Embankment safety rapid grading method based on engineering geophysical prospecting data

Abstract

The invention discloses an engineering geophysical prospecting data-based embankment safe and rapid grading method, which relates to the technical field of embankment safe and rapid grading methods, and comprises the steps of testing embankment soil state parameters, establishing a relation between geophysical prospecting data and soil state, carrying out embankment safe and rapid grading and the like. Through soil sample testing, the relation between the compactness, the water content and the like of a soil body and indexes such as dielectric constants, elastic wave velocities and electrical resistivity is established; through a forward modeling test or a physical test, relevance between multi-source geophysical prospecting parameters such as radar waves, elastic waves and resistivity and core factors such as embankment body structural integrity, embankment foundation stability and seepage conditions reflecting embankment structure safety is established, and a geophysical prospecting data analysis principle is formed; and adopting an analytic hierarchy process, and introducing a dike aging factor to construct a discrimination matrix to calculate a dike comprehensive score. According to the method, safe, rapid and dynamic grading of the dike can be realized, the dike risk level is pre-warned, and guidance is provided for rescue power investment.

Description

Technical Field

[0001] The present invention relates to the technical field of dike safety classification methods, and in particular to a rapid dike safety classification method based on engineering geophysical exploration data. Background Art

[0002] my country's levee projects are massive, but existing technology makes it difficult to quickly assess their safety hazards. During flood season, levee leakage and piping, if not promptly diagnosed and treated, can easily lead to a chain reaction of disasters, culminating in major breaches and collapses. There's an imbalance and mismatch between the amount of emergency rescue resources needed to inspect and protect levee hazards during the flood season. A key reason for this is the inability to quickly assess the dynamic development of levee hazards, assess their safety status, and provide early warning of risk levels, thereby effectively deploying emergency response resources.

[0003] Currently, methods for assessing and warning of levee safety during flood seasons have significant shortcomings. While the development of geophysical exploration technology has provided effective methods for detecting hidden dangers within levees, current detection methods tend to be static and can only provide information on the distribution of defects such as looseness, high water content, and voids. They are unable to assess the development trends of hazards under high water levels and provide early warning of levee disaster risks. On the other hand, current levee safety assessments primarily rely on manual inspections, core sampling, and recalculation to comprehensively determine levee safety levels. However, these assessments still have the following shortcomings for flood season levee safety assessments: (1) Soil mechanics parameter tests are mostly “one-sided” and cannot fully reflect the overall condition of the project. Sampling disturbance will cause the soil mechanics parameter test results to be distorted, resulting in inconsistency with the actual conditions on site; (2) The test is time-consuming and the evaluation cost is high. It focuses more on static evaluation and cannot reflect the deterioration of the embankment under the influence of high water levels during the flood season. It is difficult to meet the requirements of efficient early warning during the flood season.

[0004] In order to make up for the shortcomings of existing technologies, the advantage of geophysical technology in quickly obtaining levee performance information is utilized. By establishing the correlation between geophysical parameters and the safety status of levee structures, a flood season levee safety classification method based on levee engineering geophysical data is proposed, thereby realizing rapid levee safety classification and early warning of levee risks. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to establish the correlation between multi-source geophysical parameters such as radar waves, elastic waves, resistivity and the core factors reflecting the safety of the embankment structure, such as the structural integrity of the embankment, the stability of the embankment foundation, and the seepage conditions, and use the hierarchical analysis method to construct a discriminant matrix to calculate the comprehensive score of the embankment, so as to realize the dynamic evaluation of the embankment safety level.

[0006] To achieve the above objectives, the present invention provides the following technical solutions: a rapid embankment safety classification method based on engineering geophysical data, comprising: 1. Testing embankment soil state parameters This step is specifically carried out along the following routes.

[0007] S1.1. Select a typical embankment section and drill soil samples from the embankment body and embankment foundation; S1.2, determine the liquid limit, plastic limit and other geotechnical parameters of soil samples; S1.3, reshape soil samples with different moisture contents and compaction degrees, and measure physical indicators such as dielectric constant, elastic wave velocity, and resistivity of the soil samples.

[0008] Furthermore, the soil sample reshaped in step S1.3 includes soil samples with measured liquid limit and plastic limit moisture contents.

[0009] Furthermore, the following methods are used to determine the physical indicators of S1.3: ① Weigh the dry soil mass corresponding to different dry densities according to the same volume mass method; ② Prepare soil samples with the required moisture content according to the mass moisture content method and let them stand for 12 hours to allow the moisture to be evenly distributed; ③ Carry out homemade compaction tests according to the dry density and moisture content ratio to obtain soil column samples; ④ The prepared soil column sample is sealed with plastic wrap and placed in a constant temperature box. The capacitance of the soil column sample is obtained using an LCR precision digital bridge. and resistors ; ⑤ Dry the soil column sample to determine the actual moisture content and convert it into volume moisture content.

[0010] Preferably, the dielectric constant described in S1.3 is specifically expressed as follows:

[0011] Where: is the relative dielectric constant; is the dielectric constant of vacuum, is the effective cross-sectional area of the soil sample; is the thickness of the soil sample; is the side length of the test electrode; is the capacitance.

[0012] Preferably, the conductivity in S1.3 is specifically expressed as follows:

[0013]

[0014] Where, R is the measured resistance value in Ω; S is the electrode area, in units of m 2 ; L is the distance between the two electrodes, in m; is the resistivity, in Ω·m; is the electrical conductivity, and its unit is S / m.

[0015] Preferably, the elastic wave velocity test steps described in S1.3 are as follows: Use elastic wave measuring instruments to conduct elastic wave velocity tests; S1.3.1. Level the soil in the model, place a wooden board at one end of the model, and place the external trigger sensor in the center of the excitation plate (maintaining good contact). Place a heavy object on top of the wooden board and place the geophone at different heights on the other side of the template. S1.3.2. Use a hammer to strike one end of the excitation plate. The elastic wave velocity generated on the surface propagates through the stratum and is received by the detector. The signal is then sent to the motion meter via a cable. At the same time, the striking signal is also received by the external trigger sensor and triggers the motion meter via the external trigger input terminal. After the motion meter is triggered, it records and displays the elastic wave velocity signal on the screen.

[0016] S1.3.3. Calculate the elastic wave velocity Vs based on the elastic wave velocity signal.

[0017] 2. Establishing the connection between geophysical data and soil conditions S2.1. Based on the obtained parameters (dielectric constant, conductivity, elastic wave velocity), establish a numerical forward model or a physical test model.

[0018] Furthermore, the model includes a layered model with different preset infiltration line heights and a local anomaly model with hidden dangers of different scales and degrees.

[0019] S2.2. Carry out forward modeling or testing of radar wave method, resistivity method, elastic wave method, etc. to obtain response signals corresponding to the development of embankment physical properties.

[0020] S2.3: Since parameter indices (dielectric constant, conductivity, elastic wave velocity) are determined based on soil sample conditions (moisture content, compaction), and these parameters determine the response signals of geophysical prospecting methods (radar wave method, resistivity method, elastic wave method), the above steps establish a connection between soil sample conditions, parameter indices, and response signals.

[0021] S2.4, in step S1.2, introduce the time variable to further derive the incremental law of the response signal change of the soil sample state during different water level loading periods.

[0022] In S2.5, the response signal corresponding to the liquid limit state is used as the lower threshold, and the response signal corresponding to the design state is used as the upper threshold. The liquid limit and design state intervals are divided into several equal parts, and the response signals are assigned scores. A time variable is introduced, and the reduction factor is calculated based on the rate of change of the signal scores.

[0023] Preferably, the response signal score corresponding to the state of moisture content > liquid limit is 1, and the response signal score corresponding to the state of compaction degree ≥ design is 10. Preferably, the faster the signal score changes, the worse the soil condition is, and the smaller the corresponding reduction factor is.

[0024] 3. Rapid classification of embankment safety S3.1, Divide the embankment sections into sections with safety classification. The embankment sections with safety classification should have completed the testing of embankment soil state parameters and established the connection between geophysical data and soil state.

[0025] S3.2, quantitative indicators reflecting the safety status of the embankment from four aspects: embankment structural integrity, embankment foundation stability, seepage conditions and aging degree.

[0026] Furthermore, the structural integrity of the embankment is assessed by detecting the degree of development of hidden dangers inside the embankment using the radar wave method; the stability of the embankment foundation is determined by using the wave velocity characteristic data of the embankment foundation rock and soil obtained using the elastic wave method; the seepage condition is reflected based on data such as the water content distribution obtained using the resistivity method; and the degree of aging is determined based on the embankment's service life, historical maintenance records, and characteristics of previous years' accidents.

[0027] S3.3, construct a judgment matrix and establish a grading method that comprehensively considers the embankment safety status and single indicator control. The details are as follows: S3.3.1 Comprehensively consider the levee safety status: A comprehensive scoring method using a scale of 1 to 10 is used. Refer to step 2.5 for scoring each signal. The coefficients for levee structural integrity, foundation stability, seepage conditions, and aging are B1, B2, B3, and B4, respectively. B1 + B2 + B3 + B4 = 1. A score of [8, 10] indicates a safety level; [5-8] indicates a basic safety level; and [0-5] indicates an unsafe level, requiring an early warning. If the same levee section is surveyed more than twice, and the score decreases by ≥2 points between the two surveys, the level will be downgraded by one level.

[0028] The scoring rules are as follows: Structural integrity of the embankment: If the ground penetrating radar detects no obvious abnormalities in the embankment, a value of 9 is assigned; if there are a few tiny cracks, a value of 7 is assigned; if there are many cracks or small voids, a value of 5 is assigned; if there are large voids or serious cracks, a value of 3 is assigned.

[0029] Embankment foundation stability: If the elastic wave method or resistivity method shows that the embankment foundation rock and soil properties are good and there is no sign of sliding, the value is assigned to 9; if there is a slight abnormality but it does not affect the overall stability, the value is assigned to 7; if there is a large-scale weak layer or potential sliding surface, the value is assigned to 5; if there is obvious signs of instability, the value is assigned to 3.

[0030] Seepage conditions: If the resistivity method shows that the seepage is normal and the water content is within the safe range, a value of 9 is assigned; if the seepage is slightly abnormal and the water content is slightly high, a value of 7 is assigned; if the seepage is obviously abnormal and the water content is close to the dangerous value, a value of 5 is assigned; if the seepage is seriously abnormal and the water content exceeds the dangerous value, a value of 3 is assigned.

[0031] Degree of aging: The degree of aging is assessed based on the service life of the levee, historical maintenance records, and accident data over the years. For example, a newly built and well-maintained levee is assigned a value of 9, while an levee with a long service life and signs of accidents over the years is assigned a value of 3. The intermediate state is assigned a value between 3 and 9 based on actual conditions.

[0032] S3.3.2 Single indicator control: When there are two or more measuring lines along the embankment axis, and any score of the embankment structural integrity, embankment foundation stability, and seepage condition in the same area is ≤1, that is, there are areas below the soil liquid limit at the same section of the embankment, which is an unsafe level and requires an early warning.

[0033] Compared with the existing technology, the rapid embankment safety classification method based on engineering geophysical data provided by the present invention has the following beneficial effects: (1) Comprehensively reflect the safety status of levee structures through multi-source geophysical data (radar wave method, resistivity method, elastic wave method, etc.) and levee aging data, overcoming the limitations of a single geophysical method or assessment factor.

[0034] (2) Dynamic assessment innovation: The present invention can repeat the assessment periodically or under specific working conditions, and adjust the safety classification in real time according to the dynamic changes of geophysical data, thus providing continuous and accurate safety assessment support for the deployment of emergency rescue forces in embankments during flood season.

[0035] (3) It should be pointed out that step 1 of the present invention, testing the parameters of the embankment soil state, and step 2 of establishing the relationship between the geophysical data and the soil state, need to be completed before the flood season to form the geophysical data analysis principle; thus, step 3 of the embankment safety rapid classification can be completed quickly during the flood season. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 : is a schematic flow chart of the method for rapid grading of embankment safety based on engineering geophysical data of the present invention; Figure 2 : Schematic diagram of the working principle of the transient Rayleigh wave exploration method of the present invention; Figure 3 : This is a schematic diagram of the embankment profile collected by the exploration of the present invention; Figure 4 : This is a schematic diagram of the three-dimensional exploration embankment of the present invention; Figure 5 : is a schematic diagram of a typical ground penetrating radar cross-section of the dike top according to the present invention; Figure 6 : A schematic cross-sectional diagram of radar anomaly interpretation of the dike of the present invention; Figure 7 : A schematic cross-sectional diagram of radar anomaly interpretation of the back slope of the dike according to the present invention. DETAILED DESCRIPTION

[0037] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative work shall fall within the scope of protection of the present invention. The present invention will be described in further detail below based on the accompanying drawings and examples; Please refer to the attached Figure 1 To the attached Figure 7 As shown: To solve the problems mentioned in the technical solution, the present application provides a method for rapid grading of embankment safety based on engineering geophysical data, including: S1, test embankment soil state parameters; S2, establish the connection between geophysical data and soil conditions; S2, rapid grading of dike safety.

[0038] S1 specifically includes: S1.1. Select a typical embankment section and drill soil samples from the embankment body and embankment foundation; S1.2, determine the liquid limit, plastic limit and other geotechnical parameters of soil samples; S1.3, reshape soil samples with different moisture contents and compaction degrees, and measure physical indicators such as dielectric constant, elastic wave velocity, and resistivity of the soil samples.

[0039] Prepare different media and fill them into PVC tubes. The PVC tubes are then sealed and buried in the embankment simulation. The soil above is then compacted and the test surface is leveled. To facilitate comparative analysis of detection results, the PVC tubes are buried in the same position each time. Multiple PVC tubes with diameters of 2cm and 4cm are used to cover scattered embankment voids, arranged in two rows. All other hidden dangers are covered with PVC tubes with a diameter of 10cm.

[0040] Table 1 As shown in Table 1, the soil samples with different moisture contents and compaction degrees described in S1.3 include the soil samples with measured liquid limit and plastic limit moisture contents. The physical indicators described in S1.3 are measured using the following methods: ① Weigh the dry soil mass corresponding to different dry densities according to the same volume mass method; ② Prepare soil samples with the required moisture content according to the mass moisture content method and let them stand for 12 hours to allow the moisture to be evenly distributed; ③ Carry out homemade compaction tests according to the dry density and moisture content ratio to obtain soil column samples; ④ Seal the prepared soil column sample with plastic wrap and place it in a constant temperature box. Use an LCR precision digital bridge to obtain the capacitance and resistance of the soil column sample. ⑤ Dry the soil column sample to determine the actual moisture content and convert it into volume moisture content.

[0041] The test uses a VC4090A LCR precision digital bridge connected to a modified parallel plate electrode wire. A copper electrode with a diameter of 62mm is placed in close contact with the soil column. The same pressure is applied, the same test frequency is set, and the same voltage is set to test the capacitance index of the soil column to obtain the relative dielectric constant of the soil. , specifically expressed as follows: The dielectric constant described in S1.3 is specifically expressed as follows:

[0042] Where: is the relative dielectric constant; is the dielectric constant of vacuum, A is the effective cross-sectional area of the soil sample; is the thickness of the soil sample; b is the side length of the test electrode; is the capacitance.

[0043] In this test, the TH2830 impedance analyzer was used to test its resistance using AC current. The scanning frequency was set to 100kHz, the single measurement time was 10s, and the sampling interval was 0.1s. During the test, the test fixture was clamped on the same set of copper sheet electrodes. The average value of the measured resistance was taken and substituted into the formula to obtain the conductivity, which is specifically expressed as follows; The specific formula for the conductivity described in S1.3 is as follows:

[0044]

[0045] Where, R is the measured resistance value in Ω; S is the electrode area, in units of m 2 ; L is the distance between the two electrodes, in m; is the resistivity, in Ω·m; is the electrical conductivity, and its unit is S / m.

[0046] The elastic wave velocity test steps described in S1.3 are as follows: S1.3.1. Level the soil in the model, place a wooden board at one end of the model, and place the external trigger sensor in the center of the excitation plate. Place a heavy object on top of the wooden board and place the geophone at different heights on the other side of the template. S1.3.2. Strike one end of the excitation plate with a hammer. The elastic wave velocity generated on the surface propagates through the stratum and is received by the geophone. This signal is then sent via a cable to the motion meter. Simultaneously, the striking signal is received by the external trigger sensor, which triggers the motion meter via the external trigger input. Once triggered, the motion meter records and displays the elastic wave velocity signal on the screen. S1.3.3. Calculate the elastic wave velocity Vs based on the elastic wave velocity signal.

[0047] The elastic wave velocity test steps are as follows: Elastic wave velocity testing is performed using an elastic wave measuring instrument. The instrument uses the RS series pile dynamic tester, which has an elastic wave velocity measurement module. When used with an external detector and an external trigger sensor, it can perform structural elastic wave velocity testing. S3.1. Level the soil in the model, place a wooden board at one end of the model, and place the external trigger sensor in the center of the excitation plate (maintaining good contact). Place a heavy object on top of the wooden board and place the geophone at different heights on the other side of the template. S3.2: Use a hammer to strike one end of the excitation plate. The elastic wave velocity generated on the surface propagates through the stratum and is received by the geophone. This signal is then sent to the motion meter via a cable. Simultaneously, the striking signal is received by the external trigger sensor, which triggers the motion meter via the external trigger input. Once triggered, the motion meter records and displays the elastic wave velocity signal on the screen. Among them, the specific expression of the relationship between elastic wave velocity and soil shear modulus is as follows:

[0048] Where, is the shear wave velocity; is the shear modulus; is the soil density; Static earth pressure coefficient The relationship with the friction angle is as follows:

[0049]

[0050] From this we can get:

[0051] And for Poisson's ratio:

[0052] In addition, studies have shown that the coefficient of static earth pressure of transversely isotropic in-situ soil is related to the elastic wave velocity in both vertical and horizontal directions:

[0053] Therefore, the basic mechanical properties of soil are directly related to the shear modulus, and the elastic wave velocity can be used to analyze the stability of the soil;

[0054] Table 2 S2 specifically includes: S2.1. Based on the obtained parameters of different dielectric constants, electrical conductivity, and elastic wave velocity, establish a numerical forward model or a physical test model. The model includes a layered model with preset different infiltration line heights and a local anomaly model with different scales and degrees of hidden dangers; S2.2. Carry out forward modeling or testing of radar wave, resistivity, elastic wave and other detection methods to obtain response signals corresponding to the development of embankment physical properties; S2.3, since the parameter index is determined according to the soil sample state, and the parameter index determines the response signal of the geophysical prospecting method, the above steps establish the connection from the soil sample state to the parameter index and then to the response signal; S2.4, in step S2, the time variable is introduced to further derive the incremental law of the response signal change of the soil sample state during different water level loading periods; S2.5, take the response signal corresponding to the liquid limit state of the soil sample as the lower threshold, and the response signal corresponding to the design state of the soil sample as the upper threshold. Divide the liquid limit state and design state interval into several equal parts, assign points to the response signal, introduce a time variable, and calculate the reduction coefficient based on the rate of change of the signal score.

[0055] The response signal corresponding to the liquid limit state described in S2.5 is assigned a value of 1 if it is less than or equal to the liquid limit state; the response signal corresponding to the design state is assigned a value of 10. The faster the signal assignment changes, the worse the soil state is and the smaller the corresponding reduction factor is.

[0056] S3 includes the following steps: S3.1, divide the safety graded embankment sections into sections. The safety graded embankment sections should have completed the first and second sections; S3.2, quantitative indicators reflecting the safety status of the levee from four aspects: structural integrity of the levee, stability of the levee foundation, seepage conditions, and degree of aging; S3.3, construct a judgment matrix and establish a grading method that comprehensively considers the levee safety status and single indicator control.

[0057] The specific details of the embankment safety status and single indicator control described in S3.3 are as follows: S3.3.1 Comprehensive consideration of levee safety status: A comprehensive scoring method with a scale of 1-10 is used, with the levee structural integrity, levee foundation stability, seepage condition, and aging degree coefficients being B1, B2, B3, and B4, respectively, with B1+B2+B3+B4=1; The scoring rules are as follows: Structural integrity of the embankment: If the ground penetrating radar detects no obvious abnormalities in the embankment, a value of 9 is assigned; if there are a few tiny cracks, a value of 7 is assigned; if there are many cracks or small voids, a value of 5 is assigned; if there are large voids or serious cracks, a value of 3 is assigned.

[0058] Embankment foundation stability: If the elastic wave method or resistivity method shows that the embankment foundation rock and soil properties are good and there is no sign of sliding, the value is assigned to 9; if there is a slight abnormality but it does not affect the overall stability, the value is assigned to 7; if there is a large-scale weak layer or potential sliding surface, the value is assigned to 5; if there is obvious signs of instability, the value is assigned to 3.

[0059] Seepage conditions: If the resistivity method shows that the seepage is normal and the water content is within the safe range, a value of 9 is assigned; if the seepage is slightly abnormal and the water content is slightly high, a value of 7 is assigned; if the seepage is obviously abnormal and the water content is close to the dangerous value, a value of 5 is assigned; if the seepage is seriously abnormal and the water content exceeds the dangerous value, a value of 3 is assigned.

[0060] Degree of aging: The degree of aging is assessed based on the service life of the levee, historical maintenance records, and accident data over the years. For example, a newly built and well-maintained levee is assigned a value of 9, while an levee with a long service life and signs of accidents over the years is assigned a value of 3. The intermediate state is assigned a value between 3 and 9 based on actual conditions.

[0061] S3.3.2 Single indicator control: When there are two or more measuring lines along the axis of the embankment, and any score of the embankment structural integrity, embankment foundation stability, and seepage condition in the same area is less than or equal to 1, that is, there are areas below the soil liquid limit at the same section of the embankment, which is an unsafe level and requires an early warning.

[0062] Among them, the grading and assessment rules for comprehensive grading based on the appearance of the levee, elastic wave velocity index, and electromagnetic wave index are as follows: (1) The embankment is graded based on its appearance, elastic wave velocity index, and electromagnetic wave index. If any one of the indicators is at an unsafe level, the embankment is classified as unsafe. (2) When the elastic wave velocity index exists locally <140m / s, but the elastic wave velocity is generally stable, and the electromagnetic wave indicators and appearance conditions can reach basic safety or safety. This section of the embankment is classified as basically safe; (3) When the electromagnetic wave index has a local amplitude ratio greater than 0.7, but the area is small, and the elastic wave velocity index and appearance state can reach basic safety or safety, the embankment section is classified as basically safe; The specific implementation process of the above embodiment is as follows: First, preliminary engineering application: A field test was conducted on a certain embankment project. The embankment section was classified by conducting appearance investigation, elastic wave velocity and electromagnetic wave detection, combined with the proposed classification method based on geophysical parameters.

[0063] Second, engineering background: The embankment grade of a certain embankment is level 4, and the cross-section of the embankment is a relatively regular trapezoid. There is a platform on the inner slope of some sections of the embankment. The embankment height is 4 to 6 meters, the embankment top elevation is 12.5 to 15.0 meters, the embankment top width is 3 to 30 meters, and the slope ratio of the inner and outer slopes is 1:1.25 to 1:2.0. In 2019, the embankment was raised and thickened on the basis of the old embankment, and the reinforcement was carried out according to the standard section. The reinforcement method was to cut the slope facing the water and reinforce the side away from the water to avoid encroaching on the river channel, and cone grouting was carried out on the embankment with poor soil quality and high permeability sandy loam.

[0064] Based on historical quality, the levee section surveyed experienced hazards such as seepage, leakage, external steep slopes, and landslides between 1983 and 2010. Prior to the field test, the river water level in front of the levee exceeded the guaranteed water level for more than five consecutive days, and measures such as timber pile reinforcement and gravel filtration were implemented. To determine the current safety status of the levee, the proposed levee classification method based on geophysical parameters was used to assess the levee's classification.

[0065] Step one, elastic wave velocity index test. According to the on-site detection conditions, this field test uses the Rayleigh wave method for detection. The phase velocity of the Rayleigh wave in the formation is close to the elastic wave velocity, which can be used to make an overall judgment on the safety of the embankment. The Rayleigh wave method is an important branch of seismic exploration. The effective action depth of the Rayleigh wave is generally regarded as 1 / 2 of the wavelength. The size of the wavelength is inversely proportional to the frequency of the Rayleigh wave and directly proportional to the velocity, that is, λ=VR / f; and in inhomogeneous media, the speed of the Rayleigh wave is related to the elastic distribution characteristics of the medium within the effective action depth range. It can be seen that Rayleigh waves of different frequencies have different effective detection depths, and the elastic distribution of the medium is different in different detection depth ranges. Its comprehensive elastic characteristics show different Rayleigh wave velocities, thus forming the velocity dispersion phenomenon of the Rayleigh wave. By utilizing the dispersion phenomenon, the phase velocity V of surface waves of different frequencies can be accurately obtained. R ; Step 2: Electromagnetic wave detection. Ground-penetrating radar was used to detect the surface of the Yuxi River embankment. Two longitudinal lines were laid out along the crest and backslope of the embankment, and one along the embankment itself. A 100MHz antenna was used to continuously measure along the longitudinal lines, moving at a rate of approximately 0.6m / s. Markers were activated every 3m along the longitudinal direction to accurately control the detection position. All observation data were converted to digital form and stored as data files on a host computer for interpretation and inference analysis.

[0066] The ground penetrating radar detection results are as follows: (1) Representative diagram of radar interpretation of dike profile along the dike top is attached. Figure 5 ~Attached Figure 6 The overall waveform is relatively stable, without abnormal reflection. There are abnormal reflections in some parts. The soil in this abnormal area is uneven and has high water content, and the amplitude ratio is <0.7.

[0067] (2) Representative diagram of radar interpretation of dike profile along the back slope of dike is attached. Figure 7 There is an anomaly in the radar reflection wave in the range of pile numbers 28+753 to 28+758. According to the distribution characteristics of the radar waveform, it is judged that the soil in this abnormal area has high water content.

[0068] (3) No high-water level infiltration line interface reflection was observed on the embankment top and back slope survey lines, indicating that the anti-seepage performance of the front embankment blanket was good and there was no abnormal distortion of the infiltration line.

[0069] Step 3: Levee classification evaluation. The levee in this section is classified according to the levee classification method based on geophysical indicators, taking into account the levee's appearance, elastic wave velocity index, and electromagnetic wave index: (1) Comprehensive on-site investigation and measurement of the embankment showed that there were no signs of landslides, collapses, cracks, etc. in this section of the embankment, and no leakage, piping, or other water outlets were found on the back slope.

[0070] (2) According to the elastic wave detection results, the wave velocity map shows that the embankment soil layer interface is generally flat, the embankment soil is generally evenly distributed, there are abnormally low-speed areas in the local surface layer, and the wave velocity in the shallow layer is less than 140m / s.

[0071] (3) According to the results of electromagnetic wave detection, no abnormal distortion of the infiltration line was found on the top and back slope of the dike; there were abnormal leakage reflections in some areas, and the amplitude ratio was less than 0.7.

[0072] In summary, the elastic wave index exists locally <140m / s, but the overall wave speed is basically stable, the electromagnetic wave indicators can reach basic safety, and the appearance status can reach safety. The status of this section of the embankment meets the "basic safety" classification standard, and the comprehensive classification is basically safe.

[0073] It should be noted that, in this document, relational terms such as first and second, etc., are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the terms "comprises," "comprising," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or device comprising a series of elements includes not only those elements, but also other elements not explicitly listed, or elements inherent to such process, method, article, or device. In the absence of further limitations, an element defined by the phrase "comprising a ..." does not exclude the presence of additional identical elements in the process, method, article, or device comprising the element.

[0074] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

Claims

1. A rapid embankment safety classification method based on engineering geophysical data, characterized by: include: S1, test embankment soil state parameters; S2, establish the connection between geophysical data and soil conditions; S3, rapid grading of dike safety.

2. The rapid grading method for embankment safety based on engineering geophysical data according to claim 1 is characterized in that: Said S1 specifically includes: S1.

1. Select a typical embankment section and drill soil samples from the embankment body and embankment foundation; S1.2, determine the geotechnical indicators of liquid limit and plastic limit of soil samples; S1.

3. Reshape soil samples with different moisture contents and compaction degrees and measure the physical properties of the soil samples, including dielectric constant, elastic wave velocity, and resistivity.

3. The rapid grading method for embankment safety based on engineering geophysical data according to claim 2 is characterized in that: The soil samples with different moisture contents and compaction degrees described in S1.3 include the soil samples with measured liquid limit and plastic limit moisture contents. The physical indicators described in S1.3 are measured using the following methods: ① Weigh the dry soil mass corresponding to different dry densities according to the same volume mass method; ② Prepare soil samples with the required moisture content according to the mass moisture content method and let them stand for 12 hours to allow the moisture to be evenly distributed; ③ Carry out homemade compaction tests according to the dry density and moisture content ratio to obtain soil column samples; ④ Seal the prepared soil column sample with plastic wrap and place it in a constant temperature box. Use an LCR precision digital bridge to obtain the capacitance and resistance of the soil column sample. ⑤ Dry the soil column sample to determine the actual moisture content and convert it into volume moisture content.

4. The rapid grading method for embankment safety based on engineering geophysical data according to claim 2 is characterized in that: The dielectric constant described in S1.3 is specifically expressed as follows: Where: is the relative dielectric constant; is the dielectric constant of vacuum, A is the effective cross-sectional area of the soil sample; is the thickness of the soil sample; b is the side length of the test electrode; is the capacitance.

5. The rapid grading method for embankment safety based on engineering geophysical data according to claim 2 is characterized in that: The specific formula for the conductivity described in S1.3 is as follows: Where, R is the measured resistance value in Ω; S is the electrode area, in units of m 2 ; L is the distance between the two electrodes, in m; is the resistivity, in Ω·m; is the electrical conductivity, and its unit is S / m.

6. The rapid grading method for embankment safety based on engineering geophysical data according to claim 2 is characterized in that: The elastic wave velocity described in S1.3 is tested by an elastic wave measuring instrument. The specific test steps are as follows: S1.3.

1. Level the soil in the model. Install an excitation plate on one side of the soil. Place a wooden board at one end of the model. Place the external trigger sensor in the center of the excitation plate. Place a heavy object on top of the wooden board. Place the geophone at different heights on the other side of the template. S1.3.

2. Use a hammer to strike one end of the excitation plate. The elastic wave generated on the surface propagates through the stratum and is received by the geophone. The signal is then sent to the motion detector via a cable. Simultaneously, the striking signal is received by the external trigger sensor and triggers the motion detector via the external trigger input. After the kinetic detector is triggered, it records and displays the elastic wave velocity signal on the screen; S1.3.

3. Calculate the elastic wave velocity Vs based on the elastic wave velocity signal.

7. The rapid grading method for embankment safety based on engineering geophysical data according to claim 1 is characterized in that: The S2 specifically includes: S2.

1. Acquire geophysical data, including different electrical constants, electrical conductivity, and elastic wave velocity parameters, and establish numerical forward models or physical test models. The models include layered models with preset infiltration line heights and local anomaly models with different scales and degrees of hidden dangers. S2.

2. Conduct forward modeling or testing using radar wave, resistivity, and elastic wave methods to obtain response signals corresponding to the development of embankment physical properties; S2.3, since the parameter index is determined based on the soil sample state, the parameter index is associated with the response signal of the geophysical prospecting method. Through the above steps S2.1-S2.3, a connection is established from the soil sample state to the parameter index and then to the response signal; S2.4, in step S2, the time variable is introduced to further derive the incremental law of the response signal change of the soil sample state during different water level loading periods; S2.5, take the response signal corresponding to the liquid limit state of the soil sample as the lower threshold, and the response signal corresponding to the design state of the soil sample as the upper threshold. Divide the liquid limit state and design state interval into several equal parts, assign points to the response signal, introduce a time variable, and calculate the reduction coefficient based on the rate of change of the signal score.

8. The rapid embankment safety classification method based on engineering geophysical data according to claim 7 is characterized in that: The response signal corresponding to the liquid limit state described in S2.5 is assigned a value of 1 for the response signal corresponding to the state below the liquid limit; the response signal corresponding to the state above the design state is assigned a value of 10. The faster the signal assignment changes, the worse the soil state is and the smaller the corresponding reduction factor is.

9. The rapid embankment safety classification method based on engineering geophysical data according to claim 1 is characterized in that: The S3 specifically includes the following steps: S3.1, divide the safety graded embankment sections into sections. The safety graded embankment sections should have completed the first and second sections; S3.2, quantitative indicators reflecting the safety status of the levee from four aspects: structural integrity of the levee, stability of the levee foundation, seepage conditions, and degree of aging; S3.3, construct a judgment matrix and establish a grading method that comprehensively considers the levee safety status and single indicator control.

10. The rapid grading method for embankment safety based on engineering geophysical data according to claim 9 is characterized in that: The specific details of the embankment safety status and single indicator control described in S3.3 are as follows: S3.3.1 Comprehensive consideration of levee safety status: A comprehensive scoring method with a scale of 1-10 is used, with the levee structural integrity, levee foundation stability, seepage condition, and aging degree coefficients being B1, B2, B3, and B4, respectively, with B1+B2+B3+B4=1; S3.3.2 Single indicator control: When there are two or more measuring lines along the axis of the embankment, and any score of the embankment structural integrity, embankment foundation stability, and seepage condition in the same area is less than or equal to 1, and there are areas below the liquid limit of the soil at the same section of the embankment, it is considered an unsafe level and an early warning is issued.

Images