CN106353836A - Method for forecasting rock burst on basis of releasable elastic strain energy - Google Patents

Abstract

The invention discloses a method for forecasting rock burst on the basis of releasable elastic strain energy. The method includes steps of 1, building surrounding rock stress computational models, analyzing stress states of excavated surrounding rock and computing elastic strain energy U<1> of the excavated surrounding rock; 2, computing surrounding rock wing crack propagation energy dissipation U<t> and friction energy dissipation W<f> of main crack surfaces; 3, acquiring energy storage limit values U<0> loaded on rock mass under different confining pressures; 4, acquiring the releasable elastic strain energy U<e> of the cracked surrounding rock and computing ratios U<e>/U<0> of the releasable elastic strain energy of the cracked surrounding rock and energy storage limit of the surrounding rock and pre-judging whether rock burst of the surrounding rock is about to occur or not according to the ratios. The method for forecasting rock burst on the basis of the releasable elastic strain energy has the advantages that problems of incapability of effectively predicting rock burst occurrence disaster stages and insufficient accuracy can be solved by the aid of the method; rock burst can be accurately and reliably forecast by the aid of the method, and energy gathering, dissipating and releasing characteristics can be truly and objectively embodied in surrounding rock excavation procedures.

Description

A kind of Burst Prediction method based on releasable elastic strain energy

Technical field

The present invention relates to during the Underground Engineering Excavation of deep rock burst forecast field, especially a kind of should based on releasably elasticity Become the Burst Prediction method of energy.

Background technology

Underground engineering construction rule under China's economic construction at a high speed background of rapid development, under great burying, high-ground stress environment Mould is increasing, and engineering type is numerous, including mining engineering, Underground Excavation Cluster of Hydropower Station, Tunnel Engineering, nuclear waste srorage base Ground etc..Rigid brittle rock mass in great burying, high-ground stress environment often has higher elastic strain energy, is opened in protolith When digging off-load, country rock occurs stress concentration, also can experience gathering, dissipating and release process of energy, the bullet assembled when rock mass Property strain can exceed that rock mass limit storage can when, at the wall of hole, part rock mass by suddenly, eject fiercely, produces a kind of dynamic Power unstable phenomenon rock burst, a kind of Geological Hazard of rock burst, often threaten the safety of workmen and equipment, impact is applied Work progress.The anticipation criterion mainly having 2 classes different at present is applied to the forecast of rock burst:

(1) generation of rock burst is relevant with surrouding rock stress.With russenes rock burst anticipation method (stress index σ_θ/σ_c) as a example, σ_θ For the maximum tangential stress of cavern, σ_cFor rock uniaxiality strength；

(2) generation of rock burst is relevant with energy.Kidybinski rock burst anticipation method (elastic energy index w_et) application is more Extensively, w_etDefinition be elastic rock test specimen during stress deformation, reach the elastic strain energy of accumulation before peak strength φ_spConsume strain energy φ with unloading gained_stRatio.

Above 2 kinds of anticipation criterions are as shown in table 1:

1 two kinds of rock burst criterions of table

The generation process of rock burst substantially can be divided into two parts, collapse stage: when surrouding rock stress reaches the strong ultimate value of rock When, rock ruptures, and cracks or slide surface；The disaster stage: when the strain gathered in country rock can exceed that the energy storage of rock mass During the limit, at the wall of hole, unstability is ejected by part rock mass, that is, produce Rock-burst.Stress index σ_θ/σ_cIt is answering with rock Set up based on force intensity theory, simple and practical, the collapse stage of rock burst generation can be described, but rock can not be predicted well The outburst raw disaster stage.In rock mass, the gathering of strain energy is the principal element that rock burst produces, energy indexes w_etFoundation with energy Based on amount theory, can preferably reflect the Energy Mechanism that rock burst produces, but also have its limitation, elastic energy index w_etInstead Reflect is elastic strain energy φ in rock mass_spConsume strain energy φ with unloading gained_stRatio, fail embody the rock burst hazard stage The mechanism producing, that is, excavate releasable elastic strain energy u of rock mass after off-load_eMore than energy storage limit u₀, and this criterion is mainly suitable for To as if coal petrography, and rock burst mostly occurs in buried rigid brittle rock mass, therefore elastic energy index w_etIt is not necessarily suitable hard rock Rock burst anticipation.Therefore, using stress index σ_θ/σ_cWith nergy Index w_etGeneration to forecast rock burst is not accurate.

Content of the invention

The technical problem to be solved is to provide a kind of Burst Prediction method based on releasable elastic strain energy, Solution must not can predict the disaster stage that rock burst occurs well, not accurate problem, can more accurately and reliably forecast The generation of rock burst, and can more objective embody gathering, dissipating and release characteristic of energy in country rock digging process.

For solving above-mentioned technical problem, the technical solution adopted in the present invention is: one kind is based on releasable elastic strain energy Burst Prediction method, the method comprises the following steps:

Step 1: based on initial in-site stress field and tunnel excavation transverse shape, set up stress of surrounding rocks Calculation model, analysis The stress state of country rock after excavation, and calculate elastic strain energy u of country rock after excavation₁；

Step 2: assume that there is length in country rock is 2a and tunnel initial micro-crack radially at an angle β, with tunnel center Distance be r, crackle is in radial normal stress σ_θWith ring direct stress σ_rUnder two-way action of compressive stress, calculate country rock wing crackle and expand Exhibition power consumption u_tAnd the friction energy-dissipating w on lead crack face_f；

Step 3: carry out drill hole sampling to excavating rock mass region, rock sample is carried out with the mechanical property examination under different confined pressures Test, obtain energy storage ultimate value u that rock mass loads under different confined pressures₀；

Step 4: based on law of conservation of energy, by country rock strain energy density u₁Energy in middle deduction country rock dehiscence process Amount dissipation value u_d, you can obtain releasable elastic strain energy u after country rock cracking_e；After calculating country rock cracking, releasably elasticity should Change can be with the ratio u of its energy storage limit_e/u₀, whether rock burst is occurred with this anticipation country rock.

The calculating process of step 1 is: in initial in-site stress field it is assumed that stress value is p₀Under conditions of, excavate in protolith Article one, radius is the circular endless tunnel of r, after Elasticity midplane stress method can solve excavation country rock the 1st, the 2nd, the 3rd principal stress (σ₁、σ₂、σ₃), ring direct stress σ_θ, radial normal stress σ_rEffective shear stress τ and between crack surface_eff, by country rock Stress state can be calculated country rock elastic strain energy density u after excavation₁, as formula (1):

$u_1=p_0^2\&lsqb;3(1-2v)+2(1+v)r^4/r^4\&rsqb;/2e---\left(1\right)$

In formula: v is Poisson's ratio, e is elastic modelling quantity.

In step 2, it is set in that to there is length in country rock be that 2a and tunnel are radially at an angle β and distance of tunnel center is r Initial micro-crack, by country rock cracking model analyze excavate off-load cause country rock cracking scope r_cWith wing crack extending length l, And calculate country rock wing cracks can spread power consumption u_tAnd the friction energy-dissipating w on lead crack face_f, corresponding calculating process is as follows:

$r_c={\&lsqb;\frac{2{\mathrm{a\&xi;p}}_{0}cos\mathrm{\&beta;}(sin2\mathrm{\&beta;}-\mathrm{\&mu;}cos2\mathrm{\&beta;})}{\sqrt{{\mathrm{\&pi;l}}_{*}}{\mathrm{\&sigma;}}_c+2{\mathrm{a\&xi;\&mu;p}}_{0}cos\mathrm{\&beta;}}\&rsqb;}^{\frac{1}{2}}r---\left(2\right)$

Wing crack extending length l and the implicit relationship apart from r, as formula (3):

$\frac{{\mathrm{\&sigma;}}_c}{\mathrm{\&xi;}}=\frac{2{\mathrm{ap}}_0\{\frac{r^2}{r^2}sin2\mathrm{\&beta;}-\mathrm{\&mu;}\&lsqb;1+\frac{r^2}{r^2}cos2\mathrm{\&beta;}\&rsqb;\}cos\mathrm{\&beta;}}{\sqrt{\mathrm{\&pi;}(l+l_{*})}}-p_0(1-\frac{r^2}{r^2})\sqrt{\mathrm{\&pi;}l}---\left(3\right)$

$\begin{array}{c}{u}_t=\frac{8a^2(1-v^2)}{\mathrm{\&pi;}e}\{{\mathrm{\&tau;}}_{eff}^2\ln (1+\frac{l}{l_{*}})+\frac{1}{8}{\mathrm{\&sigma;}}_r^2{\left(\frac{\mathrm{\&pi;}l}{a}\right)}^2-{\mathrm{\&pi;\&tau;}}_{eff}{\mathrm{\&sigma;}}_r\cos \mathrm{\&beta;}\left(\frac{l_{*}}{a}\right)\\ \&lsqb;\sqrt{\left(\frac{l}{l_{*}}\right(1+\frac{l}{l_{*}}\left)\right)}-\ln (\sqrt{\frac{l}{l_{*}}}+\sqrt{(1+\frac{l}{l_{*}})})\&rsqb;\}\end{array}---\left(4\right)$

$\begin{array}{c}{w}_f=\frac{4\sqrt{2}{a}^2\mathrm{\&mu;}(1-v^2)}{e}\&centerdot;\{2({\mathrm{\&tau;}}_{eff}{\mathrm{\&sigma;}}_{\mathrm{\&theta;}}{\cos }^2\mathrm{\&beta;}+{\mathrm{\&tau;}}_{eff}{\mathrm{\&sigma;}}_r{\sin }^2\mathrm{\&beta;})\sqrt{\left(\frac{l+l_{**}}{l+l_{*}}\right)}\\ -\frac{(\sqrt{2}-1)({\mathrm{\&sigma;}}_{\mathrm{\&theta;}}{\mathrm{\&sigma;}}_r\cos \mathrm{\&beta;}+{\mathrm{\&sigma;}}_r^2\tan \mathrm{\&beta;}\sin \mathrm{\&beta;})}{\sqrt{2}}\&centerdot;\frac{{\mathrm{\&pi;l}}_{**}}{a}\sqrt{\left(\frac{l}{l_{**}}\right(1+\frac{l}{l_{**}}\left)\right)}\}\end{array}---\left(5\right)$

In above-mentioned formula: μ is coefficient of friction；σ_cFor comprcssive strength；ξ is comprcssive strength σ_cWith crackle arrest toughness k_icRatio Value, ξ=σ_c/k_ic, the span generally 55～82 of ξ；l_*=0.27a, l_**=0.083a, l_*And l_**It is to ensure that stress Intensity factor computing formula is still suitable in wing crackle very little.

In step 3, obtain energy storage ultimate value u that rock mass loads under different confined pressures₀Step be:

Step 3-1: to excavate rock mass region carry out drill hole sampling it is ensured that the height of sample, diameter, flatness, fineness, The depth of parallelism reaches rock test codes and standards；

Step 3-2: the rock sample of 4 groups of Pass Test standards of selection carries out multigroup on servo-controlled rigidity matching Conventional triaxial compression test under different confined pressures, obtains the triaxial compressions intensity of rock mass, records answering of rock sample mechanical property Force-strain curve；

Step 3-3: the routine three under multigroup difference confined pressure that rock sample is chosen in step 3-2 is calculated respectively using formula (6) Energy storage ultimate value u of axle compression test₀.

$u_0=\&lsqb;{\mathrm{\&sigma;}}_1^2+{\mathrm{\&sigma;}}_2^2+{\mathrm{\&sigma;}}_3^2-2v({\mathrm{\&sigma;}}_1{\mathrm{\&sigma;}}_2+{\mathrm{\&sigma;}}_2{\mathrm{\&sigma;}}_3+{\mathrm{\&sigma;}}_1{\mathrm{\&sigma;}}_3)\&rsqb;/2e---\left(6\right)$

In step 3-1, bored sample as cylindrical specimens, cylindrical specimens a size of diameter 50mm, high 100mm.

In step 3-2, choose 4 groups of confined pressures, respectively 10mpa, 20mpa, 30mpa and 40mpa.

Step 4 also includes:

Step 4-1: energy dissipation value u in country rock dehiscence process_dBy the country rock wing cracks can spread power consumption calculating in step 2 u_tAnd the friction energy-dissipating w on lead crack face_fTry to achieve, i.e. u_d=u_t+w_f；

Step 4-2: releasable elastic strain energy u after country rock cracking_eBy country rock strain energy density u₁With energy dissipation value u_dAsk , i.e. u_e=u₁-u_d.

The principle of the inventive method is:

Releasable elastic strain energy u within when rock mass_eExceed energy storage ultimate value u of rock mass₀When, rock burst will occur.As formula (7):

u_e/u₀>1 (7)

A kind of Burst Prediction method based on releasable elastic strain energy that the present invention provides, has the beneficial effect that:

1st, can more objective embody gathering, dissipating and release characteristic, instead of energy in country rock digging process Reflect the mechanism of rock burst generation.

2nd, the rock property scope being suitable for is wider, is applicable not only to coal petrography, is more applicable for buried rigid brittle rock mass (rock Quick-fried high frequency area).

3rd, can more accurately and reliably forecast the generation of rock burst, can be widely applied to the deep underground such as mining, water power, traffic Engineering.

The inventive method from the angle objective of energy embody the gathering of energy country rock digging process, dissipate and Release characteristic, elaborates the mechanism that rock burst produces.With existing stress index σ_θ/σ_cWith elastic energy index w_etPrediction for Rock Burst Method is compared, and forecast result is more accurately and reliably.

Brief description

The invention will be further described with reference to the accompanying drawings and examples:

The stress of surrounding rocks Calculation model schematic that Fig. 1 is set up by the embodiment of the present invention one step 1；

Fig. 2 is country rock cracks can spread schematic diagram in the embodiment of the present invention one step 2；

Fig. 3 is country rock cracking scope schematic diagram in the embodiment of the present invention one step 2；

Fig. 4 is country rock wing crack extending length schematic diagram in the embodiment of the present invention one step 2；

Fig. 5 is rock sample load-deformation curve schematic diagram under the different confined pressures obtaining in the embodiment of the present invention one step 3；

Fig. 6 is the embodiment of the present invention one rock mass energy with distance change schematic diagram；

Fig. 7 is that the embodiment of the present invention two adopts different method forecast result contrast schematic diagrams.

Specific embodiment

Embodiment one

Engineering background:

Excavate a circular tunnel (there is great burying, high-ground stress) in somewhere, tunnel radius is r=5m, At tunnel, initial field stress value is p₀=30mpa, Modulus of Elasticity of Rock Mass e=20gpa, Poisson's ratio ν=0.22, density p= 2500kg/m³, comprcssive strength σ_c=80mpa, initial micro-crack length 2a=0.004m, k_ic=σ_c/82.

A kind of Burst Prediction method based on releasable elastic strain energy, the method comprises the following steps:

Step 1: based on initial in-site stress field and tunnel excavation transverse shape, set up stress of surrounding rocks Calculation model, such as scheme 1, the stress state of country rock after analysis excavation, and calculate elastic strain energy u of country rock after excavation₁；

Step 2: assume that there is length in country rock is 2a and tunnel initial micro-crack radially at an angle β, with tunnel center Distance be r, as shown in Fig. 2 crackle is in radial normal stress σ_θWith ring direct stress σ_rUnder two-way action of compressive stress, analysis can obtain Direct stress σ on crack surface_β, shear stress τ_βWith effective shear stress τ_eff, work as τ_effWhen reaching certain marginal value, crackle starts to extend, By effective shear stress τ_effCalculate i type stress intensity factor k_i, work as k_iWhen reaching to a certain degree, the extension of wing crackle tends to steady Fixed, scope is ftractureed for r by the country rock that stress intensity factor solves_cWith wing crackle greatest length l respectively as shown in Figure 3 and Figure 4, exist On the basis of this, calculate country rock wing cracks can spread power consumption u_tAnd the friction energy-dissipating w on lead crack face_f, as shown in Figure 6；

Step 3: carry out drill hole sampling to excavating rock mass region, rock sample is carried out with the mechanical property examination under different confined pressures Test, obtain energy storage ultimate value u that rock mass loads under different confined pressures₀；

Step 4: based on law of conservation of energy, by country rock strain energy density u₁Energy in middle deduction country rock dehiscence process Amount dissipation value u_d, you can obtain releasable elastic strain energy u after country rock cracking_e, as shown in Figure 6.As seen from Figure 6, although portion Divide energy to dissipate in the form of friction energy and surface energy, but in country rock near region, especially in the range of cracking, still populated with is higher Releasable elastic strain energy.The ratio u of releasable elastic strain energy and its energy storage limit after calculating country rock cracking_e/u₀, Whether rock burst is occurred with this anticipation country rock.

As shown in figure 1, the calculating process of step 1 is: in initial in-site stress field it is assumed that stress value is p₀Under conditions of, The circular endless tunnel that a radius is r is excavated, after Elasticity midplane stress method can solve excavation in protolith Country rock the 1st, the 2nd, the 3rd principal stress (σ₁、σ₂、σ₃), ring direct stress σ_θ, radial normal stress σ_rEffective shear stress and between crack surface τ_eff, country rock elastic strain energy density u after excavation be can be calculated by the stress state of country rock₁, as shown in fig. 6, as formula (1):

$u_1=p_0^2\&lsqb;3(1-2v)+2(1+v)r^4/r^4\&rsqb;/2e---\left(1\right)$

In formula: v is Poisson's ratio, e is elastic modelling quantity.

In step 2, it is set in that to there is length in country rock be that 2a and tunnel are radially at an angle β and distance of tunnel center is r Initial micro-crack, by country rock cracking model analyze excavate off-load cause country rock cracking scope r_cWith wing crack extending length l, And calculate country rock wing cracks can spread power consumption u_tAnd the friction energy-dissipating w on lead crack face_f, corresponding calculating process is as follows:

$r_c={\&lsqb;\frac{2{\mathrm{a\&xi;p}}_{0}cos\mathrm{\&beta;}(sin2\mathrm{\&beta;}-\mathrm{\&mu;}cos2\mathrm{\&beta;})}{\sqrt{{\mathrm{\&pi;l}}_{*}}{\mathrm{\&sigma;}}_c+2{\mathrm{a\&xi;\&mu;p}}_{0}cos\mathrm{\&beta;}}\&rsqb;}^{\frac{1}{2}}r---\left(2\right)$

Wing crack extending length l and the implicit relationship apart from r, as formula (3):

$\frac{{\mathrm{\&sigma;}}_c}{\mathrm{\&xi;}}=\frac{2{\mathrm{ap}}_0\{\frac{r^2}{r^2}sin2\mathrm{\&beta;}-\mathrm{\&mu;}\&lsqb;1+\frac{r^2}{r^2}cos2\mathrm{\&beta;}\&rsqb;\}cos\mathrm{\&beta;}}{\sqrt{\mathrm{\&pi;}(l+l_{*})}}-p_0(1-\frac{r^2}{r^2})\sqrt{\mathrm{\&pi;}l}---\left(3\right)$

$\begin{array}{c}{u}_t=\frac{8a^2(1-v^2)}{\mathrm{\&pi;}e}\{{\mathrm{\&tau;}}_{eff}^2\ln (1+\frac{l}{l_{*}})+\frac{1}{8}{\mathrm{\&sigma;}}_r^2{\left(\frac{\mathrm{\&pi;}l}{a}\right)}^2-{\mathrm{\&pi;\&tau;}}_{eff}{\mathrm{\&sigma;}}_r\cos \mathrm{\&beta;}\left(\frac{l_{*}}{a}\right)\\ \&lsqb;\sqrt{\left(\frac{l}{l_{*}}\right(1+\frac{l}{l_{*}}\left)\right)}-\ln (\sqrt{\frac{l}{l_{*}}}+\sqrt{(1+\frac{l}{l_{*}})})\&rsqb;\}\end{array}---\left(4\right)$

$\begin{array}{c}{w}_f=\frac{4\sqrt{2}{a}^2\mathrm{\&mu;}(1-v^2)}{e}\&centerdot;\{2({\mathrm{\&tau;}}_{eff}{\mathrm{\&sigma;}}_{\mathrm{\&theta;}}{\cos }^2\mathrm{\&beta;}+{\mathrm{\&tau;}}_{eff}{\mathrm{\&sigma;}}_r{\sin }^2\mathrm{\&beta;})\sqrt{\left(\frac{l+l_{**}}{l+l_{*}}\right)}\\ -\frac{(\sqrt{2}-1)({\mathrm{\&sigma;}}_{\mathrm{\&theta;}}{\mathrm{\&sigma;}}_r\cos \mathrm{\&beta;}+{\mathrm{\&sigma;}}_r^2\tan \mathrm{\&beta;}\sin \mathrm{\&beta;})}{\sqrt{2}}\&centerdot;\frac{{\mathrm{\&pi;l}}_{**}}{a}\sqrt{\left(\frac{l}{l_{**}}\right(1+\frac{l}{l_{**}}\left)\right)}\}\end{array}---\left(5\right)$

In above-mentioned formula: μ is coefficient of friction；σ_cFor comprcssive strength；ξ is comprcssive strength σ_cWith crackle arrest toughness k_icRatio Value, ξ=σ_c/k_ic, the span generally 55～82 of ξ；l_*=0.27a, l_**=0.083a, l_*And l_**It is to ensure that stress Intensity factor computing formula is still suitable in wing crackle very little.

In step 3, obtain energy storage ultimate value u that rock mass loads under different confined pressures₀Step be:

Step 3-1: to excavate rock mass region carry out drill hole sampling it is ensured that the height of sample, diameter, flatness, fineness, The depth of parallelism reaches rock test codes and standards；

Step 3-2: the rock sample of 4 groups of Pass Test standards of selection carries out multigroup on servo-controlled rigidity matching Conventional triaxial compression test under different confined pressures, obtains the triaxial compressions intensity of rock mass, records answering of rock sample mechanical property Force-strain curve, as shown in Figure 5；

Step 3-3: the routine three under multigroup difference confined pressure that rock sample is chosen in step 3-2 is calculated respectively using formula (6) Energy storage ultimate value u of axle compression test₀.

$u_0=\&lsqb;{\mathrm{\&sigma;}}_1^2+{\mathrm{\&sigma;}}_2^2+{\mathrm{\&sigma;}}_3^2-2v({\mathrm{\&sigma;}}_1{\mathrm{\&sigma;}}_2+{\mathrm{\&sigma;}}_2{\mathrm{\&sigma;}}_3+{\mathrm{\&sigma;}}_1{\mathrm{\&sigma;}}_3)\&rsqb;/2e---\left(6\right)$

In step 3-1, bored sample as cylindrical specimens, cylindrical specimens a size of diameter 50mm, high 100mm.

In step 3-2, choose 4 groups of confined pressures, respectively 10mpa, 20mpa, 30mpa and 40mpa.

Step 4 also includes:

Step 4-1: energy dissipation value u in country rock dehiscence process_dBy the country rock wing cracks can spread power consumption calculating in step 2 u_tAnd the friction energy-dissipating w on lead crack face_fTry to achieve, i.e. u_d=u_t+w_f；

Step 4-2: releasable elastic strain energy u after country rock cracking_eBy country rock strain energy density u₁With energy dissipation value u_dAsk , i.e. u_e=u₁-u_d.

Embodiment two

Fig. 7 is the rock burst number of times of actual measurement and be respectively adopted existing predicting means and the inventive method during this tunnel excavation Burst Prediction number of times, it can be seen that comparing existing Burst Prediction method, using this invention provided based on can The Burst Prediction method of release elastic strain energy, closer to measured data, forecast precision is higher for forecast result.

Specific embodiment described herein is only explanation for example to present invention spirit.The affiliated technology of the present invention is led The technical staff in domain can be made various modifications, supplement or be replaced using similar mode to described specific embodiment Generation, but the spirit without departing from the present invention or surmount scope defined in appended claims.

Claims (7)

1. a kind of Burst Prediction method based on releasable elastic strain energy is it is characterised in that the method comprises the following steps:

Step 1: based on initial in-site stress field and tunnel excavation transverse shape, set up stress of surrounding rocks Calculation model, analysis is excavated The stress state of country rock afterwards, and calculate elastic strain energy u of country rock after excavation₁:

Step 2: assume that there is length in country rock is 2a and tunnel initial micro-crack radially at an angle β, crackle is away from tunnel center Distance be r, crackle is in radial normal stress σ_θWith ring direct stress σ_rUnder two-way action of compressive stress, calculate country rock wing crackle and expand Exhibition power consumption u_tAnd the friction energy-dissipating w on lead crack face_f；

Step 3: carry out drill hole sampling to excavating rock mass region, the conventional triaxial compression test under different confined pressures is carried out to rock sample, Obtain energy storage ultimate value u that rock mass loads under different confined pressures₀；

Step 4: based on law of conservation of energy, by country rock strain energy density u₁Energy consumption in middle deduction country rock dehiscence process Dissipate value u_d, you can obtain releasable elastic strain energy u after country rock cracking_e；Releasable elastic strain energy after calculating country rock cracking Ratio u with its energy storage limit_e/u₀, whether rock burst is occurred with this anticipation country rock.

2. a kind of Burst Prediction method based on releasable elastic strain energy according to claim 1 is it is characterised in that walk Rapid 1 calculating process is: in initial in-site stress field it is assumed that stress value is p₀Under conditions of, excavating a radius in protolith is r Circular endless tunnel, after Elasticity midplane stress method can solve excavation country rock the 1st, the 2nd, the 3rd principal stress (σ₁、σ₂、σ₃), ring direct stress σ_θ, radial normal stress σ_rEffective shear stress τ and between crack surface_eff, by the stress state of country rock Can be calculated country rock elastic strain energy density u after excavation₁, as formula (1):

In formula: ν is Poisson's ratio, e is elastic modelling quantity.

3. a kind of Burst Prediction method based on releasable elastic strain energy according to claim 1 is it is characterised in that walk In rapid 2, it is set in and in country rock, there is the initial fine fisssure that length is that 2a and tunnel are radially at an angle β and distance of tunnel center is r Stricture of vagina, is analyzed by country rock cracking model and excavates country rock cracking scope r that off-load causes_cWith wing crack extending length l, and calculate country rock Wing cracks can spread power consumption u_tAnd the friction energy-dissipating w on lead crack face_f, corresponding calculating process is as follows:

Wing crack extending length l and the implicit relationship apart from r, as formula (3):

In above-mentioned formula: μ is coefficient of friction；σ_cFor comprcssive strength；ξ is comprcssive strength σ_cWith crackle arrest toughness k_icRatio, ξ =σ_c/k_ic, the span generally 55～82 of ξ；l_*=0.27a, l_**=0.083a, l_*And l_**It is to ensure that stress intensity Factor computing formula is still suitable in wing crackle very little.

4. a kind of Burst Prediction method based on releasable elastic strain energy according to claim 1 is it is characterised in that walk In rapid 3, obtain energy storage ultimate value u that rock mass loads under different confined pressures₀Step be:

Step 3-1: carry out drill hole sampling it is ensured that the height of sample, diameter, flatness, fineness, parallel to excavating rock mass region Degree reaches rock test codes and standards；

Step 3-2: the rock sample choosing 4 groups of Pass Test standards carries out multigroup difference on servo-controlled rigidity matching Conventional triaxial compression test under confined pressure, obtain rock mass triaxial compressions intensity, record rock sample mechanical property stress-should Varied curve；

Step 3-3: the normal triaxial pressure under multigroup difference confined pressure that rock sample is chosen in step 3-2 is calculated respectively using formula (6) Energy storage ultimate value u of contracting test₀.

.

5. a kind of Burst Prediction method based on releasable elastic strain energy according to claim 4 it is characterised in that: In step 3-1, bored sample as cylindrical specimens, cylindrical specimens a size of diameter 50mm, high 100mm.

6. a kind of Burst Prediction method based on releasable elastic strain energy according to claim 4 it is characterised in that: step In rapid 3-2, choose 4 groups of confined pressures, respectively 10mpa, 20mpa, 30mpa and 40mpa.

7. a kind of Burst Prediction method based on releasable elastic strain energy according to claim 1 is it is characterised in that walk Rapid 4 also include:

Step 4-1: energy dissipation value u in country rock dehiscence process_dBy the country rock wing cracks can spread power consumption u calculating in step 2_tAnd Friction energy-dissipating w on lead crack face_fTry to achieve, i.e. u_d=u_t+w_f；

Step 4-2: releasable elastic strain energy u after country rock cracking_eBy country rock strain energy density u₁With energy dissipation value u_dTry to achieve, I.e. u_e=u₁-u_d.