A combined monitoring and prevention method applicable to the instability and failure of slopes under erosion conditions

Abstract

A joint monitoring method for bank slope instability and damage under erosion conditions, characterized in that the joint monitoring method includes hydraulic gradient monitoring, soil shear strength monitoring and soil surface displacement field monitoring; the hydraulic gradient monitoring results are used to obtain the hydraulic gradient safety factor at different locations of the bank slope, the soil shear strength monitoring results are used to obtain the overall anti-sliding safety factor of the bank slope soil, and the soil surface displacement field monitoring results are used to draw the soil surface shear strain cloud map. The joint monitoring method is applicable to various types of bank slope strata. The present invention accurately detects the impact of erosion on the structural stability of the bank slope soil from three perspectives: hydraulic gradient, soil shear strength and soil surface displacement, and realizes early and accurate prevention and control of waterway bank slope instability and damage. At the same time, the present invention also proposes a graded prevention and control method for bank slope instability and damage based on the joint monitoring results, so as to realize economical, efficient, safe and reliable anti-sliding reinforcement treatment of the waterway bank slope.

Description

Technical Field

[0001] The present invention relates to a combined monitoring and prevention method for slope instability failure under erosion conditions, belonging to the field of geotechnical engineering. Background Art

[0002] The channel slopes are eroded by the wave loads of passing ships for a long time. The erosion will cause the loss of soil components on the slope, the increase of void ratio, and the reduction of strength, which is prone to instability landslide failure. On the one hand, the instability failure of the channel slope will cause the siltation of the channel. On the other hand, it will cause the damage of the slope lane and even induce the backflow of channel water into villages and towns, resulting in great economic and property losses. Therefore, preventing the erosion instability failure of the channel slope plays an important role in protecting the channel ecological environment and maintaining the high-quality development of the local economy.

[0003] Currently, for the monitoring of slopes, most use Beidou positioning, radar measurement and control, UAV mapping, etc. (such as CN118393526A, CN202110638189.7, CN111854699A), or monitoring methods based on the fusion of sounding data and acoustic effects (such as CN116540238B), or based on multi-beam mobile monitoring (such as CN109398624A), or based on microseismic technology (CN110220979A), etc. to monitor the stability of slope soil. It should be noted that these existing technical solutions all judge whether there is a risk of instability landslide of the slope based on the strain of the soil. However, before a large displacement deformation occurs on the slope surface, internal erosion damage of the slope soil has already occurred, and when the internal erosion damage of the slope is transmitted to the surface and shows a large deformation, the strength of the slope soil has been greatly reduced, which is extremely unfavorable for the emergency rescue and disaster relief of the slope, because when the strength of the slope soil is greatly lost, using heavy machinery to reinforce the slope will increase the landslide risk of the slope. Therefore, there is an urgent need for a comprehensive monitoring system that can simultaneously monitor the internal erosion condition of slope soil and the surface deformation, provide sufficient early warning information before a large deformation occurs on the slope surface, provide sufficient time and safety guarantee for slope emergency reinforcement, and ensure the long-term safe and stable operation of the channel slope. Summary of the Invention

[0004] In order to overcome the risk uncertainty brought by the current evaluation of channel slope landslide disasters based on a single index of surface displacement and ensure the long-term safe and stable operation of the channel slope, the present invention provides a combined monitoring and prevention method for slope instability failure under erosion conditions.

[0005] To solve the above problems, the technical solutions adopted by the present invention are as follows:

[0006] A combined monitoring method applicable to the instability failure of slopes under erosion conditions, characterized in that the combined monitoring method includes hydraulic gradient monitoring, soil shear strength monitoring, and soil surface displacement field monitoring;

[0007] The hydraulic gradient monitoring arranges pore water pressure sensors at different positions and depths of the slope to monitor the change of pore water pressure in the slope soil, and calculates the hydraulic gradient at different positions and depths according to formula (1);

[0008]

[0009] In the formula: Δu is the difference in pore water pressure measured by two pore water pressure gauges; ρ w is the density of water; g is the acceleration due to gravity; L is the distance between two pore water pressure gauges;

[0010] The soil shear strength monitoring combines the results of laboratory tests and the monitoring indexes of slope soil to evaluate the shear strength of slope soil at different depths, including earth pressure monitoring, shear wave velocity monitoring, and laboratory unit tests;

[0011] The earth pressure monitoring arranges earth pressure sensors at different positions and depths of the slope to monitor the total earth pressure of the slope, and combines the pore water pressure monitoring results at the same position to calculate the effective stress of the soil at different positions and depths according to formula (2);

[0012] σ′ m =σ - u (2) In the formula: σ' m is the effective stress of the soil; σ is the earth pressure monitoring result; u is the pore water pressure monitoring result;

[0013] The shear wave velocity monitoring is used to obtain the shear wave velocity of the slope soil at different positions and depths, and calculate the void ratio of the slope soil at different positions and depths according to formula (3);

[0014]

[0015] In the formula: e is the void ratio of the soil; ρ is the soil density; V s is the shear wave velocity measurement result; A is a material constant, obtained by fitting the results of laboratory unit tests; n is a constant describing the influence of stress on the shear wave velocity of the soil, determined by fitting laboratory unit tests;

[0016] The laboratory unit test includes shear tests and consolidation-shear wave velocity measurement tests under different void ratio conditions. Among them, the shear test is used to obtain the quantitative correlation between the soil void ratio and the soil internal friction angle, and the consolidation-shear wave velocity measurement test is used to obtain the A value and n value in formula (3);

[0017] Combining the test results of the joint indoor unit and the measured indexes of the bank slope soil mass, calculate the shear strength of the soil mass at different positions and different depths according to Equation (4);

[0018]

[0019] In the formula: τ is the shear strength of the soil mass; is a function of the internal friction angle and void ratio of the soil mass; c' is the cohesion of the soil mass;

[0020] The monitoring of the ground surface displacement field of the soil mass is carried out by setting multiple fixed and non-fixed monitoring points on the ground surface, then taking pictures of the ground surface, analyzing the ground surface displacement field of the bank slope soil mass by comparing the pixel positions of the non-fixed monitoring points in the images at different time periods, and calculating the distribution of the ground surface shear strain of the bank slope soil mass according to Equation (5); The change of the pixel position is judged and measured based on the fixed monitoring point;

[0021]

[0022] In the formula: Δl is the ground surface deformation amount of the bank slope; L 0 is the initial distance of the ground surface measurement point.

[0023] Preferably, the monitoring results of the hydraulic gradient at different positions and different depths can be used to draw the hydraulic gradient contour map of the bank slope area according to the linear interpolation method; carry out the hydraulic gradient test under different void ratio conditions to obtain the relationship between the critical hydraulic gradient and the void ratio when the soil mass undergoes piping failure; based on the relationship between the hydraulic gradient contour map and the critical hydraulic gradient, calculate the hydraulic gradient safety factor at different regional positions according to Equation (6):

[0024]

[0025] In the formula: F w is the hydraulic gradient safety factor; i cr is the critical hydraulic gradient; i is the hydraulic gradient.

[0026] Preferably, the monitoring results of the shear strength of the soil mass are used to draw the effective stress distribution contour map of the soil and calculate the overall anti-sliding safety factor of the bank slope soil mass, and the calculation method of the anti-sliding safety factor is as shown in Equation (7):

[0027]

[0028] In the formula: K is the anti-sliding safety factor; the subscript i represents that the bank slope is divided into i slices; l i is the sliding length at the bottom of the i-th slice.

[0029] Preferably, the monitoring results of the soil surface displacement field are used to draw the soil surface shear strain nephogram; the monitoring of the soil surface displacement field can be implemented by UAV aerial photography or obtained by taking pictures with a camera at a fixed height.

[0030] Preferably, the shear wave velocity monitoring can be implemented by the surface wave method, the downhole method, or the crosshole method; when measuring by the downhole method and the crosshole method, the shear wave geophones need to be placed in the boreholes and have the same burial depth as the pore water pressure sensors and the earth pressure sensors.

[0031] Preferably, the pore water pressure sensors and the earth pressure sensors are buried into the bank slope soil through boreholes and are located at the same depth; the monitoring density of the pore water pressure sensors and the earth pressure sensors is as follows: in the depth direction, the monitoring distance exceeds 5 m from the bottom of the bank slope, and the monitoring interval does not exceed 3 m; in the direction perpendicular to the bank slope, the monitoring distance is the same as that in the depth direction, and the monitoring interval does not exceed 5 m; in the direction along the bank slope, the monitoring distance is related to the engineering requirements, and the monitoring interval does not exceed 10 m; the starting points of the monitoring distances are all the apexes of the bank slope.

[0032] Preferably, the formation types of the bank slope soil include one or more of clay, silty clay, sandy clay, silt, silty clay, sandy silt, sand, sandy clay, sandy silt, sandy gravel, gravel soil, and gravelly sand.

[0033] A method for grading prevention and control of bank slope instability failure based on the combined monitoring results of the bank slope, characterized in that the grading prevention and control method includes the following parts:

[0034] (1) When the hydraulic gradient safety factor is greater than 2, the anti-sliding safety factor is greater than 1.2, and the maximum surface shear strain is less than 0.01%, there is no need to reinforce the bank slope.

[0035] (2) When the hydraulic gradient safety factor is between 1 and 2, or the anti-sliding safety factor is between 1 and 1.2, or the maximum surface shear strain is less than 0.01%, single reinforcement measures can be appropriately taken for the bank slope, including cutting and unloading, anchor reinforcement, and waterproofing of the bank slope surface.

[0036] (3) When the hydraulic gradient safety factor is between 0.95 and 1, or the anti-sliding safety factor is between 0.9 and 1, or the maximum surface shear strain is between 0.01% and 0.1%, single or combined reinforcement measures must be taken for the bank slope, including cutting and unloading, anchor reinforcement, anti-slide pile reinforcement, grouting reinforcement of the erosion surface, and waterproofing of the bank slope surface.

[0037] (4) When the hydraulic gradient safety factor is less than 0.95, or the anti-sliding safety factor is less than 0.9, or the maximum surface shear strain is greater than 0.1%, combined reinforcement measures must be immediately taken for the bank slope, including cutting and load reduction, anchor reinforcement, anti-sliding pile reinforcement, grouting reinforcement of the erosion surface, waterproofing of the bank slope surface, and precipitation behind the bank slope.

[0038] The present invention has the following beneficial effects:

[0039] 1) The present invention comprehensively evaluates the stability of the channel bank slope under the action of erosion load from three perspectives: hydraulic gradient, soil shear strength, and soil surface displacement. The multi-angle evaluation is conducive to accurately detecting the influence of erosion on the stability of the bank slope soil structure, and realizing the early and accurate prevention and control of the instability and failure of the channel bank slope;

[0040] 2) For the ranges of three types of safety factor values, namely the hydraulic gradient safety factor, the anti-sliding safety factor, and the maximum surface shear strain, and in combination with the applicability and economy of different anti-sliding reinforcement treatment methods for the bank slope, the present invention gives a classification prevention and control method for the instability and failure of the bank slope under different conditions, realizing the economic, efficient, safe and reliable anti-sliding reinforcement treatment of the channel bank slope;

[0041] 3) Based on indoor unit tests and on-site shear wave velocity tests, earth pressure monitoring, and pore water pressure monitoring, the present invention realizes the accurate detection of the change in soil porosity ratio caused by the erosion and failure of the bank slope soil, as well as the accurate prediction of the attenuation of soil shear strength, providing theoretical and data support for the anti-sliding reinforcement design of the bank slope;

[0042] 4) The present invention selects the shear wave velocity as the measurement index and scale for the soil porosity ratio of the site. Compared with the traditional penetration test index, it has the advantage of combined indoor and outdoor measurement, is a high-quality non-destructive test method, and the test results have high repeatability and low test cost. Description of the Drawings

[0043] Figure 1 It is a schematic diagram of the combined monitoring method for the instability and failure of the bank slope of the present invention.

[0044] Figure 2 It is a schematic plan view of the sensor layout in the embodiment of the present invention. Detailed Embodiment

[0045] To make the purpose, technical solution and advantages of the present invention clearer, the technical solution of the present invention will be described in detail below. Obviously, the described embodiments are only a 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 of ordinary skill in the art without creative work fall within the scope protected by the present invention.

[0046] The above specific embodiments are used to explain the present invention, rather than limit the present invention. Any modifications and changes made to the present invention within the scope of the gist and claims of the present invention fall within the protection scope of the present invention.

[0047] The monitoring area of a certain channel slope is 100 m, the distance between the ground surface of the slope and the bottom of the channel is 8 m, and the formation of the slope is homogeneous silty sand. Now, the stability of this channel slope under erosion conditions is evaluated:

[0048] First, it is necessary to design the sensor layout for this channel slope, specifically: the monitoring ranges of the pore water pressure sensors and earth pressure sensors are 15 m in the depth direction, 15 m in the direction perpendicular to the slope, and 100 m in the direction parallel to the slope; the monitoring densities of the pore water pressure sensors and earth pressure sensors are at intervals of 3 m in the depth direction, 5 m in the direction perpendicular to the slope, and 10 m in the direction parallel to the slope. A total of 220 pore water pressure sensors and earth pressure sensors are required. The downhole method is used for the shear wave velocity test. The shear wave excitation source is arranged at the center position of adjacent surface drill holes, and the geophones are placed along the drill holes at the same depth as the pore water pressure sensors and earth pressure sensors. The fixed monitoring points and non-fixed monitoring points are set at the middle positions between adjacent drill holes. Four non-fixed monitoring points and two fixed monitoring points are set in the direction perpendicular to the slope. The corresponding sensor layout is as Figure 2 shown.

[0049] Secondly, samples of the slope soil are taken to conduct in-door element tests, including shear tests under different void ratios, consolidation-shear wave velocity measurement tests, and hydraulic gradient tests under different void ratios. Among them, the shear test is used to obtain the quantitative correlation between the void ratio of the soil and the internal friction angle of the soil; the consolidation-shear wave velocity measurement test is used to obtain the A value and n value in Equation (3); the hydraulic gradient test is used to obtain the quantitative correlation between the critical hydraulic gradient and the void ratio of the soil.

[0050] Finally, carry out the combined monitoring of the slope instability failure under erosion conditions and calculate the corresponding safety factor:

[0051] (i) Monitor the change of the pore water pressure of the slope soil by arranging pore water pressure sensors at different positions and depths of the slope, and calculate the hydraulic gradients at different positions and depths according to Equation (1).

[0052]

[0053] In the formula: Δu is the difference in pore water pressure measured by two pore water pressure gauges; ρ w is the density of water; g is the acceleration due to gravity; L is the distance between two pore water pressure gauges.

[0054] The monitoring results of hydraulic gradients at different positions and depths can be used to draw the hydraulic gradient contour map of the slope area according to the linear interpolation method; based on the relationship between the hydraulic gradient contour map and the critical hydraulic gradient, the hydraulic gradient safety factor at different regional positions can be calculated according to Equation (6):

[0055]

[0056] In the formula: F w is the hydraulic gradient safety factor; i cr is the critical hydraulic gradient; i is the hydraulic gradient.

[0057] (ii) By arranging earth pressure sensors at different positions and depths of the slope to monitor the total earth pressure of the slope, combined with the monitoring results of pore water pressure at the same position, the effective stress of the soil at different positions and depths can be calculated according to Equation (2).

[0058] σ′ m = σ - u (2) In the formula: σ' m is the effective stress of the soil; σ is the monitoring result of earth pressure; u is the monitoring result of pore water pressure.

[0059] Carry out shear wave velocity monitoring to obtain the shear wave velocity of the slope soil at different positions and depths, and calculate the void ratio of the slope soil at different positions and depths according to Equation (3).

[0060]

[0061] In the formula: e is the void ratio of the soil; ρ is the density of the soil; V s is the measurement result of shear wave velocity; A is a material constant obtained by fitting the test results of indoor unit specimens; n is a constant describing the influence of stress on the shear wave velocity of the soil, determined by fitting the indoor unit specimen test.

[0062] Based on the quantitative correlation between the void ratio of the soil determined by indoor unit specimen tests and the internal friction angle of the soil, combined with Equation (4), calculate the shear strength of the soil at different positions and depths.

[0063]

[0064] In the formula: τ is the shear strength of the soil; is a function of the internal friction angle and void ratio of the soil; c' is the cohesion of the soil.

[0065] Use the monitoring results of the shear strength of the soil to draw the effective stress distribution contour map of the soil and calculate the overall anti-sliding safety factor of the slope soil, where the calculation method of the anti-sliding safety factor is shown in Equation (7):

[0066]

[0067] Where: K is the anti-slip safety factor; the subscript i indicates that the slope is divided into i blocks; l i is the sliding length at the bottom of the i-th block.

[0068] (iii) Conduct UAV photography on the surface of the slope, analyze the surface displacement field of the slope soil by comparing the pixel positions of non-fixed monitoring points in the images at different time periods, and calculate the distribution of the surface shear strain of the slope soil according to Equation (5); the change in pixel position is judged and measured based on the fixed monitoring points; then the monitoring results of the surface displacement field of the soil are used to draw the surface shear strain nephogram of the soil.

[0069]

[0070] Where: Δl is the surface deformation of the slope; L 0 is the initial distance of the surface measurement point.

[0071] Then, according to the monitoring results of (i)-(iii), determine the corresponding hierarchical prevention and control methods:

[0072] (1) When the safety factor of the hydraulic gradient is greater than 2, and the anti-slip safety factor is greater than 1.2, and the maximum surface shear strain is less than 0.01%, there is no need to reinforce the slope.

[0073] (2) When the safety factor of the hydraulic gradient is between 1 and 2, or the anti-slip safety factor is between 1 and 1.2, or the maximum surface shear strain is less than 0.01%, single reinforcement measures can be appropriately taken for the slope, including cutting and unloading, anchor reinforcement, and slope surface waterproofing.

[0074] (3) When the safety factor of the hydraulic gradient is between 0.95 and 1, or the anti-slip safety factor is between 0.9 and 1, or the maximum surface shear strain is between 0.01% and 0.1%, single or combined reinforcement measures must be taken for the slope, including cutting and unloading, anchor reinforcement, anti-slide pile reinforcement, grouting reinforcement of the erosion surface, and slope surface waterproofing.

[0075] (4) When the safety factor of the hydraulic gradient is less than 0.95, or the anti-slip safety factor is less than 0.9, or the maximum surface shear strain is greater than 0.1%, combined reinforcement measures must be immediately taken for the slope, including cutting and unloading, anchor reinforcement, anti-slide pile reinforcement, grouting reinforcement of the erosion surface, slope surface waterproofing, and post-slope precipitation of the slope.

[0076] The monitoring results of this waterway are as follows: the safety factor of the hydraulic gradient of the bank slope at the middle position of the waterway (width 40m) is 0.98, the anti-sliding safety factor is 1.1, and the maximum surface shear strain is 0.01%. These monitoring results indicate that there is no risk of landslide instability for the bank slope, but there is a certain risk of piping. Therefore, erosion surface grouting reinforcement is designed; the monitoring results at the end position of the waterway (width 20m) show that the safety factor of the hydraulic gradient is 1.05, the anti-sliding safety factor is 0.95, and the maximum surface shear strain is 0.05%. These monitoring results show that there is a slight risk of landslide instability but no risk of piping for the bank slope at the end of this waterway. Therefore, anchor rod reinforcement is designed; the monitoring results at the other end position of the waterway (width 40m) show that the safety factor of the hydraulic gradient is 1.05, the anti-sliding safety factor is 1.15, and the maximum surface shear strain is 0.01%. These monitoring results show that there is no risk of landslide instability and piping for the bank slope at the other end position of this waterway. In summary, it is necessary to adopt refined reinforcement with different regions and techniques for the bank slope of this waterway to achieve the best economic benefits.

Claims

1. A joint monitoring method for bank slope instability and failure under erosion conditions, characterized in that: The combined monitoring method includes monitoring of hydraulic gradient, monitoring of soil shear strength and monitoring of soil surface displacement field; The hydraulic gradient monitoring is performed by arranging pore water pressure sensors at different positions and depths of the bank slope to monitor the change of pore water pressure of the bank slope soil, and calculating the hydraulic gradients at different positions and depths according to formula (1); Where: Δu is the pore water pressure difference measured by two pore water pressure gauges; ρ w is the density of water; g is the acceleration of gravity; L is the distance between the two pore water pressure gauges; The soil shear strength monitoring combines indoor test results and slope soil monitoring indicators to evaluate the shear strength of slope soil at different depths, including soil pressure monitoring, shear wave velocity monitoring and indoor unit body testing; The soil pressure monitoring is performed by arranging soil pressure sensors at different positions and depths of the slope to monitor the total soil pressure of the slope, and combining the pore water pressure monitoring results at the same position to calculate the effective stress of the soil at different positions and depths according to formula (2); in m =σ-u (2) Where: σ' m is the effective stress of soil; σ is the monitoring result of soil pressure; u is the monitoring result of pore water pressure; The shear wave velocity monitoring is used to obtain the shear wave velocity of the bank slope soil at different positions and depths, and calculate the porosity ratio of the bank slope soil at different positions and depths according to formula (3); Where: e is the porosity of the soil; ρ is the density of the soil; V s is the shear wave velocity measurement result; A is the material constant, which is obtained by fitting the indoor unit body test results; n is the constant describing the influence of stress on the shear wave velocity of the soil, which is determined by fitting the indoor unit body test results; The indoor unit body test includes a shear test and a consolidation-shear wave velocity measurement test under different porosity ratio conditions, wherein the shear test is used to obtain the quantitative correlation between the soil porosity ratio and the soil internal friction angle, and the consolidation-shear wave velocity measurement test is used to obtain the A value and the n value in formula (3); Combining the indoor unit test results and the slope soil measurement indicators, the shear strength of the soil at different positions and depths is calculated according to formula (4); Where: τ is the shear strength of the soil; is the function of the internal friction angle and porosity ratio of the soil; c' is the cohesion of the soil; The soil surface displacement field monitoring is performed by setting a plurality of fixed and non-fixed monitoring points on the surface, then taking photos of the surface, analyzing the surface displacement field of the slope soil by comparing the pixel positions of the non-fixed monitoring points in the images of different time periods, and calculating the surface shear strain distribution of the slope soil according to formula (5); the pixel position change is judged and measured based on the fixed monitoring points; Where: Δl is the surface deformation of the slope; L0 is the initial distance of the surface measurement point.

2. The joint monitoring method according to claim 1, characterized in that: The hydraulic gradient monitoring results at different positions and depths can be used to draw the hydraulic gradient cloud map of the slope area according to the linear interpolation method; hydraulic gradient tests under different porosity conditions are carried out to obtain the relationship between the critical hydraulic gradient and the porosity when the soil body is damaged by piping; based on the relationship between the hydraulic gradient cloud map and the critical hydraulic gradient, the hydraulic gradient safety factor at different regional positions is calculated according to formula (6): Where: F w is the hydraulic gradient safety factor; i cr is the critical hydraulic gradient; i is the hydraulic gradient.

3. The joint monitoring method according to claim 1, characterized in that: The soil shear strength monitoring results are used to draw the soil effective stress distribution cloud map and calculate the overall anti-sliding safety factor of the slope soil. The anti-sliding safety factor calculation method is shown in formula (7): Where: K is the anti-sliding safety factor; the subscript i indicates that the slope is divided into i strips; l i is the bottom sliding length of the i-th bar.

4. The joint monitoring method according to claim 1, characterized in that: The monitoring result of the soil surface displacement field is used to draw a soil surface shear strain cloud map; the soil surface displacement field monitoring can be implemented by drone aerial photography or obtained by taking photos with a camera at a fixed height.

5. The joint monitoring method according to claim 1, characterized in that: The shear wave velocity monitoring can be implemented by the surface wave method, the down-hole method and the cross-hole method; when the down-hole method and the cross-hole method are used for measurement, the shear wave detector needs to be placed in the borehole and be consistent with the burial depth of the pore water pressure sensor and the soil pressure sensor.

6. The joint monitoring method according to claim 1, characterized in that: The pore water pressure sensor and soil pressure sensor are buried in the soil of the slope through drilling and are located at the same depth; the monitoring density of the pore water pressure sensor and the soil pressure sensor is: the monitoring distance in the depth direction exceeds 5m from the bottom of the slope, and the monitoring interval does not exceed 3m; the monitoring distance in the direction perpendicular to the slope is consistent with that in the depth direction, and the monitoring interval does not exceed 5m; the monitoring distance along the slope is related to the engineering requirements, and the monitoring interval does not exceed 10m; the starting points of the monitoring distances are all the tops of the slope.

7. The joint monitoring method according to claim 1, characterized in that: The stratum types of the slope soil body include one or more of clay, clay silt, clay sand, silt, silty clay, silty sand, sand, sandy clay, sandy silt, sandy gravel, gravel soil, and gravelly sand.

8. A method for preventing and controlling bank slope instability based on claim 1, characterized in that: The hierarchical prevention method includes the following parts: (1) When the hydraulic gradient safety factor is greater than 2, the anti-sliding safety factor is greater than 1.2, and the maximum surface shear strain is less than 0.01%, there is no need to reinforce the slope; (2) When the hydraulic gradient safety factor is between 1 and 2, or the anti-sliding safety factor is between 1 and 1.2, or the maximum surface shear strain is less than 0.01%, a single reinforcement measure can be appropriately adopted for the bank slope, including cutting to reduce load, anchor reinforcement, and bank slope surface waterproofing; (3) When the hydraulic gradient safety factor is between 0.95 and 1, or the anti-sliding safety factor is between 0.9 and 1, or the maximum surface shear strain is between 0.01% and 0.1%, single or combined reinforcement measures shall be taken for the slope, including cutting and unloading, anchor reinforcement, anti-sliding pile reinforcement, grouting reinforcement of the eroded surface, and slope surface waterproofing; (4) When the hydraulic gradient safety factor is less than 0.95, or the anti-sliding safety factor is less than 0.9, or the maximum surface shear strain is greater than 0.1%, a combination of reinforcement measures must be taken immediately for the slope, including cutting to reduce load, anchor reinforcement, anti-sliding pile reinforcement, grouting reinforcement of the erosion surface, slope surface waterproofing, and slope backwatering.

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