CN115980195A - Method and system for determining wave velocity field change and acoustic emission location of rock material - Google Patents
Method and system for determining wave velocity field change and acoustic emission location of rock material Download PDFInfo
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Abstract
The invention discloses a method and a system for determining the wave velocity field change and acoustic emission positioning of rock materials, wherein rock materials are used for manufacturing samples, and an acoustic emission probe is fixed on the surface of the samples; carrying out a loading test for generating fracture damage under a quasi-static loading condition, acquiring acoustic emission data of the whole process, and acquiring internal wave velocity matrix data of the sample at intervals of a certain period t in the loading process; according to the plane where the acoustic emission probe is located, a sample is discretized into discrete units, each sampling period t is divided into n sections, each section of time is tj, j =1,2, …, n, acoustic emission location in t1 and a wave velocity field in t2 are determined according to discrete units, wave velocity matrix data in the sample and acoustic emission data in t1, acoustic emission location in t2 and a wave velocity field in the next section of time are determined according to the wave velocity field in t2 and the acoustic emission data in t2, and acoustic emission location in the whole loading process wave velocity field is obtained through iteration. The invention can realize the determination of the wave velocity field change of the rock material and the acoustic emission positioning under the quasi-static loading condition.
Description
Technical Field
The invention belongs to the technical field of rock mechanics and fracture mechanics, and particularly relates to a method and a system for determining wave velocity field change and acoustic emission positioning of a rock material.
Background
In the field of rock mechanics, the rock material generates the phenomena of crack initiation, crack initiation and propagation through under the action of external force load. The detection of the rock fracture damage is an important basis for rock fracture evolution mechanism and instability early warning. Therefore, the research and the understanding of the fracture and damage process of the rock have very important significance for preventing the rock disaster and engineering construction.
In order to solve the fracture and damage process of the rock material, the related scholars have conducted a series of experimental researches on the problem, and acoustic wave and acoustic emission are two means which are widely applied. Along with the generation and the propagation of the rock cracks, the dynamic characteristics of the sound waves in the process of propagating in the rock are influenced. In the propagation process of the wave, the linear wave velocity can be reduced when the wave meets the defects of cracks, joints and the like, and the wave velocity field of the rock is inverted at different stages of fracture based on the principle to obtain the wave velocity fields at different stages, so that the development condition of the cracks in the rock can be reflected. For example, zhang Yanbo and the like construct an evaluation mechanism of a rock damage variable based on a wave velocity field, and Wang Xiaoran and the like reflect the space distribution and migration rule of the internal damage field of the rock sample by utilizing the evolution of the wave velocity field. Acoustic emission is a phenomenon in which a material emits transient elastic waves due to the rapid release of energy locally caused by fracture damage, also known as stress wave emission, and the concept was originally proposed by Schofield in 1961. By means of methods and technologies such as acoustic emission waveform processing, arrival time picking, space positioning and the like, information such as positioning, energy, characteristic parameters and the like of material microcracks can be obtained, and then monitoring of the fracture and damage process of the rock material is achieved. Behnia and the like mainly research the relationship between an acoustic emission signal and crack types, cracking and expansion, energy release tendency, accumulated damage and the like through characteristic parameters (AF, RA, AE energy, b value, AE impact and the like) of the acoustic emission signal; guo Tianyang et al studied the development of the fracture process using acoustic emission localized density profiles.
The accuracy of acoustic emission localization depends on the distribution of the material wave velocity field, and in general, rock materials are not isotropic, i.e., wave velocities differ in different directions. Microcracks or macrocracks generated in the fracture damage process can also cause the wave velocity of the rock material to change, which can greatly influence the accuracy of acoustic emission positioning, and further influence the judgment of the fracture damage area. The invention provides a method for determining the wave velocity field change and acoustic emission location of a rock material under a quasi-static loading condition, in order to facilitate the research on the wave velocity field and acoustic emission location in the process of cracking and damaging the rock material.
Disclosure of Invention
Aiming at the defects or the improvement requirements of the prior art, the invention provides a method and a system for determining the wave velocity field change and the acoustic emission positioning of the rock material.
To achieve the above object, according to an aspect of the present invention, there is provided a method for determining wave velocity field variation and acoustic emission location of a rock material, comprising:
manufacturing a regular-shaped sample by using a rock-soil material, and fixing a certain amount of acoustic emission probes on the surface of the sample in the same plane;
carrying out a loading test for generating fracture damage on the sample under a quasi-static loading condition, acquiring acoustic emission data of the whole process, and acquiring internal wave velocity matrix data of the sample at intervals of a certain period t in the loading process;
according to the plane where the acoustic emission probe is located, a sample is discretized into discrete units, each sampling period t is divided into n sections, the time of each section is tj, j =1,2, …, n, acoustic emission positioning in t1 and a wave velocity field in t2 are determined according to discrete units, wave velocity matrix data in the sample and acoustic emission data in t1, acoustic emission positioning in t2 and a wave velocity field in the next section are determined according to the wave velocity field in t2 and the acoustic emission data in t2, and acoustic emission positioning under the whole-process wave velocity field loading is obtained through iteration in sequence.
Further, the discretizing the sample into discrete units according to the plane of the acoustic emission probe comprises:
the sample is discretized into discrete units using squares according to the plane in which the acoustic emission probe lies.
Further, determining acoustic emission location in t1 and inverting a wave velocity field in t2 according to the discrete unit, the internal wave velocity matrix data of the sample and acoustic emission data in t 1;
determining an initial wave velocity field in t1 according to the discrete unit and the wave velocity matrix data in the sample;
determining acoustic emission positioning in t1 according to the initial wave velocity field and acoustic emission data in t 1;
and (5) positioning and inverting the wave velocity field in t2 according to the acoustic emission in t 1.
Further, the determining the initial wave velocity field in t1 according to the discrete unit and the wave velocity matrix data inside the sample comprises:
determining the wave velocity of an excitation-reception path of the acoustic emission probe according to the wave velocity matrix data;
taking the wave speed on the excitation-reception path as the wave speed on the discrete unit passed by the path;
and determining the wave velocity value of the discrete unit which is not passed by the excitation-reception path according to an interpolation method.
Further, the acoustic emission probe excites a wave velocity of a receive path, comprising:
wherein the obtained wave velocity v SR The excitation sensor S is connected with the receiving sensor R, i.e. the wave velocity on the excitation-receiving path, D is the transmission between the excitation sensor S and the receiving sensorDistance matrix between sensors R, T R Is a receiving end probe time matrix, T S Is the excitation end probe time matrix, and I is a unit column vector.
Further, the determining acoustic emission localization within t1 from the initial wave velocity field and acoustic emission data within t1 includes:
traversing all point coordinates of a plane where the acoustic emission probe is located to obtain a dot matrix;
and determining all points meeting the error requirement of the acoustic emission event according to the dot matrix, the initial wave velocity field and the acoustic emission data to obtain acoustic emission positioning in the t 1.
Further, determining all points meeting the error requirement of the acoustic emission event according to the dot matrix, the initial wave velocity field and the acoustic emission data to obtain acoustic emission positioning in t1, and the method comprises the following steps:
acoustic emission localization is a collection of all points that meet the error requirements:
wherein, i represents the ith excitation interval time of the AST; traversing all points of the plane where the acoustic emission probe is positioned by a length far less than the length and width or radius of the sample, and recording the lattice formed by the points as P and C i 1 Representing a discrete unit through which a connecting line of each point and the sensor in the dot matrix P passes; d is a radical of i 1 Then it means that the link crosses C i 1 The length of each discrete unit in the set, the number of sensors detecting the acoustic emission event is N, and the acoustic emission data is A i 1 And at this moment, a certain point in the lattice P meeting the requirement is the location L of the acoustic emission event.
Further, the locating and inverting the wave velocity field in t2 according to the acoustic emission in t1 includes:
determining a discrete unit through which a path of an acoustic emission probe passes;
the wave speed on the path of the acoustic emission probe is taken as the wave speed on the discrete unit passed by the path;
and determining the wave velocity value of the discrete unit which is not passed by the path of the acoustic emission probe in the acoustic emission positioning-acoustic emission probe path according to an interpolation method.
Further, the method for manufacturing the regular-shaped sample by using the geotechnical material comprises the following steps:
the rock soil material is made into cuboid, cube, semicircular disc or disc samples.
According to another aspect of the present invention there is provided a system for determining the wave velocity field variation and acoustic emission location of a rock material, comprising:
the first main module is used for manufacturing a regular-shaped sample by using a geotechnical material, and the surface of the sample is fixed with a certain amount of acoustic emission probes in the same plane;
the second main module is used for carrying out a loading test for generating fracture damage on the sample under a quasi-static loading condition, acquiring acoustic emission data in the whole process, and acquiring internal wave velocity matrix data of the sample at intervals of a certain period t in the loading process;
the third main module is used for discretizing the sample into discrete units according to the plane where the acoustic emission probe is located, dividing each sampling period t into n sections, wherein each section of time is tj, j =1,2, …, n, determining acoustic emission positioning in t1 and inverting a wave velocity field in t2 according to discrete units, internal wave velocity matrix data of the sample and acoustic emission data in t1, determining acoustic emission positioning in t2 and inverting a wave velocity field in the next section of time according to the wave velocity field in t2 and the acoustic emission data in t2, and sequentially iterating to obtain the acoustic emission positioning under the variable wave velocity field in the whole loading process.
In general, compared with the prior art, the above technical solution contemplated by the present invention can achieve the following beneficial effects:
1. the method for determining the wave velocity field change and the acoustic emission positioning of the rock material can realize the determination of the wave velocity field change and the acoustic emission positioning of the rock material under the quasi-static loading condition by acquiring acoustic emission data through an acoustic emission probe and periodically recording the wave velocity matrix data inside a sample through the AST function of an acoustic emission method monitoring device, and continuously calculating and inverting the wave velocity field and the acoustic emission event of the sample by using the acoustic emission data and the wave velocity matrix data inside the sample after discretizing the sample.
2. The system for determining the wave velocity field change and the acoustic emission positioning of the rock material collects acoustic emission data through the acoustic emission probe and periodically records the wave velocity matrix data inside the sample through the AST function of the acoustic emission method monitoring device, and can determine the wave velocity field change and the acoustic emission positioning of the rock material under the quasi-static loading condition by continuously calculating and inverting the wave velocity field and the acoustic emission event of the sample by using the acoustic emission data and the wave velocity matrix data inside the sample after discretizing the sample.
Drawings
FIG. 1 is a flow chart of a method for determining changes in wave velocity field and acoustic emission localization of a rock material under quasi-static loading conditions in accordance with an embodiment of the present invention;
FIG. 2 shows the dimensions of a rectangular sample and the manner in which an acoustic emission sensor is mounted in an embodiment of the invention;
FIG. 3 is an array of acoustic emission sensor connections according to an embodiment of the present invention;
FIG. 4 is a drawing of a rectangular sample discretization and discretization cell through which an array of acoustic emission sensor connections passes in accordance with embodiments of the present invention;
FIG. 5 is a schematic view of an array of acoustic emission localization and sensor connections obtained in accordance with an embodiment;
FIG. 6 is a flow chart of a method for determining the wave velocity field change and acoustic emission location of a rock material under quasi-static loading conditions according to the present invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention. In addition, the technical features involved in the embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.
In the description of the present invention, unless expressly stated or limited otherwise, the terms "connected," "connected," and "fixed" are to be construed broadly, e.g., as meaning permanently connected, removably connected, or integral to one another; can be mechanically or electrically connected; they may be directly connected or indirectly connected through intervening media, or may be connected through the use of two elements or the interaction of two elements. The specific meanings of the above terms in the present invention can be understood in specific cases to those skilled in the art.
As used herein, the singular forms "a", "an", "the" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms "comprises" and/or "comprising," when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof.
It will be understood by those within the art that, unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the prior art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein.
The method disclosed by the invention is applied to the fields of rock mechanics, fracture mechanics and the like, and can be used for determining the wave velocity field change and acoustic emission positioning of the rock material under the quasi-static loading condition.
When the rock is deformed by a force, primary or new microcracks in the rock are secondarily broken, and a phenomenon that transient elastic waves are radiated to the periphery is called Acoustic Emission (AE).
AST- -Auto Sensor Test, also called automatic Sensor setting, purpose: before or after the test, the sensor is checked whether the error exists or not, and the actual wave velocity is measured. The AST can obtain the wave velocity field distribution inside the sample in each sampling period in an active manner, and in the embodiment of the invention, the wave velocity matrix data inside the sample in each period is obtained by testing the AST through an active probe.
As shown in fig. 1 and 6, the method for determining the wave velocity field variation and acoustic emission location of the rock material according to the present invention includes steps S100 to S300.
S100, manufacturing a regular-shaped sample by using a rock-soil material, and fixing a certain amount of acoustic emission probes on the surface of the sample in the same plane;
rock materials are made into samples such as a cuboid, a semicircular disc or a circular disc through drilling or cutting and the like, and equal-quantity acoustic emission probes are fixed at the two ends of the samples to ensure that the acoustic emission probes are all positioned on the same plane.
In the present invention, the acoustic emission probe may be fixed by a magnetic probe fixing clip with a ring magnet. The specific operation is that firstly, the surface of a sample is cleaned by alcohol and is polished by abrasive paper, an annular iron ring is pasted at the planned fixed position of the probe, the inner size of the annular iron ring is matched with the size of the probe, a coupling agent is smeared on the surface of the probe and is placed in the iron ring, and then the magnetic suction probe fixing clamp is used for adsorbing the annular iron ring, so that the purpose of fixing the probe on the surface of the sample is achieved.
For disk or half disk samples, the fixture magnets and iron rings can be correspondingly shaped to fit the curved surface.
S200, carrying out a loading test for generating fracture damage on the sample under a quasi-static loading condition, acquiring acoustic emission data of the whole process, and acquiring wave velocity matrix data inside the sample at intervals of a certain period t in the loading process;
specifically, after the samples are processed, the samples are placed in corresponding loading devices for loading tests, wherein the loading tests include but are not limited to tests such as uniaxial compression, three-point bending, brazilian disc splitting and the like, the tests enable the samples to generate fracture damage, and signals generated by the acoustic emission events are collected by an acoustic emission probe and used for subsequent acoustic emission positioning or inversion of a wave velocity field.
It should be noted that the loading condition of the loading test is quasi-static loading, and the rest of the test conditions can be directly obtained according to the specific needs by the loading test requirements of the prior art, which is known in the art and is not described herein again.
In the loading experiment process, an acoustic emission probe is adopted to record acoustic emission data in the whole loading process, and meanwhile, by setting an AST function loading period t (namely interval time) of an acoustic emission monitoring device, internal wave velocity matrix data of a sample are collected once every a period of time t;
step S300, discretizing the sample into discrete units according to the plane where the acoustic emission probe is located, dividing each sampling period t into n sections, wherein the time of each section is tj, j =1,2, …, n, determining acoustic emission location in t1 and inverting a wave velocity field in t2 according to discrete units, internal wave velocity matrix data of the sample and acoustic emission data in t1, determining acoustic emission location in t2 and inverting a wave velocity field in the next section according to the wave velocity field in t2 and the acoustic emission data in t2, and sequentially iterating to obtain the acoustic emission location under the variable wave velocity field in the whole loading process.
It should be noted that, in the embodiment of the present invention, the wave velocity matrix data inside the sample per cycle is obtained by the active probe test AST. The AST can obtain the wave velocity field distribution in the sample in each sampling period in an active mode, and the acoustic emission positioning is to continuously correct the wave velocity field in a passive mode on the basis. The AST measuring method is characterized in that one mode is an active mode, the other mode is a passive mode, the active mode and the passive mode are used in a combined mode, the wave velocity field obtained by AST testing of an active probe is continuously corrected through acoustic emission positioning, and finally the accurate measurement of the wave velocity field is achieved.
Discretizing the sample into discrete units by using a square according to a plane determined by an acoustic emission probe fixed on the sample, and discretizing the wave velocity of each discrete unit of the sample after discretization according to the wave velocity on the discrete unit passing by taking the wave velocity on an excitation-reception path as a path; and determining the wave velocity value of the discrete unit which is not passed by the excitation-reception path according to an interpolation method.
The wave speed of the excitation-receiving path of the acoustic emission probe is determined according to the following method:
wherein the obtained wave velocity v SR Is the wave velocity on the excitation-receiving path, i.e. the line connecting the excitation sensor S and the receiving sensor R, D is the distance matrix between the excitation sensor S and the receiving sensor R, T R Is a receiving end probe time matrix, T S Is the excitation end probe time matrix, and I is a unit column vector.
And summarizing wave velocities of all discrete units to finally obtain an initial wave velocity field within the first period of time t1, and obtaining acoustic emission positioning within the t1 time according to the initial wave velocity field within the t1 time and acoustic emission data within the t1 time.
The specific method for determining an acoustic emission event from a wave velocity field and acoustic emission data is as follows:
firstly, traversing all points of a plane where an acoustic emission probe is located by a length which is far smaller than the length and the width (or the radius) of a sample, recording a dot matrix formed by the points, and solving a set of all points meeting the error requirement, namely positioning the acoustic emission.
The error requirement is as follows:
wherein i represents the ith excitation interval time of the AST, traverses all points of the plane where the acoustic emission probe is positioned by a length much smaller than the length and width (or radius) of the sample, and records the lattice formed by the points as P, C i 1 Representing the discrete units through which the connecting line between each point of the lattice P and the sensor passes, d i 1 Then it means that the link crosses C i 1 The length of each discrete unit in the set, the number of sensors detecting the acoustic emission event is N, and the acoustic emission data is A i 1 And at this moment, a certain point in the lattice P meeting the requirement is the location L of the acoustic emission event.
After acoustic emission positioning in t1 time is obtained, inverting a wave velocity field in the next time (in t2 time) according to the acoustic emission positioning in t1 time, firstly determining an acoustic emission positioning-acoustic emission probe path and a discrete unit passed by the acoustic emission positioning-acoustic emission probe path, and taking the wave velocity on the acoustic emission positioning-acoustic emission probe path as the wave velocity on the discrete unit passed by the path; and determining the wave velocity value of the discrete unit which is not passed by the acoustic emission probe in the acoustic emission positioning-acoustic emission probe according to an interpolation method. The final calculation can obtain the wave velocity field in the time t 2. Acoustic emission positioning can be obtained according to the wave velocity field and acoustic emission data, and the wave velocity field … … at the next time is inverted according to the acoustic emission positioning and the like, so that the wave velocity field and acoustic emission positioning in the whole loading process is finally obtained.
Specifically, acoustic emission localization — the determination of the wave velocity on the path of the acoustic emission probe is performed as follows:
the basic elements of the AST wave velocity field calculation are three:
1. the determined coordinates of the transmitting and receiving ends (to determine D);
2. determined wave propagation path (to determine matrix v) ij Subscript number of (a), i.e., discrete cell number located on the wave propagation path);
3. and determined transmission and reception time instants (T) R And T S )。
And acquiring the wave speed of an excitation-reception path of the acoustic emission probe, and acquiring the AST wave speed field according to the wave propagation path and the discrete units passed by the wave propagation path.
The calculation of the wave velocity field of the acoustic emission localization acoustic emission probe is based on the wave velocity field obtained by the AST measurement and the acoustic emission localization determined therefrom, with the purpose of correcting the wave velocity field of the AST measurement. This method also requires the above three basic elements:
1. determining an acoustic emission positioning point (transmitting end) and a probe position (receiving end);
2. a determined wave propagation path (the path between the acoustic emission localization point and the probe, i.e. the discrete units passed through);
3. the determined emission time (the start-oscillation time of the acoustic emission event) and the receiving time (the time when the probe receives the acoustic emission event signal).
The two methods are active wave velocity field measurement and passive wave velocity field measurement, but can use the wave velocity formula of the excitation-receiving path of the acoustic emission probe to calculate. The wave velocity of the path of the acoustic emission positioning-acoustic emission probe can be obtained according to a wave velocity calculation formula of the excitation-receiving path of the acoustic emission probe by only adjusting the transmitting end to be the acoustic emission positioning point, adjusting the transmitting moment to be the starting moment of the acoustic emission event and adjusting the receiving moment to be the moment when the probe receives the signal of the acoustic emission event.
The implementation basis of the various embodiments of the present invention is realized by performing programmed processing by a device having a central processing unit function. Therefore, in engineering practice, the technical solutions and functions thereof of the embodiments of the present invention can be packaged into various modules. Based on the actual situation, on the basis of the above embodiments, the embodiments of the present invention provide a system for determining the wave velocity field change and the acoustic emission location of the rock material, which is used for executing the method for determining the wave velocity field change and the acoustic emission location of the rock material in the above method embodiments. The method comprises the following steps:
the first main module is used for manufacturing a regular-shaped sample by using a geotechnical material, and the surface of the sample is fixed with a certain amount of acoustic emission probes in the same plane;
the second main module is used for carrying out a loading test for generating fracture damage on the sample under a quasi-static loading condition, acquiring acoustic emission data in the whole process, and acquiring internal wave velocity matrix data of the sample at intervals of a certain period t in the loading process;
and the third main module is used for discretizing the sample into discrete units according to the plane where the acoustic emission probe is located, dividing each sampling period t into n sections, wherein the time of each section is tj, j =1,2, …, n, determining acoustic emission positioning in t1 and inverting a wave velocity field in t2 according to discrete units, internal wave velocity matrix data of the sample and acoustic emission data in t1, determining acoustic emission positioning in t2 and inverting a wave velocity field in the next section of time according to the wave velocity field in t2 and the acoustic emission data in t2, and sequentially iterating to obtain the acoustic emission positioning under the whole-process variable wave velocity field.
It should be noted that, the apparatus in the apparatus embodiment provided by the present invention may be used for implementing methods in other method embodiments provided by the present invention, except that corresponding function modules are provided, and the principle of the apparatus embodiment provided by the present invention is basically the same as that of the apparatus embodiment provided by the present invention, so long as a person skilled in the art obtains corresponding technical means by combining technical features on the basis of the apparatus embodiment described above, and obtains a technical solution formed by these technical means, on the premise of ensuring that the technical solution has practicability, the apparatus in the apparatus embodiment described above may be modified, so as to obtain a corresponding apparatus class embodiment, which is used for implementing methods in other method class embodiments.
In order to make the implementation of the present invention clearer and clearer, the steps shown in fig. 2-5 are used to illustrate the uniaxial compression test of a rectangular parallelepiped sample under quasi-static loading condition, and the present application describes the specific implementation principle of the present invention in detail.
The rock material under investigation was drilled and cut into rectangular parallelepiped shaped samples, as shown in figure 2, in this example the sample dimensions were 50mm width, 25mm thickness, 100mm height. Before the test is started, enough acoustic emission probes in the same plane are distributed on two sides of the sample.
And placing the sample on loading equipment for carrying out uniaxial compression, and connecting the acoustic emission probe with acoustic emission acquisition equipment. An AST function activation time interval t is set and the test is subsequently developed. When the AST function is excited, each probe in the probe array is sequentially used as an acoustic wave excitation end and a receiving end, the array formed by connecting the probes is shown in figure 3, K sensors are fixed on one side of a sample, and 2K sensors are arranged in total.
It should be noted that the number of sensors and the connecting lines in fig. 3 are only exemplary and not limiting to the actual situation, all sensors are not drawn in fig. 3, and the sensors in the middle of the sample are omitted. Similarly, the connection lines formed by the sensor arrays are not drawn in full numbers, and the sensor arrays are described by taking a plurality of sensors as examples, which are not described herein again.
The wave velocity is calculated using the following formula
When the AST function is excited, each probe in the probe array sequentially serves as an acoustic excitation end and a receiving end, and the obtained wave velocity VSR is a wave velocity on a connection line (i.e., an excitation-receiving path) between the excitation end sensor S and the receiving end sensor R. Wherein D is a distance matrix between the excitation end sensor S and the receiving end sensor R, TR is a receiving end probe time matrix, TS is an excitation end probe time matrix, and I is a unit column vector.
Dividing the whole test loading time T into m parts by the AST excitation interval time T, and dividing the whole test loading time T into m parts by T i (i =1,2, …, m) indicates that each interval time t i Divided into n segments, each time period being t i j Represents (where i =1,2, …, m; j =1,2, …, n). The relationship between T and T is shown by the following equation:
the sample is discretized by using a square on a plane defined by the probe (hereinafter, referred to as a calculation plane). The number of cells after discretization is UxW in the width and height directions, respectively, followed by t i Wave velocity field inversion and acoustic emission positioning in a time period;
obtain the time period t i 1 Inner wave velocity field V i 1 Balance V i 1 Is the initial wave velocity field. At a time period t i 1 The discrete units through which each of the transmit-receive paths passes are determined. To exciteWave speed v on the receiving path SR As the wave velocity V on the discrete cell (the light green cell portion in fig. 4) through which the path passes. For the units which are not passed by the excitation-reception path, the wave velocity value on the units is determined by using an interpolation method. Finally obtaining the time period t on the calculation plane i 1 Internal initial wave velocity field V i 1 (u,w) ，(u＝1,2,…,U；v＝1,2,…,W)；
According to the initial wave velocity field V i 1 And acoustic emission data A i 1 Calculating the time period t i 1 Internal acoustic emission localization L i 1 . Wherein A is i 1 Represents a time period t i 1 The arrival time matrix formed by all the acoustic emission events detected by three or more acoustic emission sensors is calculated for each acoustic emission event location by the length l (l)<<U∪l<<W) traverse all points in the computation plane, the lattice of points made up of these points being denoted by P. C i 1 Representing the discrete units through which the connecting line of each point of the lattice P with the sensor passes, d i 1 Then it means that the link crosses C i 1 The length of each discrete unit in the array. Setting the number of the sensors which detect the acoustic emission event as N, wherein the errors between the occurrence moments of the events calculated by the arrival times of all the sensors which detect the acoustic emission event meet the following conditions:
at this time, a certain point in the lattice P meeting the requirement is the location L of the acoustic emission event. Repeating the step S6 to obtain a time period t i 1 Internal all acoustic emission localization L i 1 ；
Locating L using acoustic emission i 1 Back calculation time period t i 2 Inner wave velocity field V i 2 . At a time period t i 2 Within, the discrete units through which each event-sensor path passes are determined. An array of event and sensor connections is shown in FIG. 5Shown in the figure. At wave speed v on event-sensor path SR As the velocity V of the wave on the discrete element through which the path passes. For the event-sensor path non-passing cell, interpolation is used to determine the wave velocity value thereon. Finally obtaining the time period t on the calculation plane i 2 Internal wave velocity field V i 2 (u,w) ，(u＝1,2,…,U；v＝1,2,…,W)；
It is noted that during the time period t i Therein is only t i 1 Internal initial wave velocity field V i 1 Is inverted using the sensor AST mode, t i j+1 (j =1,2, …, n-1) all use t i j Acoustic emission localization within (j =1,2, …, n-1) is inverted. Steps S5 to S7 are repeated until i = m, j = n. Output wave velocity field V i j (i =1,2, …, m; j =1,2, …, n), and event location L i j (i =1,2, …, m; j =1,2, …, n). And acoustic emission positioning under a variable wave speed field in the whole loading process is realized.
It will be understood by those skilled in the art that the foregoing is only a preferred embodiment of the present invention, and is not intended to limit the invention, and that any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the scope of the present invention.
Claims (10)
1. A method for determining wave velocity field change and acoustic emission location of a rock material is characterized by comprising the following steps:
manufacturing a regular-shaped sample by using a rock-soil material, and fixing a certain amount of acoustic emission probes on the surface of the sample in the same plane;
carrying out a loading test for generating fracture damage on the sample under a quasi-static loading condition, acquiring acoustic emission data of the whole process, and acquiring internal wave velocity matrix data of the sample at intervals of a certain period t in the loading process;
according to the plane where the acoustic emission probe is located, a sample is discretized into discrete units, each sampling period t is divided into n sections, each section of time is tj, j =1,2, …, n, acoustic emission location in t1 and a wave velocity field in t2 are determined according to discrete units, wave velocity matrix data in the sample and acoustic emission data in t1, acoustic emission location in t2 and a wave velocity field in the next section of time are determined according to the wave velocity field in t2 and the acoustic emission data in t2, and acoustic emission location in the wave velocity field in the whole loading process is obtained through iteration in sequence.
2. The method for determining the wave velocity field change and the acoustic emission location of the rock material according to claim 1, wherein the discretizing the sample into discrete units according to the plane of the acoustic emission probe comprises:
the sample is discretized into discrete units using squares according to the plane in which the acoustic emission probe lies.
3. The method for determining the wave velocity field variation and acoustic emission localization of a rock material according to claim 2, wherein the determining the acoustic emission localization within t1 and inverting the wave velocity field within t2 according to the discrete unit, the sample internal wave velocity matrix data and the acoustic emission data within t1 comprises;
determining an initial wave velocity field in t1 according to the discrete unit and the wave velocity matrix data in the sample;
determining acoustic emission positioning in t1 according to the initial wave velocity field and acoustic emission data in t 1;
and (5) positioning and inverting the wave velocity field in t2 according to the acoustic emission in t 1.
4. The method for determining the wave velocity field variation and acoustic emission localization of the rock material according to claim 3, wherein the step of determining the initial wave velocity field in t1 according to the discrete unit and the internal wave velocity matrix data of the sample comprises the following steps:
determining the wave velocity of an excitation-reception path of the acoustic emission probe according to the wave velocity matrix data;
taking the wave speed on the excitation-reception path as the wave speed on the discrete unit passed by the path;
and determining the wave velocity value of the discrete unit which is not passed by the excitation-reception path according to an interpolation method.
5. The method for determining the wave velocity field variation and acoustic emission location of a rock material according to claim 4, wherein the acoustic emission probe excites the wave velocity of the receiving path, comprising:
wherein the obtained wave velocity v SR Is the wave velocity on the excitation-receiving path, i.e. the line connecting the excitation sensor S and the receiving sensor R, D is the distance matrix between the excitation sensor S and the receiving sensor R, T R Is a receiving end probe time matrix, T S Is the excitation end probe time matrix, and I is a unit column vector.
6. A method of determining wave velocity field changes and acoustic emission localization of a rock material according to claim 3, wherein determining acoustic emission localization within t1 from an initial wave velocity field and acoustic emission data within t1 comprises:
traversing all point coordinates of a plane where the acoustic emission probe is located to obtain a dot matrix;
and determining all points meeting the error requirement of the acoustic emission event according to the dot matrix, the initial wave velocity field and the acoustic emission data to obtain acoustic emission positioning in the t 1.
7. The method for determining the wave velocity field change and acoustic emission localization of a rock material according to claim 6, wherein the step of determining all points meeting the error requirement of an acoustic emission event according to the lattice, the initial wave velocity field and the acoustic emission data to obtain the acoustic emission localization within t1 comprises the following steps:
acoustic emission localization is a collection of all points that meet the error requirements:
wherein i represents the ith excitation interval time of the AST; traversing all points of the plane where the acoustic emission probe is located by a length which is far less than the length and width or radius of the sample, and recording the lattice formed by the points as P and C i 1 Representing a discrete unit through which a connecting line of each point and the sensor in the dot matrix P passes; d i 1 Then it means that the link crosses C i 1 The length of each discrete unit in the set, the number of sensors detecting the acoustic emission event is N, and the acoustic emission data is A i 1 And at this moment, a certain point in the lattice P meeting the requirement is the location L of the acoustic emission event.
8. The method for determining the wave velocity field variation and acoustic emission localization of a rock material according to claim 1, wherein inverting the wave velocity field in t2 according to the acoustic emission localization in t1 comprises:
determining a discrete unit through which a path of an acoustic emission probe passes;
acoustic emission positioning-wave speed on the path of an acoustic emission probe is taken as wave speed on a discrete unit passed by the path;
and determining the wave velocity value of the discrete unit which is not passed by the path of the acoustic emission probe in the acoustic emission positioning-acoustic emission probe path according to an interpolation method.
9. The method for determining the wave velocity field variation and acoustic emission localization of rock materials according to claim 1, wherein the step of fabricating the regular-shaped test sample from the rock materials comprises:
and manufacturing the rock-soil material into a cuboid, cube, semicircular disc or disc sample.
10. A system for determining wave velocity field changes and acoustic emission localization of a rock material, comprising:
the first main module is used for manufacturing a regular-shaped sample by using a geotechnical material, and the surface of the sample is fixed with a certain amount of acoustic emission probes in the same plane;
the second main module is used for carrying out a loading test for generating fracture damage on the sample under a quasi-static loading condition, acquiring acoustic emission data in the whole process, and acquiring wave velocity matrix data inside the sample at intervals of a certain period t in the loading process;
and the third main module is used for discretizing the sample into discrete units according to the plane where the acoustic emission probe is located, dividing each sampling period t into n sections, wherein the time of each section is tj, j =1,2, …, n, determining acoustic emission positioning in t1 and inverting a wave velocity field in t2 according to discrete units, internal wave velocity matrix data of the sample and acoustic emission data in t1, determining acoustic emission positioning in t2 and inverting a wave velocity field in the next section of time according to the wave velocity field in t2 and the acoustic emission data in t2, and sequentially iterating to obtain the acoustic emission positioning under the whole-process variable wave velocity field.
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN116593295A (en) * | 2023-07-19 | 2023-08-15 | 北京科技大学 | Method and device for improving acoustic emission positioning precision by utilizing rock anisotropic wave velocity |
| CN116642750A (en) * | 2023-07-24 | 2023-08-25 | 长江三峡集团实业发展(北京)有限公司 | Rock strain localization starting time prediction method, device and equipment |
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Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN116593295A (en) * | 2023-07-19 | 2023-08-15 | 北京科技大学 | Method and device for improving acoustic emission positioning precision by utilizing rock anisotropic wave velocity |
| CN116593295B (en) * | 2023-07-19 | 2023-10-03 | 北京科技大学 | Method and device for improving acoustic emission positioning precision by utilizing rock anisotropic wave velocity |
| CN116642750A (en) * | 2023-07-24 | 2023-08-25 | 长江三峡集团实业发展(北京)有限公司 | Rock strain localization starting time prediction method, device and equipment |
| CN116642750B (en) * | 2023-07-24 | 2023-10-20 | 长江三峡集团实业发展(北京)有限公司 | Rock strain localization starting time prediction method, device and equipment |
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