Method for estimating ground sliding surface shape

Abstract

To provide a method for estimating a landslide surface shape which is excellent in speed and easiness and satisfies a certain level of accuracy on the basis of displacement measured value of a topography before landslide and a topography after landslide.SOLUTION: A movement vector at an observation point is calculated from displacement measured value, grouping is performed on the basis of inclination of the movement vector, a representative movement vector every group is obtained, division by a division line in a vertical direction is performed at a starting point of the group, a virtual line connecting the starting point of the group and a landslide terminal part end point 11 at an incline of the representative movement vector in the same group is drawn up to an intersection with a division line of the next group, a virtual line connecting an intersection of the next group and the landslide terminal part end point 11 at an incline of the representative movement vector of the next group is successively drawn up to an intersection with a division line of the next group, and is drawn from a starting point 10 of a landslide head to the end point 11 of the landslide terminal every group in a descending order.SELECTED DRAWING: Figure 6

Description

Technical Field

[0001] The present invention relates to a method for estimating the sliding surface shape of a landslide based on displacement measurement values of the terrain before the occurrence of a landslide and the terrain after the occurrence of the landslide.

Background Art

[0002] The landslide surface shape varies depending on the terrain and geology of the landslide occurrence site and the cause of occurrence (such as induced by cutting work or natural phenomena such as earthquakes and heavy rains). In addition, in many cases where it is necessary to estimate the landslide surface shape, it is during a disaster. By quickly and accurately grasping the landslide surface shape and taking countermeasures according to the scale and characteristics, the safety of disaster recovery activities can be ensured, and the risk of secondary disasters can be avoided and reduced. That is, a method that guarantees speed, ease, and a certain accuracy based on the terrain, geology, and cause of occurrence is most desired. Patent Document 1 discloses a method for estimating the landslide surface shape, which "divides a landslide mass into a plurality of blocks by vertical dividing lines, divides the displacement measuring means so that it is installed on the ground surface of each block, sets the landslide surface for each block with a high-order polynomial, assembles a normal equation by the least squares method for each block, obtains the parameters of the high-order polynomial for each block based on at least one known boundary condition, and estimates the sliding surface shape of the entire landslide mass by connecting the calculated high-order polynomials for each block."

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Non-Patent Document 1

Non-Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, in order to estimate the shape of the landslide surface using the technology disclosed in Patent Document 1, calculations using high-order polynomials or error formulas are required, and it is difficult to calculate without using an electronic computer and software for execution, and it also takes time. Therefore, equipment for analyzing measurement values, preparation of dedicated software, and operation of programs are essential.

[0005] Furthermore, according to Non-Patent Document 1, which is a document explaining the above technology, when estimating the landslide surface shape by the above technology, input of topographic data, coordinates of measurement points, coordinates of positions where deformations (cracks and extrusions) appear (positions of the head and the end of the slip surface of the landslide), and ground surface displacement vectors at the measurement points is required. In addition, in order to improve the accuracy of the analysis results, it is desirable to input the setting of block division lines, the setting of underground boundary points, and the gradients of head sliding cliffs and cracks. It can be seen that the accuracy of the estimated results is affected by the presence or absence of knowledge and experience. In addition, depending on conditions such as topography and geology, there is also a problem that the estimated result of the calculated slip surface deviates from the actual shape of the slip surface. Therefore, it is difficult to say that the execution of the program for obtaining highly accurate results is easy, and it cannot be guaranteed that rapidity is always ensured.

[0006] Therefore, an object of the present invention is to provide a method for quickly and easily estimating the landslide surface shape with a certain accuracy based on the displacement measurement values of the terrain before the landslide and after the landslide.

Means for Solving the Problems

[0007] To solve the above problems, the invention according to claim 1 is A method for estimating the landslide surface shape, which draws the landslide surface from the landslide head as the starting point to the end point that is the landslide end point, and estimates the landslide surface shape in a two-dimensional vertical section from the displacement measurement values of the ground surface wherein a movement vector of an observation point is calculated from the displacement measurement value, the movement vectors are grouped based on the gradient of the movement vector, a representative movement vector for each group is obtained, and at the starting point of the group, it is divided by a vertical dividing line, Using the slip surface estimated by the gradient of the representative movement vector of the same group as a virtual line, the starting point of the group and connecting to the end point of the landslide end the a virtual line is drawn to the intersection with the dividing line of the next group, and the intersection of each subsequent group and connecting to the end point of the landslide end the a virtual line is further drawn to the intersection with the dividing line of the next group, and up to the end point position of the landslide end of the group Similarly for each group the virtual line is drawn By doing so from the starting point of the landslide head to the end point of the landslide end in descending order the virtual line and is characterized by drawing.

Effects of the Invention

[0008] According to the present invention, it is possible to provide a method for quickly and easily estimating the landslide surface shape with a certain accuracy based on the displacement measurement values of the terrain before the landslide and after the landslide.

Brief Description of the Drawings

[0009]

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Mode for Carrying Out the Invention

[0010] The embodiments of the present invention will be described with reference to the drawings. However, the devices, shapes, etc. described in this embodiment are not intended to limit the scope of the present invention unless otherwise specifically described, and are merely illustrative examples.

[0011] (Regarding the method for obtaining the displacement measurement value of the terrain) In carrying out the present invention, in order to obtain the displacement measurement values of the terrain 01 before the landslide shown in FIG. 1 and the terrain 04 after the landslide, the topographic survey results at least at two times are required. Conventionally, core sampling by boring excavation, in-hole tests, and landslide observations using bored holes have been carried out to estimate the shape of the landslide surface. However, it requires advanced technology and costs to perform boring excavation in a way that ensures safety for landslide observations. However, in recent years, due to the spread of topographic measurement using a UAV-mounted laser scanner 02, it is possible to perform the topographic measurement before the landslide and the measurement after the landslide without conducting a field survey. The aerial laser survey and the survey method using the UAV-mounted laser scanner 02 as shown in FIG. 1 are desirable in terms of ensuring the safety and speed during observation because they can calculate the movement vectors of a plurality of observation points simultaneously. However, it is not limited to using movement piles, extensometers, ground surface inclinometers, etc. during the observation and survey for calculating the movement vectors.

[0012] (Obtain the movement vector from the displacement measurement value at the observation point.) In FIG. 2, an example of obtaining the movement vector from the displacement measurement value at the observation point is shown. Taking the observation point 06 of the terrain before the landslide as the starting point and the observation point 07 of the terrain after the landslide as the end point, their positions are specified by the X coordinate and the Y coordinate. Then, when connecting the starting point and the end point with a line, the movement distance and the movement direction (the gradient 08 or the angle of the movement vector of the observation point) of the observation point can be calculated. Next, exclude the observation points where the value of the starting point X is larger than the point corresponding to the sliding cliff 05 at the time of the landslide (hereinafter, the head starting point 10 of the landslide surface), and the observation points where the value of the starting point X is smaller than the end point 11 of the end part of the landslide surface from the list. Create a list by arranging the starting point X in descending order with the head starting point 10 of the landslide surface as number 1 and the last number being the end point 11 of the end part of the landslide surface.

[0013] (Group the movement vectors according to the gradient of the vectors.) Conventionally, as shown in FIG. 3, when drawing the landslide surface shape, it has generally been drawn as a curve connecting the head start point 10 of the landslide surface and the end point 11 of the end part of the landslide surface based on the gradient of the movement vector around the landslide cliff 05. (The landslide surface estimated by this conventional drawing method is hereinafter referred to as the initial sliding surface 12.) However, the sliding surface from the head start point 10 to the end point 11 of the actual landslide surface has differences in the shape such as unevenness in the terrain, differences in geology, differences in layer thickness, etc. Therefore, not only the downward gradient often seen in the gradient of the movement vector around the landslide cliff 05, but also a horizontal or upward gradient may exist depending on the location. Therefore, creating a list such as that exemplified in FIG. 2 can quickly find groups having gradients of movement vectors with similar tendencies and observation points showing outliers, and thus can easily perform grouping based on the gradient of the movement vector necessary for solving the problem of the present invention of "drawing the landslide surface shape for each group". When drawing the landslide surface shape described later, at the observation point that is the starting point of each group, it is divided by a vertical dividing line.

[0014] (Calculation of Gradient for Each Group) Next, the gradient 09 of the movement vector as a group is obtained from a plurality of observation points in these groups, and in this case, the median value of the gradient of the movement vector of each observation point is used. The reason for using the median value is that there may be outliers due to the accidental presence of large rocks at the observation point, and if the average value is used, the value will deviate greatly from the center. Also, when surveying with the UAV-mounted laser scanner 02, for example, it is assumed that there may be observation points where sufficient survey data cannot be obtained depending on the density of vegetation on the slope where vegetation work has been carried out. In such a case, the movement vector of the said observation point is excluded from the object of the median value calculation, and the gradient 09 of the movement vector of each group is obtained.

[0015] (Merits of Grouping by Gradient of Movement Vector Patent Document 1) Performing the grouping of the movement vectors and the calculation of the gradient 09 of the movement vectors of the group before the drawing of the landslide surface shape is a means for solving the problems of the present invention. Therefore, when the geology of the landslide slope and the causes of the landslide can be grasped in advance, for example, depending on whether the landslide is a collapse, sliding, or flow, or whether it is a viscous soil landslide, bedrock landslide, arc landslide, planar landslide, etc., taking various conditions into account, the grouping of the movement vectors and the calculation of the gradient 09 of the movement vectors can be performed, and the landslide surface shape can be estimated in a form in which irregular elements are removed in advance. On the other hand, the estimation method of Patent Document 1 requires the input of the ground surface line, the positions of the ground surface measurement points, the positions of the ground surface boundary points, the measurement data (movement vectors), and the selection of analysis conditions (polygon parallel method, polygon rotation method, polynomial method) for the analysis at the time of estimation. Furthermore, when trying to reflect information such as geology and causes of occurrence, the validity of the estimation result is enhanced by changing the analysis conditions. That is, since it is a method in which after the analysis result is obtained, a person analyzes, adjusts, and performs the analysis again using software, it takes time to obtain a highly valid estimation result. Therefore, it can be said that the estimation method of the present invention does not require multiple analyses and is easily capable of enhancing the speed of drawing the landslide surface shape.

[0016] (Merits of creating groups with the gradient of movement vectors Patent Document 2) Also, in Patent Document 2, a method of calculating a differential vector for each mesh is shown, which can be said to be a more detailed estimation method than the estimation method according to the present invention. However, there is a description such as "selecting subsequent meshes according to the direction of the differential vector" in order to enhance the validity of the estimation result, and there is a problem that it cannot be automated. Therefore, if the estimation method according to Patent Document 2, which captures the landslide shape with meshes instead of cross-sections, is used, it is speculated that the number of adjustment points that cannot be automated increases as compared with the estimation method of the present invention that estimates in cross-sections, and it can be said that there is a problem in the rapid estimation of the landslide surface shape during disasters and the like. Therefore, enhancing the speed of the method of estimating the landslide surface shape in cross-sections as in the present invention brings different benefits as compared with the invention of Patent Document 2.

[0017] (Depicting the landslide surface for each group) Then, regarding the method of drawing the landslide surface shape, the present invention estimates the landslide surface shape in a two-dimensional vertical cross-section from the displacement measurement values of the ground surface, and in the method of drawing the landslide surface from the starting point of the landslide head to the end point which is the end of the landslide, calculates the movement vector of the observation point from the displacement measurement values, groups the movement vectors based on the gradient of the movement vectors, obtains the representative movement vector for each group, divides at the starting point of the group by a vertical dividing line, draws a virtual line connecting from the starting point of the group to the end point of the landslide at the gradient of the representative movement vector of the same group up to the intersection with the dividing line of the next group, draws a virtual line connecting from the intersection of the next group to the end point of the landslide at the gradient of the representative movement vector of the next group up to the intersection with the dividing line of the further next group, draws the landslide surface for each group up to the end point position of the landslide end of the group, draws from the starting point of the landslide head to the end point of the landslide end in descending order, and estimates the landslide surface shape.

[0018] Specifically, as shown in FIG. 4, the drawing of the landslide surface shape starts from the head starting point 10 of the landslide surface. Then, as shown in FIG. 5, based on the gradient of the movement vector of group A having the head starting point 10 of the landslide surface, a virtual line (sliding surface 12a estimated by the gradient of the movement vector of group A) connecting the head starting point 10 of the landslide surface to the end point 11 of the landslide surface is drawn by a NURBS curve from the head starting point 10 of the landslide surface to the position of the vertical dividing line dropped from the observation point that is the boundary between group A and group B. Next, as shown in FIG. 6, the point where the vertical dividing line dropped from the observation point that is the boundary between group A and group B intersects with the drawing of the landslide surface shape is taken as the intersection point (ab) 14a, and based on the gradient of the movement vector of group B, a virtual line (sliding surface 12b estimated by the gradient of the movement vector of group B) connecting the intersection point (ab) 14a to the end point 11 of the landslide surface is drawn by a NURBS curve from the intersection point (ab) 14a to the position of the vertical dividing line dropped from the observation point that is the boundary between group B and group C. As a result, a new intersection point (bc) 14b is generated, and based on the gradient of the movement vector of the group starting from the new intersection point, a virtual line connecting the new intersection point to the end point 11 of the landslide surface is continuously drawn by a NURBS curve to the position of the vertical dividing line dropped from the observation point that is the boundary with the next group, and as shown in FIG. 8, the estimated landslide surface shape is drawn from the head starting point 10 of the landslide surface to the end point 11 of the landslide surface. Also, in the drawing of the landslide surface of the group, when there are observation points where sufficient survey data cannot be obtained, as shown in the range from group E to group F in FIG. 7, based on the gradient of the movement vector of the group, a virtual line (sliding surface 12e estimated by the gradient of the movement vector of group E) connecting the intersection point (de) 14d to the end point 11 of the landslide surface is drawn by a NURBS curve from the intersection point (de) 14d to the intersection point (ef) 14e which is the position of the vertical dividing line dropped from the observation point that is the starting point of group F. Regarding the drawing by a NURBS curve, although it is assumed to be the drawing by a spline curve of general CAD software, it is not limited to this.

[0019] (Regarding the drawing of the landslide surface shape in descending order) Here, the drawing of the landslide surface shape estimated in the present invention is performed in descending order from the group having the landslide head. As shown in FIG. 9, not only the landslide surfaces of the drawn groups but also the landslide surfaces of the next groups can be predicted, which not only helps to quickly grasp the overall image but also increases the judgment materials when reflecting the information such as the geology and the cause of occurrence described above.

[0020] (Regarding the comparison and evaluation of the drawn landslide surface and the actual landslide surface) FIG. 10 shows an example in which the landslide surface 15 drawn by the method for estimating the landslide surface shape according to the present invention is compared with the actual landslide surface 16 reflecting the boring results. Compared with the initial landslide surface 12 formed by the curve connecting the position of the head start point 10 of the landslide surface and the end point 11 of the end part of the landslide surface based on the gradient of the movement vector around the conventional landslide cliff 05, the landslide surface 15 drawn according to the present invention shows a difference in the landslide surface depth from the actual landslide surface 16, but there is no significant difference in the landslide surface shape. Thus, since the present invention can estimate the landslide surface shape with a certain accuracy, when the depth of an actual landslide surface at a certain location is determined by boring work, it is possible to easily infer from the landslide surface shape whether the depth of the next boring point is shallower or deeper than that of the previous boring point, and prevent misjudgment of the depth during boring.

[0021] (Conclusion) From the above, the present invention is particularly excellent in speed and ease among the methods for estimating the landslide surface based on the displacement measurement values of the terrain before the landslide and the terrain after the landslide, and satisfies a certain accuracy. Therefore, it is beneficial for ensuring safety in disaster recovery activities and quickly avoiding and reducing the risk of secondary disasters.

Explanation of symbols

[0022] 01 Terrain before landslide 02 UAV-mounted laser scanner 03 Crack 04 Terrain after landslide 05 Landslide Cliff 06 Observation Point Before Landslide 07 Observation Point After Landslide 08 Gradient of Movement Vector of Observation Point 09 Gradient of Movement Vector of Group 10 Head Starting Point (of Landslide Surface) 11 Ending Point (of Landslide Surface) 12 Initial Landslide Surface (drawn based on the head, gradient of movement vectors around the landslide cliff, and the end part) 12a Landslide Surface Estimated by Gradient of Movement Vector of Group A 12b Landslide Surface Estimated by Gradient of Movement Vector of Group B 12e Landslide Surface Estimated by Gradient of Movement Vector of Group E 13 Movement Vector 14 Intersection Point of the Vertically Divided Line from the Observation Point and the Drawn Landslide Surface 14a Intersection Point (ab) 14b Intersection Point (bc) 14d Intersection Point (de) 14e Intersection Point (ef) 15 Drawn Landslide Surface 16 Landslide Surface by Boring Survey

Claims

【Claim 1】 In a method for estimating the landslide surface shape that draws the landslide surface from the starting point of the landslide head to the end point that is the end of the landslide and estimates the landslide surface shape in a two-dimensional vertical cross-section from the displacement measurement values of the ground surface, calculate the movement vector of the observation point from the displacement measurement values, group the movement vectors based on the gradient of the movement vectors, obtain the representative movement vector for each group, at the starting point of the group, divide by a vertical dividing line, using the sliding surface estimated by the gradient of the representative movement vector of the same group as a virtual line, draw the virtual line connecting the starting point of the group and the end point of the landslide end to the intersection with the dividing line of the next group, successively draw the virtual line connecting the intersection of the next group and the end point of the landslide end to the intersection with the dividing line of the further next group, similarly draw the virtual line for each group up to the end point position of the landslide end of the group, A method for estimating the landslide surface shape, characterized by drawing the virtual line from the starting point of the landslide head to the end point of the landslide end in descending order.

Images