Monitoring and early warning method for geological disasters in slope unit based on fixed-point aerial survey of unmanned aerial vehicle

Abstract

The invention provides a monitoring and early warning method for geological disasters in a slope unit based on fixed-point aerial survey of an unmanned aerial vehicle, and belongs to the technical field of geological disaster monitoring. Comprising the following steps: S1, geological survey; s2, establishing a coordinate system; s3, arranging a marker; s4, calculating an original coordinate; s5, collecting periodic data; s6, analyzing the collected data; s7, monitoring result early warning; obtaining an average displacement value a of landslide mass markers, an azimuth angle alpha and a pitch angle beta in the main direction, an average value b of components of the markers displaced in the main direction, and an average angle theta deviating from the main direction; the landslide risk is judged according to the analysis of the monitoring data, and early warning is given in time. According to the method, the unmanned aerial vehicle is used for fixed-point aerial survey, the spatial three-dimensional coordinates are established, the displacement parameters of the landslide mass are quantitatively analyzed by calculating the spatial displacement of the marker, an early warning value is given, the problems of monitoring limitation and difficult quantification are solved, the operation process is simple, only data need to be collected, and a result is automatically generated through a program.

Description

TECHNICAL FIELD

[0001] The application provides a slope unit internal geological disaster monitoring and early warning method based on unmanned aerial vehicle fixed-point aerial survey, and belongs to the technical field of geological disaster monitoring. BACKGROUND

[0002] There are many monitoring and early warning methods for the slope unit internal geological disaster, mainly including the following methods:

[0003] Ground deformation monitoring: observation piles, inclinometers and the like are arranged in the landslide body and the periphery, and displacement, settlement and other data are measured regularly, so that the moving trend of the landslide body can be directly understood. The leveling measurement can accurately obtain the elevation change to determine whether there is subsidence; the total station can monitor the horizontal displacement to analyze the sliding direction and speed of the landslide body.

[0004] Underground deformation monitoring: with the help of a borehole inclinometer, the deformation of soil or rock mass at different depths is monitored in the underground to understand the position and development of the potential sliding surface.

[0005] Groundwater monitoring: water level observation wells are arranged in the landslide area to monitor the change of the groundwater level. The rise of the water level will increase the weight of the soil and reduce the shear strength, thereby causing the landslide. The change of the water quality can also be analyzed to infer the erosion and softening effect of the underground water activity on the rock-soil body.

[0006] Satellite remote sensing and aerial photogrammetry: satellite remote sensing can obtain information of a large area, and through multi-temporal image comparison, potential landslide signs such as surface deformation and vegetation change can be analyzed. Aerial photogrammetry can provide high-resolution images, stereoscopic observation and interpretation of topography, and identification of early micro-topographic features of landslides.

[0007] These methods generally have the problems of range limitation and difficulty in quantification. The deformation monitoring means or groundwater level monitoring means can only quantitatively study the local deformation and cannot be expanded to the entire landslide body, and the satellite remote sensing and aerial photogrammetry can only be analyzed in the plane and cannot be expanded to the three-dimensional space. In addition, they are difficult to quantitatively analyze the overall motion of the landslide body. SUMMARY

[0008] The application provides a slope unit internal geological disaster monitoring and early warning method based on unmanned aerial vehicle fixed-point aerial survey, and belongs to the technical field of geological disaster monitoring.

[0009] The specific technical scheme is as follows:

[0010] The slope unit internal geological disaster monitoring and early warning method based on unmanned aerial vehicle fixed-point aerial survey comprises the following steps:

[0011] S1. Geological survey

[0012] The geological survey includes identifying dangerous areas and determining the boundaries of dangerous areas;

[0013] (1) Landslide body identification

[0014] Landslide body identification can be carried out by the following traditional geological survey methods:

[0015] ① Topography

[0016] Mountain slope shape: If there are circle chair-shaped, horseshoe-shaped topography on the mountain slope, or there are sudden changes in slope, it may be a potential landslide.

[0017] Gully features: Pay attention to whether the gully has double-gully homology, gully wall has obvious scratches or terrace discontinuity, etc. If so, there may be potential landslides.

[0018] Abnormal slope surface: Local pits, kip, or a large number of loose accumulations on the slope surface may indicate potential landslide risks.

[0019] ② Rock and soil mass characteristics

[0020] Rock fragmentation: If the rock joints and cracks are well developed, broken, or the soil is loose, the particle size is mixed, and the stability is poor, landslides are likely to occur.

[0021] Stratigraphic dislocation: If there are obvious dislocations, distortions, and inversions of old and new strata, it may be a sign of potential landslides.

[0022] ③ Surface and vegetation

[0023] Surface cracks: Parallel or arc-shaped cracks appear on the surface of the mountain slope, especially when tensile and shear cracks exist at the same time, which may be a potential landslide.

[0024] Abnormal vegetation: Trees are tilted and shaped like "drunkard forest" and "sword tree", or the growth of vegetation is significantly different, such as sparse or dead vegetation in some areas, which may be related to potential landslides.

[0025] (2) Landslide perimeter determination

[0026] The main methods for identifying the perimeter of a landslide are as follows:

[0027] ① Geological and geomorphological identification method

[0028] Macroscopic geomorphic features: From a distance, if the slope has relatively low concave circle chair-shaped, horseshoe-shaped topography, or double-gully homology, there may be a landslide, and the boundary of the circle chair-shaped or horseshoe-shaped topography is often the perimeter of the landslide.

[0029] Micro-landform features: Close-up view, the back edge of the landslide often forms a concave or landslide lake, both sides have shear feather cracks, the front edge has bulging and longitudinal cracks, protruding landslide tongue, etc. The boundary of these special landforms can be determined as the perimeter of the landslide.

[0030] ②Stratigraphic lithology identification method

[0031] Sequence and occurrence: The strata of the landslide body are often disturbed during the sliding process, the sequence is chaotic, the structure is loose, and compared with the non-sliding slope section, the occurrence may also be discontinuous, and abnormal conditions such as new and old strata inversion may occur. The landslide perimeter can be divided according to this.

[0032] Rock-soil mass characteristics: The rock-soil mass of the landslide body will be loose and broken due to sliding, which is obviously different from the surrounding complete rock-soil mass, and can be used as a basis for identifying the perimeter of the landslide.

[0033] ③Surface crack identification method

[0034] Crack morphology: The back edge of the landslide is generally a tensile crack, which is in the form of a circle chair; the side boundary is a shear feather crack; the front edge is a bulging and longitudinal crack. Tracking the extension range of these cracks can roughly determine the perimeter of the landslide.

[0035] Crack development: Observing whether the cracks have a trend of lengthening and widening, and the extension direction of the newly appeared cracks or the original cracks can also help determine the extension range and perimeter of the landslide.

[0036] S2. Coordinate system establishment

[0037] Analyze the surface morphology of the landslide body and find the geometric center point. Draw a vertical line through the center point perpendicular to the slope surface. Fly the unmanned aerial vehicle carrying RTK and laser radar along the vertical line from near to far. As the distance increases, the lens will first meet two conditions, one is that the maximum upward angle of the lens is higher than or parallel to the top edge of the landslide body, and the other is that the downward direction of the lens exceeds or is parallel to the bottom edge of the landslide body. When the lens meets the above two conditions at the same time, determine that the body at this time is the origin O of the three-dimensional coordinate system, and record the geodetic coordinates and elevation of point O using RTK. The origin O point is the nearest point on the vertical line where the landslide body completely enters the lens field of view, and the north-south direction of the coordinate system is the x-axis, the east-west direction is the y-axis, and the up-down direction is the z-axis.

[0038] S3. Marker arrangement

[0039] The marker is composed of a small locator and a red ball on it, and the displacement of the red ball is equal to the surface displacement at the location.

[0040] The markers are arranged in a grid shape, but not at equal intervals, but at equal angular intervals.

[0041] According to the size of the landslide and the top-bottom span of the landslide relative to the original point O, the reasonable number of markers n is determined, and then the lens angle interval is calculated. Assuming that the top-bottom span of the landslide is 100°, 10 markers are arranged between the upper and lower edges of the landslide, and the angle interval is 10°.

[0042] The unmanned aerial vehicle is lifted to the original point, the body azimuth angle is consistent with the slope strike, the lens direction is consistent with the vertical line, the pitch angle is adjusted, and the lens focal point is directly opposite the center of the landslide.

[0043] The body azimuth angle and the lens pitch angle are adjusted, the lens focal point is determined in a series of angle intervals along the southeast, southwest and northwest directions from the midpoint, and the direction of each marker is determined until it is about to exceed the perimeter of the landslide. The data of each direction, i.e. the body azimuth angle α and the lens pitch angle β, are recorded. When each direction is determined, the lens is zoomed in to the maximum distance, a high-definition photo is taken, and the lens focal point is the placement position of the marker. These points are arranged in order according to the serial number from 1 to n.

[0044] The markers are placed according to the focal point positions of the above series of photos, and the unmanned aerial vehicle is lifted to the original point O again, and the laser radar is turned on to measure the distance d from the original point O to each red ball.

[0045] S4. Original coordinate calculation

[0046] Through the above operation, the azimuth angle α, the pitch angle β (the pitch angle is negative and the elevation angle is positive) and the distance d of each marker relative to the original point are obtained, and the original coordinates of each marker can be calculated accordingly. According to the trigonometric relationship in three-dimensional space, the coordinates of a point are: (d·cosα·cosβ, d·sinα·cosβ, d·sinβ).

[0047] For n markers, given α, β and d, the three sets of data can be imported into an excel table, each as a column. Then use programming to solve it with one key, and output all point coordinates in the form of an excel table.

[0048] S5. Periodic data acquisition

[0049] Landslide monitoring needs regular data acquisition and analysis.

[0050] The unmanned aerial vehicle is lifted to the original point, the body azimuth angle is consistent with the slope strike, and the lens is aligned with the vertical point. The body azimuth angle and the lens pitch angle are adjusted, and the lens is moved along the southeast, southwest and northwest directions at an angle interval. Taking the maximum image focal point of the original lens in each direction as the starting point, the red ball position deviating from the center is found. The focal point is re-aligned with the red ball, the new azimuth angle α' and the pitch angle β' are read, and the new distance d' is measured by the laser range finder. The new coordinates of the marker can be calculated accordingly. Assuming that the original coordinates of a marker are (x0, y0, z0), the new coordinates of the marker after i periods of interval are (x i , yi , z i ), then the displacement vector of the i-th marker in the first cycle is (x i -x0, y i -y0, z i -z0), and the displacement vector of the adjacent two cycles is (x i -x i-1 , y i -y i-1 , z i -z i-1 ).

[0051] S6. Data analysis

[0052] Let the displacement vector of the n markers in the adjacent two cycles be where n' is the number of non-zero vectors.

[0053] If n' < 1 / 2, it indicates that the landslide body may only have local displacement, and further geological investigation is needed. Determine the investigation range according to the distribution range of the non-zero marker number, and investigate two issues: ① Whether the rock-soil in this area is heterogeneous or has special topography or special structure compared to other areas; ② Whether the rock-soil movement in this area has an impact on the stability of rock-soil in other areas, if it does, discuss it together with n' ≥ 1 / 2.

[0054] If n' ≥ 1 / 2, it indicates that the local displacement has affected the whole, driving the whole displacement. At this time, the direction and size of the landslide body displacement need to be determined.

[0055] The degree of displacement of the landslide body is represented by the average value of the modulus of the non-zero vector of the marker.

[0056] The landslide has a main direction, but the direction of a single marker may deviate to varying degrees, and the main direction can be fitted with all non-zero displacement vectors and converted into azimuth and pitch angle.

[0057] The size of the whole landslide displacement is the average value of the modulus of the component in the main direction of each non-zero vector.

[0058] The degree of deviation of each marker from the main direction can reflect the shape of the landslide body, and the degree of deviation can be represented by the average of the angle between each marker vector and the main direction vector. The solving process is as follows:

[0059] ① The displacement vector of a certain marker is then the modulus of the vector is

[0060] Calculate this value for n' non-zero vectors, and then take the average.

[0061] 2. Calculate the covariance matrix of the n' non-zero vectors, and solve its eigenvalues and eigenvectors. The direction of the eigenvector corresponding to the largest eigenvalue is the principal direction. Let the principal direction vector be After that, the azimuth angle a and the pitch angle b can be calculated by the formula: a = arctan2(y, x),

[0062] 3. The displacement vector of a certain marker The modulus of the projection of the vector on the principal direction is Calculate this value for all non-zero vectors, and then take the average.

[0063] 4. The displacement vector of a certain marker Given the principal direction vector The angle between the two vectors is Calculate this value for all non-zero vectors, and then take the average.

[0064] S7. Monitoring result warning

[0065] In the above process, the average displacement value a of the landslide markers, the azimuth angle a and the pitch angle b of the principal direction, the average value b of the displacement component of the markers along the principal direction, and the average angle θ deviating from the principal direction are obtained.

[0066] When a < 5 cm, the landslide body is relatively stable, and the surface rock-soil layer undergoes normal displacement changes under natural conditions such as wind and water; when 5 ≤ a < 20 cm, relative movement has occurred within the landslide body, accompanied by the appearance of cracks, and the landslide front is obviously deformed, with a large landslide hazard, and residents within the influence range of the landslide area need to be relocated; when a ≥ 20 cm, the landslide body has a significant landslide hazard and may slide at any time, and residents must be relocated immediately.

[0067] When 0 < b < 5 cm, the landslide body has a safety hazard; when b ≥ 5 cm, it has a significant safety hazard and residents need to be relocated immediately.

[0068] When θ < 10°, the landslide body slides in one direction as a whole, and the expansion angle of the two sides does not exceed 20°, showing linear sliding, in which case the potential disaster area is smallest but the destructive power is the largest; when 10° < θ < 30°, the landslide body slides in a small fan shape, and the expansion angle of the two sides is between 20° and 60°, in which case the potential disaster area is medium and the destructive power is medium; when θ > 30°, the landslide body slides in a large fan shape, and the expansion angle of the two sides is greater than 60°, in which case the potential disaster area is the largest and the destructive power is the weakest.

[0069] According to the analysis of the above monitoring data, the landslide risk is judged, and timely warning is made. BRIEF DESCRIPTION OF DRAWINGS

[0070] Figure 1 is a schematic diagram of a landslide body;

[0071] Figure 2 Layout diagram of the marker points of the present application. DETAILED DESCRIPTION

[0072] The specific technical solutions of the present application are described in conjunction with the drawings.

[0073] The slope unit internal geological disaster monitoring and early warning method based on unmanned aerial vehicle fixed-point aerial survey includes the following steps:

[0074] S1. Geological survey

[0075] The purpose of geological survey is twofold: one is to identify dangerous areas such as landslide bodies, and the other is to determine the boundaries of dangerous areas such as landslide body ranges, as shown in Figure 1

[0076] (1) Landslide body identification

[0077] Landslide body identification can be carried out by the following traditional geological survey methods:

[0078] ① Topography

[0079] Mountain slope shape: If there are circle chair-shaped, horseshoe-shaped topography on the mountain slope, or there are sudden changes in slope, it may be a potential landslide.

[0080] Gully features: Pay attention to whether the gully has double-gully homology, gully wall has obvious scratches or terrace discontinuity, etc. If there are, there may be potential landslides.

[0081] Abnormal slope surface: Local pits, kip, or a large number of loose accumulations on the slope surface may indicate potential landslide risks.

[0082] ② Rock-soil mass characteristics

[0083] Rock fragmentation: If the rock joint fissure is developed, broken, or the soil is loose, the particle size is mixed, the stability is poor, and the landslide is easy to occur.

[0084] Stratigraphic dislocation: If the stratum has obvious dislocation, distortion, new and old stratum inversion, etc., it may be a sign of potential landslide.

[0085] ③ Surface and vegetation

[0086] Surface cracks: Parallel or arc-shaped cracks appear on the surface of the mountain slope, especially when tensile cracks and shear cracks exist at the same time, which may be a potential landslide.

[0087] Abnormal vegetation: Trees are tilted and show "drunkard forest" and "sword tree" shapes, or the vegetation growth conditions are obviously different, such as local sparse or dead vegetation, which may be related to potential landslides.

[0088] ​(2) Landslide perimeter determination

[0089] The methods for identifying the perimeter of a landslide mainly include the following:

[0090] ① Geologic and geomorphic identification method

[0091] Macro-geomorphic features: From a distance, if there are relatively low concave circle-chair-shaped or horseshoe-shaped landforms or double-gully co-origin phenomena on the slope, a landslide may exist, and the perimeter of the circle-chair-shaped or horseshoe-shaped landform is often the perimeter of the landslide.

[0092] Micro-geomorphic features: At close range, a concave land or landslide lake is often formed at the rear edge of the landslide, and there are shear feather-shaped cracks on both sides and bulging and longitudinal cracks, protruding landslide tongues at the front edge, and the perimeter of these special landforms can be determined as the perimeter of the landslide.

[0093] ② Stratum and lithology identification method

[0094] Stratum sequence and occurrence: The stratum of the landslide body is often disturbed during sliding, and the sequence is relatively chaotic and the structure is loose, compared with the slope section that has not slid, the occurrence may also be discontinuous, and abnormal conditions such as inversion of old and new strata may occur, which can be used to divide the perimeter of the landslide.

[0095] Rock-soil body characteristics: The rock-soil body of the landslide will be loose and broken due to sliding, which is obviously different from the surrounding complete rock-soil body, and can be used as a basis for identifying the perimeter of the landslide.

[0096] ③ Surface crack identification method

[0097] Crack morphology: The rear edge of the landslide is generally a tensile crack, which is circle-chair-shaped; the side boundary is a shear feather-shaped crack; and the front edge is a bulging and longitudinal crack. Tracking the extension range of these cracks can roughly determine the perimeter of the landslide.

[0098] Crack development: Observing whether the cracks have a trend of lengthening and widening, and the extension direction of the newly appeared cracks or the original cracks can also help determine the extension range and perimeter of the landslide.

[0099] S2. Coordinate system establishment

[0100] Analyze the surface morphology of the landslide body and find the geometric center point. Draw a vertical line perpendicular to the slope surface through the center point. Fly the unmanned aerial vehicle carrying RTK and laser radar along the vertical line from near to far, and as the distance increases, the lens will first meet two conditions, one is that the maximum upward angle of the lens is higher than or parallel to the top edge of the landslide body, and the other is that the downward direction of the lens is beyond or parallel to the bottom edge of the landslide body. When the lens meets the above two conditions at the same time, determine that the body at this time is the origin O of the three-dimensional coordinate system, and record the geodetic coordinates and elevation of point O using RTK. The origin O point is the nearest point on the vertical line where the landslide body completely enters the lens field of view, and the north-south direction of the coordinate system is the x-axis, the east-west direction is the y-axis, and the up-down direction is the z-axis.

[0101] S3. Marker placement

[0102] like Figure 2 As shown, the marker consists of a small locator and a red ball on it. The displacement of the red ball is equal to the displacement of the ground at its location.

[0103] The markers are arranged in a grid pattern, but not at equal intervals, but at equal angles. This design allows the drone to quantitatively rotate the azimuth and pitch angles and quickly collect information. Secondly, the angle change caused by displacement close to the origin is large, while the angle change caused by displacement far from the origin is small, which leads to a relatively larger calculation error. The use of equal angle spacing to arrange the grid essentially increases the number of markers in the middle area of ​​the landslide and reduces the number of markers in the surrounding area, which can reduce the calculation error. Figure 2 .

[0104] The optimal number of markers, n, is determined based on the size of the landslide and its top-to-bottom span relative to the origin, O. This allows for the calculation of the lens angle interval. For example, if the top-to-bottom span of the landslide is 100° and 10 markers are designed to be placed between the top and bottom edges of the landslide, the angle interval is 10°.

[0105] Lift the drone to the origin, align the azimuth angle of the fuselage with the direction of the slope, face the slope, align the direction of the lens with the vertical line, adjust the pitch angle, and focus the lens on the center of the landslide.

[0106] Adjust the aircraft's azimuth and lens pitch angles. Starting from the midpoint, focus the lens in the east, south, west, and north directions at a series of angular intervals until you're just beyond the landslide perimeter. Record the data for each direction: the aircraft's azimuth angle α and the lens's pitch angle β. After each direction is determined, zoom in as close as possible and take a high-definition photo. The lens's focus will be the marker's location. These points are numbered from 1 to n.

[0107] Place all the markers according to the focal positions of the above series of photos, launch the drone to the origin O again, turn on the lidar, and measure the distance d from point O to each red ball.

[0108] S4. Original coordinate calculation

[0109] Through the above operations, we obtain the azimuth angle α, pitch angle β (pitch angle is negative, elevation angle is positive), and distance d of each marker relative to the origin. Based on these, we can calculate the original coordinates of each marker. According to the trigonometric function relationship in three-dimensional space, the coordinates of a point are: (d·cosα·cosβ, d·sinα·cosβ, d·sinβ).

[0110] For n markers, known corresponding a, b, d, can be imported into excel table, each column. Then use programming one key solution, with excel table form output all point coordinates, reference the following Python code:

[0111]

[0112]

[0113] S5. Periodic data collection

[0114] Landslide monitoring needs regular data collection, analysis of changes, the cycle is usually a month.

[0115] The unmanned aerial vehicle to the origin, the body azimuth and the slope consistent, the lens pointing to the vertical point. Adjust the body azimuth and lens pitch angle, along the east, south, west, north direction with angle interval. With the original each direction lens maximum image focus as the starting point, find the red ball position deviated from the center. Realign the focus to the red ball, read the new azimuth a' and pitch angle b', and use the laser range finder to measure the new distance d'. Can be calculated according to the new coordinates of the marker. Assuming that the original coordinates of a certain marker is (x0, y0, z0), the new coordinates of the interval i period is (x i , y i , z i ), the displacement vector of each marker in the i period is (x i -x0, y i -y0, z i -z0), the displacement vector of adjacent two period markers is (x i -x i-1 , y i -y i-1 , z i -z i-1 ).

[0116] S6. Data collection and analysis

[0117] Let n markers in adjacent two period displacement vector is Where, the number of non-zero vector is n'.

[0118] If n' <1 / 2, it means that the landslide may only have local displacement, at this time need further geological investigation. According to the distribution range of non zero marker number to determine the investigation range, investigate two problems: ① whether the rock and soil in this area and other areas exist inhomogeneity or special topography, special structure; ② whether the rock and soil movement in this area has influence on the stability of other areas, if there is influence, then discuss together with n' >=1 / 2.

[0119] If n'≥1 / 2, it means that the local displacement has affected the whole, driving the whole displacement. At this time, the direction and size of the landslide displacement need to be determined.

[0120] The displacement degree of the landslide is represented by the average value of the modulus of the non-zero vector of the marker.

[0121] The landslide has a main direction, but the direction of individual markers will deviate to varying degrees, and the main direction can be fitted with all non-zero displacement vectors and converted into an azimuth angle and a pitch angle.

[0122] The size of the whole landslide displacement is the average value of the modulus of the component of each non-zero vector in the main direction.

[0123] The degree of deviation of each marker from the main direction can reflect the shape of the landslide, and the degree of deviation can be represented by the average of the angle between the vector of each marker and the main direction vector. The solving process is as follows:

[0124] ① The displacement vector of a certain marker Then the modulus of the vector is

[0125] Calculate this value for n' non-zero vectors, and then take the average.

[0126] ② Calculate the covariance matrix of n' non-zero vectors, and solve its eigenvalues and eigenvectors. The direction of the eigenvector corresponding to the largest eigenvalue is the fitted main direction. Let the main direction vector be Then the azimuth angle α and the pitch angle β value can be calculated by the formula: α = arctan2(y, x),

[0127] ③ The displacement vector of a certain marker The modulus of the vector projected in the main direction is Calculate this value for all non-zero vectors, and then take the average.

[0128] ④ The displacement vector of a certain marker Given the main direction vector Then the angle between the two vectors is Calculate this value for all non-zero vectors, and then take the average.

[0129] The above steps can be implemented through Python language:

[0130]

[0131]

[0132] S7. Monitoring results warning

[0133] In the above process, the average displacement value a of the landslide marker, the azimuth angle α and the pitch angle β of the main direction, the average value b of the component of the marker displacement along the main direction, and the average angle θ deviating from the main direction are obtained.

[0134] When a < 5 cm, the landslide body is relatively stable, and the surface rock-soil layer changes normally under natural conditions such as geomancy; when 5 ≤ a < 20 cm, relative movement has occurred in the landslide body, accompanied by the appearance of cracks, and the landslide front is obviously deformed, with a large landslide hazard, and residents in the influence range of the landslide area need to be relocated; when a ≥ 20 cm, the landslide body has a major landslide hazard and may slide at any time, and residents must be relocated immediately.

[0135] When 0 < b < 5 cm, the landslide body has a safety hazard; when b ≥ 5 cm, it has a major safety hazard, and residents need to be relocated immediately.

[0136] When θ < 10°, the landslide body slides in one direction as a whole, and the expansion angle of the two sides does not exceed 20°, showing linear sliding, at this time the potential disaster area is the smallest, but the destructive power is the largest; when 10° < θ < 30°, the landslide body slides in a small fan shape, and the expansion angle of the two sides is between 20° and 60°, at this time the potential disaster area is medium, and the destructive power is medium; when θ > 30°, the landslide body slides in a large fan shape, and the expansion angle of the two sides is greater than 60°, at this time the potential disaster area is the largest, and the destructive power is the weakest.

[0137] According to the analysis of the above monitoring data, the landslide risk is judged, and timely warning is made.

Claims

1. A method for monitoring and early warning of geological hazards within slope units based on fixed-point aerial survey by unmanned aerial vehicles, characterized in that: The following steps are involved: S1. Geological survey, including identification of hazardous areas and determination of their boundaries; S2. Coordinate system establishment; Analyze the surface morphology of the landslide and find its geometric center. Draw a vertical line perpendicular to the slope through the center. Fly a drone equipped with RTK and LiDAR along this vertical line from near to far. The camera must meet two conditions: the maximum elevation angle of the lens is above or parallel to the top edge of the landslide, and the vertical downward direction of the lens exceeds or is parallel to the bottom edge of the landslide. When the camera meets both conditions, the aircraft is determined to be the origin O of the three-dimensional coordinate system, and the geodetic coordinates and elevation of point O are recorded using RTK. Origin O is the closest point on the vertical line where the landslide is completely within the camera's field of view. The north and south of the coordinate system are the x-axis, the east and west are the y-axis, and the top and bottom are the z-axis. S3. Marker placement; The markers consist of a small locator and a red ball on top; the markers are arranged in a grid pattern, with equal angles between them; S4. Calculation of original coordinates; Obtain the azimuth angle α, pitch angle β, and distance d of each marker relative to the origin, and calculate the original coordinates of each marker based on these; S5. Periodic data collection; Landslide monitoring requires regular data collection and analysis of changes; S6. Data collection and analysis; The displacement degree of the landslide body is expressed by the average value of the modulus of the non-zero vector of the marker; The landslide has a main direction, which is fitted by all non-zero displacement vectors and converted into azimuth and pitch angles; The overall displacement of the landslide is the average value of the magnitude of the components of each non-zero vector in the main direction; The degree of deviation of each marker from the main direction reflects the shape of the landslide body. The degree of deviation is expressed by the average of the angles between each marker vector and the main direction vector. S7. Early warning of monitoring results; Obtain the average displacement value a of the landslide marker, the azimuth angle α and pitch angle β of the main direction, the average value b of the components of the marker displacement along the main direction, and the average angle θ that deviates from the main direction; Determine the landslide risk based on the analysis of monitoring data and issue timely warnings.

2. The method for monitoring and early warning of geological disasters in slope units based on fixed-point aerial survey by unmanned aerial vehicles according to claim 1 is characterized in that: The S3 specific method is: According to the scale of the landslide and the span of the top and bottom of the landslide relative to the origin O, the reasonable number of markers n is determined, and then the lens angle interval is calculated; Lift the drone to the origin, align the azimuth of the fuselage with the direction of the slope, face the slope, align the camera direction with the vertical line, adjust the pitch angle, and focus the camera on the center of the landslide; Adjust the azimuth angle of the aircraft and the pitch angle of the lens, and focus the lens from the midpoint along the east, south, west and north directions at a series of angle intervals to determine the direction of each marker until it is about to exceed the perimeter of the landslide; Record the data for each direction, namely the azimuth angle α of the fuselage and the pitch angle β of the lens. When each direction is determined, zoom in the lens at the maximum distance and take a high-definition photo. The lens focus is the location of the marker. These points are numbered from 1 to n. Place all the markers according to the focal positions of the above series of photos, launch the drone to the origin O again, turn on the lidar, and measure the distance d from point O to each red ball.

3. The method for monitoring and early warning of geological disasters in slope units based on fixed-point aerial survey by unmanned aerial vehicles according to claim 1 is characterized in that: The specific method of S4 is that according to the relationship between the trigonometric functions in three-dimensional space, the coordinates of a point are: (d·cosα·cosβ, d·sinα·cosβ, d·sinβ); For n markers, the corresponding α, β, and d are known. Import the three sets of data into an Excel table, each in a column; then use programming to solve with one click and output the coordinates of all points in the form of an Excel table.

4. The method for monitoring and early warning of geological disasters in slope units based on fixed-point aerial survey by unmanned aerial vehicles according to claim 1 is characterized in that: The specific method of S5 is: Raise the drone to the origin, align the fuselage azimuth with the slope direction, and aim the lens at the vertical point. Adjust the fuselage azimuth and lens pitch angle, and move in angular intervals along the east, south, west, and north directions. Starting from the original maximum image focus of the lens in each direction, find the position of the red ball that is off-center. Refocus on the red ball, read the new azimuth angle α' and pitch angle β', and use the laser rangefinder to measure the new distance d'; calculate the new coordinates of the marker based on this; The original coordinates of a marker are (x0, y0, z0), and the new coordinates after an interval of i periods are (x i ,y i , z i ), then the displacement vector of each marker in the i-th period is (x i -x0,y i -y0,z i -z0), the displacement vector of two adjacent periodic markers is (x i -x i-1 ,y i -y i-1 , z i -z i-1 ).

5. The method for monitoring and early warning of geological disasters in slope units based on fixed-point aerial survey by unmanned aerial vehicles according to claim 1 is characterized in that: In S6, let the displacement vector of n markers in two adjacent periods be Among them, the number of non-zero vectors is n'; If n' is less than 1 / 2, it indicates that only local displacement of the landslide mass may have occurred. Further geological investigation is required. The scope of investigation is determined based on the distribution range of the non-zero marker numbers. Two questions should be investigated: ① Whether the rock and soil in this area are heterogeneous or have special topography or special structures compared with other areas; ② Whether the rock and soil movement in this area affects the stability of the rock and soil in other areas. If so, this should be discussed together with the case of n' ≥ 1 / 2. If n'≥1 / 2, it means that the local displacement has affected the whole and driven the overall displacement; at this time, it is necessary to determine the direction and magnitude of the landslide displacement.

6. The method for monitoring and early warning of geological disasters in slope units based on fixed-point aerial survey by unmanned aerial vehicles according to claim 5 is characterized in that: The process of solving the average of the angles between each marker vector and the main direction vector is as follows: ① Displacement vector of a marker Then the modulus of the vector is Calculate this value for n' non-zero vectors and then find the average; ② Calculate the covariance matrix of n' non-zero vectors and solve their eigenvalues ​​and eigenvectors; the direction of the eigenvector corresponding to the maximum eigenvalue is the main direction of the fitting; let the main direction vector be After that, the azimuth angle α and pitch angle β are calculated by the formula: α=arctan2(y,x), ③ Displacement vector of a marker The magnitude of the projected vector in the principal direction is Calculate this value for all non-zero vectors and then find the average; ④ Displacement vector of a marker The main direction vector is known to be The angle between the two vectors is This value is calculated for all non-zero vectors and then averaged.

7. The method for monitoring and early warning of geological disasters in slope units based on fixed-point aerial survey by unmanned aerial vehicles according to claim 1, characterized in that: In S7: When a is less than 5 cm, the landslide body is relatively stable, and the surface rock and soil layers are subject to normal displacement changes under natural conditions. When 5 ≤ a < 20 cm, relative movement has occurred within the landslide body, accompanied by the appearance of cracks and obvious deformation of the landslide front. This poses a significant landslide hazard, and residents within the affected area need to be relocated. When a ≥ 20 cm, the landslide body has a significant landslide hazard and may collapse at any time, and residents must be relocated immediately. When 0 < b < 5 cm, the landslide body poses a safety hazard; when b ≥ 5 cm, it poses a major safety hazard and residents must be evacuated immediately; When θ is less than 10°, the landslide body slides in one direction as a whole, and the expansion angle of the boundaries on both sides does not exceed 20°, showing linear sliding. At this time, the potential disaster area is the smallest, but the destructive power is the greatest; when 10°<θ<30°, the landslide body slides in a small fan-shaped shape, and the expansion angle of the boundaries on both sides is between 20° and 60°. At this time, the potential disaster area is medium and the destructive power is medium; when θ is greater than 30°, the landslide body slides in a large fan-shaped shape, and the expansion angle of the boundaries on both sides is greater than 60°. At this time, the potential disaster area is the largest and the destructive power is the weakest.

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