CN114608975A - System and method for testing dynamic II-type fracture toughness of rock - Google Patents
System and method for testing dynamic II-type fracture toughness of rock Download PDFInfo
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- 239000011435 rock Substances 0.000 title claims abstract description 123
- 238000012360 testing method Methods 0.000 title claims abstract description 112
- 238000000034 method Methods 0.000 title claims abstract description 23
- 230000005540 biological transmission Effects 0.000 claims abstract description 37
- 238000012545 processing Methods 0.000 claims abstract description 11
- 238000010521 absorption reaction Methods 0.000 claims abstract description 9
- 238000005520 cutting process Methods 0.000 claims abstract description 7
- 230000010354 integration Effects 0.000 claims description 3
- 238000010998 test method Methods 0.000 description 6
- 238000005259 measurement Methods 0.000 description 4
- 238000007656 fracture toughness test Methods 0.000 description 3
- TZCXTZWJZNENPQ-UHFFFAOYSA-L barium sulfate Chemical compound [Ba+2].[O-]S([O-])(=O)=O TZCXTZWJZNENPQ-UHFFFAOYSA-L 0.000 description 2
- 230000009286 beneficial effect Effects 0.000 description 2
- 230000007547 defect Effects 0.000 description 2
- 238000010586 diagram Methods 0.000 description 2
- 235000006629 Prosopis spicigera Nutrition 0.000 description 1
- 240000000037 Prosopis spicigera Species 0.000 description 1
- 238000012669 compression test Methods 0.000 description 1
- 238000013461 design Methods 0.000 description 1
- 238000011161 development Methods 0.000 description 1
- 238000011156 evaluation Methods 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 239000000463 material Substances 0.000 description 1
- 238000005065 mining Methods 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 230000000149 penetrating effect Effects 0.000 description 1
- 238000002360 preparation method Methods 0.000 description 1
- 238000010008 shearing Methods 0.000 description 1
- 230000003068 static effect Effects 0.000 description 1
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 1
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- G—PHYSICS
- G01—MEASURING; TESTING
- 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
- G01N3/30—Investigating strength properties of solid materials by application of mechanical stress by applying a single impulsive force, e.g. by falling weight
- G01N3/307—Investigating strength properties of solid materials by application of mechanical stress by applying a single impulsive force, e.g. by falling weight generated by a compressed or tensile-stressed spring; generated by pneumatic or hydraulic means
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N1/00—Sampling; Preparing specimens for investigation
- G01N1/28—Preparing specimens for investigation including physical details of (bio-)chemical methods covered elsewhere, e.g. G01N33/50, C12Q
- G01N1/286—Preparing specimens for investigation including physical details of (bio-)chemical methods covered elsewhere, e.g. G01N33/50, C12Q involving mechanical work, e.g. chopping, disintegrating, compacting, homogenising
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N1/00—Sampling; Preparing specimens for investigation
- G01N1/28—Preparing specimens for investigation including physical details of (bio-)chemical methods covered elsewhere, e.g. G01N33/50, C12Q
- G01N1/286—Preparing specimens for investigation including physical details of (bio-)chemical methods covered elsewhere, e.g. G01N33/50, C12Q involving mechanical work, e.g. chopping, disintegrating, compacting, homogenising
- G01N2001/2873—Cutting or cleaving
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N2203/00—Investigating strength properties of solid materials by application of mechanical stress
- G01N2203/0001—Type of application of the stress
- G01N2203/001—Impulsive
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N2203/00—Investigating strength properties of solid materials by application of mechanical stress
- G01N2203/003—Generation of the force
- G01N2203/0042—Pneumatic or hydraulic means
- G01N2203/0044—Pneumatic means
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N2203/00—Investigating strength properties of solid materials by application of mechanical stress
- G01N2203/02—Details not specific for a particular testing method
- G01N2203/026—Specifications of the specimen
- G01N2203/0262—Shape of the specimen
Abstract
The invention discloses a system and a method for testing dynamic II-type fracture toughness of rocks, wherein the testing system comprises an operating platform, a supporting base, a cylinder, an impact rod, an incident rod, a transmission rod, a Z-shaped rock test piece and an absorption rod; the air cylinder is arranged on the operating platform, the output end of the air cylinder is provided with an impact rod, the supporting base is arranged above the operating platform, the supporting base on one side of the impact rod is sequentially provided with an incident rod, a transmission rod and an absorption rod, the end surface of the incident rod close to the impact rod is provided with a shaper, and a Z-shaped rock test piece is clamped between the incident rod and the transmission rod; the incident rod and the transmission rod are both provided with strain gauges, and the strain gauges are connected with a data acquisition and processing system through shielded signal lines; the Z-shaped rock test piece is obtained by respectively cutting off half cylinders with the same size in the diagonal direction of a cylindrical rock, and the middle part of the Z-shaped rock test piece is provided with a central crack which penetrates through the Z-shaped rock test piece along the horizontal diameter direction.
Description
Technical Field
The invention belongs to the field of rock mechanics and engineering, and particularly relates to a system and a method for testing dynamic II-type fracture toughness of a rock.
Background
In mining, water conservancy, geotechnical engineering and other projects, rock dynamic II type, namely in-plane shear type fracture is one of important modes of rock instability damage, so rock dynamic II type fracture toughness is an important index for structural design and safety evaluation of rock engineering. Currently, the International Society for Rock Mechanics (ISRM) does not recommend a test method suitable for dynamic type II fracture toughness of rock, and most of the existing test methods apply the test method for static type II fracture toughness of rock to a hopkinson Strut (SHPB) test system, for example: the method comprises the following steps of asymmetric grooving short beam compression test, perforation shear test, double-faced hat-shaped shear test, central straight crack Brazilian disc test and the like to obtain the dynamic II-type fracture toughness of the rock.
In the process of a rock dynamic test, the existing test method for rock dynamic II-type fracture toughness mainly has four defects, so that the measurement precision of the rock dynamic II-type fracture toughness is reduced and the method cannot be popularized. Firstly, stress concentration is easily caused at the loading end part of the rock test piece, so that the rock test piece is damaged in advance; secondly, the preparation of the rock test piece is complex, the processing time is long and the cost is high; thirdly, when the rock test piece is fractured, the I-type or open-type stress intensity factor at the end part of the prefabricated crack is larger, so that the measurement precision of the dynamic II-type fracture toughness is low, the crack through mode is disordered, and the secondary crack is seriously developed; fourthly, the rock test piece clamp can easily change the stress wave propagation principle of the SHPB test system, and is not beneficial to meeting the stress balance condition required by the rock dynamic test. Therefore, the system and the method for testing the dynamic II-type fracture toughness of the rock are designed, and the system and the method have important significance for improving the measurement precision and the test efficiency of the dynamic II-type fracture toughness of the rock.
Disclosure of Invention
The invention aims to overcome the defects of complex test piece processing, poor dynamic test stress balance and low measurement precision in the existing rock dynamic II-type fracture toughness test method, and provides a rock dynamic II-type fracture toughness test system and a rock dynamic II-type fracture toughness test method.
The purpose of the invention is realized by the following technical scheme:
a test system for rock dynamic II-type fracture toughness comprises an operation platform, a support base, a cylinder, an impact rod, an incidence rod, a transmission rod, a Z-shaped rock test piece and an absorption rod; the air cylinder is arranged on the operating platform, the output end of the air cylinder is provided with an impact rod, the supporting base is arranged above the operating platform, the supporting base on one side of the impact rod is sequentially provided with an incident rod, a transmission rod and an absorption rod, the end surface of the incident rod close to the impact rod is provided with a shaper, and the Z-shaped rock test piece is clamped between the incident rod and the transmission rod; the incident rod and the transmission rod are both provided with strain gauges, and the strain gauges are connected with a data acquisition and processing system through shielded signal lines;
the Z-shaped rock test piece is obtained by respectively cutting off half cylinders with the same size in the diagonal direction of a cylindrical rock, and the middle part of the Z-shaped rock test piece is provided with a central crack which penetrates through the Z-shaped rock test piece along the horizontal diameter direction.
Further, the length of the cut semi-cylinder is used as a dislocation distance, and the ratio of the height of the cylindrical rock test piece to the diameter of the cylindrical rock test piece is called a height-diameter ratio and is 0.5-1.5; the ratio of the dislocation distance to the height of the cylindrical rock test piece is called a dislocation ratio, and the value is 0.18-0.3.
Furthermore, the ratio of the length of the central crack to the height of the cylindrical rock test piece is called a crack ratio, and the value is 0.1-0.4.
Furthermore, the width of the central crack ranges from 0.5 mm to 2 mm.
A method for testing dynamic type II fracture toughness of rocks based on a system for testing dynamic type II fracture toughness of rocks according to claim 1, comprising the following steps:
(1) clamping a Z-shaped rock test piece between an incident rod and a transmission rod, enabling the top end of the Z-shaped rock test piece to be tightly attached to the rear end face of the incident rod, and enabling the bottom end of the Z-shaped rock test piece to be tightly attached to the front end face of the transmission rod;
(2) compressed air in the air cylinder is used for driving the impact rod to impact the front end face of the incident rod, so that impact load is applied to the Z-shaped rock test piece;
(3) by utilizing the strain gauges stuck on the incident rod and the transmission rod, the data acquisition and processing system records the incident strain, the transmission strain and the reflection strain of the Z-shaped rock test piece in the dynamic II-type fracture process, when the sum of the incident strain and the transmission strain is equal to the reflection strain, the two ends of the Z-shaped rock test piece meet the stress balance, and the impact load P (t) can be calculated according to the following formula:
in the formula: e and A are the elastic modulus and the cross-sectional area, ε, of the incident rod and the transmission rod, respectivelyI(t)、εR(t) and εT(t) incident strain signals, reflected strain signals and transmitted strain signals which are acquired by the strain gauge respectively;
(4) substituting the impact load P (t) into the following formula to calculate the type I and type II stress intensity factors of the Z-shaped rock test piece:
in the formula: pmaxFor peak impact load, R is the radius of the zigzag rock specimen, a is half the length of the central crack, YIAnd YIIRespectively a type I and a type II geometric factor, Y, of the Z-shaped rock test pieceIAnd YIIIs composed of JAnd (4) determining a finite element program of an integral method.
Compared with the prior art, the technical scheme of the invention has the following beneficial effects:
1. the Z-shaped rock test piece containing the central crack has the advantages of simple manufacturing process and low processing cost, and is easy to popularize and use for measuring the dynamic II-type fracture toughness of the rock.
2. The semicircular end part of the Z-shaped rock test piece can be conveniently and quickly attached to a Hopkinson pressure bar test system, namely the end surfaces of the incident rod and the transmission rod in the test system, so that the stress concentration of the end part is not easy to cause, and the rock test piece is prevented from being damaged in advance in the test process.
3. The test method does not need an additional test piece clamp, does not change the stress wave propagation principle of an SHPB test system, is easier to meet the stress balance condition required by a dynamic test, saves the test time and improves the test efficiency.
4. The impact load applied by the testing method is taken as the shearing force directly acting on the surface of the front edge of the crack surface, so that the I-type stress intensity factor of the end part of the crack can be effectively reduced, the development of the secondary crack can be weakened, and the testing precision of the dynamic II-type fracture toughness of the rock can be improved.
Drawings
FIG. 1 is a schematic perspective view of a Z-shaped rock test piece in an embodiment of the invention.
FIG. 2 is a schematic front view structure diagram of a Z-shaped rock test piece in the embodiment of the invention.
FIG. 3 is a schematic structural diagram of a test system according to an embodiment of the present invention.
FIG. 4 is a graph showing the geometrical factor Y of a zigzag rock specimen under different dislocation ratios and crack ratios when the aspect ratio is 1IAnd YIIFigure (a).
Reference numerals: 1-central crack, 2-cylinder, 3-impact rod, 4-shaper, 5-incidence rod, 6-strain gauge, 7-Z-shaped rock test piece, 8-transmission rod, 9-absorption rod, 10-operation platform, 11-support base, 12-shielding signal line, and 13-data acquisition and processing system.
Detailed Description
The invention is described in further detail below with reference to the figures and specific examples. It should be understood that the specific embodiments described herein are merely illustrative of the invention, and it should be understood that the terms "upper", "lower", "front", "rear", "left", "right", "top", "bottom", etc. indicate orientations or positional relationships that are based on the orientations or positions shown in the drawings, which are used for convenience and simplicity in describing the patent and are not intended to limit the invention.
Referring to fig. 1 to 3, the embodiment provides a test system for dynamic II-type fracture toughness of rock based on a hopkinson pressure bar test system, which includes an operation platform 10, a support base 11, a cylinder 2, an impact bar 3, an incident bar 5, a transmission bar 8, a zigzag rock test piece 7, and an absorption bar 9; the cylinder 2 is arranged on an operation platform 10, an impact rod 3 is arranged at the output end of the cylinder 2, a support base 11 is arranged above the operation platform 10, an incident rod 5, a transmission rod 8 and an absorption rod 9 are sequentially arranged on the support base 11 on one side of the impact rod 3, a shaper 4 is arranged on the end face of the incident rod 5 close to the impact rod 3 and used for improving loading waveforms, and a Z-shaped rock test piece 7 is clamped between the incident rod 5 and the transmission rod 8; the middle parts of the incident rod 5 and the transmission rod 8 are both provided with strain gauges 6, and the strain gauges 6 are connected with a data acquisition and processing system 13 through shielding signal lines 12;
the zigzag rock test piece 7 in this embodiment is obtained by cutting off half cylinders of the same size from the diagonal direction of a cylindrical rock, respectively, and the middle part of the zigzag rock test piece 7 is provided with a central crack 1 penetrating through the zigzag rock test piece in the horizontal diameter direction.
Referring to fig. 1 to 3, in particular, the method for testing the dynamic type II fracture toughness of the rock based on the above system in this embodiment includes the following specific steps:
(1) preparing a Z-shaped rock test piece for rock dynamic II-type fracture toughness, wherein the Z-shaped rock test piece is cut from cylindrical rocks along the horizontal diameter directions of the top surface and the bottom surface respectively towards the axial direction, the axial direction of the cylindrical rocks is taken as the horizontal direction, and the cutting lengths are the same, namely the dislocation distance l of the Z-shaped rock test piece; cutting the top end of the cylindrical rock into a semi-cylindrical end part along a vertical downward direction after the cylindrical rock is cut to a dislocation distance, cutting the bottom end of the cylindrical rock into a semi-cylindrical end part along a vertical upward direction, dislocating the two semi-cylindrical end parts up and down to enable the whole test piece to be Z-shaped, and enabling the central crack 1 to be located at the middle axial position of the Z-shaped rock test piece and penetrate through the test piece along the horizontal diameter direction;
(2) the ratio of the height h to the diameter D of the Z-shaped rock test piece is called as the height-diameter ratio, the height-diameter ratio is 1, the diameter D of the Z-shaped rock test piece is equal to or smaller than the diameters of the incident rod 5 and the transmission rod 8, and the incident rod 5 and the transmission rod 8 are the same in diameter and same in material;
(3) the ratio of the dislocation distance l of the Z-shaped rock test piece 7 to the height h of the Z-shaped rock test piece is called a dislocation ratio, and the value is 0.25;
(4) the ratio of the length 2a of the central crack 1 to the height h of the Z-shaped rock test piece is called a crack ratio and is 0.3; the width of the central crack 1 is 1 mm;
(5) clamping a Z-shaped rock test piece between an incident rod and a transmission rod, enabling the top end of the Z-shaped rock test piece to be tightly attached to the rear end face of the incident rod, and enabling the bottom end of the Z-shaped rock test piece to be tightly attached to the front end face of the transmission rod;
(6) compressed air in the air cylinder is used for driving the impact rod to impact the front end face of the incident rod, so that impact load is applied to the Z-shaped rock test piece;
(7) by utilizing the strain gauges stuck on the incident rod and the transmission rod, the data acquisition and processing system records the incident strain, the transmission strain and the reflection strain of the Z-shaped rock test piece in the dynamic II-type fracture process, when the sum of the incident strain and the transmission strain is equal to the reflection strain, the two ends of the Z-shaped rock test piece meet the stress balance, and the impact load P (t) can be calculated according to the following formula:
in the formula: e and A are the elastic modulus and the cross-sectional area of the incident rod and the transmission rod, respectively, εI(t)、εR(t) and εT(t) incident strain signals, reflected strain signals and transmitted strain signals which are acquired by the strain gauge respectively;
(8) substituting the impact load P (t) into the following formula to calculate the type I and type II stress intensity factors of the Z-shaped rock test piece:
in the formula: pmaxFor peak impact load, R is the radius of the zigzag rock specimen, a is half the length of the central crack, YIAnd YIIRespectively a type I and a type II geometric factor, Y, of the Z-shaped rock test pieceIAnd YIIDetermined by the finite element program of the J integration method.
(9) Determining Y according to a finite element program of a J integration method corresponding to the dislocation ratio value in the step (3) and the crack ratio value in the step (4)IAnd YIIY is obtained as shown in FIG. 3I≈0，YII5.221, calculating the rock dynamic type II fracture toughness according to the following formula:
wherein Y is determined by a finite element program of J-integration methodIAnd YIIThe contents of (a) are described in the patent application entitled "test piece and test method for rock type III dynamic fracture toughness" having application number "201610873898.2.
The present invention is not limited to the above-described embodiments. The foregoing description of the specific embodiments is intended to describe and illustrate the technical solutions of the present invention, and the above specific embodiments are merely illustrative and not restrictive. Those skilled in the art can make many changes and modifications to the invention without departing from the spirit and scope of the invention as defined in the appended claims.
Claims (5)
1. A test system for dynamic II-type fracture toughness of rocks is characterized by comprising an operating platform, a supporting base, a cylinder, an impact rod, an incident rod, a transmission rod, a Z-shaped rock test piece and an absorption rod; the air cylinder is arranged on the operating platform, the output end of the air cylinder is provided with an impact rod, the supporting base is arranged above the operating platform, the supporting base on one side of the impact rod is sequentially provided with an incident rod, a transmission rod and an absorption rod, the end surface of the incident rod close to the impact rod is provided with a shaper, and the Z-shaped rock test piece is clamped between the incident rod and the transmission rod; the incident rod and the transmission rod are both provided with strain gauges, and the strain gauges are connected with a data acquisition and processing system through shielded signal lines;
the Z-shaped rock test piece is obtained by respectively cutting off half cylinders with the same size in the diagonal direction of a cylindrical rock, and the middle part of the Z-shaped rock test piece is provided with a central crack which penetrates through the Z-shaped rock test piece along the horizontal diameter direction.
2. The system for testing the dynamic II-type fracture toughness of the rock according to claim 1, wherein the length of the cut semi-cylinder is taken as a dislocation distance, and the ratio of the height of the cylindrical rock test piece to the diameter of the cylindrical rock test piece is called as a height-to-diameter ratio and is 0.5-1.5; the ratio of the dislocation distance to the height of the cylindrical rock test piece is called a dislocation ratio, and the value is 0.18-0.3.
3. The system for testing the dynamic type II fracture toughness of the rock according to claim 1, wherein the ratio of the length of the central crack to the height of the cylindrical rock test piece is called a crack ratio and is 0.1-0.4.
4. The system for testing the dynamic type II fracture toughness of the rock according to claim 1, wherein the width of the central crack ranges from 0.5 mm to 2 mm.
5. A method for testing dynamic type II fracture toughness of rock, which is based on the system for testing dynamic type II fracture toughness of rock in claim 1, and is characterized by comprising the following steps:
(1) clamping a Z-shaped rock test piece between an incident rod and a transmission rod, enabling the top end of the Z-shaped rock test piece to be tightly attached to the rear end face of the incident rod, and enabling the bottom end of the Z-shaped rock test piece to be tightly attached to the front end face of the transmission rod;
(2) compressed air in the air cylinder is used for driving the impact rod to impact the front end face of the incident rod, so that impact load is applied to the Z-shaped rock test piece;
(3) by utilizing the strain gauges adhered to the incident rod and the transmission rod, the data acquisition and processing system records the incident strain, the transmission strain and the reflection strain of the Z-shaped rock test piece in the dynamic II-type fracture process, when the sum of the incident strain and the transmission strain is equal to the reflection strain, the two ends of the Z-shaped rock test piece meet the stress balance, and the impact load P (t) can be calculated according to the following formula:
in the formula: e and A are the elastic modulus and the cross-sectional area, ε, of the incident rod and the transmission rod, respectivelyI(t)、εR(t) and εT(t) incident strain signals, reflected strain signals and transmitted strain signals which are acquired by the strain gauge respectively;
(4) substituting the impact load P (t) into the following formula to calculate the type I and type II stress intensity factors of the Z-shaped rock test piece:
in the formula: pmaxFor peak impact load, R is the radius of the Z-shaped rock specimen, a is the center crack lengthHalf of (A), YIAnd YIIRespectively a type I and a type II geometric factor, Y, of the Z-shaped rock test pieceIAnd YIIDetermined by the finite element program of the J integration method.
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Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH05135181A (en) * | 1991-11-08 | 1993-06-01 | Mitsubishi Electric Corp | Abnormality detection device |
| JP2010193178A (en) * | 2009-02-18 | 2010-09-02 | Olympus Corp | Unit, method and program for processing image |
| CN106404562A (en) * | 2016-10-08 | 2017-02-15 | 四川大学 | Test piece for testing rock II-type dynamic fracture toughness and testing method |
| CN106932253A (en) * | 2017-04-17 | 2017-07-07 | 四川大学 | Test the test specimen component and method of testing of rock I II mixed mode dynamic fracture toughness |
| CN113504131A (en) * | 2021-07-09 | 2021-10-15 | 中国矿业大学 | Test system and test method for testing II-type dynamic fracture toughness of rock under different normal stresses |
-
2022
- 2022-02-28 CN CN202210189539.0A patent/CN114608975A/en active Pending
Patent Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH05135181A (en) * | 1991-11-08 | 1993-06-01 | Mitsubishi Electric Corp | Abnormality detection device |
| JP2010193178A (en) * | 2009-02-18 | 2010-09-02 | Olympus Corp | Unit, method and program for processing image |
| CN106404562A (en) * | 2016-10-08 | 2017-02-15 | 四川大学 | Test piece for testing rock II-type dynamic fracture toughness and testing method |
| CN106932253A (en) * | 2017-04-17 | 2017-07-07 | 四川大学 | Test the test specimen component and method of testing of rock I II mixed mode dynamic fracture toughness |
| CN113504131A (en) * | 2021-07-09 | 2021-10-15 | 中国矿业大学 | Test system and test method for testing II-type dynamic fracture toughness of rock under different normal stresses |
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