CN111855412B - Rock burst tendency grade discrimination method based on stress energy ratio - Google Patents
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Abstract
The invention relates to a rock burst tendency grade discrimination method based on a stress energy ratio, which comprises the following steps: s1, preparing a cylindrical sample from a rock block; s2, carrying out uniaxial compression test on the sample to obtain a stress-strain curve and uniaxial compressive strength sigma of the rock sample c S3, carrying out a uniaxial cyclic loading test to obtain axial stress strain values of different cycles; s4, calculating a difference value of strain values corresponding to the same stress in the cyclic loading stage, and drawing an axial strain difference-stress curve; s5, defining original strain, and calculating original strain energy Ea and total input energy E at peak point T (ii) a S6 defines residual strain energy Es = E T -Ea; the difference between the stress at the peak point and the original stress is the stress intensity difference sigma p (ii) a S7, calculating the stress-energy ratio W E (ii) a S8 when W E No rock burst tendency exists when the number is less than 4; when 4 < W E If the value is less than 5.5, the rock burst tendency is medium or low; when W E The rock burst tendency is serious when the rock burst is more than 5.5; the invention realizes the prejudgment of the rock burst risk.
Description
Technical Field
The invention relates to the technical field of rock burst tendency grade judgment, in particular to a rock burst tendency grade judgment method based on stress energy ratio indexes.
Background
With the increase of the mining depth of the mine, the condition of the ore rock and the mining environment gradually deteriorate, and the rock burst is more and more a power disaster which is difficult to avoid and frequently occurs in the mining process. Rock burst is a phenomenon that when a high ground stress area engineering is excavated or mined, elastic deformation potential energy accumulated in a rock mass is suddenly and violently released under a certain condition to cause the rock to burst and be ejected, and the phenomenon occurs all the time in the engineering of mining, railway construction, tunnel construction and the like. When rock burst happens, serious damage, equipment damage and casualties of an excavation working face are often caused, the project progress is influenced, and great economic loss is caused. In order to prevent the damage caused by the rock burst, scholars at home and abroad successively put forward more than 10 hypotheses and criteria, analyze the rock burst phenomenon from the aspects of strength, rigidity, energy, stability, fracture, damage, fractal and the like, illustrate the generation mechanism of the rock burst, point out the necessary conditions for the generation of the rock burst, and lay the theoretical basis for the prediction and prevention work of the rock burst. Most of the criteria consider the rock burst tendency from a single perspective, and the rock serves as a bearing body for the occurrence of rock burst disasters, and the elastic brittleness and the energy storage characteristic of the rock are main intrinsic factors for triggering rock bursts. Therefore, if the strength and the energy of the rock can be comprehensively considered, the rock burst tendency grade of the rock material can be more accurately judged.
Disclosure of Invention
The invention aims to judge the rock burst tendency by utilizing the ratio of the stress intensity difference to the residual strain energy, and provides a rock burst tendency grade judging method based on the stress energy ratio index so as to avoid serious damage of an excavation working surface, equipment damage and casualties caused by rock burst.
The specific scheme of the invention is as follows: a rock burst tendency grade discrimination method based on stress energy ratio is characterized by comprising the following steps: the method comprises the following steps:
s1: taking at least two rock blocks, and processing the obtained rock blocks to prepare a cylindrical sample;
s2: one sample is subjected to uniaxial compression test loading until failure, and the stress-strain curve and uniaxial compression resistance of the rock sample are obtainedIntensity sigma c ;
S3: another specimen was subjected to a uniaxial cyclic loading test by axially loading the specimen through a press at a rate to a peak load set at 0.5 σ c Unloading to a set value at the same speed, and cycling for at least three times to obtain axial stress strain values of different cycles;
s4: calculating the difference value of the strain value corresponding to the same stress in the cyclic loading stage, and drawing an axial strain difference-stress curve, wherein the stress corresponding to the position of a turning point of the curve is the original stress of the rock;
s5: defining the strain value on the stress-strain curve corresponding to the original stress as the original strain, and calculating the original strain energy Ea at the original stress point and the total input energy E at the peak point on the stress-strain curve T ；
S6: defining the difference value of the total input energy and the original strain energy as residual strain energy Es = E T -Ea; the difference between the stress at the peak point and the original stress is the stress intensity difference sigma p ；
S7: according to the residual strain energy Es and the stress intensity difference sigma p Calculating the stress energy ratio W E ，W E =σ p /Es；
S8: according to the stress energy ratio W E Judging the rock burst tendency grade when W is E When the number is less than 4, the rock burst tendency is avoided; when 4 < W E If the value is less than 5.5, the rock burst tendency is medium or low; when W is E Above 5.5, there is a tendency for severe rock burst.
Further, the cylindrical sample in the step S1 is a standard sample with a diameter of 50mm and a height of 100mm, the sample should ensure that the error of the non-parallelism of the two end surfaces is less than 0.05mm, the error of the diameter along the height of the sample is less than 0.3mm, the end surfaces should be perpendicular to the axis of the sample, and the deviation is less than 0.25 °.
Further, in the step S2, a uniaxial compression test is carried out on the cylindrical sample, the cylindrical rock-shaped sample is placed on a rigid electro-hydraulic servo material control testing machine and is loaded to be damaged at the speed of 0.001mm/S, and a stress-strain curve and uniaxial compressive strength sigma of the rock sample are obtained c 。
Further, the method comprisesAnd in the step S3, a uniaxial cyclic loading test is carried out on the cylindrical sample, the sample is vertically loaded to a peak load at the speed of 0.001mm/S through the testing machine, and the peak load of each cycle is set to be sigma c And then unloaded to 2kN at the same rate for a total of 3 cycles.
Further, in the step S4, the strain values corresponding to the same stresses in the second and third cyclic loading stages are subtracted to form an axial strain difference-stress curve, and the stress corresponding to the inflection point position is the original stress.
Further, the original strain energy Ea of the rock sample at the original stress point in the step S5 is a value of an area enclosed by the stress-strain curve at the original stress point and the abscissa axis; total input energy E of rock sample at the peak point T The stress-strain curve is a value of an area enclosed by the abscissa axis and the peak point.
The principle of the invention is as follows: since the rock sample is subjected to pressure from the surrounding rock before the bottom of the ground is excavated and is memorized in the form of cracks, when the stress memorized in the indoor uniaxial compression test is not reached, the rock does not generate new cracks, and energy is not accumulated. Drawing an axial strain variation-stress curve by performing a uniaxial cyclic loading test, measuring the original stress of the rock sample, calculating the difference value between the peak stress and the original stress, namely the stress intensity actually required by the energy accumulated by the rock, and defining the stress intensity difference as the stress intensity difference sigma p (ii) a Defining the point on the stress-strain curve corresponding to the original stress as original strain, calculating the area under the curve at the original stress point on the stress-strain curve, defining the area under the curve as original strain energy Ea, calculating the total input energy E at the peak stress point T The difference value of the original strain energy Ea is the energy actually accumulated in the rock in the uniaxial compression process, the energy is defined as residual strain energy Es, and then a stress-energy ratio W is calculated E The rock burst tendency can be used as a basis for judging the rock burst tendency.
The method has the beneficial effects that key factors causing rock burst are comprehensively considered: stress and energy, and provides a rock burst tendency judging method based on stress-energy ratio indexes, rock burst risk levels are pre-judged before construction, and serious damage, equipment damage and casualties of an excavation working face caused by rock burst can be avoided.
Drawings
FIG. 1 is a schematic flow chart of a rock burst tendency grade determination method according to the present invention;
FIG. 2 is a diagram of uniaxial compressive stress-strain curves of a rock;
FIG. 3 is a schematic diagram of a rock cyclic loading scheme;
FIG. 4 is a graph of strain difference versus stress curves;
FIG. 5 shows the residual strain energy Es and the stress-intensity difference σ of the rock p A method map is determined.
Detailed Description
Example one
In this embodiment, taking granite spangle as an example, the specific steps are as follows:
1. processing the rock blocks retrieved from the engineering site into cylindrical rock samples with the diameter of 50mm and the length of 100mm, taking 3 samples with the same specification, placing the samples in an INSTRON1346 electro-hydraulic servo material testing machine for a conventional uniaxial compression test, loading the samples to be damaged at the speed of 0.001mm/s, and measuring the average uniaxial compression strength and stress strain curve, sigma, of the marble c =85.31MPa;
2. The specimens were subjected to a uniaxial cyclic loading test at a rate of 0.001mm/s to a peak load of 42.66MPa (i.e., 0.5. Sigma./s) c ) Then unloaded to 2kN at a rate of 0.001mm/s, and cycled 3 times. Subtracting the strain values corresponding to the same stress in the loading stage of the second cycle and the third cycle to obtain an axial strain difference-stress curve of the rock sample, wherein the stress corresponding to the inflection point position of the curve is the original stress of the rock, and the original stress of the granite spangle is 19.28MPa;
3. finding out an original strain point corresponding to the original stress on the stress-strain curve of the granite spangle, and integrating the area between the original stress point and the abscissa on the stress-strain curve to obtain the original strain energy Ea =0.66KJ/m3 of the granite spangle; integrating the area between the peak point and the abscissa on the stress-strain curve to obtain the total input energy E of the marble T =15.45KJ/m3；
4. Calculating the stress intensity difference sigma of the sample P And residual strain energy Es, wherein the stress intensity difference σ P Difference between peak stress and original stress, σ P =66.13MPa; residual strain energy Es is the difference between the total input energy and the original strain energy, es =14.79KJ/m3.
5. According to the formula W E =σ p Calculated stress-energy ratio W of/Es E The stress energy ratio of the granite spangle can be obtained
=4.48。
6. According to the grading standard, the rock burst tendency of the granite spangle is medium or low;
7. in order to improve the accuracy of judging the rock burst tendency, the same rock is tested by taking two samples according to the steps, three stress energy ratios are respectively obtained and an average value is taken to be used as a basis for judging the rock burst tendency. Results the stress energy ratio W of the three tests on granite spangle is shown in the following table E The calculation results are respectively 4.48, 4.69 and 4.96, and the average value of the stress energy ratios of the three tests is 4.71, so the judgment result of the rock burst tendency of the granite spangle is the medium and low rock burst tendency.
Example two
In this embodiment, the white marble is taken as an example, the specific steps are the same as those in the first embodiment, and the stress-energy ratio W of three samples E The calculation results are respectively 3.91, 3.74 and 3.98, and the average value is 3.88, so the judgment result of the rock burst tendency of the white marble is no rock burst tendency, and the specific calculation results are shown in the following table:
EXAMPLE III
This example uses two-long flash length of quartzPorphyrite as an example, the specific procedure is the same as in example one, the stress energy ratio W of three samples E The calculation results are respectively 6.02, 6.19 and 5.89, and the average value is 6.03, so the judgment result of the rock burst tendency of the white marble is a serious rock burst tendency, and the specific calculation results are shown in the following table:
the first, second and third embodiments respectively judge the rock burst tendency grade of the three rock materials, and the obtained result is the same as that obtained by the Barton criterion and accords with the actual situation, so that the effectiveness and the accuracy of the judging effect of the invention can be proved according to the results.
Claims (3)
1. A rock burst tendency grade discrimination method based on stress energy ratio is characterized by comprising the following steps: the method comprises the following steps:
s1: taking at least two rock blocks, and processing the obtained rock blocks to prepare a cylindrical sample;
s2: one sample is subjected to uniaxial compression test loading until failure, and the stress-strain curve and uniaxial compressive strength sigma of the rock sample are obtained c ;
S3: another specimen was subjected to a uniaxial cyclic loading test by axially loading the specimen through a press at a rate to a peak load set at 0.5 σ c Unloading to a set value at the same speed, and cycling at least three times to obtain axial stress strain values of different cycles;
s4: calculating the difference value of the strain value corresponding to the same stress in the cyclic loading stage, and drawing an axial strain difference-stress curve, wherein the stress corresponding to the position of a turning point of the curve is the original stress of the rock;
s5: defining the strain value on the stress-strain curve corresponding to the original stress as the original strain, and calculating the original strain energy Ea at the original stress point and the total input energy E at the peak point on the stress-strain curve T ；
S6: defining the difference between the total input energy and the original strain energy as residual strain energy Es=E T -Ea; the difference between the stress at the peak point and the original stress is the stress intensity difference sigma p ；
S7: according to the residual strain energy Es and the stress intensity difference sigma p Calculating the stress energy ratio W E ，W E =σ p /Es；
S8: according to stress energy ratio W E Judging the rock burst tendency grade when W is E When the number is less than 4, the rock burst tendency is avoided; when 4 < W E When the frequency is less than 5.5, the rock burst tendency is medium or low; when W E Above 5.5, there is a tendency for severe rock burst.
2. The method for judging the rock burst tendency grade based on the stress energy ratio as claimed in claim 1, which is characterized in that: the cylindrical test piece in the step S1 is a standard test piece with the diameter of 50mm and the height of 100mm, the parallelism error of two end faces of the test piece is less than 0.05mm, the diameter error along the height of the test piece is less than 0.3mm, and the verticality deviation of the end faces is less than 0.25 degrees.
3. The method for judging the rock burst tendency grade based on the stress energy ratio as claimed in claim 1, which is characterized in that: and S2, performing uniaxial compression test on the cylindrical sample, placing the cylindrical rock sample on a rigid electro-hydraulic servo material control testing machine, and loading the cylindrical rock sample to be damaged at the speed of 0.001mm/S to obtain a stress-strain curve and uniaxial compressive strength sigma of the rock sample c 。
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| CN106248508A (en) * | 2016-08-11 | 2016-12-21 | 何满潮 | The experimental technique of simulated strain rock burst |
| CN107991184A (en) * | 2017-11-27 | 2018-05-04 | 中南大学 | A kind of Rock burst proneness Grade Judgment based on residual elasticity strain energy index |
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| CN107991184A (en) * | 2017-11-27 | 2018-05-04 | 中南大学 | A kind of Rock burst proneness Grade Judgment based on residual elasticity strain energy index |
| CN110044716A (en) * | 2019-02-02 | 2019-07-23 | 中南大学 | Rock burst proneness Grade Judgment of the response lag than index is unloaded based on adding |
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