CN105547994A - Method for testing frictional coefficient of rocks - Google Patents
Method for testing frictional coefficient of rocks Download PDFInfo
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- CN105547994A CN105547994A CN201511023377.XA CN201511023377A CN105547994A CN 105547994 A CN105547994 A CN 105547994A CN 201511023377 A CN201511023377 A CN 201511023377A CN 105547994 A CN105547994 A CN 105547994A
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- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N19/00—Investigating materials by mechanical methods
- G01N19/02—Measuring coefficient of friction between materials
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Abstract
The invention provides a method for testing the frictional coefficient of rocks. The method comprises the following steps: I. manufacturing a cylindrical rock test piece of which the ratio of height to diameter is more than 2:1; II. putting the rock test piece into a vaccumized saturation device and making the rock test piece be saturated with a saturation liquid; III. mounting an axial deformation sensor and a radial deformation sensor on the rock test piece and putting the rock test piece into a triaxial chamber of a triaxial rock testing machine; IV: carrying out triaxial test to the rock test piece by the triaxial rock testing machine; V: switching off the triaxial rock testing machine, taking out the fractured rock test piece and measuring the included angles of the fracture surface and the end surface of the test piece; and VI: calculating the frictional coefficient of the rock according to the equation. The method can simulate the underground conditions to measure the frictional coefficient of the rock under a stratigraphic condition.
Description
Technical field
The present invention relates to rock mechanics field, particularly, relate to a kind of method of testing of rock frictional test coefficient.
Background technology
For two geologic bodies be connected (object), friction effect is very important research topic in rock mechanics.From small scale, fracture plane or joint plane slide and produce friction, and fracture plane can be new generation, also can be present in stratum.From large scale, the slip of tomography also can produce friction.
After stratum natural fracture slides, natural fracture becomes permeable effective fracture.The friction factor of rock is higher, and the slip of rock is more difficult.Therefore, rock frictional test coefficient test fracture efficiency analysis is very important.
As shown in figures ia-d, conventional at present rock frictional test coefficient determination method is divided into following four kinds:
Figure 1A is the schematic diagram utilizing staight scissors method to measure friction factor, and apply a normal stress N and shear stress T, device therefor is rock direct shear apparatus.Under the effect of shear stress T, rock slides, and record displacement and shear stress curve, for asking for friction factor.
Figure 1B utilizes double shear method to measure the schematic diagram of friction factor, the method and staight scissors method similar, just many normal stress N and samples.Double shear method shortcoming is that friction area can change in shear history.
Fig. 1 C is the schematic diagram utilizing torsional technique to measure friction factor, and the advantage of the method is no matter displacement is much, and contact area is constant.
Fig. 1 D is the schematic diagram that precracking three-axis friction coefficient is measured, and the method is cut by rock core at a certain angle, an artificial manufacture slipping plane.Experiment can be measured under high pressure, high temperature and pore pressure condition, and measurement data presses close to stratum reality, is the most frequently used method of deep layer friction coefficient measurement.Three-axis friction coefficient testing procedure comprises: cut along with diametral plane with an angle by column rock core; By rock core by cutting plane to good, using heat-shrink tube pyrocondensation, being placed in triaxial chamber (triaxialcell), load confined pressure and axial stress, then with the deformation quantity of rock core for transverse axis, with the stress applied for the longitudinal axis, draw stress-strain curve.
Visible, existing conventional rock frictional test coefficient measuring method all must to the artificial prefabricated rubbing surface of rock (namely making rock frictional test face by artificial) in advance.But the rubbing surface in artificial prefabricated rubbing surface and natural formation crack there are differences in roughness and smoothness, measurement result will be caused and actually have very large gap.
Summary of the invention
The fundamental purpose of the embodiment of the present invention is the new method of testing providing a kind of rock frictional test coefficient, with to solve in prior art rock frictional test coefficient measure in Problems existing, crack rubbing surface to be formed under simulation stratum condition, instead of artificial prefabricated.
To achieve these goals, the embodiment of the present invention provides a kind of method of testing of rock frictional test coefficient, comprising: step 1, prepares columniform rock sample, and wherein, height and the diameter ratio of described rock sample are greater than 2:1; Step 2, is placed on described rock sample and vacuumizes in saturation device, utilize saturated liquid to carry out saturated; Step 3, on described rock sample, installation shaft is to deformation-sensor and radial deformation sensor, and described rock sample is put into the triaxial chamber of rock triaxial test machine; Described axial deformation sensor is for detecting described rock sample deformation quantity in the axial direction, and described radial deformation sensor is for detecting described rock sample deformation quantity diametrically; Step 4, utilizes described rock triaxial test machine to carry out triaxial test to described rock sample, comprising: utilize confined pressure loader to load confined pressure with simulated ground stress to described rock sample; Hole is utilized to press loader to apply pressure to simulate pore pressure to described rock sample; Axial loader is utilized to load axial stress to described rock sample, preset rate of deformation generation deformation to make described rock sample with one and occur crack, when judging that the variable quantity of described axial stress is tending towards 0, the value of now described axial stress is defined as residual strength; Step 5, closes described rock triaxial test machine, takes out the described rock sample of destroyed, measures the angle of its fracture plane and its end face; Step 6, according to following formulae discovery rock frictional test coefficient:
In formula, σ 1 is residual strength;
σ 2 is confined pressure;
P
0for pore pressure;
σ is the normal stress on fracture plane;
τ is the shear stress on fracture plane;
β is the angle of fracture plane and end face;
μ is rock frictional test coefficient.
In an embodiment, the flatness of the end face of described rock sample is less than 0.001mm, and the flatness of side is less than 0.3mm.
In an embodiment, described rock sample is put into the triaxial chamber of rock triaxial test machine, comprising: described rock sample is placed in the weighted platform that top is sphere, and the axis of described weighted platform is overlapped with the axis of described rock sample.
In an embodiment, described saturated liquid is local water.
In an embodiment, described saturated liquid is the normal saline solution according to strata condition configuration.
The present invention can simulate formation condition, record rock friction factor under formation conditions, can sliding by more real simulated formation in not prefabricated crack, and can proceed after conventional rock triaxial compression test completes, more rock mechanics parameters can be recorded, more save core sample.
Accompanying drawing explanation
In order to be illustrated more clearly in the embodiment of the present invention or technical scheme of the prior art, below the accompanying drawing used required in describing embodiment is briefly described, apparently, accompanying drawing in the following describes is only some embodiments of the present invention, for those of ordinary skill in the art, under the prerequisite not paying creative work, other accompanying drawing can also be obtained according to these accompanying drawings.
Figure 1A is that staight scissors method measures friction factor schematic diagram;
Figure 1B is that double shear method measures friction factor schematic diagram;
Fig. 1 C is that torsional technique measures friction factor schematic diagram;
Fig. 1 D is precracking three-axis friction coefficient measuring method schematic diagram;
Fig. 2 is the particular flow sheet of exemplifying method;
Fig. 3 is sample schematic diagram after experiment;
Fig. 4 is the schematic diagram of rock triaxial test machine;
Fig. 5 is the stress-strain curve schematic diagram in triaxial test;
Fig. 6 is the stressed schematic diagram installing radial deformation sensor, axial deformation sensor and rock sample on rock sample.
Embodiment
Below in conjunction with the accompanying drawing in the embodiment of the present invention, be clearly and completely described the technical scheme in the embodiment of the present invention, obviously, described embodiment is only the present invention's part embodiment, instead of whole embodiments.Based on the embodiment in the present invention, those of ordinary skill in the art, not making the every other embodiment obtained under creative work prerequisite, belong to the scope of protection of the invention.
illustrative methods
Illustrative methods of the present invention provides a kind of method of testing of rock frictional test coefficient, and as shown in Figure 2, the method comprises:
Step S11, prepares columniform rock sample, and wherein, height and the diameter ratio of rock sample are greater than 2:1.
Alternatively, the flatness of the end face of rock sample is less than 0.001mm, and the flatness of side is less than 0.3mm.
Step S12, is placed on rock sample and vacuumizes in saturation device, utilize saturated liquid to carry out saturated.
Alternatively, saturated liquid is local water or the normal saline solution according to strata condition configuration.
Step S13, on rock sample, installation shaft is to deformation-sensor and radial deformation sensor, and rock sample is put into the triaxial chamber of rock triaxial test machine; Axial deformation sensor is for detecting rock sample deformation quantity in the axial direction, and radial deformation sensor is for detecting rock sample deformation quantity diametrically.
Alternatively, rock sample is placed in the weighted platform that top is sphere, and the axis of weighted platform is overlapped with the axis of rock sample.
Step S14, utilizes rock triaxial test machine to carry out triaxial test to rock sample, comprising: utilize confined pressure loader to load confined pressure with simulated ground stress to rock sample; Hole is utilized to press loader to apply pressure to simulate pore pressure to rock sample; Utilize axial loader to load axial stress to rock sample, to make rock sample preset rate of deformation generation deformation occur crack with one, when judging that the variable quantity of axial stress is tending towards 0, the value of now axial stress is defined as residual strength.
During concrete enforcement, axial loader is the size controlling the axial stress applied according to rock sample deformation situation in the axial direction (keeping presetting rate of deformation generation deformation with), default rate of deformation wherein generally elect as per second with 0.001% diameter generation deformation (namely deformation quantity per second is for 0.001%).
Step S15, closes rock triaxial test machine, takes out the rock sample of destroyed, measures the angle of its fracture plane and its end face.
Step S16, analyzes test figure, according to following formulae discovery rock frictional test coefficient:
In formula, σ 1 is residual strength, and unit is MPa;
σ 2 is confined pressure, and unit is MPa;
P
0for pore pressure, unit is MPa;
σ is the normal stress on fracture plane, and unit is MPa;
τ is the shear stress on fracture plane, and unit is MPa;
β is the angle of fracture plane and end face;
μ is rock frictional test coefficient.
Exemplifying method can simulate formation condition, record rock friction factor under formation conditions, can slide by more real simulated formation in not prefabricated crack, and can proceed after conventional rock triaxial compression test completes, the more rock mechanics parameters that can survey, more save core sample.
embodiment one
The present embodiment is a specific embodiment of exemplifying method, and the present embodiment can complete in rock triaxial test machine, its operating process and ordinary triaxial test basically identical.
As shown in Figure 4, rock triaxial test machine comprises triaxial chamber, hole pressure loader, confined pressure loader, axial loader, loading frame.Wherein, triaxial chamber comprises sealing shroud and weighted platform (not showing in Fig. 4) further; Hole pressure loader is used for applying pressure to simulate pore pressure to rock sample; Confined pressure loader is used for loading confined pressure with simulated ground stress to rock sample; Axial loader is used for loading axial stress to rock sample, and the effect of axial stress makes rock sample preset rate of deformation generation deformation with one and occur crack; For the present embodiment, the rigidity of loading frame is greater than 5MN/mm or 10MN/mm rigidity the best.
The detailed process of this embodiment comprises the steps:
Step 1, prepares columniform rock sample, and the diameter of test specimen should be at least 20 times of the maximum gauge of rock particles; Wherein, the height of rock sample and diameter ratio should be greater than 2:1, and during to guarantee that crack appears in rock sample, the angle in crack is unaffected, farthest can occur the situation in crack under field conditions (factors) by simulation rock.The flatness of the end face of rock sample is less than 0.001mm, and the flatness of side is less than 0.3mm.
Step 2, is placed on rock sample and vacuumizes saturated 24-48 hour in saturation device, and wherein saturated liquid is local water or the normal saline solution according to strata condition configuration; Then check rock sample, determine that rock sample completes saturated.
Step 3, as shown in Figure 6, on rock sample, installation shaft is to deformation-sensor and radial deformation sensor, and rock sample being placed on top is in the weighted platform of sphere, and puts into the triaxial chamber of three-axis tester, utilizes sealing shroud to seal.
Wherein, axial deformation sensor is for detecting rock sample deformation quantity in the axial direction, radial deformation sensor is for detecting rock sample deformation quantity diametrically, the accuracy of instrument of axial deformation sensor and radial deformation sensor should reach 0.002mm in the measuring range of 0.02mm, within the scope of 0.25mm, reach 0.005mm.
Weighted platform can play the effect of buffering between axial loader and rock sample, why use weighted platform that top is sphere (in this case, axial loader has the concave surface matched with the sphere of weighted platform), the end face that the axial stress axial loader being applied by the weighted platform of sphere balancedly can be applied to rock sample on the one hand, guarantee the end face uniform force of rock sample, simulation rock test specimen stressing conditions in the earth formation better, the harmful effect that the out-of-flatness in order to reduce rock sample end face causes axial loader on the other hand, axial loader is protected not to be damaged.
The spherical diameter of weighted platform should be identical with the diameter of rock sample or bigger, and the centre of sphere of weighted platform should be on a vertical line with the center of circle of rock sample end face and (guarantees rock sample and weighted platform centering).During experiment, contact zones can be used rock sample and weighted platform to be intertwined to make the two centering, and to guarantee that rock sample can not move or rotate.
Step 4, utilizes rock triaxial test machine to carry out triaxial test to rock sample, comprising: utilize confined pressure loader to load confined pressure with simulated ground stress to rock sample; Hole is utilized to press loader to apply pressure to simulate pore pressure to rock sample; Axial loader is utilized to load axial stress to rock sample, be the rate of deformation generation deformation of 0.001% to make rock sample with deformation quantity per second and occur crack, when judging that the variable quantity of axial stress is tending towards 0, the value of now axial stress is defined as residual strength.
When judging whether the variable quantity of axial stress is tending towards 0, the stress-strain curve also drawn by computer real-time acquisition judges.Fig. 5 is the stress-strain curve in experimentation.As shown in Figure 5, transverse axis is deformation quantity axially, the longitudinal axis is the axial stress applied, this curve record whole process of the rock failure mechanism of rock, maximum axial stress is the compressive strength of rock, and the axial stress stress that finally section of tending to be steady (namely variable quantity is tending towards 0) is corresponding is residual strength.
Step 5, closes rock triaxial test machine, takes out the rock sample of destroyed, measures the angle β of its fracture plane and its end face, as shown in Figure 3.
Step 6, analyzes test figure, according to following formulae discovery rock frictional test coefficient:
In formula, σ 1 is residual strength, and unit is MPa;
σ 2 is confined pressure, and unit is MPa;
P
0for pore pressure, unit is MPa;
σ is the normal stress on fracture plane, and unit is MPa;
τ is the shear stress on fracture plane, and unit is MPa;
μ is rock frictional test coefficient.
In above-mentioned formula, the confined pressure σ 2 of rock sample and pore pressure p
0simulate terrestrial stress under the formation condition of rock sample place and pore pressure respectively, both just can pre-determine when preparing rock sample, the angle β of the residual strength σ 1 obtained by triaxial test again and rock sample fracture plane and its end face, is substituted in above-mentioned formula and just can calculate rock frictional test coefficient μ.
Table 1 is friction coefficient measurement result, and part of test results is as shown in table 1.
Table 1 friction coefficient measurement result
In sum, the present invention can simulate formation condition, record rock friction factor under formation conditions, can slide by more real simulated formation in not prefabricated crack, and can proceed after conventional rock triaxial compression test completes, more rock mechanics parameters can be recorded, more save core sample.
Above-described specific embodiment; object of the present invention, technical scheme and beneficial effect are further described; be understood that; the foregoing is only specific embodiments of the invention; the protection domain be not intended to limit the present invention; within the spirit and principles in the present invention all, any amendment made, equivalent replacement, improvement etc., all should be included within protection scope of the present invention.
Claims (5)
1. a method of testing for rock frictional test coefficient, is characterized in that, comprising:
Step 1, prepares columniform rock sample, and wherein, height and the diameter ratio of described rock sample are greater than 2:1;
Step 2, is placed on described rock sample and vacuumizes in saturation device, utilize saturated liquid to carry out saturated;
Step 3, on described rock sample, installation shaft is to deformation-sensor and radial deformation sensor, and described rock sample is put into the triaxial chamber of rock triaxial test machine; Described axial deformation sensor is for detecting described rock sample deformation quantity in the axial direction, and described radial deformation sensor is for detecting described rock sample deformation quantity diametrically;
Step 4, utilizes described rock triaxial test machine to carry out triaxial test to described rock sample, comprising: utilize confined pressure loader to load confined pressure with simulated ground stress to described rock sample; Hole is utilized to press loader to apply pressure to simulate pore pressure to described rock sample; Axial loader is utilized to load axial stress to described rock sample, preset rate of deformation generation deformation to make described rock sample with one and occur crack, when judging that the variable quantity of described axial stress is tending towards 0, the value of now described axial stress is defined as residual strength;
Step 5, closes described rock triaxial test machine, takes out the described rock sample of destroyed, measures the angle of its fracture plane and its end face;
Step 6, according to following formulae discovery rock frictional test coefficient:
In formula, σ 1 is residual strength;
σ 2 is confined pressure;
P
0for pore pressure;
σ is the normal stress on fracture plane;
τ is the shear stress on fracture plane;
β is the angle of fracture plane and end face;
μ is rock frictional test coefficient.
2. the method for testing of rock frictional test coefficient as claimed in claim 1, it is characterized in that, the flatness of the end face of described rock sample is less than 0.001mm, and the flatness of side is less than 0.3mm.
3. the method for testing of rock frictional test coefficient as claimed in claim 1, it is characterized in that, described rock sample is put into the triaxial chamber of rock triaxial test machine, comprise: described rock sample is placed in the weighted platform that top is sphere, and the axis of described weighted platform is overlapped with the axis of described rock sample.
4. the method for testing of rock frictional test coefficient as claimed in claim 1, it is characterized in that, described saturated liquid is local water.
5. the method for testing of rock frictional test coefficient as claimed in claim 1, is characterized in that, described saturated liquid is the normal saline solution according to strata condition configuration.
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Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN107218035A (en) * | 2017-06-13 | 2017-09-29 | 北京大学 | A kind of experimental provision of automatic change crack wall mill resistance and method of work and application |
| CN114778435A (en) * | 2022-04-06 | 2022-07-22 | 重庆交通大学 | Experimental device for be used for simulating gliding of rock block |
| CN114894708A (en) * | 2022-03-18 | 2022-08-12 | 绍兴文理学院 | Method for calibrating friction coefficient of core sample containing through single crack |
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| JPH09243550A (en) * | 1996-03-05 | 1997-09-19 | Kawasaki Heavy Ind Ltd | Method and apparatus for measuring coefficient of friction of rotary blade and disc |
| CN104990866A (en) * | 2015-07-23 | 2015-10-21 | 三峡大学 | Method utilizing nail shooting to measure rock cohesion C and internal friction angle (Phi) |
| CN105019877A (en) * | 2015-06-24 | 2015-11-04 | 西南石油大学 | Calculating method for size of fracturing and broken region of horizontal well for shale |
| CN105157537A (en) * | 2015-07-29 | 2015-12-16 | 中国神华能源股份有限公司 | Method and device for measuring frictional angles of rock sample |
-
2015
- 2015-12-31 CN CN201511023377.XA patent/CN105547994B/en active Active
Patent Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH09243550A (en) * | 1996-03-05 | 1997-09-19 | Kawasaki Heavy Ind Ltd | Method and apparatus for measuring coefficient of friction of rotary blade and disc |
| CN105019877A (en) * | 2015-06-24 | 2015-11-04 | 西南石油大学 | Calculating method for size of fracturing and broken region of horizontal well for shale |
| CN104990866A (en) * | 2015-07-23 | 2015-10-21 | 三峡大学 | Method utilizing nail shooting to measure rock cohesion C and internal friction angle (Phi) |
| CN105157537A (en) * | 2015-07-29 | 2015-12-16 | 中国神华能源股份有限公司 | Method and device for measuring frictional angles of rock sample |
Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN107218035A (en) * | 2017-06-13 | 2017-09-29 | 北京大学 | A kind of experimental provision of automatic change crack wall mill resistance and method of work and application |
| CN114894708A (en) * | 2022-03-18 | 2022-08-12 | 绍兴文理学院 | Method for calibrating friction coefficient of core sample containing through single crack |
| CN114894708B (en) * | 2022-03-18 | 2024-05-14 | 绍兴文理学院 | Method for calibrating friction coefficient of core sample containing penetrating single fracture |
| CN114778435A (en) * | 2022-04-06 | 2022-07-22 | 重庆交通大学 | Experimental device for be used for simulating gliding of rock block |
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