JP2007182695A - Diameter estimating method for soil improving body - Google Patents
Diameter estimating method for soil improving body Download PDFInfo
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- JP2007182695A JP2007182695A JP2006001311A JP2006001311A JP2007182695A JP 2007182695 A JP2007182695 A JP 2007182695A JP 2006001311 A JP2006001311 A JP 2006001311A JP 2006001311 A JP2006001311 A JP 2006001311A JP 2007182695 A JP2007182695 A JP 2007182695A
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- 239000002689 soil Substances 0.000 title claims abstract description 117
- 238000000034 method Methods 0.000 title claims abstract description 78
- ODINCKMPIJJUCX-UHFFFAOYSA-N calcium oxide Inorganic materials [Ca]=O ODINCKMPIJJUCX-UHFFFAOYSA-N 0.000 claims abstract description 96
- BRPQOXSCLDDYGP-UHFFFAOYSA-N calcium oxide Chemical compound [O-2].[Ca+2] BRPQOXSCLDDYGP-UHFFFAOYSA-N 0.000 claims abstract description 94
- 239000000292 calcium oxide Substances 0.000 claims abstract description 94
- 239000000463 material Substances 0.000 claims abstract description 44
- 239000002002 slurry Substances 0.000 claims abstract description 36
- 239000004568 cement Substances 0.000 claims abstract description 34
- 238000002156 mixing Methods 0.000 claims abstract description 11
- 238000011088 calibration curve Methods 0.000 claims description 44
- 238000005259 measurement Methods 0.000 claims description 34
- 238000002360 preparation method Methods 0.000 claims description 16
- 238000003756 stirring Methods 0.000 claims description 15
- 238000010276 construction Methods 0.000 abstract description 17
- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical compound [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 description 69
- VEXZGXHMUGYJMC-UHFFFAOYSA-N Hydrochloric acid Chemical compound Cl VEXZGXHMUGYJMC-UHFFFAOYSA-N 0.000 description 42
- 238000006386 neutralization reaction Methods 0.000 description 12
- 238000004448 titration Methods 0.000 description 10
- 230000002378 acidificating effect Effects 0.000 description 9
- 238000004364 calculation method Methods 0.000 description 8
- 238000013019 agitation Methods 0.000 description 7
- 238000005553 drilling Methods 0.000 description 7
- 238000000691 measurement method Methods 0.000 description 7
- 239000007787 solid Substances 0.000 description 7
- 230000015572 biosynthetic process Effects 0.000 description 5
- 238000002347 injection Methods 0.000 description 5
- 239000007924 injection Substances 0.000 description 5
- 238000006243 chemical reaction Methods 0.000 description 4
- 230000007423 decrease Effects 0.000 description 4
- 238000009412 basement excavation Methods 0.000 description 3
- 238000005452 bending Methods 0.000 description 3
- 239000000203 mixture Substances 0.000 description 3
- 238000007711 solidification Methods 0.000 description 3
- 230000008023 solidification Effects 0.000 description 3
- 238000012360 testing method Methods 0.000 description 3
- 235000008733 Citrus aurantifolia Nutrition 0.000 description 2
- FAPWRFPIFSIZLT-UHFFFAOYSA-M Sodium chloride Chemical compound [Na+].[Cl-] FAPWRFPIFSIZLT-UHFFFAOYSA-M 0.000 description 2
- 235000011941 Tilia x europaea Nutrition 0.000 description 2
- 238000004458 analytical method Methods 0.000 description 2
- 239000007864 aqueous solution Substances 0.000 description 2
- 238000002474 experimental method Methods 0.000 description 2
- 239000004571 lime Substances 0.000 description 2
- 238000010907 mechanical stirring Methods 0.000 description 2
- 239000000243 solution Substances 0.000 description 2
- 239000007921 spray Substances 0.000 description 2
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 2
- 238000007596 consolidation process Methods 0.000 description 1
- 230000008602 contraction Effects 0.000 description 1
- 238000001514 detection method Methods 0.000 description 1
- 238000007599 discharging Methods 0.000 description 1
- 238000004090 dissolution Methods 0.000 description 1
- 239000011521 glass Substances 0.000 description 1
- IXCSERBJSXMMFS-UHFFFAOYSA-N hcl hcl Chemical compound Cl.Cl IXCSERBJSXMMFS-UHFFFAOYSA-N 0.000 description 1
- 238000011835 investigation Methods 0.000 description 1
- 239000007788 liquid Substances 0.000 description 1
- 239000004570 mortar (masonry) Substances 0.000 description 1
- 230000002093 peripheral effect Effects 0.000 description 1
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- 239000011780 sodium chloride Substances 0.000 description 1
- 238000013112 stability test Methods 0.000 description 1
- 230000005514 two-phase flow Effects 0.000 description 1
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- Consolidation Of Soil By Introduction Of Solidifying Substances Into Soil (AREA)
Abstract
Description
本発明は、高圧噴射撹拌工法を用いた地盤改良工事によって造成される円柱状の地盤改良体の径の推定方法に関する。 The present invention relates to a method for estimating the diameter of a cylindrical ground improvement body formed by ground improvement work using a high-pressure jet stirring method.
軟弱地盤中に、セメント系固化材を含むスラリーを注入することによって、軟弱地盤を固結させて、せん断強さを増大させ、地盤を改良する工法には、主に高圧噴射撹拌工法と機械撹拌工法がある。
高圧噴射撹拌工法は、ロッドを用いて地盤を所定の深度まで削孔した後、該ロッドを回転させながら引き上げつつ、ロッドの下端に装着されている噴射ノズルから、セメント系固化材を含むスラリーを水平方向に超高圧で噴射することによって、既存の地盤を切削しつつ、スラリーと、地盤を形成する軟弱土を撹拌混合し、セメント系固化材を含む円柱状の地盤改良体を形成する工法である。
一方、機械撹拌工法は、下端に撹拌翼を装着したロッドを用いて、地盤を所定の深度まで削孔した後、該ロッドを回転させながら引き上げつつ、撹拌翼の近傍のスラリー吐出口から、セメント系固化材を含むスラリーを低圧で吐出して、固化対象土とスラリーを撹拌翼の回転で機械的に混合撹拌することによって、撹拌翼の径と略同一の径を有する円柱状の地盤改良体を形成する工法である。
By injecting slurry containing cement-based solidification material into soft ground, the soft ground is consolidated, shear strength is increased, and the ground is improved mainly by high-pressure jet stirring and mechanical stirring. There is a construction method.
In the high-pressure jet agitation method, after drilling the ground to a predetermined depth using a rod, the slurry containing cement-based solidifying material is removed from the spray nozzle attached to the lower end of the rod while pulling up the rod while rotating the rod. This is a method of forming a cylindrical ground improvement body containing cement-based solidification material by stirring and mixing slurry and soft soil forming the ground while cutting the existing ground by injecting with ultra high pressure in the horizontal direction. is there.
On the other hand, the mechanical stirring method uses a rod with a stirring blade at the lower end, drills the ground to a predetermined depth, and then pulls up the cement while rotating the rod while rotating the rod from the slurry outlet near the stirring blade. A cylindrical ground improvement body having a diameter substantially the same as the diameter of the stirring blade is obtained by discharging the slurry containing the solidified material at low pressure and mechanically mixing and stirring the soil to be solidified and the slurry by the rotation of the stirring blade. Is a method of forming
高圧噴射撹拌工法による施工に際し、地盤改良体について所望の強度を確保することに加えて、地盤改良体の径を精度良く推定することは、重要である。すなわち、地盤改良体の相互のラップ（隣接する地盤改良体間の改良領域の重複）が必要な場合に、地盤改良体の径を実際よりも過大に推定した場合には、隣接する円柱状の地盤改良体相互間の距離を過大に定めてしまい、地盤改良体相互間の中央付近に、地盤改良されない領域を残すことになりかねない。一方、地盤改良体の径を実際よりも過小に推定した場合には、隣接する円柱状の地盤改良体相互間の距離を過小に定めてしまい、地盤改良体相互間に重複した改良領域（ラップ部分）を広く形成し、コストの増大及び作業効率の低下を招くことになる。一方、地盤改良体の径の大きさは、高圧噴射撹拌工法に用いる装置の種類によって一つの定数として定まるものではなく、地盤の土質の条件、特に地盤の切削の容易性によって変化する。そのため、高圧噴射撹拌工法においては、地盤改良体の径を精度良く推定することが要請されるのである。 In the construction by the high-pressure jet agitation method, it is important to accurately estimate the diameter of the ground improvement body in addition to ensuring the desired strength of the ground improvement body. That is, when mutual wrapping of ground improvement bodies (overlap of improvement areas between adjacent ground improvement bodies) is necessary, if the diameter of the ground improvement body is estimated to be larger than the actual, If the distance between the ground improvement bodies is set excessively, an area where the ground improvement is not performed may be left in the vicinity of the center between the ground improvement bodies. On the other hand, when the diameter of the ground improvement body is estimated to be smaller than the actual size, the distance between adjacent cylindrical ground improvement bodies is set too small, and the improvement region (lap) overlapped between the ground improvement bodies. Part) is formed widely, resulting in an increase in cost and a decrease in work efficiency. On the other hand, the diameter of the ground improvement body is not determined as one constant depending on the type of the apparatus used for the high-pressure jet agitation method, but changes depending on the soil condition of the ground, especially the ease of cutting of the ground. Therefore, in the high-pressure jet stirring method, it is required to accurately estimate the diameter of the ground improvement body.
従来、地盤改良体の径を推定する方法として、地盤改良体の周縁付近と推定される領域内の複数の地点において、地盤改良体の存在する深度区間の深さまでボーリングを行ない、地盤改良体の外縁に当たるボーリングコアの固結状況から、地盤改良体の外縁を定め、地盤改良体の径を推定する方法が知られている。
しかし、この方法には、（ａ）地盤改良体の外縁に当たるボーリングコアを複数本得るまでに、多数回のボーリングを行なわなければならないことがあり、この場合、多大の労力及び作業時間を要すること、（ｂ）地表から深い地点における地盤改良体の径を確認する場合、硬質な地盤改良体から軟弱な未改良地盤の方へのボーリング孔の孔曲がりが発生しやすいなど、ボーリング孔を正確に鉛直方向に形成させることが困難なことがあり、地盤改良体の径の測定の精度が低下しがちである、などの欠点がある。
Conventionally, as a method for estimating the diameter of the ground improvement body, at a plurality of points in the region estimated to be near the periphery of the ground improvement body, drilling is performed to the depth of the depth section where the ground improvement body exists, A method for determining the outer edge of the ground improvement body and estimating the diameter of the ground improvement body from the consolidation state of the boring core hitting the outer edge is known.
However, in this method, (a) it may be necessary to perform boring a large number of times before obtaining a plurality of boring cores corresponding to the outer edge of the ground improvement body. In this case, much labor and work time are required. (B) When confirming the diameter of the ground improvement body at a deep point from the ground surface, it is easy to generate a hole in the borehole from the hard ground improvement body toward the soft unmodified ground. There are drawbacks that it may be difficult to form in the vertical direction, and the accuracy of the measurement of the diameter of the ground improvement body tends to be lowered.
そのため、地盤改良体の径の推定方法として、他の方法が提案されている。
一例として、地中に埋設されている円柱状地中固結体の直径の計測方法において、前記固結体の中心点から所定距離を離れた場所から傾斜して掘削孔を穿孔し、掘削抵抗の変化によって、前記固結体の周縁部の位置を求めることを特徴とする地中固結体の直径計測方法が提案されている（特許文献１）。
他の例として、回転軸の先端近傍に設けた高圧液体を噴出するノズルよりも下方に、半径方向に伸縮する機構を含む改良径検知翼を備えている掘削孔計測装置が提案されている（特許文献２）。
As an example, in the method of measuring the diameter of a cylindrical underground solid body buried in the ground, a drilling hole is drilled at a predetermined distance from the center point of the solid body, and a drilling resistance is formed. A method for measuring the diameter of a submerged solid body has been proposed in which the position of the peripheral portion of the solid body is obtained by a change in the above (Patent Document 1).
As another example, a drilling hole measuring device having an improved diameter detection blade including a mechanism that expands and contracts in a radial direction is proposed below a nozzle that ejects high-pressure liquid provided near the tip of a rotating shaft ( Patent Document 2).
前記の特許文献１の方法は、（ａ）土中に大きな礫等の障害物が存在する場合に、固結体（円柱状の地盤改良体）の中心点を通るように掘削孔を正確に穿孔することは、困難である、（ｂ）土質の異なる複数の層からなる地盤（互層地盤）に適用する場合、掘削抵抗の変化が、土質の変化によるものか、それとも地盤改良によるものかの判断が困難なことがある、（ｃ）隣接して連続的に形成された複数の固結体に対しては、適用することができない、（ｄ）固結体の周囲の地表面上に民家等がある場合、掘削孔を穿孔するための場所を確保することができない、などの問題がある。
前記の特許文献２の方法は、（ａ）改良径検知翼の機構が複雑であり、装置のコストが増大する、（ｂ）改良径検知翼の伸縮が、大きな礫等の異物によって妨げられ、計測が不能または不正確になるおそれがある、（ｃ）地盤の土質がヘドロや超軟弱土である場合には、地盤改良体の周囲の未改良地盤と、地盤改良体との強度差が小さく、改良径の推定が困難になる、などの問題がある。
そこで、本発明は、複雑な装置等を必要とせず簡易かつ低コストであって、施工対象地盤が如何なる条件を有していても短時間で効率的に精度良く、地盤改良体の径を推定しうる方法を提供することを目的とする。
In the method of the above-mentioned Patent Document 1, (a) when an obstacle such as a large gravel exists in the soil, the excavation hole is accurately passed through the center point of the consolidated body (columnar ground improvement body). It is difficult to drill. (B) When applied to ground consisting of multiple layers with different soils (alternate ground), whether excavation resistance changes are due to soil changes or ground improvement Judgment may be difficult. (C) Cannot be applied to a plurality of adjacently formed solid bodies. (D) A private house on the ground surface around the solid bodies. If there is, etc., there is a problem that a place for drilling the excavation hole cannot be secured.
In the method of
Therefore, the present invention is simple and low-cost without requiring a complicated device, etc., and estimates the diameter of the ground improvement body in a short time, efficiently and accurately regardless of the conditions of the target ground. It aims to provide a possible method.
本発明者は、上述の課題を解決するために鋭意検討した結果、地盤改良材であるセメント系固化材に酸化カルシウムが含まれていることから、地盤改良材を地中に噴射して形成される円柱状の地盤改良体に含まれる酸化カルシウムの含有率を測定するとともに、この測定値が大きいほど地盤改良体の径が小さいという関係を利用すれば、地盤改良体の径を推定することができると考えた。そして、この着想に基づいて得た地盤改良体の径の推定値が、地盤改良体の径の実際の値と一致するかを実験で調べたところ、この推定値が実際の径とほぼ同じであり、高い精度を有することを見出した。かかる着想及び実証を通じて、本発明は完成されたものである。 As a result of intensive investigations to solve the above-mentioned problems, the present inventor has been formed by injecting a ground improvement material into the ground because calcium oxide is contained in the cement-based solidified material that is the ground improvement material. It is possible to estimate the diameter of the ground improvement body by measuring the content of calcium oxide contained in the cylindrical ground improvement body and using the relationship that the larger the measured value, the smaller the diameter of the ground improvement body. I thought it was possible. An experiment was conducted to check whether the estimated value of the ground improvement body diameter obtained based on this idea matches the actual value of the diameter of the ground improvement body. And found high accuracy. Through this idea and demonstration, the present invention has been completed.
具体的には、本発明は、以下の［１］〜［３］を提供するものである。
［１］ 高圧噴射撹拌工法によって、酸化カルシウムを主成分とするセメント系固化材を含むスラリーを地中に噴射し、水平方向の断面が略円形である円柱状の地盤改良体を形成する地盤改良工事において、上記地盤改良体の径を推定する方法であって、上記地盤改良体の酸化カルシウム含有率が大きいほど、上記地盤改良体の径が小さいという関係を利用して、上記地盤改良体の酸化カルシウム含有率の測定値に基づいて、上記地盤改良体の径を推定することを特徴とする地盤改良体の径の推定方法。
［２］ 上記地盤改良体の改良前の土の一部を採取し、該採取した土と上記セメント系固化材を、少なくとも３つの異なる配合割合で混合して、少なくとも３種の検量線作成用試料を調製する試料調製工程と、上記少なくとも３種の検量線作成用試料の各々について、酸化カルシウム含有率を測定する試料測定工程と、上記試料測定工程で得られた酸化カルシウム含有率と、上記少なくとも３種の検量線作成用試料の各々について算出した地盤改良体の径の理論値との関係曲線である検量線を作成する検量線作成工程と、上記地盤改良体の土の一部を採取し、該採取した土の酸化カルシウム含有率を測定する改良土測定工程と、上記改良土測定工程で得られた酸化カルシウム含有率を、上記検量線に適用して、上記地盤改良体の径の推定値を得る推定値決定工程を含む前記［１］の地盤改良体の径の推定方法。
［３］ 上記地盤改良体の改良前の土の一部を採取し、該採取した土の酸化カルシウム含有率を測定する原土測定工程と、上記地盤改良体の土の一部を採取し、該採取した土の酸化カルシウム含有率を測定する改良土測定工程と、上記原土測定工程で得られた酸化カルシウム含有率と、上記改良土測定工程で得られた酸化カルシウム含有率と、上記セメント系固化材の既知の酸化カルシウム含有率とに基づいて、上記地盤改良体の径の推定値を得る推定値決定工程を含む前記［１］の地盤改良体の径の推定方法。
Specifically, the present invention provides the following [1] to [3].
[1] A ground improvement that forms a cylindrical ground improvement body having a substantially circular cross section in the horizontal direction by injecting a slurry containing a cement-based solidified material mainly composed of calcium oxide into the ground by a high-pressure jet stirring method. In construction, a method for estimating the diameter of the ground improvement body, using the relationship that the larger the calcium oxide content of the ground improvement body, the smaller the diameter of the ground improvement body, A method for estimating a diameter of a ground improvement body, wherein the diameter of the ground improvement body is estimated based on a measured value of a calcium oxide content rate.
[2] A part of the soil before improvement of the ground improvement body is collected, and the collected soil and the cement-based solidified material are mixed in at least three different blending ratios to prepare at least three kinds of calibration curves. A sample preparation step for preparing a sample, a sample measurement step for measuring a calcium oxide content for each of the at least three types of calibration curve preparation samples, a calcium oxide content obtained in the sample measurement step, and the above A calibration curve creation process for creating a calibration curve that is a relationship curve with the theoretical value of the diameter of the ground improvement body calculated for each of at least three types of calibration curve creation samples, and a part of the soil of the ground improvement body is collected. And applying the improved soil measuring step for measuring the calcium oxide content of the collected soil and the calcium oxide content obtained in the improved soil measuring step to the calibration curve, Get an estimate The method for estimating the diameter of the ground improvement body according to [1], including an estimated value determining step.
[3] A part of the soil before improvement of the ground improvement body is collected, a raw soil measurement step of measuring the calcium oxide content of the collected soil, a part of the soil of the ground improvement body is collected, Improved soil measuring step for measuring calcium oxide content of the collected soil, calcium oxide content obtained in the raw soil measuring step, calcium oxide content obtained in the improved soil measuring step, and cement The estimation method of the diameter of the ground improvement body of said [1] including the estimated value determination process of obtaining the estimated value of the diameter of the said ground improvement body based on the known calcium oxide content rate of a system solidification material.
本発明の地盤改良体の径の推定方法によれば、複雑な装置等を必要とせず簡易かつ低コストであって、施工対象地盤が如何なる条件を有していても短時間で効率的に精度良く、地盤改良体の径を推定することができる。
すなわち、地盤改良体の内部の任意の地点から、少量の改良土を試料として採取し、この試料の酸化カルシウム含有率を測定するなどの簡易な作業を行なうだけで、地盤改良体の径を精度良く推定することができる。特に、従来、地盤改良体の外縁に当たるボーリングコアを得る際に、ボーリング孔の孔曲がりが発生して、地盤改良体の径の測定の精度が低下しがちであったのに対し、本発明では、地盤改良体の外縁でボーリングを行なう必要がないため、孔曲がりによる測定精度の低下の問題が生じず、常に高い精度で推定値を得ることができる。
また、本発明は、ラップ部分を有するように隣接して連続的に形成された複数の地盤改良体を対象とする場合や、地中に大きな礫等の障害物が存在する場合や、土質の異なる複数の層や超軟弱土からなる地盤を対象とする場合や、地盤改良体の周囲に民家等がある場合などにおいても、何ら支障なく実施することができる。
According to the method of estimating the diameter of the ground improvement body of the present invention, it is simple and low-cost without requiring a complicated device or the like, and can be accurately accurately in a short time regardless of the conditions of the construction target ground. The diameter of the ground improvement body can be estimated well.
In other words, a small amount of improved soil is sampled from any point inside the ground improvement body as a sample, and the diameter of the ground improvement body can be accurately adjusted by simply performing a simple operation such as measuring the calcium oxide content of this sample. It can be estimated well. In particular, conventionally, when obtaining a boring core that hits the outer edge of the ground improvement body, the bending accuracy of the diameter of the ground improvement body has been apt to be reduced due to the occurrence of the bending of the borehole. Further, since it is not necessary to perform boring at the outer edge of the ground improvement body, there is no problem of a decrease in measurement accuracy due to hole bending, and an estimated value can always be obtained with high accuracy.
In addition, the present invention is intended for a plurality of ground improvement bodies that are continuously formed adjacent to each other so as to have a lap portion, when there are obstacles such as large gravel in the ground, The present invention can be carried out without any trouble even when the ground is made of a plurality of different layers or ultra-soft soil, or when there are private houses around the ground improvement body.
本発明の地盤改良体の径の推定方法の対象物は、高圧噴射撹拌工法によって、酸化カルシウムを主成分とするセメント系固化材を含むスラリーを地中に噴射して形成される、水平方向の断面が略円形である円柱状の地盤改良体である。
改良前の地盤としては、例えば、軟弱粘性土、緩い砂質土等が挙げられる。
高圧噴射撹拌工法の種類としては、（ａ）超高圧の固化材スラリーを噴射する一相流方式の工法、（ｂ）前記（ａ）の工法よりも大きな径の地盤改良体を造成する目的で、超高圧の固化材スラリー噴流の周りに空気を沿わせた二相流方式の工法、（ｃ）超高圧水の周りに空気を沿わせて切削拡径し、固化材スラリーを填充して地盤改良体を造成する三相流方式、がある。
本発明は、これら（ａ）〜（ｃ）のいずれの工法に対しても適用することができる。中でも、前記（ａ）の一相流方式の高圧噴射撹拌工法は、ある程度の土被りがあれば、セメント系固化材を含むスライムが地表に排出されず、本発明の原理を好適に適用することができること、及び、地盤改良体の径（以下、「造成径」ともいう。）が比較的小さく、径の確認が困難とされていることから、本発明を適用する工法として特に好ましいものである。
The object of the method for estimating the diameter of the ground improvement body of the present invention is formed by injecting a slurry containing a cement-based solidified material mainly composed of calcium oxide into the ground by a high-pressure jet stirring method. It is a cylindrical ground improvement body having a substantially circular cross section.
Examples of the ground before the improvement include soft viscous soil, loose sandy soil, and the like.
The types of the high-pressure jet agitation method include (a) a one-phase flow method for injecting a super-high-pressure solidified slurry, and (b) for the purpose of creating a ground improvement body having a larger diameter than the method (a). , Two-phase flow method with air around the ultra-high pressure solidified slurry slurry jet, (c) Ground expansion by filling the solid slurry with air along the ultra-high pressure water There is a three-phase flow method, which creates an improved body.
The present invention can be applied to any of these methods (a) to (c). Among them, the high pressure jet agitation method of the one-phase flow method (a) described above preferably applies the principle of the present invention without slime containing cement-based solidifying material being discharged to the ground surface if there is a certain amount of earth covering. It is particularly preferable as a construction method to which the present invention is applied because the diameter of the ground improvement body (hereinafter also referred to as “reconstructed diameter”) is relatively small and it is difficult to confirm the diameter. .
本発明の地盤改良体の径の推定方法の原理は、次のとおりである。
高圧噴射撹拌工法によって、酸化カルシウムを主成分とするセメント系固化材を含むスラリーを土中に噴射すると、該スラリーと既存の固化対象土（原土）が均一に混合された、水平方向の断面が略円形である円柱状の地盤改良体が形成される。この地盤改良体の中には、原土に由来する酸化カルシウム、及び土中に噴射したスラリー中のセメント系固化材に由来する酸化カルシウムが含まれている。
この地盤改良体の内部から採取した少量の土（改良土の試料）に過剰の塩酸（ＨＣｌ）を加えて、酸性のスラリーを得た後、この酸性のスラリーに水酸化ナトリウム（ＮａＯＨ）溶液を加えて、中和滴定を行なうと、中和に要した水酸化ナトリウムの量から、改良土の試料中の酸化カルシウム（ＣａＯ）の量が特定される。
これらの操作における化学反応式（ａ）〜（ｂ）、及び、改良土の試料中の酸化カルシウム量の計算式（ｃ）を、下記に示す。
（ａ） ＣａＯ（改良土の試料）＋２ＨＣｌ → ＣａＣｌ2＋ Ｈ2Ｏ
（ｂ） ＨＣｌ（残余） ＋ ＮａＯＨ → ＮａＣｌ ＋ Ｈ2Ｏ
（ｃ）［改良土の試料中のＣａＯ量］＝［ＨＣｌの総量］−［ＮａＯＨの使用量］
The principle of the method for estimating the diameter of the ground improvement body of the present invention is as follows.
When a slurry containing cement-based solidified material mainly composed of calcium oxide is sprayed into the soil by the high-pressure spray agitation method, the slurry and the existing solidified soil (raw soil) are uniformly mixed, and the horizontal cross section A cylindrical ground improvement body having a substantially circular shape is formed. This ground improvement body contains calcium oxide derived from the raw soil and calcium oxide derived from the cement-based solidified material in the slurry injected into the soil.
Excess hydrochloric acid (HCl) was added to a small amount of soil (sample of improved soil) collected from the inside of this ground improvement body to obtain an acidic slurry, and then sodium hydroxide (NaOH) solution was added to the acidic slurry. In addition, when neutralization titration is performed, the amount of calcium oxide (CaO) in the sample of the improved soil is specified from the amount of sodium hydroxide required for neutralization.
The chemical reaction formulas (a) to (b) in these operations and the calculation formula (c) of the amount of calcium oxide in the sample of the improved soil are shown below.
(A) CaO (modified soil sample) + 2HCl → CaCl 2 + H 2 O
(B) HCl (residue) + NaOH → NaCl + H 2 O
(C) [CaO amount in sample of improved soil] = [total amount of HCl] − [amount of NaOH used]
前記の計算式（ｃ）で示される酸化カルシウム（ＣａＯ）量に基づいて、円柱状の地盤改良体の体積（Ｌ×πＤ2／４；式中、Ｌは、地盤改良体の軸線方向の長さを示し、Ｄは、地盤改良体の未知の径を示す。）中の酸化カルシウムの総量を想定した場合、この酸化カルシウムの総量から、原土に含まれていた既存の酸化カルシウム量を差し引いた量は、噴射したスラリー中のセメント系固化材に由来する酸化カルシウムの総量に等しい。
一般に、噴射したスラリーの総量が一定であれば、改良土の酸化カルシウム含有率が大きくなるほど、地盤改良体の造成径が小さくなるという関係が成立する。この関係を図１に概念的に示す。
本発明は、この関係を利用して、地盤改良体の造成径（Ｄ）を推定するものである。
なお、前記の（ｂ）の化学反応式における中和滴定の方法の一例としては、ＫＯＤＡＮ２０７法（日本道路公団規格：セメントおよび石灰安定処理混合物のセメントおよび石灰量試験方法，ＪＨＳ ２０７−１９９２）中の「滴定法によるセメント安定処理混合物のセメント量試験方法」において、３Ｎの塩酸に代えて、６Ｎの塩酸を用いる方法が挙げられる。なお、６Ｎの塩酸を使用する理由は、３Ｎの塩酸では、使用量及び溶解時間の増大によって作業効率が低下するからである。
Based on the amount of calcium oxide (CaO) represented by the formula (c), a cylindrical volume of the soil improvement material (L × πD 2/4; wherein, L is the axial direction of the soil improvement material length D indicates the unknown diameter of the ground improvement body.) When the total amount of calcium oxide in the ground is assumed, the existing amount of calcium oxide contained in the raw soil is subtracted from the total amount of calcium oxide. This amount is equal to the total amount of calcium oxide derived from the cementitious solidified material in the sprayed slurry.
In general, if the total amount of the injected slurry is constant, the relationship that the formation diameter of the ground improvement body decreases as the calcium oxide content of the improved soil increases. This relationship is conceptually shown in FIG.
The present invention uses this relationship to estimate the formation diameter (D) of the ground improvement body.
In addition, as an example of the neutralization titration method in the chemical reaction formula (b), the KODAN207 method (Japan Highway Public Corporation Standard: Cement and lime stability test method for cement and lime stable treatment mixture, JHS 207-1992) In “Method for testing cement amount of cement stabilized treatment mixture by titration method”, a method using 6N hydrochloric acid instead of 3N hydrochloric acid can be mentioned. The reason why 6N hydrochloric acid is used is that the working efficiency of 3N hydrochloric acid decreases due to an increase in the amount used and dissolution time.
本発明の地盤改良体の径の推定方法の実施形態としては、（Ａ）検量線を用いる方法、及び（Ｂ）計算式を用いる方法、が挙げられる。以下、これらの実施形態の各々について、詳しく説明する。
（Ａ）検量線を用いる方法
検量線を用いる方法は、（ａ）地盤改良体の改良前の土（原土）の一部を採取し、該採取した原土とセメント系固化材を、少なくとも３つの異なる配合割合で混合して、少なくとも３種の検量線作成用試料を調製する試料調製工程と、（ｂ）得られた検量線作成用試料の各々について、酸化カルシウム含有率を測定する試料測定工程と、（ｃ）試料測定工程で得られた酸化カルシウム含有率と、前記の検量線作成用試料の各々について算出した地盤改良体の径の理論値との関係曲線である検量線を作成する検量線作成工程と、（ｄ）地盤改良体の土の一部（改良土の試料）を採取し、該採取した改良土の試料の酸化カルシウム含有率を測定する改良土測定工程と、（ｅ）改良土測定工程で得られた酸化カルシウム含有率を、前記工程（ｃ）で作成済みの検量線に適用して、地盤改良体の径の推定値を得る推定値決定工程を含むものである。
Examples of the method for estimating the diameter of the ground improvement body of the present invention include (A) a method using a calibration curve and (B) a method using a calculation formula. Hereinafter, each of these embodiments will be described in detail.
(A) Method using a calibration curve The method using a calibration curve is as follows: (a) a part of soil (raw soil) before improvement of the ground improvement body is sampled, and the collected raw soil and cement-based solidified material are at least A sample preparation step for preparing at least three types of calibration curve preparation samples by mixing at three different blending ratios, and (b) a sample for measuring the calcium oxide content rate for each of the obtained calibration curve preparation samples. Create a calibration curve that is a relationship curve between the measurement step, (c) the calcium oxide content obtained in the sample measurement step, and the theoretical value of the diameter of the ground improvement body calculated for each of the calibration curve creation samples. A calibration curve creation step, (d) an improved soil measurement step in which a portion of the soil of the ground improvement body (sample of improved soil) is collected, and the calcium oxide content of the sample of improved soil collected is measured ( e) Containing calcium oxide obtained in the improved soil measurement process An estimated value determining step of obtaining an estimated value of the diameter of the ground improvement body by applying the probability to the calibration curve created in the step (c) is included.
［工程（ａ）；試料調製工程］
本工程は、原土の一部を採取し、該採取した原土とセメント系固化材を、少なくとも３つの異なる配合割合で混合して、少なくとも３種の検量線作成用試料を調製する工程である。
原土は、改良対象土の内部にてボーリングにより採取する。採取した原土は、湿潤密度及び含水比を測定した後、四分法等で縮分、混合し、代表試料とする。この代表試料を１１０℃で恒量になるまで乾燥した後、乳鉢等を用いて、１０５μｍ篩全通程度にまで粉砕し、再度、四分法等で縮分し、試験用試料とする。
地盤改良体の径として少なくとも３つの径を想定する。想定する径の数は、好ましくは３〜８、より好ましくは４〜５である。該値が２未満では、正確な検量線を作成することが困難である。該値が８を超えると、検量線の作成の労力が多大となる。
想定する少なくとも３つの径の各々について、想定する径に相当する所定の配合割合で、試験用試料とセメント系固化材を混合し、少なくとも３種の検量線作成用試料を調製する。
[Step (a); Sample preparation step]
In this step, a part of the raw soil is sampled, and the collected raw soil and cement-based solidified material are mixed in at least three different blending ratios to prepare at least three types of calibration curve preparation samples. is there.
The raw soil is collected by boring inside the soil to be improved. The collected raw soil is measured for wet density and moisture content, and then reduced and mixed by the quadrant method or the like to obtain a representative sample. This representative sample is dried to a constant weight at 110 ° C., then pulverized to about 105 μm sieve using a mortar or the like, and again reduced to a test sample by a quartering method or the like.
At least three diameters are assumed as the diameter of the ground improvement body. The number of assumed diameters is preferably 3-8, more preferably 4-5. If the value is less than 2, it is difficult to create an accurate calibration curve. When the value exceeds 8, labor for creating a calibration curve becomes great.
For each of at least three assumed diameters, the test sample and the cement-based solidifying material are mixed at a predetermined blending ratio corresponding to the assumed diameter to prepare at least three types of calibration curve preparation samples.
［工程（ｂ）；試料測定工程］
本工程は、工程（ａ）で得られた少なくとも３種の検量線作成用試料の各々について、酸化カルシウム含有率を測定する工程である。
酸化カルシウム含有率の測定方法の一例は、次のとおりである。
まず、３００ミリリットルのビーカーに、検量線作成用試料５〜１５ｇを収容する。次いで、１００ミリリットルの水を加えて、ガラス棒で撹拌し、スラリーとする。このスラリーに、６Ｎの塩酸を過剰量（１０〜３０ミリリットル）加えて、撹拌する。なお、塩酸の使用量は、次式を満たすように定めればよい。
［塩酸の使用量（ｍＬ）］ ≧ ［試料中のセメント系固化材の質量（ｇ）］×１０
１０分間経過後、ビーカーをマグネプトスターラー台に載せ、ビーカー内のスラリーを撹拌しながら、２Ｎの水酸化ナトリウム水溶液を滴下していき、スラリーのｐＨが７．０になった時点における水酸化ナトリウム水溶液の使用量を測定する。測定後、次式に基づいて、試料中の酸化カルシウム含有率（質量％）を算出する。
［試料中のＣａＯ量］＝［塩酸の使用量］−［水酸化ナトリウムの使用量］
[Step (b); Sample measurement step]
This step is a step of measuring the calcium oxide content rate for each of at least three types of calibration curve preparation samples obtained in step (a).
An example of a method for measuring the calcium oxide content rate is as follows.
First, 5 to 15 g of a calibration curve preparation sample is accommodated in a 300 ml beaker. Next, 100 milliliters of water is added and stirred with a glass rod to form a slurry. To this slurry, an excess amount of 6N hydrochloric acid (10-30 ml) is added and stirred. In addition, what is necessary is just to determine the usage-amount of hydrochloric acid so that following Formula may be satisfy | filled.
[Amount of hydrochloric acid used (mL)] ≧ [Mass of cement-based solidified material in sample (g)] × 10
After 10 minutes, the beaker was placed on a magneto stirrer stand, and while stirring the slurry in the beaker, 2N sodium hydroxide aqueous solution was added dropwise, and the sodium hydroxide at the time when the pH of the slurry reached 7.0. Measure the amount of aqueous solution used. After the measurement, the calcium oxide content (mass%) in the sample is calculated based on the following formula.
[CaO amount in sample] = [Amount of hydrochloric acid used] − [Amount of sodium hydroxide used]
［工程（ｃ）；検量線作成工程］
本工程は、工程（ｂ）で得られた酸化カルシウム含有率と、工程（ａ）で調製した検量線作成用試料の各々について算出した地盤改良体の径の理論値との関係曲線である検量線を作成する工程である。
検量線は、酸化カルシウム含有率を横軸とし、地盤改良体の径の理論値を縦軸として作成される。
地盤改良体の径の理論値は、次の式（１）によって算出される。
なお、施工に用いる高圧噴射撹拌装置の種類によっては、円柱状の地盤改良体の内部にその軸線を中心とする棒状の未改良部が形成されることがある。この場合、未改良部の径の大きさ（例えば、０．３ｍ）に応じて、次の式（２）によって、地盤改良体の径の理論値（Ｄ）を補正する。
[Step (c); calibration curve creation step]
This step is a calibration curve that is a relation curve between the calcium oxide content obtained in step (b) and the theoretical value of the diameter of the ground improvement body calculated for each of the calibration curve preparation samples prepared in step (a). This is a process of creating a line.
The calibration curve is created with the calcium oxide content rate as the horizontal axis and the theoretical value of the diameter of the ground improvement body as the vertical axis.
The theoretical value of the diameter of the ground improvement body is calculated by the following equation (1).
In addition, depending on the kind of high-pressure jet stirring apparatus used for construction, a rod-shaped unimproved portion centering on the axis may be formed inside the cylindrical ground improvement body. In this case, the theoretical value (D) of the diameter of the ground improvement body is corrected by the following formula (2) according to the size of the diameter of the unimproved portion (for example, 0.3 m).
［工程（ｄ）；改良土測定工程］
本工程は、地盤改良体の土の一部（改良土の試料）を採取し、該採取した改良土の試料の酸化カルシウム含有率を測定する工程である。
改良土の試料は、地盤改良体の内部にてボーリングにより採取する。本発明では、従来と異なり、地盤改良体の外縁でボーリングする必要がなく、地盤改良体の内部の任意の地点で試料を採取すればよい。
採取した改良土の試料について酸化カルシウム含有率を測定する方法は、上述の工程（ｂ）（試料測定工程）における塩酸及び水酸化ナトリウムを用いた中和滴定による測定方法と同様である。
［工程（ｅ）；推定値決定工程］
本工程は、工程（ｄ）（改良土測定工程）で得られた酸化カルシウム含有率を、工程（ｃ）で作成済みの検量線に適用して、地盤改良体の径の推定値を得る工程である。
具体的には、改良土の酸化カルシウム含有率を、検量線の横軸の目盛りで特定した後、この目盛りに対応する検量線（曲線）上の点を特定し、この点の縦軸の目盛りを読み取って、地盤改良体の径の推定値とする。
[Step (d): Improved soil measurement step]
This step is a step of collecting a part of the soil of the ground improvement body (sample of improved soil) and measuring the calcium oxide content rate of the sample of improved soil collected.
Samples of the improved soil are collected by boring inside the ground improvement body. In the present invention, unlike the conventional case, it is not necessary to perform boring at the outer edge of the ground improvement body, and a sample may be collected at an arbitrary point inside the ground improvement body.
The method for measuring the calcium oxide content of the collected sample of improved soil is the same as the measurement method by neutralization titration using hydrochloric acid and sodium hydroxide in the above-described step (b) (sample measurement step).
[Step (e); Estimated Value Determination Step]
In this step, the calcium oxide content obtained in step (d) (improved soil measurement step) is applied to the calibration curve created in step (c) to obtain an estimated value of the diameter of the ground improvement body. It is.
Specifically, after specifying the calcium oxide content of the improved soil on the scale on the horizontal axis of the calibration curve, the point on the calibration curve (curve) corresponding to this scale is identified, and the scale on the vertical axis of this point Is taken as the estimated value of the diameter of the ground improvement body.
（Ｂ）計算式を用いる方法
計算式を用いる方法は、（ａ）地盤改良体の改良前の土（原土）の一部を採取し、該採取した原土の酸化カルシウム含有率を測定する原土測定工程と、（ｂ）地盤改良体の土（改良土）の一部を採取し、該採取した改良土の酸化カルシウム含有率を測定する改良土測定工程と、（ｃ）工程（ａ）で得られた原土の酸化カルシウム含有率と、工程（ｂ）で得られた改良土の酸化カルシウム含有率と、セメント系固化材の既知の酸化カルシウム含有率とに基づいて、地盤改良体の径の推定値を得る推定値決定工程を含むものである。
［工程（ａ）；原土測定工程］
本工程は、原土の一部を採取し、該採取した原土の酸化カルシウム含有率を測定する工程である。
原土の酸化カルシウム含有率の測定方法は、上述の「（Ａ）検量線を用いる方法」中の工程（ｂ）（試料測定工程）における塩酸及び水酸化ナトリウムを用いた中和滴定による測定方法と同様である。
［工程（ｂ）；改良土測定工程］
本工程は、改良土の一部を採取し、該採取した改良土の酸化カルシウム含有率を測定する工程である。
改良土の酸化カルシウム含有率の測定方法は、上述の「（Ａ）検量線を用いる方法」中の工程（ｂ）（試料測定工程）における塩酸及び水酸化ナトリウムを用いた中和滴定による測定方法と同様である。
(B) Method using calculation formula The method using the calculation formula is as follows: (a) A part of soil (raw soil) before improvement of the ground improvement body is sampled, and the calcium oxide content rate of the sampled raw soil is measured Raw soil measurement step, (b) improved soil measurement step in which a portion of the soil of the ground improvement body (improved soil) is collected, and the calcium oxide content of the collected improved soil is measured, and (c) step (a ) Based on the calcium oxide content of the raw soil obtained in step (b), the calcium oxide content of the improved soil obtained in step (b), and the known calcium oxide content of the cement-based solidified material. This includes an estimated value determining step for obtaining an estimated value of the diameter.
[Step (a): Raw soil measurement step]
This step is a step of collecting a part of the raw soil and measuring the calcium oxide content of the collected raw soil.
The measurement method of the calcium oxide content of the raw soil is a measurement method by neutralization titration using hydrochloric acid and sodium hydroxide in step (b) (sample measurement step) in the above-mentioned “(A) Method using calibration curve”. It is the same.
[Step (b): Improved soil measurement step]
In this step, a part of the improved soil is sampled and the calcium oxide content of the sampled improved soil is measured.
The measurement method of the calcium oxide content of the improved soil is a measurement method by neutralization titration using hydrochloric acid and sodium hydroxide in step (b) (sample measurement step) in the above-mentioned “(A) Method using calibration curve”. It is the same.
［工程（ｃ）；推定値決定工程］
本工程は、工程（ａ）で得られた原土の酸化カルシウム含有率と、工程（ｂ）で得られた改良土の酸化カルシウム含有率と、セメント系固化材の既知の酸化カルシウム含有率とに基づいて、地盤改良体の径の推定値を得る工程である。
セメント系固化材の酸化カルシウム含有率が不明な場合、上述の「（Ａ）検量線を用いる方法」中の工程（ｂ）（試料測定工程）における塩酸及び水酸化ナトリウムを用いた中和滴定による測定方法と同様にして、セメント系固化材の酸化カルシウム含有率を測定し、この測定値を本工程における既知の値として用いる。
本工程において、地盤改良体の径の推定値は、次のように算出することができる。
まず、地盤改良体の酸化カルシウム含有量は、原土の酸化カルシウム含有量と、セメント系固化材を含むスラリーの酸化カルシウム含有量の和に等しく、次の式で表される。
［地盤改良体の酸化カルシウム含有量：M’CaO］＝［原土の酸化カルシウム含有量：MsCaO］＋［スラリーの酸化カルシウム含有量：MmCaO］
[Step (c); Estimated Value Determination Step]
In this step, the calcium oxide content of the raw soil obtained in step (a), the calcium oxide content of the improved soil obtained in step (b), and the known calcium oxide content of the cement-based solidified material Is a step of obtaining an estimated value of the diameter of the ground improvement body based on the above.
When the calcium oxide content of the cement-based solidified material is unknown, neutralization titration using hydrochloric acid and sodium hydroxide in step (b) (sample measurement step) in the above-mentioned “(A) Method using calibration curve” In the same manner as the measurement method, the calcium oxide content of the cement-based solidified material is measured, and this measured value is used as a known value in this step.
In this step, the estimated value of the diameter of the ground improvement body can be calculated as follows.
First, the calcium oxide content of the ground improvement body is equal to the sum of the calcium oxide content of the raw soil and the calcium oxide content of the slurry containing the cement-based solidified material, and is expressed by the following equation.
[Calcium oxide content of the soil improvement material: M 'CaO] = [calcium oxide content of the raw soil: M sCaO] + [calcium oxide content of the slurry: M MCAO]
この式において、地盤改良体の酸化カルシウム含有含有量（M’CaO）、原土の酸化カルシウム含有量（MsCaO）、及び、スラリーの酸化カルシウム含有量（MmCaO）は、各々、次の式（３）〜（５）で表される。
前記の式（３）〜（５）から、次の式（６）が導かれる。式（６）によって、地盤改良体の径の推定値（Ｄ）を得ることができる。
［１．高圧噴射撹拌工法の噴射方式］
噴射方式として、一相流方式の高圧噴射撹拌工法を用いた。
浅層部の施工仕様として、噴射圧力２０ＭＰａの工法（以下、「Ｊ−２０工法」ともいう。）及び噴射圧力４０ＭＰａの工法（以下、「Ｊ−４０工法」ともいう。）を採用し、深層部の施工仕様として、噴射圧力４０ＭＰａの工法（Ｊ−４０工法）を採用した。これらの施工仕様の詳細を表１に示す。
As the injection method, a one-phase flow type high-pressure injection stirring method was used.
As construction specifications for the shallow layer portion, a construction method with an injection pressure of 20 MPa (hereinafter also referred to as “J-20 construction method”) and a construction method with an injection pressure of 40 MPa (hereinafter also referred to as “J-40 construction method”) are adopted. As a construction specification of the part, a construction method (J-40 construction method) with an injection pressure of 40 MPa was adopted. Details of these construction specifications are shown in Table 1.
［２．原土及びセメント系固化材の性状］
浅層部の改良領域として、深度が１．５〜４．５ｍの領域を対象とした。深層部の改良領域として、深度が１６．０〜２１．０ｍの領域を対象とした。浅層部及び深層部の各々の原土の性状を表２に示す。
浅層部及び深層部の各々について、表２に示す性状の固化材Ａ、Ｂを用いた。
As an improvement region of the shallow layer portion, a region having a depth of 1.5 to 4.5 m was targeted. As an improved region of the deep layer portion, a region having a depth of 16.0 to 21.0 m was targeted. Table 2 shows the properties of the raw soil in the shallow and deep layers.
For each of the shallow layer portion and the deep layer portion, solidified materials A and B having the properties shown in Table 2 were used.
［３．検量線を用いる方法］
（１）浅層部の検量線作成のための滴定分析
表３に示す量の乾燥原土及びセメント系固化材を混合して、試料「Ａ−１」〜「Ａ−４」を調製した。表３中の「固化材の換算添加量」は、地盤改良体１ｍ3中の固化材の質量（ｋｇ）を示す。
(1) Titration analysis for preparation of calibration curve of shallow layer portion Samples “A-1” to “A-4” were prepared by mixing the amounts of dry raw soil and cement-based solidifying material in amounts shown in Table 3. “Conversion addition amount of solidified material” in Table 3 indicates the mass (kg) of the solidified material in 1 m 3 of the ground improvement body.
試料「Ａ−１」〜「Ａ−４」に対して、６Ｎの塩酸を過剰量（１０．０ミリリットル）加えて、酸性のスラリーを得た後、この酸性のスラリーに２Ｎの水酸化ナトリウムを徐々に添加して中和滴定し、中和に要した水酸化ナトリウム量を測定した。測定結果を表４に示す。
塩酸及び水酸化ナトリウムの使用量に基づいて、試料（乾燥状態）中の酸化カルシウム含有率（質量％）を算出した。算出方法は、次の式（７）による。算出値を表４に示す。
Based on the usage-amounts of hydrochloric acid and sodium hydroxide, the calcium oxide content rate (mass%) in a sample (dry state) was computed. The calculation method is based on the following equation (7). Table 4 shows the calculated values.
また、地盤改良体の径の理論値（想定造成径）を、上述の式（１）によって算出した。算出値を表４に示す。
さらに、表４に示すＣａＯ含有率及び想定造成径に基づいて、図２に示す浅層部の検量線のグラフを作成した。
Furthermore, based on the CaO content and the assumed formation diameter shown in Table 4, a graph of the calibration curve of the shallow layer shown in FIG. 2 was created.
（２）深層部の検量線作成のための滴定分析
表５に示す量の乾燥原土及びセメント系固化材を混合して、試料「Ｂ−１」〜「Ｂ−５」を調製した。表５中の「固化材の換算添加量」は、地盤改良体１ｍ3中の固化材の質量（ｋｇ）を示す。
試料「Ｂ−１」〜「Ｂ−５」に対して、６Ｎの塩酸を過剰量（表６参照）加えて、酸性のスラリーを得た後、この酸性のスラリーに２Ｎの水酸化ナトリウムを徐々に添加して中和滴定し、中和に要した水酸化ナトリウム量を測定した。測定結果を表６に示す。
塩酸及び水酸化ナトリウムの使用量に基づいて、試料（乾燥状態）中の酸化カルシウム含有率（質量％）を算出した。算出方法は、上述の式（７）による。算出値を表６に示す。
また、地盤改良体の径の理論値（想定造成径）を、上述の式（１）によって算出した。算出値を表６に示す。
さらに、表６に示すＣａＯ含有率及び想定造成径に基づいて、図３に示す深層部の検量線のグラフを作成した。
Based on the usage-amounts of hydrochloric acid and sodium hydroxide, the calcium oxide content rate (mass%) in a sample (dry state) was computed. The calculation method is based on the above equation (7). Table 6 shows the calculated values.
Moreover, the theoretical value (assumed creation diameter) of the ground improvement body was calculated by the above-mentioned formula (1). Table 6 shows the calculated values.
Furthermore, based on the CaO content and the assumed formation diameter shown in Table 6, a graph of the calibration curve of the deep layer shown in FIG. 3 was created.
（３）実施例１
Ｊ−２０の工法を用いて、浅層部の地盤改良体を造成した後、この地盤改良体の内部からボーリングによって改良土の試料（質量：２０．０００ｇ）を採取した。この試料に、６Ｎの塩酸を２０．０ミリリットル加えて混合し、酸性のスラリーを得た後、このスラリーに対して、ｐＨが７．０になるまで２Ｎの水酸化ナトリウム水溶液を滴下した。中和に要した水酸化ナトリウムの使用量から、試料中の酸化カルシウム含有率（質量％）を算出した。この算出値を図１に示す浅層部用の検量線に適用して、地盤改良体の径の推定値（推定径）を得た。
一方、地表面から３．５ｍの深さまで掘削して、地盤改良体の径の実測値（実測径）を得た。
（４）実施例２〜７
地盤改良体の浅層・深層の別、工法、及び造成地点を変えて、実施例１と同様に実験した。なお、深層部の実測径は、パイロット孔の削孔及びサウンディングによる測定方法で得た。
以上の結果を表７に示す。表７から、推定径と実測径の差は１〜４ｃｍであり、検量線を用いた造成径の推定方法は、極めて高い精度を有することがわかる。
(3) Example 1
After constructing a shallow ground improvement body using the method of J-20, a sample of improved soil (mass: 20.000 g) was collected from the inside of the ground improvement body by boring. To this sample, 20.0 ml of 6N hydrochloric acid was added and mixed to obtain an acidic slurry, and then a 2N aqueous sodium hydroxide solution was added dropwise to the slurry until the pH reached 7.0. From the amount of sodium hydroxide used for neutralization, the calcium oxide content (mass%) in the sample was calculated. This calculated value was applied to the calibration curve for the shallow layer shown in FIG. 1 to obtain an estimated value (estimated diameter) of the diameter of the ground improvement body.
On the other hand, it excavated to the depth of 3.5 m from the ground surface, and the measured value (measured diameter) of the diameter of the ground improvement body was obtained.
(4) Examples 2-7
Experiments were conducted in the same manner as in Example 1 by changing the shallow and deep layers of the ground improvement body, the construction method, and the creation point. The measured diameter of the deep layer was obtained by a measurement method using pilot hole drilling and sounding.
The results are shown in Table 7. From Table 7, it can be seen that the difference between the estimated diameter and the actually measured diameter is 1 to 4 cm, and the method for estimating the formed diameter using the calibration curve has extremely high accuracy.
［４．計算式を用いる方法］
（１）原土及びセメント系固化材の酸化カルシウム含有率の測定
表８に示すように、原土（浅層、深層）及びセメント系固化材（固化材Ａ、固化材Ｂ）の各々の試料に対して、６Ｎの塩酸を過剰量加えて、酸性のスラリーを得た後、この酸性のスラリーに２Ｎの水酸化ナトリウムを徐々に添加して中和滴定し、中和に要した水酸化ナトリウム量を測定した。測定結果を表８に示す。
塩酸及び水酸化ナトリウムの使用量に基づいて、試料（乾燥状態）中の酸化カルシウム含有率（質量％）を算出した。算出方法は、上述の式（７）による。算出値を表８に示す。
[4. Method using formula]
(1) Measurement of calcium oxide content of raw soil and cement-based solidified material As shown in Table 8, each sample of raw soil (shallow layer, deep layer) and cement-based solidified material (solidified material A, solidified material B) On the other hand, an excess amount of 6N hydrochloric acid was added to obtain an acidic slurry, and then 2N sodium hydroxide was gradually added to the acidic slurry, followed by neutralization titration, and sodium hydroxide required for neutralization. The amount was measured. Table 8 shows the measurement results.
Based on the usage-amounts of hydrochloric acid and sodium hydroxide, the calcium oxide content rate (mass%) in a sample (dry state) was computed. The calculation method is based on the above equation (7). Table 8 shows the calculated values.
（２）実施例８〜１４
実施例１〜７で得られた改良土の酸化カルシウム含有率と、表８に示す原土の酸化カルシウム含有率と、表８に示す固化材の酸化カルシウム含有率とを、上述の式（６）に加入することによって、計算式による地盤改良体の推定径を算出した。算出値を表９に示す。表９から、推定径と実測径の差は１〜６ｃｍであり、計算式を用いた造成径の推定方法は、非常に高い精度を有することがわかる。
The calcium oxide content rate of the improved soil obtained in Examples 1 to 7, the calcium oxide content rate of the raw soil shown in Table 8, and the calcium oxide content rate of the solidified material shown in Table 8 are expressed by the above formula (6 ), The estimated diameter of the ground improvement body was calculated by the formula. Table 9 shows the calculated values. From Table 9, it can be seen that the difference between the estimated diameter and the actually measured diameter is 1 to 6 cm, and the formation diameter estimation method using the calculation formula has very high accuracy.
Claims (3)
上記地盤改良体の酸化カルシウム含有率が大きいほど、上記地盤改良体の径が小さいという関係を利用して、上記地盤改良体の酸化カルシウム含有率の測定値に基づいて、上記地盤改良体の径を推定することを特徴とする地盤改良体の径の推定方法。 In the ground improvement work in which a slurry containing a cement-based solidified material mainly composed of calcium oxide is injected into the ground by a high-pressure jet stirring method, and a cylindrical ground improvement body having a substantially circular cross section in the horizontal direction is formed. A method for estimating the diameter of the ground improvement body,
Based on the measured value of the calcium oxide content of the ground improvement body, using the relationship that the larger the calcium oxide content of the ground improvement body, the smaller the diameter of the ground improvement body, the diameter of the ground improvement body A method for estimating the diameter of a ground improvement body, characterized in that
上記少なくとも３種の検量線作成用試料の各々について、酸化カルシウム含有率を測定する試料測定工程と、
上記試料測定工程で得られた酸化カルシウム含有率と、上記少なくとも３種の検量線作成用試料の各々について算出した地盤改良体の径の理論値との関係曲線である検量線を作成する検量線作成工程と、
上記地盤改良体の土の一部を採取し、該採取した土の酸化カルシウム含有率を測定する改良土測定工程と、
上記改良土測定工程で得られた酸化カルシウム含有率を、上記検量線に適用して、上記地盤改良体の径の推定値を得る推定値決定工程を含む請求項１に記載の地盤改良体の径の推定方法。 A portion of the soil before improvement of the ground improvement body is collected, and the collected soil and the cement-based solidified material are mixed at at least three different blending ratios to prepare at least three types of calibration curve preparation samples. A sample preparation process,
A sample measurement step for measuring the calcium oxide content for each of the at least three types of calibration curve preparation samples;
A calibration curve that creates a calibration curve that is a relationship curve between the calcium oxide content obtained in the sample measurement step and the theoretical value of the diameter of the ground improvement body calculated for each of the at least three types of calibration curve creation samples. Creation process,
A part of the soil of the ground improvement body is collected, and the improved soil measurement step of measuring the calcium oxide content of the collected soil,
The calcium oxide content obtained in the improved soil measurement step is applied to the calibration curve to include an estimated value determining step for obtaining an estimated value of the diameter of the ground improved body. Diameter estimation method.
上記地盤改良体の土の一部を採取し、該採取した土の酸化カルシウム含有率を測定する改良土測定工程と、
上記原土測定工程で得られた酸化カルシウム含有率と、上記改良土測定工程で得られた酸化カルシウム含有率と、上記セメント系固化材の既知の酸化カルシウム含有率とに基づいて、上記地盤改良体の径の推定値を得る推定値決定工程を含む請求項１に記載の地盤改良体の径の推定方法。
A part of the soil before improvement of the ground improvement body is collected, and the raw soil measurement step of measuring the calcium oxide content of the collected soil,
A part of the soil of the ground improvement body is collected, and the improved soil measurement step of measuring the calcium oxide content of the collected soil,
Based on the calcium oxide content obtained in the raw soil measurement step, the calcium oxide content obtained in the improved soil measurement step, and the known calcium oxide content of the cement-based solidified material, the ground improvement The estimation method of the diameter of the ground improvement body of Claim 1 including the estimated value determination process of obtaining the estimated value of the diameter of a body.
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| JP2015081436A (en) * | 2013-10-22 | 2015-04-27 | 大成建設株式会社 | Ground improvement body structure |
| JP2019157551A (en) * | 2018-03-15 | 2019-09-19 | ケミカルグラウト株式会社 | Quality management system of ground improvement body, and ground improvement method |
| JP2021161720A (en) * | 2020-03-31 | 2021-10-11 | 小野田ケミコ株式会社 | Quality prediction method and quality control method of improvement body |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| JP2015081436A (en) * | 2013-10-22 | 2015-04-27 | 大成建設株式会社 | Ground improvement body structure |
| JP2019157551A (en) * | 2018-03-15 | 2019-09-19 | ケミカルグラウト株式会社 | Quality management system of ground improvement body, and ground improvement method |
| JP7112820B2 (en) | 2018-03-15 | 2022-08-04 | ケミカルグラウト株式会社 | SOIL IMPROVEMENT SYSTEM AND QUALITY CONTROL METHOD |
| JP2021161720A (en) * | 2020-03-31 | 2021-10-11 | 小野田ケミコ株式会社 | Quality prediction method and quality control method of improvement body |
| JP7356947B2 (en) | 2020-03-31 | 2023-10-05 | 小野田ケミコ株式会社 | Quality prediction method and quality control method of improved product |
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