JP2004183340A - Cut earth slope management support system, cut earth slope disruption risk degree determination system used in the system and earth moisture status measuring method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a cut earth slope management support system for supporting determination of timing of traffic restriction, in particular its releasing timing, a cut earth slope disruption risk degree determination system used in the system, and earth moisture status measuring method. <P>SOLUTION: In this cut earth slope management system, the safety factor of the slope is estimated to determine the timing of traffic restriction, in particular the releasing timing without obtaining the safety factor of the cut earth slope as an absolute numerical value by utilizing the effect that the safety factor Q of the cut earth slope is influenced by the precipitation R to relatively change. This depends upon that the safety of the slope has the characteristic of recovery after decline or stop of rainfall. That is, the safety factor of the cut earth slope tends to recover when rainfall is declined or stopped, so that the timing (the inflection point of safety factor of cut earth slope) showing the recovery tendency is grasped to precisely estimate the release timing of traffic restriction. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

【００２７】
一方、円弧すべり法による安全率の算出は、ＣＯＳＴＡＮＡ（製品名：富士通ＦＩＰ社製）を用いて行われる。その基礎式を数式２に示す。
【数２】

【００２８】
ただし、通常のＣＯＳＴＡＮＡでは、不飽和帯の質量変化が考慮されていないため、不飽和領域の体積含水率分布に応じた土壌の重量変化を考慮し改良したものが使用されている。
【００２９】
また、不飽和領域の浸透特性をあらわす透水係数と体積含水率との関係及びせん断抵抗角と体積含水率との関係については、これまで種々の経験式が提案されているが、この管理支援システムにおける解析では、透水係数と体積含水率との関係としてＩｒｍａｙの式、せん断抵抗角と体積含水率との関係としてＶａｎＧｅｎｕｃｈｔｅｎの式が採用されている。これらの関係式を数式３に示す。
【数３】

【００３０】
数式３における形状関数には、一般的な値として提案されている表１に示す値の中間値を用いている。
【表１】

【００３１】
また、この管理支援システムでは、切土のり面を降雨による崩壊の危険度に応じて区分し、危険度が所定値以上となる切土のり面に雨量計を設置し、該雨量計の計測値を該降水量として使用すると共に、該計測値を使用して降雨予測データを補正している。
こうすると、切土のり面の実況安全率（現時点での安全率）の算出においては、その基となる降雨量が管理する切土のり面での現実の値となるため、気象協会から提供される降雨データを使用する場合と比較し、算出精度を向上させることができる。また、切土のり面の予測安全率（これからの推移予測値）の算出においては、その基となる降雨予測データを管理する切土のり面の実状を考慮したものにできるので、気象協会から提供される降雨予測データをそのまま使用する場合と比較し、算出精度を向上させることができる。更に、危険度の高い切土のり面のみに適用することで、システム全体に不必要な負荷がかかることを防止できる。
【００３２】
更に、危険度が所定値以上となる切土のり面には、ＡＤＲ土壌水分計、間隙水圧計及び地下水位計を設置し、該断面２次飽和−不飽和浸透流解析に使用するのり面モデルを随時補正している。
こうすると、解析に使用するのり面モデルの精度を高めることができる。また、危険度の高い切土のり面のみに適用するため、システム全体に不必要な負荷がかかることを防止できる。
【００３３】
次に、この管理支援システムで行われる処理を、図２を参照しながら説明する。
まず、管理対象となる切土のり面の危険度を処理Ｓ１において判定する。そして、判定危険度が所定値以上であれば、実測斜面モデルによる管理を行うこととし、それ以外は単元化斜面モデルによる管理を行うこととする。
【００３４】
実測斜面モデルとは、上記断面２次飽和−不飽和浸透流解析に使用されるのり面モデルであって、その切土のり面現場に設置されたＡＤＲ土壌水分計、間隙水圧計及び地下水位計の実測値により随時補正されるものをいう。そして、このモデルを使用した管理においては、処理Ｓ１０において得られたＡＤＲ土壌水分計、間隙水圧計及び地下水位計の実測値をのり面モデルに入力し、処理Ｓ１１で実測斜面のモデル化を行う。また、実測値は、現場の監視用としても使用される。そして、処理Ｓ１２で飽和度変化の判定がなされ、急激な変化が無い場合には、そのままモデルの補正が繰り返される。そして、急激な変化があった場合に、次の処理Ｓ１５に進み浸透流解析及び安定性解析が行われる。この際、解析に必要な降雨量データとして、気象協会から提供されている実況降雨データ及び超短時間降雨予測情報データの取り込みが開始され（処理Ｓ１３、Ｓ１４）、以降解析を行う場合には必要に応じて参照されることになる。現地降雨データは、上記処理Ｓ１０においてその他の実測値とともに取り込みが開始され、以降同様に解析の際参照されることになる。なお、ここにいう浸透流解析は上記ＡＦＩＭＥＸを使用した解析をさし、また安定性解析は上記ＣＯＳＴＡＮＡの改良型を使用した解析をさすものとし、以後も同様に表現するものとする。
【００３５】
一方、単元化斜面モデルとは、典型的な斜面崩壊パターンを整理し、単純化した斜面モデルのことである。降雨条件による斜面安定性を定量化するための解析では、斜面長、斜面層厚、斜面角度、斜面土層（透水性）、集水面積及びのり面保護工パターンの６つをパラメータとし、更に斜面の安定性を損なわせた既往降雨パターンを入力し、２次元の単元化斜面における水分状況（飽和度分布）を求める浸透解析を行う。そして、この飽和度分布を安定性解析の入力条件とする。このモデルを使用した管理においては、処理Ｓ２１で現地斜面の単元化を行った後、特別な判定を行うことなく処理Ｓ２５の浸透流解析及び安定性解析が行われることになる。この際、解析に必要な降雨量として、気象協会から提供されている実況降雨データ及び超短時間降雨予測情報データの取り込みが開始され、（処理Ｓ２３、Ｓ２４）以降解析を行う場合には必要に応じて参照されることになる。
【００３６】
浸透流解析及び安定性解析（処理Ｓ１５又はＳ２５）以降の処理は、どちらのモデルを使用した場合の管理においてもほぼ同じあるため、以後両管理に共通する内容として説明する。
【００３７】
処理Ｓ１５又はＳ２５の安定解析により、その時点での切土のり面の安全率Ｑの経時変化を得ることができたら、その結果に基づいて切土のり面の安定性評価を行う。（処理Ｓ１６又はＳ２６）得られた切土のり面の安全率Ｑが低下傾向を示すかどうかを把握し、低下する場合には、規定の降雨基準値を照査しながら危険であると評価する。そして、危険であると評価された場合は通行規制を行う。（判断Ｄ１）一方、切土のり面の安全率Ｑが低下傾向を示さない場合は、安全であると判断し、危険であると評価されるまで解析を繰り返す。
【００３８】
通行規制を行ったら、再び同様の解析を行う。（処理Ｓ１７又はＳ２７）そして、処理Ｓ１７又はＳ２７の安定解析により、切土のり面の安全率Ｑの経時変化を得ることができたら、その結果に基づいて斜面安定性評価を行う。（処理Ｓ１８又はＳ２８）切土のり面の安全率Ｑが回復傾向を示す時期（切土のり面の安全率Ｑの変曲点Ｐ）を把握し、変曲点Ｐに達しておらず危険な状態が続くと判断された場合には同様の解析を繰り返す。一方、変曲点Ｐを過ぎその切土のり面の安全率Ｑが回復に向かい、安全と判断された場合には通行規制解除時期の決定を行い（判断Ｄ２）全ての処理が終了する。
【００３９】
処理Ｓ１における危険度の判定には、切土のり面崩壊危険度判定システムが使用されている。図３は、同判定システムのブロック図である。
【００４０】
この切土のり面崩壊危険度判定システムは、道路建設前の地形を確認して原地形としての集水地形を考慮して切土のり面の危険度を判定している。
【００４１】
なお、この判定システムは、基本判定手法としてニューラルネットワークモデルを使用した手法が採用されている。そして、データ１１を入力するための入力層１２と、データ１１を処理する第１ニューロン群１３で構成される中間層１４と、中間層１４から引き渡された処理済値を更に処理する第２ニューロン群１５で構成される出力層１６とからなっている。
【００４２】
入力層１２から入力されるデータ１１は、日本道路公団において平成８年に実施された道路防災総点検における安定度調査表の要因の各項目（地形、土質・地質・構造、表層の状況、形状、変状）の評点区分及びその他の追加素因からなっている。追加素因として、切土のり面上方の状況（のり面上方の土地利用、のり面上方の地形）、地質（地質年代等）及びその他形状素因（のり面延長、のり面の全直高、のり面の形）が入力されるようになっている。そして、道路建設前の地形を確認して原地形としての集水地形を考慮して切土のり面の危険度を判定するようになっている。
【００４３】
この判定システムによれば、従来の切土のり面管理において考慮されていなかった原地形としての集水地形を考慮することにより、危険度の判定精度を向上させることができる。
【００４４】
中間層を構成する第１ニューロン群１３の各ニューロンでは、データ１１の各項目要素に結合係数Ｗｉを乗じて重み付けを行い、これらを足し合わせた後しきい値ｂｉを引き去り、更にそこで得られた値をシグモイド関数に通す処理が行われる。なお、第１ニューロン群１３の数は２０となっている。
【００４５】
出力層１６において出力される危険度１７は、限界降雨量ランクとして表現されるようになっている。また、限界降雨量ランクは、限界降雨量が１００ｍｍ以下となるランクを最も危険度の高いランクとし、危険度の低くなる方向へ限界降雨量が１００ｍｍ刻みで増加するよう８つに区分けされている。そして、最も危険度の低いランクにおける限界降雨量は７０１ｍｍ以上となっている。
こうすると、切土のり面の危険度１７が定量的に表現されるので、厳密な判断を行うことができる。また、実際の管理に使用されている降雨基準値を危険の度合いの指標としたことで、実際の管理に即導入することが可能となる。特に、上記一連の処理はノートパソコン程度のコンピュータで処理可能であることから、従来の研究レベルの安定性判定手法と異なり、実際の管理に即導入可能であることを想定した動作環境を実現することが可能となる。
【００４６】
なお、保護工の定性的評価結果から、のり面にコンクリート吹付けやのり枠工が施工されている場合、耐雨効果が１００ｍｍ以上期待できることがわかったので、その場合は限界降雨量ランクを１ランク上位に設定することとしている。例えば、植生主体の場合に最大経験降雨量が３６５ｍｍであれば限界降雨量ランクは４になるところ、保護工がある場合は最大経験降雨量が３６５ｍｍであれば限界降雨量ランクは５になる。
【００４７】
この判定システムにより判定される危険度の妥当性を検証するため、実データによる学習と判別を実施した。実データとして、日本道路公団八王子管理事務所と大月管理事務所管内の全切土のり面データ（のり面数：２１６）を使用した。
【００４８】
検証を行うにあたり、まず使用するデータを、崩壊履歴のあるもの（崩壊履歴群）と未崩壊のもの（未崩壊群）とに分類する。更に、各群のデータを地質と限界降雨量ランク区分に分類した後、各群のデータを２つの組みに分けた。地質毎と限界降雨量ランク区分毎に分類した理由は、（１）地質によって切土のり面の特徴が異なることが考えられるため、地質の偏りを無くすことと、（２）限界降雨量ランク１〜８を有する切土のり面の特徴を偏り無くシステムに学習させるためである。
【００４９】
次に、上記２つの組みのうち、どちらか一方を学習用データとし、この切土のり面崩壊危険度判定システムに記憶させた。そして、他方の組みに属する切土のり面を判定対象とし、そのデータを判定用とし、各切土のり面の危険度について学習用データを参照しながらその判定を行った。その判定結果を図４に示す。図４はこの判定システムによって判定された各切土のり面の限界降雨量と実際の限界降雨量との差（ランク差）の頻度分布である。たとえば、限界降雨量ランク２である切土のり面がこの判定システムによる判定で２となった場合はランク差０であり、両者が一致していることを示す。したがって、ランク差０の頻度が大きいほど、同判定システムの判別能力が優れていることになる。ここでは、未崩壊のり面の限界降雨量ランクは経験降雨で近似されている値なので、ランク差が１まで許容範囲（判別が一致）と考える。ランク差１までの累積頻度から的中率（判別が一致した数／データの総数）を求めると、学習データで１００％、判別データで平均８４％となった。
【００５０】
Ｓ１０の現地観測に使用される、ＡＤＲ土壌水分計及び間隙水圧計は、本発明にかかる土中水分状況計測方法に適するように設置されている。すなわち、ＡＤＲ土壌水分計の計測地点における設置深度と、間隙水圧計の計測地点における設置深度が標準化されており、切土のり面における降雨の表層からの浸透状況を経時的に把握することができるようになっている。
【００５１】
この計測方法によれば、従来の方法と比べ、メンテナンスが容易となり、また測定を容易かつ迅速に行うことができ、しかも十分に高い計測精度を得ることができる。
【００５２】
図５に示すように、ＡＤＲ土壌水分計は計測地点における土中の設置位置Ａ、Ｂ及びＣに３個設置され、その設置深度は２０ｃｍ、４０ｃｍ及び８０ｃｍとされている。一方、間隙水圧計は土中の設置位置Ｄに設置され、その設置深度は１ｍとされている。
こうすると、実際に土中水分状況を的確に計測を行うことができる。
【００５３】
この計測方法により観測を行った結果を、図６及び図７に示す。この観測により、切土のり面の水分状態をリアルタイムでモニタリングできることが確認された。
【００５４】
また、この計測方法の確認に加え、以下のことが判明した。
１）土質の違いによって、同じ降雨でも飽和度の変動パターンに違いがある。２）同じ土質でも、切土のり面の植生の繁茂状態によって飽和度の変動パターンに違いがある。（図８参照）すなわち、植生が繁茂した斜面を中心に降雨時にのみ飽和度が急激に上昇する現象が確認され、これは植生の根茎等が土の構造に影響を与えてマクロポーラス的な間隙が発生していることによる。
３）降雨の浸透現象に関しては、開放型のり枠工斜面と自然植生斜面とを同等に扱うことができる。
４）１０分間隔の計測を行うことで、雨の振り方によっては地表から切土のり面内部への浸透速度を把握できる。本発明にかかる切土のり面管理支援システムは、切土のり面の不安定化の判定よりもむしろ降雨停止後の切土のり面の安定側への推移を把握することを主眼としているが、不安定化判定にも寄与できる可能性を示している。
５）降雨停止後の飽和度の低下傾向は、砂質度で明瞭であるが粘性土では不明瞭（緩やか）である。しかしながら、間隙水圧計の観測データはいずれの土質においても降雨の停止に伴って明瞭に低下することが明らかとなった。（図７参照）すなわち、降雨停止後の飽和度低下が不明瞭（緩やか）な粘性土からなる切土のり面においては、ＡＤＲ土壌水分計と間隙水圧計を併用することが、降雨停止後の切土のり面の安定側への推移を把握する上で有効である。
【００５５】
【発明の効果】
本発明にかかる切土のり面管理支援システムによれば、切土のり面の安全率を絶対的な数値として得ることなしに、斜面の安全性を予測して交通規制の時期、特に解除時期を決定することができる。
【００５６】
請求項２によれば、既存の解析手法を利用して、安全率を求めることができる。
【００５７】
請求項３によれば、切土のり面の実況安全率（現時点での安全率）の算出においては、その基となる降雨量が管理する切土のり面での現実の値となるため、気象協会から提供される降雨データを使用する場合と比較し、算出精度を向上させることができる。また、切土のり面の予測安全率（これからの推移予測値）の算出においては、その基となる降雨予測データを管理する切土のり面の実状を考慮したものにできるので、気象協会から提供される降雨予測データをそのまま使用する場合と比較し、算出精度を向上させることができる。更に、危険度の高い切土のり面のみに適用することで、システム全体に不必要な負荷がかかることを防止できる。
【００５８】
請求項４によれば、解析に使用するのり面モデルの精度を高めることができ、また危険度の高い切土のり面のみに適用するため、システム全体に不必要な負荷がかかることを防止できる。
【００５９】
請求項５による本発明にかかる切土のり面崩壊危険度判定システムによれば、従来の切土のり面管理において考慮されていなかった原地形としての集水地形を考慮することにより、危険度の判定精度を向上させることができる。そして、その判別率はかなり高いことが確認された。
【００６０】
請求項６によれば、切土のり面の危険度が定量的に表現されるので、厳密な判断を行うことができる。また、実際の管理に使用されている降雨基準値を危険の度合いの指標としたことで、実際の管理に即導入することが可能となる。
【００６１】
請求項７による本発明にかかる土中水分状況計測方法によれば、従来の方法と比べ、メンテナンスが容易となり、また測定を容易かつ迅速に行うことができ、しかも十分に高い計測精度を得ることができる。
【００６２】
請求項８によれば、実際に土中水分状況を的確に計測を行うことができる。また、実際の観測により、切土のり面の水分状態をリアルタイムでモニタリングできることが確認され。更に、この計測方法によれば、実際の観測により、土質や植生の繁茂状態が飽和度に影響を及ぼすこと、降雨の浸透現象に関しては開放型のり枠工斜面と自然植生斜面とを同等に扱うことが可能であること、及び粘性土からなる切土のり面においてはＡＤＲ土壌水分計と間隙水圧計との併用が有効であること等が判明した。更にまた、この計測方法は、１０分間隔（リアルタイム）の計測を行うことで、切土のり面の不安定化判定はいうまでもなく、降雨停止後の切土のり面の安定性評価にも用いることができる。
【図面の簡単な説明】
【図１】時間経過を横軸として、降水量及び切土のり面の安全率の経時変化の関係を示すグラフである。
【図２】本発明にかかる切土のり面管理支援システムの具体例を示すフローチャート図である。
【図３】本発明にかかる切土のり面崩壊危険度判定システムの具体例を示すブロック図である。
【図４】同判定システムによって判定された各切土のり面の限界降雨量と実際の限界降雨量との差（ランク差）の頻度分布である。
【図５】本発明にかかる土中水分状況計測方法に適した、ＡＤＲ土壌水分計及び間隙水圧計の設置状態を示す図である。
【図６】同計測方法を使用することにより得られた、降雨による飽和度の深度別変化の傾向を示す図である。
【図７】同計測方法を使用することにより得られた、粘性土地盤における降雨停止後の飽和度と間隙水圧の変化傾向を示す図である。
【図８】同計測方法を使用することにより得られた、切土のり面植生の繁茂状態の違いによる飽和度変動パターンの違いを示す図である。
【符号の説明】
Ｑ 切土のり面の安全率
Ｒ 降雨量[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a system for supporting timing determination of road traffic regulation for preventing a landslide disaster or the like during abnormal weather.
[0002]
[Prior art]
The biggest issue of road traffic regulation to prevent landslide disasters during abnormal weather is to avoid overlooked disasters as much as possible to ensure the safety of road users and to maximize the function of roads. In other words, how to adjust the contact point of two contradictory objectives, that is, to reduce the amount of lost traffic. In order to solve this problem, road managers are reviewing the regulation methods and regulation standard values in consideration of various local conditions and rainfall indicators.Each regulation method is based on past disaster history analysis. It is a method of managing with a certain reference value set based on this.
[0003]
[Problems to be solved by the invention]
However, in Japan, where the geographical and geological conditions are complicated, the geographical and geological conditions are diversified even when only looking at the range of a certain traffic restriction section. Therefore, when analyzing disaster histories on a section-by-section basis, in many cases, the causal relationship between rainfall and the occurrence of collapse had to be unclear. That is, the correlation between the rain index and the occurrence of collapse is not always one-to-one, and it has been difficult to determine the timing of traffic regulation.
[0004]
In addition, many institutions have been conducting research on elucidating the mechanism of surface landslides on slopes caused by rainfall and on predicting the occurrence of landslides. Is still a difficult task to grasp. Therefore, it is almost impossible at this time to completely predict the occurrence of collapse.
[0005]
In traffic regulation, it is necessary to coordinate the prevention of overlooked disasters and the reduction of unscheduled traffic. It is necessary to start traffic regulation. Therefore, how to determine the time to release the traffic regulation is an actual problem.
[0006]
Therefore, the present invention provides a cut slope management support system for supporting the determination of the timing of traffic regulation, particularly the determination of the release timing, a cut slope failure risk determining system used in the cut slope management system, and measurement of soil moisture status. The aim is to provide a method.
[0007]
[Means for Solving the Problems]
The cut slope management support system according to the present invention is characterized in that the safety factor of the cut slope is relatively changed under the influence of precipitation.
[0008]
According to this management support system, since the change in the relative safety factor of the cut slope is used, the safety of the slope can be reduced without obtaining the absolute value of the safety factor of the cut slope. By predicting, it is possible to determine the timing of traffic regulation, particularly the release timing. This is due to the fact that the stability of the slope has the property of recovering after the rainfall has decreased or stopped. That is, since the safety factor of the cut slope shows a recovery tendency due to the decrease or stop of the rainfall, by grasping the time when the recovery trend shows (the inflection point of the safety factor of the cut slope), the traffic regulation of the traffic The release time can be accurately predicted.
[0009]
The present invention is intended to support the management of a cut slope having complicated geological conditions and the like, but can be naturally applied to the management support of an embankment slope having simpler conditions. Therefore, in the present invention, even if it is expressed as a cut slope, it means that it can be particularly applied to the cut slope, and it is not intended to exclude the embankment slope from the object. The embankment slope is naturally included. The same applies to the following.
[0010]
The safety factor of the cut slope reflects the soil moisture condition and groundwater condition obtained by the cross-sectional secondary saturated-unsaturated seepage flow analysis of the cut slope, and takes into account the change in the water content of the unsaturated zone. It may be obtained by the arc sliding method.
In this case, the safety factor of the cut slope can be obtained by using the existing analysis method.
[0011]
The cut slope is classified according to the risk of collapse due to rainfall, a rain gauge is installed on the cut slope where the risk is equal to or greater than a predetermined value, and the measured value of the rain gauge is defined as the rainfall. At the same time, the rainfall prediction data may be corrected using the measured value.
In this case, in calculating the actual safety factor (current safety factor) of the cut slope, the Meteorological Association will provide it because the rainfall on which it is based is the actual value on the managed cut slope. The calculation accuracy can be improved as compared with the case where rainfall data is used. In addition, in calculating the predicted safety factor of the cut slope (predicted transition value from now on), it is possible to take into account the actual condition of the cut slope that manages the rainfall forecast data on which it is based. The calculation accuracy can be improved as compared with the case where the rainfall prediction data is used as it is. Further, by applying only to the cut slope having a high risk, unnecessary load can be prevented from being applied to the entire system.
[0012]
An ADR soil moisture meter, a pore water pressure gauge and a groundwater level gauge are installed on the cut slope where the degree of risk is equal to or more than a predetermined value, and a slope model used for the secondary saturated-unsaturated seepage flow analysis is used. The correction may be made at any time.
In this case, the accuracy of the slope model used for the analysis can be improved, and since it is applied only to the high-risk cut slope, unnecessary load on the entire system can be prevented. In this method, an updatable model is introduced in the conventional analysis method in which a model with the highest possible accuracy is constructed in the initial stage and the analysis based on the model is continued thereafter.
[0013]
The risk can be determined using the cut slope failure risk determination system according to the present invention.
[0014]
The cut slope failure risk determination system according to the present invention is characterized in that it checks the topography before road construction and determines the risk of the cut slope in consideration of the catchment topography as the original topography. . Note that a method using a neural network model is preferable as the basic determination method.
[0015]
According to the cut slope failure risk assessment system, it is possible to improve the accuracy of the risk assessment by considering the catchment topography as the original topography that was not considered in the conventional cut slope management. it can.
[0016]
The risk may be expressed as a marginal rainfall rank.
In this case, since the degree of danger of the cut slope is quantitatively expressed, strict judgment can be made. Further, by using the rainfall reference value used for the actual management as an index of the degree of danger, it becomes possible to immediately introduce the rainfall reference value to the actual management.
[0017]
It is preferable that the ADR soil moisture meter and the pore water pressure gauge are arranged so as to be suitable for the soil moisture status measuring method according to the present invention.
[0018]
The method for measuring the moisture content in soil according to the present invention standardizes the installation depth at the measurement point of the ADR soil moisture meter and the installation depth of the pore water pressure gauge at the measurement point, and infiltrates rainfall on the cut slope from the surface layer. It is characterized by grasping the situation over time.
[0019]
According to this measurement method, maintenance is easy, and the measurement can be performed easily and quickly, and sufficiently, compared with conventional methods such as a soil extraction / furnace drying method, a method using a neutron moisture meter, and a tensiometer method. High measurement accuracy can be obtained. In addition, in the soil extraction and furnace drying method, there was a problem that continuous monitoring was not possible although it had high accuracy. In addition, the neutron moisture meter had a problem in handling the neutron source. Furthermore, the tensiometer method has a problem in long-term monitoring in situ, such as a problem of hysteresis and complicated maintenance.
[0020]
The three ADR soil moisture meters are installed at the measurement point, the installation depth of the ADR soil moisture meter is 20 cm, 40 cm and 80 cm, and the installation depth of the pore water pressure gauge is preferably 1 m. In addition, the soil moisture status can be accurately measured.
[0021]
DETAILED DESCRIPTION OF THE INVENTION
A specific example of the cut slope management support system according to the present invention will be described with reference to FIGS.
[0022]
FIG. 2 is a flowchart showing a specific example of the cut slope management support system according to the present invention. The purpose of this management support system is to determine the timing of traffic regulation, that is, to determine the traffic regulation start timing (decision D1) and the traffic regulation release timing (decision D2). These determinations D1 and D2 are obtained as a result of the stability evaluation of the cut slope in the processing S16, S18 or S26, S28. In the evaluation, the safety factor Q of the cut slope is determined by the influence of the precipitation R. It uses the fact that it changes relatively in response to it. FIG. 1 shows a specific example of a temporal change of the safety factor Q of the cut slope.
[0023]
FIG. 1 is a graph showing the relationship between the amount of precipitation R and the change over time in the safety factor Q of the cut slope, with time elapsed on the horizontal axis. The safety factor Q of the cut slope is based on the left vertical axis, and the precipitation R is based on the right vertical axis. As for the safety factor Q of the cut slope, the value calculated based on the data at a specific time is represented by white circles, and these white circles are arranged in chronological order to show a temporal change. Further, the precipitation R shows a temporal change by a bar graph in which the precipitation within a predetermined time is arranged in time series.
[0024]
According to this management support system, since the relative change in the safety factor Q of the cut slope is used, the safety factor Q of the cut slope cannot be obtained as an absolute value, and the safety of the slope can be reduced. The timing of traffic regulation, in particular, the timing of release can be determined by predicting the nature of traffic. This is due to the fact that the stability of the slope has the property of recovering after the rainfall has decreased or stopped. That is, since the safety factor Q of the cut slope shows a recovery tendency due to the decrease or stop of the rainfall, by grasping the time when the recovery trend shows (the inflection point P of the safety factor Q of the cut slope), It is possible to accurately predict the timing of releasing traffic regulations. More specifically, referring to FIG. 1, the safety factor Q of the cut slope after the inflection point P does not become lower than the value at the inflection point P. If that is the case, it means that traffic restrictions can be lifted. It is necessary to start traffic regulation at least at the time before the inflection point P, where the safety factor Q of the cut slope shows a decreasing tendency. become.
[0025]
The safety factor Q of the cut slope reflects the soil moisture and groundwater conditions obtained by the cross-sectional secondary saturated-unsaturated seepage flow analysis of the cut slope, and takes into account the change in the water content of the unsaturated zone. It is determined by the arc sliding method.
In this case, the safety factor can be obtained by using the existing analysis method.
[0026]
In this support management system, the cross-sectional secondary saturated-unsaturated seepage flow analysis is performed by using AIMEX (product name: Fujitsu FIP). Formula 1 shows the basic formula.
(Equation 1)

[0027]
On the other hand, the calculation of the safety factor by the arc sliding method is performed using COSTANA (product name: manufactured by Fujitsu FIP). Equation 2 shows the basic formula.
(Equation 2)

[0028]
However, since ordinary COSTANA does not consider the change in mass of the unsaturated zone, an improved COSTANA is used in consideration of the change in soil weight according to the volumetric water content distribution in the unsaturated region.
[0029]
In addition, various empirical formulas have been proposed for the relationship between the permeability and the volume moisture content, which represent the permeation characteristics of the unsaturated region, and the relationship between the shear resistance angle and the volume moisture content. In the analysis in, the Irmay formula is used as the relationship between the hydraulic conductivity and the volume water content, and the VanGenuchten formula is used as the relationship between the shear resistance angle and the volume water content. Equation 3 shows these relational expressions.
[Equation 3]

[0030]
As the shape function in Expression 3, an intermediate value between the values shown in Table 1 that are proposed as general values is used.
[Table 1]

[0031]
Further, in this management support system, the cut slope is classified according to the risk of collapse due to rainfall, a rain gauge is installed on the cut slope where the risk is equal to or more than a predetermined value, and the measured value of the rain gauge is measured. Is used as the precipitation amount, and the rainfall prediction data is corrected using the measurement value.
In this way, in calculating the actual safety factor (current safety factor) of the cut slope, the rainfall on which it is based is the actual value on the managed cut slope, and is provided by the Meteorological Association. The calculation accuracy can be improved as compared with the case where rainfall data is used. In addition, in calculating the predicted safety factor of the cut slope (predicted transition value from now on), it is possible to take into account the actual condition of the cut slope that manages the rainfall forecast data on which it is based. The calculation accuracy can be improved as compared with the case where the rainfall prediction data is used as it is. Further, by applying only to the cut slope having a high risk, unnecessary load can be prevented from being applied to the entire system.
[0032]
Further, an ADR soil moisture meter, a pore water pressure gauge and a groundwater level gauge are installed on the cut slope where the degree of risk is equal to or more than a predetermined value, and a slope model used for the secondary saturated-unsaturated seepage flow analysis of the section. Is corrected from time to time.
In this case, the accuracy of the slope model used for the analysis can be improved. In addition, since the method is applied only to the cut slope having a high risk, it is possible to prevent unnecessary load from being applied to the entire system.
[0033]
Next, processing performed by the management support system will be described with reference to FIG.
First, the risk of the cut slope to be managed is determined in step S1. If the determination risk is equal to or more than the predetermined value, the management is performed using the actually measured slope model, and otherwise, the management is performed using the unitized slope model.
[0034]
The measured slope model is a slope model used for the above-mentioned secondary saturated-unsaturated seepage flow analysis, and is an ADR soil moisture meter, a pore water pressure gauge, and a groundwater level gauge installed at the cut slope. Is corrected at any time by the actual measurement value. In the management using this model, the measured values of the ADR soil moisture meter, the pore water pressure gauge and the groundwater level gauge obtained in the processing S10 are input to the slope model, and the actually measured slope is modeled in the processing S11. . The measured values are also used for on-site monitoring. Then, in step S12, a change in the degree of saturation is determined, and if there is no rapid change, the correction of the model is repeated as it is. Then, when there is a sudden change, the process proceeds to the next step S15, where the permeation flow analysis and the stability analysis are performed. At this time, as the rainfall data necessary for the analysis, the actual rainfall data and the ultra-short rainfall prediction information data provided by the Meteorological Association are taken in (processes S13 and S14), and are required for the subsequent analysis. Will be referenced accordingly. The local rainfall data is started to be imported together with other actually measured values in the above-described process S10, and will be similarly referred to at the time of analysis. The permeation flow analysis referred to here refers to the analysis using the above-mentioned AIMEX, and the stability analysis refers to the analysis using the improved version of the above-described COSTANA, and will be expressed in the same manner hereinafter.
[0035]
On the other hand, the unitized slope model is a simplified slope model in which typical slope failure patterns are arranged. In the analysis for quantifying slope stability due to rainfall conditions, the following parameters were used: slope length, slope layer thickness, slope angle, slope soil layer (water permeability), catchment area, and slope protection pattern. A permeation analysis is performed to input a past rainfall pattern that impairs the stability of the slope, and to determine the moisture status (saturation distribution) on the two-dimensional unitized slope. Then, this saturation distribution is used as an input condition for stability analysis. In the management using this model, the unity of the on-site slope is performed in the processing S21, and then the seepage flow analysis and the stability analysis in the processing S25 are performed without performing any special determination. At this time, as the rainfall required for the analysis, the actual rainfall data and the ultra-short-time rainfall prediction information data provided by the Meteorological Association are taken in. When the analysis is performed after (processing S23, S24), it becomes necessary. Will be referenced accordingly.
[0036]
Since the processes after the permeation flow analysis and the stability analysis (process S15 or S25) are almost the same in the management using either model, the following description will be made as the content common to both the managements.
[0037]
If it is possible to obtain a temporal change of the safety factor Q of the cut slope at that time by the stability analysis of the processing S15 or S25, the stability evaluation of the cut slope is performed based on the result. (Processing S16 or S26) It is grasped whether the obtained safety factor Q of the cut slope shows a tendency to decrease, and when it falls, it is evaluated as dangerous while checking a prescribed rainfall reference value. If it is judged to be dangerous, traffic regulation is performed. (Determination D1) On the other hand, if the safety factor Q of the cut slope does not show a decreasing tendency, it is determined to be safe and the analysis is repeated until it is evaluated as dangerous.
[0038]
After restricting traffic, the same analysis is performed again. (Processing S17 or S27) When the stability analysis of the processing S17 or S27 can obtain the temporal change of the safety factor Q of the cut slope, the slope stability is evaluated based on the result. (Processing S18 or S28) The time when the safety factor Q of the cut slope shows a tendency to recover (the inflection point P of the safety factor Q of the cut slope) is grasped, and it is dangerous that the inflection point P is not reached. When it is determined that the state continues, the same analysis is repeated. On the other hand, after passing the inflection point P, the safety factor Q of the cut slope goes toward recovery, and if it is determined that the road is safe, the timing of releasing the traffic regulation is determined (decision D2), and all the processing ends.
[0039]
For the determination of the risk in the process S1, a cut slope failure risk determination system is used. FIG. 3 is a block diagram of the determination system.
[0040]
This cut slope failure risk determination system checks the topography before road construction and determines the risk of the cut slope in consideration of the catchment topography as the original topography.
[0041]
In this determination system, a method using a neural network model is adopted as a basic determination method. Then, an input layer 12 for inputting the data 11, an intermediate layer 14 composed of a first neuron group 13 for processing the data 11, and a second neuron for further processing the processed value passed from the intermediate layer 14 And an output layer 16 composed of a group 15.
[0042]
The data 11 input from the input layer 12 is based on the factors (topography, soil / geology / structure, surface condition, shape, etc.) of the factors of the stability survey table in the Road Disaster Prevention Inspection conducted by the Japan Highway Public Corporation in 1996. , Transformation) and other additional factors. Additional factors include conditions above the cut slope (land use above the slope, topography above the slope), geology (geological age, etc.) and other shape factors (extension of the slope, overall height of the slope, slope) Is entered. The terrain before road construction is confirmed, and the degree of danger of the cut slope is determined in consideration of the water-collecting terrain as the original terrain.
[0043]
According to this determination system, the accuracy of determining the degree of risk can be improved by considering the water-collecting landform as the original landform that has not been considered in the conventional cut slope management.
[0044]
In each neuron of the first neuron group 13 constituting the intermediate layer, each item element of the data 11 is weighted by multiplying it by the coupling coefficient Wi, and after adding them, the threshold value bi is subtracted and further obtained therefrom. A process of passing the value through a sigmoid function is performed. The number of the first neuron groups 13 is 20.
[0045]
The risk 17 output from the output layer 16 is expressed as a critical rainfall rank. In addition, the critical rainfall rank is defined as the highest danger rank when the critical rainfall is 100 mm or less, and is divided into eight such that the critical rainfall increases in 100 mm increments in the direction of decreasing the danger. . The marginal rainfall at the lowest risk rank is 701 mm or more.
In this way, the risk 17 of the cut slope is quantitatively expressed, so that a strict judgment can be made. Further, by using the rainfall reference value used for the actual management as an index of the degree of danger, it becomes possible to immediately introduce the rainfall reference value to the actual management. In particular, since the above series of processes can be processed by a computer such as a notebook computer, an operating environment that assumes that it can be immediately introduced into actual management, unlike conventional research-level stability determination methods, is realized. It becomes possible.
[0046]
In addition, from the qualitative evaluation results of the protective work, it was found that when concrete spraying or a slope frame work was applied to the slope, the rain resistance effect could be expected to be 100 mm or more. In that case, the critical rainfall rank was ranked 1 rank. It is set to be higher. For example, in the case of mainly vegetation, the maximum rainfall rank is 4 if the maximum experience rainfall is 365 mm, and the critical rainfall rank is 5 if the maximum experience rainfall is 365 mm when there is a protection work.
[0047]
In order to verify the validity of the risk determined by this determination system, learning and determination using actual data were performed. As actual data, all cut slope data (the number of slopes: 216) in the jurisdiction of the Japan Highway Public Corporation Hachioji management office and the Otsuki management office were used.
[0048]
In performing the verification, data to be used are first classified into those with a collapse history (collapse history group) and those without collapse (non-collapse group). Furthermore, after classifying the data of each group into geological and critical rainfall rank categories, the data of each group was divided into two sets. Reasons for classification by geology and by marginal rainfall rank classification are as follows: (1) It is considered that the characteristics of the cut slope may differ depending on the geology. This is for the purpose of causing the system to learn the characteristics of the cut slope having 8 without bias.
[0049]
Next, one of the above two sets was used as learning data and stored in the cut slope failure risk assessment system. Then, the cut slopes belonging to the other group were set as determination targets, and the data was used for determination, and the determination was performed with reference to the learning data for the risk of each cut slope. FIG. 4 shows the result of the determination. FIG. 4 is a frequency distribution of a difference (rank difference) between the critical rainfall amount of each cut slope and the actual critical rainfall amount determined by the determination system. For example, if the cut slope having the critical rainfall rank 2 is determined to be 2 by the determination system, the rank difference is 0, indicating that the two are the same. Therefore, the higher the frequency of rank difference 0, the better the discriminating ability of the judgment system. Here, since the marginal rainfall rank of the uncollapsed slope is a value approximated by empirical rainfall, it is considered that the rank difference is an allowable range up to 1 (identification is consistent). When the hit rate (the number of matched discriminations / the total number of data) was calculated from the cumulative frequency up to the rank difference 1, the learning data was 100% and the discrimination data was 84% on average.
[0050]
The ADR soil moisture meter and the pore water pressure gauge used for the on-site observation in S10 are installed so as to be suitable for the soil moisture condition measuring method according to the present invention. That is, the installation depth at the measurement point of the ADR soil moisture meter and the installation depth at the measurement point of the pore water pressure gauge are standardized, and the permeation state of rainfall from the surface layer on the cut slope can be grasped over time. It has become.
[0051]
According to this measuring method, maintenance becomes easier, and measurement can be performed easily and quickly, and sufficiently high measuring accuracy can be obtained, as compared with the conventional method.
[0052]
As shown in FIG. 5, three ADR soil moisture meters are installed at installation positions A, B, and C in the soil at the measurement points, and the installation depths thereof are 20, 40, and 80 cm. On the other hand, the pore pressure gauge is installed at an installation position D in the soil, and its installation depth is 1 m.
In this case, the soil moisture status can be actually measured accurately.
[0053]
FIGS. 6 and 7 show the results of observation by this measurement method. This observation confirmed that the water condition of the cut slope could be monitored in real time.
[0054]
In addition to confirming this measurement method, the following was found.
1) There is a difference in the variation pattern of the degree of saturation even in the same rainfall due to the difference in soil properties. 2) Even with the same soil type, the variation pattern of the saturation varies depending on the vegetation overgrowth on the cut slope. (See FIG. 8) That is, a phenomenon was observed in which the degree of saturation increased sharply only during rainfall, mainly on the slopes where vegetation was overgrown, and this was because the rhizomes of the vegetation affected the soil structure and caused macroporous gaps. Due to the occurrence of
3) Regarding rainfall infiltration phenomena, open slopes and natural vegetation slopes can be treated equally.
4) By measuring at intervals of 10 minutes, it is possible to grasp the permeation rate from the ground surface to the inside of the cut slope depending on the manner of rain. The cut slope management support system according to the present invention is mainly aimed at grasping the transition of the cut slope to a stable side after rain stop, rather than determining the instability of the cut slope, This indicates the possibility of contributing to the determination of instability.
5) The tendency of the decrease in saturation after rainfall is stopped is clear in sandiness, but unclear (slow) in cohesive soil. However, it was clarified that the pore pressure gauge data clearly decreased with the stop of rainfall in all soil types. (See FIG. 7) In other words, on a cut slope made of a viscous soil whose saturation degree is unclear (slow) after rain stop, it is difficult to use the ADR soil moisture meter and the pore water pressure gauge together after the rain stop. It is effective for grasping the transition of the cut slope to the stable side.
[0055]
【The invention's effect】
According to the cut slope management support system according to the present invention, without obtaining the safety factor of the cut slope as an absolute value, predicting the safety of the slope, the time of traffic regulation, especially the release time. Can be determined.
[0056]
According to the second aspect, the safety factor can be obtained by using an existing analysis method.
[0057]
According to the third aspect, in the calculation of the actual safety factor (current safety factor) of the cut slope, the rainfall on which it is based is an actual value on the managed cut slope, and the The calculation accuracy can be improved as compared with the case where rainfall data provided by the association is used. In addition, in calculating the predicted safety factor of the cut slope (predicted transition value from now on), it is possible to take into account the actual condition of the cut slope that manages the rainfall forecast data on which it is based. The calculation accuracy can be improved as compared with the case where the rainfall prediction data is used as it is. Further, by applying only to the cut slope having a high risk, unnecessary load can be prevented from being applied to the entire system.
[0058]
According to the fourth aspect, the accuracy of the slope model used for the analysis can be improved, and since it is applied only to the cut slope having a high risk, unnecessary load can be prevented from being applied to the entire system. .
[0059]
According to the cut slope failure risk assessment system of the present invention according to claim 5, by taking into account the catchment topography as the original topography that was not considered in the conventional cut slope management, the risk is reduced. Determination accuracy can be improved. And it was confirmed that the discrimination rate was considerably high.
[0060]
According to the sixth aspect, the degree of danger of the cut slope is quantitatively expressed, so that a strict judgment can be made. Further, by using the rainfall reference value used for the actual management as an index of the degree of danger, it becomes possible to immediately introduce the rainfall reference value to the actual management.
[0061]
According to the method for measuring the moisture content in soil according to the present invention according to claim 7, maintenance is easy, and the measurement can be performed easily and quickly, and sufficiently high measurement accuracy can be obtained as compared with the conventional method. Can be.
[0062]
According to the eighth aspect, it is possible to accurately measure the soil moisture status actually. In addition, actual observations confirmed that the water condition on the cut slope could be monitored in real time. Furthermore, according to this measurement method, the actual observation shows that the soil condition and vegetation overgrowth affect the degree of saturation, and regarding the infiltration phenomenon of rainfall, open sloped slopes and natural vegetation slopes are treated equally. It was found that the combination of an ADR soil moisture meter and a pore pressure gauge was effective on a cut slope made of clayey soil. Furthermore, this measurement method performs measurement at intervals of 10 minutes (real time) to determine the instability of the cut slope and to evaluate the stability of the cut slope after rain stoppage. Can be used.
[Brief description of the drawings]
FIG. 1 is a graph showing the relationship between the precipitation and the change over time in the safety factor of a cut slope, with time elapsed as the horizontal axis.
FIG. 2 is a flowchart illustrating a specific example of a cut slope management support system according to the present invention.
FIG. 3 is a block diagram showing a specific example of a cut slope failure risk determining system according to the present invention.
FIG. 4 is a frequency distribution of a difference (rank difference) between the critical rainfall amount of each cut slope and the actual critical rainfall amount determined by the determination system.
FIG. 5 is a diagram showing an installation state of an ADR soil moisture meter and a pore water pressure gauge suitable for the soil moisture status measuring method according to the present invention.
FIG. 6 is a diagram showing a tendency of a depth-dependent change in the degree of saturation due to rainfall obtained by using the same measurement method.
FIG. 7 is a diagram showing a change tendency of a saturation degree and a pore water pressure after stopping rainfall in a viscous ground obtained by using the same measurement method.
FIG. 8 is a diagram showing a difference in a saturation variation pattern due to a difference in the vegetation state of a cut slope obtained by using the same measurement method.
[Explanation of symbols]
Q Safety factor of cut slope
R rainfall

Claims (8)

A cut slope management support system utilizing the fact that the safety factor (Q) of the cut slope relatively changes under the influence of the precipitation (R). The safety factor (Q) of the cut slope reflects the soil moisture condition and the groundwater condition obtained by the cross-sectional secondary saturated-unsaturated seepage flow analysis of the cut slope, and changes in the water content of the unsaturated zone. The cut slope management support system according to claim 1, wherein the cut slope management support system is obtained by an arc sliding method in consideration of: The cut slope is classified according to the risk of collapse due to rainfall, a rain gauge is installed on the cut slope where the risk is equal to or greater than a predetermined value, and the measured value of the rain gauge is defined as the rainfall. The cut slope management support system according to claim 1, wherein the rainfall prediction data is corrected using the measured value while being used. An ADR (Amplitude-Domain Refractometry) soil moisture meter, a pore water pressure gauge, and a groundwater level gauge are installed on the cut slope where the risk is equal to or higher than a predetermined value, and the cross section secondary saturated-unsaturated flow analysis is performed. The cut slope management support system according to claim 3, wherein a slope model to be used is corrected as needed. A cut slope failure risk determination system characterized by confirming a topography before road construction and determining a cut slope risk in consideration of a catchment topography as an original topography. The cut slope failure risk determining system according to claim 5, wherein the risk is expressed as a critical rainfall rank. The installation depth at the measurement point of the ADR soil moisture meter and the installation depth of the pore pressure gauge at the measurement point are standardized, and the permeation state of rainfall from the surface layer on the cut slope is grasped over time. Soil moisture measurement method. 8. The three ADR soil moisture meters are installed at the measurement point, the installation depth of the ADR soil moisture meter is 20 cm, 40 cm, and 80 cm, and the installation depth of the pore water pressure gauge is 1 m. The method for measuring the moisture content in soil described in the above.

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