CN116611264B - Rock damage evolution model considering initial damage recovery and construction method thereof - Google Patents
Rock damage evolution model considering initial damage recovery and construction method thereof Download PDFInfo
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- 239000011435 rock Substances 0.000 title claims abstract description 262
- 230000006378 damage Effects 0.000 title claims abstract description 234
- 238000011084 recovery Methods 0.000 title claims abstract description 43
- 238000010276 construction Methods 0.000 title claims abstract description 7
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- 230000006735 deficit Effects 0.000 claims description 4
- NAWXUBYGYWOOIX-SFHVURJKSA-N (2s)-2-[[4-[2-(2,4-diaminoquinazolin-6-yl)ethyl]benzoyl]amino]-4-methylidenepentanedioic acid Chemical compound C1=CC2=NC(N)=NC(N)=C2C=C1CCC1=CC=C(C(=O)N[C@@H](CC(=C)C(O)=O)C(O)=O)C=C1 NAWXUBYGYWOOIX-SFHVURJKSA-N 0.000 claims description 3
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- 230000005483 Hooke's law Effects 0.000 description 1
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Abstract
The invention discloses a rock damage evolution model considering initial damage recovery and a construction method thereof, and belongs to the technical field of rock deformation analysis. The method comprises the following steps: obtaining a rock stress-strain curve according to the rock uniaxial compression test data, thereby obtaining a crack strain-stress curve and a damage variable of the rock after a crack compaction stageAnd a damage variable-strain curve; establishing a damage evolution model of the rock in a crack compaction stage and a damage evolution model of the rock after the crack compaction stage; and building a coupling damage evolution model considering initial damage recovery of the rock according to the damage variable of the rock in the crack compaction stage and the damage variable of the rock after the crack compaction stage. The method considers the recovery process of the rock initial damage when building the coupling damage evolution model, and accords with the actual rock damage evolution process. Through verification, the model provided by the invention can better understand the rock damage and destruction process from a microscopic angle.
Description
Technical Field
The invention relates to the technical field of rock deformation analysis, in particular to a rock damage evolution model considering initial damage recovery and a construction method thereof.
Background
The rock has initial damage caused by the original defects of pores, cracks, joint weak planes, faults and the like which are more or less generated in the rock in the process of forming the rock in a long and complicated way and under the action of various external compound disturbance. Compared with an ideal rock block in an intact state, the initial defects or weak structural surfaces are distributed in the rock matrix in a staggered and random manner, so that macroscopic deformation mechanical parameters (elastic modulus, compressive strength and the like) of the rock block are changed, and the damage evolution process of the rock block is obviously influenced. From the perspective of the evolution process of the damage, a primary microcrack or a process of pore compression closure, namely initial damage recovery exists in the initial stage of rock loading deformation, and the damage degree is minimum or nearly no damage state is achieved in the elastic deformation stage; from the stress-strain curve, the damaged rock shows obvious nonlinear upward concave characteristics at the initial stage of the stress-strain curve under the uniaxial loading condition. Studies have shown that: the nonlinear characteristics of the compaction stage of the rock are weakened by the existence of lateral pressure, when the confining pressure is increased to a certain degree, the original defects or cracks in the rock are compressed and closed, the initial damage degree is gradually weakened and restored to be close to an ideal intact state, and the rock damage evolution process and the stress-strain relation show a huge difference compared with the condition containing the initial damage.
At present, a common rock damage evolution model is characterized by the degree of deterioration of the rock elastic modulus containing initial defects or damage (such as high-temperature heat treatment, joint inclination, karst fissures, water chemical corrosion, freeze thawing cycles and the like) compared with the initial elastic modulus of complete rock, and the method shows different damage degrees in the initial state of the rock, but the damage degree still remains at the initial damage level until the rock damage threshold, namely the yield strength. According to the strain evolution rule of the crack volume, the rock damage degree is gradually reduced before the elastic stage, namely the initial crack compression closure can be regarded as a dynamic process of recovering to a nondestructive or near-nondestructive state from the initial damage degree, and is not a nondestructive maintenance process. Therefore, existing rock damage evolution models are not effective for a fine-scale understanding of the rock damage destruction process.
Disclosure of Invention
In order to solve the problems in the prior art, the invention provides the following technical scheme.
The first aspect of the invention provides a method for constructing a rock damage evolution model considering initial damage recovery, comprising the following steps:
obtaining a rock stress-strain curve according to the rock uniaxial compression test data, and further obtaining a crack strain-stress curve;
according to the crack strain-stress curve, a damage evolution model of the rock in a crack compaction stage is established:
(1)；
in the formula (1), the components are as follows,the damage variable of the rock in the crack compaction stage is shown; />Is the initial damage coefficient; />Is stress;the equivalent elastic modulus of the rock in the crack compaction stage; />Strain for crack closure; />Peak strain, which is a stress-strain curve of rock;
calculating damage variable of rock after crack compaction stage according to rock stress-strain curveFurther, the damage variable ∈>-a strain curve;
according to the damage variable-the strain curve models the evolution of the damage of the rock after the crack compaction stage:
(2)；
in the formula (2), the amino acid sequence of the compound, and />All are fitting parameters, ++>Is strain;
according to the damage variable of rock in crack compaction stageAnd the damage variable of the rock after the crack compaction stage +.>Establishing a coupling damage evolution model considering rock initial damage recovery:
(3)；
in the formula (3), the amino acid sequence of the compound,to take into account coupled damage variables of the rock initial damage recovery.
Preferably, the obtaining a rock stress-strain curve from the rock uniaxial compression test data, and further obtaining a crack strain-stress curve comprises:
obtaining a rock stress-strain curve according to rock uniaxial compression test data;
and calculating the corresponding matrix strain and crack strain under a certain stress state according to the following formula by utilizing a rock stress-strain curve:
(4)；
(5)；
(6)；
wherein ,is the strain of the matrix; />Is crack strain; />The elastic modulus of the rock is obtained according to the slope of the elastic deformation phase of the rock stress-strain curve.
And respectively obtaining a matrix strain-stress curve and a crack strain-stress curve according to the stress and the matrix strain and the crack strain corresponding to the stress.
Preferably, the modeling the damage evolution of the rock in the crack compaction stage according to the crack strain-stress curve includes:
simulating crack strain of rock in compaction stage and elastic deformation stage：
(7)；
Damage variable characterizing rock in crack compaction stage：
(8)；
Combining formula (7) and formula (8):
(9)；
correction of formula (9) yields formula (10):
(10)。
preferably, the correcting of formula (9) includes:
(11)；
(12)；
the formula (11) is corrected by the formula (12):
(10)。
preferably, the damage variable of the rock after the crack compaction stage is calculated according to the stress-strain curve of the rockFurther, the damage variable ∈>-the strain curve comprises:
characterization of damage variables of rock after crack compaction stage：
(13)；
In the formula (13), the amino acid sequence of the compound,is a damage variable of the rock after the crack compaction stage; />The elastic modulus of the rock is determined according to the slope of the elastic deformation stage of the rock stress-strain curve; />The deformation modulus of the rock is the slope of a connecting line between any point on a rock stress-strain curve and the origin of coordinates;
calculating according to the formula (13) to obtain the damage variable corresponding to any point on the rock stress-strain curve after the crack compaction stage；
According to the damage variableAnd the corresponding strain-derived impairment variable +.>-a strain curve.
Preferably, the damage variable of the rock in the crack compaction stage is based onAnd the damage variable of the rock after the crack compaction stage +.>The building of the coupled damage evolution model considering rock initial damage recovery comprises the following steps:
according to the rock strain equivalent hypothesis theory, the method comprises the following steps:
(14)；
if only the damage of the rock in the crack compaction stage is considered, there are:
(15)；
considering that the rock is superimposed with the damage induced by the new crack initiation on the basis of the damage in the crack compaction stage, the following are:
(16)；
combining equation (14) and equation (16), a coupled damage evolution model is obtained that considers rock initial damage recovery:
(3)；
wherein ,is the elastic modulus of the damaged rock; />Is the elastic modulus of the lossless rock; />To take into account only the modulus of elasticity of the rock damaged in the crack compaction stage.
Preferably, the method comprises the steps of,obtained by fitting crack strain-stress curves.
Preferably, the method comprises the steps of,and obtaining the intersection point of the reverse extension line and the strain coordinate axis of the rock stress-strain curve elastic stage.
Preferably, the method comprises the steps of, and />All according to injury variable->-strain curve fitting.
The invention further provides a rock damage evolution model considering initial damage recovery, which is obtained by adopting the construction method of the rock damage evolution model considering initial damage recovery in the first aspect.
The beneficial effects of the invention are as follows: according to the rock damage evolution model considering initial damage recovery and the construction method thereof, firstly, a rock stress-strain curve is obtained according to rock uniaxial compression test data, and further, a crack strain-stress curve and a damage variable of the rock after a crack compaction stage are obtainedFurther, the damage variable ∈>-a strain curve; then, according to the crack strain-stress curve, building a damage evolution model of the rock in the crack compaction stage, and according to damage variables-the strain curve builds a model of the damage evolution of the rock after the crack compaction stage; finally according to the damage variable of the rock in the crack compaction stage +.>And the damage variable of the rock after the crack compaction stage +.>And establishing a coupling damage evolution model considering rock initial damage recovery. The method not only considers the damage variable of the rock after the crack compaction stage, but also considers the damage variable of the rock in the crack compaction stage when building the coupling damage evolution model,the recovery process of the rock initial damage is considered, and the actual rock damage evolution process is met, so that the rock damage process can be better understood from a fine view angle by adopting the model provided by the invention.
Drawings
FIG. 1 is a schematic diagram of a typical rock stress-strain curve;
FIG. 2 is a schematic diagram of the rock deformation, matrix deformation and crack deformation process according to the present invention;
FIG. 3 is a schematic diagram of the rock pre-peak deformation process according to the present invention;
FIG. 4 is a graph showing the calculation of elastic modulus of rock according to stress-strain curve according to the present inventionRock deformation modulus +.>Is a method schematic diagram of (a);
FIG. 5 is a graph showing the lesion variables according to the present invention-a strain curve schematic;
FIG. 6 is a graph showing uniaxial compressive stress-strain curves of three rock samples according to an embodiment of the present invention;
FIG. 7 is a schematic diagram showing the evolution process of uniaxial compression injury of a metamorphic gabion sample according to the embodiment of the invention;
FIG. 8 is a schematic diagram of a uniaxial compression damage evolution process of a red sandstone sample according to an embodiment of the present invention;
fig. 9 is a schematic diagram of a uniaxial compression injury evolution process of a layered siltstone sample according to an embodiment of the present invention.
Detailed Description
In order to better understand the above technical solutions, the following detailed description will be given with reference to the accompanying drawings and specific embodiments.
In the early stages of the uniaxial compression test of rock, the extent of rock damage is progressively reduced before the elastic phase, rather than a non-damage-preserving process, due to the initial crack compression closure of the rock. The invention constructs a rock damage evolution model on the basis of considering the rock initial damage recovery process.
The embodiment of the invention provides a method for constructing a rock damage evolution model considering initial damage recovery, which comprises the following steps:
obtaining a rock stress-strain curve according to the rock uniaxial compression test data, and further obtaining a crack strain-stress curve;
according to the crack strain-stress curve, a damage evolution model of the rock in a crack compaction stage is established:
(1)；
in the formula (1), the components are as follows,the damage variable of the rock in the crack compaction stage is shown; />Is the initial damage coefficient; />Is stress;the equivalent elastic modulus of the rock in the crack compaction stage; />Strain for crack closure; />Peak strain, which is a stress-strain curve of rock;
calculating damage variable of rock after crack compaction stage according to rock stress-strain curveFurther, the damage variable ∈>-a strain curve;
according to the damage variable-the strain curve models the evolution of the damage of the rock after the crack compaction stage:
(2)；
in the formula (2), the amino acid sequence of the compound, and />All are fitting parameters, ++>Is strain;
according to the damage variable of rock in crack compaction stageAnd the damage variable of the rock after the crack compaction stage +.>Establishing a coupling damage evolution model considering rock initial damage recovery:
(3)；
in the formula (3), the amino acid sequence of the compound,to take into account coupled damage variables of the rock initial damage recovery.
In the method, for the rock with the initial damage, the rock damage evolution model is established by considering the influence of the initial damage recovery process on the rock damage evolution, and the method has important reference value for understanding the rock damage process from a fine view point.
In an embodiment of the present invention, the obtaining a rock stress-strain curve according to the uniaxial compression test data of the rock, and further obtaining a crack strain-stress curve may include:
obtaining a rock stress-strain curve according to rock uniaxial compression test data;
and calculating the corresponding matrix strain and crack strain under a certain stress state according to the following formula by utilizing a rock stress-strain curve:
(4)；
(5)；
(6)；
wherein ,is the strain of the matrix; />Is crack strain; />The elastic modulus of the rock can be obtained according to the slope of the elastic deformation phase of the stress-strain curve of the rock.
And respectively obtaining a matrix strain-stress curve and a crack strain-stress curve according to the stress and the matrix strain and the crack strain corresponding to the stress.
Rock subjected to various disturbance effects in engineering practice generally contains initial damage, and it is the presence of these initial damage that causes the rock stress-strain curve to exhibit upwardly concave nonlinear variation characteristics in the early stages, as in fig. 1oaShown in section. Different samples from the same complete rock mass, at the same compression rate, the rock with high initial damage level enters the linear stage (as the curve in figure 1abcdA kind of electronic deviceabShown in section) The resulting axial deformation is greater, affecting the rock cracking compaction stage (as in figure 1oaShown in paragraph) and thus causes a change in the modulus of elasticity and compressive strength. Therefore, it is necessary to analyze macroscopic nonlinearity of the crack compaction stage at the initial stage of rock.
According to the theory of effective medium, under the condition of uniaxial loading, the strain of rockComprises basal body strain->And crack strain. The formula can be expressed as:
(4)；
the rock matrix may be approximated as a continuous solid material whose deformation process follows the generalized Hooke's law, and thus:
(5)；
combining formula (4) and formula (5), one can obtain:
(6)；
using the rock stress-strain curve, the deformation process of the rock matrix and crack with the increase of stress (i.e. matrix strain-stress curve and crack strain-stress curve), i.e. the deformation process before the rock peak, can be calculated according to formula (5) and formula (6), as shown in fig. 2. In the early stage of the uniaxial compression test, initial defects such as primary cracks or cracks in the rock are gradually compressed and compacted along with the increase of load stress, the initial defect or damage degree is also reduced along with the increase of load stress, and the crack deformation amount and the crack deformation curve in the stageOBSegments) are subject to the number, density and geometry characteristics of cracks occurring within the rockInfluence of factors such as symptoms; when the crack deformation curve tends to stabilize the deformation amount and does not grow any more, the rock deformation mainly consists of linear elastic deformation generated by a matrix, the primary defects are fully compacted at the stage, the current stress level is insufficient to promote the initiation of new microcracks, and the rock approximates to a complete rigid body and is in a state with relatively lowest damage degree or almost no damage; when the load stress continues to increase beyond the damage stress, the rock enters a plastic deformation stage, and new cracks start to initiate and develop, gradually merge and penetrate with the original compaction cracks to form macroscopic cracks, so that the rock is damaged.
In the invention, the crack strain of the rock in the compaction stage and the elastic deformation stage is simulated by using the following method：
(7)；
In (7)For crack closure strain, it can be determined from the intersection of the elastic phase reverse extension of the rock stress-strain curve in FIG. 2 and the ordinate axis (i.e. in FIG. 2AAxial strain values corresponding to points); />For the equivalent elastic modulus at the crack compaction stage, the crack strain-stress curve in fig. 2 can be fitted by using equation (7).
The method is characterized by comprising the steps of establishing a damage evolution model considering the rock initial damage recovery process, wherein the precondition is that a reasonable damage variable representation mode is selected, and common damage variable representation modes comprise an elastic variable method, an energy dissipation method, an acoustic emission characteristic parameter method, a crack strain method and the like. Considering that the rock deformation in the crack compaction stage is the result of the compression closure of the primary cracks, the crack strain method is selected to represent the damage variable of the rock in the crack compaction stage. That is, the crack strain of rock at any moment in compaction stage is definedStress-crack closure->The ratio of (2) is the damage variable of the rock in the crack compaction stage:
(8)；
in the formula ：is the damage variable of the rock in the crack compaction stage, and is 0.ltoreq. +.>Is less than or equal to 1, when->When=0, it indicates that the rock has no initial damage; when->At=1, rock full damage is indicated.
Combining formula (7) and formula (8) can be obtained:
(9)；
however, the damage variable calculated according to equation (9)Is monotonically increasing, does not conform to the changing characteristics of the initial lesion recovery, so equation (9) can be modified as:
(11)；
the damage variable calculated according to formula (11)Is monotonically decreasing from 1 to 0And the initial damage degree of the rock is not equal to 1. Thus, the initial damage coefficient is introducedD 0 Correction of equation (11) (to characterize the degree of rock initiation damage), which is typically characterized by the degree of weakening of the elastic modulus of the damaged rock relative to the elastic modulus of the undamaged rock, equation (17):
(17)；
in the formula Is the elastic modulus of the damaged rock; />Is the elastic modulus of the lossless rock.
However, the elastic modulus of a lossless rock is difficult to directly obtain. The invention proposes to adopt the crack closure strain before the rock peak on the basis of analyzing the deformation characteristic before the rock peak (as shown in figure 3, which is a deformation schematic diagram before the rock peak)And peak strain->The initial damage degree of the rock is represented by the ratio of the following expression:
(12)；
the formula (11) is corrected by the formula (12):
(10)。
the formula (10) is a damage evolution model of the rock in a crack compaction stage.
After the rock is subjected to the crack compaction process, the rock enters an elastic deformation stage, and the inside of the rock at the stageThe primary cracks are already compressed and closed, no new cracks are generated, the damage degree is the minimum state in the whole deformation process, when the load exceeds the damage stress, the rock enters the plastic deformation stage, the new cracks start to develop, and gradually merge and penetrate with the primary compaction cracks to form macroscopic cracks, so that the rock is damaged. Unlike the damage recovery process of the crack compaction stage, the damage process of the rock after the crack compaction stage is gradually damaged from a substantially intact state of the elastic deformation stage and evolves to a final damaged state of the rock. At this time, if the deformation process of the crack compaction stage is not considered, and if the rock is directly loaded into the elastic deformation stage as shown in fig. 4, the deformation modulus attenuation method can be used for representing the damage variable of the rock after the crack compaction stage：
(13)；
In the formula (13), the amino acid sequence of the compound,is a damage variable of the rock after the crack compaction stage; />The elastic modulus of the rock is determined according to the slope of the elastic deformation stage of the rock stress-strain curve; />The deformation modulus of the rock is the slope of a connecting line between any point on a rock stress-strain curve and the origin of coordinates;
calculating according to formula (13) to obtain damage variable corresponding to any point on the rock stress-strain curve after the crack compaction stageThe method comprises the steps of carrying out a first treatment on the surface of the According to the injury variable->And the corresponding strain-derived impairment variable +.>Strain curve, as shown in fig. 5. As can be seen from FIG. 5, the injury variable +.>The strain curve (i.e. the evolution process of the damage variable) shows a S-type transformation law and can be divided into 4 stages of initial no damage, start of damage, acceleration of damage and slowing down of damage. Because the S-shaped characteristic of the evolution process of the rock damage variable can be better described by using the Logistic function, the damage variable +_ of the rock after the crack compaction stage is established by using the Logistic function>The evolving theoretical equation, namely:
(2)；
in the formula (2), the amino acid sequence of the compound, and />Are fitting parameters, and the invention can be based on the damage variable +.>-strain curve fitting. The formula (2) is a damage evolution model of the rock after the crack compaction stage.
It is considered that damage to the rock during the crack compaction stage is induced by the compaction closure of the primary crack, whereas damage after the crack compaction stage is induced by the propagation of the new crack. Therefore, it is necessary to build a coupled damage evolution model that considers both the primary crack closure and the new crack growth. According to the invention, firstly, according to the rock strain equivalent hypothesis theory, the method comprises the following steps:
(14)；
if only the damage of the rock in the crack compaction stage is considered, there are:
(15)；
considering that the rock is superimposed with the damage induced by the new crack initiation on the basis of the damage in the crack compaction stage, the following are:
(16)；
combining equation (14) and equation (16), a coupled damage evolution model is obtained that considers rock initial damage recovery:
(3)；
wherein ,is the elastic modulus of the damaged rock; />Is the elastic modulus of the lossless rock; />To take into account only the modulus of elasticity of the rock damaged in the crack compaction stage.
The formula (3) is the rock damage evolution model considering initial damage recovery.
For the rock damage evolution model considering initial damage recovery provided by the invention, the effect of the rock damage evolution model is verified by adopting the following specific embodiments.
The three different rock samples of metamorphic gabbro, red sandstone and lamellar siltstone, which were taken from the site, were processed into standard cylindrical samples having a height of 100mm and a diameter of 50mm, and then subjected to an indoor uniaxial compression test to obtain uniaxial compression stress-strain curves of the three samples, as shown in fig. 6.
According to the stress-strain curve of the uniaxial compression test of each sample, each parameter value of the rock damage evolution model considering initial damage recovery can be obtained according to the steps shown in the technical scheme, as shown in table 1.
Substituting each parameter value in table 1 into formula (3) to obtain rock damage evolution models of the three rocks, wherein the rock damage evolution models consider initial damage recovery:
the damage evolution process under the uniaxial compression condition of three samples (as shown in fig. 7-9) can be obtained according to the rock damage evolution model considering the initial damage recovery, and the three stages are roughly divided: the damage weakening, damage holding and damage development are respectively in one-to-one correspondence with the crack compaction, elastic deformation and plastic deformation processes of the rock stress-strain curve (shown in fig. 7), or respectively in one-to-one correspondence with the crack compaction, elastic deformation, plastic deformation and strain softening processes of the rock stress-strain curve (shown in fig. 8-9). Because the compression strength and the elastic modulus of the metamorphic gabion are higher, the peak stress is small when the metamorphic gabion is damaged, and the metamorphic gabion belongs to strong brittle rocks, the post-peak stress-strain curve cannot be completely measured, and therefore the post-peak strain softening process does not occur. The analysis accords with the evolution process from compression closure to initiation development of cracks under the rock loading condition, so that the rock damage evolution model which is established by the invention and considers the initial damage recovery is reasonable.
While preferred embodiments of the present invention have been described, additional variations and modifications in those embodiments may occur to those skilled in the art once they learn of the basic inventive concepts. It is therefore intended that the following claims be interpreted as including the preferred embodiments and all such alterations and modifications as fall within the scope of the invention. It will be apparent to those skilled in the art that various modifications and variations can be made to the present invention without departing from the spirit or scope of the invention. Thus, it is intended that the present invention also include such modifications and alterations insofar as they come within the scope of the appended claims or the equivalents thereof.
Claims (6)
1. The method for constructing the rock damage evolution model considering initial damage recovery is characterized by comprising the following steps of:
obtaining a rock stress-strain curve according to the rock uniaxial compression test data, and further obtaining a crack strain-stress curve;
according to the crack strain-stress curve, a damage evolution model of the rock in a crack compaction stage is established:
(1)；
in the formula (1), the components are as follows,the damage variable of the rock in the crack compaction stage is shown; />Is the initial damage coefficient; />Is stress; />The equivalent elastic modulus of the rock in the crack compaction stage; />Strain for crack closure; />Peak strain, which is a stress-strain curve of rock;
calculating damage variable of rock after crack compaction stage according to rock stress-strain curveFurther, the damage variable ∈>-a strain curve;
according to the damage variable-the strain curve builds a model of the evolution of the damage of the rock after the crack compaction stage:
(2)；
in the formula (2), the amino acid sequence of the compound, and />All are fitting parameters, ++>Is strain;
according to the damage variable of rock in crack compaction stageAnd the damage variable of the rock after the crack compaction stage +.>The initial damage of the rock is considered in the establishmentRecovered coupled impairment evolution model:
(3)；
in the formula (3), the amino acid sequence of the compound,coupling damage variables for consideration of rock initial damage recovery;
the building of the damage evolution model of the rock in the crack compaction stage according to the crack strain-stress curve comprises the following steps:
simulating crack strain of rock in compaction stage and elastic deformation stage：
(7)；
Damage variable characterizing rock in crack compaction stage：
(8)；
Combining formula (7) and formula (8):
(9)；
correction of formula (9) yields formula (10):
(10)；
the correcting of the formula (9) includes:
(11)；
(12)；
the formula (11) is corrected by the formula (12):
(10)；
the damage variable of the rock after the crack compaction stage is calculated according to the stress-strain curve of the rockFurther, the damage variable ∈>-the strain curve comprises:
characterization of damage variables of rock after crack compaction stage：
(13)；
In the formula (13), the amino acid sequence of the compound,is a damage variable of the rock after the crack compaction stage; />The elastic modulus of the rock is determined according to the slope of the elastic deformation stage of the rock stress-strain curve; />The deformation modulus of the rock is the slope of a connecting line between any point on a rock stress-strain curve and the origin of coordinates;
calculating according to formula (13) to obtain damage variable corresponding to any point on the rock stress-strain curve after the crack compaction stage；
According to the damage variableAnd the corresponding strain-derived impairment variable +.>-a strain curve;
the damage variable of the rock in the crack compaction stageAnd the damage variable of the rock after the crack compaction stage +.>The building of the coupled damage evolution model considering rock initial damage recovery comprises the following steps:
according to the rock strain equivalent hypothesis theory, the method comprises the following steps:
(14)；
if only the damage of the rock in the crack compaction stage is considered, there are:
(15)；
considering that the rock is superimposed with the damage induced by the new crack initiation on the basis of the damage in the crack compaction stage, the following are:
(16)；
combining equation (14) and equation (16), a coupled damage evolution model is obtained that considers rock initial damage recovery:
(3)；
wherein ,is the elastic modulus of the damaged rock; />Is the elastic modulus of the lossless rock; />To take into account only the modulus of elasticity of the rock damaged in the crack compaction stage.
2. The method of constructing a rock damage evolution model with initial damage recovery in mind of claim 1, wherein said deriving a rock stress-strain curve from rock uniaxial compression test data, and further deriving a crack strain-stress curve, comprises:
obtaining a rock stress-strain curve according to rock uniaxial compression test data;
and calculating the corresponding matrix strain and crack strain under a certain stress state according to the following formula by utilizing a rock stress-strain curve:
(4)；
(5)；
(6)；
wherein ,is the strain of the matrix; />Is crack strain; />The elastic modulus of the rock is obtained according to the slope of the elastic deformation stage of the stress-strain curve of the rock;
and respectively obtaining a matrix strain-stress curve and a crack strain-stress curve according to the stress and the matrix strain and the crack strain corresponding to the stress.
3. The method for constructing a model of evolution of rock damage taking into account initial damage recovery as claimed in claim 1, wherein,obtained by fitting crack strain-stress curves.
4. The method for constructing a model of evolution of rock damage taking into account initial damage recovery as claimed in claim 1, wherein,and obtaining the intersection point of the reverse extension line and the strain coordinate axis of the rock stress-strain curve elastic stage.
5. The method for constructing a model of evolution of rock damage taking into account initial damage recovery as claimed in claim 1, wherein, and />All according to injury variable->-strain curve fitting.
6. A rock damage evolution model taking into account initial damage recovery, characterized in that the rock damage evolution model taking into account initial damage recovery is obtained by adopting the construction method of the rock damage evolution model taking into account initial damage recovery as claimed in any one of claims 1 to 5.
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