JP5898639B2 - Prediction method of ground displacement - Google Patents
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本発明は、斜面地盤において発生する可能性のある地すべり、表層崩壊、がけ崩れ等の土砂災害をもたらすような地盤の変位を予測する地盤変位の予測方法の技術分野に関するものである。 The present invention relates to a technical field of a ground displacement prediction method for predicting ground displacement that may cause a sediment disaster such as landslide, surface layer collapse, and landslide that may occur on slope ground.
一般に、自然災害の一つとして土砂災害があり、このような土砂災害として、傾斜地に発生する地すべり、表層崩壊、がけ崩れ、土石流などによる災害がある。そして、このような傾斜地での土砂災害は、斜面地盤が変状したり移動したりする地盤変位によって引き起される。このような地盤変位を測定する手法については、従来、例えば、地盤変位が発生するとされる場所にボーリング孔を掘り、ここに歪ゲージを備えたパイプを挿入し、地盤変位によって生じた歪量を計測することで地盤変位を測定するようにしたものが知られている（例えば、特許文献１参照。）。また、ボーリング孔に挿入されるケーブルに形状記憶合金からなる導体を内装し、地盤変位が発生した場合に導体にケーブルの変位形状を記憶させておくことで地盤変位の測定をするようにしたものも提唱されている（例えば、特許文献２参照。）。
しかしながら前記従来のものは、実際に斜面崩壊が発生している最中又は発生した後の地盤変位を測定するものであって、地盤変位の発生を予測するものではない。しかるに、地盤変位の発生を予測することは、土砂災害を未然に防止するために重要である。
そこで、本発明の発明者は、地盤変位が発生する惧れのある地区の地下水に含まれるナトリウムイオンやカルシウムイオン等の特定イオンの濃度を経時的に測定し、該イオン濃度が急激に上昇した場合には、これを地すべりや表層崩壊等の斜面崩壊による地盤変位が発生する前兆であるとして予測する方法を発明した（特許文献３参照。）。
このものは、風化の進行等により土粒子が微細化すると、地盤内の応力に変化が生じてすべり面が発生し、このすべり面が成長することによってさらにすべり面近傍の土粒子が微細化していくという現象を捉え、このように微細化した土粒子表面を通過した地下水は、摺動力を受けていない比較的大きな土粒子表面を通過した地下水よりもイオン濃度が高くなることに着目したもので、地下水に含まれるイオン濃度を継続的に測定し、イオン濃度が上昇すれば地下水が通過してきた地盤のどこかにすべり面が発生したとみなし、該すべり面が発生したことによって地盤変位が起こる可能性が高いと予測するものである。
さらに、本発明の発明者は、地盤変位が発生すると予測される地盤から供試体を採取し、該供試体に採取した現場の地下水を通過させ、該通過した地下水の化学組成の変化を観測することで、採取した地盤での地盤変位の時期を予測できることを確認し、この考え方に基づいて地盤変位の予測方法を発明した（特許文献４参照。）。
そして、これらの発明により、地盤変位の発生の予測および発生する時期を予測することができ、地盤管理に大きく貢献している。
In general, there is a landslide disaster as one of the natural disasters, and as such a landslide disaster, there are disasters caused by landslides, surface collapses, landslides, debris flows, etc. that occur on slopes. And the earth and sand disaster in such a sloping ground is caused by the ground displacement which a slope ground deforms or moves. With regard to a technique for measuring such ground displacement, conventionally, for example, a borehole is dug in a place where the ground displacement is generated, a pipe having a strain gauge is inserted therein, and the amount of strain caused by the ground displacement is calculated. What measured the ground displacement by measuring is known (for example, refer to patent documents 1). In addition, a conductor made of a shape memory alloy is built in the cable inserted into the borehole, and when the ground displacement occurs, the displacement shape of the cable is memorized in the conductor and the ground displacement is measured. Has also been proposed (see, for example, Patent Document 2).
However, the conventional one measures the ground displacement during or after the slope failure actually occurs, and does not predict the occurrence of the ground displacement. However, it is important to predict the occurrence of ground displacement in order to prevent landslide disasters.
Therefore, the inventor of the present invention measured the concentration of specific ions such as sodium ions and calcium ions contained in the groundwater in the area where the ground displacement may occur, and the ion concentration increased rapidly. In some cases, we invented a method for predicting this as a precursor to the occurrence of ground displacement due to slope failures such as landslides and surface failure (see Patent Document 3).
In this case, when the soil particles become finer due to the progress of weathering etc., the stress in the ground changes and a slip surface is generated, and the growth of this slip surface further refines the soil particles near the slip surface. In this way, we focused on the fact that the groundwater that passed through the surface of the finely divided soil particles had a higher ion concentration than the groundwater that passed through the relatively large soil particle surface that was not subjected to sliding force. , Continuously measuring the ion concentration in the groundwater, if the ion concentration increases, it is considered that a slip surface has occurred somewhere in the ground through which the groundwater has passed, and the ground displacement occurs due to the occurrence of the slip surface It is predicted that the possibility is high.
Further, the inventor of the present invention collects a specimen from the ground where ground displacement is predicted to occur, passes the groundwater collected on the specimen to the ground, and observes a change in the chemical composition of the groundwater that has passed through. Thus, it was confirmed that the ground displacement time in the collected ground could be predicted, and a ground displacement prediction method was invented based on this concept (see Patent Document 4).
And by these inventions, it is possible to predict the occurrence of ground displacement and the time when it will occur, which greatly contributes to ground management.
しかしながら、前記特許文献３、４のものは、地盤変位の発生の予測や、発生する時期を予測することはできるが、その地盤変位がどの程度の規模であるかは予測することができず、このため、具体的にどの程度の防災対策が必要であるかの判断がなかなか難しいという問題があり、ここに本発明の解決すべき課題がある。 However, although the thing of the said patent documents 3 and 4 can estimate the generation | occurrence | production of a ground displacement and the time to generate | occur | produce, it cannot estimate how much the ground displacement is, For this reason, there is a problem that it is difficult to determine how much disaster prevention measures are necessary, and there is a problem to be solved by the present invention.
本発明は、上記の如き実情に鑑みこれらの課題を解決することを目的として創作されたものであって、請求項１の発明は、観測対象地区の地下水中に存在する特定イオンのイオン濃度と地盤変位量とを継続的に測定し、該測定値に基づいて特定イオンのイオン濃度変化量と地盤変位量との相関関係を予め求め、該相関関係に基づいて特定イオンのイオン濃度変化量から次回に発生する地盤変位の変位量を予測する予測方法であって、前記相関関係は、イオン濃度が所定量以上変化した場合に地盤変位量はイオン濃度変化量の一次関数となることを特徴とする地盤変位の予測方法である。
請求項２の発明は、請求項１において、特定イオンのイオン濃度変化量と地盤変位量との相関関係を求めるにあたり、イオン濃度および地盤変位量の測定開始後に最初にイオン濃度の急上昇が発生したときのイオン濃度変化と、該最初のイオン濃度の急上昇の発生後に最初に発生した地盤変位とを対応させ、以降は発生順に順次イオン濃度変化と地盤変位とを対応させて相関関係を求めたことを特徴とする地盤変位の予測方法である。
請求項３の発明は、請求項１または２において、相関関係を求める場合に用いるイオン濃度変化量は、任意のイオン濃度急上昇を今回のイオン濃度急上昇としたとき、該今回のイオン濃度急上昇の開始を終点とする今回のイオン濃度急上昇以前の一定期間におけるイオン濃度の平均値をベースライン濃度とし、また、前記一定期間内にイオン濃度の急上昇があった場合には、該イオン濃度急上昇の終了を始点とし今回のイオン濃度急上昇の開始を終点とする期間におけるイオン濃度の平均値をベースライン濃度として、該ベースライン濃度を基準とする今回のイオン濃度急上昇時におけるイオン濃度の増加量であることを特徴とする地盤変位の予測方法である。
The present invention was created in order to solve these problems in view of the above circumstances, and the invention of claim 1 is characterized by the ion concentration of specific ions existing in the groundwater of the observation target area. The ground displacement amount is continuously measured, and a correlation between the ion concentration change amount of the specific ion and the ground displacement amount is obtained in advance based on the measured value, and the ion concentration change amount of the specific ion is calculated based on the correlation. A prediction method for predicting a displacement amount of a ground displacement that occurs next time, wherein the correlation is characterized in that the ground displacement amount is a linear function of the ion concentration change amount when the ion concentration changes by a predetermined amount or more. This is a method for predicting ground displacement.
In the invention of
According to a third aspect of the present invention, in the first or second aspect, the ion concentration change amount used when obtaining the correlation is the start of the current ion concentration rapid increase when an arbitrary ion concentration rapid increase is regarded as the current ion concentration rapid increase. The average value of the ion concentration in a certain period before the current rapid increase in ion concentration is used as the baseline concentration, and if there is a sudden increase in ion concentration within the certain period, the termination of the rapid increase in ion concentration is terminated. The average value of the ion concentration in the period from the start point to the start of the current rapid increase in ion concentration is used as the baseline concentration, and the amount of increase in the ion concentration at the current rapid increase in ion concentration with reference to the baseline concentration. This is a characteristic ground displacement prediction method.
請求項１の発明とすることにより、次回に発生する地盤変位の規模を把握できることになり、具体的な防災対策に大いに貢献できる。
請求項２または３の発明とすることにより、次回に発生する地盤変位の規模を正確に把握することができる。
By making it the invention of claim 1, it will be possible to grasp the scale of ground displacement that will occur next time, which can greatly contribute to specific disaster prevention measures.
By setting it as invention of
一般に、地すべりや表層崩壊等の斜面崩壊は、風化等による地盤の不安定化に起因して発生する。そして、安定した地盤内部の土粒子は比較的大きな土粒子であるが、不安定化した地盤内部では土粒子の微視的な変位や破壊が発生しており、土粒子は小さい粒子からなる粉状になっている。このように土粒子が粉状になった箇所は応力が変化するため土塊が移動し易い状態となり、ここにすべり面が発生する。このようなすべり面が発生するとすべり面周辺の土塊の応力に変化が生じるため土塊が安定になろうとして移動し始める（地盤変位）。この移動によってすべり面は除々に成長していって地盤内に広がり、成長したすべり面を滑動面として地盤全体が移動して地すべり崩壊等の土砂災害が発生するものと考えられる。 In general, slope failures such as landslides and surface layer failures occur due to instability of the ground due to weathering or the like. Soil particles in the stable ground are relatively large soil particles, but microscopic displacement and destruction of the soil particles occur in the unstable ground, and the soil particles are powders composed of small particles. It is in the shape. In this way, the location where the soil particles become powdery changes the stress, so that the mass of the soil easily moves, and a slip surface is generated here. When such a slip surface is generated, the stress of the soil block around the slip surface changes, so that the soil block begins to move to stabilize (ground displacement). By this movement, the slip surface gradually grows and spreads in the ground, and the entire ground moves with the grown slip surface as a sliding surface, and it is considered that landslide disasters such as landslide collapse occur.
一方、地盤変位の観測対象となる傾斜地に降る雨水は、地表表面に到達した時点では海塩由来の粒子や空中に浮遊する煤煙由来の粒子等を含有し、例えばナトリウムイオン、カルシウムイオン、塩素イオン、硫酸イオン等の低濃度の含有が認められる。このような地表表面における雨水のイオン濃度をバックグラウンド濃度とする。 On the other hand, the rainwater that falls on the slope where the ground displacement is to be observed, when it reaches the surface of the earth, contains particles derived from sea salt and smoke-derived particles floating in the air, such as sodium ions, calcium ions, and chlorine ions. In addition, a low concentration of sulfate ions and the like is observed. The ion concentration of rainwater on the surface of the ground is set as the background concentration.
傾斜地に降った雨水は、地表からやがて地中へと滲み込んでいき、地盤の土粒子の間を通過しながら地下水として集約されていく。
雨水を構成しているのは水であるが、水の分子は、一般に強い極性を示すことから、土粒子表面のイオン交換基（例えばシラノール基で、ケイ素原子に結合している水酸基）とのあいだでイオン交換をおこなうことが一般に知られている。このため地盤に浸透していった雨水はイオン交換がなされることによって前記バックグラウンド濃度よりも高いイオン濃度となる。このイオン濃度をベースライン濃度とする。
Rainwater that has fallen on the sloped land will infiltrate from the ground surface into the ground, and is collected as groundwater while passing between the soil particles on the ground.
Rainwater is composed of water, but water molecules generally exhibit a strong polarity, and therefore, the water molecules are bonded with ion exchange groups on the surface of the soil particles (for example, silanol groups and hydroxyl groups bonded to silicon atoms). It is generally known to perform ion exchange between them. For this reason, the rainwater that has permeated the ground has an ion concentration higher than the background concentration by ion exchange. This ion concentration is taken as the baseline concentration.
ところで、土粒子が微細化した場合は、土粒子表面積が全体として増加するため、それだけ土粒子表面のイオン交換基の数も多くなり、このような状態となった土粒子表面を通過した地下水は、微細化する前の土粒子の間を通過した地下水よりもイオンの量（イオン濃度）が多くなっている。このように微細化した直後の土粒子間を通過したことによって高くなったイオン濃度をピーク濃度とする。
前述のすべり面が発生している周辺では、摩擦や部分的な破壊によって土粒子が微細化した状態となっており、土粒子全体としての有効表面積が大きくなっているため、すべり面発生箇所を通過した地下水はピーク濃度となる。
By the way, when the soil particles are refined, since the surface area of the soil particles increases as a whole, the number of ion exchange groups on the surface of the soil particles increases accordingly, and the groundwater that has passed through the soil particle surface in such a state is The amount of ions (ion concentration) is greater than that of groundwater that has passed between the soil particles before being refined. Thus, the ion concentration which became high by having passed between the soil particles immediately after refinement | miniaturization is made into peak concentration.
In the vicinity where the above-mentioned slip surface is generated, the soil particles are miniaturized due to friction and partial breakage, and the effective surface area of the soil particles as a whole is large. Passed groundwater has a peak concentration.
このように傾斜地に降った雨水は傾斜地の表面から地中の地盤を経て地下水となる過程で地中の土粒子とイオン交換を行うため、観測対象地盤を通過した地下水のイオン濃度は地盤中の土質力学的な、あるいは化学的な状態を反映しており、前述したように地下水のイオン濃度がベースライン濃度からピーク濃度に上昇している場合は、観測対象地盤の何れかにすべり面が発生したと推測することが出来る。そして、このイオン濃度のベースライン濃度からピーク濃度への変化量と、すべり面の発生によって引き起される地盤変位の変位量との間には相関関係が存在すると考えられ、該相関関係を求めることで、特定イオンのイオン濃度変化量から次回に発生する地盤変位の変位量を予測することができるのではないかと推論した。 In this way, the rainwater that falls on the sloped land undergoes ion exchange with the soil particles in the ground in the process of becoming groundwater from the surface of the sloped ground through the ground in the ground, so the ion concentration of groundwater that has passed through the ground to be observed is If the groundwater ion concentration rises from the baseline concentration to the peak concentration as described above, reflecting the geomechanical or chemical state, a slip surface is generated on one of the observation grounds. Can be guessed. Then, it is considered that there is a correlation between the amount of change in the ion concentration from the baseline concentration to the peak concentration and the amount of displacement of the ground displacement caused by the occurrence of the slip surface, and the correlation is obtained. Therefore, it was inferred that the displacement amount of the ground displacement that would occur next time could be predicted from the amount of ion concentration change of the specific ions.
そこで、本発明の発明者は、長期に亘り、地すべりや表層崩壊等の地盤変位が発生するとされる複数の観測対象地区において、地下水中の特定イオンのイオン濃度の変化量と地盤変位量とを継続的に測定し、該測定値に基づいてイオン濃度変化量と地盤変位量との相関関係を検討した。 Therefore, the inventor of the present invention calculates the amount of change in the ion concentration and the amount of ground displacement in a specific ion in the groundwater in a plurality of observation target areas where landslides and surface layer collapse are expected to occur over a long period of time. The measurement was continuously performed, and the correlation between the ion concentration change amount and the ground displacement amount was examined based on the measured value.
前記相関関係を検討するにあたり、地盤の変位量の測定は、観測対象地区の地盤に傾斜計孔を掘削し、該傾斜計孔に傾斜計を設置して地盤変位量を測定した。また、地下水中の特定イオンのイオン濃度の測定は、観測対象地区の地盤を通過する地下水を継続的に採取し、イオンクロマトグラフィー／電気伝導率検出法によりイオン濃度を測定した。濃度測定する特定イオンは無機イオンであって、カルシウムイオン、ナトリウムイオン、カリウムイオン、硫酸イオン、塩化物イオンが例示される。 In examining the correlation, the displacement of the ground was measured by excavating an inclinometer hole in the ground of the observation target area and installing an inclinometer in the inclinometer hole to measure the amount of ground displacement. In addition, the ion concentration of specific ions in groundwater was measured by continuously collecting groundwater passing through the ground in the observation target area and measuring the ion concentration by ion chromatography / electric conductivity detection method. The specific ion whose concentration is measured is an inorganic ion, and examples thereof include calcium ion, sodium ion, potassium ion, sulfate ion, and chloride ion.
さらに、前記特定イオンのイオン濃度の測定に基づいてイオン濃度の変化量を求めるが、この場合に、観測された任意のイオン濃度の急上昇を今回のイオン濃度急上昇としたとき、該今回のイオン濃度急上昇の開始を終点とする今回のイオン濃度急上昇以前の一定期間（例えば、１〜数週間）におけるイオン濃度の平均値をベースライン濃度とし、また、前記一定期間内にイオン濃度の急上昇があった場合には、該イオン濃度急上昇の終了を始点とし今回のイオン濃度急上昇の開始を終点とする期間におけるイオン濃度の平均値をベースライン濃度として、該ベースライン濃度を基準とする今回の急上昇時のイオン濃度の増加量を、イオン濃度の変化量とする。 Further, the amount of change in the ion concentration is obtained based on the measurement of the ion concentration of the specific ion. In this case, when the sudden increase in the observed arbitrary ion concentration is regarded as the current ion concentration rapid increase, the current ion concentration The average value of the ion concentration in a certain period (for example, 1 to several weeks) before the current rapid increase in ion concentration with the start of the rapid increase as the end point is set as the baseline concentration, and there is a rapid increase in the ion concentration within the predetermined period. In this case, the average value of the ion concentration in the period starting from the end of the rapid increase in ion concentration and ending as the end of the rapid increase in ion concentration is used as the baseline concentration. The amount of increase in ion concentration is defined as the amount of change in ion concentration.
また、前述したように、イオン濃度が急上昇した場合にはすべり面が発生したと推測されるが、該すべり面の発生と、すべり面の発生により引き起される地盤変位の発生とのあいだにはタイムラグが存在する。つまり、イオン濃度が急上昇し、その後に地盤変位が発生することになり、そこで、イオン濃度変化量と地盤変位量との相関関係を検討する場合に、イオン濃度および地盤変位量の測定開始後に最初にイオン濃度の急上昇が発生したときのイオン濃度変化量と、該最初のイオン濃度の急上昇の発生後に最初に発生した地盤変位の変位量とを対応させ、以降は発生順に順次イオン濃度変化量と地盤変位量とを対応させて相関関係を求めた。 In addition, as described above, when the ion concentration increases rapidly, it is estimated that a slip surface has occurred. Between the occurrence of the slip surface and the occurrence of ground displacement caused by the occurrence of the slip surface. There is a time lag. In other words, the ion concentration suddenly increases, and then ground displacement occurs. Therefore, when examining the correlation between the ion concentration change amount and the ground displacement amount, the first time after the measurement of the ion concentration and the ground displacement amount is started. The amount of change in ion concentration when an ion concentration suddenly increases corresponds to the amount of displacement of ground displacement that first occurred after the first rapid increase in ion concentration. Correlation was obtained by correlating with the amount of ground displacement.
そして、複数の観測対象地区において、イオン濃度変化量と地盤変位量との相関関係を検討したところ、イオン濃度の変化量が所定量未満の場合には、イオン濃度変化量と地盤変位量との間に相関関係は認められないが、イオン濃度の変化量が所定量以上の場合には、地盤変位量はイオン濃度変化量の一次関数となることを発見した。さらに、上記所定量や一次関数の傾き、切片は、個々の観測対象地区の地盤の特性等によって異なるため、各観測対象地区毎に相関関係を予め求めておくことで、イオン濃度変化量から次回に発生する地盤変位の変位量を予測することができると考え、本発明を完成するに至った。 Then, in a plurality of observation target areas, the correlation between the ion concentration change amount and the ground displacement amount was examined. When the ion concentration change amount was less than a predetermined amount, the ion concentration change amount and the ground displacement amount Although no correlation was observed between them, it was discovered that the amount of ground displacement is a linear function of the amount of change in ion concentration when the amount of change in ion concentration is greater than or equal to a predetermined amount. Furthermore, since the predetermined amount, the slope of the linear function, and the intercept vary depending on the characteristics of the ground of each observation target area, the correlation is previously calculated for each observation target area, so that the next time the ion concentration change amount is calculated. Therefore, the present invention has been completed.
以下に、測定事例について具体的に説明する。
〈測定事例１〉
図２は、実際に地すべりが観測されているＡ地区において、約４年間に亘って継続的に測定した得られた、観測対象地盤を通過する地下水中に存在する特定イオン（カルシウムイオン）のイオン濃度変化量ｐｐｍ（ｍｇ／Ｌ）と、観測対象地盤の地盤変位量（ｍｍ）との関係を示すグラフ図である。
この地区の表層地盤は風化を強く受けた泥岩であって、過去に幾度かの地すべりが繰り返し発生している。
地盤変位量は、観測対象地盤にすべり面発生箇所を通る傾斜計孔を掘削し、該傾斜計孔内のすべり面深さ位置に傾斜計を設置して計測した。
また、特定イオンのイオン濃度変化量を測定するにあたり、観測対象地盤を通過する地下水として前記傾斜計孔内に貯留されている地下水を採取した。採取量は地下水１００ｍＬ（ミリリットル）であり、取り決めた時間毎（測定事例１では２４時間毎）に採取してポリエチレンびんに入れ、分析を行った。分析は、イオンクロマトグラフィー／電気伝導率検出法を用い、前記採取した地下水中のカルシウムイオン（Ｃａ２＋）の濃度を定量した。そして、イオン濃度が急上昇してピーク濃度が観測された場合に、該イオン濃度上昇を今回のイオン濃度上昇として、今回のイオン濃度上昇の開始を終点とする今回のイオン濃度上昇より前の一定期間（測定事例１では一週間）におけるイオン濃度の平均値をベースライン濃度とし、該ベースライン濃度を基準として今回のピーク濃度観測時におけるイオン濃度の増加量（ピーク濃度−ベースライン濃度）を求めた。また、前記一定期間内にイオン濃度の急上昇（前回のイオン濃度急上昇）があった場合には、前回のイオン濃度急上昇の終了を始点とし今回のイオン濃度急上昇の開始を終点とする期間におけるイオン濃度の平均値をベースライン濃度とした。
そして、前記図２を作製するにあたり、イオン濃度および地盤変位量の測定開始後に最初にイオン濃度の急上昇が発生したときのイオン濃度変化量と、該最初のイオン濃度の急上昇の発生後に最初に発生した地盤変位の変位量とを対応させ、以降は発生順に順次イオン濃度変化量と地盤変位量とを対応させて、イオン濃度変化量をＸ軸、地盤変位量をＹ軸の値としてプロットした。
Below, a measurement example is demonstrated concretely.
<Measurement example 1>
Fig. 2 shows the specific ions (calcium ions) present in the groundwater passing through the observation target ground, which were continuously measured for about 4 years in the A area where landslides are actually observed. It is a graph which shows the relationship between density | concentration variation | change_quantity ppm (mg / L) and the ground displacement amount (mm) of an observation object ground.
The surface ground of this area is mudstone that has been heavily weathered, and several landslides have occurred repeatedly in the past.
The amount of ground displacement was measured by excavating an inclinometer hole that passes through the location where the slip surface occurred in the observation target ground, and installing an inclinometer at the depth of the slip surface within the inclinometer hole.
Moreover, in measuring the ion concentration change amount of specific ions, groundwater stored in the dip meter hole was collected as groundwater passing through the observation target ground. The amount collected was 100 mL (milliliter) of ground water, and was collected every predetermined time (24 hours in Measurement Example 1) and placed in a polyethylene bottle for analysis. The analysis used ion chromatography / electric conductivity detection method, and the concentration of calcium ions (Ca 2+ ) in the collected ground water was quantified. And when the ion concentration rises rapidly and the peak concentration is observed, the ion concentration increase is regarded as the current ion concentration increase, and the start of the current ion concentration increase is the end point for a certain period before the current ion concentration increase. The average value of the ion concentration in the measurement example 1 (one week) was used as the baseline concentration, and the amount of increase in the ion concentration at this peak concentration observation (peak concentration−baseline concentration) was obtained based on the baseline concentration. . In addition, if there is a sudden increase in ion concentration (previous ion concentration rapid increase) within the predetermined period, the ion concentration in a period starting from the end of the previous rapid ion concentration increase and ending at the start of the current rapid ion concentration increase Was the baseline concentration.
Then, in the production of FIG. 2, the amount of change in ion concentration when the ion concentration suddenly increases for the first time after the start of measurement of the ion concentration and ground displacement amount, and the first occurrence after the first rapid increase in ion concentration occurs. The amount of change in the ground displacement was made to correspond, and thereafter, the amount of change in ion concentration and the amount of ground displacement were made to correspond in order of occurrence, and the amount of change in ion concentration was plotted as the value of the X axis and the amount of ground displacement was plotted as the value of the Y axis.
前記図２からＡ地区における特定イオン（カルシウムイオン）のイオン濃度変化量と地盤変化量との関係を検討したところ、イオン濃度の変化量が１３０ｐｐｍ未満の場合には、イオン濃度変化量と地盤変位量との間に相関関係は認められないが、イオン濃度変化量が１３０ｐｐｍ以上の場合には、地盤変位量とイオン濃度変化量とは一次関数の相関関係が存在すると推測され、そこで、イオン濃度の変化量が１３０ｐｐｍ以上の場合について回帰分析したところ、図２に示す回帰直線が得られた。この場合の決定係数Ｒ２は０．９０８８であり、強い相関関係が存在することが判明した。 2A and 2B, when the relationship between the ion concentration change amount of the specific ions (calcium ions) and the ground change amount in the A area is examined, when the ion concentration change amount is less than 130 ppm, the ion concentration change amount and the ground displacement are determined. There is no correlation with the amount, but when the ion concentration change is 130 ppm or more, it is presumed that there is a linear function correlation between the ground displacement and the ion concentration change. When a regression analysis was performed for the case where the amount of change of 130 ppm or more was obtained, a regression line shown in FIG. 2 was obtained. The coefficient of determination R 2 in this case is 0.9088, it was found that a strong correlation exists.
〈測定事例２〉
次に、Ｂ地区において、約４年間に亘って継続的に測定した得られた、観測対象地盤を通過する地下水中に存在する特定イオン（ナトリウムイオン）のイオン濃度変化量ｐｐｍ（ｍｇ／Ｌ）と、観測対象地盤の地盤変位量（ｍｍ）との関係を示すグラフ図を図３に示す。
このＢ地区は軟弱な地盤であって、斜面一帯の随所に小さな崩壊が観測されている。
地盤変位量は、前記測定事例１と同様に、観測対象地盤にすべり面発生箇所を通る傾斜計孔を掘削し、該傾斜計孔内のすべり面深さ位置に傾斜計を設置して計測した。
また、特定イオンのイオン濃度変化量の測定は、前記測定事例１と同様に、傾斜計孔内に貯留されている地下水を採取した。採取量は地下水１００ｍＬ（ミリリットル）で、取り決めた時間毎に採取し、イオンクロマトグラフィー／電気伝導率検出法を用い、前記採取した地下水中のナトリウムイオン（Ｎａ２＋）の濃度を定量した。そして、前記測定事例１と同様にしてベースライン濃度を求め、該ベースライン濃度を基準としてイオン濃度急上昇時におけるイオン濃度の変化量（ピーク濃度−ベースライン濃度）を求めた。
さらに、前記図２の作製と同様にして、発生順に順次イオン濃度変化量と地盤変位量とを対応させてプロットすることにより、イオン濃度急上昇時のイオン濃度変化量と、その後に発生した地盤変位量との関係を示す図３を作製した。
<Measurement example 2>
Next, in the B area, the ion concentration change ppm (mg / L) of specific ions (sodium ions) existing in the groundwater passing through the observation target ground, which was continuously measured over about 4 years. FIG. 3 is a graph showing the relationship between and the ground displacement amount (mm) of the observation target ground.
This B area is a soft ground, and small collapses have been observed throughout the slope.
The ground displacement was measured by excavating an inclinometer hole that passes through the location where the slip surface was generated in the ground to be observed, and installing an inclinometer at the depth of the slip surface in the inclinometer hole, as in measurement example 1 above. .
Moreover, the measurement of the ion concentration variation | change_quantity of a specific ion collect | recovered the groundwater stored in the clinometer hole similarly to the said measurement example 1. FIG. The collected amount was 100 mL (milliliter) of ground water, and was collected every predetermined time, and the concentration of sodium ions (Na 2+ ) in the collected ground water was quantified using ion chromatography / electric conductivity detection method. Then, the baseline concentration was obtained in the same manner as in the measurement example 1, and the amount of change in the ion concentration (peak concentration−baseline concentration) at the time when the ion concentration suddenly increased was obtained using the baseline concentration as a reference.
Further, in the same manner as in the production of FIG. 2 described above, the ion concentration change amount and the ground displacement amount are sequentially plotted in correspondence with each other in the order of generation, so that the ion concentration change amount when the ion concentration suddenly increases and the ground displacement generated thereafter. FIG. 3 showing the relationship with the amount was prepared.
前記図３からＢ地区における特定イオン（ナトリウムイオン）のイオン濃度変化量と地盤変化量との関係を検討したところ、イオン濃度の変化量が２００ｐｐｍ未満の場合には、イオン濃度変化量と地盤変位量との間に相関関係は認められないが、イオン濃度変化量が２００ｐｐｍ以上の場合には、地盤変位量とイオン濃度変化量とは一次関数の相関関係が存在すると推測され、そこで、イオン濃度の変化量が２００ｐｐｍ以上の場合について回帰分析したところ、図３に示す回帰直線が得られ、一次関数の相関関係が存在することが判明した。 When the relationship between the ion concentration change amount of the specific ion (sodium ion) and the ground change amount in the B area is examined from FIG. 3, when the ion concentration change amount is less than 200 ppm, the ion concentration change amount and the ground displacement. There is no correlation with the amount, but when the ion concentration change amount is 200 ppm or more, it is presumed that there is a linear function correlation between the ground displacement amount and the ion concentration change amount. When a regression analysis was performed with respect to the case where the amount of change was 200 ppm or more, the regression line shown in FIG. 3 was obtained, and it was found that there was a linear function correlation.
〈測定事例３〉
次に、Ｃ地区において、約４年間に亘って継続的に測定した得られた、観測対象地盤を通過する地下水中に存在する特定イオン（硫酸イオン）のイオン濃度変化量ｐｐｍ（ｍｇ／Ｌ）と、観測対象地盤の地盤変位量（ｍｍ）との関係を示すグラフ図を図４に示す。
このＣ地区は、断続的に地すべりが発生している地区である。
地盤変位量は、前記測定事例１、２と同様に、観測対象地盤にすべり面発生箇所を通る傾斜計孔を掘削し、該傾斜計孔内のすべり面深さ位置に傾斜計を設置して計測した。
また、特定イオンのイオン濃度変化量の測定は、前記測定事例１、２と同様に、傾斜計孔内に貯留されている地下水を採取した。採取量は地下水１００ｍＬ（ミリリットル）で、取り決めた時間毎に採取し、イオンクロマトグラフィー／電気伝導率検出法を用い、前記採取した地下水中の硫酸イオン（ＳＯ４ ２−）の濃度を定量した。そして、前記測定事例１、２と同様にしてベースライン濃度を求め、該ベースライン濃度を基準としてイオン濃度急上昇時におけるイオン濃度の変化量（ピーク濃度−ベースライン濃度）を求めた。
さらに、前記図２、３の作製と同様にして、発生順に順次イオン濃度変化量と地盤変位量とを対応させてプロットすることにより、イオン濃度急上昇時のイオン濃度変化量と、その後に発生した地盤変位量との関係を示す図４を作製した。
<Measurement example 3>
Next, in the C area, the ion concentration change ppm (mg / L) of specific ions (sulfate ions) present in the groundwater passing through the observation target ground, which was continuously measured for about 4 years. FIG. 4 is a graph showing the relationship between and the ground displacement amount (mm) of the observation target ground.
This C area is an area where landslides occur intermittently.
As with the measurement examples 1 and 2, the ground displacement amount is obtained by excavating an inclinometer hole passing through the slip surface occurrence location on the observation target ground and installing an inclinometer at the slip surface depth position in the inclinometer hole. Measured.
Moreover, the measurement of the ion concentration variation | change_quantity of a specific ion collect | recovered the groundwater stored in the inclination meter hole like the said measurement examples 1 and 2. The collected amount was 100 mL (milliliter) of ground water, and was collected every predetermined time, and the concentration of sulfate ion (SO 4 2− ) in the collected ground water was quantified using ion chromatography / electric conductivity detection method. Then, the baseline concentration was obtained in the same manner as in the measurement examples 1 and 2, and the amount of change in the ion concentration (peak concentration−baseline concentration) at the time of the rapid increase of the ion concentration was obtained using the baseline concentration as a reference.
Further, in the same manner as in the production of FIGS. 2 and 3, the ion concentration change amount and the ground displacement amount are sequentially plotted in correspondence with each other in the order of generation, thereby generating the ion concentration change amount when the ion concentration suddenly increases and thereafter generated. FIG. 4 showing the relationship with the amount of ground displacement was prepared.
前記図４からＣ地区における特定イオン（硫酸イオン）のイオン濃度変化量と地盤変化量との関係を検討したところ、イオン濃度の変化量が１００ｐｐｍ未満の場合には、イオン濃度変化量と地盤変位量との間に相関関係は認められないが、イオン濃度変化量が１００ｐｐｍ以上の場合には、地盤変位量とイオン濃度変化量とは一次関数の相関関係が存在すると推測され、そこで、イオン濃度の変化量が１００ｐｐｍ以上の場合について回帰分析したところ、図４に示す回帰直線が得られ、一次関数の相関関係が存在することが判明した。 When the relationship between the change in the ion concentration of specific ions (sulfate ions) and the amount of ground change in the C area is examined from FIG. 4, when the amount of change in the ion concentration is less than 100 ppm, the change in the ion concentration and the ground displacement. There is no correlation with the amount, but when the ion concentration change amount is 100 ppm or more, it is presumed that there is a linear function correlation between the ground displacement amount and the ion concentration change amount. As a result of regression analysis for the case where the amount of change of 100 ppm or more, the regression line shown in FIG. 4 was obtained, and it was found that there was a linear function correlation.
前記測定事例１〜３および実際に試みた他の複数の測定事例により、イオン濃度変化量と地盤変位量との間には、イオン濃度の変化量が所定量以上の場合に、地盤変位量はイオン濃度変化量の一次関数となるという相関関係が存在することが確認された。上記所定量や一次関数の傾き、切片は、個々の観測対象地盤の特性や、イオン濃度を測定する特定イオンによって異なるため、各観測対象地盤毎に相関関係を予め求めておく。そして、該相関関係に基づいて、イオン濃度が所定量以上変化した場合に、該イオン濃度変化量から次回に発生する地盤変位の変位量を予測することができる。これにより、次回に発生する地盤変位の規模を正確に把握できることになり、具体的な防災対策に大いに貢献できる。 According to the measurement examples 1 to 3 and a plurality of other measurement examples actually tried, when the ion concentration change amount is greater than or equal to a predetermined amount, the ground displacement amount is between the ion concentration change amount and the ground displacement amount. It was confirmed that there is a correlation that is a linear function of the amount of change in ion concentration. Since the predetermined amount, the slope of the linear function, and the intercept vary depending on the characteristics of the individual observation target ground and the specific ions for measuring the ion concentration, the correlation is obtained in advance for each observation target ground. Based on the correlation, when the ion concentration changes by a predetermined amount or more, it is possible to predict the displacement amount of the ground displacement generated next time from the ion concentration change amount. As a result, the scale of ground displacement that will occur next time can be accurately grasped, which can greatly contribute to specific disaster prevention measures.
尚、前述したように、すべり面の発生によるイオン濃度の上昇と、すべり面の発生により引き起される地盤変位の発生とのあいだにはタイムラグがあり、このため、イオン濃度変化量と地盤変位量との相関関係に基づいて、イオン濃度変化量から次回に発生する地盤変位の変位量を予測できることになるが、この場合に、次回に地盤変位が発生する有力なトリガーとして降水が考えられる。而して、観測対象地区の降水量（時間あたりの降水量、所定期間内における積算降水量、所定期間内における連続降水量等）を観測し、該降水量が所定量以上の場合に、前記相関関係に基づいて予測した地盤変位量での地盤変位が発生する可能性が高いと予測することができる。 As described above, there is a time lag between the increase in ion concentration due to the occurrence of a slip surface and the occurrence of ground displacement caused by the occurrence of a slip surface. Based on the correlation with the amount, the amount of displacement of the ground displacement that will occur next time can be predicted from the amount of change in ion concentration. In this case, precipitation is considered as a promising trigger for the next occurrence of ground displacement. Thus, when the amount of precipitation in the observation target area (precipitation per hour, accumulated precipitation within a predetermined period, continuous precipitation within a predetermined period, etc.) is observed, It can be predicted that there is a high possibility that ground displacement will occur at the ground displacement amount predicted based on the correlation.
また、観測対象地盤毎にイオン濃度変化量と地盤変位量との相関関係を求めるにあたり、正確な回帰直線を作成するにはデータ数が多い方が望ましいが、前述したように複数の観測事例により強い相関関係が存在していることが判明しているため、新たな観測対象地盤で相関関係を求めるにあたり、データ数が少なくても誤差は少ないと考えられる。また、新たな観測対象地盤で相関関係を求めるには長期に亘る観測が必要であることから、多少の誤差を考慮した上で、既に相関関係を求めてある似たような特性の地盤のものを代用することもできる。 In addition, in order to obtain the correlation between the ion concentration change amount and the ground displacement amount for each observation target ground, it is desirable to have a large number of data to create an accurate regression line. Since it has been found that a strong correlation exists, it is considered that there is little error even when the number of data is small when obtaining the correlation in the new observation target ground. In addition, since long-term observation is necessary to obtain the correlation in the new observation target ground, after considering some errors, the ground of similar characteristics for which correlation has already been obtained. Can be substituted.
本発明は、不安定な斜面地盤において発生する可能性のある地盤変位の変位量を予測する場合に利用することができる。 The present invention can be used for predicting the amount of ground displacement that may occur on unstable slope ground.
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| JP4219100B2 (en) * | 2001-05-18 | 2009-02-04 | 財団法人鉄道総合技術研究所 | Prediction device for ground displacement due to slope failure such as landslide and surface layer failure |
| JP2003004859A (en) * | 2001-06-18 | 2003-01-08 | Kiyoshi Wadatsumi | Earthquake foreknowing method |
| JP2009102841A (en) * | 2007-10-22 | 2009-05-14 | Tohoku Kensetsu Kyokai | Method of estimating concentration of specific ion in underground water, method of preparing hexa-diagram, and method and device for monitoring site to be monitored for displacement of ground |
| JP5669311B2 (en) * | 2011-03-31 | 2015-02-12 | 公益財団法人鉄道総合技術研究所 | Method and apparatus for predicting ground displacement |
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN111667125A (en) * | 2020-08-10 | 2020-09-15 | 成都嘉捷信诚信息技术有限公司 | Landslide displacement prediction method, landslide displacement prediction device and storage medium |
| CN111667125B (en) * | 2020-08-10 | 2020-11-20 | 成都嘉捷信诚信息技术有限公司 | Landslide displacement prediction method, landslide displacement prediction device and storage medium |
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| JP2014190782A (en) | 2014-10-06 |
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