CN111366461B - Method for testing tensile strength of rock - Google Patents
Method for testing tensile strength of rock Download PDFInfo
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- CN111366461B CN111366461B CN202010284609.1A CN202010284609A CN111366461B CN 111366461 B CN111366461 B CN 111366461B CN 202010284609 A CN202010284609 A CN 202010284609A CN 111366461 B CN111366461 B CN 111366461B
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- G—PHYSICS
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- G01N3/00—Investigating strength properties of solid materials by application of mechanical stress
- G01N3/08—Investigating strength properties of solid materials by application of mechanical stress by applying steady tensile or compressive forces
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- 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
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- G01N2203/00—Investigating strength properties of solid materials by application of mechanical stress
- G01N2203/0014—Type of force applied
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- G01N2203/00—Investigating strength properties of solid materials by application of mechanical stress
- G01N2203/0098—Tests specified by its name, e.g. Charpy, Brinnel, Mullen
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- G01N2203/00—Investigating strength properties of solid materials by application of mechanical stress
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- G01N2203/025—Geometry of the test
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- G01N2203/00—Investigating strength properties of solid materials by application of mechanical stress
- G01N2203/02—Details not specific for a particular testing method
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- 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
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- G01N2203/00—Investigating strength properties of solid materials by application of mechanical stress
- G01N2203/02—Details not specific for a particular testing method
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Abstract
The invention discloses aThe test method for the tensile strength of the rock comprises the following steps: the method comprises the following steps: collecting mechanical parameters of a real rock sample; step two: establishing a test piece model with the length of l, the height of h, the thickness of t and the diameter of d of a cylindrical through hole dug in the center, calculating the relation between the maximum tensile stress and the thickness of the test piece model under the action of the symmetrical compressive stress, and finding the thickness-diameter ratio m of the test piece model corresponding to the maximum tensile stress k (ii) a Step three: establishing a thickness-diameter ratio of m k Calculating the maximum tensile stress under the action of different symmetrical compressive stresses, and determining a tensile strength correction equation; step four: taking a real rock sample to process the thickness-diameter ratio of m k And substituting the compressive stress borne by the sample when the sample cracks into a tensile strength correction equation to obtain the tensile strength of the real rock sample. The invention has the beneficial effects that: the equipment and the sample are simple, the test method is easy to implement, the sample is easy to prepare, the calculation formula of the tensile strength is simple, the test result is reliable, and the method is favorable for practical application.
Description
Technical Field
The invention relates to the technical field of rock mechanics, in particular to a method for testing tensile strength of a rock.
Background
The tensile strength of rock is the maximum tensile stress that a rock sample can bear under the action of tensile load, and the value of the tensile strength is far lower than the compressive strength of the rock, so that rock engineering is usually destroyed from a region with larger tensile stress. The determination of the tensile strength of the rock has great significance for determining the engineering design and construction scheme of the rock mass and ensuring the engineering safety.
The rock tensile failure test is divided into a direct tensile test and an indirect tensile test. Although the direct rock tensile test is more in line with the actual tensile condition of the rock, the direct rock tensile test is difficult to implement due to the defects that the test piece is difficult to prepare, stress concentration is easy to occur at the contact part of the clamp and the test piece, eccentricity may exist in the tensile process and the like. Limited by the disadvantages of the direct tensile test of rock, the indirect tensile test of rock represented by the barcy test emerges. For Brazilian tests, the defects of stress concentration, eccentric loading and the like at the loading point still exist, so that the test result is always questioned by academia.
Disclosure of Invention
The invention aims to overcome the defects of the prior art and provide a simple and effective test method for rock tensile strength, so as to avoid the technical difficulty of direct rock tensile test and Brazilian test, and accurately measure the rock tensile strength to obtain the true value of the rock tensile strength.
The purpose of the invention is realized by the following technical scheme: a test method for rock tensile strength comprises the following steps:
the method comprises the following steps: collecting mechanical parameters of a real rock sample, wherein the mechanical parameters comprise elastic modulus E, poisson ratio mu, volume modulus K and shear modulus G. The acquisition method comprises the following steps: and (4) carrying out an indoor test, testing the elastic modulus and the Poisson ratio of the real rock sample, and calculating the volume modulus and the shear modulus. Specifically, a real rock sample to be measured is taken to carry out an indoor rock deformation test, the elastic modulus E and the Poisson ratio mu of the rock sample are measured, and the elastic modulus E and the Poisson ratio mu are substituted into an elastic mechanics formula to respectively calculate the volume modulus K and the shear modulus G of the rock sample.
Wherein, the volume modulus K and the shear modulus G of the rock sample can be respectively expressed as: k = E/3 (1-2 μ), G = E/2 (1 + μ), where E is the rock-like elastic modulus and μ is the poisson's ratio of the rock-like.
Step two: according to the collected mechanical parameters of the real rock sample, a test piece model with the length of l, the height of h, the thickness of t and a cylindrical through hole with the diameter of D and extending along the thickness direction is built by using numerical software FLAC3D (Fast Lagrangian Analysis of Continua), the center is excavated, the relation between the maximum tensile stress and the thickness of the test piece model under the action of symmetrical compressive stress is calculated by using the numerical software, and the thickness-diameter ratio m of the test piece model corresponding to the maximum tensile stress is found k And the thickness-diameter ratio is the ratio of the thickness t of the test piece model to the diameter d of the cylindrical through hole. The method comprises the following specific steps:
according to the collected mechanical parameters of the real rock sample, a test piece model with the length l =24cm and the height h =24cm is established by using numerical software FLAC3D, and the test piece model is arrangedA cylindrical hole with the diameter d =3cm and the thickness the same as that of the test piece model is excavated in the model center, namely the cylindrical hole extends along the thickness direction of the test piece model and penetrates through the test piece model, and the thickness of the test piece model is respectively set as t 1 ＝0.3cm，t 2 ＝0.6cm，…，t 19 ＝5.7cm，t 20 If the thickness-diameter ratio of the test piece model is not less than 6.0cm, the thickness-diameter ratio of the test piece model is m i (thickness t) i The ratio of the diameter d of the central circular hole) is m 1 ＝0.1，m 2 ＝0.2，…，m 19 ＝1.9，m 20 =2.0. Applying vertical compressive stress f on the upper and lower top surfaces of the test piece model i Are respectively f 1 ＝2MPa、f 2 And (5) =3MPa, and performing elasticity solution.
According to the existing theoretical results of the elastic mechanics, when the thin plate with the round hole is subjected to symmetrical pressure, the maximum tensile stress appears around the round hole at the position close to the load acting end, the direction of the maximum tensile stress is perpendicular to the stress direction of the plate, namely the horizontal stress of the test piece model is the tensile stress, and the maximum horizontal stress is the maximum tensile stress. Respectively extracting m with different thickness-diameter ratios i The maximum horizontal stress after the test piece model calculation
Calculating the ratio of the maximum horizontal stress to the compressive stress applied by the test piece model
Drawing sigma xmax F-m plot of
Thickness-diameter ratio m of test piece corresponding to medium maximum value k 。
Step three: according to the mechanical parameters of the collected real rock sample, a numerical software FLAC3D is utilized to establish a test piece model with the length of l, the height of h, the thickness of t and a cylindrical through hole which extends along the thickness direction and has the diameter of D and is excavated at the center, and the thickness-diameter ratio of the test piece model is m k Calculating the maximum tensile stress of the test piece model under the action of different symmetrical compressive stresses by using numerical software FLAC3D, wherein the thickness-diameter ratio of the test piece model is m obtained in the second step k And fitting a relation equation of the maximum tensile stress and the applied compressive stress to determine a tensile strength correction equation. The method comprises the following specific steps:
according to the acquired mechanical parameters of the real rock sample, a test piece model with the length l =24cm and the height h =24cm is established by using numerical software FLAC3D, a cylindrical hole with the diameter D =3cm and the thickness the same as that of the test piece model is excavated in the center of the test piece model, namely the cylindrical hole extends and penetrates along the thickness direction of the test piece model, and the thickness-diameter ratio of the test piece model is m obtained in the step two k . Applying vertical compressive stress f on the upper and lower surfaces of the test piece model j Are respectively set to f 1 ＝1.0MPa，f 2 ＝1.5MPa，…，f 9 ＝5.0MPa，f 10 Respectively performing elastic solution at a pressure of 5.5MPa, and extracting different compressive stress loads f j Maximum horizontal stress calculated by test piece model under action
Drawing sigma xmax Fitting of σ to f-m plot xmax The equation for f is: sigma xmax = af + b, where a, b are constants obtained by fitting. Equation σ xmax And the = af + b is the tensile strength correction equation of the rock sample.
Step four: according to the thickness-diameter ratio m of the test piece determined by using numerical software to calculate k Taking a real rock sample, processing the rock sample into a cylindrical through hole with the length of l, the height of h, the thickness of t, the center of d and the diameter of d, wherein the cylindrical through hole extends along the thickness direction, and the thickness-diameter ratio of m k The uniaxial compression test is carried out on the sample to be tested, the tensile strength of the real rock sample is obtained by substituting the compressive stress borne by the sample in the tensile strength correction equation, and the method specifically comprises the following steps:
taking a real rock sample, processing the real rock sample into a sample to be measured with the length l =24cm and the height h =24cm, excavating a cylindrical hole with the diameter d =3cm and the thickness same as the thickness of the sample in the center of the sample, namely, the cylindrical hole extends along the thickness direction of the sample and penetrates through the sample, and taking the thickness-diameter ratio of the sample as m obtained in the step two k When the thickness of the sample is t = m k d. Placing the rock sample on a testing machine for singlesAnd (5) performing a shaft compression test, and observing the rock sample destruction process. If the force applied to the testing machine is F when the rock sample cracks, the corresponding applied compressive stress on the test sample is F = F/lt, and the tensile strength of the rock sample can be expressed as sigma by combining the tensile strength correction equation of the rock sample t = af + b, where σ t The tensile strength of the rock.
Further preferably, in order to avoid the influence of the loading boundary on the stress around the circular hole, the ratio of the length l and the height h of the test piece model or the test sample to the diameter d of the central circular hole satisfies that l/d is more than or equal to 8 and h/d is more than or equal to 8.
Further preferably, when determining the thickness-diameter ratio of the test piece corresponding to the maximum tensile stress, a plurality of levels of vertical compressive stress f can be adopted i Performing elasticity calculations, i.e. f i Are respectively f 1 ＝2MPa、f 2 ＝3MPa、…、f i ＝nMPa,n＞3。
Further, when the actual rock sample fracture initiation pressure is determined, a high-power camera can be used for recording the rock sample damage process, and the rock sample fracture initiation position and time can be accurately specified.
The invention has the following advantages:
the equipment and the sample used by the invention are simple, the test method is easy to implement, the sample is easy to prepare, the calculation formula of the tensile strength is simple, the test result is reliable, and the invention is beneficial to practical application.
The invention is based on the theoretical achievement of elastic mechanics, the maximum horizontal stress is the maximum tensile stress position, and the sample cracking point can be ensured to be the maximum tensile stress point.
The method fully considers the influence of the thickness of the sample on the result, and obtains a correction formula of the maximum tensile stress around the hole when the thin plate with the round hole in the elastic mechanics is subjected to the symmetric pressure through numerical calculation, so that the obtained result is more accurate.
The rock test piece used in the method has simple processing technology and is beneficial to ensuring the consistency of test results.
The rock test piece used in the method has a regular shape, is convenient to load, and has small test interference and small test result discreteness.
The rock tensile strength obtained by the method is simple in calculation formula and is beneficial to practical application.
The invention skillfully utilizes the distribution rule of the stress around the hole when the thin plate with the round hole in the elastic mechanics is subjected to symmetrical pressure, can ensure that the maximum tensile stress occurs around the round hole near the load action end, and the rock sample is cracked at first in the area. The adopted sample is square outside and round inside, so that the application of load is facilitated, and the occurrence of stress concentration or eccentric loading at a loading point is avoided.
Drawings
FIG. 1 is a flow chart of the steps of the rock tensile strength testing method of the invention.
FIG. 2 is a schematic view of a test piece according to the present invention.
FIG. 3 is a diagram showing the distribution of stress around a hole when a thin plate with a circular hole is subjected to symmetrical pressure.
FIG. 4 is a graph showing the relationship between the thickness/diameter ratio and the maximum horizontal stress according to the embodiment.
FIG. 5 is a graph of the relationship between the applied load and the corresponding maximum horizontal stress dispersion point, and a fitted curve and an equation obtained in the embodiment.
Detailed Description
The invention is further described with reference to the following figures and embodiments:
as shown in FIG. 1, a method for testing tensile strength of rock comprises the following steps:
the method comprises the following steps: collecting mechanical parameters of a real rock sample, wherein the mechanical parameters comprise elastic modulus E, poisson ratio mu, volume modulus K and shear modulus G. The acquisition method comprises the following steps: and (4) performing an indoor test, testing the elastic modulus and Poisson's ratio of the real rock sample, and calculating the bulk modulus and the shear modulus. Specifically, a real rock sample to be measured is taken to carry out an indoor rock deformation test, the elastic modulus E and the Poisson ratio mu of the rock sample are measured, and the elastic modulus E and the Poisson ratio mu are substituted into an elastic mechanics formula to respectively calculate the volume modulus K and the shear modulus G of the rock sample.
Wherein, the volume modulus K and the shear modulus G of the rock sample can be respectively expressed as: k = E/3 (1-2 μ), G = E/2 (1 + μ), where E is the rock sample elastic modulus and μ is the Poisson's ratio of the rock sample
In this example, the elastic modulus E =10000MPa and poisson ratio μ =0.25 of the rock sample are measured, and the volume modulus K =6666.67MPa and the shear modulus G =4000MPa of the rock sample are calculated.
Step two: according to the collected mechanical parameters of the real rock sample, a test piece model with the length of l, the height of h, the thickness of t and a cylindrical through hole which extends along the thickness direction and has the diameter of d is excavated at the center, the relation between the maximum tensile stress of the test piece model under the action of the symmetrical compressive stress and the thickness of the test piece model is calculated by using numerical software, and the thickness-diameter ratio m of the test piece model corresponding to the maximum tensile stress is found k And the thickness-diameter ratio is the ratio of the thickness t of the test piece model to the diameter d of the cylindrical through hole. In order to avoid the influence of the loading boundary on the stress around the circular hole, the ratio of the length l and the height h of the test piece model to the diameter d of the central circular hole meets the condition that l/d is more than or equal to 8 and h/d is more than or equal to 8.
In this embodiment, a test piece model with a length l =24cm and a height h =24cm is established by using numerical software FLAC3D, a cylindrical hole with a diameter D =3cm and the same thickness as that of the test piece model is excavated in the center of the test piece model, namely, the cylindrical hole extends along the thickness direction of the test piece and penetrates through the test piece, and the thicknesses of the test piece model are respectively set as t 1 ＝0.3cm，t 2 ＝0.6cm，…，t 19 ＝5.7cm，t 20 =6.0cm. Thickness-diameter ratio m of test piece model i Are respectively m 1 ＝0.1，m 2 ＝0.2，…，m 19 ＝1.9，m 20 =2.0. As shown in fig. 2, vertical pressure is applied to the upper and lower top surfaces of the specimen model 3 by the upper indenter 1 and the lower indenter 2, and vertical compressive stress f is applied to the upper and lower top surfaces of the specimen model i Are respectively f 1 ＝2MPa、f 2 =3MPa, respectively performing elastic solution, and extracting m with different thickness-diameter ratios i Calculated maximum horizontal stress of the sample
Of course, it may also be preferred that multiple levels of vertical compressive stress f may be used i Performing elasticity calculations, i.e. f i Are respectively f 1 ＝2MPa、f 2 ＝3MPa、…、f i = nMPa, n > 3. By elastic mechanicsSome theoretical results show that when the thin plate with the round hole is subjected to symmetrical pressure, the maximum tensile stress is generated around the round hole close to the load acting end, and the direction of the maximum tensile stress is perpendicular to the direction of the stress of the plate. Therefore, the horizontal stress of the specimen model is tensile stress, and the maximum horizontal stress is maximum tensile stress, as shown in fig. 3. Calculating the ratio of the maximum horizontal stress to the compressive stress applied by the test piece model
Drawing sigma xmax The/f-m curve is shown in FIG. 4. Find out
Thickness-to-diameter ratio m of sample corresponding to medium maximum value k ＝1.2。
Step three: according to the mechanical parameters of the collected real rock sample, a test piece model with the length of l, the height of h, the thickness of t and a cylindrical through hole extending along the thickness direction and having the diameter of D is excavated in the center and is established by numerical software FLAC3D, and the thickness-diameter ratio of the test piece model is m k Calculating the maximum tensile stress of the test piece model under the action of different symmetrical compressive stresses by using numerical software FLAC3D, wherein the thickness-diameter ratio of the test piece model is m obtained in the second step k And fitting a relation equation of the maximum tensile stress and the applied compressive stress to determine a tensile strength correction equation. Similarly, in order to avoid the influence of the loading boundary on the stress around the circular hole, the ratio of the length l and the height h of the test piece model to the diameter d of the central circular hole meets the condition that l/d is more than or equal to 8 and h/d is more than or equal to 8.
In the embodiment, a test piece model with the length l =24cm and the height h =24cm is established by using numerical software FLAC3D, a cylindrical hole with the diameter D =3cm and the thickness the same as that of the sample is excavated in the center of the test piece model, namely the cylindrical hole extends along the thickness direction of the sample and penetrates through the sample, and the thickness-diameter ratio m of the test piece model is larger than that of the sample k =1.2. The vertical compressive stresses applied to the upper and lower surfaces of the specimen model are respectively set to f 1 ＝1.0MPa，f 2 ＝1.5MPa，…，f 9 ＝5.0MPa，f 10 Respectively performing elastic solution under the condition of not less than 5.5MPa, and extracting different stress loads f j Maximum horizontal stress calculated by test piece model under action
Drawing sigma xmax -f-dependence graph, as shown in FIG. 5, fitting σ xmax The equation for f is: sigma xmax =1.1434f-0.0039, equation σ xmax And the equation of modification of the tensile strength of the rock sample is set as 1.1434 f-0.0039.
Step four: according to the thickness-diameter ratio m of the test piece determined by using numerical software to calculate k Taking a real rock sample, processing the rock sample into a cylindrical through hole with the length of l, the height of h, the thickness of t, the center of d and the diameter of d, wherein the cylindrical through hole extends along the thickness direction, and the thickness-diameter ratio of m k And carrying out a uniaxial compression test on the sample to be tested, and substituting the compressive stress borne by the sample in the tensile strength correction equation to obtain the tensile strength of the real rock sample. Similarly, in order to avoid the influence of the loading boundary on the stress around the round hole, the ratio of the length l and the height h of the sample to the diameter d of the central round hole meets the condition that l/d is more than or equal to 8 and h/d is more than or equal to 8. Preferably, when determining the fracture initiation pressure of the real rock sample, a high power camera can be used for recording the damage process of the rock sample.
In the embodiment, the real rock sample is taken and processed into a sample to be measured with the length l =24cm and the height h =24cm, a cylindrical hole with the diameter d =3cm and the thickness the same as that of the sample is excavated in the center of the sample, and the thickness-diameter ratio of the sample is m k =1.2, thickness t =3.6cm of the sample. The rock sample is placed on a testing machine for uniaxial compression test, and the damage process of the rock sample is observed. The test shows that the force applied on the testing machine when the rock sample cracks is F =13.176kN, the corresponding applied compressive stress on the test sample is F =1.83MPa, and the tensile strength sigma of the rock sample can be obtained by combining the tensile strength correction equation of the rock sample t ＝2.09MPa。
Parts which are not described in the invention can be realized by adopting or referring to the prior art.
Claims (9)
1. A test method for rock tensile strength is characterized in that: the method comprises the following steps:
the method comprises the following steps: collecting mechanical parameters of a real rock sample, wherein the mechanical parameters comprise an elastic modulus E, a Poisson ratio mu, a volume modulus K and a shear modulus G;
step two: according to the collected mechanical parameters of the real rock sample, a test piece model with the length of l, the height of h, the thickness of t and a cylindrical through hole extending along the thickness direction and having the diameter of D is excavated in the center is established by using numerical software FLAC3D, the relation between the maximum tensile stress and the thickness of the test piece model under the action of the symmetrical compressive stress is calculated, and the thickness-diameter ratio m of the test piece model corresponding to the maximum tensile stress is found k The thickness-diameter ratio is the ratio of the thickness t of the test piece model to the diameter d of the cylindrical through hole;
the symmetrical compressive stress is vertical compressive stress applied to the upper top surface and the lower top surface of the test piece model;
step three: according to the mechanical parameters of the collected real rock sample, a numerical software FLAC3D is utilized to establish a test piece model with the length of l, the height of h, the thickness of t and a cylindrical through hole which extends along the thickness direction and has the diameter of D and is excavated at the center, and the thickness-diameter ratio of the test piece model is m k Calculating the maximum tensile stress of the test piece model under the action of different symmetrical compressive stresses, fitting a relational equation of the maximum tensile stress and the applied compressive stress, and determining a tensile strength correction equation;
step four: according to the thickness-diameter ratio m of the test piece determined by using numerical software to calculate k Taking a real rock sample, processing the rock sample into a cylindrical through hole with the length of l, the height of h, the thickness of t, the center of d and the diameter of d, wherein the cylindrical through hole extends along the thickness direction, and the thickness-diameter ratio of m k And carrying out a uniaxial compression test on the sample to be tested, and substituting the compressive stress borne by the sample in the tensile strength correction equation to obtain the tensile strength of the real rock sample.
2. The method for testing the tensile strength of the rock according to claim 1, wherein: the first step comprises the following steps: and (4) performing an indoor test, testing the elastic modulus and Poisson's ratio of the real rock sample, and calculating the bulk modulus and the shear modulus.
3. The method for testing the tensile strength of the rock according to claim 2, wherein: taking a real rock sample to be tested to perform an indoor rock deformation test, measuring the elastic modulus E and the Poisson ratio mu of the rock sample, substituting the elastic modulus E and the Poisson ratio mu into an elastic mechanics formula, and respectively calculating the bulk modulus K and the shear modulus G of the rock sample, wherein the bulk modulus K and the shear modulus G of the rock sample can be respectively expressed as: k = E/3 (1-2 μ), G = E/2 (1 + μ), where E is the rock sample elastic modulus and μ is the poisson's ratio of the rock sample.
4. The method for testing the tensile strength of the rock according to claim 1, wherein: the second step comprises the following steps: according to the mechanical parameters of the collected real rock sample, a test piece model with the length l =24cm and the height h =24cm is established by using numerical software FLAC3D, a cylindrical hole with the diameter D =3cm and the thickness same as that of the test piece model is excavated in the center of the test piece model, namely the cylindrical hole extends along the thickness direction of the test piece model and penetrates through the test piece model, and the thickness of the test piece model is respectively set as t 1 ＝0.3cm，t 2 ＝0.6cm，…，t 19 ＝5.7cm，t 20 =6.0cm, the thickness-diameter ratio m of the test piece model i Are respectively m 1 ＝0.1，m 2 ＝0.2，…，m 19 ＝1.9，m 20 =2.0, said thickness/diameter ratio m i Is a thickness t i The ratio of the stress to the diameter d of the central circular hole, the vertical compressive stress f is applied to the upper and lower top surfaces of the test piece model i Are respectively f 1 ＝2MPa、f 2 Performing elastic solution under the condition of =3 MPa; respectively extracting m with different thickness-diameter ratios i The maximum horizontal stress after the test piece model is calculated
Calculating the ratio of the maximum horizontal stress to the compressive stress applied by the test piece model
Drawing sigma xmax F-m plot of
Thickness-diameter ratio m of test piece corresponding to medium maximum value k 。
5. The method for testing the tensile strength of the rock according to claim 1, wherein: the third step comprises:
according to the acquired mechanical parameters of the real rock sample, a test piece model with the length l =24cm and the height h =24cm is established by using numerical software FLAC3D, a cylindrical hole with the diameter D =3cm and the thickness the same as that of the test piece model is excavated in the center of the test piece model, namely the cylindrical hole extends and penetrates along the thickness direction of the test piece model, and the thickness-diameter ratio of the test piece model is m obtained in the step two k (ii) a Applying vertical compressive stress f on the upper and lower surfaces of the test piece model j Are respectively set to f 1 ＝1.0MPa，f 2 ＝1.5MPa，…，f 9 ＝5.0MPa，f 10 =5.5MPa, elastic solution is respectively carried out, and different compressive stress loads f are extracted j Maximum horizontal stress calculated by test piece model under action
Drawing sigma xmax Fitting of σ to f-m plot xmax The equation for f is: sigma xmax = af + b, where a, b are constants obtained by fitting, equation σ xmax And (d) = af + b, namely the rock sample tensile strength correction equation.
6. The method for testing the tensile strength of the rock according to claim 1, wherein: the fourth step comprises: taking a real rock sample, processing the real rock sample into a sample to be measured with the length l =24cm and the height h =24cm, excavating a cylindrical hole with the diameter d =3cm and the thickness same as the thickness of the sample in the center of the sample, namely, the cylindrical hole extends along the thickness direction of the sample and penetrates through the sample, and taking the thickness-diameter ratio of the sample as m obtained in the step two k When the thickness of the sample is t = m k d; placing the rock sample on a testing machine to perform a uniaxial compression test, and observing the damage process of the rock sample; if the force applied on the testing machine is F when the rock sample cracks, the corresponding applied compressive stress on the sample is F = F/lt, and the tensile strength of the combined rock sample is F =The tensile strength of the rock sample can be expressed as sigma by the degree correction equation t = af + b, where σ t The tensile strength of the rock.
7. The method for testing the tensile strength of the rock according to claim 1, wherein: the ratio of the length l and the height h of the test piece model or the test piece to the diameter d of the central circular hole meets the condition that l/d is more than or equal to 8 and h/d is more than or equal to 8.
8. The method for testing tensile strength of rock according to claim 4, wherein: when the thickness-diameter ratio of the test piece corresponding to the maximum tensile stress is determined, vertical compressive stress f of multiple grades is adopted i Performing elasticity calculations, i.e. f i Are respectively f 1 ＝2MPa、f 2 ＝3MPa、…、f i ＝nMPa,n＞3。
9. The method for testing tensile strength of rock according to claim 6, wherein: and when the fracture initiation pressure of the real rock sample is determined, recording the damage process of the rock sample by adopting a high-power camera.
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Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN103900899A (en) * | 2014-03-27 | 2014-07-02 | 河南省水利科学研究院 | Test tamp and test method for measuring concrete tensile strength by adopting radial splitting method |
| CN107916934A (en) * | 2017-11-25 | 2018-04-17 | 彝良驰宏矿业有限公司 | Level pillar unstability critical thickness decision method under a kind of more stage casings while exploitation pattern |
| CN109632508A (en) * | 2019-01-08 | 2019-04-16 | 安徽理工大学 | A kind of test method of precise measurement Rock Under Uniaxial Compression tensile strength |
| CN110410151A (en) * | 2019-08-21 | 2019-11-05 | 兖州煤业股份有限公司 | A kind of coal mine rock burst method for early warning, system and its component |
Family Cites Families (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US8990028B2 (en) * | 2006-02-01 | 2015-03-24 | Nippon Steel & Sumitomo Metal Corporation | Fracture prediction method, device, a program arrangement and computer-accessible medium therefor |
| CN201413273Y (en) * | 2009-04-10 | 2010-02-24 | 山东大学 | Rock deformation and cracking three-dimensional dynamic testing device based on optical fiber strain sensing |
| CN103267678B (en) * | 2013-04-28 | 2015-08-05 | 北京大学 | A kind of method that hydrocarbon-bearing pool rock mass mechanics ground in-situ model recovers and device |
| CN104297028B (en) * | 2014-10-11 | 2016-09-14 | 四川大学 | Sillar test specimen and rocks in direct tension test method for direct tensile test |
| CN110044683B (en) * | 2019-04-08 | 2021-07-27 | 三峡大学 | Device and method for testing tensile and compressive creep of interbore rock bridge by using expanding agent |
-
2020
- 2020-04-13 CN CN202010284609.1A patent/CN111366461B/en active Active
Patent Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN103900899A (en) * | 2014-03-27 | 2014-07-02 | 河南省水利科学研究院 | Test tamp and test method for measuring concrete tensile strength by adopting radial splitting method |
| CN107916934A (en) * | 2017-11-25 | 2018-04-17 | 彝良驰宏矿业有限公司 | Level pillar unstability critical thickness decision method under a kind of more stage casings while exploitation pattern |
| CN109632508A (en) * | 2019-01-08 | 2019-04-16 | 安徽理工大学 | A kind of test method of precise measurement Rock Under Uniaxial Compression tensile strength |
| CN110410151A (en) * | 2019-08-21 | 2019-11-05 | 兖州煤业股份有限公司 | A kind of coal mine rock burst method for early warning, system and its component |
Non-Patent Citations (1)
| Title |
|---|
| 巴西劈裂试验对岩石抗拉强度影响因素研究;刘天宇等;《矿业工程研究》;20161220(第04期);第1-7页 * |
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