Method for estimating three-dimensional shape of landslide surface

Abstract

[Problem] To provide a method for estimating, on the basis of displacement measurements of the terrain before and after the occurrence of a landslide, the three-dimensional shape of a landslide surface that guarantees a certain degree of accuracy, while offering promptness and ease of use even in places where the cause of occurrence or movement pattern is unusual. [Solution] Movement vectors of observation points are calculated from survey results before and after the occurrence of a landslide and the landslide occurrence range is divided into areas by drawing main survey lines, secondary survey lines, and cross lines. Movement vectors under the main survey lines and the secondary survey lines are divided into groups according to gradient. An estimated shape of the landslide surface is drawn by sequentially connecting the landslide head part to the landslide terminal part according to the gradient in each group. The cross lines reflect the gradients of landslide scarps and cracks on both sides of the landslide occurrence range. Values calculated from the drawing are given to points of intersection of the cross lines with the main survey lines and with the sub-survey lines. A two-dimensional shape of the landslide surface is drawn by sequentially connecting one side thereof to the other side. These estimated values are reflected on a topographic map so as to create an estimated diagram of the three-dimensional shape of the landslide surface.

Description

Method for estimating the shape of a three-dimensional landslide surface

[0001] This invention relates to a method for estimating the shape of a landslide surface based on displacement measurements of the topography before and after the landslide.

[0002] The shape of a landslide surface varies depending on the topography and geology of the landslide site, as well as the cause of the landslide (e.g., excavation work, or natural phenomena such as earthquakes or heavy rainfall). Furthermore, the need to estimate the shape of a landslide surface often arises during a disaster. By quickly and accurately determining the shape of the landslide surface and taking countermeasures tailored to its scale and characteristics, the safety of disaster recovery activities can be ensured, and the risk of secondary disasters can be avoided or mitigated. In other words, a method that is quick, easy, and ensures a certain level of accuracy based on the topography, geology, and cause of the landslide is desirable. As for control measures taken when a landslide occurs, the Landslide Prevention Technology Guidelines issued by the Ministry of Land, Infrastructure, Transport and Tourism in 2008 include surface water drainage, groundwater drainage, soil removal, retaining embankment, and erosion prevention measures using river structures, etc. Estimating the shape of the landslide surface allows for the determination of boring drilling locations and depths, the amount of embankment, and the method of restraint work, and construction is carried out accordingly.

[0003] Among the aforementioned landslide prevention measures, groundwater drainage is an important construction method that stabilizes the slope and prevents secondary landslides by removing groundwater remaining on the landslide surface after a landslide has occurred. The depth, location, and direction of boring are determined based on the estimated shape of the landslide surface. As a method for estimating this landslide surface shape, the method described in Patent Document 1 is known, and as stated in the specification

[0046] , "As shown in Figure 11, the landslide surface is set by sequentially connecting the landslide constituent points PC within the same mesh group MSG." This method involves selecting a continuous mesh group from the head to the toe of the landslide and using the information of the movement vector on that mesh to draw from the starting point of the landslide head to the ending point of the toe. The applicant has also invented a two-dimensional method for estimating the shape of a landslide surface, such as in Patent Document 2. However, under certain conditions, these conventional methods for estimating the shape of a landslide surface may show a large discrepancy between the estimated value and the landslide surface depth (hereinafter referred to as the measured value) obtained by boring or other means. For example, if the shape of the ground that collapsed due to a landslide is bowl-shaped, the cause of the change may lie on the side of the landslide area. In addition to sliding from the highest elevation landslide head to the lower elevation toe, a large amount of soil mass may slide from the side to the center. Therefore, if a survey line is drawn (or a group of meshes is selected) connecting the landslide head to the toe of the landslide near the side in the width direction of the landslide, and the shape of the landslide surface below that survey line is plotted two-dimensionally, a large discrepancy between the estimated and measured values ​​is likely to occur. Furthermore, if the original topography has unusual characteristics, such as clayey soil extending deep into the ground, a large discrepancy between the estimated and measured values ​​may occur even when estimating the shape of the landslide surface below a survey line (or mesh) placed in the center in the width direction of the landslide area. Therefore, in order to safely and efficiently perform boring drilling in groundwater drainage works, there is a need for a method of estimating the shape of the landslide surface that is quick and easy to implement, while ensuring a certain degree of accuracy, even in locations where the causes and movement patterns of landslides are unusual or have unique topography and geology.

[0004] Next, among the above-mentioned suppression works, the embankment work aims to add a force that resists the sliding force of the landslide by embanking at the end of the landslide slope. Therefore, it is very important to grasp the quantity and volume of the soil mass that has slid due to the occurrence of the landslide. As a method for grasping the volume of this slid soil mass, a measurement line is drawn at approximately the center in the width direction of the landslide occurrence range, connecting from the landslide head to the landslide end. Based on the movement vector under the measurement line, a two-dimensional landslide surface shape is drawn. Based on this shape, the volume of the entire landslide soil mass is calculated and estimated. The amount of embankment, the length and number of anchors, etc. are determined from the estimated volume, and basically, the determined construction method is carried out uniformly everywhere. Therefore, when there are characteristics different from the normal ones in the above-mentioned causes of occurrence, terrain, or geology, there is a possibility that the actual volume is larger than the estimated volume. Due to insufficient embankment or inappropriate selection of the suppression method, there is a concern that the risk of secondary disasters increases. Here, it is possible to consider a method of estimating the volume of the landslide soil mass three-dimensionally by increasing the number of measurement lines connecting from the landslide head to the landslide end for drawing the landslide surface shape and estimating more two-dimensional landslide surface shapes in the measurement line direction. However, as described above, when estimating the landslide surface shape based on the measurement line drawn closer to the side surface in the width direction of the landslide occurrence range, there is a characteristic that the deviation between the estimated value and the measured value is likely to occur. Therefore, it can be said that it is insufficient as a solution to this problem.

[0005] Furthermore, in the aforementioned landslide prevention work, the depth of the landslide surface can be determined according to the soil type and groundwater volume when boring is performed. On the other hand, the method for estimating the shape of the landslide surface is based on reading surface topographic changes and estimating the shape of the landslide surface underground, so it does not necessarily match the measured values. For this reason, in work at many landslide sites, the shape of the landslide surface (hereinafter referred to as the landslide surface shape based on measured values) is determined by boring, etc., and the cause analysis of landslide occurrence is performed from this landslide surface shape based on measured values, which is useful for predicting future risks and implementing preventive measures. However, there are challenges in determining the shape of the landslide surface based on measured values. That is, if the landslide area is wide or the ground has irregular characteristics, the number of borings must be increased. This is costly and time-consuming, and it can be said that there is a need to efficiently determine the shape of the landslide surface with a certain degree of accuracy using fewer measured values.

[0006] Patent No. 7170575 Patent Application No. 2023-117952

[0007] The present invention aims to provide a method that, based on displacement measurements of the topography before and after a landslide, can estimate a three-dimensional landslide surface shape with a certain degree of accuracy, while maintaining speed and ease, even in locations with unusual or unique topography or geology where the cause of the landslide or the movement pattern is not typical. Furthermore, it aims to provide a method that can quickly and easily determine the next appropriate boring drilling location based on the landslide depth obtained from actual boring drilling.

[0008] To solve the aforementioned problems, the three-dimensional landslide surface shape estimation method according to the present invention is a method for estimating the landslide surface shape from ground displacement measurements and drawing the landslide surface from the landslide head to the endpoint, which is the landslide toe, characterized in that the landslide surface shape below the main and sub-surface lines, which are longitudinal survey lines of the landslide occurrence area, is estimated in accordance with the direction of landslide movement, and the landslide surface shape of the transverse lines in the width direction of the landslide occurrence area is estimated based on the estimation results of the landslide surface shape below the main and sub-surface lines and the slopes of the landslide scarps and cracks on both sides of the landslide occurrence area, thereby estimating a three-dimensional landslide surface shape. Furthermore, in addition to the above features, the method is characterized by drawing a main survey line located approximately in the center of the width direction of the landslide area, connecting the head of the landslide to the toe of the landslide, and drawing secondary survey lines to sandwich the main survey line on the left and right, and drawing a transverse line approximately in the center of the length direction of the landslide area, connecting the left and right sides of the landslide area, and intersecting the main survey line and / or the secondary survey line, and drawing transverse lines above and below the transverse line, thereby dividing the landslide area into areas.

[0009] More specifically, in a method for estimating the shape of a landslide surface from ground displacement measurements and plotting the landslide surface from the landslide head to the landslide toe, the movement vector of the observation point is calculated from the ground displacement measurements, and a main survey line is located approximately in the center of the width direction of the landslide area, connecting the landslide head to the landslide toe, secondary survey lines are flanking the main survey line on the left and right, and a line connects the left and right sides of the landslide area and intersects with the main survey line and / or the secondary survey line. A cross line is drawn, the movement vectors are grouped based on the gradient of the movement vectors under the main survey line, a representative movement vector is determined for each group, the group is divided by a vertical dividing line at the starting point of the group, a virtual line is drawn from the starting point of the group to the end point of the landslide to the intersection with the dividing line of the next group using the gradient of the representative movement vector of that group, and so on, from the intersection of the next group to the end point of the landslide to the gradient of the representative movement vector of the next group, Furthermore, the lines are drawn up to the intersection with the dividing line of the next group, and the landslide surface is drawn for each group up to the endpoint of the landslide toe of the group, and the two-dimensional landslide surface shape is drawn in descending order from the starting point of the landslide head to the endpoint of the landslide toe, and the secondary survey line is drawn in the same manner as the main survey line, from the starting point of the landslide head to the endpoint of the landslide toe, in descending order, and from one side below the transverse line, the slope of the landslide cliff or crack on that one side, The method is characterized by drawing a spline curve connecting the next intersection of the main survey line or the secondary survey line below the aforementioned cross-section line, drawing a spline curve connecting the next intersection of the main survey line or the secondary survey line from the intersection that is the endpoint of the sequentially drawn virtual lines, drawing a spline curve connecting the intersection with the secondary survey line immediately preceding the end of the other side surface to the end of the other side surface, drawing the slope of the landslide cliff or crack on the other side surface, and drawing a two-dimensional landslide surface shape from one side surface to the other side surface.Furthermore, in addition to the above features, the method is characterized by the addition of a step to determine the next ground excavation location within the landslide area by first estimating the three-dimensional landslide surface shape from ground displacement measurements using a three-dimensional landslide surface shape estimation method, then plotting the three-dimensional landslide surface shape based on the measured value of the landslide surface depth determined by ground excavation within the landslide area and the gradient of the landslide scarp or crack surrounding the landslide area, comparing and verifying the three-dimensional estimated landslide surface shape plotted using the three-dimensional landslide surface shape estimation method with the two-dimensional or three-dimensional landslide surface shape plotted based on the measured value of the landslide surface depth and the gradient of the landslide scarp or crack surrounding the landslide area, and then determining the next ground excavation location within the landslide area.

[0010] This invention utilizes the two-dimensional landslide surface shape estimation method described in Patent Document 2 by the applicant. The three-dimensional landslide surface shape drawing method according to the present invention retains the advantages described in

[0015] of the specification of Patent Document 2, namely that "multiple analyses are unnecessary and it is easy to increase the speed of drawing the landslide surface shape." Therefore, even when estimating the landslide surface shape under multiple survey lines or cross lines, speed and ease can be maintained. Furthermore, by estimating the landslide surface shape under cross lines, it is possible to grasp not only the sliding of landslides that move from the high-elevation landslide head to the low-elevation landslide toe, but also irregular sliding caused by landslide scarps on the sides of the landslide occurrence area and the original topographic and geological characteristics. This enables more accurate estimation of the landslide surface shape than the conventional technology, improving the accuracy of determining boring drilling locations and the volume of soil masses that have slid due to landslides. This can be used to select appropriate construction methods for control and restraint works and to ensure the safety of construction workers. Furthermore, by comparing and verifying the measured landslide surface depth determined through boring drilling and other operations, the three-dimensional landslide surface shape drawn based on the slope of the landslide scarp or crack, and the estimated three-dimensional landslide surface shape according to the present invention, the landslide surface shape of the entire landslide area can be grasped more efficiently, the next appropriate boring drilling location can be set, costs can be reduced by decreasing the number of boring drills, and work efficiency can be greatly improved.

[0011] Flowchart of the process for estimating the shape of a three-dimensional landslide surface (1) Explanatory diagram of topographic surveys at two periods, before and after the landslide, using UAV laser surveying. Tabular diagram of the list of topographic survey results at two periods, before and after the landslide. Explanatory diagram of the topography before and after the landslide and the initial slip surface (slope of the movement vector around the head and fall cliff, and landslide surface drawn based on the toe). Topographic map of landslide location A reflecting movement vectors, main survey lines, secondary survey lines and cross lines (1) Topographic map of landslide location B reflecting movement vectors, main survey lines, secondary survey lines and cross lines Explanatory diagram 1 of drawing the landslide surface shape below the main survey line and secondary survey line. Explanatory diagram 2 of drawing the landslide surface shape below the main survey line and secondary survey line. Explanatory diagram 3 of drawing the landslide surface shape below the main survey line and secondary survey line. Explanatory diagram 4 of drawing the landslide surface shape below the main survey line and secondary survey line. Diagram 5 illustrating the drawing of the landslide surface shape below the main and secondary survey lines. Diagram 6 illustrating the drawing of the landslide surface shape below the main and secondary survey lines. Estimated two-dimensional landslide surface shape below transverse line b (1) Contour map of the landslide surface at landslide location A (estimated three-dimensional landslide surface shape). Process flow diagram of the method for estimating the three-dimensional landslide surface shape (2) Topographic map of landslide location A reflecting the movement vector, main survey line, secondary survey line and transverse line (2) Comparison diagram of the estimated two-dimensional landslide surface shape below transverse line b and the landslide surface shape reflecting the landslide depth Contour map of the landslide surface drawn based on the landslide depth obtained by boring at landslide location A (estimated three-dimensional landslide surface shape).

[0012] Embodiments of the present invention will be described with reference to the drawings. However, unless otherwise specifically stated, the devices, shapes, etc., described in these embodiments are not intended to limit the scope of the present invention, but are merely illustrative examples.

[0013] (Flow of the estimation method according to the present invention) An embodiment of the three-dimensional landslide surface shape estimation method according to the present invention will be explained based on the process flow diagram in Figure 1. First, displacement measurements of observation points are obtained from survey results before and after the landslide, the direction of movement of the observation points is calculated, and the movement vector is determined ([1] Movement vector calculation step). Second, the landslide area is identified from the topographic map after the landslide, and main survey lines, sub-survey lines and cross lines are drawn in the landslide area to divide it into areas ([2] Area division step). Third, the movement vectors under the main survey line and sub-survey line are grouped according to the gradient of the vector, and the gradient for each group is calculated ([3] Movement vector grouping step). Fourth, for the main survey line and sub-survey line, the estimated shape of the two-dimensional landslide surface is drawn by sequentially connecting the landslide head to the landslide toe using the gradient for each group calculated in the movement vector grouping step. ([4] Estimation process of the two-dimensional landslide surface shape below the main survey line and the sub-surface survey line) Fifth, for the transverse line, the gradient near the landslide scarp on both sides of the landslide occurrence area corresponding to the starting and ending points is reflected, and values ​​calculated by drawing the estimated two-dimensional landslide surface shape of the main survey line or the sub-surface survey line are given to the intersections of the transverse line and the main survey line, and the transverse line and the sub-surface survey line, and the two-dimensional landslide surface shape is drawn by sequentially connecting one side to the other. ([5] Estimation process of the two-dimensional landslide surface shape below the transverse line) Sixth, the estimated values ​​of the two-dimensional landslide surface shape drawn below the main survey line, the sub-surface survey line and below the transverse line are reflected in the topographic map after the landslide has occurred, and an estimated map of the three-dimensional landslide surface shape is created ([6] Estimation process of the three-dimensional landslide surface shape).

[0014] (Regarding the method for determining topographic displacement measurements) In carrying out the present invention, topographic survey results from at least two periods are required in order to determine the displacement measurements of the topography 01 before the landslide and the topography 04 after the landslide, as shown in Figure 2. Conventionally, the shape of the landslide surface was estimated by taking core samples by boring drilling, conducting in-hole tests, and performing landslide observations using boreholes. However, performing boring drilling for landslide observation while ensuring safety requires advanced technology and cost. However, with the recent spread of topographic measurement using UAV-mounted laser scanners 02, it is possible to perform topographic surveys before and after the landslide without entering the landslide area. Aerial laser surveying and surveying methods using UAV-mounted laser scanners 02 as shown in Figure 2 are desirable in terms of ensuring safety and speed during observation because they can calculate the movement vectors of multiple observation points simultaneously. However, there are no limitations on the use of moving stakes, extensometers, ground surface inclinometers, etc., when performing observations and surveys for calculating movement vectors.

[0015] (The movement vector is determined from the displacement measurement values ​​at the observation points.) [1] As an example of the movement vector calculation process shown in Figure 3, the observation point 06 of the terrain before the landslide occurs is set as the starting point, and the observation point 07 of the terrain after the landslide occurs is set as the ending point, and their positions are determined by the X coordinate and Y coordinate. Then, by connecting the starting point and the ending point with a line, the distance and direction of movement of the observation point (the gradient 08 or angle of the movement vector of the observation point) can be calculated.

[0016] (Draw main survey lines, secondary survey lines and cross lines on the topographic map after the landslide has occurred.) [2] In the area division process, as shown in the example of landslide occurrence location A in Figure 5, the landslide occurrence area 12 is identified on the topographic map after the landslide has occurred, a main survey line 13 is drawn located approximately in the center of the width direction of the landslide occurrence area 12 and connecting the landslide head to the landslide toe, and secondary survey lines a14a and b14b are drawn to sandwich the main survey line 13 on the left and right, and a cross line b15b is drawn approximately in the center of the length direction of the landslide occurrence area 12, connecting the left and right sides of the landslide occurrence area 12 and intersecting the main survey line 13, and cross lines a15a and c15c are drawn to sandwich the cross line b15b above and below, thereby dividing the landslide occurrence area 12 into areas. In this example, there are three longitudinal survey lines (main and sub-surface survey lines) and three transverse survey lines in the width direction of the landslide area 12, and they are placed at nearly equal intervals. However, the more longitudinal survey lines and transverse survey lines there are, the more detailed the estimated values ​​can be calculated, and there are no particular restrictions on the number of lines or the spacing between them. Furthermore, if the landslide area 12 has an irregular shape, as in the landslide location B in Figure 6, it is not possible to draw a straight survey line connecting the head and toe of the landslide. In such cases, a bent line like the sub-surface survey lines a14a and b14b in the figure may be drawn, or a short survey line like the sub-surface survey line c14c may be drawn. In addition, if it is possible to predict locations where the cause of change can be identified or suspected from the topography and movement vectors after the landslide occurs, including those locations in the longitudinal survey lines and transverse survey lines in the width direction can improve the accuracy of the landslide surface shape estimation.

[0017] (Group the movement vectors according to the gradient of the vectors.) [3] The process of grouping the movement vectors involves creating a list like the one shown in Figure 3 and grouping them into groups with similar gradients of movement vectors. Conventionally, when drawing the shape of a landslide surface, it is common to draw it as shown in Figure 4, using a curve that connects the starting point 10 of the head of the landslide surface and the ending point 11 of the toe of the landslide surface, based on the gradient of the movement vectors around the landslide scarp 05 (hereinafter referred to as the initial slip surface 16), but this initial slip surface 16 could not adequately reflect differences in shape such as unevenness in the topography, differences in geology, differences in layer thickness, for example, that in addition to the downward gradient that is often seen in the gradient of the movement vectors around the landslide scarp 05, there may also be gradients in the planar direction or upward direction in some places. However, by listing the numerical values ​​in this way, observation points showing outliers can be quickly found, and grouping based on the gradient of the movement vectors can also be easily performed. When drawing the two-dimensional landslide surface shape on the main survey line 13, the secondary survey line a14a, and the secondary survey line b14b, which will be described later, the observation point that serves as the starting point for each group is divided by a vertical dividing line.

[0018] (Calculation of gradients for each group) Then, the gradient 09 of the group's movement vector is determined from multiple observation points of these groups shown in Figure 3, and it is preferable to use the median of the gradients 08 of the movement vectors at each observation point. The reason why it is preferable to use the median is that there is a risk of outliers occurring at observation points due to the accidental presence of large rock formations, etc., and using the average value would result in a value that deviates significantly from the center. Furthermore, when surveying is performed using a UAV-mounted laser scanner 02, it is assumed that there are observation points where sufficient survey data cannot be obtained due to, for example, the density of vegetation on slopes where vegetation work has been carried out. In such cases, the movement vector of the observation point is excluded from the calculation of the median, and the gradient 09 of the movement vector for each group is determined.

[0019] (Regarding the estimation of the two-dimensional landslide surface shape below the main and secondary survey lines) [4] The process of estimating the two-dimensional landslide surface shape below the main and secondary survey lines will be explained with reference to the diagrams of one embodiment of the landslide surface shape estimation method shown in Figures 7 to 11. These diagrams are illustrative and represent the landslide surface shape at a different location from the landslide occurrence range shown in Figures 4 and 5. First, as shown in Figure 7, the drawing of the landslide surface shape begins from the head initiation point 10 of the landslide surface. Next, as shown in Figure 8, based on the gradient of the movement vector of group A having the head initiation point 10 of the landslide surface, a virtual line 18a (the landslide surface 18a estimated by the gradient of the movement vector of group A) connecting the head initiation point 10 of the landslide surface to the end point 11 of the landslide surface is drawn using a NURBS curve from the head initiation point 10 of the landslide surface to the position of the vertical dividing line drawn down from the observation point that forms the boundary between group A and group B. Then, as shown in Figure 9, the point where the vertical dividing line drawn from the observation point that forms the boundary between group A and group B intersects with the drawing of the landslide surface shape is defined as intersection point (ab) 19a. Based on the gradient of the movement vector of group B, a virtual line 18b (the landslide surface 18b estimated by the gradient of the movement vector of group B) is drawn from intersection point (ab) 19a to the endpoint 11 of the landslide surface using a NURBS curve, from intersection point (ab) 19a to the position of the vertical dividing line drawn from the observation point that forms the boundary between group B and group C. This creates a new intersection (bc) 19b, and as shown in Figure 10, based on the gradient of the movement vector of the group starting from the new intersection, a virtual line 18 connecting the new intersection to the end point 11 of the landslide surface is continuously drawn using a NURBS curve up to the position of the vertical dividing line drawn from the observation point that forms the boundary with the next group. Finally, as shown in Figure 11, the estimated shape of the landslide surface is drawn from the head starting point 10 to the end point 11 of the landslide surface.However, when plotting the landslide surface of the aforementioned group, there may be observation points where sufficient survey data cannot be obtained. In such cases, as shown in Figure 10 for the range from group E to group F, it is advisable to plot a virtual line 18e (the landslide surface 18e estimated by the gradient of the movement vector of group E) connecting intersection (de) 19d to the endpoint 11 of the landslide surface, using a NURBS curve, from intersection (de) 19d to intersection (ef) 19e, which is the position of the vertical dividing line drawn down from the observation point that is the starting point of group F. The plotting using a NURBS curve is assumed to be done using a spline curve in general CAD software, but it is not limited to this.

[0020] (Regarding the drawing of landslide surface shapes in descending order) Furthermore, the drawing of the two-dimensional landslide surface shapes estimated under the main and secondary survey lines will be done in descending order from the group with the landslide head. As shown in Figure 12, it is possible to predict not only the slip surface of the drawn group but also the slip surface of the next group, which not only helps to quickly grasp the overall picture but also increases the amount of information to consider when reflecting the aforementioned information such as geology and cause of occurrence.

[0021] (Regarding the estimation of the two-dimensional landslide surface shape below the transverse lines) [5] The process of estimating the two-dimensional landslide surface shape below the transverse lines is performed after the drawing of the two-dimensional landslide surface shapes below the main and sub-surface lines is completed, and then, for transverse lines a15a, b15b, and c15c shown in Figure 5, the two-dimensional landslide surface shapes below each transverse line are drawn in the following procedure. Figure 13 shows the landslide surface shape below transverse line a15a, and the drawing of the landslide surface shape in this figure starts from the left side head 21. First, the intersection points of transverse line a15a and the main or sub-surface line, intersection point (ab) 22a, intersection point (bc) 22b, and intersection point (cd) 22c, are given the values ​​of the landslide surface shape obtained by the estimation of the two-dimensional landslide surface shape of the main and sub-surface lines. Secondly, based on the slope of the landslide cliff on the left side head 21, a NURBS curve is drawn connecting the left side head 21 to the intersection (ab) 22a of the secondary survey line a14a and the transverse line a15a. Thirdly, a NURBS curve is drawn starting from the intersection (ab) 22a and connecting to the intersection (bc) 22b of the main survey line 13 and the transverse line a15a. Next, a NURBS curve is drawn starting from the intersection (bc) 22b and connecting to the intersection (cd) 22c of the secondary survey line b14b and the transverse line a15a. Fourth, since the intersection (cd) 22c is the intersection point immediately preceding the right side head 23, a NURBS curve is drawn connecting the right side head 23 to the intersection (cd) 22c of the secondary survey line b14b and the transverse line a15a, based on the slope of the landslide cliff of the right side head 23. Then, the two-dimensional landslide surface shapes of transverse lines b and c are drawn sequentially. In this embodiment, the drawings are made sequentially from the left side to the right side, but there is no problem in drawing from either the left or the right, and there is no problem in drawing the two-dimensional landslide surface shape from any of the transverse lines.

[0022] (Regarding the estimation of the three-dimensional landslide surface shape) [6] The process of estimating the three-dimensional landslide surface shape is a process of estimating the three-dimensional landslide surface shape by estimating the landslide surface shape below the main and sub-surfaces, which are longitudinal survey lines of the landslide occurrence area, and estimating the landslide surface shape of the transverse lines in the width direction of the landslide occurrence area, taking into account the estimation results of the landslide surface shape below the main and sub-surfaces and the slopes of the landslide scarps on both sides of the landslide occurrence area. For example, as shown in Figure 14, the estimated three-dimensional landslide surface shape can be represented as a contour map by drawing contour maps using CAD software. Then, the total volume of the landslide mass in the landslide occurrence area can be calculated from the difference between the contour map of the landslide surface in the landslide occurrence area and the contour map of the ground surface in the landslide occurrence area.

[0023] (Regarding the process of verifying the shape based on measured values ​​and the estimated shape [7]) Figure 15 is a process flow chart that adds the process of verifying the shape based on measured values ​​[7] after the six processes shown in Figure 1. An example of this process will be explained below. The process of verifying the shape based on measured values ​​[7] consists of four processes as shown in the right diagram of Figure 15: [a] determining the landslide depth (measured value) by boring drilling, etc., [b] creating topographic data and a contour map of the landslide surface based on the measured value, [c] comparing the measured value and the estimated value using topographic data or a contour map of the landslide surface, and [d] extracting the next boring drilling location. Firstly, the process of determining the landslide depth (measured value) by boring drilling, etc., is a process in which boring drilling is performed based on the estimated landslide surface shape, and the measured value is obtained from the actual landslide depth. The location where the measured value was obtained is designated as boring location 24, as shown in Figure 16. Secondly, [b] the process of creating topographic data or a contour map of the landslide surface based on measured values ​​is, in this case, the process of creating topographic data or a contour map of the landslide surface based on measured values, based on the landslide depth at the boring location 24 and the slope of the landslide scarp or crack surrounding the landslide occurrence area 12. Since the boring location 24 is located at the intersection of the main survey line 13 and the transverse line b15b of the landslide occurrence area 12, it can be represented by the two-dimensional estimated shape of the landslide surface of the transverse line b15b, as shown in Figure 17. The drawing procedure in this figure involves drawing a NURBS curve of the slope of the landslide scarp or crack connecting the landslide depth 25 at the boring location 24 and the right side head 23, and then drawing a NURBS curve of the slope of the landslide scarp or crack connecting the landslide depth 25 at the boring location 24 and the left side head 21, thereby drawing the landslide surface shape 26 below the transverse line b based on measured values. Furthermore, as shown in Figure 18, a contour map can be drawn using general CAD software, taking into account the measured value of the landslide depth at the boring location 24 and the slope of the landslide scarp or crack surrounding the landslide occurrence area 12. This figure was created using landslide depths from multiple boring locations 24, but it can be drawn if there are measured values ​​from one or more locations.As will be explained later, the comparison of measured and estimated values ​​in the next step can be done using only topographic data, so it is not necessarily required to create a contour map of the slip surface in this step.

[0024] Thirdly, the [c] step of comparing measured and estimated values ​​using topographic data or slip surface contour maps is a step of comparing the measured and estimated landslide depths at the same location, or quantifying them and finding the difference. Comparison using topographic data is a step of finding the difference from the quantified landslide depth. For example, the estimated landslide depth at each point of the three-dimensional estimated landslide surface shape drawn in steps [1] to [6] above can be quantified, and similarly the landslide depth based on measured values ​​can be quantified and compared to find the difference in landslide depth. Areas or locations with a large difference are likely to have irregular characteristics in the ground. Comparison using slip surface contour maps is a step of understanding the overall picture of the landslide occurrence area by comparing the two maps. For example, in Figure 17, which compares two-dimensional landslide surface shapes, when comparing the drawn landslide surface 20, which is the estimated landslide surface shape below the transverse line b15b, with the landslide surface shape 26 below the transverse line b15b based on actual measurements, the point of maximum discrepancy 27 between the estimated and actual values ​​becomes clear. Also, in Figures 14 and 18, which compare three-dimensional landslide surface shapes, the difference in the number of contour lines below the transverse line b15b from the intersection with the auxiliary survey line a14a to the landslide scarp on the left side of the illustration can be grasped, and construction workers can quickly grasp the overall picture of the landslide surface shape by looking at these comparison figures. Fourthly, [d] the process of extracting the next boring drilling location is a process of evaluating the difference in topographic data obtained in the process of [c] and the difference in features seen in the landslide surface contour map, and determining the next boring drilling location. For example, in Figure 17, the process involves identifying areas where it is difficult to estimate the landslide surface shape from surface changes, such as the point 27 where the estimated value and the measured value diverge the most, and selecting candidate locations 28 for the next boring location. This process allows for the prior identification of irregular characteristics in understanding the landslide surface shape of the landslide area, which not only improves the accuracy of understanding the overall shape of the landslide area but also makes it easier to efficiently reduce the number of borings required, leading to cost and time savings. By repeating these steps [a] to [d], the landslide surface shape of the entire landslide area can be understood more efficiently.

[0025] (Conclusion) Based on the above, the present invention is useful in providing a method that can estimate a three-dimensional landslide surface shape with a certain degree of accuracy, while being quick and easy, even in locations with unusual or unique topography or geology where the cause of the landslide and the movement pattern are not common, based on displacement measurements of the topography before and after the landslide. Furthermore, it is useful in providing a method that can quickly and easily determine the next appropriate boring drilling location based on the landslide depth obtained by actual boring drilling.

[0026] 01 Topography before landslide 02 UAV-mounted laser scanner 03 Crack 04 Topography after landslide 05 Slip cliff 06 Observation point before landslide 07 Observation point after landslide 08 Slope of movement vector of observation point 09 Slope of movement vector of group 10 Head origin (of landslide surface) 11 End point (of landslide surface) 12 Landslide occurrence area 13 Main survey line 14 Sub-surface survey line 14a Sub-surface survey line a 14b Sub-surface survey line b 14c Sub-surface survey line c 15 Cross-section line 15a Cross-section line a 15b Cross-section line b 15c Cross-section line c 15d Cross-section line d 16 Original slip surface (slope of movement vector around the head and slip cliff, landslide surface drawn based on the end) 17 Movement vector 18a 18b Slip surface estimated from the gradient of the movement vector of Group A 18e Slip surface estimated from the gradient of the movement vector of Group B 19 Intersections of the vertical division lines from the observation point and the drawn slip surface 19a Intersection (ab) 19b Intersection (bc) 19d Intersection (de) 19e Intersection (ef) 20 Drawn slip surface 21 Left side head 22a Intersection (ab) 22b Intersection (bc) 22c Intersection (cd) 23 Right side head 24 Boring location 25 Slip depth at boring location 24 26 Slip surface shape below transverse line b drawn based on measured values ​​27 Point of maximum discrepancy between estimated and measured values ​​28 Candidates for the next boring location

Claims

In a method for estimating the shape of a landslide surface from ground displacement measurements and plotting the landslide surface from the landslide head to the landslide toe, The shape of the landslide surface below the main and secondary survey lines, which are survey lines in the longitudinal direction of the landslide occurrence area, is estimated in accordance with the direction of landslide movement. Furthermore, the shape of the landslide surface along the widthwise transverse of the landslide area is estimated based on the estimated results of the landslide surface shape below the main and secondary survey lines and the slopes of the landslide scarps and cracks on both sides of the landslide area. Estimating the three-dimensional shape of a landslide surface. A three-dimensional landslide surface shape estimation method characterized by the following. 　 A main survey line is drawn approximately in the center of the widthwise region of the landslide area, connecting the landslide head to the landslide toe, and secondary survey lines are drawn to sandwich the main survey line on both sides. Then, a transverse line is drawn approximately in the center of the length of the landslide area, connecting the left and right sides of the landslide area, and intersecting the main and / or secondary survey lines, and a transverse line is drawn above and below the aforementioned transverse line. Dividing the area where landslides occurred into zones. A method for estimating the shape of a three-dimensional landslide surface according to claim 1, characterized by the above. 　 In a method for estimating the shape of a landslide surface from ground displacement measurements and plotting the landslide surface from the landslide head to the landslide toe, The movement vector of the observation point is calculated from the ground displacement measurement, A main survey line is drawn approximately in the center of the widthwise region of the landslide area, connecting the landslide head to the landslide toe, secondary survey lines are drawn flanking the main survey line, and cross lines are drawn connecting the left and right sides of the landslide area and intersecting the main survey line and / or the secondary survey lines. Based on the gradient of the movement vectors under the aforementioned main measurement line, the movement vectors are grouped. The representative movement vector for each group is determined, At the starting point of the aforementioned group, it is divided by a vertical dividing line, From the starting point of the aforementioned group, a virtual line is drawn connecting it to the endpoint of the landslide to the gradient of the group's representative movement vector, up to the intersection with the dividing line of the next group. From the intersection of the next group, a virtual line is drawn connecting the end point of the landslide to the corresponding point using the gradient of the representative movement vector of the next group, and then to the intersection with the dividing line of the next group. The landslide surface is drawn for each group up to the endpoint of the landslide tomb of the aforementioned group. The two-dimensional landslide surface shape is drawn in descending order from the starting point of the landslide head to the endpoint of the landslide toe. The aforementioned secondary survey line is drawn in the same manner as the main survey line, drawing the two-dimensional landslide surface shape from the starting point of the landslide head to the endpoint of the landslide toe in descending order. From one side below the aforementioned cross-section, a spline curve is drawn connecting the next intersection of the aforementioned main survey line or the aforementioned secondary survey line below the aforementioned cross-section, using the slope of the landslide cliff or crack on that one side. Then, from the intersections which are the endpoints of the sequentially drawn virtual lines, a spline curve is drawn connecting the next intersection of the aforementioned main survey line or the aforementioned secondary survey line. The spline curve connecting the intersection point with the aforementioned sub-surface line just before the end of the other side and the end of the other side is drawn using the slope of the landslide cliff or crack on the other side, thereby drawing a two-dimensional landslide surface shape from one side to the other side. A three-dimensional landslide surface shape estimation method characterized by the following: After estimating the three-dimensional landslide surface shape from ground displacement measurements using a three-dimensional landslide surface shape estimation method, The measured depth of the landslide surface, determined by ground excavation within the landslide area, and the three-dimensional landslide surface shape based on the slope of the landslide scarp or cracks surrounding the landslide area are plotted. The three-dimensional landslide surface shape estimated using the three-dimensional landslide surface shape estimation method described above is compared and verified with the two-dimensional or three-dimensional landslide surface shape drawn based on the measured value of the landslide surface depth and the slope of the landslide scarp or crack surrounding the landslide occurrence area. The process of determining the location of ground excavation within the next landslide area was added. A method for estimating the shape of a three-dimensional landslide surface according to claim 1, claim 2, or claim 3, characterized by the above.

Images