JP7708446B2 - Method for estimating landslide surface shape - Google Patents
Method for estimating landslide surface shapeInfo
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Description
本発明は、地すべり発生前の地形と地すべり発生後の地形の変位測定値に基づき、地すべりのすべり面形状を推定する方法に関するものである。 The present invention relates to a method for estimating the shape of a landslide slide surface based on displacement measurements of the topography before and after the landslide occurs.
地すべり面形状は、地すべり発生現場の地形や地質、発生原因（切土工事、または、地震や豪雨等の自然現象を誘因として発生する等）によって異なる。また、地すべり面形状の推定を必要とする機会の多くは災害発生時であり、迅速で、かつ精度の高い地すべり面形状の把握を行い、規模や特性に合わせた対策をとることによって、災害復旧活動の安全性を確保し、二次災害の危険性を回避・軽減することができる。つまりは、迅速性、容易性及び地形や地質、発生原因を踏まえた一定の精度を担保する方法が最も望まれる。
特許文献１には、「地すべり土塊を鉛直方向の分割線によって複数のブロックに分割するとともに、変位測定手段が各ブロックの地表に設置されるように分割し、該ブロック毎の地すべり面を高次多項式で設定し、ブロック毎に最小二乗法による正規方程式を組立てて前記ブロック毎の高次多項式のパラメータを少なくとも1つの既知の境界条件に基づいて求め、算出されたブロック毎の前記高次多項式を連ねて地すべり土塊全体のすべり面形状を推定する」とする地すべり面形状の推定方法が開示されている。
The shape of a landslide surface varies depending on the topography and geology of the landslide site and the cause of the landslide (cutting earthworks, or natural phenomena such as earthquakes and heavy rains). In addition, many of the occasions when it is necessary to estimate the shape of a landslide surface occur when a disaster occurs, and by quickly and accurately grasping the shape of a landslide surface and taking measures according to the scale and characteristics of the landslide, it is possible to ensure the safety of disaster recovery activities and avoid or reduce the risk of secondary disasters. In other words, a method that ensures speed, ease, and a certain level of accuracy based on the topography, geology, and cause of the landslide is most desirable.
Patent Document 1 discloses a method for estimating the shape of a landslide surface, which involves "dividing a landslide mass into a plurality of blocks by vertical dividing lines and dividing the mass so that a displacement measuring means is installed on the ground surface of each block, setting the landslide surface of each block as a high-order polynomial, constructing normal equations for each block by the least squares method, determining parameters of the high-order polynomial for each block based on at least one known boundary condition, and estimating the shape of the slide surface of the entire landslide mass by concatenating the calculated high-order polynomials for each block."
しかし、特許文献１に示された技術を用いて地すべり面の形状を推定するためには、高次多項式や誤差式を用いた計算を要し、電子計算機および実行するためのソフトウェアを用いずに算出することは困難であり、かつ、時間を要する。そのため、計測値を分析するための機器、専用ソフトウェアの準備やプログラムの操作が必須となる。 However, to estimate the shape of a landslide surface using the technology shown in Patent Document 1, calculations using higher-order polynomials and error equations are required, and it is difficult and time-consuming to perform calculations without using a computer and software to execute them. Therefore, it is necessary to prepare equipment for analyzing the measured values, special software, and operate the program.
さらに、前記技術を説明した資料である非特許文献１によると、前記技術により地すべり面形状を推定するにあたり、地形データ、計測点の座標、変状（クラックや押し出し）が表れている位置の座標（地すべりの頭部とすべり面末端の位置）、計測点における地表面変位ベクトルの入力を要する上、その解析結果の精度を上げるためには、ブロック区分線の設定 、地中境界点の設定、 頭部滑落崖や亀裂の勾配について入力することが望ましいとされており、知識や経験の有無によって推定される結果の精度が左右されてしまうことがわかる。併せて、地形や地質等の条件によっては、算出されたすべり面の推定結果が実際のすべり面の形状と乖離する課題も生じている。そのため、精度の高い結果を求めるためのプログラム実行は容易であると言い難く、また、迅速性についても必ず担保されるとは言えない。 Furthermore, according to Non-Patent Document 1, which is a document explaining the above-mentioned technology, when estimating the landslide surface shape using the above-mentioned technology, it is necessary to input topographical data, coordinates of measurement points, coordinates of positions where deformations (cracks and extrusions) are observed (positions of the head of the landslide and the end of the slide surface), and ground surface displacement vectors at the measurement points. In addition, in order to improve the accuracy of the analysis results, it is desirable to input the settings of block division lines, underground boundary points, and the gradient of the head scarp and cracks, and it is clear that the accuracy of the estimated results depends on the presence or absence of knowledge and experience. In addition, there is also the issue that the calculated estimated results of the slide surface may deviate from the actual shape of the slide surface depending on the conditions of the topography, geology, etc. Therefore, it is difficult to say that it is easy to run a program to obtain highly accurate results, and it cannot be said that speed is necessarily guaranteed.
そこで、本発明は、地すべり発生前の地形と地すべり発生後の地形の変位測定値に基づき、地すべり面形状を迅速で容易、かつ、一定の精度を満たして推定する手法を提供することを課題とする。 The present invention aims to provide a method for quickly, easily, and with a certain degree of accuracy to estimate the shape of a landslide surface based on displacement measurements of the topography before and after the landslide occurs.
前記課題を解決するため、請求項１に記載の発明は、地すべり頭部を起点とし、地すべり末端部である終点までの地すべり面を描画し、地表の変位測定値から2次元鉛直断面における地すべり面形状を推定する地すべり面形状の推定方法において、前記変位測定値から観測点の移動ベクトルを算出し、前記移動ベクトルの勾配に基づき前記移動ベクトルをグループ分けし、前記グループごとの代表移動ベクトルを求め、前記グループの起点において、鉛直方向の分割線によって分割し、同グループの代表移動ベクトルの勾配により推定されるすべり面を仮想線として、前記グループの起点と地すべり末端部終点とを結ぶ前記仮想線を、次グループの分割線との交点まで描画し、順次次グループの交点と地すべり末端部終点とを結ぶ前記仮想線を、さらに次のグループの分割線との交点まで描画し、前記グループの地すべり末端部終点位置まで同様に、グループごとに前記仮想線を描画することによって、前記地すべり頭部の起点から、降順に前記地すべり末端部の終点まで前記仮想線を描画することを特徴とする。 In order to solve the above problem, the invention described in claim 1 provides a method for estimating a landslide surface shape in which a landslide surface is drawn from a landslide head to an end point which is a landslide end, and the shape of the landslide surface in a two-dimensional vertical cross section is estimated from displacement measurement values of the ground surface, the method comprising: calculating a movement vector of an observation point from the displacement measurement values; classifying the movement vectors into groups based on the gradients of the movement vectors; determining a representative movement vector for each group; dividing the group by a vertical division line at the starting point of the group; and calculating a representative movement vector for each group. The method is characterized in that the slide surface estimated from the gradient of the vector is taken as a virtual line, and the virtual line connecting the starting point of the group and the end point of the landslide terminus is drawn up to the intersection with the dividing line of the next group, and the virtual line connecting the intersection with the end point of the landslide terminus of the next group is successively drawn up to the intersection with the dividing line of the next group, and so on for each group up to the end point of the landslide terminus of the group, thereby drawing the virtual lines from the starting point of the landslide head to the end point of the landslide terminus in descending order.
本発明により、地すべり発生前の地形と地すべり発生後の地形の変位測定値に基づき、地すべり面形状を迅速で容易、かつ、一定の精度を満たして推定する手法を提供することができる。 The present invention provides a method for quickly, easily, and with a certain degree of accuracy to estimate the shape of a landslide surface based on displacement measurements of the topography before and after a landslide occurs.
本発明の実施形態について、図を参照しつつ説明する。但し、この実施の形態に記載されている装置、形状等は特に特定的な記載がない限りは、この発明の範囲を限定する趣旨ではなく、単なる説明例に過ぎない。 The following describes an embodiment of the present invention with reference to the drawings. However, unless otherwise specified, the devices, shapes, etc. described in the embodiment are not intended to limit the scope of the present invention and are merely illustrative examples.
（地形の変位測定値を求める方法について）
本発明を実施するにあたり、図１に示す地すべり発生前の地形０１と地すべり発生後の地形０４の変位測定値を求めるため、少なくとも２時期における地形測量結果を要する。従来は、ボーリング掘削によるコア採取や孔内試験、掘削孔を利用した地すべり観測を行い、地すべり面形状の推定を行っていたが、地すべり観測のために安全性を担保する形でボーリング掘削を行うには高度な技術とコストを要する。しかし、近年ＵＡＶ搭載型レーザスキャナ０２を用いた地形計測の普及により、地すべり発生前の地形と地すべり発生後の測量を踏査せずに行うことができる。航空レーザ測量や、図１において示したようなＵＡＶ搭載型レーザスキャナ０２による測量方法は、同時に複数の観測点の移動ベクトルを算出できるため、観測時の安全性及び迅速性確保の面から望ましい。但し、移動ベクトルの算出のための観測や測量の際に、移動杭、伸縮計、地表面傾斜計等を使用することに限りはない。
(Method of determining topographical displacement measurements)
In carrying out the present invention, in order to obtain displacement measurements of the topography 01 before the landslide and the topography 04 after the landslide as shown in FIG. 1, topographical survey results at least at two times are required. Conventionally, landslide observations using core sampling by boring and borehole testing, and boreholes were used to estimate the shape of the landslide surface, but drilling in a manner that ensures safety for landslide observation requires advanced technology and costs. However, with the recent spread of topographical measurements using UAV-mounted laser scanners 02, it is possible to perform surveys of the topography before the landslide and the topography after the landslide without reconnaissance. Aerial laser surveying and a surveying method using the UAV-mounted laser scanner 02 as shown in FIG. 1 can calculate the movement vectors of multiple observation points simultaneously, and are therefore desirable in terms of ensuring safety and speed during observation. However, there is no limit to the use of moving piles, extensometers, ground surface inclinometers, etc. during observations and surveys for calculating the movement vectors.
（観測点における変位測定値から移動ベクトルを求める。）
図２において、観測点における変位測定値から移動ベクトルを求める例を示す。地すべり発生前の地形の観測点０６を始点、そして、地すべり発生後の地形の観測点０７を終点とし、これらをＸ座標とＹ座標によって位置を特定する。そして、前記始点と前記終点を線で結ぶと、観測点の移動距離と移動方向（観測点の移動ベクトルの勾配０８または角度）を算出することができる。
次に、地すべり発生時の滑落崖０５にあたる地点（以下、地すべり面の頭部起点１０）より始点Ｘの値が大きい観測点、及び、地すべり面の末端部終点１１より始点Ｘの値が小さい観測点はリストから除外し、地すべり面の頭部起点１０を番号１、最後の番号が地すべり面の末端部終点１１となるように、始点Ｘを要素として降順に並べ、リストを作成する。
(The displacement vector is calculated from the displacement measurements at the observation points.)
Figure 2 shows an example of calculating a movement vector from displacement measurements at an observation point. The observation point 06 on the terrain before the landslide occurs is set as the start point, and the observation point 07 on the terrain after the landslide occurs is set as the end point, and their positions are specified by X and Y coordinates. By connecting the start point and the end point with a line, the movement distance and movement direction of the observation point (gradient 08 or angle of the movement vector of the observation point) can be calculated.
Next, observation points whose start point X value is greater than the point corresponding to the cliff 05 at the time the landslide occurred (hereinafter referred to as the head starting point 10 of the landslide surface) and observation points whose start point X value is smaller than the end point 11 of the landslide surface are excluded from the list, and a list is created by arranging the start point X in descending order as an element, so that the head starting point 10 of the landslide surface is number 1 and the last number is the end point 11 of the landslide surface.
（移動ベクトルをベクトルの勾配別にグループ分けする。）
従来、図３で示すように、地すべり面形状を描画する際には、滑落崖０５周辺の移動ベクトルの勾配を基に、地すべり面の頭部起点１０と地すべり面の末端部終点１１の位置を結ぶ曲線で描かれることが一般的であった。（この従来型の描画方法により推定される地すべり面を以下、当初のすべり面１２とする）しかし、実際の地すべり面の頭部起点１０から地すべり面の末端部終点１１の位置までのすべり面は、地形における凹凸等の形状の違い、地質の違い、層厚の違い等があるため、滑落崖０５の周辺における移動ベクトルの勾配によく見られる下方向の勾配だけでなく、場所によっては平面方向や上方向の勾配が存在しうる。そのため、前記図２を例とするようなリストを作成することは、傾向が類似する移動ベクトルの勾配を有するグループ、異常値を示す観測点を速やかに見つけることができるため、「グループごとにすべり面形状の描画を行う」とする本発明の課題解決に必要な移動ベクトルの勾配に基づくグルーピングを容易に行うことができる。後述する地すべり面形状を描画する際には、この各グループの起点となる観測点で、鉛直方向の分割線によって分割する。
(Group the movement vectors by the gradient of the vector.)
Conventionally, as shown in Fig. 3, when drawing the shape of a landslide surface, it was common to draw a curve connecting the position of the head start point 10 of the landslide surface and the position of the end point 11 of the landslide surface based on the gradient of the movement vector around the slide scarp 05. (The landslide surface estimated by this conventional drawing method is hereinafter referred to as the initial slide surface 12.) However, the slide surface from the head start point 10 of the actual landslide surface to the position of the end point 11 of the landslide surface has differences in shape such as unevenness in the topography, differences in geology, differences in layer thickness, etc., so that not only the downward gradient often seen in the gradient of the movement vector around the slide scarp 05, but also the horizontal direction and the upward gradient may exist in some places. Therefore, by creating a list such as that shown in Fig. 2, it is possible to quickly find groups having similar gradients of the movement vectors and observation points showing abnormal values, and therefore it is easy to perform grouping based on the gradient of the movement vectors, which is necessary for solving the problem of the present invention, which is to "draw the shape of the slide surface for each group". When plotting the landslide surface shape described later, each group is divided by a vertical dividing line at the observation point that is the starting point of each group.
（グループ別の勾配の算出）
次に、これらのグループの複数の観測点からグループとしての移動ベクトルの勾配０９を求め、その際には各観測点の移動ベクトルの勾配の中央値を使用する。中央値を使用する理由は、観測点において、偶発的に大きな岩が存在する等により外れ値が存在する恐れがあり、平均値を使用すると値が中央から大きく外れてしまうからである。また、ＵＡＶ搭載型レーザスキャナ０２による測量を行った場合には、例えば、植生工を施した斜面の植生の密生度によって十分な測量データを得られない観測点が存在することが想定される。そのような場合には、前記観測点の移動ベクトルは、中央値の算出の被対象から外し、各グループの移動ベクトルの勾配０９を求める。
(Calculation of gradient by group)
Next, the gradient 09 of the movement vector as a group is calculated from the multiple observation points of these groups, and 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 is a risk of outliers at the observation point due to the accidental presence of a large rock, etc., and if the average value is used, the value will deviate significantly from the center. In addition, when a survey is performed using a UAV-mounted laser scanner 02, it is expected that there will be observation points from which sufficient survey data cannot be obtained due to, for example, the density of vegetation on a slope where vegetation work has been performed. In such cases, the movement vector of the observation point is excluded from the calculation of the median value, and the gradient 09 of the movement vector of each group is calculated.
（移動ベクトルの勾配でグループを作るメリット 特許文献１）
前記移動ベクトルのグルーピング、及び、グループの移動ベクトルの勾配０９の算出を、地すべり面形状の描画の前に行うことは、本発明の課題解決のための手段である。そのため、事前に地すべり斜面の地質や地すべりの発生原因を把握できている場合には、例えば、地すべりが崩落、滑動、流動のいずれにあたるか、または、粘質土すべりか岩盤すべりか、円弧すべりか平面すべりか等、様々な条件を踏まえて、前記移動ベクトルのグルーピング、及び、移動ベクトルの勾配０９の算出ができ、イレギュラーな要素を予め取り除いた形で地すべり面形状の推定ができる。一方で、特許文献１の推定方法は、推定時の解析には、地表線、地表面計測点の位置、地表境界点の位置、計測データ（移動ベクトル）、解析条件選択（多角形平行法、多角形回転法、多項式法）の入力を要し、さらに、地質や発生原因等の情報を反映させようとする場合には、解析条件を変化させながら推定結果の妥当性を高めるものである。つまり、解析結果が出た後、人が分析し、調整し、再度ソフトウェアを利用して解析を行う手法であることから、妥当性の高い推定結果を得るためには時間を要する。よって、本発明の推定方法は、複数回の解析が不要であり、地すべり面形状の描画の迅速性を高めることが容易であると言える。
(Advantages of creating groups based on the gradient of the movement vector, Patent Document 1)
The grouping of the movement vectors and the calculation of the gradient 09 of the movement vectors of the groups before drawing the landslide surface shape are means for solving the problem of the present invention. Therefore, if the geology of the landslide slope and the cause of the landslide are known in advance, the grouping of the movement vectors and the calculation of the gradient 09 of the movement vectors can be performed based on various conditions, such as whether the landslide is a collapse, slide, or flow, whether it is a clayey soil slide or a rock slide, an arc slide, or a planar slide, and the like, and the landslide surface shape can be estimated with irregular elements 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 during estimation, and further, when it is intended to reflect information such as the geology and the cause of the landslide, the validity of the estimation result is improved by changing the analysis conditions. In other words, since this is a method in which after the analysis results are obtained, a person analyzes, adjusts, and then performs analysis again using software, it takes time to obtain highly valid estimation results. Therefore, the estimation method of the present invention does not require multiple analyses, and can be said to easily increase the speed at which the landslide surface shape can be drawn.
（移動ベクトルの勾配でグループを作るメリット 特許文献２）
また、特許文献２において、メッシュごとに較差ベクトルを算出する方法が示されており、本発明に係る推定方法よりも緻密な推定方法といえる。しかし、推定結果の妥当性を高めるために「較差ベクトルの方向に応じて後続のメッシュを選定する」等の記載があり、自動化ができない課題を有する。そのため、断面ではなくメッシュで地すべり形状を捉える特許文献２に係る推定方法を使用すると、断面で推定する本発明の推定方法に比べて、前述のように自動化できない調整箇所が増加することが推察され、災害時等の迅速な地すべり面形状の推定には課題があると言える。よって、本発明のように断面で地すべり面形状を推定する方法の迅速性を高めることは、特許文献２の発明と比較し、異なる有益性をもたらすものである。
(Advantages of creating groups based on the gradient of the movement vector, Patent Document 2)
In addition, Patent Document 2 discloses a method for calculating a difference vector for each mesh, which is a more precise estimation method than the estimation method according to the present invention. However, in order to improve the validity of the estimation result, it is described that "subsequent meshes are selected according to the direction of the difference vector," and this method has a problem in that it cannot be automated. Therefore, when using the estimation method according to Patent Document 2, which captures the landslide shape using meshes rather than cross sections, it is presumed that the number of adjustments that cannot be automated increases as described above compared to the estimation method of the present invention, which estimates using cross sections, and this means that there is a problem in estimating the landslide surface shape quickly during disasters, etc. Therefore, improving the speed of the method of estimating the landslide surface shape using cross sections as in the present invention brings about different benefits compared to the invention of Patent Document 2.
（グループごとに地すべり面を描写すること）
そして、地すべり面形状の描画方法について説明すると、本発明は、地表の変位測定値から２次元鉛直断面における地すべり面形状を推定し、地すべり頭部を起点とし、地すべり末端部である終点までの地すべり面を描画する方法において、前記変位測定値から観測点の移動ベクトルを算出し、前記移動ベクトルの勾配に基づき前記移動ベクトルをグループ分けし、前記グループごとの代表移動ベクトルを求め、前記グループの起点において、鉛直方向の分割線によって分割し、前記グループの起点から、同グループの代表移動ベクトルの勾配で地すべり末端部終点とを結ぶ仮想線を、次グループの分割線との交点まで描画し、順次次グループの交点から、次グループの代表移動ベクトルの勾配で地すべり末端部終点とを結ぶ仮想線を、さらに次のグループの分割線との交点まで描画し、前記グループの地すべり末端部終点位置まで、グループごとに地すべり面を描画し、前記地すべり頭部の起点から、降順に前記地すべり末端部の終点まで描画し、地すべり面形状を推定することを特徴とするものである。
(Draw the landslide surface for each group)
The method for depicting the shape of a landslide surface will now be described. In this method, the shape of a landslide surface in a two-dimensional vertical section is estimated from displacement measurement values on the ground surface, and a landslide surface is depicted from a landslide head point to an end point, which is a landslide trailing edge. The method calculates a movement vector of an observation point from the displacement measurement values, groups the movement vectors based on the gradient of the movement vectors, obtains a representative movement vector for each group, divides the group by a vertical division line at the starting point of the group, and Then, a virtual line is drawn connecting the end point of the landslide with the gradient of the representative movement vector of the same group to the intersection with the dividing line of the next group, and then a virtual line is drawn connecting the end point of the landslide with the gradient of the representative movement vector of the next group from the intersection of the next group to the intersection with the dividing line of the next group.Then, a landslide surface is drawn for each group up to the end point of the landslide end of the group, and the landslide surface is drawn in descending order from the starting point of the landslide head to the end point of the landslide end, thereby estimating the shape of the landslide surface.
具体的には、図４で示すように、地すべり面形状の描画は、地すべり面の頭部起点１０から始める。そして、図５で示すように、地すべり面の頭部起点１０を有するグループＡの移動ベクトルの勾配に基づき、地すべり面の頭部起点１０から地すべり面の末端部終点１１とを結ぶ仮想線（グループＡの移動ベクトルの勾配により推定されるすべり面１２ａ）を、地すべり面の頭部起点１０からグループＡとグループＢの境界となる観測点から下された鉛直方向の分割線の位置まで、ＮＵＲＢＳ曲線により描画する。次は、図６で示すように、前記グループＡとグループＢの境界となる観測点から下された鉛直方向の分割線と地すべり面形状の描画が交差する点を交点（ａｂ）１４ａとし、グループＢの移動ベクトルの勾配に基づき、交点（ａｂ）１４ａから地すべり面の末端部終点１１とを結ぶ仮想線（グループＢの移動ベクトルの勾配により推定されるすべり面１２ｂ）を、交点（ａｂ）１４ａからグループＢとグループＣの境界となる観測点から下された鉛直方向の分割線の位置まで、ＮＵＲＢＳ曲線により描画する。これにより新たな交点（ｂｃ）１４ｂが生まれ、新たな交点を起点とするグループの移動ベクトルの勾配に基づき、新たな交点から地すべり面の末端部終点１１とを結ぶ仮想線を、その次のグループとの境界となる観測点から下された鉛直方向の分割線の位置まで、ＮＵＲＢＳ曲線により描画し続け、図８で示すように、地すべり面の頭部起点１０から地すべり面の末端部終点１１まで、推定される地すべり面形状を描画する。また、前記グループの地すべり面の描画において、十分な測量データを得られない観測点が存在する場合には、図７のグループＥからグループＦの範囲で示したように、グループの移動ベクトルの勾配に基づき、交点（ｄｅ）１４ｄから地すべり面の末端部終点１１とを結ぶ仮想線（グループＥの移動ベクトルの勾配により推定されるすべり面１２ｅ）を、交点（ｄｅ）１４ｄからグループＦの起点となる観測点から下された鉛直方向の分割線の位置である交点（ｅｆ）１４ｅまで、ＮＵＲＢＳ曲線により描画する。ＮＵＲＢＳ曲線による描画については、一般的なＣＡＤソフトのスプライン曲線による描画を想定しているが、これに限りはない。 Specifically, as shown in Figure 4, the drawing of the landslide surface shape begins from the head starting point 10 of the landslide surface. Then, as shown in Figure 5, based on the gradient of the movement vector of group A which has the head starting point 10 of the landslide surface, a virtual line connecting the head starting point 10 of the landslide surface to the end point 11 of the landslide surface (slide surface 12a estimated from the gradient of the movement vector of group A) is drawn using a NURBS curve from the head starting point 10 of the landslide surface to the position of a vertical dividing line dropped from the observation point which is the boundary between group A and group B. Next, as shown in Figure 6, the point where the vertical dividing line drawn from the observation point that is the boundary between Group A and Group B intersects with the drawing of the landslide surface shape is designated as intersection (ab) 14a, and based on the gradient of the movement vector of Group B, an imaginary line connecting intersection (ab) 14a to the end point 11 of the landslide surface (slide surface 12b estimated from the gradient of the movement vector of Group B) is drawn using a NURBS curve from intersection (ab) 14a to the position of the vertical dividing line drawn from the observation point that is the boundary between Group B and Group C. This creates a new intersection (bc) 14b, and based on the gradient of the movement vector of the group starting from the new intersection, a virtual line connecting the new intersection to the end point 11 of the landslide surface is drawn using a NURBS curve up to the position of the vertical dividing line dropped from the observation point that is the boundary with the next group, and the estimated shape of the landslide surface is drawn from the start point 10 of the head of the landslide surface to the end point 11 of the landslide surface, as shown in Figure 8. Furthermore, when drawing the landslide surface of the group, if there is an observation point for which sufficient survey data cannot be obtained, as shown in the range from group E to group F in Figure 7, a virtual line connecting intersection point (de) 14d to the end point 11 of the landslide surface (slide surface 12e estimated by the gradient of the movement vector of group E) is drawn as a NURBS curve based on the gradient of the movement vector of the group from intersection point (de) 14d to 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. The drawing using a NURBS curve is assumed to be a spline curve of general CAD software, but is not limited to this.
（降順に地すべり面形状の描画を行うことについて）
ここで、本発明において推定される地すべり面形状の描画は、地すべり頭部を有するグループより降順に行う。図９で示したように、描画したグループのすべり面だけでなく、次のグループのすべり面の予測をすることができ、全体像の把握の迅速化に役立つだけでなく、前述した地質や発生原因等の情報を反映する際に判断材料を増やすことができるからである。
(Drawing the landslide surface shape in descending order)
Here, the estimated landslide surface shape in the present invention is drawn in descending order starting from the group with the landslide head. As shown in Fig. 9, it is possible to predict not only the slide surface of the drawn group but also the slide surface of the next group, which not only helps to quickly grasp the overall picture but also increases the amount of information to be used when reflecting the above-mentioned information on geology and cause of occurrence.
（描画したすべり面と実際のすべり面の比較 評価について）
図１０にて、本発明に係る地すべり面形状の推定方法により描画したすべり面１５とボーリング結果を反映した実際のすべり面１６とを比較した例を示すと、従来の滑落崖０５の周辺の移動ベクトルの勾配を基とする、地すべり面の頭部起点１０と地すべり面の末端部終点１１の位置を結ぶ曲線による当初のすべり面１２と比較し、本発明により描画したすべり面１５は、実際のすべり面１６とすべり面深度には差異が見られるものの、すべり面形状については大きな差異が見られない結果となった。このように本発明は、地すべり面形状を一定の精度で推定できるため、ボーリング作業により一箇所の実際のすべり面の深度が判明すると、次のボーリング地点が前のボーリング地点よりも深度が浅いか深いかを地すべり面形状から容易に推察でき、ボーリング時の深度の見誤りを防ぐことができる。
(Evaluation of the comparison between the drawn slip surface and the actual slip surface)
Figure 10 shows an example of comparing a slide surface 15 drawn by the method for estimating the landslide surface shape according to the present invention with an actual slide surface 16 reflecting the boring results. Compared with the original slide surface 12 drawn by a curve connecting the position of the head start point 10 of the landslide surface and the end point 11 of the landslide surface based on the gradient of the movement vector around the conventional slide cliff 05, the slide surface 15 drawn by the present invention shows a difference in slide surface depth from the actual slide surface 16, but no significant difference in slide surface shape. In this way, the present invention can estimate the landslide surface shape with a certain degree of accuracy, so that once the depth of the actual slide surface at one location is determined by boring work, it is easy to infer from the landslide surface shape whether the next boring point is shallower or deeper than the previous boring point, and misjudgment of the depth during boring can be prevented.
（結論）
以上のことから、本発明は、地すべり発生前の地形と地すべり発生後の地形の変位測定値に基づき、地すべり面を推定する手法のうち、迅速性及び容易性に特に優れ、かつ、一定の精度を満たしていることから、災害復旧活動で安全性を確保し、迅速に二次災害の危険性を回避・軽減するために有益である。
(Conclusion)
In view of the above, among methods for estimating landslide surfaces based on displacement measurements of the topography before and after a landslide occurs, the present invention is particularly excellent in terms of speed and ease and also satisfies a certain level of accuracy, and is therefore useful for ensuring safety in disaster recovery activities and quickly avoiding and reducing the risk of secondary disasters.
０１ 地すべり前の地形
０２ ＵＡＶ搭載型レーザスキャナ
０３ 亀裂
０４ 地すべり後の地形
０５ 滑落崖
０６ 地すべり前の観測点
０７ 地すべり後の観測点
０８ 観測点の移動ベクトルの勾配
０９ グループの移動ベクトルの勾配
１０ （地すべり面の）頭部起点
１１ （地すべり面の）末端終点
１２ 当初のすべり面（頭部、滑落崖周辺の移動ベクトルの勾配、末端部を基に描画した地すべり面）
１２ａ グループＡの移動ベクトルの勾配により推定されるすべり面
１２ｂ グループＢの移動ベクトルの勾配により推定されるすべり面
１２ｅ グループＥの移動ベクトルの勾配により推定されるすべり面
１３ 移動ベクトル
１４ 観測点からの鉛直方向の分割線と描画したすべり面の交点
１４ａ 交点（ａｂ）
１４ｂ 交点（ｂｃ）
１４ｄ 交点（ｄｅ）
１４ｅ 交点（ｅｆ）
１５ 描画したすべり面
１６ ボーリング調査によるすべり面
01 Topography before the landslide 02 UAV-mounted laser scanner 03 Crack 04 Topography after the landslide 05 Scarp 06 Observation point before the landslide 07 Observation point after the landslide 08 Gradient of the movement vector of the observation point 09 Gradient of the movement vector of the group 10 Starting point of the head (of the landslide surface) 11 End point (of the landslide surface) 12 Initial slide surface (landslide surface drawn based on the gradient of the movement vector around the head and scarp, and the end part)
12a: Slide surface estimated from the gradient of the movement vector of group A; 12b: Slide surface estimated from the gradient of the movement vector of group B; 12e: Slide surface estimated from the gradient of the movement vector of group E; 13: Movement vector; 14: Intersection 14a: Intersection (a-b) of the vertical division line from the observation point and the drawn slide surface.
14b Intersection (bc)
14d Intersection (de)
14e Intersection (ef)
15. Drawn slide surface 16. Slide surface from boring survey
Claims (1)
前記変位測定値から観測点の移動ベクトルを算出し、
前記移動ベクトルの勾配に基づき前記移動ベクトルをグループ分けし、
前記グループごとの代表移動ベクトルを求め、
前記グループの起点において、鉛直方向の分割線によって分割し、
同グループの代表移動ベクトルの勾配により推定されるすべり面を仮想線として、前記グループの起点と地すべり末端部終点とを結ぶ前記仮想線を、次グループの分割線との交点まで描画し、
順次次グループの交点と地すべり末端部終点とを結ぶ前記仮想線を、さらに次のグループの分割線との交点まで描画し、
前記グループの地すべり末端部終点位置まで同様に、グループごとに前記仮想線を描画することによって、
前記地すべり頭部の起点から、降順に前記地すべり末端部の終点まで前記仮想線を描画することを特徴とする地すべり面形状の推定方法。 A method for estimating the shape of a landslide surface in which a landslide surface is drawn from the head of the landslide to the end point, which is the end of the landslide, and the shape of the landslide surface in a two-dimensional vertical cross section is estimated from the displacement measurement value of the ground surface ,
Calculating a movement vector of the observation point from the displacement measurement value;
Grouping the motion vectors based on a gradient of the motion vectors;
A representative motion vector is obtained for each of the groups;
dividing the group at its origin by a vertical dividing line;
A slide surface estimated based on the gradient of the representative movement vector of the group is used as a virtual line, and the virtual line connecting the start point of the group and the end point of the landslide to the intersection with the dividing line of the next group is drawn.
The virtual line connecting the intersection point of the next group and the end point of the landslide to the intersection point with the dividing line of the next group is drawn in sequence.
Similarly , the virtual line is drawn for each group up to the end position of the landslide end portion of the group .
A method for estimating a landslide surface shape, comprising drawing the virtual line in descending order from the start point of the landslide head to the end point of the landslide toe.
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| JP2008202994A (en) | 2007-02-16 | 2008-09-04 | Public Works Research Institute | Landslide surface shape estimation method, estimation device, and estimation program |
| US20090161944A1 (en) | 2007-12-21 | 2009-06-25 | Industrial Technology Research Institute | Target detecting, editing and rebuilding method and system by 3d image |
| JP2011058875A (en) | 2009-09-08 | 2011-03-24 | Pasuko:Kk | Method, device and program for measurement of displacement |
| CN109344867A (en) | 2018-08-27 | 2019-02-15 | 中国地质大学（武汉） | A landslide displacement similarity matching method and system based on movement angle difference |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| JP2008202994A (en) | 2007-02-16 | 2008-09-04 | Public Works Research Institute | Landslide surface shape estimation method, estimation device, and estimation program |
| US20090161944A1 (en) | 2007-12-21 | 2009-06-25 | Industrial Technology Research Institute | Target detecting, editing and rebuilding method and system by 3d image |
| JP2011058875A (en) | 2009-09-08 | 2011-03-24 | Pasuko:Kk | Method, device and program for measurement of displacement |
| CN109344867A (en) | 2018-08-27 | 2019-02-15 | 中国地质大学（武汉） | A landslide displacement similarity matching method and system based on movement angle difference |
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