JPH01158109A - Solidification of soft soil - Google Patents

Abstract

PURPOSE:To permit soft soil to be solidified and transported by a method in which a water-soluble cationic high molecular compound powder and a water-soluble anionic high molecular compound powder are added to soft soil of high water content. CONSTITUTION:A water-soluble cationic high molecular compound, e.g., aminoalkyl acrylate homopolymer, or the water-soluble cationic high molecular compound and a water-soluble anionic high molecular compound powder, e.g., polyacrylic acid or its salt, are added and agitated to soft discharged soil of high water content is construction work such as sludge press shield, mud water shield, underground continuous wall, foundation pile, etc. Free water in the soft soil is absorbed by the high molecular compounds to become gelled and solids are coagulated and given a tacky property. The whole of the solid can thus be solidified under a condition that free water is kept in the voids of the coagulated solids.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] This invention relates to a method for consolidating soft soil with a high moisture content.

[Conventional technology]

The excavated soil discharged during construction works such as mud pressure shields, muddy water shields, underground continuous walls, and foundation piles contains soft soil with a high moisture content, which is difficult to transport by dump truck as it is. It is carried out to modify and transport by adding a modifier.

Conventionally, a method for improving soft soil that has a high moisture content and is difficult to transport using normal dump trucks is to use 30 to 100 kg of inorganic materials such as quicklime and cement.
/-・In addition to removing soil at a ratio of soil, a method of improving transportability by utilizing the hydraulic properties of soil (for example, Japanese Patent Application Laid-Open No. 61-2169
No. 94) and a method of modifying by adding 1 to 10 kg/m of water-absorbing resin represented by cross-linked sodium polyacrylate which is insoluble in water (for example, JP-A-58-27780). ing.

On the other hand, as a method for coagulating slurry, a method is used in which powder of an acrylamide-based polymer compound is added to the slurry, the slurry is transferred in a fluid state, and the powdered polymer compound is dissolved during transfer to cause coagulation (for example, Japanese Patent Publication No. 56 -35959)
It has been known.

[Problem that the invention seeks to solve]

However, the above-mentioned consolidation method using quicklime, cement, etc. has the following problems.

■The modification effect is small and does not solidify.

■The pH during modification becomes strongly alkaline.

■Since the reaction time takes several days, a vast area is required for the treatment, making it impossible to improve the soil at the site where it is discharged, especially in construction works in urban areas where disposal of waste soil is a problem.

■A large amount of drugs are used.

Furthermore, the method using a water-absorbing resin has the following problems.

■The reforming effect is insufficient, especially near the coast.
Or, if the ground is improved with water glass or the like in advance, the effectiveness will be significantly reduced if the ground has a high salt concentration.

(2) Although the reaction time is longer than the above-mentioned quicklime and cement, it still takes about 30 minutes.

■When piled up in the open, modified soil will not dry out forever because of its water-retaining ability, and even if it dries out, once it encounters rainfall, it will absorb water again, and because of this repetition, it will remain damp forever.

Furthermore, since the slurry coagulation method using an acrylamide-based polymer compound targets the slurry being transferred through a pipe, solid-liquid separation is required for coagulation, and the separated solid content is larger than the soft soil targeted by the present invention. Since it is much softer, it will solidify after a long time if left as is, but it cannot be transported by dump truck immediately after separation, and further processing such as dehydration is required for transportation.

The purpose of this invention is to solve the above-mentioned problems by making it possible to consolidate soft soil in a short time with a small amount of modifier, and to be able to consolidate soft soil with a wide range of moisture content. The purpose of this study is to propose a method of compacting soft soil with high quality effects.

[Means for solving problems]

This invention adds a water-soluble cationic polymer compound or a powder of a water-soluble cationic polymer compound and a water-soluble anionic polymer compound to soft soil to absorb free water in the soft soil. The present invention also provides a method for consolidating soft soil, characterized in that the soft soil is consolidated by imparting adhesiveness.

The soft soil to be treated in this invention is soil with a high water content such as excavated soil discharged during construction work as exemplified above, and the water content is about 20 to 85% by weight. In particular, those having a water content of 50 to 85% by weight are suitable targets.

There are no restrictions on the water-soluble cationic polymer compound used as a modifier in this invention, but examples include homopolymers of aminoalkyl (meth)acrylates, copolymers with acrylamide or other mothmers, and polyacrylamide copolymers. Synthetic polymer compounds such as Hofmann decomposition products and Mannich modification products, polyamide polyamines, polyvinylimidacillin, polyethyleneimine, and polydialkyl diallylammonylim salts are preferred. These water-soluble cationic polymer compounds can be used alone or in combination of two or more.

In the present invention, only a powder of a water-soluble cationic polymer compound may be used as a modifier, but a powder of a water-soluble cationic polymer compound and a powder of a water-soluble anionic polymer compound may be used. Preference is given to using formulations.

There are no restrictions on the water-soluble anionic polymer compound that can be used, but synthetic polymer compounds such as those shown below are preferred.

(1) Polyacrylic acid (or its salt), polyacrylamide partial hydrolyzate, acrylamide and acrylic acid (
A polymer compound containing a carboxylic acid (or a salt thereof) such as a copolymer with a carboxylic acid (or a salt thereof).

(2) Polymer compounds containing sulfonic acid (or a salt thereof) such as polyvinylsulfonic acid (or a salt thereof) and a copolymer of acrylamide and 2-acrylamido-2-methylpropanesulfonic acid (or a salt thereof).

(3) Carboxylic acids (or salts thereof) and sulfonic acids (or A polymer compound with salt).

There are no particular limitations on the degree of polymerization of cationic polymer compounds and anionic polymer compounds; The polymer compound is 6
．． It is sufficient if it is 0 or more, and preferably 4.5 or more for cationic polymer compounds and 10 or more for anionic polymer compounds.

The particle size of the drug is not particularly limited, and the purpose can be achieved as long as it is about 10 mesh or less.

In the present invention, powders of a water-soluble cationic polymer compound or a water-soluble cationic polymer compound and a water-soluble anionic polymer compound as described above are added to soft soil, and the powder is added to soft soil without performing solid-liquid separation. Consolidates soft soil to enable transportation by belt conveyor, etc.

In the case of a cationic polymer compound alone, the powder is used as it is, and in the case of a combination agent, the cationic polymer compound and anionic polymer compound are mixed in advance at a weight ratio of cation to anion of 3 = 1 to 1. :2. Preferably 2:1-1:
Add a mixture of 1:1 to soft soil in powder form,
Mix and stir.

The amount added varies depending on the soil quality, moisture content, etc., but generally it is 0.2 to 20 kg per soft soil, preferably 0.5 to 20 kg.
It is 5 kg. If it is less than this value, the effect will be poor,
Too much is not a problem in terms of effectiveness, but it is uneconomical.

When a water-soluble cationic polymer compound, or a powder of a water-soluble cationic polymer compound and a water-soluble anionic polymer compound is added to soft soil and mixed and stirred, the polymer compound converts into free water in the soft soil. It absorbs water, turns into a gel, aggregates the solids, and gives them stickiness, so the whole solidifies with free water trapped in the gaps between the aggregates. Therefore, even without solid-liquid separation as in the case of slurry, the entire soft soil is consolidated, and it is possible to load it onto a dump truck, belt conveyor, etc. and transport it as is.

Consolidation of such soft soil can be completed in about 3 to 10 minutes, so it can also be treated at a construction site.

The difference between the consolidation of soft soil in the present invention and the consolidation of slurry using conventional polymer compounds lies in the difference in mechanism due to the difference in water content. In other words, the conventional slurry is a suspension containing about 95 to 99% water by weight, which is much higher than the soft soil targeted by the present invention. It is in a suspended state. When a powdered polymer compound is added to this, the polymer compound dissolves during transportation, becomes an aqueous solution, and aggregates the solid content, so by subsequently separating water by solid-liquid separation,
A concentrated solid is obtained. Since this solid content still has a high water content, further operations such as dehydration are required, and it cannot be transported as is by a dump truck or the like.

On the other hand, in the consolidation of soft soil in the present invention, as mentioned above, the water-soluble polymer compound absorbs free water in the soft soil and gels it, so that the free water in the soft soil disappears and , which agglomerates solid content to give it stickiness.
The whole solidifies without performing solid-liquid separation.

Further, conventional consolidation using lime, cement, etc. utilizes the hydraulic properties of lime, cement, etc., and is different from the method of the present invention, which absorbs water and coagulates. Furthermore, conventional water-absorbing resins only perform water-absorbing action.

This is different from the one that performs water absorption and aggregation according to the present invention. Since the present invention utilizes the water absorbing, cohesive, and tackifying properties of water-soluble polymer compounds, it has a greater effect on improving soft soil than these conventional methods, and can consolidate soft soil in a short time. can do.

When soft soil is consolidated with a water-soluble cationic polymer compound or a cationic and anionic polymer compound, the consolidation effect is better than when treated with an anionic or nonionic polymer compound.

〔Effect of the invention〕

According to the present invention, powder of a water-soluble cationic or cationic and anionic polymer compound is added to soft soil with a high water content and consolidated, so a small amount of chemical agent is added and a short time is achieved. It can consolidate and transport soft soil, can be applied to soft soil with a wide range of moisture content, and has a high reforming effect.
It has advantages such as being able to be treated at construction sites.

〔Example〕

Examples of the present invention will be described below. In the examples, % indicates weight %.6 The test conditions and test methods of the examples are as follows.

(1) Test conditions i) Type of sample Excavated soil from shield construction site (Sampling location, Yozaki City) Soil quality: Silt (Japan unified soil classification C) I) if) Moisture content of sample 57%, 66%, 81. 1% ■) Flow value of sample When moisture content is 57% 250 x 250 moisture content 66
% 300 x 300 or more Moisture content 81.1%
When: 300 x 300 or more and less than 300 samples 400ta Q Actually, the unit volume weight is measured in advance, and the sample is collected by weight.

■) Modifier Water-soluble cationic polymer compound (C) Methyl chloride of dimethylamino methacrylate (estimated molecular weight 8,000,000) Water-soluble anionic polymer compound (A): Partial hydration of polyacrylamide Degradation product (estimated molecular weight 14,000,000) Water-soluble nonionic polymer compound (N): Polyacrylamide (estimated molecular weight 12,000,000) vL) Stirring time: 3 minutes if modification is completed quickly, maximum 10 minutes.

(2) Test method A 400 mm sample was placed in an IQ polyethylene beaker, a predetermined amount of the drug was added thereto, and the mixture was stirred for 3 to 10 minutes using a spatula. When the solidification was completed, the time required was recorded, and if the solidification was not completed, the test was stopped after 10 minutes and a flow test was immediately conducted in accordance with the "physical testing method for mortar" specified in JIS-85201. Conventional methods using water-absorbing resin, quicklime, and cement as controls were conducted in exactly the same manner.

Note that if the flow value is within 110 x 110, it can actually be transported by a dump truck. Furthermore, it is somehow possible to transport when the flow value is within the range of 110XIIO to 120X120, but when it exceeds 120X120, transport becomes impossible.

The test results are shown in Table 1.

Claims (4)

[Claims] (1) Adding a water-soluble cationic polymer compound or a powder of a water-soluble cationic polymer compound and a water-soluble anionic polymer compound to the soft soil to absorb free water in the soft soil, and , by imparting tackiness,
A method for consolidating soft soil, comprising: consolidating the soft soil. (2) The method for consolidating soft soil according to claim 1, wherein the moisture content of the soft soil is about 20 to 85% by weight. (3) The solidification of soft soil according to claim 1 or 2, wherein the weight ratio of the water-soluble cationic polymer compound to the water-soluble anionic polymer compound is 3:1 to 1:2. How to tie. (4) The method for consolidating soft soil according to any one of claims 1 to 3, wherein the soft soil is excavated soil discharged during construction work.