【発明の詳細な説明】
本発明は超軟弱地盤若しくは軟弱地盤の走行性
を改良する為の超軟弱地盤若しくは軟弱地盤の表
面処理工法に関する。
茲でいう超軟弱地盤とは、臨海埋立地、干拓
地、沼沢地などに見られる高含水泥質より成り、
流動性が大きく、液性限界を超えた軟弱地盤を指
す。また軟弱地盤とは、高含水泥質より成るも、
湿地ブルドーザの運行が可能かどうかの限界附近
の軟弱度を有する地盤を指称する。
臨海埋立地、干拓地、沼沢地などは勿論のこ
と、環境浄化のために底質を浚渫し封じ込めて造
成される有害重金属を含んだ地盤などの所謂、超
軟弱地盤若しくは軟弱地盤といわれる地盤を安定
化して、道路、構築物或いは緑地を造成するなど
のニーズは極めて多い。
超軟弱地盤若しくは軟弱地盤を加良、安定化し
て土地利用を可能にするためには、先ず改良工事
を施すに必要な工事用機械、車輌の導入のため、
その上に土砂を巻き出して覆土し、走行性の改良
と確保が必要欠くべからざる工程である。
超軟弱地盤若しくは軟弱地盤上に土砂を巻き出
して覆土するために従来から各種の工法が提案さ
れている。その主なものは、巻き出し土砂と超軟
弱地盤若しくは軟弱地盤との間に繊維シート或い
はプラスチツク網などを介在せしめるとか、或い
は地盤の表層にセメント、石灰系の固結剤を添
加、混合して固化させるなどの方法である。
これらの在来工法は確かに有効な工法である
が、然し乍らその施工性なでに多少の難点が指摘
されより優れた工法の出現が強く望まれているの
が現状である。
本発明は超軟弱地盤若しくは軟弱地盤の表面
に、けい酸ゾル（シロキシシラノール）を散布或
いは流し込むという簡易な方法で、その表面にけ
い酸ゲルの硬質膜層を形成し、その硬質な物理性
と支持力を活かして直接表面に土砂の巻き出しを
可能にし、超軟弱地盤若しくは軟弱地盤の改良安
定化工事に貢献する新規な方法を提供するもので
ある。
茲で第１図、第２図は超軟弱地盤の表面処理工
法に於ける実施の一例を示す説明図であつて、先
ず第１図は超軟弱地盤に直接土砂を巻き出した場
合、地盤は流動破壌を起して土砂は陥没し、地盤
の一部が隆起する状況を示しており、また第２図
に於いては、超軟弱地盤の表面に、本発明による
含水けい酸ゲルの膜層を作つた場合の土砂の巻き
出し状況を夫々示している。
本発明に使用するけい酸ゾル（シロキシシラノ
ール）は、けい酸ソーダを主剤とし、凝結剤とし
て硫酸、塩酸、硝酸、りん酸、酸性塩等の酸性物
質の一種又は数種の混酸を用い、中和法により調
整される化学材料で、一定の水素イオン濃度領域
でゲル化するという特性を持つものである。
本発明を更に詳しく説明すれば、比重1.05〜
1.08の水と殆んど変わらぬ低粘性の一液性けい酸
ゾルを、超軟弱地盤若しくは軟弱地盤の表面に散
布或いは流し込むという簡易な施工で、水平性を
保つ地盤表面に均等厚の液層を作ることは容易と
なるのである。この場合、水分過飽状の地盤に吸
収される虞れもない。そしてこの散布或いは流し
込みによつて出来るけい酸ゾルの液層は、数分〜
60分程度でゲル化し、均等厚に近い含水けい酸ゲ
ルの硬質な膜層に変わる。
この含水けい酸ゲルの硬度は、主剤として用い
るけい酸ソーダの稀釈度によつて左右されるが
JIS規格３号水ガラスを用いた場合、４倍稀釈液
でシヨアー硬度計C8.0、６倍稀釈液でC6.5程度
の硬度を示しており、そしてシヨアー軸度計
C6.5の含水けい酸ゲルの層厚10cm上で川砂敷厚
20〜30cmの垂直荷重に十分耐え得ることが実験で
確認せられた。
これは、超軟弱地盤に於いては巻き出し土砂の
陥没と地盤の流動破壌を防止し、また軟弱地盤に
於いては、巻き出し土砂と地盤の混合、泥寧化を
防止するのに本発明工法が有効であることを示す
ものである。
土砂の巻き出しに用いるブルドーザの走行のた
めには、Ｋ値が2.0Kg／cm2以上の確保が必要であ
る。
含水けい酸ゲルの膜層はブルドーザの走行を許
す強度は勿論期待できないが、先ず20cm以上の厚
みに土砂を巻き出し、その漸増をまつてブルドー
ザを使用すれば良く、また初期の巻き出しには、
ジエツトダンプを用いて土砂を射出散布する方法
が適当である。そして土砂の巻き出し層厚の漸増
をまち、その支持力を確認の上、ブルドーザの使
用に切り替えればよい。
実験の結果、含水率95％の泥質上に10cm厚の含
水けい酸ゲル層を作り、その上に20cm厚に川砂を
巻き出した場合のＫ値は2.2Kg／cm2の結果を得
た。
次に軟弱地盤層と巻き出し土砂との間に介在す
る構造は、土木の常識として、土砂の載荷重で圧
密され軟弱地盤層に含まれる水分を濾過、脱水す
るため透水性構造をもつものでなければならな
い。
含水けい酸ゲル層は硬質で土砂の垂直荷重に耐
えることは前述の通りであるが、含水けい酸ゲル
は縮合の進展に伴い、経時的に水分を離漿液とし
て滲出し容積を縮小する。この現象は、その上に
巻き出された土砂の積荷重により促進され、離漿
水は毛管水として土砂の中に吸いとられ容積を滅
少する。
斯くして脱水、容積縮小を起した含水けい酸ゲ
ル層は、縮合の進行に伴い硬度を漸増する反面、
けい酸ゲルの特性である脆性により、たて方向に
クラツクを発生して謂わば礫石を敷き並べた状態
に変わり、下方の軟弱層の含水を濾過、脱水する
役目を果たすことも実験で確認された。
本発明は上述の通り単一の液状、けい酸ゾル
（シロキシシラノール）を超軟弱地盤若しくは軟
弱地盤の表面に散布或いは流し込むという単純な
る処理工法で、超軟弱地盤若しくは軟弱地盤の表
面に土砂の巻き出しを可能にする支持力を与え、
同時に該地盤層に含まれる水分をフイルターする
機能をも併せ与えることになり、土木界に貢献す
る新工法たる価値を有するものと確信する。
けい酸ゾルはPH中性に近い無機組成物で、環境
上無害な化学材料であると共に、国内に豊富に存
在するけい砂を原料として作られるけい酸ソーダ
を主剤とするため、材料は全て安価に安定供給さ
れる点も本発明によるメリツトの一つである。
実施例
縦2.0ｍ、横1.5ｍ、深さ1.5ｍのコンクリート製
テストピツトに、粘性土に加水混合して作つた含
水率95％の泥土を75cm厚に詰め、その表面に３号
水ガラス４倍溶液を主剤とし、硫酸95、りん酸５
の混酸の10倍溶液を３；１の割合で混合して調整
したけい酸ゾル（PH6.5）を散布し、厚み10cmの
含水けい酸ゲル層を作つた。
含水けい酸ゲル層の生成後（２時間）川砂を10
cm厚、20cm厚、30cm厚の三区画に分けて覆土し
て、平板載荷試験を行ない、次の結果を得た。こ
の場合、いずれの区画も流動破壊による川砂の陥
没、地盤隆起の現象は認められなかつた。
含水けい酸ゲル層の硬度 シヨアー硬度計
C8.0
【表】DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a surface treatment method for ultra-soft or soft ground for improving the running performance of the ultra-soft or soft ground. The ultra-soft ground in Koma consists of highly water-containing mud found in coastal reclaimed land, reclaimed land, swampy land, etc.
Refers to soft ground that has high fluidity and exceeds the liquid limit. In addition, soft ground is composed of highly water-containing mud.
Wetland refers to the ground that has a softness near the limit of whether or not bulldozer operation is possible. In addition to coastal reclaimed land, reclaimed land, and swampland, we also use so-called ultra-soft or soft ground, such as ground containing toxic heavy metals that is created by dredging and sealing bottom sediment for environmental purification. There are many needs for stabilization and the creation of roads, structures, and green spaces. In order to improve and stabilize ultra-soft or soft ground and make it usable for land use, we first need to introduce the necessary construction machinery and vehicles for the improvement work.
This is an indispensable process that involves rolling out earth and sand and covering it with soil to improve and ensure runnability. Various construction methods have been proposed to cover ultra-soft or soft ground by rolling out earth and sand. The main methods are to interpose a fiber sheet or plastic net between the unrolled soil and ultra-soft or soft ground, or to add and mix cement or lime-based solidifying agents to the surface layer of the ground. This method involves solidifying the material. These conventional construction methods are certainly effective construction methods, but at the same time, some drawbacks have been pointed out regarding their workability, and there is a strong desire for the emergence of better construction methods. The present invention uses a simple method of spraying or pouring silicic acid sol (siloxysilanol) onto the surface of ultra-soft or soft ground, forming a hard film layer of silicic acid gel on the surface, and improving its hard physical properties. The present invention provides a new method that makes it possible to take advantage of the bearing capacity to directly roll out earth and sand onto the surface, contributing to improvement and stabilization work on ultra-soft or soft ground. Figures 1 and 2 are explanatory diagrams showing an example of the implementation of the surface treatment method for ultra-soft ground. First of all, Figure 1 shows that when earth and sand are rolled out directly onto ultra-soft ground, the ground This shows a situation in which the soil collapses due to flow failure, and a part of the ground rises. In addition, in Fig. Each figure shows the situation in which soil is thrown out when layers are created. The silicic acid sol (siloxysilanol) used in the present invention uses sodium silicate as the main ingredient, and uses one or several mixed acids of acidic substances such as sulfuric acid, hydrochloric acid, nitric acid, phosphoric acid, and acid salts as a coagulant. It is a chemical material prepared using the Japanese method, and has the property of gelling in a certain hydrogen ion concentration range. To explain the present invention in more detail, the specific gravity is 1.05~
A simple method of spraying or pouring a low-viscosity one-component silicic acid sol, which is almost the same as 1.08 water, onto the surface of ultra-soft or soft ground creates an evenly thick liquid layer on the ground surface that maintains horizontality. It becomes easy to make. In this case, there is no risk of the water being absorbed into the water supersaturated ground. The liquid layer of silicic acid sol that is formed by this spraying or pouring is formed within a few minutes.
It gels in about 60 minutes, turning into a hard film layer of hydrous silicic acid gel with a nearly uniform thickness. The hardness of this hydrous silicic acid gel depends on the degree of dilution of the sodium silicate used as the main ingredient.
When JIS standard No. 3 water glass is used, a 4-fold dilution shows a hardness of C8.0 on the Schauer hardness tester, a 6-fold dilution shows a hardness of about C6.5, and a Schauer axial hardness test
River sand bed thickness on C6.5 hydrous silicic acid gel layer thickness 10cm
Experiments have confirmed that it can sufficiently withstand vertical loads of 20 to 30 cm. This is essential to prevent the blown-out earth and sand from sinking and the ground to flow in extremely soft ground, and to prevent mixing of the blown-out earth and sand and the ground from becoming muddy in soft ground. This shows that the invented construction method is effective. In order for the bulldozer used to roll out earth and sand to run, it is necessary to ensure a K value of 2.0 kg/cm 2 or more. Of course, the membrane layer of hydrous silicic acid gel cannot be expected to have the strength to allow a bulldozer to run, but it is sufficient to first roll out the earth and sand to a thickness of 20 cm or more, wait for the thickness to gradually increase, and then use the bulldozer. ,
An appropriate method is to use a jet dump to inject and spread the soil. Then, after gradually increasing the thickness of the layer of earth and sand and confirming its supporting capacity, the use of a bulldozer can be switched to use. As a result of the experiment, when a 10 cm thick layer of hydrated silicic acid gel was made on mud with a water content of 95% and river sand was rolled out to a thickness of 20 cm on top of it, the K value was 2.2 Kg/ cm2 . . Next, as is common knowledge in civil engineering, the structure intervening between the soft ground layer and the rolled-out earth and sand is a water-permeable structure that is consolidated by the load of the earth and sand and filters and dewaters the water contained in the soft ground layer. There must be. As mentioned above, the hydrated silicic acid gel layer is hard and can withstand the vertical load of earth and sand, but as condensation progresses, the hydrated silicic acid gel oozes water as syneresis liquid over time, reducing its volume. This phenomenon is accelerated by the load of the earth and sand thrown out on top of it, and the syneresis water is absorbed into the earth and sand as capillary water, reducing its volume. The hydrous silicic acid gel layer, which has undergone dehydration and volume reduction, gradually increases in hardness as condensation progresses.
Due to the brittleness characteristic of silicic acid gel, it has been confirmed through experiments that cracks occur in the vertical direction, turning the gel into a state of being laid out with gravel, which serves to filter and dehydrate the water contained in the soft layer below. Ta. As mentioned above, the present invention is a simple treatment method in which a single liquid silicic acid sol (siloxysilanol) is sprayed or poured onto the surface of ultra-soft or soft ground, and the surface of the ultra-soft or soft ground is covered with earth and sand. Provides supporting force that allows for
At the same time, it also provides the function of filtering the moisture contained in the ground layer, and we are confident that it has value as a new construction method that will contribute to the civil engineering world. Silicate sol is an inorganic composition with a pH close to neutrality, and is an environmentally harmless chemical material.As the main ingredient is sodium silicate, which is made from silica sand, which is abundant in Japan, all materials are inexpensive. One of the advantages of the present invention is that it can be stably supplied. Example: A concrete test pit measuring 2.0 m long, 1.5 m wide, and 1.5 m deep is filled with mud with a moisture content of 95% made by adding water to clayey soil to a thickness of 75 cm, and the surface is covered with No. 3 water glass 4 times. Main ingredient: 95% sulfuric acid, 5% phosphoric acid
A silicic acid sol (PH6.5) prepared by mixing a 10-fold solution of a mixed acid (3:1) was sprayed on the surface to form a 10 cm thick hydrous silicic acid gel layer. After the formation of a hydrous silicic acid gel layer (2 hours), add 10% of river sand.
The soil was divided into three sections, 1 cm thick, 20 cm thick, and 30 cm thick, and covered with soil, and a flat plate loading test was conducted, and the following results were obtained. In this case, no river sand sinking or ground upheaval due to flow failure was observed in any of the sections. Hardness of hydrous silicic acid gel layer Sjoer hardness tester
C8.0 [Table]
【図面の簡単な説明】[Brief explanation of the drawing]
第１図、第２図は超軟弱地盤の表面処理工法に
於ける実施の一例を示す説明図である。
FIGS. 1 and 2 are explanatory diagrams showing an example of the implementation of the surface treatment method for ultra-soft ground.