above embodiments are merely preferred embodiments of the present application, and should not be construed as limiting the present application, and the embodiments and features of the embodiments of the present application may be arbitrarily combined with each other without collision. The protection scope of the present application is defined by the claims, and the protection scope includes equivalent alternatives to the technical features of the claims. I.e., equivalent replacement modifications within the scope of this application are also within the scope of the application.
Claims (10)
1. A test device for simulating the damage characteristics of a shell-like surrounding rock in a blasthole interlayer is characterized in that: the device comprises a bracket (12), hopkinson bars (4) at two ends of the bracket (12), a rock sample (11) is arranged between the two Hopkinson bars (4), a rock sample blast hole (8) is arranged on one side of the rock sample (11), a baffle (9) is arranged on the rock sample blast hole (8), and a fluid (10) is arranged between the rock sample blast hole (8) and the baffle (9);
one of the Hopkinson bars (4) hits a rock sample blast hole (8), and a rock mass sample (11) is poured by a pouring die (6).
2. The test device for simulating the damage characteristics of the inter-borehole layer surrounding rock according to claim 1, wherein the test device is characterized by: the two Hopkinson bars (4) are coaxially arranged, the Hopkinson bars (4) for striking the rock sample blast holes (8) comprise incidence bars, the rock sample blast holes (8) are hemispherical in structure, the diameter of each rock sample blast hole (8) is slightly larger than that of the incidence bar of each Hopkinson bar (4), and each rock sample blast hole (8) is provided with a section of cylindrical path.
3. The test device for simulating the damage characteristics of the inter-borehole layer surrounding rock according to claim 1, wherein the test device is characterized by: one side of the baffle (9) is conical, and the fluid (10) is fluid with the bulk modulus of elasticity not less than 2.18 GPa.
4. The test device for simulating the damage characteristics of the inter-borehole layer surrounding rock according to claim 1, wherein the test device is characterized by: the pouring die (6) comprises end dies (601) at two ends, a surrounding die plate (602) with a U-shaped structure is arranged between the two end dies (601), a partition plate (603) is arranged on the surrounding die plate (602), a side film (604) is arranged between the two end dies (601), and an arc plate (605) is arranged on the side film (604).
5. The test device for simulating the damage characteristics of the inter-borehole layer surrounding rock according to claim 1, wherein the test device is characterized by: the two Hopkinson bars (4) are provided with strain gauges (7), the two strain gauges (7) are connected with a dynamic signal acquisition instrument (2), the dynamic signal acquisition instrument (2) is connected with a computer (1), and one side of a rock mass sample (11) is provided with a high-speed photographic instrument (3) and an infrared velocimeter (5).
6. The test method of the test device for simulating the damage characteristics of the inter-borehole layer surrounding rock according to any one of claims 1 to 5, which comprises the following steps: the method comprises the following steps: s1, preparation before experiment: aligning two Hopkinson bars (4), wherein the two Hopkinson bars (4) respectively comprise an incident bar and a transmission bar, a rock mass sample (11) is manufactured, the Hopkinson bars (4) of the incident bar are opposite to a rock sample blast hole (8) and are clung to an orifice baffle (9), and the other Hopkinson bar (4) is clung to the other side of the rock mass sample (11);
s2, installing an infrared velocimeter (5), adjusting the height to enable the infrared velocimeter (5) to be positioned at the position of an impact rod impacting an incident rod, measuring the impact speed, installing a high-speed camera (3) on a bracket (12), adjusting the angle of the instrument to enable the high-speed camera (3) to be opposite to a rock sample, and recording deformation characteristics of surrounding rock under the action of load;
s3, calculating the longitudinal wave velocity in the rock mass sample (11) and the damage variable of the rock mass sample (11), and calculating the relation between the damage variable and the acoustic wave velocity of the rock mass before and after damage;
s4, judging the standard of the rock mass sample (11) affected by blasting according to the wave speed change by a drilling acoustic observation method;
s5, calculating the shock wave pressure and detonation pressure required by macroscopic damage of a point which is located at any distance from the center of the blast hole in the rock mass sample (11); acquiring damage characteristics of a rock mass sample (11) in a blasting environment;
and S6, determining the farthest explosive distance of macroscopic damage at a certain position in the rock sample under the conditions of different explosive types, charging diameters and blast hole diameters when the critical damage variables are different.
7. The test method of any test device for simulating the damage characteristics of the inter-borehole layer surrounding rock according to claim 6, which is characterized by comprising the following steps: in S3, according to the wave theory, the wave velocity of the longitudinal wave propagating in the continuous, uniform, isotropic elastic medium can be expressed as:
in (a): v (V) p Is the longitudinal wave velocity of rock mass E d Is the dynamic elastic modulus of the rock mass, ρ is the density of the rock mass, v d Is a dynamic poisson ratio;
rock is generally considered an isotropically damaged material when the dominant feature size of the rock mass structural face is much smaller than the stress wave wavelength. Assuming that the damage development results in a decrease in the elastic modulus of the rock, the damage variable is calculated as:
wherein: d is injury; e (E) d The dynamic elastic modulus for damage;is the dynamic elastic modulus of the lossless rock;
the dynamic poisson ratio vd and the density ρ of the rock mass are kept unchanged before and after blasting, and the formula (2) is substituted into the formula (1) to obtain:
wherein: v (V) p The sonic wave velocity of the rock mass after being affected by the blasting;
the relation between the damage variable of the rock mass and the sonic wave velocity of the rock mass before and after damage is obtained by the formula (3):
8. the test method of any test device for simulating the damage characteristics of the inter-borehole layer surrounding rock according to claim 6, which is characterized by comprising the following steps: s4, the wave speed change rate is not large15%, no or little effect; the wave speed change rate is more than 10% but not more than 15%, the influence is slight, and the wave speed change rate is more than 15%, and the influence is caused. From equations (3) and (4), two critical values affected by blasting, namely, a critical damage variable D when the wave velocity change rate is 10%, can be calculated lim The method comprises the steps of carrying out a first treatment on the surface of the When the wave velocity change rate is 15%, the critical damage variable D lim2。
9. The test method of any test device for simulating the damage characteristics of the inter-borehole layer surrounding rock according to claim 6, which is characterized by comprising the following steps: in S5, when the rock mass sample (11) is near an explosion source, the radial and circumferential stress amplitude values of a single Kong Baozha stress wave along with the distance decay law meet the following formula:
(σ r ) max ＝P(r/r d ) -α (5)；
wherein: (sigma) r ) max Sum (sigma) r ) max Radial maximum dynamic stress and circumferential maximum dynamic stress are respectively; p is the initial pressure of the shock wave transmitted into the rock; r is the distance from the center of the blast hole, r d The radius of the blast hole; alpha is the pressure decay coefficient, alpha is approximately 3 for the shock wave;lateral coefficient of stress wave for rock->In the region of action of the shock wave, < >>
Depending on the stress conditions, either tensile failure or compressive shear failure may be exhibited, and when the effective stress in the rock exceeds the failure strength of the rock, macroscopic deformation failure phenomena will occur, yielding crush zones and fracture zones that satisfy the following conditions:
(σ′ r ) max ≥(σ r ) max /(1-D lim )＝σ cd (compression zone) (7);
-(σ′ θ ) max ≥-(σ θ ) max /(1-D lim )＝σ td (fissure zone) (8);
wherein: (sigma' r ) max Sum (sigma ')' θ ) max The method is divided into radial and annular maximum effective stress respectively; sigma (sigma) cd Sum sigma td The uniaxial dynamic compression strength and the dynamic tensile strength of the rock are respectively;
according to the principle of acoustic approximation, the transmitted shock wave pressure P in the rock is:
detonation pressure P of blast hole 0 The method comprises the following steps:
wherein: ρ 0 Is the density of the explosive; d is the detonation velocity of the explosive; gamma is an isentropic index, and the isentropic index of the explosive gamma=3; n is the pressure increase coefficient when the explosive explosion product expands and collides with the wall of the gun hole, and n=10 is generally taken; l (L) e For axial coefficient of charge, take l in general e =1 to 1.41; k is the radial uncoupled coefficient of the charge,r d ，r c the radius of the blast hole and the radius of the medicine bag are respectively.
10. The test method of any test device for simulating the damage characteristics of the inter-borehole layer surrounding rock according to claim 6, which is characterized by comprising the following steps: in S6, the following formulas (13) and (14) can be obtained:D lim and D lim2 Substituting (5) to (8) to obtain：
D lim In the time-course of which the first and second contact surfaces,
D lim2 in the time-course of which the first and second contact surfaces,
the above formulas (15) to (18) calculate that the critical damage variables are D respectively lim And D lim2 And when the type, the charging diameter and the blast hole diameter of different explosives are determined, the furthest explosion center distance (r) of macroscopic damage to a certain position in the rock sample is obtained, and the damage characteristic of the rock sample in the explosion environment is obtained.
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