CN111855412A - 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 the rock; s2 uniaxial compression test is carried out on the sample to obtain the stress-strain curve and uniaxial compressive strength sigma of the rock samplecS3, carrying out uniaxial cyclic loading test 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; s5 defines the original strain, calculates the original strain energy Ea and the total input energy E at the peak pointT(ii) a S6 defines residual strain energy Es = ET-Ea; the difference between the stress at the peak point and the original stress is the stress intensity difference sigmap(ii) a S7 calculating stress energy ratio WE(ii) a S8 when WENo rock burst tendency exists when the number is less than 4; when 4 < WEIf less than 5.5, the rock burst tendency is medium or low; when W isEThe rock burst tendency is serious when the rock burst is more than 5.5; the invention realizesAnd (4) prejudging 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, so that the rock bursts and is ejected out, and the phenomenon occurs 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 is used as a bearing body for the occurrence of rock burst disasters, and the elastic brittleness and the energy storage property of the rock are main intrinsic factors for triggering the rock burst. 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 of rocks 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 a 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 cylindrical samples;
s2: loading one sample to failure in uniaxial compression test to obtain the stress-strain curve and uniaxial compressive strength sigma of the rock samplec;
S3: the other sample was subjected to a uniaxial cyclic loading test by loading the sample axially through a press at a rate to a peak load set at 0.5 σcUnloading 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 the 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 curveT；
S6: defining the difference between the total input energy and the original strain energy as residual strain energy Es = ET-Ea; the difference between the stress at the peak point and the original stress is the stress intensity difference sigmap；
S7: according to the residual strain energy Es and the stress intensity difference sigmapCalculating the stress energy ratio WE，WE=σp/Es；
S8: according to stress energy ratio WEJudging the rock burst tendency grade when W isEWhen the number is less than 4, the rock burst tendency is avoided; when 4 < WEWhen the frequency is less than 5.5, the rock burst tendency is medium or low; when W isEAbove 5.5, there is a tendency for severe rock burst.
Further, the cylindrical test piece in the step S1 is a standard test piece with a diameter of 50mm and a height of 100mm, the test piece should ensure that the error of the non-parallelism of the two end faces is less than 0.05mm, the error of the diameter along the height of the test piece is less than 0.3mm, meanwhile, the end face should be perpendicular to the axis of the test piece, and the deviation is less than 0.25 °.
Further, in the step S2, a uniaxial compression test is performed on the cylindrical sample, the cylindrical rock-shaped sample is placed on a rigid electrohydraulic servo material control testing machine, and the cylindrical rock-shaped sample is loaded to be damaged at a rate of 0.001mm/S, so as to obtain a stress-strain curve and uniaxial compressive strength σ of the rock samplec。
Further, in the step S3, the cylindrical test piece is subjected to a uniaxial cyclic loading test, and the test piece is vertically loaded to a peak load at a rate of 0.001mm/S by a testing machine, and the peak load of each cycle is set to σcAnd then unloaded to 2kN at the same rate for a total of 3 cycles.
Further, in the step S4, the stress corresponding to the inflection point position is the original stress, where the axial strain difference-stress curve is drawn by subtracting the strain amount values corresponding to the same stresses in the second and third cyclic loading stages.
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 pointTThe 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 not memorized is reached in the indoor uniaxial compression test, the rock does not generate new cracks, so that energy is not accumulated. An axial strain-stress curve is drawn by carrying out a uniaxial cyclic loading test, the original stress of the rock sample is measured, the difference value of the peak stress and the original stress is calculated, namely the stress intensity actually required by the energy accumulated by the rock is obtained, and the stress intensity difference is defined as the stress intensity difference sigmap(ii) a Defining the point on the stress-strain curve corresponding to the original stress as the 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 the original strain energy Ea, and calculating the total input energy E at the peak stress pointTThe difference value of the original strain energy Ea is the energy actually accumulated in the rock in the uniaxial compression processIt is defined as residual strain energy Es, and then the stress energy ratio W is calculatedEThe method can be used as a basis for judging the rock burst tendency of the rock.
The invention has the beneficial effects that key factors causing rock burst are comprehensively considered: stress and energy, and provides a rock burst tendency judgment method based on stress-energy ratio indexes, and rock burst risk level prejudgment is carried out on rocks before construction, so that 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 rockpA 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 marblec=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 σ)c) Then unloaded to 2kN at a rate of 0.001mm/s, and cycled 3 times. Subtracting strain values corresponding to the same stress in the second cycle and the third cycle loading stage 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 marbleT=15.45KJ/m3；
4. Calculating the stress intensity difference sigma of the samplePAnd residual strain energy Es, wherein the stress intensity difference σPIs the difference between the peak stress and the original stress, σP=66.13 MPa; residual strain energy Es is the difference between the total input energy and the original strain energy, Es =14.79KJ/m 3.
5. According to the formula WE=σpCalculated stress-energy ratio W of/EsEThe 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 the average value is taken as the 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 tableEThe 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 samplesEThe calculated results are respectively 3.91, 3.74 and 3.98, and the average value is 3.88, so the rock burst tendency judgment knot of the white marbleIf the rock burst tendency is not existed, the specific calculation result is shown in the following table:
EXAMPLE III
In this example, the stress energy ratio W of two long-length quartz porphyrite is used as the stress energy ratio W of three samplesEThe 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 cylindrical samples;
s2: loading one sample to failure in uniaxial compression test to obtain the stress-strain curve and uniaxial compressive strength sigma of the rock samplec;
S3: the other sample was subjected to a uniaxial cyclic loading test by loading the sample axially through a press at a rate to a peak load set at 0.5 σcUnloading 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 the 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 curveT；
S6: defining the difference between the total input energy and the original strain energy as residual strain energy Es = ET-Ea; the difference between the stress at the peak point and the original stress is the stress intensity difference sigmap；
S7: according to the residual strain energy Es and the stress intensity difference sigmapCalculating the stress energy ratio WE，WE=σp/Es；
S8: according to stress energy ratio WEJudging the rock burst tendency grade when W isEWhen the number is less than 4, the rock burst tendency is avoided; when 4 < WEWhen the frequency is less than 5.5, the rock burst tendency is medium or low; when W isEAbove 5.5, there is a tendency for severe rock burst.
2. The method for discriminating the rock burst tendency grade based on the stress energy ratio as claimed in claim 1, wherein: the cylindrical test piece in the step S1 is a standard test piece with the diameter of 50mm and the height of 100mm, the error of the parallelism of the two end faces of the test piece is less than 0.05mm, the error of the diameter along the height of the test piece is less than 0.3mm, and the deviation of the verticality of the end face is less than 0.25 degrees.
3. The method for discriminating the rock burst tendency grade based on the stress energy ratio as claimed in claim 1, wherein: in the step S2, a uniaxial compression test is carried out on the cylindrical sample, the cylindrical rock 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 the stress-strain curve and the uniaxial compressive strength sigma of the rock sample are obtainedc。
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| CN112991337A (en) * | 2021-04-27 | 2021-06-18 | 中国矿业大学(北京) | Method for correcting rock burst fragment kinetic energy test error |
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