Grouting type hollow interlayer multi-string anchor rod axial force meter

Abstract

The invention relates to the technical field of anchoring measurement, in particular to a grouting type hollow interlayer multi-string anchor rod axial force meter which comprises an anchor head, a plurality of through anchor rods and steel bar meters distributed between every two adjacent through anchor rods. The steel bar meter comprises a connecting sleeve, a cable is fixed to the outer portion of the connecting sleeve in a sealed mode, and a coil connected with the cable is connected to the inner wall of the connecting sleeve in an embedded mode. The interior of the through anchor rod is designed to be of a through structure, and threaded openings are formed in the outer portions of the two ends of the through anchor rod. Threaded openings matched with the through anchor rods are formed in the two ends of the interior of the connecting sleeve in the steel bar meter, and the steel bar meter is in threaded connection with the through anchor rods through the threaded openings. The anchor head is in threaded connection with the interior of one end of the through anchor rod, and the interior of one end of the through anchor rod is in threaded connection with a fastening nut. The installation structure of the anchor rod and the reinforcement meter is simple and convenient, a user can select and install the anchor rod and the reinforcement meter conveniently according to specific use conditions, and the high-efficiency construction measurement requirement is met.

Description

Technical Field

[0001] The invention relates to the technical field of anchoring measurement, in particular to a grouting-capable hollow sandwich multi-chord anchor axial force meter. Background Art

[0002] Anchor rods are the most basic component of tunnel support in modern coal mines. In the fields of underground engineering and slope engineering, anchor rod support is the most widely used reinforcement technology. Due to the different characteristics of the rock mass at different depths around the tunnel and the different stress environments, it is easy to produce uncoordinated deformation. Therefore, when using anchor rods, nuts need to be used to pre-tighten the anchor rods to prevent the nuts from loosening due to deformation of the surrounding rock and causing support failure.

[0003] Commonly used anchor stress gauges in China mainly include hydraulic, vibrating wire and strain gauges;

[0004] The working principle of the vibrating wire dynamometer is that when the stress inside the measured structure changes, the strain gauge synchronously senses the deformation, and the deformation is transmitted to the vibrating wire through the front and rear end seats and converted into a change in the stress of the vibrating wire, thereby changing the vibration frequency of the vibrating wire. The electromagnetic coil excites the vibrating wire and measures its vibration frequency. The frequency signal is transmitted to the reading device via a cable, and the strain inside the measured structure can be measured. This type of strain gauge is usually placed in the middle of the measured anchor rod or tied to the measured anchor rod. The installation process is relatively cumbersome, and the anchor rod axial force is easily disturbed by external factors during the subsequent monitoring process, resulting in inaccurate measurement data.

[0005] Therefore, a grouting type hollow sandwich multi-chord anchor axial force meter is proposed. Summary of the invention

[0006] The object of the present invention is to provide a groutable hollow sandwich multi-chord anchor axial force meter to solve the problems raised in the above background technology.

[0007] To achieve the above object, the present invention provides the following technical solutions: a groutable hollow sandwich multi-chord anchor axial force meter, comprising an anchor head, a plurality of through-hole anchors and a steel bar meter distributed between two adjacent through-hole anchors;

[0008] The steel bar meter comprises a connecting sleeve, and a cable is sealed and fixed on the outside of the connecting sleeve, and a coil connected to the cable is embedded in the inner wall of the connecting sleeve;

[0009] The through-type anchor rod has a through-type structure design inside, and thread openings are provided on the outside of both ends of the through-type anchor rod;

[0010] The connecting sleeve in the rebar gauge has threaded openings at both ends matching the through-type anchor rod, and the rebar gauge is threadedly connected to the through-type anchor rod through the threaded openings;

[0011] The anchor head is connected with the inner thread of one end of the through anchor rod, the inner thread of one end of the through anchor rod is threadedly connected with a fastening nut, and a bottom pad is sleeved between the fastening nut and the through anchor rod.

[0012] A method for using a groutable hollow sandwich multi-chord anchor axial force meter specifically comprises the following steps:

[0013] S1. Anchor bolt axial force meter is composed of multiple steel bar meters and cylindrical steel bar measuring rods with threaded ends at both ends. The ends of the anchor bolt are connected to the steel bar meters by a shorter steel bar measuring rod with a threaded end. The length of the wire at each measuring point of the anchor bolt is different.

[0014] S2. Drill holes at the installation location with a hole diameter of 50mm-60mm. Determine the hole depth according to the design plan. The deepest measuring point in the hole is N. The length of the wire to each measuring point at the hole mouth is N--(N+1)--(N+2)--(N+3)--(N+4);

[0015] S3. After assembling the anchor rod, check each joint to make sure it is tightly connected, and install it into the drilling measuring point hole. The hole diameter is 55mm, and the hole depth is based on the length of the anchor rod plus 10 centimeters. Grouting is performed. The grouting depth should include all sensors. Finally, use anchoring agent to seal it.

[0016] S4. Collect and measure data through the anchor axial force meter measurement system, and detect the stress condition of the anchor axial force meter in the project.

[0017] Preferably, the anchor axial force meter measurement system comprises:

[0018] Sensor unit: used to detect the strain, displacement or pressure of the anchor rod. The sensor includes a resistance strain gauge, a fiber grating sensor and a piezoelectric sensor;

[0019] Signal acquisition unit: converts the analog signal collected by the sensor into a digital signal and transmits it to the data processing unit. The signal acquisition unit usually includes a signal conditioning circuit and an analog-to-digital converter;

[0020] Data processing unit: processes and analyzes the collected signals and calculates the axial force value of the anchor. This unit can be embedded in the control system or processed through cloud computing;

[0021] Display and storage unit: used to display measurement results in real time and store historical data for further analysis.

[0022] Preferably, the specific use steps of the anchor axial force meter measurement system are as follows:

[0023] Step 1: The built-in sensor of the steel bar meter transmits data and feedback to the axial force meter measurement system through cables, and adopts a multi-point monitoring method for data acquisition and integrated analysis;

[0024] Step 2: Signal acquisition and signal conditioning: The analog signal output by the sensor is amplified and filtered through the signal conditioning circuit to remove interference signals and ensure the accuracy of the signal;

[0025] Data acquisition: convert the processed analog signal into a digital signal through an analog-to-digital converter and transmit the data to the data processing unit;

[0026] Step 3: Data processing and calculation, strain-axial force conversion: according to the type of sensor and calibration curve, the strain or displacement signal is converted into the axial force value;

[0027] F=K·∈

[0028] Where F is the axial force, K is the calibration coefficient of the sensor, and ∈ is the measured strain value;

[0029] Error correction: Considering the influence of environmental factors such as temperature and humidity, the measurement value is corrected through compensation algorithm to further improve the measurement accuracy;

[0030] Data analysis: Compare the calculated axial force data with the design value, analyze the stress state of the anchor rod, and determine whether there is any abnormality

[0031] Step 4: Data display and storage: The axial force data of the anchor bolt is displayed in real time on the display screen or computer interface to facilitate monitoring by operators, and the historical measurement data is stored in a local or cloud database for subsequent analysis and engineering evaluation.

[0032] Preferably, the resistance strain gauge method:

[0033]

[0034] Among them: F is the axial force of the anchor, E is the elastic modulus of the anchor material, A is the cross-sectional area of ​​the anchor, ∈ is the strain value, ν is the Poisson's ratio;

[0035] Fiber Bragg grating method:

[0036] F=K g ·Δλ

[0037] Where: K g Calibration coefficient of fiber Bragg grating, Δλ wavelength offset;

[0038] Temperature compensation algorithm formula:

[0039] F corr =F-α·ΔT

[0040] Among them: F corr Axial force after temperature compensation, α temperature compensation coefficient, ΔT temperature change.

[0041] Preferably, the strain data of the anchor rod at different positions are collected by arranging multiple sensors, and the data are fused by weighted averaging and interpolation algorithms;

[0042] Weighted average method: N sensors are installed at different positions of the anchor, and the strain data collected are ∈ 1 ,∈ 2 , ...,∈ n , then the overall strain ∈ can be calculated by weighted average method avg :

[0043]

[0044] where w i , is the weight of sensor i, which is set according to the location of the sensor and the importance of the measurement;

[0045] Interpolation algorithm: The distribution of sensors is sparse, and interpolation algorithms, such as linear interpolation or spline interpolation, are used to estimate the strain values ​​at other locations of the anchor rod and then calculate the overall axial force.

[0046] Preferably, according to the material mechanics theory, the relationship between the axial force F and the strain ∈ can be expressed by Hooke's law:

[0047] F=E·A·∈ avg

[0048] Where: E is the elastic modulus of the anchor material, A is the cross-sectional area of ​​the anchor, ∈ avg is the overall strain after integrated analysis,

[0049] Preferably, in order to ensure the accuracy of the measurement data, a Z-score outlier detection algorithm is introduced to detect and process outliers;

[0050] score anomaly detection: For each measurement point ∈ i , calculate its Z-score:

[0051]

[0052] Where μ is the mean value of strain data, σ is the standard deviation, when Z i When it exceeds a certain threshold (such as 3), it is considered that ∈ i These are outliers and need to be removed or corrected.

[0053] Compared with the prior art, the present invention has the following beneficial effects:

[0054] 1. The installation structure of the anchor rod and the steel bar meter in this application is simple and convenient, which is convenient for users to choose installation according to specific usage conditions and achieve efficient construction measurement needs;

[0055] 2. This application can achieve accurate measurement and dynamic monitoring of the anchor axial force, providing reliable data support for the safety of engineering structures. The system has the advantages of high precision, automation, and remote monitoring, and is suitable for all types of engineering projects that require anchor monitoring. BRIEF DESCRIPTION OF THE DRAWINGS

[0056] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0057] Figure 1 It is the overall structural view of the present invention;

[0058] Figure 2 It is a structural view of the anchor head and the through anchor rod of the present invention;

[0059] Figure 3 It is a structural view of the through anchor rod and the steel bar meter of the present invention;

[0060] Figure 4 It is the measuring point table of the anchor axial force meter of the present invention;

[0061] Figure 5 This is a structural view of the anchor rod axial force meter and the axial force hole of the present invention.

[0062] Description of reference numerals:

[0063] 1. Anchor head; 2. Middle anchor rod; 3. Rebar gauge; 31. Connecting sleeve; 32. Cable; 33. Connecting coil; 4. Fastening nut; 5. Bottom pad. DETAILED DESCRIPTION

[0064] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0065] See also Figures 1 to 5 , the present invention provides a technical solution:

[0066] A groutable hollow sandwich multi-chord anchor axial force gauge, comprising an anchor head 1, a plurality of through-hole anchors 2, and a steel bar gauge 3 distributed between two adjacent through-hole anchors;

[0067] The steel bar meter 3 comprises a connecting sleeve 31, and a cable 32 is sealed and fixed to the outside of the connecting sleeve 31, and a connecting coil 33 connected to the cable is embedded in the inner wall of the connecting sleeve 31;

[0068] The through-hole anchor rod 2 has a through-hole structure design, and thread openings are provided on both ends of the through-hole anchor rod 2.

[0069] The connecting sleeve 31 in the steel bar gauge 3 has threaded openings at both ends thereof that match the through anchor rod 2, and the steel bar gauge 3 is threadedly connected to the through anchor rod 2 through the threaded openings;

[0070] The anchor head 1 is connected to one end of the through anchor rod 2 through internal threads, one end of the through anchor rod 2 is threadedly connected to a fastening nut 4 through internal threads, and a bottom pad 5 is sleeved between the fastening nut 4 and the through anchor rod 2.

[0071] A method for using a groutable hollow sandwich multi-chord anchor axial force meter specifically comprises the following steps:

[0072] S1. Anchor bolt axial force meter is composed of multiple steel bar meters and cylindrical steel bar measuring rods with threaded ends at both ends. The ends of the anchor bolt are connected to the steel bar meters by a shorter steel bar measuring rod with a threaded end. The length of the wire at each measuring point of the anchor bolt is different.

[0073] S2. Drill holes at the installation location with a hole diameter of 50mm-60mm. Determine the hole depth according to the design plan. The deepest measuring point in the hole is N. The length of the wire to each measuring point at the hole mouth is N--(N+1)--(N+2)--(N+3)--(N+4);

[0074] S3. After assembling the anchor rod, check each joint to make sure it is tightly connected, and install it into the drilling measuring point hole. The hole diameter is 55mm, and the hole depth is based on the length of the anchor rod plus 10 centimeters. Grouting is performed. The grouting depth should include all sensors. Finally, use anchoring agent to seal it.

[0075] S4. Collect and measure data through the anchor axial force meter measurement system, and detect the stress condition of the anchor axial force meter in the project.

[0076] Specifically, the anchor axial force meter measurement system includes:

[0077] Sensor unit: used to detect the strain, displacement or pressure of the anchor rod. The sensor includes a resistance strain gauge, a fiber grating sensor and a piezoelectric sensor;

[0078] Signal acquisition unit: converts the analog signal collected by the sensor into a digital signal and transmits it to the data processing unit. The signal acquisition unit usually includes a signal conditioning circuit and an analog-to-digital converter;

[0079] Data processing unit: processes and analyzes the collected signals and calculates the axial force value of the anchor. This unit can be embedded in the control system or processed through cloud computing;

[0080] Display and storage unit: used to display measurement results in real time and store historical data for further analysis.

[0081] Specifically, the specific steps of using the anchor axial force meter measurement system are as follows:

[0082] Step 1: The built-in sensor of the steel bar meter transmits data and feedback to the axial force meter measurement system through cables, and adopts a multi-point monitoring method for data acquisition and integrated analysis;

[0083] Step 2: Signal acquisition and signal conditioning: The analog signal output by the sensor is amplified and filtered through the signal conditioning circuit to remove interference signals and ensure the accuracy of the signal;

[0084] Data acquisition: convert the processed analog signal into a digital signal through an analog-to-digital converter and transmit the data to the data processing unit;

[0085] Step 3: Data processing and calculation, strain-axial force conversion: according to the type of sensor and calibration curve, the strain or displacement signal is converted into the axial force value;

[0086] F=K·∈

[0087] Where F is the axial force, K is the calibration coefficient of the sensor, and ∈ is the measured strain value;

[0088] Error correction: Considering the influence of environmental factors such as temperature and humidity, the measurement value is corrected through compensation algorithm to further improve the measurement accuracy;

[0089] Data analysis: Compare the calculated axial force data with the design value, analyze the stress state of the anchor rod, and determine whether there is any abnormality

[0090] Step 4: Data display and storage: The axial force data of the anchor bolt is displayed in real time on the display screen or computer interface to facilitate monitoring by operators, and the historical measurement data is stored in a local or cloud database for subsequent analysis and engineering evaluation.

[0091] Specifically, the resistance strain gauge method:

[0092]

[0093] Among them: F is the axial force of the anchor, E is the elastic modulus of the anchor material, A is the cross-sectional area of ​​the anchor, ∈ is the strain value, ν is the Poisson's ratio;

[0094] Fiber Bragg grating method:

[0095] F=Kg ·Δλ

[0096] Where: K g Calibration coefficient of fiber Bragg grating, Δλ wavelength offset;

[0097] Temperature compensation algorithm formula:

[0098] F corr =F-α·ΔT

[0099] Among them: F corr Axial force after temperature compensation, α temperature compensation coefficient, ΔT temperature change.

[0100] Specifically, the strain data of the anchor rod at different positions are collected by arranging multiple sensors, and the weighted average and interpolation algorithms are used to fuse the data;

[0101] Weighted average method: N sensors are installed at different positions of the anchor, and the strain data collected are ∈ 1 ,∈ 2 , ...,∈ n , then the overall strain ∈ can be calculated by weighted average method avg :

[0102]

[0103] where w i , is the weight of sensor i, which is set according to the location of the sensor and the importance of the measurement;

[0104] Interpolation algorithm: The distribution of sensors is sparse, and interpolation algorithms, such as linear interpolation or spline interpolation, are used to estimate the strain values ​​at other locations of the anchor rod and then calculate the overall axial force.

[0105] Specifically, according to the theory of material mechanics, the relationship between the axial force F and the strain ∈ can be expressed by Hooke's law:

[0106] F=E·A·∈ avg

[0107] Where: E is the elastic modulus of the anchor material, A is the cross-sectional area of ​​the anchor, ∈ avg is the overall strain after integrated analysis,

[0108] Specifically, in order to ensure the accuracy of the measurement data, the Z-score outlier detection algorithm is introduced to detect and process outliers;

[0109] score anomaly detection: For each measurement point ∈ i , calculate its Z-score:

[0110]

[0111] Where μ is the mean value of strain data, σ is the standard deviation, when Z i When it exceeds a certain threshold (such as 3), it is considered that ∈ i These are outliers and need to be removed or corrected.

[0112] Assuming that three sensors are installed on the anchor rod, the strain data collected is 1 =1000μ, 2 =1050μ, 3 =980μ, and the weights are w 1 =0.3, w 2 =0.4, w 3 =0.3.

[0113] Calculate the overall strain ∈ avg :

[0114]

[0115] Calculate the axial force F:

[0116] Assuming that the material elastic modulus of the anchor rod is E = 200 GPa and the cross-sectional area is A = 0.01 m2, then:

[0117] F = 200 × 10 9 ×0.01×1014×10 -6 =2.028×10 6 N=2028kN

[0118] Anomaly detection and processing:

[0119] Assuming that the calculated strain mean μ=1014μ∈ and standard deviation σ=28.86μ∈, then for the Z-score of sensor 1:

[0120]

[0121] If the Z-score is less than or greater than the set threshold, it is determined to be an outlier and can be selected for elimination or correction.

[0122] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A groutable hollow sandwich multi-chord anchor axial force meter, characterized in that: It comprises an anchor head (1), a plurality of through-hole anchor rods (2) and a steel bar meter (3) distributed between two adjacent through-hole anchor rods (2); The steel bar meter (3) comprises a connecting sleeve (31), wherein a cable (32) is sealed and fixed to the outside of the connecting sleeve (31), and a connecting coil (33) connected to the cable (32) is embedded in the inner wall of the connecting sleeve (31); The through-hole anchor rod (2) has a through-hole structure design inside, and thread openings are provided on the outside of both ends of the through-hole anchor rod (2); The connecting sleeve (31) in the steel bar gauge (3) is also provided with threaded openings matching the through anchor rod (2) at both ends thereof, and the steel bar gauge (3) is threadedly connected to the through anchor rod (2) via the threaded openings; The anchor head (1) is connected to one end of the through anchor rod (2) via internal threads, one end of the through anchor rod (2) is connected to a fastening nut (4) via internal threads, and a bottom pad (5) is sleeved between the fastening nut (4) and the through anchor rod (2).

2. A method for using a groutable hollow sandwich multi-chord anchor axial force meter according to claim 1, characterized in that: The specific steps include: S1. Anchor bolt axial force meter is composed of multiple steel bar meters and cylindrical steel bar measuring rods with threaded ends at both ends. The ends of the anchor bolt are connected to the steel bar meters by a shorter steel bar measuring rod with a threaded end. The length of the wire at each measuring point of the anchor bolt is different. S2. Drill holes at the installation location with a hole diameter of 50mm-60mm. Determine the hole depth according to the design plan. The deepest measuring point in the hole is N. The length of the wire to each measuring point at the hole mouth is N--(N+1)--(N+2)--(N+3)--(N+4); S3. After assembling the anchor rod, check each joint to make sure it is tightly connected, and install it into the drilling measuring point hole. The hole diameter is 55mm, and the hole depth is based on the length of the anchor rod plus 10 centimeters. Grouting is performed. The grouting depth should include all sensors. Finally, use anchoring agent to seal it. S4. Collect and measure data through the anchor axial force meter measurement system, and detect the stress condition of the anchor axial force meter in the project.

3. The method for using the groutable hollow sandwich multi-chord anchor axial force meter according to claim 2, characterized in that: The anchor axial force meter measurement system comprises: Sensor unit: used to detect the strain, displacement or pressure of the anchor rod. The sensor includes a resistance strain gauge, a fiber grating sensor and a piezoelectric sensor; Signal acquisition unit: converts the analog signal collected by the sensor into a digital signal and transmits it to the data processing unit. The signal acquisition unit usually includes a signal conditioning circuit and an analog-to-digital converter; Data processing unit: processes and analyzes the collected signals and calculates the axial force value of the anchor. This unit can be embedded in the control system or processed through cloud computing; Display and storage unit: used to display measurement results in real time and store historical data for further analysis.

4. The method for using the groutable hollow sandwich multi-chord anchor axial force meter according to claim 3 is characterized by: The specific steps of using the anchor axial force meter measurement system are as follows: Step 1: The built-in sensor of the steel bar meter transmits data and feedback to the axial force meter measurement system through cables, and adopts a multi-point monitoring method for data acquisition and integrated analysis; Step 2: Signal acquisition and signal conditioning: The analog signal output by the sensor is amplified and filtered through the signal conditioning circuit to remove interference signals and ensure the accuracy of the signal; Data acquisition: convert the processed analog signal into a digital signal through an analog-to-digital converter and transmit the data to the data processing unit; Step 3: Data processing and calculation, strain-axial force conversion: according to the type of sensor and calibration curve, the strain or displacement signal is converted into the axial force value; F=K·∈ Where F is the axial force, K is the calibration coefficient of the sensor, and ∈ is the measured strain value; Error correction: Considering the influence of environmental factors such as temperature and humidity, the measurement value is corrected through compensation algorithm to further improve the measurement accuracy; Data analysis: Compare the calculated axial force data with the design value, analyze the stress state of the anchor rod, and determine whether there is any abnormality Step 4: Data display and storage: The axial force data of the anchor bolt is displayed in real time on the display screen or computer interface to facilitate monitoring by operators, and the historical measurement data is stored in a local or cloud database for subsequent analysis and engineering evaluation.

5. The method for using the groutable hollow sandwich multi-chord anchor axial force meter according to claim 4, characterized in that: The resistance strain gauge method: Among them: F is the axial force of the anchor, E is the elastic modulus of the anchor material, A is the cross-sectional area of ​​the anchor, ∈ is the strain value, ν is the Poisson's ratio; Fiber Bragg grating method: F=K g ·Dl Where: K g Calibration coefficient of fiber Bragg grating, Δλ wavelength offset; Temperature compensation algorithm formula: F corr =F-α·ΔT Among them: F corr Axial force after temperature compensation, α temperature compensation coefficient, ΔT temperature change.

6. The method for using the groutable hollow sandwich multi-chord anchor axial force meter according to claim 5, characterized in that: Through the arrangement of multiple sensors, the strain data of the anchor rod at different positions are collected, and the weighted average and interpolation algorithms are used to fuse the data; Weighted average method: N sensors are installed at different positions of the anchor, and the strain data collected are ∈1, ∈2, ..., ∈ n , then the overall strain ∈ can be calculated by weighted average method avg : where w i , is the weight of sensor i, which is set according to the location of the sensor and the importance of the measurement; Interpolation algorithm: The distribution of sensors is sparse, and interpolation algorithms, such as linear interpolation or spline interpolation, are used to estimate the strain values ​​at other locations of the anchor rod and then calculate the overall axial force.

7. The method for using the groutable hollow sandwich multi-chord anchor axial force meter according to claim 6, characterized in that: According to the theory of material mechanics, the relationship between the axial force F and the strain ∈ can be expressed by Hooke's law: F=E·A·∈ avg Where: E is the elastic modulus of the anchor material, A is the cross-sectional area of ​​the anchor, ∈ avg is the overall strain after integrated analysis.

8. The method for using the groutable hollow sandwich multi-chord anchor axial force meter according to claim 7, characterized in that: In order to ensure the accuracy of the measurement data, the Z-score outlier detection algorithm is introduced to detect and process outliers; score anomaly detection: For each measurement point ∈ i , calculate its Z-score: Where μ is the mean value of strain data, σ is the standard deviation, when Z i When it exceeds a certain threshold (such as 3), it is considered that ∈ i These are outliers and need to be removed or corrected.

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