JP2019065463A - Ground physical property estimation method after thawing - Google Patents
Ground physical property estimation method after thawing Download PDFInfo
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- JP2019065463A JP2019065463A JP2017188387A JP2017188387A JP2019065463A JP 2019065463 A JP2019065463 A JP 2019065463A JP 2017188387 A JP2017188387 A JP 2017188387A JP 2017188387 A JP2017188387 A JP 2017188387A JP 2019065463 A JP2019065463 A JP 2019065463A
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本発明は、凍土工法により凍結された地盤が解凍された後の地盤物性の変化を解凍収縮率から推定する地盤物性推定方法に関する。 The present invention relates to a soil physical property estimation method for estimating a change in ground physical properties after the ground frozen by the frozen soil construction method has been thawed from the thawing shrinkage rate.
従来、地盤の安定化、防水層の形成などを図る防護工として、耐力壁や止水壁を凍土壁によって形成する凍結工法が用いられている（例えば、特許文献１参照）。 Conventionally, as a protective work for stabilizing the ground, forming a waterproof layer, and the like, a freezing method in which a bearing wall and a water blocking wall are formed by a frozen soil wall is used (see, for example, Patent Document 1).
一方、凍結工法においては、凍土解凍（融解）後の地盤物性の変化を把握することも重要であるが、従来の研究実績では研究者により粘性土において強度・剛性が低下する、または増加するという相反する結論が示されている。その理由は実験方法に原因があると考えられ、これを解消するために凍結・融解・せん断の全過程を同一セルの中で行えるようにした三軸試験装置が実用化されている（非特許文献１参照）。なお、砂質土は、凍結前、解凍後も土粒子の構造が変化しないので、強度・剛性も変化しない。 On the other hand, in the freezing method, it is important to grasp the change of the ground physical property after the frozen soil thawing (thawing), but in the conventional research results, the strength and rigidity decrease or increase in the sticky soil by researchers Conflicting conclusions are shown. The reason is considered to be caused by the experimental method, and in order to eliminate this, a triaxial test apparatus has been put into practical use that can perform all processes of freezing, thawing and shearing in the same cell (non-patented) Reference 1). In addition, since the structure of soil particles does not change even before freezing and after thawing, the sandy soil does not change in strength and rigidity.
しかしながら、三軸試験を行うためには地盤の採取（サンプリング）が必要であり、そもそも三軸試験の方法自体が確立していないという問題点があり、凍土解凍後の地盤物性の変化を把握するための新たな手法の開発が望まれていた。 However, in order to conduct a triaxial test, sampling (sampling) of the ground is necessary, and there is a problem that the method of the triaxial test itself has not been established in the first place, and changes in ground physical properties after frozen soil thawing are grasped The development of new methods for
本発明は、上記事情に鑑み、解凍収縮率に着目することで、凍結工法を用いて凍結された地盤の解凍後の物性をより簡便に把握する方法を提供することを目的とする。 An object of this invention is to provide the method of grasping | ascertaining more simply the physical property after thawing | decompression of the ground frozen using the freezing construction method in view of the said situation by paying attention to a thawing | shrinkage contraction rate.
上記の目的を達するために、この発明は以下の手段を提供している。 In order to achieve the above object, the present invention provides the following means.
本発明の解凍後の地盤物性推定方法は、凍結された地盤の解凍収縮率に基づき、解凍後の地盤の物性を特定するようにしたことを特徴とする。 The ground physical property estimation method after thawing according to the present invention is characterized in that the physical properties of the ground after thawing are specified based on the thawing contraction rate of the frozen ground.
また、本発明の解凍後の地盤物性推定方法においては、解凍収縮率が負の場合に、解凍後の地盤の強度・剛性が増加し、正の場合には解凍後の地盤の強度・剛性が低下すると判断することを特徴とする。 In the method of estimating physical properties after thawing of the present invention, the strength and rigidity of the ground after thawing increase when the thawing contraction rate is negative, and when the positive, the strength and rigidity of the ground after thawing are It is characterized by judging that it falls.
本発明の凍結工法の地盤物性推定方法においては、凍結工法を用いて凍結された地盤の解凍後の物性をより簡便に把握することが可能になる。 In the method for estimating the physical properties of the ground of the freezing method of the present invention, it is possible to easily grasp the physical properties after thawing of the ground frozen using the freezing method.
以下、図１及び図２を参照し、本発明の一実施形態に係る解凍後の地盤物性推定方法について説明する。ここで、本実施形態では、凍結工法を用いて凍結された地盤（凍土）の解凍後の物性の変化を解凍収縮率から推定する方法に関するものである。 Hereinafter, with reference to FIG.1 and FIG.2, the ground physical-property estimation method after thawing | decompression which concerns on one Embodiment of this invention is demonstrated. Here, the present embodiment relates to a method of estimating a change in physical properties after thawing of ground (freezed ground) frozen using a freezing method from the thawing shrinkage rate.
本実施形態の解凍後の地盤物性推定方法においては、凍結融解のメカニズムを考慮し、解凍収縮率に着目する。 In the method of estimating the physical property of the ground after thawing of the present embodiment, the mechanism of freezing and thawing is taken into consideration, and the thawing and contraction rate is noted.
具体的に、図１に示すように、粘性土は、未凍土側から吸水しながら凍結し膨張する。解凍後は、軟弱な粘性土では凍結により脱水圧密を生じる。このとき、凍結前の原地盤以上に収縮することから、解凍後の圧密土は密度が増加し、強度・剛性も増加すると考えられる。 Specifically, as shown in FIG. 1, the cohesive soil freezes and expands while absorbing water from the unfrozen soil side. After thawing, in soft clay soil, dehydration consolidation occurs by freezing. At this time, since it shrinks more than the original ground before freezing, it is thought that the density of the consolidated soil after thawing increases and the strength and rigidity also increase.
一方、硬質粘性土では、凍結中に吸水した水の解凍時の排水が不十分な場合に解凍後も原地盤以上に膨張したままになる。このことから、解凍後に密度が減少し、強度・剛性が低下する場合もあると考えられる。 On the other hand, in the case of hard viscous soil, when the drained water at the time of thawing of water absorbed during freezing is insufficient, it remains expanded beyond the original ground even after thawing. From this, it is considered that the density may decrease after thawing, and the strength and rigidity may decrease.
すなわち、解凍収縮率が負（収縮、沈下）の場合には、解凍後の強度・剛性が増加する、正（膨張、浮上）の場合には低下する傾向があると考えられる。 That is, it is considered that the strength and rigidity after thawing tend to increase when the thawing shrinkage rate is negative (contraction, settlement), and to decrease when the thawing shrinkage ratio is positive (expansion, floating).
これに基づき、非特許文献１などのデータから、解凍収縮率と凍土解凍後の強度変化を整理すると、図２に示すように、相関があることが確認された。したがって、本実施形態の凍結工法の地盤物性推定方法においては、三軸試験を行うことなく、解凍収縮率に基づき、より簡便に凍土解凍後の地盤の物性を把握することができる。
ここで、粘性土の解凍収縮率については、過去に十分に蓄積されているデータを用い、試験を行うことなく解凍後の解凍収縮率を設定できる。さらに、必要に応じて、標準的な凍上・沈下試験を行うことにより解凍収縮率を算出できる。
Based on this, it was confirmed from the data of
Here, with respect to the thawing and shrinking rate of the cohesive soil, it is possible to set the thawing and shrinking rate after thawing without performing a test using data accumulated sufficiently in the past. Furthermore, if necessary, the thawing and shrinking rate can be calculated by performing a standard freeze-up and sink test.
このとき、解凍収縮率のデータベースとしては、例えば、２０１２年現在で過去４１年間の約５００種類の土の情報が収録され、これを用いればよい。参考文献として、例えば、小松紗代子，隅谷大作，上田保司：凍結性状データベースの分析に基づく凍土の解凍収縮特性，地盤工学研究発表会発表講演集Ｎｏ．４７，２０１２年がある。 At this time, for example, information of about 500 types of soil for the past 41 years as of 2012 is recorded as a database of the thawing shrinkage rate, and this may be used. As a reference, for example, Kyoko Komatsu, Daisaku Sumiya, Hoji Ueda: Defrosting and shrinking characteristics of frozen soil based on analysis of frozen property database, Proceedings of Geotechnical Engineering Conference No. There are 47, 2012 years.
凍上・沈下試験による解凍収縮率の算出については、例えば、地盤工学会基準（ＪＧＳ０１７１−２００９）「凍上量予測のための土の凍上試験方法」に基づき、解凍収縮率（解凍沈下率）を算出すればよい。 For the calculation of the thawing shrinkage rate by the freeze-up / sink test, for example, the thawing shrinkage rate (thaw-sink rate) is calculated based on the Geotechnical Society Standard (JGS 0171-2009) “Method of testing the freeze-up of soil for forecasting the amount of frost”. do it.
したがって、本実施形態の解凍後の地盤物性推定方法においては、上記のようなデータベースを用い、試験を実施することなく解凍収縮率を求めることにより、凍土解凍後の地盤の物性を把握することができる。 Therefore, in the soil physical property estimation method after thawing of this embodiment, the physical property of the ground after thawing of the frozen soil can be grasped by obtaining the thawing shrinkage rate without carrying out the test using the above-mentioned database it can.
以上、本発明による解凍後の地盤物性推定方法の一実施形態について説明したが、本発明は上記の一実施形態に限定されるものではなく、その趣旨を逸脱しない範囲で適宜変更可能である。 As mentioned above, although one Embodiment of the ground physical-property estimation method after thawing | decompression by this invention was described, this invention is not limited to said one embodiment, It can change suitably in the range which does not deviate from the meaning.
Claims (2)
前記解凍収縮率が負の場合に、解凍後の地盤の強度・剛性が増加し、正の場合には解凍後の地盤の強度・剛性が低下すると判断することを特徴とする解凍後の地盤物性推定方法。 In the ground physical property estimation method after thawing according to claim 1,
It is judged that the strength and rigidity of the ground after thawing increase when the thawing contraction rate is negative, and it is judged that the strength and rigidity of the ground after thawing decrease when positive. Estimation method.
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Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH06248635A (en) * | 1993-02-26 | 1994-09-06 | Seiken:Kk | Strengthening method for bearing wall in freezing |
| JP2001003350A (en) * | 1999-06-18 | 2001-01-09 | Kinjo Rubber Kk | Soil improvement method by board drain making use of freezing-thawing |
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Patent Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH06248635A (en) * | 1993-02-26 | 1994-09-06 | Seiken:Kk | Strengthening method for bearing wall in freezing |
| JP2001003350A (en) * | 1999-06-18 | 2001-01-09 | Kinjo Rubber Kk | Soil improvement method by board drain making use of freezing-thawing |
Non-Patent Citations (1)
| Title |
|---|
| 小野丘・三田地利之: "粘性土の軸対称三軸応力下における凍結・融解履歴について", 土木学会論文集, vol. 617/3-46, JPN6021030751, March 1999 (1999-03-01), JP, pages 275 - 282, ISSN: 0004566444 * |
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