CN113804248B - Nondestructive ground stress testing device and method using digital speckle and finite element technology - Google Patents
Nondestructive ground stress testing device and method using digital speckle and finite element technology Download PDFInfo
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- CN113804248B CN113804248B CN202110973452.8A CN202110973452A CN113804248B CN 113804248 B CN113804248 B CN 113804248B CN 202110973452 A CN202110973452 A CN 202110973452A CN 113804248 B CN113804248 B CN 113804248B
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01D—MEASURING NOT SPECIALLY ADAPTED FOR A SPECIFIC VARIABLE; ARRANGEMENTS FOR MEASURING TWO OR MORE VARIABLES NOT COVERED IN A SINGLE OTHER SUBCLASS; TARIFF METERING APPARATUS; MEASURING OR TESTING NOT OTHERWISE PROVIDED FOR
- G01D21/00—Measuring or testing not otherwise provided for
- G01D21/02—Measuring two or more variables by means not covered by a single other subclass
Abstract
The invention relates to a nondestructive ground stress testing device and a nondestructive ground stress testing method using digital speckle and finite element technology. The technical proposal is as follows: the front face of the full-diameter rock core clamp holder is provided with a high-speed camera or a camera, the upper side of the clamp holder is connected with a servo control system through a data line, the servo control system injects ring pressure into the clamp holder, and the high-speed camera or the camera guides the collected deformation and displacement into a finite element model to carry out ground stress inversion. The beneficial effects are that: the invention does not damage the internal structure of rock, can conveniently observe the extrusion deformation condition of the rock sample surface in the test process, is convenient for recording the displacement field and strain field information of the rock sample in the whole loading process, establishes a finite element model as an initial and boundary condition to carry out ground stress inversion, can simultaneously acquire the magnitude and direction of ground stress, and can simultaneously adjust the full-diameter test rock core according to different depths and lithology, thereby acquiring more rock sample change information and realizing the description and calculation of the ground stress of multiple layers.
Description
Technical Field
The invention relates to a device and a method for testing stratum ground stress in the field of oil gas drilling and production, in particular to a device and a method for testing lossless ground stress by utilizing digital speckle and finite element technology, which can simultaneously acquire the magnitude and the direction of ground stress.
Background
Currently, hydraulic fracturing measures, deployment and optimization of a fluid production well pattern, horizontal well orientation and hydraulic fracturing must be implemented in oil and gas field development, taking the direction, size and distribution rule of the stress of the present day into consideration. However, the existing method for testing the ground stress direction of the rock in the laboratory, such as the rock acoustic emission method combined with the paleogeomagnetic orientation, the differential strain method combined with the paleogeomagnetic orientation, the sound velocity anisotropic method combined with the paleogeomagnetic orientation and the like, needs to cut the rock core in the testing process, damages the rock core, influences the subsequent test after the rock core is damaged, and meanwhile, the test data are difficult to repeat, particularly the existing ground stress magnitude and direction testing method generally needs to be completed by coupling a plurality of experiments together, the selected rock core is difficult to ensure parallel experiments, so that the uncertainty of the test result is high, and the error is sometimes larger; secondly, the traditional sonic method requires that the rock has no obvious cracks and has uniform texture, and the selection of the rock is greatly limited.
The research on the ground stress is widely paid attention to by oil and gas exploration and development personnel, and the ground stress belongs to an internal force of rock in a natural state and reflects the stress state of the rock in the underground. At present, the ground stress measurement work is carried out in a plurality of countries, the measurement method has more than ten kinds, and the measurement instruments are nearly hundred kinds. The various measurement methods that occur in succession fall broadly into two main categories: direct and indirect measurements. The direct method measurement is divided into: a flat jack method, a rigid inclusion stress meter method, a hydraulic fracturing method and an acoustic emission method; the indirect measurement includes: trepanning stress relief, local stress relief, strain relaxation measurements, geophysical prospecting. At present, two stress measuring methods are mainly adopted at home and abroad: stress (strain) relief and hydraulic fracturing. The solution method is divided into three types: strain gauges, and strain gauges, wherein strain gauges are widely used. The strain gauge method for measuring the three-dimensional stress by single drilling is available, but has the defects of low precision and reliability and troublesome operation.
With the rapid development of petroleum industry, more and more unconventional oil and gas resources such as shale gas, shale oil, sand and the like are found everywhere in China, and the conventional differential strain or Kesaier acoustic emission ground stress experimental test method is difficult to meet the requirement of test precision due to the complex geological characteristics of the reservoirs, so that the development of novel ground stress test equipment and method is necessary. The two ground stress experimental test methods can not meet the test requirements.
Disclosure of Invention
The invention aims at solving the defects existing in the prior art and provides a nondestructive ground stress testing device and method by utilizing digital speckle and finite element technology.
The invention relates to a nondestructive ground stress testing device utilizing digital speckle and finite element technology, which adopts the technical scheme that:
including full diameter core holder (a), high-speed camera or camera (b), servo control system (c) and power (d), full diameter core holder (a) openly one side install high-speed camera or camera (b), servo control system (c) is connected through the data line to the upside of full diameter core holder (a), power (d) is connected through the wire in the front of full diameter core holder (a), servo control system (c) are connected to computer (e) through the data line for pour into the ring pressure to full diameter core holder (a), high-speed camera or camera (b) be connected to computer (e) through the data line.
Preferably, the full-diameter core holder (a) comprises a holder outer cylinder (1), a rear end plug (2), a front baffle ring (3), a ring pressure capsule (4), a ring pressure liquid injection nozzle (5) and an optical lamp belt (6), wherein the ring pressure capsule (4) is arranged in an inner cavity of the holder outer cylinder (1), a full-diameter core (7) is arranged in the ring pressure capsule (4), the rear end plug (2) is arranged at the rear side of the holder outer cylinder (1), the inner end surface of the rear end plug (2) is in contact with the full-diameter core (7), and the outer end surface is positioned at the outer side of the holder outer cylinder (1); the front side of the outer cylinder (1) of the clamp holder is provided with a front baffle ring (3), and the inner side of the front baffle ring (3) is provided with an optical lamp strip (6); the upper side of the outer cylinder (1) of the clamp holder is provided with a ring pressure liquid injection nozzle (5).
Preferably, the outer cylinder (1) of the clamp holder comprises an outer cylinder body (1.1), a ring pressure liquid injection hole (1.2), a baffle ring limiting step (1.3), a capsule limiting step (1.4), a rear thread (1.5) and a front thread (1.6), wherein the outer cylinder body (1.1) is of a cylindrical structure, and the upper end of the outer cylinder body (1.1) is provided with the ring pressure liquid injection hole (1.2) for installing a ring pressure liquid injection nozzle (5); the inner wall of the outer cylinder body (1.1) is provided with a baffle ring limiting step (1.3) and a capsule limiting step (1.4) which respectively form a baffle ring cavity and a capsule cavity, the inner diameter of the baffle ring cavity is larger than that of the capsule cavity, the outer wall of the baffle ring cavity is provided with a front thread (1.6), and the inner wall of the rear end of the outer cylinder body (1.1) is provided with a rear thread (1.5).
Preferably, the rear end plug (2) comprises an end plug main body (2.1), an end plug external thread (2.2) and a rotator (2.3), wherein the front end of the end plug main body (2.1) is contacted with the full-diameter core (7), and the middle part of the end plug main body (2.1) is provided with a convex end plug external thread (2.2) for being movably connected with the rear thread (1.5) of the holder outer barrel (1); the rear end of end plug main part (2.1) is equipped with rotor (2.3) for drive end plug main part (2.1) rotation, and end plug main part (2.1) and rotor (2.3) adopt 316 grades high strength steel to make, through connecting heating equipment, can realize the heating effect of full diameter rock core (7), be used for simulating stratum temperature.
Preferably, the front baffle ring (3) comprises a baffle ring main body (3.1), an inner baffle ring (3.2), a baffle ring external thread (3.3) and a baffle ring external step (3.4), wherein the inner wall of the front end of the baffle ring main body (3.1) is provided with the inner baffle ring (3.2), the inner cavity of the rear end of the baffle ring main body (3.1) is of a conical structure, the outer wall of the rear end of the baffle ring main body (3.1) is provided with the baffle ring external step (3.4), and the outer wall of the middle part of the baffle ring main body (3.1) is provided with the baffle ring external thread (3.3).
Preferably, the annular pressure capsule (4) is made of annular silica gel.
The invention relates to a using method of a nondestructive ground stress testing device by utilizing digital speckle and finite element technology, which adopts the technical scheme that the using method comprises the following steps:
(1) Placing the processed full-diameter core into the inner cavity of the outer barrel (1) of the holder, screwing in the rear end plug (2) and screwing up; (2) The front end of the holder outer barrel (1) is provided with a front baffle ring (3), and an optical lamp band (6) is arranged in the middle of the front baffle ring (3) and used for supplementing light to the full-diameter core; (3) At the moment, hydraulic oil is injected into the annular pressure capsule (4) through the servo control system (c) to be loaded at constant pressure at a certain speed, and meanwhile, a high-speed camera or a camera (b) is used for recording the deformation condition of the full-diameter rock core; (4) After the experiment is finished, the data analysis finds the maximum horizontal stress azimuth of the full-diameter rock core; (5) Processing and analyzing the acquired and stored digital images, and then comparing and analyzing the gray scale of the images of the full-diameter rock core before and after deformation to obtain the correlation coefficient of the digital images; and recording deformation and displacement parameters of the rock in the loading process to obtain a strain value of the rock, and simultaneously deriving the strain value for subsequent finite element numerical simulation.
Preferably, finite element geometric modeling is carried out according to a specific core size, after a rock strain field is acquired, strain field variable data are imported into a finite element model, in actual import, related unit data can be interpolated according to an interpolation method to obtain unit integral points, initial mechanical parameters and the like are brought in according to actual rock mechanical parameters of the core, then stress conditions are loaded to solve a numerical simulation displacement field and a strain field, a least square objective function is constructed, and an actual measurement displacement field and the strain field are subjected to repeated comparison correction with the displacement field and the strain field acquired by digital speckle, and particle swarm optimization is carried out to obtain a minimum differential stress comparison result; at the moment, the calculation result of the ground stress and the direction of the rock can be completely obtained; if the ground stress measured data exist in the field, such as a small pressure test, a well wall caving analysis result, microseism monitoring and imaging logging, correction and quality control can be performed on the obtained ground stress numerical simulation result.
Compared with the prior art, the invention has the following beneficial effects:
in the compression process of the full-diameter rock sample, the invention can record the stress-strain curve of the full-diameter rock sample in the loading direction, and simultaneously, the deformation process of the surface of the rock sample can be recorded by a high-speed camera or a camera; the invention does not damage the internal structure of rock, can conveniently observe the extrusion deformation condition of the rock sample surface in the test process, is convenient for recording the displacement field and strain field information of the rock sample in the whole loading process, establishes a finite element model as an initial and boundary condition to carry out ground stress inversion, can simultaneously acquire the magnitude and direction of ground stress, and can simultaneously adjust the full-diameter test rock core according to different depths and lithology, thereby acquiring more rock sample change information and realizing the description and calculation of the ground stress of multiple layers.
Drawings
FIG. 1 is a schematic illustration of the overall connection of the present invention;
FIG. 2 is a schematic structural view of a full diameter core holder;
FIG. 3 is a schematic structural view of the outer cylinder of the clamper;
FIG. 4 is a schematic view of the structure of the rear end plug;
FIG. 5 is a schematic view of the structure of the front stop ring;
FIG. 6 is a schematic view of the structure of a ring-pressed capsule and a ring-pressed nozzle;
FIG. 7 is a force deflection schematic of a tested full diameter core;
FIG. 8 is a schematic diagram of digital speckle reference and target image subregions;
in the upper graph: full diameter core holder a, high-speed video camera or camera b, servo control system c, power d, computer e, full diameter core holder a, high-speed video camera or digital camera b, servo control system c, power d, computer e, holder urceolus 1, rear end plug 2, front baffle ring 3, annular pressure capsule 4, annular pressure injection nozzle 5, optical lamp band 6, full diameter core 7;
the capsule comprises an outer cylinder body 1.1, a ring pressure liquid injection hole 1.2, a baffle ring limit step 1.3, a capsule limit step 1.4, a rear thread 1.5, a front thread 1.6, an end plug main body 2.1, an end plug external thread 2.2, a rotator 2.3, a baffle ring main body 3.1, an inner baffle ring 3.2, a baffle ring external thread 3.3 and a baffle ring external step 3.4.
Detailed Description
The preferred embodiments of the present invention will be described below with reference to the accompanying drawings, it being understood that the preferred embodiments described herein are for illustration and explanation of the present invention only, and are not intended to limit the present invention.
Embodiment 1, referring to fig. 1, the nondestructive ground stress testing device using digital speckle and finite element technology comprises a full-diameter core holder a, a high-speed camera or camera b, a servo control system c and a power supply d, wherein the high-speed camera or camera b is arranged on one side of the front surface of the full-diameter core holder a, the upper side of the full-diameter core holder a is connected with the servo control system c through a data wire, the front surface of the full-diameter core holder a is connected with the power supply d through a wire, the servo control system c is connected with a computer e through a data wire and used for injecting hydraulic pressure into the full-diameter core holder a so as to simulate formation pressure, and the high-speed camera or camera b is connected with the computer e through a data wire.
Referring to fig. 2, the full-diameter core holder a of the invention comprises a holder outer cylinder 1, a rear end plug 2, a front baffle ring 3, a ring pressure capsule 4, a ring pressure liquid injection nozzle 5 and an optical lamp belt 6, wherein the ring pressure capsule 4 is arranged in the inner cavity of the holder outer cylinder 1, a full-diameter core 7 is arranged in the ring pressure capsule 4, the rear end plug 2 is arranged at the rear side of the holder outer cylinder 1, the inner end surface of the rear end plug 2 is contacted with the full-diameter core 7, and the outer end surface is positioned at the outer side of the holder outer cylinder 1; the front side of the outer cylinder 1 of the clamp holder is provided with a front baffle ring 3, and the inner side of the front baffle ring 3 is provided with an optical lamp strip 6; the upper side of the outer cylinder 1 of the clamp holder is provided with a ring-pressing liquid injection nozzle 5.
Referring to fig. 3, an outer cylinder 1 of a holder of the invention comprises an outer cylinder 1.1, a ring pressure liquid injection hole 1.2, a stop ring limit step 1.3, a capsule limit step 1.4, a rear thread 1.5 and a front thread 1.6, wherein the outer cylinder 1.1 is of a cylindrical structure, and the upper end of the outer cylinder 1.1 is provided with the ring pressure liquid injection hole 1.2 for installing a ring pressure liquid injection nozzle 5; the inner wall of the outer cylinder body 1.1 is provided with a baffle ring limiting step 1.3 and a capsule limiting step 1.4, a baffle ring cavity and a capsule cavity are respectively formed, the inner diameter of the baffle ring cavity is larger than that of the capsule cavity, the outer wall of the baffle ring cavity is provided with a front thread 1.6, and the inner wall of the rear end of the outer cylinder body 1.1 is provided with a rear thread 1.5.
Referring to fig. 4, the rear end plug 2 of the present invention includes a plug body 2.1, an external thread 2.2 of the plug, and a rotator 2.3, wherein the front end of the plug body 2.1 contacts with a full diameter core 7, and a raised external thread 2.2 of the plug is provided in the middle of the plug body 2.1 for movable connection with the rear thread 1.5 of the outer barrel 1 of the holder; the rear end of end plug main part 2.1 is equipped with rotor 2.3 for drive end plug main part 2.1 rotation, and end plug main part 2.1 and rotor 2.3 adopt 316 grades high strength steel to make, through connecting heating equipment, can realize the heating effect of full diameter rock core 7, be used for simulating formation temperature.
Referring to fig. 5, the front baffle ring 3 of the invention comprises a baffle ring main body 3.1, an inner baffle ring 3.2, a baffle ring external thread 3.3 and a baffle ring external step 3.4, wherein the inner wall of the front end of the baffle ring main body 3.1 is provided with the inner baffle ring 3.2, the inner cavity of the rear end of the baffle ring main body 3.1 is of a conical structure, the outer wall of the rear end of the baffle ring main body 3.1 is provided with the baffle ring external step 3.4, and the outer wall of the middle part of the baffle ring main body 3.1 is provided with the baffle ring external thread 3.3.
Referring to fig. 6, the ring-pressed capsule 4 of the present invention is made of ring-shaped silica gel.
The application method of the nondestructive ground stress testing device using digital speckle and finite element technology comprises the following steps:
(1) Placing the processed full-diameter core into the inner cavity of the outer barrel 1 of the holder, screwing in the rear end plug 2 and screwing up; (2) The front end of the holder outer barrel 1 is provided with a front baffle ring 3, and an optical lamp band 6 is arranged in the middle of the front baffle ring 3 and used for supplementing light to the full-diameter core; (3) At the moment, hydraulic oil is injected into the annular pressure capsule 4 through the servo control system c to be loaded at constant pressure at a certain speed, and meanwhile, a high-speed camera or a camera b is used for recording the deformation condition of the full-diameter rock core; (4) After the experiment is finished, the data analysis finds the maximum horizontal stress azimuth of the full-diameter rock core; (5) Processing and analyzing the acquired and stored digital images, and then comparing and analyzing the gray scale of the images of the full-diameter rock core before and after deformation to obtain the correlation coefficient of the digital images; and recording deformation and displacement parameters of the rock in the loading process to obtain a strain value of the rock, and simultaneously deriving the strain value for subsequent finite element numerical simulation.
Preferably, finite element geometric modeling is carried out according to a specific core size, after a rock strain field is acquired, strain field variable data are imported into a finite element model, in actual import, related unit data can be interpolated according to an interpolation method to obtain unit integral points, initial mechanical parameters and the like are brought in according to actual rock mechanical parameters of the core, then stress conditions are loaded to solve a numerical simulation displacement field and a strain field, a least square objective function is constructed, and an actual measurement displacement field and the strain field are subjected to repeated comparison correction with the displacement field and the strain field acquired by digital speckle, and particle swarm optimization is carried out to obtain a minimum differential stress comparison result; at the moment, the calculation result of the ground stress and the direction of the rock can be completely obtained; if the ground stress measured data exist in the field, such as a small pressure test, a well wall caving analysis result, microseism monitoring and imaging logging, correction and quality control can be performed on the obtained ground stress numerical simulation result.
In addition, the processed full-diameter core refers to: and (3) trimming the end face of the full-diameter rock core with a diamond turning tool to be smooth, and spraying speckles on the end face of the rock.
And then, placing the full-diameter core into a lateral clamp holder to laterally load the rock with equal pressure, simultaneously taking a picture of the rock end face at a high speed by using a high-speed camera, and analyzing the picture by using digital speckle software after the experiment is finished. The main stress is released after the rock is drilled due to the different stress of the rock in the stratum. The stress varies, the strain released by the rock varies, the greater the stress the greater the strain released and vice versa. The rock face may therefore exhibit different strains when the rock is laterally loaded with the same stress. Therefore, the speckle analysis software can see the strain field of the rock along with the change of lateral pressure, the direction with larger strain is the maximum horizontal stress, and the direction perpendicular to the strain is the minimum horizontal stress.
In addition, in a computer in which images measured by the digital speckle correlation method exist in a matrix form, motion information of a measured object point is estimated from an image matrix, and an assumption is needed at this time, namely: the same point keeps the same gray level during the motion process, namely, the gray level is not changed, and a specific calculation expression can be expressed as follows:
（1）
（2）
wherein:ffor the reference image to be a reference image,gis the target image.w(x;a)=x+d(x;a)Is a coordinate function.u，vRespectively isx，yDisplacement in the direction. To solve foruAndvfirstly, using points to be measured in a reference imagex 0 ,y 0 ) Selecting a certain area as a reference image subarea for the center, and then finding out the largest correlation with the reference image subarea in the target image by a certain searching methodx’, y’) Point target image subregions, with particular reference to fig. 8;
after the correlation function is selected, the correlation search is started, and the process is shown in the figure. Firstly, selecting a reference image subarea, endowing a deformation parameter with an initial value, and substituting the initial value into a shape function to obtain the model under the initial valuex’,y’) And (5) a dot. In the deformation process of the object, the displacement is not generally the whole pixel, sox’,y’) The gray value of a dot must be obtained by subpixel interpolation. When all points in the reference image subarea correspond tox’,y’) After the gray values of the points are all obtained, the correlation function values are calculated according to the normalized covariance correlation function and compared, and if the preset threshold is reached, the deformation parameters are considered to be the obtained deformation parameters. If not, reassigning calculation to the deformation parameters until the requirements are met. In order to characterize the degree of similarity of the reference image and the target image subregion, a similarity function is requiredC. The digital speckle uses the correlation function as a judging basis, searches in the reference image and the target image, and finds the correlation functionThe number is the sub-region of the extremum. The similarity of the reference areas is measured by adopting cross correlation coefficients, and a definition formula is as follows:
（3）
(x, y) and (x ', y') each represent an arbitrary point before deformation of the sub-region and its corresponding post-deformation point coordinates. When the similarity function C value=1, it is explained that the two sub-regions are completely correlated. When the similarity function C value=0, it is explained that the two sub-regions are completely uncorrelated.
After the digital speckle strain field data are acquired, carrying out numerical simulation on the strain field by establishing a finite element calculation model to form a parameter identification error function of the finite element deformation field and the digital speckle strain field, wherein a calculation formula is expressed as follows:
（6）
wherein:ε xn 、ε yn 、τ xyn respectively finite element numerical calculation xDirectional strain,yDirectional strain, shear strain;ε xs 、ε ys 、τ xys calculated by a digital speckle correlation method in full-diameter rock core loading deformation experimentsxDirectional strain,yDirectional strain, shear strain; in addition, in the case of the optical fiber,nfor the number of integration points in the finite element model,m = n。
when the strain field inversion optimization algorithm is selected, the algorithm needs to be considered to fully search space in a calculation group, and high calculation efficiency and calculation accuracy are realized. When the calculation accuracy does not reach the standard, the initial parameters are required to be further adjusted, trial calculation is performed again until the whole model calculation result is completely converged.
The above description is only a few preferred embodiments of the present invention, and any person skilled in the art may make modifications to the above described embodiments or make modifications to the same. Accordingly, the corresponding simple modifications or equivalent changes according to the technical scheme of the present invention fall within the scope of the claimed invention.
Claims (4)
1. A nondestructive ground stress testing device using digital speckle and finite element technology is characterized in that: the high-speed camera or camera (b) is arranged on one side of the front face of the full-diameter core holder (a), the upper side of the full-diameter core holder (a) is connected with the servo control system (c) through a data wire, the front face of the full-diameter core holder (a) is connected with the power supply (d) through a wire, the servo control system (c) is connected to a computer (e) through a data wire and is used for injecting ring pressure into the full-diameter core holder (a), and the high-speed camera or camera (b) is connected to the computer (e) through a data wire;
the full-diameter core holder (a) comprises a holder outer cylinder (1), a rear end plug (2), a front baffle ring (3), a ring pressure capsule (4), a ring pressure liquid injection nozzle (5) and an optical lamp belt (6), wherein the ring pressure capsule (4) is arranged in an inner cavity of the holder outer cylinder (1), a full-diameter core (7) is arranged in the ring pressure capsule (4), the rear end plug (2) is arranged at the rear side of the holder outer cylinder (1), the inner end surface of the rear end plug (2) is in contact with the full-diameter core (7), and the outer end surface is positioned at the outer side of the holder outer cylinder (1); the front side of the outer cylinder (1) of the clamp holder is provided with a front baffle ring (3), and the inner side of the front baffle ring (3) is provided with an optical lamp strip (6); the upper side of the outer cylinder (1) of the clamp holder is provided with a ring pressure liquid injection nozzle (5);
the outer cylinder (1) of the clamp comprises an outer cylinder body (1.1), a ring pressure liquid injection hole (1.2), a baffle ring limiting step (1.3), a capsule limiting step (1.4), a rear thread (1.5) and a front thread (1.6), wherein the outer cylinder body (1.1) is of a cylindrical structure, and the upper end of the outer cylinder body (1.1) is provided with the ring pressure liquid injection hole (1.2) for installing a ring pressure liquid injection nozzle (5); the inner wall of the outer cylinder body (1.1) is provided with a baffle ring limiting step (1.3) and a capsule limiting step (1.4) which respectively form a baffle ring cavity and a capsule cavity, the inner diameter of the baffle ring cavity is larger than that of the capsule cavity, the outer wall of the baffle ring cavity is provided with a front thread (1.6), and the inner wall of the rear end of the outer cylinder body (1.1) is provided with a rear thread (1.5);
the rear end plug (2) comprises an end plug main body (2.1), an end plug external thread (2.2) and a rotator (2.3), wherein the front end of the end plug main body (2.1) is contacted with a full-diameter core (7), and the middle part of the end plug main body (2.1) is provided with a convex end plug external thread (2.2) for being movably connected with a rear thread (1.5) of the holder outer barrel (1); the rear end of the end plug main body (2.1) is provided with a rotator (2.3) for driving the end plug main body (2.1) to rotate, the end plug main body (2.1) and the rotator (2.3) are made of 316-grade high-strength steel, and the heating effect of the full-diameter core (7) can be realized by connecting heating equipment so as to simulate the stratum temperature;
the front baffle ring (3) comprises a baffle ring main body (3.1), an inner baffle ring (3.2), a baffle ring external thread (3.3) and a baffle ring external step (3.4), wherein the inner wall of the front end of the baffle ring main body (3.1) is provided with the inner baffle ring (3.2), the inner cavity of the rear end of the baffle ring main body (3.1) is of a conical structure, the outer wall of the rear end of the baffle ring main body (3.1) is provided with the baffle ring external step (3.4), and the outer wall of the middle part of the baffle ring main body (3.1) is provided with the baffle ring external thread (3.3).
2. The non-destructive ground stress testing apparatus utilizing digital speckle and finite element techniques of claim 1, wherein: the ring-pressed capsule (4) is made of annular silica gel.
3. A method of using the non-destructive ground stress testing apparatus of claim 1 or 2 utilizing digital speckle and finite element techniques, comprising the steps of:
(1) Placing the processed full-diameter core into the inner cavity of the outer barrel (1) of the holder, screwing in the rear end plug (2) and screwing up; (2) The front end of the holder outer barrel (1) is provided with a front baffle ring (3), and an optical lamp band (6) is arranged in the middle of the front baffle ring (3) and used for supplementing light to the full-diameter core; (3) At the moment, hydraulic oil is injected into the annular pressure capsule (4) through the servo control system (c) to be loaded at constant pressure at a certain speed, and meanwhile, a high-speed camera or a camera (b) is used for recording the deformation condition of the full-diameter rock core; (4) After the experiment is finished, the data analysis finds the maximum horizontal stress azimuth of the full-diameter rock core; (5) Processing and analyzing the acquired and stored digital images, and then comparing and analyzing the gray scale of the images of the full-diameter rock core before and after deformation to obtain the correlation coefficient of the digital images; and recording deformation and displacement parameters of the rock in the loading process to obtain a strain value of the rock, and simultaneously deriving the strain value for subsequent finite element numerical simulation.
4. A method of using a non-destructive ground stress testing apparatus utilizing digital speckle and finite element techniques as defined in claim 3, wherein:
performing finite element geometric modeling according to a specific core size, after acquiring a rock strain field, introducing strain field variable data into a finite element model, and performing actual introduction, or performing interpolation on related unit data according to an interpolation method to obtain unit integral points, wherein initial mechanical parameters are brought in according to actual rock mechanical parameters of the core, loading stress conditions to solve a numerical simulation displacement field and a strain field, constructing a least square objective function, performing repeated comparison correction on the actual measurement displacement field and the strain field and the displacement field and the strain field acquired by digital speckle, and performing optimization treatment by using a particle swarm algorithm to obtain a minimum differential stress comparison result; at the moment, the calculation result of the ground stress and the direction of the rock can be completely obtained; if the ground stress measured data exists in the field, the obtained ground stress numerical simulation result can be corrected and the quality can be controlled.
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| Application Number | Priority Date | Filing Date | Title |
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| CN202110973452.8A CN113804248B (en) | 2021-08-24 | 2021-08-24 | Nondestructive ground stress testing device and method using digital speckle and finite element technology |
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| CN202110973452.8A CN113804248B (en) | 2021-08-24 | 2021-08-24 | Nondestructive ground stress testing device and method using digital speckle and finite element technology |
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| CN113804248A CN113804248A (en) | 2021-12-17 |
| CN113804248B true CN113804248B (en) | 2023-09-22 |
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