Method for estimating three-dimensional landslide surface shape

Abstract

Based on the displacement measurement values of the terrain before and after landslide occurrence, provide a method for estimating a three-dimensional landslide surface shape that ensures a certain degree of accuracy while being rapid and easy, even at locations with special causes of occurrence and movement patterns. 【Solution means】Obtain the movement vectors of the observation points from the survey results before and after landslide occurrence, divide the landslide occurrence range into areas by drawing main survey lines, secondary survey lines, and transverse lines, group the movement vectors under the main survey lines and secondary survey lines by gradient, draw the estimated shape of the landslide surface so as to sequentially connect from the head of the landslide to the end of the landslide with the gradient of each group, the transverse lines reflect the gradients of the landslide cliffs and cracks on both side surfaces of the landslide occurrence range, and give the values calculated by drawing at the intersection points with the main survey lines or secondary survey lines, draw the two-dimensional landslide surface shape so as to sequentially connect from one side surface to the other side surface, reflect these estimated values on the topographic map, and create an estimated map of the three-dimensional landslide surface shape.

Description

Technical Field

[0001] The present invention relates to a method for estimating the slip surface shape of a landslide based on displacement measurement values of the terrain before the occurrence of the 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 triggered by cut earthworks or natural phenomena such as earthquakes and heavy rains). 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 measures 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 ensures speed, ease, and a certain degree of accuracy based on the terrain, geology, and cause of occurrence is desired. As suppression work carried out during a landslide, the Landslide Prevention Technology Guidelines shown by the Ministry of Land, Infrastructure, Transport and Tourism in 2008 include surface water drainage work, groundwater drainage work, drainage work, embankment work, erosion prevention work using river structures, etc. By estimating the landslide surface shape, the position and depth of boring excavation, the amount of embankment, and the method of suppression work are determined, and the construction is carried out.

[0003] Among the above-mentioned suppression work, the groundwater drainage work is an important construction for stabilizing the slope and preventing the occurrence of secondary landslides by draining the groundwater remaining on the landslide surface after the occurrence of the landslide. Based on the estimated value of the landslide surface shape, the depth, position, and excavation direction of boring excavation are determined. As a method for estimating this landslide surface shape, the method of Patent Document 1 is known. As described in the specification

[0046] , "As shown in FIG. 11, the landslide surface is set by connecting the landslide constituent points PC in the same mesh group MSG in order." A continuous mesh group from the head to the end of the landslide is selected, and using the information of the movement vectors on the mesh, it is a method of drawing from the starting point of the landslide head to the end point of the end. In addition, the applicant has invented a method for estimating the two-dimensional landslide surface shape as in Patent Document 2. However, under certain conditions, there may be a large deviation between the estimated value and the landslide surface depth (hereinafter referred to as the measured value) grasped by boring excavation or the like in these conventional landslide surface shape estimation methods. For example, when the shape of the ground collapsed due to landslide is bowl-shaped, the cause of the change may be on the side of the landslide occurrence range. Not only the sliding from the landslide head with the highest elevation to the end with the lowest elevation, but also a large amount of soil blocks sliding from the side to the center are generated. Therefore, when a survey line connecting from the landslide head to the landslide end is drawn near the side surface in the width direction of the landslide (or a group of meshes is selected) and the landslide surface shape under the survey line is drawn two-dimensionally, a large deviation between the estimated value and the measured value is likely to occur. Furthermore, when the original terrain has characteristics different from the normal, such as clayey soil deep underground, even when the landslide surface shape is estimated under the survey line (or mesh) provided at the center in the width direction of the landslide occurrence range, a large deviation between the estimated value and the measured value may occur. Therefore, in order to perform boring excavation in groundwater drainage work safely and efficiently, even in places with landslide causes and movement forms that are not common or have special terrain and geology, a landslide surface shape estimation method with a certain degree of accuracy while being rapid and easy is desired.

[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 blocks that have slid due to the occurrence of the landslide. As a method for grasping the volume of the slid soil blocks, a measurement line is drawn at approximately the center in the width direction of the landslide occurrence range, connecting from the head of the landslide to the end of the landslide. A two-dimensional landslide surface shape is drawn from the movement vectors under the measurement line, and based on this shape, the volume of the entire landslide soil block 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, topography, or geology, there is a possibility that the actual volume is larger than the estimated volume, and there is a concern that the risk of secondary disasters increases due to insufficient embankment or inappropriate selection of the suppression method. Here, it is possible to consider a method of estimating the volume of the landslide soil block three-dimensionally by increasing the number of measurement lines connecting from the head of the landslide to the end of the landslide for drawing the landslide surface shape and estimating more two-dimensional landslide surface shapes in the direction of the measurement lines. However, as described above, when estimating the landslide surface shape based on the measurement lines 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] Also, in the above-mentioned suppression work, when boring excavation is carried out, the depth of the landslide surface can be grasped according to the soil quality and the amount of groundwater. On the other hand, since the method of estimating the landslide surface shape is a method of reading the surface topography change and estimating the landslide surface shape in the ground, it is not necessarily consistent with the measured value as a premise. Therefore, in the work at many landslide occurrence sites, the landslide surface shape based on boring, etc. (hereinafter, the landslide surface shape based on the measured value) is grasped, and the cause analysis of the occurrence of the landslide, etc. is carried out from this landslide surface shape based on the measured value, which is used for future risk prediction and preventive measures. However, there are also problems in grasping the landslide surface shape based on these measured values. That is, when the landslide occurrence range is wide or the ground has irregular features, the number of boring excavations must be increased. This requires cost and time, and it can be said that there is a demand to efficiently grasp the shape of the landslide surface with a certain degree of accuracy using a small number of measured values.

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0007] The present invention is based on displacement measurement values of the terrain before landslide occurrence and the terrain after landslide occurrence, and can estimate a three-dimensional landslide surface shape with a certain degree of accuracy while providing rapidity and ease, even in places where the causes of landslide occurrence and movement forms are not common or have specific terrains and geologies. Furthermore, an object of the present invention is to provide a method that can quickly and easily set the next appropriate boring excavation position based on the landslide depth by actual boring excavation or the like.

Means for Solving the Problems

[0008] To solve the above problems, the three-dimensional landslide surface shape estimation method according to the present invention estimates the landslide surface shape from the displacement measurement values of the ground surface, and draws the landslide surface from the starting point of the landslide head to the end point which is the end part of the landslide. In this method, the landslide surface shapes under the main survey line and the sub-survey line which are the survey lines in the length direction of the landslide occurrence range are estimated according to the landslide movement direction, and the landslide surface shape of the transverse line in the width direction of the landslide occurrence range is estimated based on the estimation results of the landslide surface shapes under the main survey line and the sub-survey line and the gradients of the landslide cliffs or cracks on both sides of the landslide occurrence range, thereby estimating the three-dimensional solid landslide surface shape. It is characterized by the above. In addition to the above features, a main survey line is located at a substantially central part in the width direction of the landslide occurrence range and connects from the landslide head to the landslide end, and sub-survey lines are drawn so as to sandwich the main survey line on the left and right. Then, a transverse line is drawn at a substantially central part in the length direction of the landslide occurrence range to connect the left side surface and the right side surface of the landslide occurrence range and intersect with the main survey line or the sub-survey line. A transverse line is drawn so as to sandwich the transverse line vertically, and the landslide occurrence range is divided into areas.

[0009] More specifically, in a method of estimating the landslide surface shape from the displacement measurement values of the ground surface, and drawing the landslide surface from the starting point of the landslide head to the end point which is the end of the landslide, the movement vector of the observation point is calculated from the displacement measurement values of the ground surface, and a main measurement line is located at approximately the center in the width direction of the landslide occurrence range and connects from the landslide head to the landslide end, auxiliary measurement lines sandwiching the main measurement line on the left and right, and a transverse line connecting the left and right sides of the landslide occurrence range and intersecting the main measurement line or and the auxiliary measurement lines are drawn. The movement vectors are grouped based on the gradient of the movement vectors under the main measurement line, 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. A virtual line connecting from the starting point of the group to the end point of the landslide with the gradient of the representative movement vector of the same group is drawn to the intersection with the dividing line of the next group, and from the intersection of each subsequent group in sequence, a virtual line connecting from the intersection to the end point of the landslide with the gradient of the representative movement vector of the next group is drawn to the intersection with the dividing line of the next subsequent group. The landslide surface is drawn for each group up to the end point position of the landslide of the group, and a two-dimensional landslide surface shape is drawn from the starting point of the landslide head to the end point of the landslide in descending order. The auxiliary measurement lines draw a two-dimensional landslide surface shape from the starting point of the landslide head to the end point of the landslide in descending order in the same manner as the main measurement line. From one side under the transverse line, a spline curve connecting to the intersection of the next main measurement line or the auxiliary measurement line under the transverse line with the gradient of the landslide cliff or and crack on the one side is drawn, and from the intersection which is the end point of the sequentially drawn virtual line, a spline curve connecting to the intersection of the next main measurement line or the auxiliary measurement line is drawn. A spline curve connecting the intersection with the auxiliary measurement line one before the end of the other side and the end of the other side is drawn with the gradient of the landslide cliff or and crack on the other side, and a two-dimensional landslide surface shape is drawn from the one side to the other side, which is characterized by this. Furthermore, in addition to the above features, after estimating the three-dimensional landslide surface shape from the displacement measurement values of the ground surface by a three-dimensional landslide surface shape estimation method, the actual measurement value of the landslide surface depth found by ground excavation within the landslide occurrence range, and a two-dimensional or three-dimensional landslide surface shape is drawn based on the gradient of the landslide cliff or crack surrounding the landslide occurrence range. The three-dimensional landslide surface estimated shape drawn by the three-dimensional landslide surface shape estimation method is compared and verified with the actual measurement value of the landslide surface depth and the two-dimensional or three-dimensional landslide surface shape drawn based on the gradient of the landslide cliff or crack surrounding the landslide occurrence range, and a step of determining the ground excavation position within the next landslide occurrence range is added, which is a feature of this invention.

Advantages of the Invention

[0010] The present invention is an invention that utilizes the two-dimensional landslide surface shape estimation method of Patent Document 2 by the applicant. The three-dimensional landslide surface shape drawing method according to the present invention is a method that retains the advantage of "not requiring multiple analyses and being easy to enhance the rapidity of drawing the landslide surface shape" described in the specification of Patent Document 2

[0015] . Therefore, even when estimating the landslide surface shape under multiple measurement lines or cross lines, rapidity and ease can be maintained. In addition, not only the sliding of the landslide that slides from the landslide head with a high elevation to the landslide end with a low elevation, but also the irregular sliding caused by the landslide cliff on the side of the landslide occurrence range and the original terrain and geological features can be grasped by estimating the landslide surface shape under the cross line. Since it is possible to estimate the landslide surface shape with higher accuracy than the prior art, the accuracy of grasping the volume of the soil mass that has slid due to the boring excavation position and the landslide is also increased, which can be used to select the appropriate construction of the restraining works and anti-sliding works and ensure the safety of the construction workers. Furthermore, by comparing and verifying the measured values of the landslide surface depth found in boring excavation work, etc., the three-dimensional landslide surface shape drawn based on the gradient of the landslide cliff or crack, and the estimated shape of the three-dimensional landslide surface according to the present invention, it is possible to more efficiently grasp the landslide surface shape of the entire landslide occurrence range, set the next appropriate boring excavation position, reduce costs by decreasing the number of boring excavations, and greatly improve work efficiency.

Brief Description of the Drawings

[0011]

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Mode for Carrying Out the Invention

[0012] 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.

[0013] (Regarding the flow of the estimation method according to the present invention) An embodiment of the method for estimating the 3D landslide surface shape according to the present invention will be described based on the process flow diagram of FIG. 1. First, the displacement measurement value of the observation point is obtained from the survey results before and after the landslide, the movement direction of the observation point is calculated, and the movement vector is obtained ([1] Movement vector calculation step). Second, from the topographic map after the landslide, the landslide occurrence range is specified, and main survey lines, secondary survey lines, and cross-section lines are drawn in the landslide occurrence range to divide it into areas ([2] Area division step). Third, the movement vectors under the main survey line and the secondary survey line are grouped according to the gradient of the vectors, and the gradient for each group is calculated ([3] Grouping step of movement vectors). Fourthly, for the main survey line and the secondary survey line, draw the estimated shape of the two-dimensional landslide surface so as to sequentially connect from the landslide head to the landslide end with the gradient for each group calculated by the grouping step of the movement vectors. ([4] Step of estimating the two-dimensional landslide surface shape under the main survey line and the secondary survey line) Fifthly, for the transverse line, reflect the gradients near the landslide cliffs on both side surfaces of the landslide occurrence range corresponding to the starting point and the ending point, and give the values calculated by the drawing of the estimated shape of the two-dimensional landslide surface of the main survey line or the secondary survey line to the intersections of the transverse line with the main survey line and the transverse line with the secondary survey line, and draw the two-dimensional landslide surface shape so as to sequentially connect from one side surface to the other side surface. ([5] Step of estimating the two-dimensional landslide surface shape under the transverse line) Sixthly, reflect the estimated values of the two-dimensional landslide surface shapes drawn under the main survey line, the secondary survey line and the transverse line on the topographic map after the landslide occurs, and create an estimated map of the three-dimensional landslide surface shape ([6] Step of estimating the three-dimensional landslide surface shape).

[0014] (Regarding the method for obtaining the displacement measurement value of the terrain) In practicing the present invention, in order to obtain the displacement measurement values of the terrain 01 before the landslide and the terrain 04 after the landslide shown in FIG. 2, the topographic survey results at least at two times are required. Conventionally, core sampling by boring excavation, in-hole tests, and landslide observations using the excavation holes were performed to estimate the landslide surface shape, but it requires advanced technology and costs to perform boring excavation in a form that ensures safety for landslide observations. However, due to the spread of topographic measurement using a UAV-mounted laser scanner 02 in recent years, it is possible to perform the topographic measurement before the landslide and the measurement after the landslide without entering the landslide area. The aerial laser measurement and the measurement method using the UAV-mounted laser scanner 02 as shown in FIG. 2 are desirable in terms of ensuring the safety and speed during observation because the movement vectors of a plurality of observation points can be calculated simultaneously. However, there is no limitation to using movement piles, extensometers, ground surface inclinometers, etc. during the observation and measurement for calculating the movement vectors.

[0015] (Obtain the movement vector from the displacement measurement value at the observation point.) [1] Regarding the moving vector calculation process, as shown in Fig. 3 for example, the observation point 06 of the terrain before the landslide is taken as the starting point, and the observation point 07 of the terrain after the landslide is taken as the end point, and 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 moving distance and the moving direction (the gradient 08 or the angle of the moving vector of the observation point) of the observation point can be calculated.

[0016] (Draw main survey lines, secondary survey lines and transverse lines on the topographic map after the landslide.) [2] As shown in the example of the landslide occurrence location A in Fig. 5, in the area division process, on the topographic map after the landslide, the landslide occurrence range 12 is specified, and the main survey line 13 is located at approximately the center in the width direction of the landslide occurrence range 12 and connects from the landslide head to the landslide end, and the secondary survey lines a14a and b14b are drawn so as to sandwich the main survey line 13 on the left and right, and the transverse line b15b is drawn at approximately the center in the length direction of the landslide occurrence range to connect the left side and the right side of the landslide occurrence range 12 and intersect with the main survey line 13, and the transverse lines a15a and c15c are drawn so as to sandwich the transverse line b15b from above and below to divide the landslide occurrence range 12 into areas. In this example, there are three survey lines (main survey line and secondary survey lines) in the length direction of the landslide occurrence range 12 and three transverse lines in the width direction, and they are arranged at positions close to equal intervals. However, the more the number of the survey lines in the length direction and the transverse lines in the width direction, the finer estimated values can be calculated, and there are no particular limitations on the number of lines and the intervals between the lines. And when the landslide occurrence range 12 is in an irregular shape as in the landslide occurrence location B in Fig. 6, since a straight survey line connecting from the landslide head to the end cannot be drawn, a bent line like the secondary survey line a14a or b14b in the figure can be drawn, or a short survey line like the secondary survey line c14c can be drawn. Also, when it is possible to predict a location where the cause of the change is identified or suspected from the terrain and the moving vector after the landslide, if the survey lines in the length direction or / and the transverse lines in the width direction are provided including that location, the accuracy of the landslide surface shape estimation can be improved.

[0017] (Group the movement vectors according to the gradient of the vectors.) [3]The step of grouping the movement vectors creates a list as shown in FIG. 3 and groups them into groups having gradients of movement vectors with similar tendencies. Conventionally, when drawing the landslide surface shape, as shown in FIG. 4, based on the gradient of the movement vectors around the landslide cliff 05, it is generally drawn as a curve connecting the starting point 10 of the head of the landslide surface and the ending point 11 of the end part of the landslide surface (the landslide surface estimated by this conventional drawing method is hereinafter referred to as the initial landslide surface 16). This initial landslide surface 16 could not sufficiently reflect features such as differences in shapes such as unevenness in the terrain, differences in geology, differences in layer thickness, for example, not only the downward gradient often seen in the gradient of the movement vectors around the landslide cliff 05, but also the possibility of the existence of horizontal or upward gradients depending on the location. However, by listing the numerical values in this way, it is possible to quickly find the observation points showing abnormal values and also easily perform grouping based on the gradient of the movement vectors. 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 described later, at the observation points that are the starting points of each group, they are divided by vertical dividing lines.

[0018] (Calculation of gradients for each group) Then, the gradient 09 of the movement vector of the group is obtained from a plurality of observation points of these groups shown in FIG. 3. In this case, it is advisable to use the median value of the gradients 08 of the movement vectors of each observation point. The reason for using the median value is that there may be outliers at the observation points due to the accidental presence of large rock masses, etc., and if the average value is used, the value will deviate greatly from the center. Also, when performing surveying using the UAV-mounted laser scanner 02, for example, it is assumed that there are observation points where sufficient survey data cannot be obtained due to the density of vegetation on the slope where vegetation work has been carried out. In such a case, the movement vectors of the said observation points are excluded from the objects for calculating the median value, and the gradient 09 of the movement vector of each group is obtained.

[0019] (Regarding the estimation of the two-dimensional landslide surface shape under the main survey line and the secondary survey lines) [4] The step of estimating the two-dimensional ground slide surface shape below the main measurement line and below the sub-measurement line will be described with reference to the drawings of an embodiment of the method for estimating the ground slide surface shape shown in FIGS. 7 to 11. These figures are for illustrative purposes and show the ground slide surface shape at locations different from the ground slide occurrence ranges in FIGS. 4 and 5. First, as shown in FIG. 7, the drawing of the landslide surface shape starts from the head start point 10 of the landslide surface. Next, as shown in FIG. 8, based on the gradient of the movement vector of group A having the head start point 10 of the landslide surface, a virtual line 18a (slip surface 18a estimated by the gradient of the movement vector of group A) connecting the head start point 10 of the landslide surface to the end point 11 of the landslide surface is drawn by a NURBS curve from the head start point 10 of the landslide surface to the position of the vertical division line dropped from the observation point that is the boundary between group A and group B. Then, as shown in FIG. 9, the point where the vertical division 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 defined as the intersection point (ab) 19a, and based on the gradient of the movement vector of group B, a virtual line 18b (slip surface 18b estimated by the gradient of the movement vector of group B) connecting the intersection point (ab) 19a to the end point 11 of the landslide surface is drawn by a NURBS curve from the intersection point (ab) 19a to the position of the vertical division line dropped from the observation point that is the boundary between group B and group C. As a result, a new intersection point (bc) 19b is generated, and as shown in FIG. 10, based on the gradient of the movement vector of the group starting from the new intersection point, a virtual line 18 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 division line dropped from the observation point that is the boundary with the next group, and finally, as shown in FIG. 11, the estimated landslide surface shape is drawn from the head start point 10 of the landslide surface to the end point 11 of the landslide surface. However, when drawing the landslide surface of the group, there may be observation points where sufficient survey data cannot be obtained. In such a case, as shown in the range from group E to group F in FIG. 10, based on the gradient of the movement vector of the group, a virtual line 18e (slip surface 18e estimated by the gradient of the movement vector of group E) connecting the intersection point (de) 19d to the end point 11 of the landslide surface is drawn by a NURBS curve from the intersection point (de) 19d to the intersection point (ef) 19e which is the position of the vertical division line dropped from the observation point that is the start 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.

[0020] (Regarding drawing the landslide surface shape in descending order) In addition, the drawing of the two-dimensional landslide surface shape estimated under the main survey line and the sub-survey line is performed in descending order from the group having the landslide head. As shown in FIG. 12, not only the sliding surfaces of the drawn group but also the sliding surfaces of the next group 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.

[0021] (Regarding estimation of the two-dimensional landslide surface shape under the cross-section line) [5] The process of estimating the two-dimensional landslide surface shape under the cross-section line is as follows: After the drawing of the two-dimensional landslide surface shapes under the main survey line and the sub-survey line is completed, for the cross-section lines a15a, b15b, and c15c shown in FIG. 5, the two-dimensional landslide surface shapes under the respective cross-section lines are drawn according to the following procedure. FIG. 13 is a diagram showing the ground sliding surface shape below the cross line a15a. The drawing of the ground sliding surface shape in this figure starts from the left side head 21. First, at the intersections (ab) 22a, (bc) 22b, and (cd) 22c, which are the intersections of the cross line a15a and the main survey line or the secondary survey line, the shape values of the ground sliding surface obtained by estimating the two-dimensional ground sliding surface shape of the main survey line and the secondary survey line are given. Second, based on the gradient of the landslide cliff of the left side head 21, a NURBS curve connecting from the left side head 21 to the intersection (ab) 22a of the secondary survey line a14a and the cross line a15a is drawn. Third, starting from the intersection (ab) 22a, a NURBS curve connecting to the intersection (bc) 22b of the main survey line 13 and the cross line a15a is drawn. Next, starting from the intersection (bc) 22b, a NURBS curve connecting to the intersection (cd) 22c of the secondary survey line b14b and the cross line a15a is drawn. Fourth, since the intersection (cd) 22c is the intersection one before the right side head 23, based on the gradient of the landslide cliff of the right side head 23, a NURBS curve connecting from the right side head 23 to the intersection (cd) 22c of the secondary survey line b14b and the cross line a15a is drawn. Then, sequentially, the two-dimensional ground sliding surface shapes of the cross lines b and c are drawn. In this embodiment, the drawing is performed in order from the left side to the right side, but there is no problem in drawing from either the left or the right side, and there is no problem in performing the two-dimensional ground sliding surface shape from any cross line.

[0022] (Regarding the estimation of the three-dimensional ground sliding surface shape) [6]The process of estimating the three-dimensional landslide surface shape is, as described above, to estimate the landslide surface shapes under the main survey line and the secondary survey line, which are survey lines in the length direction of the landslide occurrence range, and to estimate the landslide surface shape of the transverse line in the width direction of the landslide occurrence range based on the estimation results of the landslide surface shapes under the main survey line and the secondary survey line and the gradients of the landslide cliffs on both sides of the landslide occurrence range, thereby estimating the three-dimensional solid landslide surface shape. For example, as shown in FIG. 14, the three-dimensional solid landslide estimated shape can be represented as a contour map by drawing a contour map using CAD software or the like. Then, the volume of the entire landslide mass in the landslide occurrence range can be calculated from the difference between the contour map of the landslide surface in the landslide occurrence range and the contour map of the ground surface in the landslide occurrence range.

[0023] ([7] Process of verifying the shape based on measured values and the estimated shape) FIG. 15 is a process flow diagram adding the process of verifying the shape based on measured values and the estimated shape, [7], after the six processes shown in FIG. 1. An example of this process will be described below. The process of verifying the shape based on measured values and the estimated shape, [7], consists of four processes shown in the right figure of FIG. 15: [a] grasping the landslide depth (measured value) by boring excavation or the like, [b] creating topographic data or and landslide surface contour map based on the measured values, [c] comparing the measured values and the estimated values using the topographic data or the landslide surface contour map, [d] extracting the next boring excavation position. First, the process of grasping the landslide depth (measured value) by boring excavation or the like, [a], is a process of performing boring excavation based on the estimated landslide surface shape and obtaining the measured values from the actual landslide depth. The location where the measured values are obtained is taken as the boring position 24 shown in FIG. 16. Second, the step of creating terrain data or a slip surface contour map based on measured values is, in this example, a step of creating terrain data of the slip surface based on measured values or a slip surface contour map based on the gradient of the landslide cliff or crack surrounding the landslide depth and the landslide occurrence range 12 at the boring position 24. Since the boring position 24 is the intersection of the main survey line 13 of the landslide occurrence range 12 and the transverse line b15b, as shown in FIG. 17, it can be represented by the two-dimensional estimated shape of the slip surface of the transverse line b15b. The drawing procedure in this figure is to draw a NURBS curve of the gradient of the landslide cliff or crack connecting the landslide depth 25 at the boring position 24 and the right-side head 23, and further draw a NURBS curve of the gradient of the landslide cliff or crack connecting the landslide depth 25 at the boring position 24 and the left-side head 21, so as to draw the slip surface shape 26 below the transverse line b based on measured values. Also, regarding the drawing of the three-dimensional slip surface shape, as shown in FIG. 18, based on the measured value of the landslide depth at the boring position 24 and the gradient of the landslide cliff or crack surrounding the landslide occurrence range 12, a contour map can be drawn using general CAD software. This figure is drawn using the landslide depths at multiple boring positions 24, but if there are measured values at one or more locations, it can be drawn. As will be described later, since the comparison between the measured value and the estimated value performed in the next step can be performed only with the terrain data, it is not always necessary to create a slip surface contour map within this step.

[0024] Third, the step of comparing the measured value with the estimated value using the terrain data or the slip surface contour map is a step of comparing the landslide depths at the same points of the measured value and the estimated value, or obtaining the difference by quantification. The comparison using terrain data is a step of obtaining the difference from the quantified landslide depth. For example, the estimated landslide depths at each point of the three-dimensional estimated shape of the slip surface drawn in the steps [1] to [6] above are quantified, and similarly, the landslide depth based on the measured value is quantified, and the difference in the landslide depth can be obtained by comparison. It can be determined that there is a high possibility that the ground in the area or at the point where this difference is large has irregular characteristics. Comparing using the slip surface contour map is a process of grasping the overall image of the landslide occurrence range by comparing two maps. For example, in FIG. 17 comparing the 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 the measured values, the maximum deviation point 27 between the estimated value and the measured value becomes clear. Also, in FIGS. 14 and 18 comparing the three-dimensional landslide surface shapes, the difference in the number of contour lines below the transverse line b15b from the intersection with the secondary measurement line a14a to the landslide cliff on the left side of the illustration can be grasped. By looking at these comparison diagrams, construction workers can quickly grasp the overall image of the landslide surface shape. Fourthly, the step of extracting the next boring excavation position [d] is a step of evaluating the difference in the terrain data obtained by the step [c] and the difference in features seen in the slip surface contour map, and determining the next boring excavation position. For example, in FIG. 17, it is to grasp an area where it is difficult to estimate the landslide surface shape from surface changes such as the maximum deviation point 27 between the estimated value and the measured value, and select a candidate 28 for the next boring position. By this step, not only does the accuracy of grasping the overall shape of the landslide range increase by grasping in advance the irregular features in grasping the landslide surface shape of the landslide occurrence range, but it also becomes easy to efficiently reduce the number of boring excavations required, leading to cost and time reduction. By repeating these steps from [a] to [d], the landslide surface shape of the entire landslide occurrence range can be grasped more efficiently.

[0025] (Conclusion) From the above, the present invention is based on the displacement measurement values of the terrain before and after the landslide, and can estimate a three-dimensional landslide surface shape with rapidity and ease while ensuring a certain degree of accuracy even in places with general or specific terrain and geology where the cause and movement form of the landslide are not common. Furthermore, it is beneficial for providing a method that can quickly and easily set the next appropriate boring excavation position based on the landslide depth by actual boring excavation, etc.

Explanation of Signs

[0026] 01 Topography before landslide 02 UAV-mounted laser scanner 03 Crack 04 Topography after landslide 05 Sliding 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 Landslide occurrence range 13 Main survey line 14 Secondary survey line 14a Secondary survey line a 14b Secondary survey line b 14c Secondary survey line c 15 Cross line 15a Cross line a 15b Cross line b 15c Cross line c 15d Cross line d 16 Initial sliding surface (drawn based on the head, gradient of movement vector around the sliding cliff, and the end part) 17 Movement vector 18a Sliding surface estimated by the gradient of the movement vector of group A 18b Sliding surface estimated by the gradient of the movement vector of group B 18e Sliding surface estimated by the gradient of the movement vector of group E 19 Intersection point of the vertical dividing line from the observation point and the drawn sliding surface 19a Intersection point (ab) 19b Intersection point (bc) 19d Intersection point (de) 19e Intersection point (ef) 20 Drawn sliding surface 21 Left side head 22a Intersection point (ab) 22b Intersection point (bc) 22c Intersection point (cd) 23 Right side head 24 Bowling positions 25 Landslide depth of bowling position 24 26 Landslide surface shape under the transverse line b drawn based on the measured values 27 Point with the maximum deviation between the estimated value and the measured value 28 Candidate for the next bowling position

Claims

1. In this method, the shape of the landslide surface is estimated from the displacement measurements of the ground surface, and the landslide surface is drawn from the head of the landslide as the starting point to the end point, which is the end of the landslide. The shape of the landslide surface under the main and secondary survey lines, which are the longitudinal survey lines of the landslide area, was estimated according to the direction of landslide movement. In addition, the shape of the landslide surface on the transverse line of the landslide occurrence area is estimated based on the estimated results of the landslide surface shape under the main survey line and the secondary survey line and the slopes of the scarps and / or cracks on both sides of the landslide occurrence area. Estimating the three-dimensional shape of the landslide surface A method for estimating three-dimensional landslide surface shape, characterized by:

2. A main survey line is drawn at the approximate center of the width of the landslide area, connecting the head of the landslide to the end of the landslide, and secondary survey lines are drawn on either side of the main survey line. Then, draw a transverse line at approximately the center of the length of the landslide occurrence area, connecting the left side and right side of the landslide occurrence area and crossing the main survey line and / or the secondary survey line, and draw transverse lines so as to sandwich the transverse line above and below. Divide the landslide area into areas 2. The method for estimating a three-dimensional landslide surface shape according to claim 1,

3. In this method, the shape of the landslide surface is estimated from the displacement measurements of the ground surface, and the landslide surface is drawn from the head of the landslide as the starting point to the end point, which is the end of the landslide. Calculate the movement vector of the observation point from the displacement measurement value of the ground surface, Draw a main survey line located approximately in the center of the width of the landslide area, connecting the landslide head to the landslide end, secondary survey lines on either side of the main survey line, and a transverse line connecting the left and right sides of the landslide area and intersecting the main survey line and / or the secondary survey line. grouping the motion vectors based on the gradient of the motion vectors under the main survey line; A representative motion vector is obtained for each of the groups; dividing the group at its origin by a vertical dividing line; A virtual line is drawn from the starting point of the group to the end point of the landslide to the gradient of the representative movement vector of the group to the intersection with the dividing line of the next group; A virtual line is drawn from the intersection of the next group to the end point of the landslide to the slope of the representative movement vector of the next group, and then to the intersection with the division line of the next group. Draw a landslide surface for each group up to the end position of the landslide toe of the group; Draw a two-dimensional landslide surface shape from the start point of the landslide head to the end point of the landslide toe in descending order; The secondary survey lines are drawn in the same manner as the primary survey lines, to depict a two-dimensional landslide surface shape from the starting point of the landslide head to the end point of the landslide toe in descending order; Draw a spline curve connecting the slope of the cliff or crack on one side of the transverse line to the next intersection of the main survey line or the secondary survey line under the transverse line, and draw a spline curve connecting the intersection that is the end point of the drawn virtual lines to the next intersection of the main survey line or the secondary survey line. A spline curve connecting the intersection point of the other side end with the secondary survey line immediately before the other side end and the other side end is drawn with the slope of the cliff or crack of the other side, and a two-dimensional landslide surface shape is drawn from the one side to the other side. A method for estimating three-dimensional landslide surface shape,

4. After estimating the three-dimensional shape of the landslide surface from the measured displacement of the ground surface using a three-dimensional landslide surface shape estimation method, The 3D shape of the landslide surface is drawn based on the actual measured value of the landslide surface depth determined by excavating the ground within the landslide area and the slope of the scarp or crack surrounding the landslide area. comparing and verifying the three-dimensional landslide surface estimated shape drawn by the three-dimensional landslide surface shape estimation method with a two-dimensional or three-dimensional landslide surface shape drawn based on the actual measured value of the landslide surface depth and the gradient of the scarp and / or crack surrounding the landslide occurrence range; A process was added to determine the location of ground excavation within the area where the next landslide will occur. The method for estimating a three-dimensional landslide surface shape according to claim 1, 2 or 3,

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