JP2714873B2 - Prevention of swelling by decompression method - Google Patents
Prevention of swelling by decompression methodInfo
- Publication number
- JP2714873B2 JP2714873B2 JP13589090A JP13589090A JP2714873B2 JP 2714873 B2 JP2714873 B2 JP 2714873B2 JP 13589090 A JP13589090 A JP 13589090A JP 13589090 A JP13589090 A JP 13589090A JP 2714873 B2 JP2714873 B2 JP 2714873B2
- Authority
- JP
- Japan
- Prior art keywords
- pressure
- swelling
- drainage
- pressurized water
- prevention
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Fee Related
Links
Landscapes
- Investigation Of Foundation Soil And Reinforcement Of Foundation Soil By Compacting Or Drainage (AREA)
Description
【発明の詳細な説明】 産業上の利用分野 この発明は、地盤の掘削工法において実施される、被
圧水圧の減圧方式による盤ぶくれ防止工法に関する。Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for preventing swelling by a method of reducing a pressure to be applied, which is carried out in a method of excavating a ground.
従来の技術 従来、第３図のように高い被圧水圧Ｕを持つ地盤を深
く掘削する場合には、土圧の減少とのアンバランスによ
って根切り底に所謂盤ぶくれ（根切り底の盛り上り崩
壊）を生ずるおそれが多分にある。即ち、土被り重量の
大きさをＷとし、被圧水圧の大きさをＵとすると、Ｗ＝
1.2（h.γｔ）、但し、ｈは土被り、γｔは土の単位重
量である。また、Ｕ＝Ｈ・γｗ、但し、Ｈは被圧水頭
で、γｗを水の単位重量とすると、ＷとＵの関係が1.2
（h.γｔ）＜Ｈ・γｗの関係になると盤ぶくれが発生す
る。2. Description of the Related Art Conventionally, when a ground having a high pressure U is deeply excavated as shown in FIG. There is a high possibility that this will occur (upward collapse). That is, assuming that the size of the overburden weight is W and the size of the pressurized water pressure is U, W =
1.2 (h.γ t ), where h is soil cover and γ t is unit weight of soil. U = H · γ w , where H is the pressure head and γ w is the unit weight of water, the relationship between W and U is 1.2
When the relationship (h.γ t ) <H · γ w is satisfied, a bulge occurs.
そこで従来は、盤ぶくれ防止対策として、第３図に示
したように不透水層（粘性土層）１を貫通してその下の
被圧滞水層２に達するディープウエル３を打ち込み、強
制的排水により被圧水頭Ｈを低下させ盤ぶくれを防止す
ることが行なわれている。Conventionally, as a countermeasure against board swelling, as shown in FIG. 3, a deep well 3 that penetrates through an impermeable layer (cohesive soil layer) 1 and reaches a pressure-bearing aquifer layer 2 thereunder is driven into the well. It has been practiced to reduce the pressurized head H by the purpose of drainage to prevent the board from bulging.
本発明が解決しようとする課題 従来のディープウエル３による盤ぶくれ防止工法は、
強制的に被圧水を排水するため、被圧水圧Ｕと土被り重
量Ｗとのつり合いを保ち難く、停電等によりディープウ
ェルが停止した場合２次災害の危険性があるほか、ディ
ープウエル３の費用及び排水料金を含む排水コストが高
くなる欠点があり、本発明の解決するべき課題になって
いる。Problems to be Solved by the Present Invention The conventional method for preventing swelling by the deep well 3 is as follows.
Since the water under pressure is forcibly drained, it is difficult to maintain the balance between the water pressure U under pressure and the weight W of the overburden, and there is a danger of a secondary disaster if the deep well stops due to a power outage or the like. There is a drawback that the drainage cost including the cost and the drainage fee is increased, which is a problem to be solved by the present invention.
課題を解決するための手段 上記従来技術の課題を解決するための手段として、こ
の発明に係る減圧方式による盤ぶくれ防止工法は、第１
図に実施例を示したとおり、 根切り底４の直下の不透水層（粘性土層）１をさらに
その下の被圧滞水層２にまで貫通する減圧孔５を設け、
該減圧孔５を通じて湧出した被圧水は根切り底４の排水
により排除して被圧水圧の減圧を行なうことを特徴とす
る。Means for Solving the Problems As means for solving the above-mentioned problems of the prior art, a method for preventing bulging by a decompression method according to the present invention is the first method.
As shown in the embodiment of the figure, a decompression hole 5 is provided that penetrates the impermeable layer (cohesive soil layer) 1 directly below the root bottom 4 to the pressure-bearing aquifer layer 2 therebelow.
The pressurized water that has flowed out through the pressure reducing hole 5 is removed by drainage of the root bottom 4 to reduce the pressure of the pressurized water.
作用 被圧滞水層２内の被圧水は、その直上の土被り重量Ｗ
とのつり合いを保つ程度に、減圧孔５を通じて根切り底
４へ湧出し、つり合いが自然に保たれる。従って、排水
は根切り底４の部分へ湧出した被圧水だけ排除すれば足
りる。Action The pressurized water in the pressurized stagnation layer 2 has an overburden weight W immediately above it.
To the extent that the balance is maintained, the well is discharged to the root bottom 4 through the decompression hole 5 and the balance is naturally maintained. Therefore, it is sufficient for the drainage to remove only the pressurized water that has flowed to the root 4.
実 施 例 次に、第１図と第２図に示した本発明の実施例を説明
する。Embodiment Next, an embodiment of the present invention shown in FIGS. 1 and 2 will be described.
第１図は、根切り底４の直下に不透水層（粘性土層）
１に、これを上下方向に貫通してその下の被圧滞水層
（砂質土層）２にまで通ずる減圧孔５…を、根切り底４
の全面にわたりバランスの良い配置で設け、土被り重量
Ｗをオーバーする圧力分の被圧水は根切り底４の部分
（砂質土）への湧出とすることを可能ならしめている。
つまり、減圧孔５の孔径と配置ピッチ及び配置本数は、
減圧孔５による被圧水圧の全面一様な減圧を可能ならし
めるよう配置されている。ちなみに、減圧孔２の構成
は、第２図に示したように、不透水層１を貫通する削孔
10の中にやや小径のケーシングパイプ11を挿入し、同ケ
ーシングパイプ11の外周と不透水層１の部分の削孔壁面
との間に膨潤型ゴムの如きパッカー12を装着した構成と
されている。一方、地上からは不透水層１の上の根切り
底部分４の深さの限度にウエルポイントのような井戸６
を設置し、前記減圧孔５を通じて根切り底部分４へ湧出
した被圧水だけを排除する構成とされている。FIG. 1 shows an impermeable layer (cohesive soil layer) immediately below the root bottom 4
1, pressure-reducing holes 5 penetrating vertically through the pressure-retaining aquifer layer (sandy soil layer) 2 thereunder,
Is provided in a well-balanced arrangement over the entire surface, and the pressurized water corresponding to the pressure exceeding the overburden weight W can flow out to the root bottom 4 (sandy soil).
That is, the diameter, arrangement pitch, and number of the decompression holes 5 are:
The pressure reducing hole 5 is disposed so as to enable uniform reduction of the pressure of the pressurized water over the entire surface. Incidentally, as shown in FIG. 2, the structure of the decompression hole 2 is a drilling hole penetrating the water-impermeable layer 1.
A casing pipe 11 having a slightly smaller diameter is inserted into the casing 10 and a packer 12 such as swelling rubber is mounted between the outer periphery of the casing pipe 11 and the bored wall of the portion of the water-impermeable layer 1. . On the other hand, from the ground, a well 6 such as a well point is limited to the depth of the root bottom 4 above the impermeable layer 1.
Is installed, and only the pressurized water that has flowed out to the root bottom portion 4 through the decompression hole 5 is eliminated.
従って、排水量もさほど多くはない。何よりも被圧水
圧Ｕと土被り重量Ｗとのつり合いが自然に保たれるた
め、盤ぶくれ現象は未然に確実に防止されるほか、被圧
水の強制的排水の場合に比較して地盤の安定性が高い。Therefore, the amount of drainage is not so large. Above all, since the balance between the pressurized water pressure U and the overburden weight W is naturally maintained, the swelling phenomenon is reliably prevented beforehand, and the ground pressure is lower than in the case of forced drainage of pressurized water. High stability.
本発明が奏する効果 本発明に係る減圧方式による盤ぶくれ防止工法によれ
ば、被圧水圧と土被り重量とのつり合いを自然に保ちな
がら被圧水圧を減圧して盤ぶくれが防止され、地盤掘削
工事の安全性に寄与する。また、従来のディープウエル
等による強制的排水による工法に比してディープウエル
費用がかからず、また、排水量そのものも少ないので、
綜合的な排水コストを大幅に低減でき、経済性を高めら
れるのである。Advantageous Effects of the Present Invention According to the lapping prevention method by the depressurization method according to the present invention, lapping is prevented by reducing the pressure to be applied while naturally maintaining the balance between the pressure to be applied and the earth covering weight, Contributes to the safety of excavation work. In addition, compared to the conventional method using forced drainage by deep wells, etc., deep well costs are not required, and the amount of drainage itself is small,
The overall cost of drainage can be greatly reduced, and the economy can be improved.
第１図は本発明の実施例を要部について示した断面図、
第２図は減圧孔の構成を示した斜視図、第３図は従来工
法を要部について示した断面図である。 ４……根切り底、１……不透水層 ２……被圧滞水層、５……減圧孔 ６……排水用の井戸FIG. 1 is a cross-sectional view showing a main part of an embodiment of the present invention,
FIG. 2 is a perspective view showing the structure of the pressure reducing hole, and FIG. 3 is a cross-sectional view showing a main part of the conventional method. 4 ... root bottom 1 ... impervious layer 2 ... pressure-bearing aquifer 5 ... decompression hole 6 ... well for drainage
───────────────────────────────────────────────────── フロントページの続き (72)発明者 甲野 裕之 広島県広島市中区橋本町10番10号 株式 会社竹中工務店広島支店内 (56)参考文献 特開 昭62−59727（ＪＰ，Ａ) 特公 昭30−6824（ＪＰ，Ｂ１) ──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Hiroyuki Kono 10-10, Hashimotocho, Naka-ku, Hiroshima-shi, Hiroshima In the Hiroshima branch of Takenaka Corporation (56) References JP-A-62-59727 (JP, A) Tokiko 30-3024 (JP, B1)
Claims (1)
の被圧滞水層にまで貫通する減圧孔を設け、該減圧孔を
通じて湧出した被圧水は根切り底部分における排水によ
り排除して被圧水圧の減圧を行なうことを特徴とする、
減圧方式による盤ぶくれ防止工法。1. A pressure reducing hole is provided which penetrates an impermeable layer immediately below a root cut bottom to a pressure-retained aquifer layer thereunder, and pressurized water discharged through the pressure reducing hole is discharged by drainage at the root cut bottom. Characterized in that the pressure of the pressurized water is reduced and eliminated.
Prevention of swelling by pressure reduction method.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP13589090A JP2714873B2 (en) | 1990-05-25 | 1990-05-25 | Prevention of swelling by decompression method |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP13589090A JP2714873B2 (en) | 1990-05-25 | 1990-05-25 | Prevention of swelling by decompression method |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPH0430019A JPH0430019A (en) | 1992-02-03 |
| JP2714873B2 true JP2714873B2 (en) | 1998-02-16 |
Family
ID=15162193
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP13589090A Expired - Fee Related JP2714873B2 (en) | 1990-05-25 | 1990-05-25 | Prevention of swelling by decompression method |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JP2714873B2 (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| KR100873089B1 (en) * | 2008-05-30 | 2008-12-09 | 주식회사 도화종합기술공사 | Underground aqueduct with reducing well on confined aquifer for settlement prevention |
Families Citing this family (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN115262661B (en) * | 2022-09-29 | 2022-12-06 | 北京城建设计发展集团股份有限公司 | Soil taking method and system for tunnel floating treatment |
-
1990
- 1990-05-25 JP JP13589090A patent/JP2714873B2/en not_active Expired - Fee Related
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| KR100873089B1 (en) * | 2008-05-30 | 2008-12-09 | 주식회사 도화종합기술공사 | Underground aqueduct with reducing well on confined aquifer for settlement prevention |
Also Published As
| Publication number | Publication date |
|---|---|
| JPH0430019A (en) | 1992-02-03 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| LAPS | Cancellation because of no payment of annual fees |