Method, device, storage medium and equipment for evaluating brittleness of hard rock

Abstract

The present invention relates to a method, device, storage medium and equipment for evaluating the brittleness of hard rock. It is applicable to the field of underground engineering. The technical solution adopted by the present invention is: a method for evaluating the brittleness of hard rock, characterized by: obtaining the elastic modulus, Poisson's ratio, crack initiation strength, peak strength, uniaxial tensile strength, uniaxial compressive strength, crack extension volume strain and elastic volume strain of the rock to be evaluated; determining the brittleness evaluation index of the rock according to the hard rock brittleness evaluation model. A brittleness evaluation device for hard rock, characterized by comprising: a parameter acquisition module, used to obtain the elastic modulus, Poisson's ratio, crack initiation strength, peak strength, uniaxial tensile strength, uniaxial compressive strength, crack extension volume strain and elastic volume strain of the rock to be evaluated; a brittleness evaluation module, used to determine the brittleness evaluation index of the rock according to the hard rock brittleness evaluation model.

Description

Technical Field

[0001] The present invention relates to a hard rock brittleness evaluation method, device, storage medium and equipment, which are applicable to the field of underground engineering. Background Art

[0002] In underground engineering, brittle characteristics are an important indicator to characterize the drillability of rocks. In high-in-situ stress environments, brittle characteristics are also an important factor affecting high-in-situ stress damage such as rock bursts and spalling.

[0003] Brittleness is an inherent property of rock when it is damaged by force. Its characteristics are that the compressive strength is much greater than the tensile strength, and the ultimate strain value at the time of failure is extremely small. The existing rock brittleness index evaluation method mainly constructs the evaluation index from the following aspects: strength index, including tensile strength, compressive strength, residual strength, and crack initiation strength; shear strength parameters; deformation index, including elastic modulus and Poisson's ratio; strain index, including peak strain, residual strain, and strain energy; mineral composition; hardness; impact failure characteristics; penetration depth, load; rupture angle, etc.

[0004] The brittleness index of rock is widely used in the field of oil and gas production. Most companies have established their own evaluation methods for rock brittleness index for the evaluation of reservoir properties. The usual brittleness index generally has the following shortcomings: first, there are few parameters and can only reflect the influence of a certain aspect; second, there are many parameters, but the value selection method is complicated and the accuracy is low. Summary of the invention

[0005] The technical problem to be solved by the present invention is: in view of the above-mentioned existing problems, a method, device, storage medium and equipment for evaluating the brittleness of hard rock which can reflect key strength and deformation characteristics, has easy-to-obtain parameters and is easy to operate are provided.

[0006] The technical solution adopted by the present invention is: a method for evaluating the brittleness of hard rock, characterized in that:

[0007] Obtain the elastic modulus, Poisson's ratio, crack initiation strength, peak strength, uniaxial tensile strength, uniaxial compressive strength, crack extension volume strain and elastic volume strain of the rock to be evaluated;

[0008] Determine the rock brittleness evaluation index according to the hard rock brittleness evaluation model;

[0009] The hard rock brittleness evaluation model includes:

[0010] B=aB1+bB2+cB3+dB4+eB5

[0011] In the formula: B is the brittleness evaluation index, dimensionless; B1 is the sub-brittleness index based on the elastic modulus of rock, dimensionless; B2 is the sub-brittleness index based on the Poisson's ratio of rock, dimensionless; B3 is the sub-brittleness index based on the crack initiation strength and peak strength of rock, dimensionless; B4 is the sub-brittleness index based on the uniaxial tensile strength and compressive strength of rock, dimensionless; B5 is the sub-brittleness index based on the volume strain of rock crack extension and elastic volume strain, dimensionless; a, b, c, d, e are sub-coefficients.

[0012] The sub-item brittleness index based on rock elastic modulus includes:

[0013]

[0014] Where: E is the elastic modulus of the rock; E min is the minimum elastic modulus of rock material; E max is the maximum elastic modulus of rock material.

[0015] The sub-item brittleness index based on the rock Poisson's ratio includes:

[0016]

[0017] Where: ν is the Poisson's ratio of the rock; v min is the minimum Poisson's ratio of rock material; v max is the maximum Poisson's ratio of rock material.

[0018] The sub-item brittleness indexes based on rock crack initiation strength and peak strength include:

[0019]

[0020] Where: ci is the crack initiation strength of the rock; f is the peak strength of the rock.

[0021] The sub-item brittleness index based on the uniaxial tensile strength and compressive strength of rock includes:

[0022]

[0023] Where: t is the uniaxial tensile strength of the rock; σ c is the uniaxial compressive strength of the rock.

[0024] The sub-item brittleness index based on rock fracture extension volume strain and elastic volume strain includes:

[0025]

[0026] ε cg=max(ε cr )-ε cr

[0027] ε cr =ε v -ε ve

[0028]

[0029] Where: ε cg is the crack expansion volume strain; ε cr is the total volume strain of the crack; ε v is the volume strain; ε ve is the elastic volume strain; v is the Poisson's ratio of the rock; E is the elastic modulus of the rock; σ1, σ3 are the maximum principal stress and the minimum principal stress; ε cgf is the crack extension volume strain corresponding to the peak stress; ε vef is the elastic volume strain corresponding to the peak stress.

[0030] A brittleness evaluation device for hard rock, characterized by comprising:

[0031] Parameter acquisition module, used to obtain the elastic modulus, Poisson's ratio, crack initiation strength, peak strength, uniaxial tensile strength, uniaxial compressive strength, crack extension volume strain and elastic volume strain of the rock to be evaluated;

[0032] A brittleness evaluation module is used to determine the brittleness evaluation index of rock according to the hard rock brittleness evaluation model;

[0033] The hard rock brittleness evaluation model includes:

[0034] B=aB1+bB2+cB3+dB4+eB5

[0035] In the formula: B is the brittleness evaluation index, dimensionless; B1 is the sub-brittleness index based on the elastic modulus of rock, dimensionless; B2 is the sub-brittleness index based on the Poisson's ratio of rock, dimensionless; B3 is the sub-brittleness index based on the crack initiation strength and peak strength of rock, dimensionless; B4 is the sub-brittleness index based on the uniaxial tensile strength and compressive strength of rock, dimensionless; B5 is the sub-brittleness index based on the volume strain of rock crack extension and elastic volume strain, dimensionless; a, b, c, d, e are sub-coefficients.

[0036] A storage medium stores a computer program executable by a processor, wherein the computer program implements the steps of the hard rock brittleness evaluation method when executed.

[0037] A computer device comprises a memory and a processor, wherein the memory stores a computer program executable by the processor, wherein the computer program implements the steps of the hard rock brittleness evaluation method when executed.

[0038] The beneficial effect of the present invention is that the brittleness evaluation index obtained according to the hard rock brittleness evaluation model of the present invention fully reflects the following characteristics: the higher the elastic modulus, the stronger the brittleness characteristic; the lower the Poisson's ratio, the stronger the brittleness characteristic; the lower the crack initiation strength, the stronger the brittleness characteristic; the lower the tensile strength, the stronger the brittleness characteristic; the smaller the plastic strain occurring during destruction, the stronger the brittleness characteristic.

[0039] The present invention adopts the crack extension volume strain and volume strain to calculate the sub-item brittleness index, thus avoiding the one-sidedness caused by adopting a single direction strain.

[0040] The brittleness index calculation parameter proposed in the present invention is easy to obtain, and the types of tests performed are few. The brittleness index calculation results are consistent with the test phenomena and on-site failure phenomena, and can accurately reflect the brittle characteristics of hard rock, providing support for the drillability and high-stress failure risk assessment of rock. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 It is the full stress-strain curve diagram in the embodiment. DETAILED DESCRIPTION

[0042] This embodiment is a method for evaluating the brittleness of hard rock, which specifically includes the following steps:

[0043] S1. Obtain the elastic modulus E, Poisson's ratio v, and crack initiation strength σ of the target rock to be evaluated ci , peak intensity σ f , uniaxial tensile strength σ t , uniaxial compressive strengthσ c , the volume strain ε corresponding to the peak stress cgf and elastic volume strain ε vef .

[0044] Select representative samples to conduct rock tensile tests, uniaxial compression tests, or conventional triaxial compression tests (when it is necessary to evaluate the brittle characteristics of rocks under different confining pressures), obtain the full stress-strain curve of the test, and record the failure characteristics of the samples (such as Figure 1 shown).

[0045] According to the experimental stress-strain curve, the characteristic parameters of each representative rock sample are obtained, including the tensile strength σ t , uniaxial compressive strength σ c , elastic modulus E, Poisson's ratio v, peak strength σ under confining pressure in triaxial test f .

[0046] According to the experimental stress-strain curve, the deviator stress-volume strain curve and the deviator stress-crack total volume strain are obtained, and the crack initiation strength σ is determined according to the experimental curve ci , determine the maximum value of the total volume strain of the crack after the sample is compacted (max(ε cr ).

[0047] According to the experimental stress-strain curve, the volume strain ε of the sample at the peak stress is determined. v Combined with the specimen deformation parameters, calculate the elastic volume strain ε at peak stress ve , the total volume strain of the crack ε cr , and calculate the crack extension volume strain ε cg .

[0048] S2, according to the elastic modulus E, Poisson's ratio v, and crack initiation strength σ of the target rock ci , peak intensity σ f , uniaxial tensile strength σ t , uniaxial compressive strengthσ c , the crack extension volume strain and elastic volume strain corresponding to the peak stress are combined with the hard rock brittleness evaluation model to determine the rock brittleness evaluation index B (as shown in the following table).

[0049] The hard rock brittleness evaluation model in this embodiment includes:

[0050] B=aB1+bB2+cB3+dB4+eB5

[0051] Wherein: B is a brittleness evaluation index, dimensionless; B1 is a sub-item brittleness index based on the elastic modulus of rock, dimensionless; B2 is a sub-item brittleness index based on the Poisson's ratio of rock, dimensionless; B3 is a sub-item brittleness index based on the crack initiation strength and peak strength of rock, dimensionless; B4 is a sub-item brittleness index based on the uniaxial tensile strength and compressive strength of rock, dimensionless; B5 is a sub-item brittleness index based on the volume strain of rock crack extension and elastic volume strain, dimensionless; a, b, c, d, e are sub-item coefficients. In this embodiment, the sub-item coefficients are a=b=c=d=e=0.2.

[0052] In this example, the sub-item brittleness index based on rock elastic modulus includes:

[0053]

[0054] Where: E is the elastic modulus of the rock; E min is the minimum elastic modulus of the rock; E max is the maximum elastic modulus of the rock.

[0055] In this example, the sub-item brittleness indicators based on the Poisson's ratio of rock include:

[0056]

[0057] Where: v is the Poisson's ratio of the rock; v min is the minimum Poisson's ratio of the rock; v max is the maximum Poisson's ratio of the rock.

[0058] In this case, the sub-item brittleness indicators based on rock crack initiation strength and peak strength include:

[0059]

[0060] Where: ci is the crack initiation strength of the rock; f is the peak strength of the rock.

[0061] In this example, the sub-item brittleness indicators based on the uniaxial tensile strength and compressive strength of rock include:

[0062]

[0063] Where: t is the uniaxial tensile strength of the rock; σ c is the uniaxial compressive strength of the rock.

[0064] In this example, the sub-item brittleness indicators based on rock crack extension volume strain and elastic volume strain include:

[0065]

[0066] ε cg =max(ε cr )-ε cr

[0067] ε cr =ε v -ε ve

[0068]

[0069] Where: ε cg is the crack expansion volume strain; ε cr is the total volume strain of the crack; ε v is the volume strain; ε ve is the elastic volume strain; v is the Poisson's ratio of the rock; E is the elastic modulus of the rock; σ1, σ3 are the maximum principal stress and the minimum principal stress; ε cgf is the crack extension volume strain corresponding to the peak stress; ε vef is the elastic volume strain corresponding to the peak stress.

[0070] In this embodiment, the brittleness evaluation index B of rock determined based on the hard rock brittleness evaluation model is shown in the following table.

[0071] Table 1 Obtained basalt brittleness indexes

[0072]

[0073] This embodiment also provides a brittleness evaluation device for hard rock, including a parameter acquisition module and a brittleness evaluation module, wherein the parameter acquisition module is used to obtain the elastic modulus, Poisson's ratio, crack initiation strength, peak strength, uniaxial tensile strength, uniaxial compressive strength, crack extension volume strain and elastic volume strain of the rock to be evaluated; the brittleness evaluation module is used to determine the brittleness evaluation index of the rock according to the hard rock brittleness evaluation model.

[0074] This embodiment further provides a storage medium on which a computer program executable by a processor is stored. When the computer program is executed, the steps of the hard rock brittleness evaluation method of this embodiment are implemented.

[0075] This embodiment also provides a computer device, which has a memory and a processor. The memory stores a computer program that can be executed by the processor. When the computer program is executed, the steps of the hard rock brittleness evaluation method in this embodiment are implemented.

Claims

1. A method for evaluating the brittleness of hard rock, characterized in that: Obtain the elastic modulus, Poisson's ratio, crack initiation strength, peak strength, uniaxial tensile strength, uniaxial compressive strength, crack extension volume strain and elastic volume strain of the rock to be evaluated; Determine the rock brittleness evaluation index according to the hard rock brittleness evaluation model; The hard rock brittleness evaluation model includes: B=aB1+bB2+cB3+dB4+eB5 Wherein: B is the brittleness evaluation index, dimensionless; B1 is the sub-item brittleness index based on the elastic modulus of rock, dimensionless; B2 is the sub-item brittleness index based on the Poisson's ratio of rock, dimensionless; B3 is the sub-item brittleness index based on the crack initiation strength and peak strength of rock, dimensionless; B4 is the sub-item brittleness index based on the uniaxial tensile strength and compressive strength of rock, dimensionless; B5 is the sub-item brittleness index based on the volume strain of rock crack extension and elastic volume strain, dimensionless; a, b, c, d, e are sub-item coefficients; The sub-item brittleness index based on rock elastic modulus includes: Where: E is the elastic modulus of the rock; E min is the minimum elastic modulus of the rock; E max is the maximum elastic modulus of the rock; The sub-item brittleness index based on the rock Poisson's ratio includes: Where: v is the Poisson's ratio of the rock; v min is the minimum Poisson's ratio of the rock; v max is the maximum Poisson's ratio of the rock; The sub-item brittleness indexes based on rock crack initiation strength and peak strength include: Where: ci is the crack initiation strength of the rock; f is the peak strength of the rock; The sub-item brittleness index based on the uniaxial tensile strength and compressive strength of rock includes: Where: t is the uniaxial tensile strength of the rock; σ c is the uniaxial compressive strength of the rock; The sub-item brittleness index based on rock fracture extension volume strain and elastic volume strain includes: e cg =max(e cr )-e cr e cr =e v -e ve Where: ε cg is the crack expansion volume strain; ε cr is the total volume strain of the crack; ε v is the volume strain; ε ve is the elastic volume strain; v is the Poisson's ratio of the rock; E is the elastic modulus of the rock; σ1, σ3 are the maximum principal stress and the minimum principal stress; ε cgf is the crack extension volume strain corresponding to the peak stress; ε vef is the elastic volume strain corresponding to the peak stress.

2. A hard rock brittleness evaluation device, using the hard rock brittleness evaluation method according to claim 1, characterized in that: include: Parameter acquisition module, used to obtain the elastic modulus, Poisson's ratio, crack initiation strength, peak strength, uniaxial tensile strength, uniaxial compressive strength, crack extension volume strain and elastic volume strain of the rock to be evaluated; A brittleness evaluation module is used to determine the brittleness evaluation index of rock according to the hard rock brittleness evaluation model; The hard rock brittleness evaluation model includes: B=aB1+bB2+cB3+dB4+eB5 In the formula: B is the brittleness evaluation index, dimensionless; B1 is the sub-brittleness index based on the elastic modulus of rock, dimensionless; B2 is the sub-brittleness index based on the Poisson's ratio of rock, dimensionless; B3 is the sub-brittleness index based on the crack initiation strength and peak strength of rock, dimensionless; B4 is the sub-brittleness index based on the uniaxial tensile strength and compressive strength of rock, dimensionless; B5 is the sub-brittleness index based on the volume strain of rock crack extension and elastic volume strain, dimensionless; a, b, c, d, e are sub-coefficients.

3. A storage medium having stored thereon a computer program executable by a processor, characterized in that: The computer program, when executed, implements the steps of the hard rock brittleness evaluation method of claim 1.

4. A computer device comprising a memory and a processor, wherein the memory stores a computer program executable by the processor, wherein: The computer program, when executed, implements the steps of the hard rock brittleness evaluation method of claim 1.

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