System and method for detecting crushing degree of fractured formation rock mass
By monitoring the strain of the core column using load application equipment and fiber optic sensing technology, the problems of large errors and long time consumption in the detection of fractured strata were solved, and quantitative analysis of the degree of fracture was realized.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-12-18
- Publication Date
- 2026-04-10
AI Technical Summary
Existing technologies for detecting the degree of fracture in fractured rock masses suffer from large errors, long processing times, poor representativeness, and reliance on engineers' experience, making quantitative analysis impossible.
A load-applying device is used to apply pressure to the fractured core column. Combined with a laser, measuring optical fiber, and optical fiber demodulation equipment, the number of natural cracks on the surface of the core column is identified by monitoring the optical fiber strain data, and the fracture index is calculated.
It achieves efficient and reliable quantitative characterization of the degree of fracture in fractured rock masses, avoids subjective errors in manual identification, and can identify minute cracks that are difficult to detect by conventional methods.
Smart Images
Figure CN121830293A_ABST
Abstract
Description
Technical Field
[0001] This application relates to the fields of geotechnical engineering and oil and gas drilling technology, and in particular to a system and method for detecting the degree of fracture in fractured rock masses. Background Technology
[0002] The deep and ultra-deep geological environments are complex, with ancient geological ages and multiple tectonic movements, making it easy to form fractured strata in areas of intense tectonic deformation. Drilling into fractured strata carries the potential for complex and severe wellbore instability events, which can lead to large-scale block collapses, lost circulation, and stuck drill bits. This will hinder efficient and safe drilling in deep formations, making the problem of wellbore instability in fractured formations an urgent issue to be addressed.
[0003] The complex downhole problems faced by fractured formations stem from the discontinuous and fractured structural characteristics of the underground rock mass. Therefore, conducting research on the systemic mechanical behavior of fractured rock masses has significant theoretical and practical value. To achieve quantitative analysis of the mechanical behavior of fractured rock masses, it is first necessary to accurately quantitatively characterize their degree of fracture. Rock mass integrity is an important indicator for evaluating rock mass quality and the degree of fracture. Currently, there are three main methods for evaluating rock mass integrity: the elastic P-wave velocity testing method, represented by the rock mass integrity coefficient Kv; the structural surface statistical method, represented by the volume joint number Jv; and the borehole quality index RQD method. However, in practical engineering applications, these methods often suffer from problems such as large errors, long processing times, high costs, poor representativeness, and reliance on engineer experience. Summary of the Invention
[0004] This application provides a system and method for detecting the degree of fracture in fractured rock masses, which solves the problems of large errors, long time consumption, poor representativeness, reliance on engineer experience, and inability to achieve quantitative analysis in existing methods for detecting fracture indicators of fractured rock masses.
[0005] To address the aforementioned technical problems, this application provides a system for detecting the degree of fracture in fractured rock masses, comprising: a load application device, a laser, a coupler, a measuring optical fiber, and an optical fiber demodulation device; The load application device is used to apply pressure to a fractured core column, which is equipped with a measuring optical fiber. The laser and fiber demodulation device are connected to the measurement fiber via a coupler. The laser emitted by the laser is split into a first signal light and a second signal light by the coupler. The first signal light enters the measurement fiber, and the second signal light enters the fiber demodulation device. The measurement fiber generates Rayleigh backscattered light, which enters the fiber demodulation device through the coupler. The fiber demodulation device is used to obtain fiber strain data by demodulating the beat frequency signal formed by the Rayleigh backscattered light of the first signal light and the second signal light. The fiber strain data is used to determine the breakage index.
[0006] In a further embodiment of this application, the measuring optical fiber is spirally wound around the surface of the fractured core column from the measurement starting point until it reaches the measurement termination point of the fractured core column.
[0007] In a further embodiment of this application, the measuring optical fiber is subjected to calcination treatment using a calcined metal rod at the positions of the first and second measuring points of the fractured core column.
[0008] In a further embodiment of this application, the measuring optical fiber is bonded to the surface of the fractured core column via ethyl α-cyanoacrylate.
[0009] In a further embodiment of this application, the surface of the fractured core column is coated with sealant.
[0010] In a further embodiment of this application, the sealant includes KE-441-T adhesive.
[0011] In a further embodiment of this application, the system further includes: a processing device; The processing equipment is used to determine the crushing parameters according to the following operations: The fiber strain data is preprocessed; Based on the preprocessed fiber strain data, the strain field diagram on the surface of the core column was determined. The strain gradient points are found from the strain field diagram on the surface of the core column using a peak-finding function. The number of cracks is determined based on the strain gradient points; Calculate the breakage index based on the number of cracks.
[0012] A second aspect of this application provides a method for detecting the degree of fracturing in fractured rock masses, applicable to the system described in any of the foregoing embodiments, the method comprising: A fractured core column equipped with a measuring optical fiber is placed on the load application device; The load application device is controlled to operate in a constant speed loading mode; The fiber optic demodulation device is controlled to analyze and record fiber optic strain data until the core column or the measuring fiber changes, at which point the recording of fiber optic strain data stops. Based on the fiber strain data, the breakage index is determined.
[0013] In a further embodiment of this application, determining the breakage index based on the optical fiber strain data includes: The fiber strain data is preprocessed; Based on the preprocessed fiber strain data, the strain field diagram on the surface of the core column was determined. The strain gradient points are found from the strain field diagram on the surface of the core column using a peak-finding function. The number of natural cracks is determined based on the strain gradient points. The breakage index is calculated based on the number of natural cracks.
[0014] In a further embodiment of this application, the preprocessing of the fiber strain data includes: The fiber strain data is thinned out over time to obtain the first processed data. Identify and adjust the abnormal sway strain values in the first processed data to obtain the second processed data; The second processed data is subjected to noise reduction processing to obtain the third processed data; The third processed data is filtered to obtain preprocessed fiber strain data.
[0015] In a further embodiment of this application, determining the strain field map of the core column surface based on the preprocessed fiber strain data includes: Based on the preprocessed fiber strain data, the axial strain data is obtained by decomposition. Based on the axial strain data, the strain field diagram on the surface of the core column was determined.
[0016] In a further embodiment of this application, the fracturing index is calculated based on the number of natural cracks, including: The crushing index is calculated using the following formula: ; in, J v For breakage indicators, N The number of cracks L This represents the length of the fiber optic measurement segment.
[0017] In a further embodiment of this application, the method further includes: The fractured core column was prepared using the following steps: The rock obtained by cutting the fractured blocks yielded multiple standard core columns; By controlling the air pump with different preset pump pressures, the impact pin is driven to strike the top and side surfaces of different standard core columns, resulting in core columns with different degrees of fragmentation.
[0018] This application provides a system and method for detecting the degree of fracture in fractured rock masses. By applying pressure to a fractured core column using a load-applying device, and by using a laser and a measuring optical fiber mounted on the core column, the surface field variation of the core column under external load can be monitored. The number of natural cracks is counted based on the strain data from the optical fiber, thereby obtaining the fracture index. This application does not require observation of the rock, effectively avoiding subjective errors caused by manual identification, and can identify tiny cracks that are difficult to detect using conventional methods. It provides an efficient and reliable technical approach for the quantitative characterization of the degree of fracture in fractured rock masses.
[0019] To make the above and other objects, features and advantages of this application more apparent and understandable, preferred embodiments are described below in detail with reference to the accompanying drawings. Attached Figure Description
[0020] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.
[0021] Figure 1 This paper shows a first structural diagram of a fractured rock mass detection system according to an embodiment of this application; Figure 2 This shows a second structural diagram of the fracture degree detection system for fractured rock mass according to an embodiment of this application; Figure 3A A schematic diagram of the fiber optic winding measurement scheme according to an embodiment of this application is shown; Figure 3B A physical diagram of the fiber optic winding measurement scheme according to an embodiment of this application is shown; Figure 4 This invention illustrates a schematic diagram of the spatial location of the marked measuring points according to an embodiment of this application. Figure 5 A schematic diagram illustrating the calculation process of the crushing index in an embodiment of this application is shown; Figure 6 The image shows a uniaxially loaded fiber strain field diagram of a core column according to an embodiment of this application; Figure 7 The diagram shows the results of finding the strain gradient (number of natural cracks) in an embodiment of this application. Figure 8 A flowchart of the fiber optic strain data preprocessing procedure according to an embodiment of this application is shown; Figure 9 A flowchart of a method for detecting the degree of fracture in fractured rock mass according to an embodiment of this application is shown; Figure 10A structural diagram of a computer device according to an embodiment of this application is shown.
[0022] Explanation of symbols in the attached drawings: 101. Load application equipment; 102. Laser; 103. Coupler; 104. Measuring optical fibers; 105. Fiber optic demodulation equipment; 20. Core column; 201. High-Temperature and High-Pressure Rock Triaxial Apparatus; 1002. Computer equipment; 1004, Processor; 1006. Memory; 1008. Drive mechanism; 1010. Input / Output Module; 1012. Input devices; 1014. Output devices; 1016. Presentation device; 1018. Graphical User Interface; 1020. Network interface; 1022. Communication link; 1024. Communication bus. Detailed Implementation
[0023] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.
[0024] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this application are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of this application described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion; for example, a process, method, apparatus, product, or device that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or devices.
[0025] This specification provides the operational steps of the methods described in the embodiments or flowcharts, but based on conventional or non-inventive labor, more or fewer operational steps may be included. The order of steps listed in the embodiments is merely one possible execution order among many and does not represent the only possible execution order. In actual system or device products, the methods shown in the embodiments or drawings can be executed sequentially or in parallel.
[0026] In existing technologies, there are three main methods for evaluating rock mass integrity: the elastic longitudinal wave velocity test method, represented by the rock mass integrity coefficient Kv; the structural surface statistical method, represented by the volume joint number Jv; and the borehole quality index RQD method.
[0027] These testing methods each have their advantages and disadvantages. The advantage of the elastic P-wave velocity testing method is that the testing process does not require sample destruction and the testing cost is low. However, the testing range of P-waves in rock masses with abundant joints and fractures is very limited, and the P-wave response is not ideal when the rock mass is significantly damaged. The borehole quality index (RQD) method, which obtains RQD values or the number of joints per unit volume of core during core drilling, is intuitive and quick to operate. However, core sampling in fractured strata is difficult, making it hard to obtain complete core columns. Furthermore, for strata with low fracture levels, the size of the fractured particles is relatively large. When core drilling and sampling in such strata, the sampling range may be completely contained within a single fractured particle, failing to effectively cover the contact interface between adjacent fractured particles. This results in the obtained core exhibiting macroscopic integrity characteristics, which does not match the actual characteristics of fractured strata. The number of volumetric joints relies on subjective human statistics, and the number of natural fractures and joint orientations in underground rock masses cannot be observed.
[0028] Subsequent improvements and refinements to rock mass integrity evaluation indicators have been largely based on the three methods mentioned above, with varying degrees of modifications and improvements made to testing methods, calculation methods, and model establishment. Currently, the rock mass integrity coefficient is primarily used as one of the parameters in rock mass quality grading standards, participating in the assessment of rock mass quality. Existing quantitative characterization methods are mostly applied in civil engineering or water conservancy and hydropower industries to help analyze the integrity of slopes or tunnel rock masses; research on the degree of fragmentation in fractured strata of deep underground oil and gas reservoirs is relatively limited.
[0029] In summary, existing technologies for analyzing the degree of fracturing of fractured rocks suffer from problems such as large errors, long processing times, high costs, poor representativeness, and reliance on engineers' experience.
[0030] To address the aforementioned technical problems, this application provides a system for detecting the degree of fracture in fractured rock masses, such as... Figure 1 and Figure 2 As shown, it includes: a load application device 101, a laser 102, a coupler 103, a measurement fiber 104, and a fiber demodulation device 105.
[0031] The load application device 101 is used to apply pressure to the fractured core column 20, which is equipped with a measuring optical fiber 104.
[0032] The laser 102 and the fiber demodulation device 105 are connected to the measurement fiber 104 via the coupler 103. The laser emitted by the laser 102 is split into a first signal light and a second signal light by the coupler 103. The first signal light enters the measurement fiber 104 and the second signal light enters the fiber demodulation device 105. The measurement fiber 104 generates Rayleigh backscattered light, which enters the fiber demodulation device 105 through the coupler 103.
[0033] The fiber optic demodulation device 105 is used to obtain fiber optic strain data by demodulating the beat frequency signal formed by the Rayleigh backscattered light of the first signal light and the second signal light. The fiber optic strain data is used to determine the breakage index.
[0034] This embodiment applies pressure to a fractured rock core column using a load-applying device. By using a laser, a measuring optical fiber mounted on the core column, and a reference optical fiber, the surface field variation of the core column under external load can be monitored. The number of natural cracks is counted based on the fiber strain data, thereby obtaining the fracture index. This application does not require observation of the rock, effectively avoiding subjective errors caused by manual identification, and can identify tiny cracks that are difficult to detect by conventional methods. It provides an efficient and reliable technical path for the quantitative characterization of the degree of fracture of fractured rock masses.
[0035] In some embodiments, unlike jointed core columns which have relatively regular orientations, fractured core columns need to simulate the irregular and discontinuous fracture structure caused by high tectonic stress in underground fractured strata. Therefore, the commonly used fabrication methods such as wire cutting or cement powder injection in the preparation of jointed core columns will be difficult to apply.
[0036] Based on this, this application uses the following operation to prepare fractured core columns: cutting the rock obtained from the fractured block to obtain multiple standard core columns; according to different preset pump pressures, controlling the air pump to drive the impact pin to strike the top and side surfaces of different standard core columns to obtain fractured core columns with different degrees of fracture.
[0037] In some implementations, a natural homogeneous sandstone outcrop from a fractured area is selected. The selected sandstone is cut and processed into a standard homogeneous sandstone core column with dimensions of 38×76mm and no natural cracks on the surface. To simulate the fracturing of strata rocks underground due to intense tectonic movement and immense tectonic stress, a pneumatically driven impactor is used to apply a large instantaneous impact force to the top and sides of the standard core column, causing irregular fracturing. The pump pressure of the pneumatically driven impactor is adjusted to change the impactor speed and control the degree of fracturing of the core column. In one specific implementation, the pump pressure is set to 0.2MPa, 0.3MPa, 0.4MPa, and 0.5MPa to produce core columns with different degrees of fracturing.
[0038] In some embodiments, the measuring optical fiber is a distributed optical fiber, which features millimeter-level high spatial resolution, continuous distributed measurement, and high strain measurement accuracy. By monitoring the surface strain field of fractured rock mass under external load, the number of natural cracks is automatically counted based on the strain signal response, and the fracture index is calculated.
[0039] In some embodiments, the load application device is a high-temperature and high-pressure rock triaxial apparatus, which is a comprehensive rock stress testing system, mainly comprising eight system modules: a stress loading system, a confining pressure loading system, an axial and radial deformation measurement system, a servo control and data acquisition system, an ultrasonic and acoustic emission measurement system, a radial velocity anisotropy testing system, a differential strain testing system, and a high-temperature control and heat conduction system. The maximum axial dynamic pressure is 800 kN, meeting the requirements for evaluating the mechanical parameters and properties of rocks in deep high-temperature and high-pressure formations up to 7000 m.
[0040] The system can test and analyze parameters such as acoustic velocity, permeability, geostress, and mechanical strength of rock cores under high temperature and high pressure conditions, and can perform the following experiments: Displacement and strain experiments of rock cores under high temperature and high pressure conditions: dynamic uniaxial and triaxial experiments; P-wave and S-wave velocity tests; hydraulic fracturing experiments; differential strain tests; pore volume compression tests; heat conduction tests; rapid pulse decay permeability experiments and radial wave velocity anisotropy tests.
[0041] The system can also be upgraded with various accessories to perform a wide range of tests, including indirect tension, ultrasonic velocity, rock fracture toughness, true triaxial testing, acoustic emission, differential strain analysis, hydraulic fracturing, resistivity, direct tension, and permeability. The maximum loading temperature is 200℃ with an accuracy of 0.5℃; the maximum confining pressure is 140MPa, the maximum pore pressure is 140MPa with an accuracy of 0.1%FS; the maximum axial static pressure is 1500KN, the maximum axial dynamic pressure is 800KN with a testing accuracy of 0.15%FS; the maximum axial deformation is 5.0mm, the maximum radial deformation is 2.5mm with a measurement accuracy of 0.15%FS; and the maximum sample diameter is 54mm.
[0042] In some implementations, such as Figure 2 As shown, firstly, the measuring optical fiber 104 on the fractured core column 20 is disconnected from the optical fiber demodulation device 105. The fractured core column 20, with the measuring optical fiber 104 attached, is placed on the base in the middle of the high-temperature and high-pressure rock triaxial apparatus 201. After the measuring optical fiber 104 passes through the positioning ring below the displacement sensor on the base of the high-temperature and high-pressure rock triaxial apparatus 201, the positioning rings above and below the displacement sensor are fixed to the base below the fractured core column 20 and the pressure head above the fractured core column 20, respectively, to ensure uniform loading. After the fractured core column 20 is placed, the measuring optical fiber 104 is connected to the optical fiber demodulation device 105. Next, the loading and failure process begins: After the fractured core column 20 is positioned correctly, a pre-tightening process is first performed. In the high-temperature and high-pressure rock triaxial apparatus 201, a pressure of 0.1 MPa is used to advance the loading head until the loading head touches the fractured core column 20 and the core column does not shake, at which point the advancement is stopped. Then, the constant-speed loading mode in the high-temperature and high-pressure rock triaxial apparatus 201 is used to load until the fractured core column 20 is destroyed. At the moment the formal loading begins, the fiber optic demodulation device 105 synchronously records the fiber optic data until the fractured core column 20 yields and fails or the measuring fiber breaks prematurely, at which point the loading is stopped and the data is recorded.
[0043] In some embodiments, the fiber optic demodulation equipment employs a dynamic distributed fiber optic sensing system (OSI-D) based on optical frequency domain reflectance (OFDR) technology. This system can monitor the temperature in real time throughout the entire experimental process. The OSI-D includes a reference fiber, a reflector at the end of the reference fiber, a photodetector, and a demodulator. The spatial resolution of the measurement points can reach up to 0.64 mm, the temperature measurement accuracy reaches ±0.1℃, the strain measurement accuracy reaches ±1 με, and the sampling rate is 120 Hz. Combined with algorithms, real-time dynamic demodulation of the OFDR signal can be achieved.
[0044] OFDR is a coherent detection technique based on continuous frequency modulated light. It locates the scattered signal by measuring the frequency of Rayleigh backscattered light generated by the modulated probe light, achieving millimeter-level spatial resolution and extremely high sensing accuracy. The specific measurement process is as follows: A laser emits a linearly scanning continuous beam, which is split into two paths by a coupler. One beam serves as a reference beam, and the other as a probe beam, which is emitted into the fiber under test. As the probe beam propagates forward in the fiber, it continuously generates Rayleigh backscattered light. This Rayleigh backscattered light and the reflected reference light undergo beat frequency interference after passing through the coupler, generating a beat frequency signal, which is detected by a photodetector. The photodetector converts the beat frequency signal into an electrical signal, thereby obtaining the Rayleigh backscattered distribution information along the entire fiber under test. The demodulator then demodulates the Rayleigh backscattered light to obtain strain and temperature data. In some embodiments, to ensure that the measuring fiber can monitor natural cracks on the rock sample surface to the greatest extent, the measuring fiber is spirally wound around the surface of the core column from the measurement start point to the measurement end point. In practice, the measuring optical fiber is spirally wound upwards from the starting point at the bottom of the core column to the ending point at a preset angle, with the spiral winding angle being [value missing]. After the measurement fiber is laid out, it is fused together and connected to the fiber optic demodulation equipment for measurement. The measurement data is then transmitted from the fiber optic demodulation equipment to the computer for storage.
[0045] In some embodiments, the measuring optical fiber is bonded to the surface of the core column using α-cyanoacrylate adhesive.
[0046] In some embodiments, after the optical fiber to be measured is bonded to the surface of the core column using α-cyanoacrylate adhesive, a sealant is applied to the surface of the core column. Preferably, KE-441-T sealant is used. The sealant ensures that the optical fiber in the gaps is completely encapsulated, filling surface defects caused by collapse and fragmentation during the preparation of the fractured core column, and preventing the fiber from being cut by rigid displacement of the fragments under uniaxial loading. KE-441-T sealant is a one-component RTV flame-retardant electrical sealant that hardens by reacting with moisture in the air, producing oxime gas. It is a room-temperature curing condensation-reactive adhesive. It features fast curing speed, no shrinkage during curing, strong preservation, resistance to high and low temperatures (-50℃~250℃), non-corrosiveness, viscosity of 15 Pa·s, tensile strength of 1.7 MPa, elongation at break of 280%, surface curing time of 60 min, and tensile shear bond strength of 1 MPa. Its low viscosity and self-leveling properties allow it to easily flow and fill tiny cracks on the surface of fractured rock samples, effectively protecting optical fibers and simulating the cementation of geological rocks.
[0047] In one specific embodiment, such as Figure 3A and Figure 3B As shown, Figure 3A and Figure 3B A schematic diagram of the fiber optic winding scheme for measurement is shown, wherein, Figure 3A This is a frontal view diagram; the diagonal lines represent the schematic diagram of the measuring optical fiber wound around the core column. Figure 3A The horizontal axis represents the perimeter of the rock cross-section, the diameter of the core column cross-section is 38mm, and the vertical axis represents the height of the rock. Figure 3B For example, Figure 3B The medium-sized cylinder is a fractured core column, and sealant has been applied to the cracks on the surface of the fractured core column.
[0048] In some embodiments, the positions of the measuring optical fiber at the first and second measurement points on the core column are treated by burning with a heated metal rod. This embodiment is applied after the measuring optical fiber is connected to the signal demodulation equipment and the measurement signal is displayed normally. In some embodiments, the measurement start point (i.e., the first measurement point) is marked 10 mm from the lower end face of the core column surface; the measurement end point is marked 10 mm from the upper end face of the core column surface on the same vertical line as the measurement start point. The start point is used as the first measurement point, and the end point is used as the last measurement point. Multiple measurement points are set between the start point and the end point. After the burning treatment, the optical fiber demodulation equipment will detect obvious peak fluctuations at the corresponding measurement points, such as... Figure 4 The middle arrow points to the point where the first measurement point corresponds to the fluctuation. By recording the absolute spatial positions of the peak values at the first and second measurement points, the length and specific location of the fiber optic measurement segment can be obtained. This method can also be used to record the specific spatial positions of other required measurement points.
[0049] In some embodiments, the fracture degree detection system for fractured rock mass further includes: processing equipment.
[0050] like Figure 5 As shown, the processing equipment is used to determine the crushing parameters according to the following operations: Step 501: Preprocess the fiber strain data.
[0051] The fiber optic strain data includes strain data at various measurement points on the measuring fiber.
[0052] Step 502: Determine the strain field map on the surface of the core column based on the preprocessed fiber strain data.
[0053] The preprocessed fiber strain data includes the processed strain data of each measurement point on the measuring fiber.
[0054] Step 503: Use the peak-finding function to find the strain gradient point from the strain field diagram on the surface of the core column.
[0055] Step 504: Determine the number of natural cracks based on the strain gradient points.
[0056] Step 505: Calculate the breakage index based on the number of natural cracks.
[0057] The processing equipment can be integrated into the fiber optic demodulation equipment.
[0058] In some implementation sets, the strain field map of the core column surface is determined based on the preprocessed fiber strain data, including: (1) Based on the preprocessed fiber strain data, the axial strain data is obtained by decomposition. .
[0059] The fractured core column was loaded axially, so the strain field on its surface was significantly affected by axial stress. However, to comprehensively monitor the strain response on the core column surface, a measuring optical fiber was spirally wound around the surface. This spiral winding method ensured that the obtained fiber strain data included not only axial strain but also strain in other directions, specifically strain in six rock directions: axial strain, circumferential strain, radial strain, and three shear strains. Therefore, the fiber strain data needed to be decomposed to extract the axial strain component for analysis.
[0060] Distributed fiber optic strain monitoring technology, limited by its measurement principle, can only measure the tensile or compressive strain generated along the axial direction of the optical fiber under the influence of external environmental factors. In the experiment, the distributed measurement fiber was spirally wound onto the surface of a rock core column. Strain transfer losses caused by adhesives, sheaths, and other materials during the fiber bonding process were ignored. The fiber strain data measured under these conditions... Essentially, it reflects the deformation of the measurement points on the core column surface in different directions. Specifically, the strain state at any measurement point on the core column surface can be represented by the strain tensor. This means that, through coordinate transformation, the strain components of the measurement point in any direction in space can be calculated.
[0061] Let the unit direction vector along the fiber optic axis be... Then the fiber strain in that axial direction (i.e., fiber optic strain data) can be expressed as: (1) Right now: (2) (3) in, l , m , nLet be the direction cosine between the axis of the fiber differential segment and the coordinate axis. The above equation directly reflects the linear combination effect of the strain tensor along the fiber axis, without introducing additional geometric transformations. Compared to the traditional coordinate transformation method, this expression reveals its physical essence more concisely through tensor algebraic form: fiber optic strain measurement is essentially a linear combination of spatial strain states in a specific direction, with its weight determined by the direction cosine. This method not only simplifies the mathematical derivation but also strengthens the physical explanation of the strain transfer mechanism.
[0062] The core column was axisymmetric before failure, so fiber strain was analyzed in cylindrical coordinates. It was assumed that the core column was cylindrical before and after uniaxial loading, and that the rock was an ideally isotropic, elastic, homogeneous sandstone. Therefore, the fiber strain can be further derived as follows: (4) in, , , It is the helical tilt angle of the optical fiber winding. The circumferential strain of the core column measured by optical fiber, This represents the axial strain of the core column measured by the optical fiber.
[0063] Under uniaxial loading, the upper end face of the core column is always subjected to a uniformly distributed load. The function of the core column is as follows: the lower end face is a fixed bottom surface; the side surface of the core column is a free surface with zero surface force; body forces are negligible. The boundary conditions of the core column are determined accordingly.
[0064] Boundary conditions on the upper end face of the core column: (5) Boundary conditions at the lower end face of the core column: (6) Boundary conditions on the side of the core column: (7) Among the above boundary conditions, , , , , , This represents the normal stress and shear stress at each boundary.
[0065] l 1 indicates the outer normal of the boundary and x The spatial cosine between axes; l 2 indicates the outer normal of the boundary and y The spatial cosine between axes; l 3 indicates the outer normal of the boundary and z Spatial cosine between axes.
[0066] The above three boundary conditions are for uniaxial loading of the core. In actual implementation, if the core column is set under triaxial confining pressure or other conditions, the boundary conditions can be modified accordingly.
[0067] Under the above boundary conditions, solve the equilibrium equations and stress compatibility equations for the uniaxial loading process of the core.
[0068] The equilibrium equations are as follows: (8) The stress compatibility equation is as follows: (9) In the above formula, , , , , , This represents the normal stress and shear stress during uniaxial loading of rock.
[0069] The inverse solution method is used to solve the problem. Based on the uniqueness of the solution, if a solution is given that satisfies all the equations and the boundary conditions, then this solution is the unique solution to the basic problem.
[0070] Assumption , .
[0071] Here As an undetermined constant, substituting the above assumption into the equilibrium equation (Equation 8) and the stress compatibility equation (Equation 9) shows that it is always satisfied. Therefore, this assumption is the unique solution under this condition. Substituting the above values into the boundary conditions (Equations 5, 6, and 7) yields... Therefore, .
[0072] Therefore, the stress distribution of the core column under uniaxial loading is as follows: (10) Substituting equation (10) into the equilibrium equation (equation 8), stress compatibility equation (equation 9), and boundary conditions (equations 5, 6, and 7) all satisfy the conditions. The negative sign indicates that the direction of the variable is opposite to the positive direction of the coordinate axis.
[0073] The stress transformation relationship between cylindrical coordinates and rectangular coordinates is as follows: (11) In the above formula, , , , , , This represents the normal stress and shear stress of a core column under uniaxial loading in cylindrical coordinates. This indicates that the direction vector at a point in space is xy Projection on a plane and x The angle between axes.
[0074] The generalized Hooke's law in cylindrical coordinates is as follows: (12) In the above formula, E The elastic modulus of the core column. v is the Poisson's ratio of the core column.
[0075] At the same time, due to the axial symmetry of the cylindrical coordinate system, we have .
[0076] Substituting equation (10) into equations (11) and (12) yields the strain field in cylindrical coordinates, as shown below: ; ; ; .
[0077] Therefore, it can be obtained , v It is the Poisson's ratio of the loaded rock.
[0078] Will Substituting into equation (4), the axial strain of the core column measured by the optical fiber can be obtained as follows: ; By substituting the preprocessed fiber strain data into the above axial strain calculation formula, the axial strain data can be obtained, which can be used to better analyze the core surface strain response caused by uniaxial loading.
[0079] (2) Determine the strain field diagram on the surface of the core column based on the axial strain data.
[0080] Correspondingly, if the axial strain data is the axial strain data of the fractured core column during uniaxial loading, then the surface strain field diagram of the core column is the surface strain field diagram of the fractured core column during uniaxial loading.
[0081] A strain field diagram of the core column surface in a specific embodiment is shown below. Figure 6 As shown, Figure 6 The vertical axis represents the length of the fiber optic sensing section, and the horizontal axis represents the duration of the experiment. Figure 6 Different colors correspond to different strain values; the redder the color, the greater the strain, and the bluer the color, the smaller the strain. Figure 6It is known that the fracture region on the core column exhibits unique strain gradient characteristics. Based on this, this application proposes a strain gradient identification algorithm with dynamic threshold optimization, including: utilizing a peak-finding function... findpeaks The strain gradient points in the fiber optic strain data of the core column at each moment are automatically found from the strain field map on the surface of the core column. The number of strain gradient points is the number of natural cracks.
[0082] To accurately identify the number of all natural cracks, we established a threshold selection method based on the statistical characteristics of strain gradients, analyzing strain gradient amplitude, local signal-to-noise ratio, and crack spacing. The number of strain gradient points that meet the adaptive threshold is used as the direct basis for counting natural cracks, achieving fully automated and high-precision quantification of crack identification.
[0083] In one specific embodiment, the strain gradient search result is as follows: Figure 7 As shown, Figure 7 The middle trapezoid line indicates the number of cracks found. Among them, Figure 7 The vertical axis represents the number of cracks found, and the horizontal axis represents the time of the uniaxial loading experiment on the core column. Figure 7 For use findpeaks The diagram illustrates the process of using a peak-finding function to determine the number of natural fractures. The number of fractures found varies with loading time. Ultimately, the number of fractures in the core sample is considered to be the highest value throughout the entire loading process. Figure 7 The maximum value in.
[0084] In some embodiments, step 505 above calculates the fracturing index based on the number of natural cracks, including: The crushing index is calculated using the following formula: ; ; in, J v For breakage indicators, N The number of cracks L The length of the fiber optic measurement segment. findpeaks ( t ) represents the maximum number of natural cracks identified by the peak-finding function across all time steps in the entire uniaxial loading process.
[0085] In some embodiments, such as Figure 8 As shown, the preprocessing of fiber strain data includes: Step 801: Perform data thinning on the fiber strain data in the time dimension to obtain the first processed data.
[0086] The data volume of fiber optic strain data is enormous; in indoor experiments, the data volume generated in 10 minutes can reach 1GB for storage. To ensure automated and rapid crack identification and fracture index calculation, the fiber optic strain data needs to be reasonably diluted. Measurement points on the measuring fiber are distributed along its length; more measurement points can monitor more of the core surface. Therefore, spatial dilution of the fiber optic strain data should be avoided as much as possible to ensure the integrity of its spatial distribution. Uniaxial loading of a fractured core column is a constant-rate loading mode, so the fiber optic strain data has strong continuity in its temporal distribution. This embodiment chooses to thin the fiber optic strain data in the time dimension. Due to the continuity of fiber optic monitoring, the trend and accuracy of the fiber optic monitoring data are not disrupted. Because the data volume of the fiber optic strain data is reduced, the calculation efficiency of the fracture index can be improved while maintaining the accuracy of the calculation. For example, diluting the fiber optic strain data by 10 times optimizes the automatic calculation speed of the fracture index from 10 minutes to 30 seconds.
[0087] Step 802: Identify and adjust the abnormal sway strain values in the first processed data to obtain the second processed data.
[0088] During the loading process of the load application equipment, the measuring optical fiber wrapped around the surface of the fractured core column is prone to shaking, which will cause some measuring points on the fractured core column to generate abnormal strain values. This step is used to identify abnormal strain values caused by shaking.
[0089] In some implementations, the process of identifying abnormal sway strain values includes: (1) Calculate the median strain at adjacent time points at each measurement point on the fractured core column: ; in, i This indicates the measurement point number, where t and t+1 are adjacent time points. The strain value at measurement point i at time point t, Let be the strain value of measurement point i at time point t+1.
[0090] (2) Comparison of median strain and The error between the values and the preset threshold, when the strain median and When the error between the values is greater than a preset threshold, the strain value at measurement point i at time point t+1 is considered to be... This represents the abnormal strain value.
[0091] The preset threshold is, for example, 50%, when the median strain... and The error between the values exceeds 50%. ; That is, the measurement point is considered i At the point of time t +1 strain value For abnormal strain values, use Replace it.
[0092] In practice, the aforementioned preset threshold is an error range and can be set according to actual needs. When it is necessary to observe crack propagation, the preset threshold can be set to a larger range. When more attention is paid to the changes in the surface strain field during core loading, the preset threshold can be set to a smaller range.
[0093] Step 803: Perform noise reduction processing on the second processed data to obtain the third processed data.
[0094] When implementing this step, wavelet denoising can be used to denoise the second-processed data, thereby removing environmental noise and abnormal strain caused by fiber slippage during the loading process.
[0095] Some implementations also include verifying the noise reduction effect. Specifically, the wavelet noise reduction effect is evaluated using three parameters: the signal-to-noise ratio (SNR) before and after noise reduction, the energy percentage of the original signal after noise reduction (ESN), and the root mean square error (RMSE) between the original and denoised signals. If the noise reduction effect does not meet the requirements, the noise reduction parameters are modified and the noise reduction evaluation continues until the noise reduction effect meets the requirements.
[0096] SNR is defined as: ; in, x ( t ) is a noisy signal (i.e., the second processed signal). x ( t )' is the noise-reduced signal (i.e., the third processed signal). N This represents the number of sampling points. A higher signal-to-noise ratio (SNR) indicates that the signal contains more information about the actual microseismic signals, resulting in a better noise reduction effect.
[0097] ESN is defined as: ; in, E 'The energy of the signal after noise reduction' , E The total energy of the original signal. The larger the ESN value, the more the denoised signal retains the characteristics of the original signal and is closer to the original signal.
[0098] RMSE is defined as: ; in, Nis the vector length of the denoised data, and here it is the number of fiber optic measurement points. Root mean square error (RMSE) is a measure of the deviation of the denoised microseismic data from the average value of the original data. The smaller the RMS error, the closer the denoised signal is to the original signal, and the better the denoising effect.
[0099] Different wavelet denoising parameters (wavelet basis, noise estimation method, soft and hard threshold selection, threshold selection rule, wavelet decomposition level) are set. The final wavelet denoising parameters are then determined based on the signal-to-noise ratio (SNR), energy percentage (ESN), and original root mean square error (RMSE) obtained from these different parameters. The fiber optic strain data from each fractured core column requires denoising processing. The optimal wavelet denoising parameters differ for different fractured core columns and loading experiments.
[0100] Step 804: Filter the third processing data to obtain preprocessed fiber strain data.
[0101] When implementing this step, Gaussian smoothing filtering can be used to filter the third-processed data.
[0102] In some embodiments, a method for detecting the degree of fragmentation of fractured rock mass is also provided, applicable to the fractured rock mass detection system described in the foregoing embodiments, such as... Figure 9 As shown, the methods for detecting the degree of fracturing in fractured rock masses include: Step 901: The fractured core column equipped with the measuring optical fiber is placed on the load application device.
[0103] Step 902: Control the load application device to operate in a constant speed loading mode.
[0104] Step 903: Control the fiber demodulation device to analyze and record fiber strain data until the core column or the measuring fiber changes and then stop recording fiber strain data.
[0105] Step 904: Determine the breakage index based on the fiber strain data.
[0106] In some embodiments, step 904, determining the breakage index based on the fiber strain data, includes: The fiber strain data is preprocessed; Based on the preprocessed fiber strain data, the strain field diagram on the surface of the core column was determined. The strain gradient points are found from the strain field diagram on the surface of the core column using a peak-finding function. The number of natural cracks is determined based on the strain gradient points. The breakage index is calculated based on the number of natural cracks.
[0107] The preprocessing of the fiber strain data includes: The fiber strain data is thinned out over time to obtain the first processed data. Identify and adjust the abnormal sway strain values in the first processed data to obtain the second processed data; The second processed data is subjected to noise reduction processing to obtain the third processed data; The third processed data is filtered to obtain preprocessed fiber strain data.
[0108] Among them, based on the preprocessed fiber strain data, the strain field map of the core column surface is determined, including: Based on the preprocessed fiber strain data, the axial strain data is obtained by decomposition. Based on the axial strain data, the strain field diagram on the surface of the core column was determined.
[0109] The fracture index is calculated based on the number of natural cracks, including: The crushing index is calculated using the following formula: ; in, J v For breakage indicators, N The number of cracks L This represents the length of the fiber optic measurement segment.
[0110] This embodiment applies pressure to a fractured rock core column using a load-applying device. By using a laser, a measuring optical fiber mounted on the core column, and a reference optical fiber, the surface field variation of the core column under external load can be monitored. The number of natural cracks is counted based on the fiber strain data, thereby obtaining the fracture index. This application does not require observation of the rock, effectively avoiding subjective errors caused by manual identification, and can identify tiny cracks that are difficult to detect by conventional methods. It provides an efficient and reliable technical path for the quantitative characterization of the degree of fracture of fractured rock masses.
[0111] To more clearly illustrate the technical solution of this application, a specific embodiment is provided below for detailed description. The automatic measurement method for the degree of fracture of fractured rock mass based on fiber optic response includes the following steps: Step 1: Prepare a fractured core column for which fracture parameters need to be measured. The core column must meet the standard core column specifications recommended by the International Society for Rock Mechanics and Rock Engineering (ISRM).
[0112] Removing gravel from the surface of the core column does not affect the bonding of the measuring optical fiber. In this embodiment, an artificially prepared fractured core column is used, and the fragments inside the fractured core column are tightly bonded together using α-cyanoacrylate adhesive to simulate its cementation state underground.
[0113] Step 2: Mark the start and end points of the measurement on the core column. Position the measuring fiber at a preset angle (e.g., ...). The optical fiber is spirally wound upwards from the measurement start point at the bottom of the core column to the measurement end point, for a total of 4 turns. After bonding the optical fiber to the core column surface using α-cyanoacrylate adhesive and allowing the adhesive to cure, KE-441-T sealant is applied to natural cracks on the core column surface, ensuring that the optical fiber in the gaps is completely encapsulated by the sealant. This prevents the optical fiber in the gaps from being cut during loading. Figure 3B As shown.
[0114] Step 3: Set the parameters of the fiber optic signal demodulation equipment, and set the spatial resolution of the measurement fiber to 0.64mm to ensure that the response of the measurement fiber at the natural crack is monitored to the greatest extent possible.
[0115] Step 4: Calibrate the measuring points of the measuring fiber. Connect the measuring fiber wound around the core column to the signal demodulation equipment. After the measurement signal displays normally, touch the corresponding measuring points of the measuring fiber with a high-temperature heated metal rod to determine the fiber length at the measuring point location. The measuring points include the fiber winding start point, end point, and locations of significant natural cracks, etc., to facilitate comparison and determination of the location of natural cracks in subsequent data processing. Figure 4 As shown.
[0116] Step 5: Disconnect the measuring fiber from the signal demodulation equipment. Place the fractured core column with the measuring fiber attached into the high-temperature, high-pressure rock triaxial apparatus. After the measuring fiber passes through the displacement sensor chassis, place the displacement sensor, ensuring uniform loading. After the core column is placed, connect the measuring fiber to the signal demodulation equipment, such as... Figure 2 As shown.
[0117] Step Six: After aligning the core column, the pre-tightening process is initiated. Using a high-temperature, high-pressure rock triaxial apparatus, a pressure of 0.1 MPa is applied to advance the loading head until it touches the core column and the core column shows no movement; then, advancement is stopped. Subsequently, the constant-rate loading mode of the high-temperature, high-pressure rock triaxial apparatus is used to load the core column until it fails. Fiber optic strain data is recorded simultaneously at the moment loading begins, continuing until the fractured core column yields and fails or the fiber optic cable breaks prematurely; at this point, loading is stopped and data is recorded.
[0118] Step 7: Read the fiber optic strain data and remove abnormal strain values caused by fiber optic swaying due to loading. Calculate the median strain at adjacent time points for each measuring point: ; in, i Indicates the measurement point number.
[0119] When the strain median and The error between the values exceeds 50%. ; That is to say, the first i Each measuring point t Strain value at time +1 For abnormal strain, use Replace it.
[0120] Subsequently, wavelet threshold denoising was used to remove noise from the fiber strain signal. The denoising formula is shown below: ; in, W ( a , b ) are wavelet transform coefficients. f ( t () represents the original time-domain signal. For wavelet basis functions, a As a scale factor, b The translation factor is... j This represents the number of decomposition layers.
[0121] In this example, the Symlet wavelet basis is used, and the noise estimation method uses signal length normalization (sln), soft thresholding (s), tentative Stein unbiased risk estimation (heursure) threshold selection rule, and the wavelet decomposition level is 17.
[0122] Gaussian smoothing filtering was applied to the fiber strain data after wavelet denoising to remove abnormal strain caused by fiber slippage during loading.
[0123] ; in, The kernel standard deviation determines the smoothing strength. x For spatial or temporal variables, kernel window length L =2 M +1, M The window width is half the window width. In this example, the window width for Gaussian smoothing filtering is 500.
[0124] Step 8: Calculate the fiber strain based on the formula for decomposing the axial strain of the rock measured by the optical fiber to obtain the axial strain of the rock core. The formula is as follows: ; Step Nine: Based on the fiber optic axial strain data, plot the strain field diagram on the surface of the fractured core column during uniaxial loading. Analysis revealed a significant gradient in the strain signal at the natural cracks in the diagram (e.g., Figure 6(As shown). The peak-finding function `findpeaks` is used to automatically find strain gradient points in the fiber optic strain data of the core column at each time step. The number of strain gradient points is the number of natural cracks.
[0125] Step 10: Calculate the crushing index J v .
[0126] ; in, L The length of the fiber optic measurement segment; N = max ( findpeaks ( t )) represents the maximum number of cracks found by the peak-finding function in the entire spatiotemporal fiber strain data matrix.
[0127] This application involves preparing sandstone cores with varying degrees of fragmentation and conducting uniaxial loading experiments on these cores using fiber optic monitoring. The fiber optic cable is deployed on the surface of the core, and the evolution of the strain field on the core surface is monitored in real time during the application of external loads. When the loading induces the closure of natural cracks within the core and the displacement of the fractured body, this will manifest as a sudden change in local strain in the fiber optic strain signal. Due to the high spatial resolution and high precision of the fiber optic cable, real-time monitoring of the continuous strain field on the core surface is possible, allowing for the identification and automatic counting of cracks without direct observation of the fractured structure. This enables automated and quantitative characterization of the degree of fragmentation in the core and the calculation of fracture indices. This application not only effectively avoids the subjective errors inherent in traditional manual crack counting but also possesses the ability to identify minute surface cracks, making it particularly suitable for scenarios where natural cracks in fractured rock columns are fine, complexly distributed, and difficult to observe.
[0128] This application also provides a computer device for calculating crushing indicators. For example... Figure 10As shown, computer device 1002 may include one or more processors 1004, such as one or more central processing units (CPUs), each of which may implement one or more hardware threads. Computer device 1002 may also include any memory 1006 for storing information of any kind, such as code, settings, data, etc. Non-limitingly, for example, memory 1006 may include any type of RAM, any type of ROM, flash memory, hard disk, optical disk, etc. More generally, any memory can use any technology to store information. Furthermore, any memory may provide volatile or non-volatile retention of information. Furthermore, any memory may represent a fixed or removable component of computer device 1002. In one case, when processor 1004 executes associated instructions stored in any memory or combination of memories, computer device 1002 may perform any operation of the associated instructions. Computer device 1002 also includes one or more drive mechanisms 1008 for interacting with any memory, such as hard disk drive mechanisms, optical disk drive mechanisms, etc.
[0129] Computer device 1002 may further include an input / output module 1010 (I / O) for receiving various inputs (via input device 1012) and providing various outputs (via output device 1014). A specific output mechanism may include a presentation device 1016 and an associated graphical user interface (GUI) 1018. In other embodiments, the input / output module 1010 (I / O), input device 1012, and output device 1014 may be omitted, and the device may function solely as a computer device within a network. Computer device 1002 may also include one or more network interfaces 1020 for exchanging data with other devices via one or more communication links 1022. One or more communication buses 1024 couple the components described above together.
[0130] The communication link 1022 can be implemented in any way, such as via a local area network, a wide area network (e.g., the Internet), a point-to-point connection, or any combination thereof. The communication link 1022 may include any combination of hardwired links, wireless links, routers, gateway functions, name servers, etc., governed by any protocol or combination of protocols.
[0131] This application also provides a computer-readable storage medium, such as a non-transient computer-readable storage medium, on which a computer program is stored, and which, when run by a processor, performs the steps of the above-described method.
[0132] This application also provides a computer-readable instruction, wherein when a processor executes the instruction, the program therein causes the processor to perform the method shown in any of the foregoing embodiments.
[0133] It should be understood that in the various embodiments of this application, the order of the above-mentioned processes does not imply the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of this application.
[0134] It should also be understood that, in the embodiments of this application, the term "and / or" is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, and B existing alone. Additionally, the character " / " in this application generally indicates that the preceding and following related objects have an "or" relationship.
[0135] Those skilled in the art will recognize that the units and algorithm steps of the various examples described in conjunction with the embodiments disclosed in this application can be implemented in electronic hardware, computer software, or a combination of both. To clearly illustrate the interchangeability of hardware and software, the composition and steps of each example have been generally described in terms of functionality in the foregoing description. Whether these functions are implemented in hardware or software depends on the specific application and design constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementation should not be considered beyond the scope of this application.
[0136] Those skilled in the art will clearly understand that, for the sake of convenience and brevity, the specific working processes of the systems, devices, and units described above can be referred to the corresponding processes in the foregoing method embodiments, and will not be repeated here.
[0137] In the embodiments provided in this application, it should be understood that the disclosed systems, apparatuses, and methods can be implemented in other ways. For example, the apparatus embodiments described above are merely illustrative; for instance, the division of units is only a logical functional division, and in actual implementation, there may be other division methods. For example, multiple units or components may be combined or integrated into another system, or some features may be ignored or not executed. Furthermore, the couplings or direct couplings or communication connections shown or discussed may be indirect couplings or communication connections through some interfaces, apparatuses, or units, or they may be electrical, mechanical, or other forms of connection.
[0138] The units described as separate components may or may not be physically separate. The components shown as units may or may not be physical units; that is, they may be located in one place or distributed across multiple network units. Some or all of the units can be selected to achieve the purpose of the embodiments of this application, depending on actual needs.
[0139] Furthermore, the functional units in the various embodiments of this application can be integrated into one processing unit, or each unit can exist physically separately, or two or more units can be integrated into one unit. The integrated unit can be implemented in hardware or as a software functional unit.
[0140] If the integrated unit is implemented as a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of this application, in essence, or the part that contributes to the prior art, or all or part of the technical solution, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute all or part of the steps of the methods described in the various embodiments of this application. The aforementioned storage medium includes various media capable of storing program code, such as USB flash drives, portable hard drives, read-only memory (ROM), random access memory (RAM), magnetic disks, or optical disks.
[0141] This application uses specific embodiments to illustrate the principles and implementation methods of this application. The description of the above embodiments is only for the purpose of helping to understand the method and core ideas of this application. At the same time, for those skilled in the art, there will be changes in the specific implementation methods and application scope based on the ideas of this application. Therefore, the content of this specification should not be construed as a limitation of this application.
Claims
1. A system for detecting the degree of fracture in fractured rock masses, characterized in that, include: Load application equipment, laser, coupler, measurement fiber, fiber demodulation equipment; The load application device is used to apply pressure to a fractured core column, which is equipped with a measuring optical fiber. The laser and fiber demodulation device are connected to the measurement fiber via a coupler. The laser emitted by the laser is split into a first signal light and a second signal light by the coupler. The first signal light enters the measurement fiber, and the second signal light enters the fiber demodulation device. The measurement fiber generates Rayleigh backscattered light, which enters the fiber demodulation device through the coupler. The fiber demodulation device is used to obtain fiber strain data by demodulating the beat frequency signal formed by the Rayleigh backscattered light of the first signal light and the second signal light. The fiber strain data is used to determine the breakage index.
2. The system as described in claim 1, characterized in that, The measuring optical fiber is spirally wound around the surface of the fractured core column from the measurement starting point until it reaches the measurement termination point of the fractured core column.
3. The system as described in claim 1, characterized in that, The measuring optical fiber is heated at the first and second measuring points of the fractured core column using a heated metal rod.
4. The system as described in claim 1, characterized in that, The measuring optical fiber is bonded to the surface of the fractured core column via ethyl α-cyanoacrylate.
5. The system as described in claim 4, characterized in that, The surface of the fractured core column is coated with sealant.
6. The system as described in claim 5, characterized in that, The sealant includes KE-441-T adhesive.
7. The system as described in claim 1, characterized in that, The system also includes: a processing device; The processing equipment is used to determine the crushing parameters according to the following operations: The fiber strain data is preprocessed; Based on the preprocessed fiber strain data, the strain field diagram on the surface of the core column was determined. The strain gradient points are found from the strain field diagram on the surface of the core column using a peak-finding function. The number of cracks is determined based on the strain gradient points; Calculate the breakage index based on the number of cracks.
8. A method for detecting the degree of fracture in fractured rock masses, characterized in that, The method, applicable to any one of claims 1 to 7, comprises: A fractured core column equipped with a measuring optical fiber is placed on the load application device; The load application device is controlled to operate in a constant-speed loading mode; The fiber optic demodulation device is controlled to analyze and record fiber optic strain data until the fractured core column or the measuring fiber changes, at which point the recording of fiber optic strain data stops. Based on the fiber strain data, the breakage index is determined.
9. The method as described in claim 8, characterized in that, Based on the fiber strain data, the breakage index is determined, including: The fiber strain data is preprocessed; Based on the preprocessed fiber strain data, the strain field diagram on the surface of the core column was determined. The strain gradient points are found from the strain field diagram on the surface of the core column using a peak-finding function. The number of natural cracks is determined based on the strain gradient points. The breakage index is calculated based on the number of natural cracks.
10. The method as described in claim 9, characterized in that, The fiber strain data is preprocessed, including: The fiber strain data is thinned out over time to obtain the first processed data. Identify and adjust the abnormal sway strain values in the first processed data to obtain the second processed data; The second processed data is subjected to noise reduction processing to obtain the third processed data; The third processed data is filtered to obtain preprocessed fiber strain data.
11. The method as described in claim 9, characterized in that, Based on the preprocessed fiber strain data, the strain field map of the core column surface was determined, including: Based on the preprocessed fiber strain data, the axial strain data is obtained by decomposition. Based on the axial strain data, the strain field diagram on the surface of the core column was determined.
12. The method as described in claim 9, characterized in that, Based on the number of natural cracks, the fracturing index is calculated, including: The crushing index is calculated using the following formula: ； in, J v For breakage indicators, N The number of cracks L This represents the length of the fiber optic measurement segment.
13. The method as described in claim 9, characterized in that, The method further includes: The fractured core column was prepared using the following steps: The rock obtained by cutting the fractured blocks yielded multiple standard core columns; By controlling the air pump with different preset pump pressures, the impact pin is driven to strike the top and side surfaces of different standard core columns, resulting in core columns with different degrees of fragmentation.