CN114019028B - Analysis method for detecting damage of fractured rock material by utilizing ultrasonic waves - Google Patents
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Classifications
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N29/00—Investigating or analysing materials by the use of ultrasonic, sonic or infrasonic waves; Visualisation of the interior of objects by transmitting ultrasonic or sonic waves through the object
- G01N29/04—Analysing solids
- G01N29/07—Analysing solids by measuring propagation velocity or propagation time of acoustic waves
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N3/00—Investigating strength properties of solid materials by application of mechanical stress
- G01N3/08—Investigating strength properties of solid materials by application of mechanical stress by applying steady tensile or compressive forces
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N2203/00—Investigating strength properties of solid materials by application of mechanical stress
- G01N2203/0014—Type of force applied
- G01N2203/0016—Tensile or compressive
- G01N2203/0019—Compressive
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N2203/00—Investigating strength properties of solid materials by application of mechanical stress
- G01N2203/0058—Kind of property studied
- G01N2203/0069—Fatigue, creep, strain-stress relations or elastic constants
- G01N2203/0075—Strain-stress relations or elastic constants
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N2291/00—Indexing codes associated with group G01N29/00
- G01N2291/02—Indexing codes associated with the analysed material
- G01N2291/028—Material parameters
- G01N2291/0289—Internal structure, e.g. defects, grain size, texture
Abstract
The invention discloses an analysis method for detecting fracture rock material damage by utilizing ultrasonic waves, which comprises the following steps: simultaneously carrying out an acoustic test and a uniaxial compression test on the rock material to be tested, and recording stress, strain values and acoustic signals in the test process; processing the obtained sound wave signal to obtain a sound wave signal time domain diagram, extracting the time t of the first wave sound, and passing through the formulaCalculating wave velocity v of sound waves transmitted in the test piece under different load actions; substituting the wave velocity v into the formulaCalculating the n-order change ratio DeltaV of the wave velocity V i The method comprises the steps of carrying out a first treatment on the surface of the According to the obtained DeltaV i And judging the position of the damage point by the numerical value. Compared with the prior art, the invention can change the ratio delta V by the n-order of the wave velocity of the dimensionless constant i And judging the damage condition and the damage point of the material in the loading process.
Description
Technical Field
The invention relates to an analysis method, in particular to an analysis method for detecting crack rock material damage by utilizing ultrasonic waves, which belongs to the technical field of sound wave detection, and particularly relates to detection of cracks of an engineering structure.
Background
Most underground engineering structures (retaining walls, pile foundations and tunnel linings) are made of rock materials and are in a pressurized state, and as pressure is applied, microcrack extension and expansion easily occur in the materials to cause damage accumulation, and finally structural deformation instability finally occurs, so that the engineering is integrally damaged, and even huge economic loss and casualties are caused. The existence of the weak surface of the joint structure such as the internal cracks of the rock is one of the sources of the damage of the rock mass, so that the identification or prediction of the crack growth of the internal cracks of the rock mass is particularly important.
The acoustic wave detection is used as an effective and sensitive nondestructive detection method, is widely applied to internal defect detection of structures, and is widely applied to research on micro cracks and crack closure in the stress loading process such as King, wherein the micro cracks and crack closure directly influence the wave velocity test result, and the change of the wave velocity in the loading process can be utilized to judge the propagation rule of the cracks. Chen Gengye and the like are used for researching the influence of rock fracture damage on ultrasonic attenuation, analyzing the relation between the quality factor reduction and the stress ratio, and further describing the acoustic law of crack propagation. The Kurtulus et al carried out ultrasonic testing on a marble test piece without joints and containing joints, and the results show that the attenuation of the joints is obvious, and the relation between the number of joints and the ultrasonic speed is analyzed.
The above research only analyzes the change of wave velocity along with cracks in the loading process, but the research on how to detect the damage point of the rock in the compression process is less, the detection of material damage is the research focus in the field of sound wave detection, and the method is one of the problems which need to be solved in the technical field of the existing engineering structure defect detection.
Disclosure of Invention
Aiming at the defects of the prior art, the invention provides an analysis method for detecting the damage of the fractured rock material by utilizing ultrasonic waves, which is used for acquiring acoustic signals by detecting the sound waves of the rock in the uniaxial compression process and then carrying out data processing on the extracted signals, thereby achieving the purpose of rapid and accurate detection.
The invention provides an analysis method for detecting damage of a crack rock material by utilizing ultrasonic waves, which specifically comprises the following steps:
step S1: simultaneously carrying out an acoustic test and a uniaxial compression test on the rock material to be tested, and recording stress, strain values and acoustic signals in the test process;
step S2: performing data processing on the sound wave signals obtained in the step S1 to obtain a sound wave signal time domain diagram, extracting a first wave time t, and calculating wave speeds v of sound waves transmitted in a test piece under different load actions through a formula (1);
wherein l is the length of the test piece, and t is the arrival time of the head wave of the sound wave propagating in the rock test piece;
step S3:substituting the wave velocity V obtained in the step S2 into a formula (2) to calculate an n-order change ratio DeltaV of the wave velocity V i ：
Wherein DeltaV i The ratio of the wave speed under the i-th level load to the wave speed difference under the front and rear level load is n-th power, namely the n-order change ratio of the wave speed; v i Is the wave velocity under the action of the i-th level load; n is an index, specifically a natural number other than 0, and the latter is also an order;
step S4: deltaV obtained according to step S3 i And judging the position of the damage point by the numerical value.
Preferably, in step S4, when DeltaV i When the change of the value is obvious, the delta V is corresponding to i The points of the values are points of injury.
Preferably, in step S3, the stress and strain values obtained in step S1 and the wave velocity v obtained in the corresponding step S2 are subjected to a stress (σ) -wave velocity (v), and the obtained stress (σ) -wave velocity (v) relationship is analyzed to approximate the relationship as a piecewise function.
Preferably, in step S4, the n-step change ratio DeltaV given in step S3 i Theoretical verification and explanation are carried out:
the linear continuous piecewise function with any slope k value change is set as follows:
wherein k is 1 、k 2 、k 3 Is the slope (k) of the segment function of the variable x belonging to each interval 1 ≠k 2 ≠k 3 )，t 1 、t 2 、t 3 The variable x is the intercept of the piecewise function of each interval; a to d represent the end points of the interval, and x=b and c are regarded as slope change points since there is a slope change before and after the function at the positions x=b and c;
then a characteristic parameter index y is defined based on the slope change points x=b, c i Let y i The n-order change ratio of (2) isBy calculating the index, a preset slope change point (x=b, c) can be accurately positioned according to the value change, and the method can be used for observing the value change in the stress (sigma) -wave velocity (v) relation obtained in the step S3, and the obtained value inflection point is defined as a damage point.
The beneficial effects are that:
the invention provides an analysis method for detecting damage of a crack rock-like material by utilizing ultrasonic waves, which calculates wave speeds of the acoustic waves transmitted in the rock-like material under different load actions according to the first wave sound extracted from a time domain diagram and defines n-order change ratio delta V of dimensionless constant wave speeds i Thereby judging the damage condition and the damage point of the material in the loading process. The method has the advantages of simple flow and obvious advantages:
(1) Judging whether damage points and damage points occur or not by measuring the wave speed;
(2) By calculating DeltaV under different load actions i Can pass through DeltaV i The damage of the material is judged, the damage point of the material in the loading process is roughly described, and the damage and the destruction are effectively judged;
(3) The invention has simple operation flow, stable measurement result and visual and accurate judgment result.
Description of the drawings:
FIG. 1 is a flow chart of the method of the present invention;
FIG. 2 is a schematic diagram of a piecewise function provided in embodiment 1 of the present invention;
fig. 3 shows Δv of the piecewise function provided in embodiment 1 of the present invention when n=1, 2,3 i Schematic representation as a function of x value;
FIG. 4 is a model of a pre-fabricated fracture test piece of example 1 of the present invention;
FIG. 5 is a graph showing stress-strain curves for all test pieces of example 1 of the present invention;
FIG. 6 is a time domain diagram of the complete test piece (A-0-0) of example 1 of the present invention during uniaxial compression;
FIG. 7 is a time domain plot during uniaxial compression of a vertical fracture test (A-30-90) of example 1 of the present invention;
FIG. 8 is a time domain diagram of the uniaxial compression of a horizontal slit test piece (A-30-0) according to example 1 of the present invention;
FIG. 9 is a schematic view of the head wave jump point in embodiment 1 of the present invention;
FIG. 10 is a graph of longitudinal wave velocity versus stress for a vertical fracture test piece of example 1 (corresponding to the graph of σ -v in Table 2-1) according to the present invention;
FIG. 11 is a graph of longitudinal wave velocity versus stress for a horizontal slit test piece according to example 1 of the present invention (corresponding to the graph of σ -v in Table 2-2);
FIG. 12 shows the wave velocity 2-step change ratio DeltaV of the complete test piece according to example 1 of the present invention i A figure;
FIG. 13 shows the wave velocity 2-order change ratio DeltaV of the vertical fracture test piece according to example 1 of the present invention i A figure;
FIG. 14 shows the wave velocity 2-order change ratio DeltaV of the horizontal slit test piece according to example 1 of the present invention i A drawing.
The specific embodiment is as follows:
the invention is further described in detail below with reference to the drawings and detailed description.
Example 1
The embodiment provides an analysis method for detecting damage of a fractured rock material by utilizing ultrasonic waves, which is shown in fig. 1 and comprises the following steps:
(1) And (3) preparing a test piece: river sand with the grain diameter of less than 1.18mm is screened out, and the mixing ratio of sand, cement, gypsum and water is 1:0.2:0.05:0.1, mixing, and placing into a test piece manufacturing module with 100mm and 100 mm;
(2) Manufacturing prefabricated cracks: obliquely inserting an aluminum sheet into the vibrated test piece raw material obtained in the step 1 according to the design angle and the length to manufacture a crack, fixing the aluminum sheet to wait for the test piece to be coagulated, placing the test piece at room temperature (about 20 ℃), naturally drying, ventilating, standing for 48h, taking out, curing to a specified age 28d, wherein the height of the crack is 100mm, and the thickness is 0.5mm, and the model is shown in fig. 4;
(3) All test pieces were numbered as test pieces numbered "A-50-90," A "representing sand: and (3) cement: gypsum: the mass ratio of the water is 1:0.2:0.05:0.1; "50" means that the fracture length is 50mm and "90" means that the fracture inclination angle is 90 °;
(4) Adopting a CMT5105 microcomputer to control a single-sheet universal tester to carry out a single-axis compression test on a test piece, and automatically acquiring and recording data such as stress, strain and the like by a system in the experimental process;
(5) Performing acoustic wave test on the test piece by adopting a TH204 type acoustic wave tester, respectively placing the transducers at two ends of the test piece for acoustic wave test, performing acoustic wave test once (namely 0 kN) in initial time, and performing acoustic wave test once every 1kN test until the test piece is damaged or the acoustic wave cannot be identified;
(6) And (3) carrying out data processing on the sound wave signals to obtain a time domain diagram (shown in fig. 6, 7 and 8) of the test piece in the loading process, finding out a head wave jump point (shown in fig. 9) in the time domain signals, calculating the wave speed of the test piece under the action of each level of load by combining a formula (1), and drawing a corresponding stress (sigma) -wave speed (v) relation diagram (shown in fig. 10 and 11) according to the table 1-1 and the table 1-2 as shown in the table 1-1 and the table 1-2.
TABLE 1-1 wave velocities for vertical fractures under different loads
TABLE 1-2 wave velocities for horizontal fractures under different loads
As can be seen from fig. 10 and 11, for the different fracture test pieces, the wave speed slightly increases at the initial stage of loading, and as the load increases, the crack starts to expand, and the wave speed decreases; the load is further increased, the crack continues to expand, new crack is generated, and the sound wave speed is obviously reduced; when the load is increased to a limit state, the wave speed is rapidly reduced until the crack is penetrated, and the test piece is damaged; the inventors have thus further studied and analyzed the resulting wave velocity v according to the above phenomenon, and found that the sigma-v relationship can be regarded approximately as a piecewise function.
(7) Theoretical verification is carried out on the sigma-v relation obtained in the step 6, and as shown in figure 2, a slope k is arbitrarily defined 1 ＝5、k 2 ＝2、k 3 ＝3、k 4 ＝-2.5、k 5 ＝-4、k 6 A piecewise function of = -1, with x = 2, 4, 6, 8, 10 set as the slope change point, the resulting function is:
based on the function, then y i The calculation formula of the n-order change ratio of (2) is:
wherein y is i 、y i-1 、y i+1 Respectively, x=x in the piecewise function i 、x i-1 、x i+1 The corresponding function value.
According to the change of the slope |k| value corresponding to the front and rear adjacent segments in the piecewise function, the following conditions are adopted:
(1) when |k| increases or decreases, then y i N-order change ratio of (2)That is, when |k| increases, x=4, 8 in the slope change point, and when |k| decreases, x=2, 6, 10 in the slope change point;
(2) when |k| is unchanged, then y i N-order change ratio DeltaV of (2) i ＝1。
According to the two changes of the k value, through y i The corresponding Δv when n=1, 2,3 is calculated by the n-order change ratio formula of (c) i Values (results are shown in Table 2), showing DeltaV i As x varies (as shown in fig. 3).
TABLE 2
As can be seen from Table 2 and FIG. 3, the slope change points 2, 4, 6, 8, 10 have ΔV i The values are all relative to DeltaV i The change when=1 is obvious, which indicates that the index y is defined by i The n-order change ratio of (2) can accurately position a preset slope change point; and DeltaV i The value of (c) increases faster as the order of n increases. DeltaV i The numerical change of (a) is obvious, which shows that the index can accurately locate the slope change point, can fully reflect the slope change point with smaller slope change, and if n is smaller, deltaV i When the change of the value of n is less significant, we can increase the value of n and then make calculation analysis.
(8) Substituting the wave velocity V of the crack under different load effects into the formula (2) to calculate the wave velocity n-order change ratio DeltaV of the material i In this example, the n-step change ratio DeltaV was calculated on the basis of the wave velocity V of the whole test piece A-0-0 in tables 1-1 and 1-2 i The results of (n=1, 2,3, 4) are shown in table 3, and fig. 12 is plotted according to the data obtained in table 3. As can be seen from fig. 12, when n=1, 2,3, 4, Δv i The change in value is all evident, and when n=2, Δv i The damage positions of the crack closing stage, the crack stabilizing and propagating stage and the crack destabilizing stage are clearly seen in the figure in the interval (0, 1000), so that the damage positions are later DeltaV i The values can all be calculated with n=2.
TABLE 3 wave speed n-order change ratio DeltaV of complete test pieces A-0-0 i
(9) Since n=2 can already account for Δv i Calculating the wave velocity 2-order change ratio DeltaV of the crack under different load actions i The calculation results are shown in tables 4-1 and 4-2, and thus, fig. 13 and 14 are plotted.
TABLE 4-1 under different loadsWave velocity 2-order change ratio DeltaV of vertical fracture i
TABLE 4-2 wave velocity 2-order change ratio DeltaV for horizontal fractures under different loads i
In which the slope |k| varies before and after all points due to errors in the test data, the inventors have made a data analysis process for only points where the increase in |k| is significant and DeltaV i Points with larger values, i.e. damage points defined below, are the object of analysis.
(10) Taking a complete rock sample A-0-0 as an example, for DeltaV i The calculation process is described in detail: when the stress σ=2 MPa, σ=5 MPa, |k| decreases, and when the stress σ=7 MPa, σ=11 MPa, σ=15 MPa, |k| increases, there is a wave velocity 2-step change ratio Δv corresponding to the case (1) in step 7 i Is calculated as DeltaV 2 ＝9、ΔV 5 ＝9、ΔV 7 ＝9、ΔV 11 ＝40、ΔV 15 =289; when the stress sigma is other, the slope |k| is changed, but the change is relatively small, and the wave speed 2-order change ratio delta V i The calculation result of (2) is in the vicinity of the value 1, corresponding to the case (2) in step 7. As described in the foregoing method, the stress σ=2mpa, σ=5mpa, σ=7mpa, σ=11mpa, σ=15mpa is the change point, i.e., the damage point.
Conclusion of the test
Analysis by taking a complete rock sample A-0-0 as an example combines the sigma-epsilon stress strain curve graph and sigma-delta V of the test piece i The figure shows that:
(1) Crack closure stage (oa stage in fig. 5). Because the test piece is manufacturedInitial damage (microcracks and bubbles) inevitably exists in the process, and under the action of load, the initial microcracks are closed to cause the wave speed to change by 2 steps in ratio delta V i The onset of abrupt change may correspond to the point a of the line elastic phase in the crack closure phase (i.e., fig. 5), where the corresponding stress σ=2mpa corresponds to the first inflection point in fig. 11 and is defined as the first damage point. The first point of damage occurs at substantially the same stress level for different types of pre-slit test pieces.
(2) A crack steady propagation stage (ab stage in fig. 5). Continuously loading the crack into a damage expansion area, starting to expand and penetrate the crack in the test piece, obviously increasing the initial crack width, and gradually reducing the wave speed along with the increase of the stress; the damage is accumulated continuously, the damage area is expanded, but no destabilization damage occurs, corresponding to the second mutation point in fig. 11 and defined as the second damage point, at which time the corresponding stress σ=11 MPa.
(3) Crack destabilization propagation stage (stage bc in fig. 5). The surface cracks are continuously expanded, new cracks are continuously increased, the wave speed is rapidly reduced along with the increase of stress, and the test piece finally develops to a full-damage state until the loss of bearing capacity is damaged; when sigma-sigma c ＝14MPa，σ-ΔV i A third point of inflection is evident in the figure, which is defined as the third point of damage, indicating that the test piece has reached the limit of damage at this time, and therefore, this point is taken as the point of failure of the structure, and measures are required to be taken in time to enhance its stability.
Using wave velocity n-order change ratio DeltaV i The numerical value of the (B) is compared with the wave velocity value, the crack change condition of a test piece can be rapidly monitored, the damage of the rock-like material under uniaxial compression can be judged, and under the action of different loads, the wave velocity 2-order change ratio delta V of the rock-like material i When the value of the (B) is obviously changed, the point is a damage point, and the analysis method provided by the invention can enable the measurement result to be more accurate and visual.
The foregoing is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the invention is described in terms of the preferred embodiments, it is not intended to be limiting. Therefore, the simple modification or variation of the above embodiments according to the technical substance of the present invention shall fall within the scope of the protection of the technical solution of the present invention.
Claims (4)
1. An analysis method for detecting damage of a fractured rock material by utilizing ultrasonic waves is characterized by comprising the following steps:
step S1: simultaneously carrying out an acoustic test and a uniaxial compression test on the rock material to be tested, and recording stress, strain values and acoustic signals in the test process;
step S2: performing data processing on the sound wave signals obtained in the step S1 to obtain a sound wave signal time domain diagram, extracting a first wave time t, and calculating wave speeds v of sound waves transmitted in a rock test piece under different load actions through a formula (1);
wherein l is the length of the test piece, and t is the arrival time of the head wave of the sound wave propagating in the rock test piece;
step S3: substituting the wave velocity V obtained in the step S2 into a formula (2) to calculate an n-order change ratio DeltaV of the wave velocity V i ：
Wherein DeltaV i The ratio of the wave speed under the i-th level load to the wave speed difference under the front and rear level load is n-th power, namely the n-order change ratio of the wave speed; v i Is the wave velocity under the action of the i-th level load; n is an index, specifically a natural number other than 0, and the latter is also an order;
step S4: deltaV obtained according to step S3 i Numerical determination of the position of the injury point, the obtained DeltaV i The numerical inflection point is the injury point.
2. The analysis method for detecting damage to fractured rock material by using ultrasonic waves according to claim 1, whereinCharacterized in that, in step S4, when DeltaV i When the change of the value is obvious, the delta V is corresponding to i The points of the values are points of injury.
3. The method according to claim 1, wherein in step S3, the stress and strain values obtained in step S1 are related to the wave velocity v obtained in step S2 by a stress (σ) -wave velocity (v), and the obtained stress (σ) -wave velocity (v) relationship is analyzed to approximate a piecewise function.
4. The method for analyzing damage to fractured rock material by ultrasonic waves according to claim 1, wherein in step S4, the n-step change ratio DeltaV given in step S3 is i Theoretical verification and explanation are carried out:
the linear continuous piecewise function with any slope k value change is set as follows:
wherein k is 1 、k 2 、k 3 Is the slope (k) of the segment function of the variable x belonging to each interval 1 ≠k 2 ≠k 3 )，t 1 、t 2 、t 3 The variable x is the intercept of the piecewise function of each interval; a to d represent the end points of the interval, and x=b and c are regarded as slope change points since there is a slope change before and after the function at the positions x=b and c;
then a characteristic parameter index y is defined based on the slope change points x=b, c i Let y i The n-order change ratio of (2) isBy calculating the index, a preset slope change point (x=b, c) can be accurately positioned according to the value change, and the method can be used for observing the value change in the stress (sigma) -wave velocity (v) relation obtained in the step S3, and the obtained value inflection point is defined as a damage point.
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