CN114577609A - Method for measuring in-situ rock I-type fracture toughness in field - Google Patents
Method for measuring in-situ rock I-type fracture toughness in field Download PDFInfo
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- CN114577609A CN114577609A CN202210271916.5A CN202210271916A CN114577609A CN 114577609 A CN114577609 A CN 114577609A CN 202210271916 A CN202210271916 A CN 202210271916A CN 114577609 A CN114577609 A CN 114577609A
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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
- G01N3/08—Investigating strength properties of solid materials by application of mechanical stress by applying steady tensile or compressive forces
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- G—PHYSICS
- G06—COMPUTING; CALCULATING OR COUNTING
- G06F—ELECTRIC DIGITAL DATA PROCESSING
- G06F30/00—Computer-aided design [CAD]
- G06F30/20—Design optimisation, verification or simulation
- G06F30/23—Design optimisation, verification or simulation using finite element methods [FEM] or finite difference methods [FDM]
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- G06F2111/00—Details relating to CAD techniques
- G06F2111/10—Numerical modelling
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- G—PHYSICS
- G06—COMPUTING; CALCULATING OR COUNTING
- G06F—ELECTRIC DIGITAL DATA PROCESSING
- G06F2119/00—Details relating to the type or aim of the analysis or the optimisation
- G06F2119/14—Force analysis or force optimisation, e.g. static or dynamic forces
Abstract
The invention provides a method for measuring in-situ rock I-type fracture toughness on site, which comprises the steps of carrying out in-situ drawing test on a rock on site to obtain the tensile strength of the rock, calculating an empirical formula for calculating the fracture toughness by using the tensile strength of the rock obtained by numerical simulation, and calculating the rock I-type fracture toughness. The method realizes the aim of testing the I-type fracture toughness of the rock on site, is suitable for testing the I-type fracture toughness in engineering, and considers the existence of secondary cracks during numerical simulation.
Description
Technical Field
The invention relates to the field of a method for measuring the fracture property of rock, in particular to a method for measuring the I-type fracture toughness of in-situ rock on site.
Background
In various geotechnical engineering, the problem of rock failure is mostly involved, and rock failure and fracture are initiated by crack propagation.
Fracture toughness is an important parameter of rock, and is a physical quantity that describes the ability of the rock to resist crack propagation, and is numerically equal to the stress intensity factor at the critical condition for crack propagation.
At present, domestic and foreign scientists provide a plurality of test methods for obtaining rock type I fracture toughness through tests, and a V-shaped kerf bending test piece (CB) method, a short rod test piece (SR) method, a Brazilian disc test piece (CCNBD) method and a semicircular disc (SCB) method of middle V-shaped kerf are recommended as standard methods for testing rock type I fracture toughness by the International society of rock mechanics and engineering (ISRM).
The methods are all methods for measuring the fracture toughness of the rock in a laboratory, the methods are difficult to apply in practical engineering, and the method for measuring the fracture toughness of the rock in an engineering field needs to be further developed.
Disclosure of Invention
The invention mainly aims to provide a method for measuring in-situ rock fracture toughness on site so as to solve the problems in the prior art.
The invention adopts the following technical scheme:
a method for measuring in-situ rock type I fracture toughness comprises the following steps:
step 1: selecting a proper drilling tool to drill a columnar core with the bottom connected with the original rock on the in-situ rock;
step 2: connecting the top end of the core with a stretching device by using an epoxy adhesive;
and step 3: measuring the tensile strength of the rock;
and 4, step 4: substituting the tensile strength of the rock into equation (1)
The I-type fracture toughness of the rock can be obtained.
In the formula (1), C is the diameter of a core;
d is the drilling depth;
r is tensile strength of the rock.
Further, the inner diameter of the drilling tool selected in step 1 should be more than ten times the average rock grain size, or more than 5cm and less than 15cm, so as to ensure the applicability of the method, and the selected test position should be representative.
Further, the formula in step 4 is an empirical formula obtained by numerical simulation, and the obtaining process is as follows:
(1) researching the three-dimensional stress field of the sample by using finite element software to determine a maximum tensile stress surface;
(2) establishing a 2D model to simulate an in-situ tensile test, setting 5 initial cracks with different lengths in a gradient manner, and calculating corresponding fracture strength factors by a J integration method respectively;
(3) fitting by utilizing the relation between the initial cracks with different lengths and the stress intensity factor to obtain the stress intensity factor when the initial crack is zero;
(4) according to formula (2)
The geometric factor Y is obtained.
In the formula (2), K is a breaking strength factor;
σ is the tensile stress at the maximum tensile stress plane.
(5) Establishing 2D models of different C and D, repeating the steps (2) to (4) to obtain a relation (3) of the geometric factor Y and the C and D
Y＝(0.8511×ln(C)+1.48945)×1.08938×D^(-0.61685) (3)
(6) Using the formula (4)
Finally, equation (1) is obtained.
Furthermore, due to the size limitation selected during modeling, the application range of the formula (1) in the step 4 is that C is more than or equal to 5cm and less than or equal to 15cm, D is more than or equal to 5cm and less than or equal to 15cm, and D is more than or equal to C.
Compared with the prior art, the method has the advantages that:
the method realizes the field measurement of the I-type fracture toughness, simplifies the calculation method of the I-type fracture toughness, is beneficial to engineering application, considers the existence of initial cracks during simulation, and is the premise of performing theoretical calculation of fracture mechanics.
Drawings
FIG. 1 is a flow chart of the present invention.
FIG. 2 is a schematic illustration of an in situ core.
Detailed Description
The technical solution of the present invention is further illustrated by the accompanying drawings and examples.
As shown in fig. 1, a method for measuring in-situ rock type i fracture toughness in situ comprises the following steps:
(1) as shown in fig. 2, a proper drilling tool is selected to drill a columnar core with the bottom connected with the original rock on the original rock, for example: the inner diameter of the drilling tool is 10cm, and the drilling depth is 10 cm;
(2) connecting the top end of the core with a stretching device by using an epoxy adhesive;
(3) testing to obtain the in-situ tensile strength R of the rock;
(4) substituting tensile strength of rock into formula
The I-type fracture toughness of the rock can be obtained.
The above description is only a preferred embodiment of the present invention, and is not intended to limit the technical scope of the present invention, so that any minor modifications, equivalent changes and modifications made to the above embodiment according to the technical spirit of the present invention are within the technical scope of the present invention.
Claims (4)
1. A method for measuring in-situ rock type I fracture toughness is characterized by comprising the following steps:
step 1: selecting a proper drilling tool to drill a columnar core with the bottom connected with the original rock on the in-situ rock;
step 2: connecting the top end of the core with a stretching device by using an epoxy adhesive;
and step 3: measuring the tensile strength of the rock;
and 4, step 4: substituting the tensile strength of the rock into equation (1)
The I-type fracture toughness K of the rock can be obtainedIC；
In the formula (1), C is the diameter of a core;
d is the drilling depth;
and R is the tensile strength of the rock.
2. The method for in-situ measurement of type i fracture toughness of rock in situ according to claim 1, wherein the drill tool selected in step 1 has an internal diameter greater than ten times the average grain size of the rock, or greater than 5cm and less than 15 cm.
3. The method for in-situ measurement of type i fracture toughness of rock in situ according to claim 1, wherein said formula (1) in step 4 is an empirical formula obtained by numerical simulation, and is obtained by the following method:
(1) researching the three-dimensional stress field of the sample by using finite element software to determine a maximum tensile stress surface;
(2) establishing a 2D model to simulate an in-situ tensile test, setting 5 initial cracks with different lengths in a gradient manner, and calculating corresponding fracture strength factors by a J integration method respectively;
(3) fitting by utilizing the relation between the initial cracks with different lengths and the stress intensity factor to obtain the stress intensity factor when the initial crack is zero;
(4) according to formula (2)
Obtaining a geometric factor Y;
in the formula (2), K is a breaking strength factor;
sigma is the tensile stress on the maximum tensile stress surface;
(5) establishing 2D models of different C and D, repeating the steps (2) - (4) to obtain a relation (3) of the geometric factor Y and the C and D
Y＝(0.8511×ln(c)+1.48945)×1.08938×D^(-0.61685) (3)
(6) Using formula (4)
Finally, equation (1) is obtained.
4. The method for measuring in-situ rock type I fracture toughness in the field according to claim 1, wherein the application range of formula (1) in the step 4 is 5 cm-C-15 cm, and 5 cm-D-15 cm.
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| CN202210271916.5A CN114577609B (en) | 2022-03-18 | 2022-03-18 | Method for in-situ measurement of I-type fracture toughness of in-situ rock |
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| CN114577609B CN114577609B (en) | 2023-06-16 |
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Citations (8)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP0250059A2 (en) * | 1986-06-19 | 1987-12-23 | Tohoku University | Method for determining fracture toughness of rock by core boring |
| US4821577A (en) * | 1987-06-22 | 1989-04-18 | Dowell Schlumberger Incorported | Modified ring test |
| CN101710042A (en) * | 2009-12-16 | 2010-05-19 | 上海理工大学 | Device and method for measuring I-type creep fracture toughness and fracture toughness of rock |
| CN104359776A (en) * | 2014-11-14 | 2015-02-18 | 四川大学 | Testing method of I-type crack dynamic fracture toughness under explosive load |
| CN105865924A (en) * | 2016-06-13 | 2016-08-17 | 南京大学 | Cohesive-soil strain-control-type I-type fracture toughness tester and testing method |
| CN105910899A (en) * | 2016-04-14 | 2016-08-31 | 华北水利水电大学 | Method for simultaneous determination of tensile strength and fracture toughness of rock material |
| CN106097125A (en) * | 2016-06-17 | 2016-11-09 | 延长油田股份有限公司 | A kind of Sandstone Gas Reservoir pressure break evaluation methodology |
| 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 |
-
2022
- 2022-03-18 CN CN202210271916.5A patent/CN114577609B/en active Active
Patent Citations (8)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP0250059A2 (en) * | 1986-06-19 | 1987-12-23 | Tohoku University | Method for determining fracture toughness of rock by core boring |
| US4821577A (en) * | 1987-06-22 | 1989-04-18 | Dowell Schlumberger Incorported | Modified ring test |
| CN101710042A (en) * | 2009-12-16 | 2010-05-19 | 上海理工大学 | Device and method for measuring I-type creep fracture toughness and fracture toughness of rock |
| CN104359776A (en) * | 2014-11-14 | 2015-02-18 | 四川大学 | Testing method of I-type crack dynamic fracture toughness under explosive load |
| CN105910899A (en) * | 2016-04-14 | 2016-08-31 | 华北水利水电大学 | Method for simultaneous determination of tensile strength and fracture toughness of rock material |
| CN105865924A (en) * | 2016-06-13 | 2016-08-17 | 南京大学 | Cohesive-soil strain-control-type I-type fracture toughness tester and testing method |
| CN106097125A (en) * | 2016-06-17 | 2016-11-09 | 延长油田股份有限公司 | A kind of Sandstone Gas Reservoir pressure break evaluation methodology |
| 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 |
Non-Patent Citations (3)
| Title |
|---|
| H.F. LI 等: "The relationship between fracture toughness and tensile property in high-strength steels", pages 1 - 10 * |
| VÍTOR OLIVEIRA SANTOS VIZINI等: "Mode I Fracture Toughness Determination of Rock and Concrete via Pull‑Of Test", pages 1305 * |
| 崔振东等: "岩石Ⅰ 型断裂韧度测试方法研究进展", pages 189 - 196 * |
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