CN112129448A - Method for measuring ground stress by using elastic recovery deformation of core - Google Patents
Method for measuring ground stress by using elastic recovery deformation of core Download PDFInfo
- Publication number
- CN112129448A CN112129448A CN202010509017.5A CN202010509017A CN112129448A CN 112129448 A CN112129448 A CN 112129448A CN 202010509017 A CN202010509017 A CN 202010509017A CN 112129448 A CN112129448 A CN 112129448A
- Authority
- CN
- China
- Prior art keywords
- strain
- core
- stress
- hysteresis
- elastic
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Pending
Links
Images
Classifications
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01L—MEASURING FORCE, STRESS, TORQUE, WORK, MECHANICAL POWER, MECHANICAL EFFICIENCY, OR FLUID PRESSURE
- G01L5/00—Apparatus for, or methods of, measuring force, work, mechanical power, or torque, specially adapted for specific purposes
- G01L5/16—Apparatus for, or methods of, measuring force, work, mechanical power, or torque, specially adapted for specific purposes for measuring several components of force
Landscapes
- Physics & Mathematics (AREA)
- General Physics & Mathematics (AREA)
- Force Measurement Appropriate To Specific Purposes (AREA)
- Investigating Strength Of Materials By Application Of Mechanical Stress (AREA)
Abstract
A method for measuring ground stress by utilizing elastic recovery deformation of a core is used for effectively acquiring reliable ground stress data, and has stronger adaptability and higher efficiency. The method comprises the following steps: drilling a rock core; pasting a strain gauge; performing hysteresis elastic deformation strain test; temperature calibration; determining the hysteresis elasticity and flexibility; and (6) analyzing and processing data. Compared with the traditional method, the method has stronger adaptability and economy, and particularly, when the stress relief method, the hydraulic fracturing method and the like are difficult to implement under the complex geological conditions of large-depth drilling holes and broken stratums, the method still has the possibility of obtaining more reliable ground stress data and has stronger adaptability.
Description
Technical Field
The invention relates to geological exploration, in particular to a method for measuring ground stress by utilizing elastic recovery deformation of a rock core.
Background
The ground stress is the natural stress present in the formation without the engineered disturbance. The method is a fundamental acting force causing deformation and damage of the underground engineering, and is a precondition for determining mechanical properties of engineering rock mass, analyzing stability of surrounding rock, optimizing excavation design of the underground engineering and making decisions scientifically and controlling the whole process of rock excavation. Numerous studies and in situ ground stress measurements have shown that the effects of gravity and tectonic movements are the main causes of ground stress, with tectonic movements in the horizontal direction having the greatest influence on the formation of ground stress. The ground stress state of a certain location is mainly controlled by the last construction movement, but is also related to the historical construction movement. For millions of years, the earth experiences countless large and small tectonic movements, and stress fields of the tectonic movements are overlapped, drawn and transformed for many times and are influenced by other factors, so that the complexity and diversity of the ground stress state are caused. Therefore, the magnitude and direction of the ground stress are difficult to obtain by mathematical calculation or model analysis, and the most effective method for knowing the ground stress state of a region is to perform field ground stress measurement.
The ground stress and the physical and mechanical parameters of the rock mass are the most basic parameters required by underground engineering design and construction. The magnitude and the direction of the ground stress can be obtained only by in-situ test, the two methods which are the most widely adopted at present comprise the ground stress measurement of a hydraulic fracturing method and the ground stress measurement of a stress relieving method have certain limitations, wherein a packer packing test section is required in the hydraulic fracturing method test process, so that the packer is difficult to put down to the test section for ultra-deep holes and broken drill holes, and the hydraulic fracturing method cannot be implemented; the stress relief method needs to punch holes in the test part to install strain gauges, so that the method is mainly used for construction projects.
Disclosure of Invention
The invention aims to solve the technical problem of providing a method for measuring geostress by utilizing the elastic recovery deformation of the core lag so as to effectively obtain reliable geostress data, and the method has stronger adaptability and higher efficiency.
The technical scheme adopted by the invention for solving the technical problems is as follows:
the invention relates to a method for measuring ground stress by utilizing elastic recovery deformation of a rock core, which comprises the following steps:
(1) drilling a rock core;
(2) pasting a strain gauge;
(3) performing hysteresis elastic deformation strain test, namely placing the core at a non-disturbed position, opening acquisition equipment for monitoring, setting the acquisition interval to be 10min, and recording time and temperature data after effective data are pasted for 2 hours to obtain a hysteresis elastic deformation measurement curve;
(4) temperature calibration, namely stopping measurement when the estimated hysteretic elastic recovery strain reaches more than 95%, performing a temperature calibration experiment on the core, putting the core into a constant temperature box, performing the temperature calibration experiment according to the temperature change characteristic in monitoring to obtain the strain heat output magnitude at the temperature of 10 degrees, 20 degrees and 30 degrees, and eliminating the strain heat output magnitude in measurement;
(5) determining the elastic hysteresis flexibility, namely placing the in-situ rock core on an elastic hysteresis loading test instrument, estimating the stress level at a drilling test point, loading, and unloading after long-term strain is stable to obtain the elastic hysteresis strain recovery flexibility under the stress level;
(6) and (3) analyzing and processing data, calculating the hysteresis elasticity data, meeting the requirements of 3 times of parallel experiments with a measuring point to obtain the magnitude of the main stress, and preferentially selecting a directional core, or adopting post-drilling image shooting positioning, or carrying out main stress direction judgment according to the calculation result of the ground stress and the combination of the structural characteristics.
In the step (2), the core with the length larger than 150mm taken out from the drilled hole is cleaned, the surface of the core is polished and the strain rosettes are adhered, three groups of strain sheets are adhered, the circumference is equally divided into three groups along the cross section of the measured core, and the included angle between every two adjacent strain sheets is 120 degrees.
In the step (5), the hysteresis elastic strain recovery flexibility is calculated according to the following formula:
wherein Jas (t) is shear hysteresis elastic strain recovery compliance, Jav (t) is volume hysteresis elastic strain recovery compliance, σ1For axial loading, σ3In order to be a transverse load,1ain order to be under axial strain,3ais the transverse strain.
In the step (6), the principal stress σi(i ═ 1,2,3) was calculated as follows:
σi＝ei(t)/Jas(t)+em(t)/Jav(t)+p0
in the formula ei(t) (i ═ 1,2,3) shows anelastic bias strain, em(t) is anelastic flatAverage principal strain, Jas (t) shear hysteresis elastic strain recovery compliance, Jav (t) volume hysteresis elastic strain recovery compliance, p0Is the pore pressure;
vertical principal stress sigmavCalculated as follows:
in the formula Ip,mp,npIs the cosine of the angle between the vertical main stress and the axis of the three main strains, k is the compliance ratio, Jas (t)/Jav (t) k.
The method has the advantages that the defects of the existing method can be effectively overcome, the hysteresis elastic recovery deformation of the rock core which is just lifted is measured by sticking the strain gauge to the rock core, and the size of the three-dimensional ground stress can be calculated by calibrating the indoor temperature and measuring the hysteresis elastic strain recovery flexibility; compared with the traditional method, the method has stronger adaptability and economy; particularly, under complex geological conditions of large-depth drilling and broken stratums, when a stress relief method, a hydraulic fracturing method and the like are difficult to implement, reliable ground stress data can be obtained by the method, and the method is high in adaptability; the method has the advantages of low cost, high efficiency, no limitation of drilling depth and temperature, capability of measuring three-dimensional stress and the like, and can be used for measuring the ground stress by using the method as long as the directional core can be obtained.
Drawings
The specification includes the following figures:
FIG. 1 is a graph of strain versus time during rock loading and unloading;
FIG. 2 is a schematic view of a 2-unit rheological model;
FIG. 3 is a schematic view of a field layout;
FIG. 4 is a schematic diagram of the number of channels of a strain gage;
FIG. 5 is a graph of raw data for point X;
FIG. 6 is a temperature channel temperature calibration scatter plot;
FIG. 7 is a temperature channel coefficient fit plot;
FIG. 8 is an X core anelastic strain curve;
FIG. 9 shows the entire process of uniaxial loading at 25 MPa.
Detailed Description
The invention is further illustrated with reference to the following figures and examples.
Referring to fig. 1, a core is deformed under the action of three-dimensional stress in an original condition, when the stress is released, a part of deformation of the core is recovered instantly and belongs to elastic deformation, and the other part of deformation does not reach an elastic deformation value immediately but has a relative lagging process in time, and the deformation is called hysteresis elastic recovery deformation.
The elastic deformation of the instantaneous recovery is difficult to capture in the measurement of the ground stress, so that the measurement of the ground stress can be developed by utilizing the elastic recovery deformation. In studying the rheology of rock, the core is used as an isotropic, linear viscoelastic material, and its deformation includes shear deformation and volume deformation, and usually adopts an anelastic volume rheological model as shown in fig. 2. In the figure, E1 represents the elasticity of the material, and η 1 represents the viscosity of the material.
Set at a generally three-dimensional stress and void pressure P0The rock under action is elastic, and the normal strain in any direction l, m, n can be written as:
where l, m, n are direction cosines in any direction, corresponding to axis X, Y, Z: e is the elastic modulus: upsilon is a transverse deformation coefficient; k is the bulk modulus; ksIs the parent rock bulk modulus; alpha is alphaTIs the linear expansion coefficient; Δ T is the temperature increase.
For conventional triaxial compression experiments (σ)2＝σ3Anelastic strain recovery flexibilities jas (t) and jav (t) can be determined by the formula (2):
for isotropic viscoelastic materials, the amount of hysteretic elastic recovery strain in any direction is determined by the gradual release of in-situ and pore water stressesa(t) is:
when the control temperature is constant in the measurement of the hysteresis elastic strain recovery method, the thermal expansion strain due to the change in temperature in the above formula (3) can be ignored. The above formula (3) gives the basis of measuring the geostress by the hysteresis elastic strain recovery method, and indicates that the hysteresis elastic strain recovery depends on independent 6 normal components in the tensorial geostress, the pore water pressure and the hysteresis elastic strain recovery flexibility of two deformation modes. Thus, if elastic strain recovery flexibility (Jas (t), Jav (t)) and pore water pressure p are retained0It is known that 6 normal stress components (i.e. the three-dimensional earth stress tensor) can be obtained by measuring at least 6 independent directions of anelastic strain.
For isotropic viscoelastic materials, the 3 principal stress directions coincide with the principal axes of the 3 extensional hysteretic strains, so the three-dimensional principal stress direction can be determined by measurement of the extensional hysteretic strains, i.e. by measuring the normal strain of at least 6 independent directions.
Main stress deflection:
si＝σi-σm(i＝1,2,3) (4)
in the formula, siIs the principal stress offset s1、s2、s3；σiIs 3 principal stresses sigma1、σ2、σ3；σmTo average principal stress, σm＝(σ1+σ2+σ3)/3
Main strain offset:
ei＝i-em(i＝1,2,3) (5)
in the formula, eiIs a principal strain offset e1、e2、e3；iIs three main strains1、2、3；emIn order to average out the main strain,
em＝(1+2+3)/3 (6)
it is theorized that the ratio of principal stress offsets may be determined from the principal stress offsets. If the rock is a mechano-thermal isotropic body, then the elastic strain bias e is retardedijaWhen replacing anelastic normal strain in 6 independent directions, there are:
eija(t)＝(1/3)[(3l2-1)σx+(3m2-1)σy+(3n2-1)·σz+6lmτxy+6mnτyz+6nlτzx]Jas(t) (7)
these 6 anelastic strain offsets determine the ratio of principal stress offset to principal stress azimuth.
The elastic strain recovery flexibility changes with the change of the average stress, the dependence on the average stress is mainly influenced by short-term deformation, and a certain time is needed for the rock core extracted from the deep hole to reach a laboratory, so in the formula (7), the elastic strain recovery flexibility with the change of the average stress can be disregarded.
In addition, the anelastic mean normal strain eaCan be written as:
ea(t)＝(σm-P0)Jav(t)+αTΔT (8)
measurement of mesopore pressure P in anelastic strain recovery0May be measured by well logging. Therefore, when the absolute value of the crustal stress is determined, the volume recovery flexibility of the core elastic strain can be measured by a laboratory, and the absolute value of the three-dimensional crustal stress can be determined by combining the ratio of the 3 main stress deflection determined in the step (7) through an iteration method.
After the anelastic deformation strain test is finished, the magnitude of the in-situ stress value needs to be estimated by using an aging calculation theory, and the specific calculation steps are as follows:
after a core (the length is more than 150mm) taken out from a drill hole is cleaned, the surface of the core is polished and stuck with strain flowers according to the requirements of an aging strain test scheme, three groups of strain sheets are stuck together, the circumference is equally divided into three groups along the cross section of the measured core, namely the included angle of two adjacent strain sheets is 120 degrees, and the coordinate system of the core is selected and the corresponding position relation of any cross section strain sheet along the axis direction of the core is shown in figure 3.
Each strain rosette comprises four strain gauges, during measurement, the strain rosettes are connected into channels 1-4 of the acquisition box according to the diagram shown in figure 4 in a first group, connected into channels 5-8 of the acquisition box in a second group, and connected into channels 9-12 of the acquisition box in a third group.
If the core coordinate system is as shown in O-XYZ in fig. 3, the Z-axis is the same as the direction in which the upper part of the core points during coring (the upper part of fig. 3 points outward from the vertical plane of the paper). Strain value and strain tensor measured by strain rosette adhered on the surface of the rock corex,y,z,xy,yz,zxCan be written as equation (9):
A＝b (9)
in the formula: 2 ═ 2x,y,z,xy,yz,zx]TThe strain tensor of the rock is shown in the above-mentioned coordinate system of fig. 3, where b is [ b ]1,b2,b3,b4,b5,b6,b7,b8,b9,b10,b11,b12]TB, strain value measured for strain gauge adhered to surface of rock core in the measurement1,b2,b3,b4,b5,b6,b7,b8,b9,b10,b11,b12Respectively corresponding to the strain acquisition values of 1-12 channels of the acquisition box. A is a coefficient matrix, and the expansion of A is as follows:
li,mi,niis the cosine of the direction of the strain gauge axis relative to the axis of the coordinate system O-XYZ (the coordinate system shown in FIG. 3), and can be established by the core coordinate system shown in FIG. 3 and the strain gauge structure and pasting method shown in FIG. 4The cosine of the direction of each strain channel is shown in the following table 1:
TABLE 1 cosine values of coordinate system directions of cores corresponding to strain gauge channels
Note: the corresponding channel of the strain gauge in the table represents the channel number of the strain gauge accessing the strain collector, li,mi,niIndicating the cosine of the direction of the axis of the strain channel corresponding to coordinate axis X, Y, Z.
Substituting the data in the table into the expansion of A can obtain the coefficient matrix A as follows:
the unknown number in the strain component equation is equal to n and equal to 6, and the number m of independent equations is equal to 10 (three strain gages in the long axis direction of the core are the same, namely 4 channels, 8 channels and 12 channels are the same, so that 2 channels are repeated), and the most accurate solution can be obtained by solving the overdetermined equation set by using a least square method. The following equation (10) is solved by using the least square method, and the solution process is as follows:
ATA＝ATb (10)
the solution is as follows:
＝(ATA)-1ATb (11)
the strain component can be solved from the resultx,y,z,xy,yz,zx]T。
The magnitude of the principal strain can be found by solving the following system of equations:
solving the linear homogeneous equation set can be carried out by using a determinant coefficient of 0, and the specific solving process is as follows:
the determinant is developed as a one-dimensional cubic equation:
3-(1+2+3)2+(2 3+3 1+1 2)-1 2 3＝0 (12)
in the formula:1+2+3＝x+y+z；
therefore, the magnitude of the main strain can be obtained by solving the cubic equation.
Calculation of principal stress σ from anelastic strainiThe size of (i ═ 1,2,3) can be calculated according to equation (13):
σi＝ei(t)/Jas(t)+em(t)/Jav(t)+p0 (13)
in the formula ei(t) (i ═ 1,2,3) shows anelastic bias strain, em(t) hysteresis elastic mean principal strain, Jas (t) shear hysteresis elastic strain recovery compliance, Jav (t) volume hysteresis elastic strain recovery compliance, p0Is the pore pressure.
Assuming jas (t)/jav (t) k, then the vertical stress can be expressed as equation (14):
in the formula Ip,mp,npThe cosine value of the included angle between the vertical main stress and the axis of the three main strains, and meanwhile, the vertical main stress can be estimated by using the dead weight of the overlying strata according to the formula (15):
σv＝ρgh (15)
therefore, as can be seen from the foregoing, by combining the above equations (12), (13), (14), and (15), the stress solution can be completed.
The meanings of the letters related to the formula in the specification are as follows:
| l,m,n | direction cosine of | σm | Mean principal stress |
| E | Modulus of elasticity | ei | Offset of principal strain |
| υ | Coefficient of transverse deformation | εi | Principal strain |
| K | Bulk modulus | em | Mean principal strain |
| k | Compliance ratio | eija | Bias of anelastic strain |
| αT | Coefficient of linear expansion | ei(t) | Strain of hysteresis elasticity |
| ΔT | Temperature increment | em(t) | Mean principal strain of hysteresis |
| p0 | Pore water pressure | Jas(t) | Shear hysteresis elastic strain recovery compliance |
| si | Principal stress offset | Jav(t) | Volume hysteresis elastic strain recovery compliance |
| σi | Principal stress | σv | Vertical principal stress |
The invention relates to a method for measuring ground stress by utilizing elastic recovery deformation of a rock core, which comprises the following steps:
(1) and (6) drilling a core. And preferentially selecting the directional core, or adopting later-stage drilling and shooting for positioning, or carrying out main stress direction judgment according to the ground stress calculation result and the structural characteristics.
(2) And pasting a strain gauge. According to the rock types, strain gauges matched with heat output are selected, the complete section of the core is selected to be cleaned, wiped and polished, a plurality of groups of strain rosettes are pasted according to different directions, the core is wrapped after pasting, and meanwhile, a section of core at the same position is reserved for orientation and calibration. The length of the rock core taken out of the drill hole is more than 150mm, three groups of strain gauges are generally pasted together, the circumference is equally divided into three groups along the cross section of the rock core to be measured, and the included angles of two adjacent strain gauges are 120 degrees.
(3) Performing hysteresis elastic deformation strain test, namely placing the core at a non-disturbed position, opening acquisition equipment for monitoring, setting the acquisition interval to be 10min, and recording time and temperature data after effective data are pasted for 2 hours to obtain a hysteresis elastic deformation measurement curve;
(4) and (3) temperature calibration, namely stopping measurement when the estimated hysteretic elastic recovery strain reaches more than 95%, performing a temperature calibration experiment on the core, putting the core into a constant temperature box, performing the temperature calibration experiment according to the temperature change characteristic in monitoring to obtain the strain heat output at the temperature of 10 degrees, 20 degrees and 30 degrees, and eliminating the strain heat output during measurement. Firstly, carrying out a temperature calibration experiment, namely putting the rock core into a constant temperature box, carrying out the temperature calibration experiment according to the temperature change characteristics in monitoring to obtain the magnitude of the strain heat output at different temperatures, and eliminating the magnitude of the strain heat output during measurement.
(5) And (3) determining the elastic hysteresis flexibility, namely placing the in-situ rock core on an elastic hysteresis loading test instrument, estimating the stress level at a drilling test point, loading, and unloading after long-term strain is stable to obtain the elastic hysteresis strain recovery flexibility under the stress level.
The hysteresis elastic strain recovery flexibility is calculated according to the following formula:
wherein Jas (t) is shear hysteresis elastic strain recovery compliance, Jav (t) is volume hysteresis elastic strain recovery compliance, σ1For axial loading, σ3In order to be a transverse load,1ain order to be under axial strain,3ais the transverse strain.
(6) And (3) analyzing and processing the data, calculating the hysteresis elasticity data, meeting the requirements of 3 times of parallel experiments with the measuring point to obtain the magnitude of the main stress, and judging the direction of the main stress according to the structural information to obtain the direction of the main stress.
Principal stress sigmai(i ═ 1,2,3) was calculated as follows:
σi＝ei(t)/Jas(t)+em(t)/Jav(t)+p0
in the formula ei(t) (i ═ 1,2,3) shows anelastic bias strain, em(t) hysteresis elastic mean principal strain, Jas (t) shear hysteresis elastic strain recovery compliance, Jav (t) volume hysteresis elastic strain recovery compliance, p0Is the pore pressure;
vertical principal stress sigmavCalculated as follows:
in the formula Ip,mp,npIs the cosine of the angle between the vertical main stress and the axis of the three main strains, k is the compliance ratio, Jas (t)/Jav (t) k.
At the same time, the vertical principal stress σvThe overburden dead weight is used for estimation as follows:
σv＝ρgh
where ρ is overburden density, g is gravitational acceleration, and h is overburden thickness.
Compared with the existing ground stress test method, the method has stronger adaptability and economy. Particularly, under the complex geological conditions of large-depth drilling and broken stratum, when a stress relief method, a water fracturing method and the like are difficult to implement, the method still has the advantages of being possible to obtain reliable ground stress data, stronger in adaptability, low in cost, high in efficiency, free of the limitation of the depth and the temperature of the drilling, capable of carrying out three-dimensional stress measurement and the like, and the ground stress can be measured by using the method as long as the directional core can be obtained.
Example (b):
(1) brief introduction to the measurement engineering
Coring depth: 890.3m-891m (vertical hole)
Coring length: 70 cm
Coring diameter: 47mm
(2) Hysteretic elastic strain data on-site acquisition
The time duration of the acquisition and testing of the timeliness strain field of the core at the X measuring point is about 5-7 days, the timeliness strain acquisition unit can be used for acquiring and storing onsite core timeliness strain data, and each acquisition unit is extracted to analyze and process the timeliness strain data to obtain a timeliness strain-time curve, as shown in figure 5. The change trend of the anelastic strain along with time is basically consistent, after the rock core is lifted from the in-situ state, the initial change of the aging strain is rapid, the later period of the test is basically unchanged, and the aging strain reaches a stable peak value within 3-7 days.
The core was temperature calibrated after transport from the field to the laboratory, and the measurement box calibration results are shown in fig. 6.
Finally, the temperature coefficient of the temperature channel obtained according to the calibration curve is 2754.4/DEG C, and the fitting graph of the index change of the temperature channel generated by the temperature channel along with the temperature change is shown in figure 7.
The coefficients of the channels of the cores of the X measuring points obtained by the temperature calibration test are shown in the following table 2:
table 2 table of temperature calibration results of time-dependent strain acquisition device for core sample at X measuring point
Note: in the table, N represents the number of the acquisition channel of the time-dependent strain collector, T represents the temperature set value (10-30 ℃, three temperature sections are designed totally, the temperature increment of the adjacent temperature sections is 10 ℃) when the temperature is calibrated, and K represents the temperature error strain caused when the temperature of each channel changes by 1 ℃.
The estimated temperature coefficient is used to eliminate the temperature influence and the channel strain with strain drift and the temperature channel temperature coefficient is used to obtain a temperature change diagram as shown in FIG. 8.
(3) Calibration experiment for hysteretic elastic strain recovery flexibility of rock
And (3) performing an anelastic uniaxial dead load test on the X-measuring point core rock to obtain a Poisson's ratio of 0.23, using 25MPa dead load for about 96 hours during indoor experimental loading of the aging deformation parameters of the X-measuring point core sample, immediately unloading after the experimental loading process is finished, and acquiring aging strain recovery data for about 144 hours after unloading.
The whole process of uniaxial loading at 25MPa is shown in FIG. 9.
The results of the hysteresis flexibility calculations are shown in table 3 below:
TABLE 3 integrated table of hysteresis elasticity and flexibility calculation results of X measuring points
(4) Computing strain selection and stress value estimation
Data are selected in the stable peak value stage of the testing strain-time curve, the temperature error is eliminated, and the final determination value of the timeliness strain of the core of the obtained measuring point is shown in the following table 4:
table 4X measuring point calculation strain selection table
In the calculation, the z axis in the local coordinate system is the axial direction of the core, and the drilled hole is a vertical hole, so that the main strain with an included angle close to 0 degree or 180 degrees with the z axis can be judged as the vertical strain, and the corresponding main stress is the vertical main stress. The other two directions of principal stress are horizontal large principal stress and horizontal small principal stress, and the results are shown in tables 5 and 6 below.
TABLE 5X measuring point principal strain calculation result table
TABLE 6 table of calculation results of principal stress at X measuring point
Claims (7)
1. The invention relates to a method for measuring ground stress by utilizing elastic recovery deformation of a rock core, which comprises the following steps:
(1) drilling a rock core;
(2) pasting a strain gauge;
(3) performing hysteresis elastic deformation strain test, namely placing the core at a non-disturbed position, opening acquisition equipment for monitoring, setting the acquisition interval to be 10min, and recording time and temperature data after effective data are pasted for 2 hours to obtain a hysteresis elastic deformation measurement curve;
(4) temperature calibration, namely stopping measurement when the estimated hysteretic elastic recovery strain reaches more than 95%, performing a temperature calibration experiment on the core, putting the core into a constant temperature box, performing the temperature calibration experiment according to the temperature change characteristics in monitoring to obtain the strain heat output at the temperature of 10 degrees, 20 degrees and 30 degrees, and eliminating the strain heat output during measurement;
(5) determining the elastic hysteresis flexibility, namely placing the in-situ rock core on an elastic hysteresis loading test instrument, estimating the stress level at a drilling test point, loading, and unloading after long-term strain is stable to obtain the elastic hysteresis strain recovery flexibility under the stress level;
(6) and (3) analyzing and processing data, calculating the hysteresis elasticity data, meeting the requirements of 3 times of parallel experiments with a measuring point to obtain the magnitude of the main stress, and preferentially selecting a directional core, or adopting later-stage drilling and camera shooting for positioning, or carrying out main stress direction judgment according to the calculation result of the ground stress and the combination of the structural characteristics.
2. The method of claim 1, wherein the method comprises the steps of: in the step (1), directional cores are preferably selected, or later-stage drilling and shooting positioning is adopted, or main stress direction judgment is carried out according to the ground stress calculation result and the structural characteristics.
3. The method of claim 1, wherein the method comprises the steps of: and (2) selecting strain gauges matched with heat output according to the rock types, selecting complete sections of the rock core, cleaning, wiping and polishing, pasting a plurality of groups of strain rosettes according to different directions, wrapping the rock core after pasting, and simultaneously reserving a section of rock core at the same position for orientation and calibration.
4. The method of claim 1, wherein the method comprises the steps of: in the step (4), firstly, a temperature calibration experiment is carried out, the core is placed in a constant temperature box, the temperature calibration experiment is carried out according to the temperature change characteristics in monitoring, the magnitude of the strain heat output at different temperatures is obtained, and the magnitude of the strain heat output is eliminated in the measurement.
5. The method of claim 1, wherein the method comprises the steps of: in the step (2), the core with the length larger than 150mm taken out from the drill hole is cleaned, the surface of the core is polished and the strain rosettes are adhered, three groups of strain sheets are adhered, the circumference is equally divided into three groups along the cross section of the measured core, and the included angle between every two adjacent strain sheets is 120 degrees.
6. The method of claim 1, wherein the method comprises the steps of: in the step (5), the hysteresis elastic strain recovery flexibility is calculated according to the following formula:
wherein Jas (t) is shear hysteresis elastic strain recovery flexibility, Jav (t) is volume hysteresis elastic strain recovery flexibility, σ1For axial loading, σ3In order to be a transverse load,1ain order to be under axial strain,3ais the transverse strain.
7. The method of claim 1, wherein the method comprises the steps of: in the step (6), the principal stress σi(i ═ 1,2,3) was calculated as follows:
σi＝ei(t)/Jas(t)+em(t)/Jav(t)+p0
in the formula ei(t) (i ═ 1,2,3) shows anelastic bias strain, em(t) hysteresis elastic mean principal strain, Jas (t) shear hysteresis elastic strain recovery compliance, Jav (t) volume hysteresis elastic strain recovery compliance, p0Is the pore pressure;
vertical principal stress sigmavCalculated as follows:
in the formula Ip,mp,npIs the cosine of the angle between the vertical main stress and the axis of the three main strains, k is the compliance ratio, Jas (t)/Jav (t) k.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202010509017.5A CN112129448A (en) | 2020-06-07 | 2020-06-07 | Method for measuring ground stress by using elastic recovery deformation of core |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202010509017.5A CN112129448A (en) | 2020-06-07 | 2020-06-07 | Method for measuring ground stress by using elastic recovery deformation of core |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CN112129448A true CN112129448A (en) | 2020-12-25 |
Family
ID=73851259
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN202010509017.5A Pending CN112129448A (en) | 2020-06-07 | 2020-06-07 | Method for measuring ground stress by using elastic recovery deformation of core |
Country Status (1)
| Country | Link |
|---|---|
| CN (1) | CN112129448A (en) |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN113108957A (en) * | 2021-03-18 | 2021-07-13 | 西南石油大学 | Rock core testing and extracting method for paleotectonic period ground stress |
| CN113756781A (en) * | 2021-08-17 | 2021-12-07 | 西南交通大学 | Low-cost ground stress test method |
Citations (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN1072019A (en) * | 1991-10-25 | 1993-05-12 | 北京科技大学 | A kind of earth stress measuring method of complete temperature compensation and device |
| US5386875A (en) * | 1992-12-16 | 1995-02-07 | Halliburton Company | Method for controlling sand production of relatively unconsolidated formations |
| CN102852516A (en) * | 2012-04-19 | 2013-01-02 | 北京大学 | Full-sew-length three-dimensional crushing data simulation method and device for oil and gas reservoir development |
| CN105784971A (en) * | 2016-03-25 | 2016-07-20 | 大连理工大学 | Experimental facility for utilizing anelastic strain recovery method for in situ analysis of aquo-complex settled layer stress state |
| CN106768581A (en) * | 2017-01-22 | 2017-05-31 | 孙东生 | A kind of horizontal stress coefficient of variation measuring method and device |
| CN108487911A (en) * | 2018-03-28 | 2018-09-04 | 中铁二院工程集团有限责任公司 | The compound crossing method construction method of longspan tunnel bilateral wall under complex geological condition |
| US20180311406A1 (en) * | 2017-04-28 | 2018-11-01 | Medtronic Vascular, Inc. | Shape memory articles and methods for controlling properties |
-
2020
- 2020-06-07 CN CN202010509017.5A patent/CN112129448A/en active Pending
Patent Citations (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN1072019A (en) * | 1991-10-25 | 1993-05-12 | 北京科技大学 | A kind of earth stress measuring method of complete temperature compensation and device |
| US5386875A (en) * | 1992-12-16 | 1995-02-07 | Halliburton Company | Method for controlling sand production of relatively unconsolidated formations |
| CN102852516A (en) * | 2012-04-19 | 2013-01-02 | 北京大学 | Full-sew-length three-dimensional crushing data simulation method and device for oil and gas reservoir development |
| CN105784971A (en) * | 2016-03-25 | 2016-07-20 | 大连理工大学 | Experimental facility for utilizing anelastic strain recovery method for in situ analysis of aquo-complex settled layer stress state |
| CN106768581A (en) * | 2017-01-22 | 2017-05-31 | 孙东生 | A kind of horizontal stress coefficient of variation measuring method and device |
| US20180311406A1 (en) * | 2017-04-28 | 2018-11-01 | Medtronic Vascular, Inc. | Shape memory articles and methods for controlling properties |
| CN108487911A (en) * | 2018-03-28 | 2018-09-04 | 中铁二院工程集团有限责任公司 | The compound crossing method construction method of longspan tunnel bilateral wall under complex geological condition |
Non-Patent Citations (3)
| Title |
|---|
| MATSUKI K .: "Anelastic strain recovery compliance of rocks and its application to in situ stress measurement", 《INTERNATIONAL JOURNAL OF ROCK MECHANICS & MINING SCIENCES》 * |
| 王连捷、孙东生、林为人 等: ""地应力测量的非弹性应变恢复法及应用实例"", 《地球物理学报》 * |
| 蔡美峰等: "平煤十矿地应力测量及其应用", 《北京科技大学学报》 * |
Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN113108957A (en) * | 2021-03-18 | 2021-07-13 | 西南石油大学 | Rock core testing and extracting method for paleotectonic period ground stress |
| CN113108957B (en) * | 2021-03-18 | 2021-11-30 | 西南石油大学 | Rock core testing and extracting method for paleotectonic period ground stress |
| US11372121B1 (en) | 2021-03-18 | 2022-06-28 | Southwest Petroleum University | Method for testing and extracting paleo-tectonic geostress based on rock core |
| CN113756781A (en) * | 2021-08-17 | 2021-12-07 | 西南交通大学 | Low-cost ground stress test method |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| CN103278614B (en) | Method and device for correcting dynamic and static rock mechanical parameters | |
| CN103257081B (en) | A kind of method that hydrocarbon-bearing pool rock mass mechanics ground in-situ model recovers and device | |
| JP6112663B2 (en) | In-situ rock test method and test equipment | |
| Figueiredo et al. | Determination of the stress field in a mountainous granite rock mass | |
| Zhang et al. | Characteristics of in-situ stress distribution in Zhengzhuang Region, Southern Qinshui Basin, China and its stress path during depletion | |
| CN112129448A (en) | Method for measuring ground stress by using elastic recovery deformation of core | |
| CN111982377B (en) | Deep hole differential stress evaluation method based on secondary sleeve core | |
| CN108169456A (en) | A kind of collapsible loess estimates big pressure evaluation method | |
| US11598703B2 (en) | Apparatus, system and method for mechanical testing under confined conditions | |
| Sun et al. | Three-dimensional in situ stress determination by anelastic strain recovery and its application at the Wenchuan Earthquake Fault Scientific Drilling Hole-1 (WFSD-1) | |
| CN104153768A (en) | Granite reservoir stratum reservoir performance evaluation method | |
| Min et al. | An experimental and numerical study of the in-situ stress measurement on transversely isotropic rock by overcoring method | |
| CN112412434B (en) | Improved loose sandstone ground stress calculation method | |
| Bakker et al. | Multiscale evaluation of potential damage in jetted lateral boreholes | |
| Zhang et al. | Geomechanical-evaluation enabled successful stimulation of a high-pressure/high-temperature tight gas reservoir in Western China | |
| Zhang et al. | Geomechanical evaluation enabled successful stimulation of a HPHT tight gas reservoir in western China | |
| Lin et al. | A case study of 3D stress orientation determination in Shikoku Island and Kii Peninsula, Japan | |
| CN115341886A (en) | Composite rock stratum fracturing simulation method and device | |
| CN111289174B (en) | Three-dimensional stress sensor calibration device and calibration method thereof | |
| CN114647913A (en) | Maximum level principal ground stress acquisition method based on Mohr-Coulomb criterion | |
| Dano et al. | Interpretation of dilatometer tests in a heavy oil reservoir | |
| Fjær et al. | Mechanical properties and stress data from laboratory analysis | |
| CN117189092B (en) | Soft rock ground stress testing method based on drilling cuttings particle size distribution | |
| CN220705697U (en) | Underground while-drilling ground stress measurement system | |
| CN116658157B (en) | Stratum pressure prediction method and system for tight sandstone gas reservoir |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| PB01 | Publication | ||
| PB01 | Publication | ||
| SE01 | Entry into force of request for substantive examination | ||
| SE01 | Entry into force of request for substantive examination | ||
| RJ01 | Rejection of invention patent application after publication | ||
| RJ01 | Rejection of invention patent application after publication |
Application publication date: 20201225 |