CN105910906A - Numerical description method of marble post-peak brittleness-malleability-plasticity conversation mechanical property - Google Patents

Abstract

The invention provides a numerical description method of the marble post-peak brittleness-malleability-plasticity conversation mechanical characteristics. The method comprises the steps that the change characteristics of marble intensity parameters along with the plastic strain at the different confining pressure levels are described on the basis of a Hoek-Brown constitutive model; an indoor loading test is conducted to obtain marble mechanical property parameters and the post-peak mechanical characteristics; numerical analog simulation is conducted through a finite difference method; the boundary conditions of the model are set, and a confining pressure load is applied to a unit body; after the unit body is initially balanced, axial uniform-velocity loading is conducted, and the calculation time step is set for calculation and solution; the size of the confining pressure load is changed, numerical simulation calculation is repeatedly conducted, and then a numerical description result of the marble post-peak brittleness-malleability-plasticity conversation mechanical characteristics at the different confining pressure levels is obtained. According to the method, the numerical description precision of the deep-buried marble post-peak brittleness-malleability-plasticity conversation mechanical characteristics is improved, and the method can be widely applied to numerical description and confining pressure stability analysis on the mechanical characteristics of deep-buried underground engineering such as hydropower and traffic.

Description

Behind a kind of griotte peak crisp prolong mould conversion mechanical characteristic numerical value method is described

Technical field

After the present invention relates to a kind of griotte peak crisp prolong mould conversion mechanical characteristic numerical value method is described, with existing Description method is compared, and describes precision higher.It is applicable to the buried griotte of the underground engineering such as water conservancy and hydropower, traffic open When digging, mechanical characteristic behind country rock peak is carried out numerical value description.

Background technology

21 century mankind's underground space development activity gets more and more, and gradually moves towards Earth, buried depth is big, Crustal stress height has become one of typical geologic feature of underground rock engineering, and steady to the safety of deep cavern country rock Determine important.Substantial amounts of engineering practice, Theoretical Calculation and numerical value analysis and research are it has been shown that excavate off-load The primary stress of rock mass can be broken so that surrouding rock stress is readjusted, and cause country rock stress raisers, when When concentrated stress exceedes the utmost carrying ability of country rock, country rock will enter mechanical state behind peak, and physical and mechanical parameter is bad Changing, bearing capacity of the wall rock and stability are substantially reduced.Therefore, lithology and load behind peak mechanical characteristic to country rock Bearing capacity and stability have a major impact.When mechanical characteristic is more complicated behind crustal stress, rock peak, uses and pass It is more difficult that system theoretical method analyzes deep rock mass excavation surrounding rock stability, and efficiency is relatively low, method for numerical simulation As a kind of the most efficient but also practical technology, it is widely used for analyzing the damage of country rock after deep rock mass excavates Feature, and use the peak that it is critical only that accurate description rock of numerical method accurate simulation rock convergence measure destructive characteristics Rear mechanical characteristic.

China is the country that hydraulic power potentials is the abundantest in the world, and a large amount of high-quality HYDROELECTRIC ENERGY are stored in Southwestern China ground District, is limited by southwest high mountain gorge orographic condition, and most of Hydraulic and Hydro-Power Engineerings are by water such as power plant buildings Work building is arranged in underground, all refers to high intensity, large-scale buried rock excavation.Additionally, Southwestern China Is produced from area abundant griotte, the griotte not single-mode of the curves of stress-strain relationship in loading procedure, But show obvious confined pressure dependency, during the lowest confined pressure, behind griotte peak, mechanical characteristic is close with granite, Show Brittleness；When confined pressure raises, behind griotte peak, mechanical characteristic shows ductile characteristic；Work as confined pressure When reaching certain level, show again obvious plastic behavior.Therefore, accurate description griotte increases with country rock And behind the peak presented crisp prolong mould conversion mechanical characteristic be use numerical simulation analysis deep rock mass excavation country rock steady Premise qualitatively.

In rock-soil mechanics, most widely used theory is Mohr-Coulomb strength theory at present, by σ₁And σ₃Table The Mohr-Coulomb criterion of strength shown relation on principal stress plane is:

In formula, c is cohesive strength；For internal friction angle；σ₁、σ₃It is respectively maximum, minimum principal stress.This reason Opinion think, when material reaches capacity state, the shear stress on certain shear surface reach one depend on direct stress with The maximum of material character.By rock being compressed test, it is thus achieved that maximum, minimum principal stress value, sitting A series of limit stress circle representing these limit states, and the envelope of these limit stresses circle is made in mark plane Line, this envelope is exactly the criterion of strength of rock.Therefore, Mohr's stress circle is the most tangent with intensity curve just becomes Differentiating the criterion whether rock destroys, these expression formulas are different because rock strength curve shape is different, if Mohr's envelope is that straight line is then referred to as Mohr-Coulomb criterion, and its expression formula is:

τ≥μσ+c(2)

In formula, σ, τ are direct stress and the shear stress of this plane；It is respectively internal friction with μ Angle and coefficient of internal friction；C is cohesive strength intensity.

Mohr-Coulomb strength theory is applicable to the isotropic rock mass of homogenizing, can describe fragile material and mould The destructive characteristics of property material, than more fully having reacted the strength characteristics of rock, but Mohr-Coulomb criterion Fail to consider the feature that strain of rock mass softens, it is impossible to dynamically mechanical behavior during reflection rock mass damage, simultaneously Mohr-Coulomb criterion mainly describes and linearly destroys rock mass, but griotte stress in loading procedure- Strain curve not single-mode, but show obvious confined pressure dependency, therefore Mohr-Coulomb Strength theory has some limitations during mechanical characteristic behind the peak describing griotte.

Summary of the invention

Describe the defect of griotte mechanical characteristic for Mohr-Coulomb model, the present invention proposes one and retouches After stating the higher griotte peak based on Hoek-Brown constitutive model of precision, crisp prolonging moulds the number changing mechanical characteristic Value description method.

The principle of the invention is: based on Hoek-Brown constitutive model, first passes through and does indoor load test, Obtain mechanical characteristics and Mechanics Parameters of Rock Mass behind griotte peak；The mechanics parameter that recycling is obtained uses finite difference Point-score carries out numerical simulation；Finally utilize the credibility of actual measurement acoustic velocity checking computations numerical simulation.

In order to realize above-mentioned technical characteristic, the object of the present invention is achieved like this: crisp behind a kind of griotte peak Prolong mould conversion mechanical characteristic numerical value method is described, including step:

Step 1, use Hoek-Brown constitutive model carry out to griotte crisp prolong mould conversion mechanical characteristic retouch State, it is allowed to m after rock mass surrender_b、s、a(m_b, s, a be to rock-mass quality scoring and sillar material parameters relevant Parameter) equal strength parameter is along with plastic strainAccumulation and change, in order to describe the strengthening of material after surrender And softening behavior.Softening and hardening description is introducing one and minimum principal stress σ₃Relevant zoom factor μ, For describing m under different confined pressure level_b, s, a equal strength parameter is along with plastic strainVariation characteristic；

Step 2, takes griotte rock sample test piece and carries out confined pressure loading experiment in indoor, it is thus achieved that power behind the peak of griotte Learn characteristic and the mechanics parameters of griotte；

Step 3, uses finite difference calculus to carry out numbered analog simulation, creates geometric model, definition material model For Hoek-Brown model, according to the mechanics parameters Definition Model material parameter above obtained；Arrange The boundary condition of model, then applies confined pressure to unit model, the most at the uniform velocity loads, finally solve and tied Really, then the load-deformation curve of griotte under this confined pressure is obtained；

Step 4, changes the size of applied confined pressure load, repeats above-mentioned numbered analog simulation process, Obtain one group of griotte load-deformation curve under different confined pressures.

Step 5, utilizes the credibility of actual measurement velocity of wave checking computations numerical simulation result, and the velocity of wave band that will survey is sentenced Fixed rock convergence measure scope compares with by the rock convergence measure scope obtained by the method for numerical simulation.

Described step 1 farther includes sub-step:

Step 1-1: based on Hoek-Brown criterion of strength, proposes a kind of relevant to Rock Damage degree non- Fixing flow rule, the pare-debris flow body of its constitutive model is:

${\mathrm{\σ}}_1={\mathrm{\σ}}_3+{\mathrm{\σ}}_{ci}{(m_b\frac{{\mathrm{\σ}}_3}{{\mathrm{\σ}}_1}+s)}^a---\left(3\right)$

Model supposes maximum plastic strain incrementWith minimum plastic strain incrementMeet following relation:

${\mathrm{\Δ\ϵ}}_1^p={\mathrm{\γ\Δ\ϵ}}_3^p---\left(4\right)$

In formula: σ₁、σ₃It is respectively minimum and maximum principal stress during rock mass surrender；σ_ciList for sillar test specimen Axle comprcssive strength；m_b, s and a be and rock-mass quality scoring GSI and sillar material parameters m_iRelevant parameter；γ For the factor relevant to stress level.

Step 1-2: introduce 4 kinds of flow rules according to stress level Hoek-Brown model:

(1) associated flow, describes the yield characteristics under the conditions of low confined pressure, and now the volumetric strain of rock mass increases Long the fastest, and associated flow criterion can guarantee that bulk strain is farthest increased theoretically.Association The flow rule of flowing is:

${\mathrm{\Δ\ϵ}}_i^p=-\mathrm{\γ}\frac{\∂F}{\∂{\mathrm{\σ}}_i}---\left(5\right)$

By formula (1), (3) are brought formula (2) into and can are in the hope of the factor gamma of associated flow:

${\mathrm{\γ}}_{af}=-\frac{1}{1+{\mathrm{am}}_b{(m_b\frac{{\mathrm{\σ}}_3}{{\mathrm{\σ}}_1}+s)}^{a-1}}---\left(6\right)$

(2) equal-volume flowing criterion, when confined pressure increases to confined pressure higher limitFollow-up after sillar surrender In loading procedure, volume keeps constant, for describing the yield characteristics under high confining pressure.Flow rule expression formula is:

γ_cv=-1 (7)

(3) Radial Flow rule, describes the extensional under sillar tension and destroys.Flow rule is:

${\mathrm{\γ}}_{rf}=\frac{{\mathrm{\σ}}_1}{{\mathrm{\σ}}_3}---\left(8\right)$

(4) combination flowing, when confined pressure isFlow rule after sillar surrender should be between association stream Between dynamic and equal-volume flows, combination flowing criterion is therefore used to be been described by.Combination flow rule is:

$\mathrm{\γ}=\frac{1}{\frac{1}{{\mathrm{\γ}}_{af}}+(\frac{1}{{\mathrm{\γ}}_{cv}}-\frac{1}{{\mathrm{\γ}}_{af}})\frac{{\mathrm{\σ}}_3}{{\mathrm{\σ}}_3^{cv}}}---\left(9\right)$

Step 1-3: softening and introducing one and minimum principal stress σ in hardening description₃Relevant zoom factor μ, is used for describing m under different confined pressure level_b, s, a equal strength parameter is along with plastic strainVariation characteristic.

Described step 3 farther includes following sub-step:

Step 3-1: carry out numbered analog simulation based on finite difference calculus, creates initial three-dimensional element body geometry mould Type；

Step 3-2: the material model in definition unit body region is Hoek-Brown model, according to indoor examination Test the material parameter in obtained mechanics parameters definition Hoek-Brown model；

Step 3-3: monitoring variable or parameter is set, the most correct for discriminatory analysis, model whether with reality Be consistent, calculate whether restrain, the most consistent with existing conclusion etc.；

Step 3-4: arrange boundary condition and original upload condition, applies a certain confined pressure load and carries out initial balance Solve, set up the poised state of model initialization；

Step 3-5: the most at the uniform velocity load calculating and solve, Time step is set, when the computing time step reaching setting Time calculate terminate.During solving calculating, if model of element enters the residual strength stage, then to model The material parameter calculated is modified and after reduction, proceeds subsequent calculations；

Step 3-6: result output and analysis, draws the griotte stress-strain song that curve obtains under this confined pressure Line.

The method have the advantages that:

(1) in a model, it is allowed to after sillar surrender, rock strength parameter changes along with the accumulation of plastic strain, Therefore material reinforcement after surrender and softening behavior can be described.

(2) simple to operation, the scope of application is wider, and carry out actual compared to scene detects test, saves The resources such as substantial amounts of material resources and financial resources, and method highly effective.

(3) after improve buried griotte peak crisp prolong mould conversion mechanical characteristic numerical value precision is described, can be extensive Numerical value for the deep-buried underground engineering mechanical characteristic such as water power, traffic describes and Stability Analysis of The Surrounding Rock.

Detailed description of the invention

In existing rock-soil mechanics, most widely used theory is Mohr-Coulomb strength theory, but Mohr-Coulomb criterion fails to consider the feature that strain of rock mass softens, mechanics performance behind the peak of griotte simultaneously Gone out obvious confined pressure dependency rather than single failure mode, for avoiding the problems referred to above, the present invention based on Hoek-Brown constitutive model, uses finite difference calculus to carry out numbered analog simulation to crisp after describing griotte peak Prolong the change of mechanical property moulding conversion.With existing description method phase based on Mohr-Coulomb strength theory Ratio, description of the invention result is the most accurately and reliably.

The specific implementation process of the present invention will be described in detail below.

First, based on Hoek-Brown constitutive model, introduce a kind of relevant to griotte damage strength non-solid Determining flow rule, its pare-debris flow body is:

${\mathrm{\σ}}_1={\mathrm{\σ}}_3+{\mathrm{\σ}}_{ci}{(m_b\frac{{\mathrm{\σ}}_3}{{\mathrm{\σ}}_1}+s)}^a---\left(3\right)$

Model supposes maximum plastic strain incrementWith minimum plastic strain incrementMeet following relation:

${\mathrm{\Δ\ϵ}}_1^p={\mathrm{\γ\Δ\ϵ}}_3^p---\left(4\right)$

In formula: σ₁、σ₃It is respectively minimum and maximum principal stress during rock mass surrender；σ_ciList for sillar test specimen Axle comprcssive strength；m_b, s and a be and rock-mass quality scoring GSI and sillar material parameters m_iRelevant parameter；γ For the factor relevant to stress level.

Meanwhile, four kinds of flow rules are introduced depending on stress level during surrender: associated flow rule, equal-volume flow Rule, Radial Flow rule, combination flow rule, and the zoom factor μ relevant to minimum principal stress with, For describing under different confined pressure level griotte intensive parameter with the variation characteristic of plastic strain.

Then, take griotte rock sample test piece and carry out load test in indoor, it is thus achieved that mechanical characteristics behind the peak of griotte And mechanics parameters.

Then, finite difference calculus is used to carry out numbered analog simulation, to crisp behind the griotte peak under different confined pressures Prolong and mould conversion mechanical characteristic and carry out numerical value description, use following steps to carry out numerical simulation:

(1) creating initial geometric model, create in the present invention is three-dimensional element volume geometric model；

(2) material model in definition unit body region is Hoek-Brown constitutive model, according to above indoor Material parameter in the mechanics parameters Definition Model that test is obtained；

(3) monitoring variable or monitoring parameter is set, the most correct for discriminatory analysis, model whether with reality Be consistent, calculate whether restrain, the most consistent with existing conclusion etc.；

(4) arranging boundary condition and original upload condition, applying confined pressure load carries out initial balance and solves, builds The initialized poised state of formwork erection type；

(5) the most at the uniform velocity load calculating to solve, Time step is set, the meter when reaching the computing time step arranged Terminate.During solving calculating, if unit model enters the residual strength stage, then to model meter The material parameter calculated is modified and after reduction, proceeds subsequent calculations.

(6) result output, draws the griotte load-deformation curve obtaining under this confined pressure.Change and applied to enclose The size of pressure load, repeats aforesaid numbered analog simulation process, obtains griotte under different confined pressures Load-deformation curve change procedure.

Finally use the credibility of actual measurement velocity of wave checking computations numerical simulation result, the velocity of wave band of actual measurement will be utilized to be sentenced Fixed rock convergence measure scope compares with by the rock convergence measure scope obtained by numerical simulation, both country rocks Damage range the most then illustrates that the credibility of numerical simulation result is preferable.

The technique effect of the present invention is further illustrated below in conjunction with accompanying drawing and example.

Rock stratum residing for certain deep-lying tunnel is mainly griotte, causes greatly crustal stress level high due to buried depth, Big principal stress is up to 72MPa, and direction is parallel with canal axes；Minimum principal stress is up to 32MPa, and direction is erected Straight downward.

First, take griotte rock sample and carry out three axle confining pressure tests in indoor, process of the test constantly changes and encloses The size of pressure load, obtains mechanical characteristic behind the peak of griotte, three axle confining pressure test schematic diagram such as Fig. 2 Shown in.Meanwhile, by uniaxial compression test and triaxial compression test, and by griotte rock mass characteristic and The analysis of rock integrity etc., obtains the mechanics parameter of griotte, for followed by during numerical simulation to model In material parameter be defined.

Then, finite difference calculus is used to carry out numbered analog simulation, to crisp behind the griotte peak under different confined pressures Prolong and mould conversion mechanical characteristic and carry out numerical value description, use following process to carry out numerical simulation:

(1) creating three-dimensional element volume geometric model, this numerical simulation is only with a standard size (1m × 1m × 1m) unit, eliminates the strain localization's phenomenon in numerical procedure, obtained by calculating Stress and strain is decided by feature and the rock mass materials parameter of constitutive model；

(2) material model in definition unit body region is Hoek-Brown constitutive model, according to above indoor Material parameter in the mechanics parameters Definition Model that test is obtained；

(3) monitoring variable or monitoring parameter, the position that sample record coordinate (0,0,1) place node is axial are set Move, and the size of maximal unbalanced force in monitoring model, utilize the variable of monitoring or parameter to be used for discriminatory analysis Whether correct, whether model is consistent with actual, calculate whether restrain, the most consistent with existing conclusion etc.；

(4) boundary condition and original upload condition are set.Carry out initial boundary conditions setting, retrain rock sample axle To initial displacement, model is applied one and fixes confined pressure load, computing 500 time step is set, calculate and set up at the beginning of model Beginning poised state；

(5) cell cube carries out the most at the uniform velocity load calculating solve, Time step is set, when reaching setting Calculate during computing time step and terminate.During solving calculating, if unit model enters the residual strength stage, The material parameter then calculated model is modified and after reduction, proceeds subsequent calculations.

(6) the load-deformation curve change of griotte under certain fixing confined pressure load is obtained by above procedure numerical simulation Change process.Change the size of applied confined pressure load, repeat aforesaid numbered analog simulation process, obtain Griotte load-deformation curve change procedure under different confined pressures.

Finally use the credibility of actual measurement acoustic velocity checking computations numerical simulation.

At the scene country rock is launched sound wave, hole cinclides 1#, 2#, 3#, 4#, 5# is carried out acoustic velocity test, Obtain the acoustic velocity value under different hole depth, owing to country rock has crack, have during sonic transmissions energy loss and The reduction of velocity of wave, when a certain maintenance level of velocity of wave convergence, then it is assumed that crack no longer occurs, departs from rock convergence measure District, thus obtains the rock convergence measure occurrence scope of actual measurement.Fig. 3 is actual measurement damage zone, 4# hole monitoring result, root Can be determined that its damage range is about 2.0m according to 4# hole velocity of wave band scope.Knot by above numerical simulation calculation Really, it is also possible to draw peak strength envelope and residual strength envelope, after reaching peak strength with stress path And the descending branch of obvious flex point occurs as the criterion of country rock breakage, therefore deduce that the lesion depths of country rock. As shown in Figure 4, for 4# pitch-row surrouding rock stress dynamic adjustment process away from excavation face 1m, 1.5m, 2m, 2.5m, Substantially falling occurs in 4# pitch-row surrouding rock stress away from excavation face 1.5m, and the surrouding rock stress at 2.0m is without substantially Flex point descending branch, therefore may determine that the lesion depths in 4# hole is about 2.0m.By the velocity of wave band institute to actual measurement The rock convergence measure scope judged compares with by the rock convergence measure scope obtained by numerical simulation, it can be seen that Compared to description method based on Mohr-Coulomb strength theory, use that this invention provided based on Hoke-Brown criterion utilizes finite difference calculus to carry out the description method of numbered analog simulation, result closer to Measured data, describes precision higher, and credible result degree is good.Measured result, based on Hoke-Brown this structure mould Type uses finite difference calculus to carry out numerical simulation and the contrast feelings described based on Mohr-Coulomb strength theory Condition is as shown in Figure 1.

Concrete example described herein is only to present invention spirit explanation for example.Technology neck belonging to the present invention The technical staff in territory can carry out required amendment, supplements or use similar side described instantiation Formula substitutes, but without departing from the spirit of the present invention or surmount scope defined in appended claims.

Accompanying drawing explanation

Fig. 1 is that new and old methods and results contrasts schematic diagram.

Fig. 2 is three axle confining pressure test schematic diagrams.

Fig. 3 is actual measurement damage zone, 4# hole monitoring result schematic diagram.

Fig. 4 is 4# pitch-row surrouding rock stress dynamic adjustment process schematic diagram at a certain distance from excavation face.

Above-described embodiment is used for illustrating the present invention rather than limiting the invention, in the essence of the present invention In god and scope of the claims, any modifications and changes that the present invention is made, both fall within the present invention's Protection domain.

Claims (3)

1. behind a griotte peak crisp prolong mould conversion mechanical characteristic numerical value method is described, it is characterised in that bag Include step:

Step 1, use Hoek-Brown constitutive model carry out to griotte crisp prolong mould conversion mechanical characteristic retouch State, it is allowed to m after rock mass surrender_b, s, a equal strength parameter is along with plastic strainAccumulation and change, in order to Strengthening and the softening behavior of material after surrendering are described.Softening and hardening description is introducing one and minimum principal stress σ₃Relevant zoom factor μ, is used for describing m under different confined pressure level_b, s, a equal strength parameter is along with plasticity StrainVariation characteristic；

Step 2, takes griotte rock sample test piece and carries out confined pressure loading experiment in indoor, it is thus achieved that power behind the peak of griotte Learn characteristic and the mechanics parameters of griotte；

Step 3, uses finite difference calculus to carry out numbered analog simulation, creates geometric model, definition material model For Hoek-Brown model, according to the mechanics parameters Definition Model material parameter above obtained；Arrange The boundary condition of model, then applies confined pressure to unit model, the most at the uniform velocity loads, finally solve and tied Really, then the load-deformation curve of griotte under this confined pressure is obtained；

Step 4, changes the size of applied confined pressure load, repeats above-mentioned numbered analog simulation process, Obtain one group of griotte load-deformation curve under different confined pressures.

Step 5, utilizes the credibility of actual measurement velocity of wave checking computations numerical simulation result, and the velocity of wave band that will survey is sentenced Fixed rock convergence measure scope compares with by the rock convergence measure scope obtained by the method for numerical simulation.

Behind a kind of griotte peak the most according to claim 1, crisp prolonging moulds the numerical value description changing mechanical characteristic Method, it is characterised in that: step 1 farther includes sub-step:

Step 1-1: based on Hoek-Brown criterion of strength, proposes a kind of relevant to Rock Damage degree non- Fixing flow rule, the pare-debris flow body of its constitutive model is:

${\mathrm{\σ}}_1={\mathrm{\σ}}_3+{\mathrm{\σ}}_{ci}{(m_b\frac{{\mathrm{\σ}}_3}{{\mathrm{\σ}}_1}+s)}^a---\left(1\right)$

Model supposes maximum plastic strain incrementWith minimum plastic strain incrementMeet following relation:

${\mathrm{\Δ\ϵ}}_1^p={\mathrm{\γ\Δ\ϵ}}_3^p---\left(2\right)$

In formula: σ₁、σ₃It is respectively minimum and maximum principal stress during rock mass surrender；σ_ciList for sillar test specimen Axle comprcssive strength；m_b, s and a be and rock-mass quality scoring GSI and sillar material parameters m_iRelevant parameter；γ For the factor relevant to stress level.

Step 1-2: introduce 4 kinds of flow rules according to stress level Hoek-Brown model:

(1) associated flow, describes the yield characteristics under the conditions of low confined pressure, and now the volumetric strain of rock mass increases Long the fastest, and associated flow criterion can guarantee that bulk strain is farthest increased theoretically.Association The flow rule of flowing is:

${\mathrm{\Δ\ϵ}}_i^p=-\mathrm{\γ}\frac{\∂F}{\∂{\mathrm{\σ}}_i}---\left(3\right)$

By formula (1), (3) are brought formula (2) into and can are in the hope of the factor gamma of associated flow:

${\mathrm{\γ}}_{af}=-\frac{1}{1+{\mathrm{am}}_b{(m_b\frac{{\mathrm{\σ}}_3}{{\mathrm{\σ}}_1}+s)}^{a-1}}---\left(4\right)$

(2) equal-volume flowing criterion, when confined pressure increases to confined pressure higher limitAdd in follow-up after sillar surrender During load, volume keeps constant, for describing the yield characteristics under high confining pressure.Flow rule expression formula is:

γ_cv=-1 (5)

(3) Radial Flow rule, describes the extensional under sillar tension and destroys.Flow rule is:

${\mathrm{\γ}}_{rf}=\frac{{\mathrm{\σ}}_1}{{\mathrm{\σ}}_3}---\left(6\right)$

(4) combination flowing, when confined pressure isFlow rule after sillar surrender should be between associated flow And between equal-volume flowing, therefore use combination flowing criterion to be been described by.Combination flow rule is:

$\mathrm{\γ}=\frac{1}{\frac{1}{{\mathrm{\γ}}_{af}}+(\frac{1}{{\mathrm{\γ}}_{cv}}-\frac{1}{{\mathrm{\γ}}_{af}})\frac{{\mathrm{\σ}}_3}{{\mathrm{\σ}}_3^{cv}}}---\left(7\right)$

Step 1-3: softening and introducing one and minimum principal stress σ in hardening description₃Relevant zoom factor μ, is used for describing m under different confined pressure level_b, s, a equal strength parameter is along with plastic strainVariation characteristic.

Behind a kind of griotte peak the most according to claim 1, crisp prolonging moulds the numerical value description changing mechanical characteristic Method, it is characterised in that: step 3 farther includes following sub-step:

Step 3-1: carry out numbered analog simulation based on finite difference calculus, creates initial three-dimensional element body geometry mould Type；

Step 3-2: the material model in definition unit body region is Hoek-Brown model, according to indoor examination Test the material parameter in obtained mechanics parameters definition Hoek-Brown model；

Step 3-3: monitoring variable or parameter is set, the most correct for discriminatory analysis, model whether with reality Be consistent, calculate whether restrain, the most consistent with existing conclusion etc.；

Step 3-4: arrange boundary condition and original upload condition, applies a certain confined pressure load and carries out initial balance Solve, set up the poised state of model initialization；

Step 3-5: the most at the uniform velocity load calculating and solve, Time step is set, when the computing time step reaching setting Time calculate terminate.During solving calculating, if model of element enters the residual strength stage, then to model The material parameter calculated is modified and after reduction, proceeds subsequent calculations；

Step 3-6: result output and analysis, draws the griotte stress-strain song that curve obtains under this confined pressure Line.