JPH0745657B2 - Ground stabilization method - Google Patents

Description

The present invention relates to a method for stabilizing the ground.

More specifically, the present invention relates to a method for stabilizing the ground using a silicate-based ground stabilizer (hereinafter, referred to as grout) containing colloidal silica as a main agent and carbon dioxide as a curing agent.

[Prior art]

Conventionally, silicate soda is used as the main agent of the silicate-based soil stabilizer, generally, the molar ratio of SiO ₂ to Na ₂ O of silicic acid in sodium (SiO ₂ / Na ₂ O) is at 2.9 to 3.4 JIS K
-1408, No. 3 product is widely used. Usually, these sodium silicates are diluted with water to form a main agent liquid, and mixed with various curing agents to produce grout.

[Problems to be solved by the invention]

Grouts containing sodium silicate as a main component and carbon dioxide as a curing agent are well known, but these grouts have the following drawbacks.

1) The strength of a cured product obtained by curing an aqueous solution of sodium silicate is such that the curing agent is an organic type such as glyoxal or ethylene carbonate if the ratio of the main agent, sodium silicate, to the curing agent is appropriately adjusted. In some cases, it generally increases as the concentration of sodium silicate is increased, and the uniaxial compressive strength of sand gel is about 8 to 10 kgf / cm ² or more, while the hardening agent is inorganic type. In some cases, the strength of the cured product obtained is limited even if the concentration of sodium silicate is increased, and only a value of about ² to 4 kgf / cm ² can be obtained.

2) The curing time of the grout is usually adjusted by changing the ratio of the amount of the curing agent used to the main agent used. Speaking of using carbon dioxide as a curing agent,
A stoichiometrically high amount of carbon dioxide is required to obtain a grout with a short setting time. Therefore, in such a case, the method of mixing gaseous carbon dioxide with sodium silicate causes a large amount of unreacted gas to be included in the grout, and thus a uniform grout cannot be obtained. It is difficult to carry out sufficient ground stabilization when using grout in various states.

The method of producing grout by mixing carbonated water and sodium silicate requires the use of carbonated water having a high carbon dioxide concentration. However, since the solubility of carbon dioxide in water is extremely small at about 0.2% at room temperature and atmospheric pressure, it is necessary to manufacture pressurized carbonated water with a high concentration of carbon dioxide and handle it under high pressure. Therefore, there is a problem in terms of occupational safety and energy, and in addition, there are various equipment costs such as pressurized carbonated water production equipment, grout injection equipment using pressurized carbonated water, pumps / pipes and other incidental equipment. It will be extremely expensive.

[Means for solving problems]

The present inventors have conducted various studies in order to improve the above-mentioned drawbacks, and in a grout using carbon dioxide as a curing agent, when a colloidal silica-containing composition is used as a main component, a conventional solution containing sodium silicate as a main component is used. It was found that a high-strength cured product, which could not be obtained with the type inorganic grout, can be obtained, and that the operating pressure can be greatly reduced even when grout having a short curing time is obtained by using carbonated water. Completed the invention.

The present invention relates to a "method for stabilizing the ground using a silicate-based ground stabilizer having carbon dioxide as a curing agent, characterized by using a composition comprising colloidal silica as a main ingredient. "Stabilization method of".

The present invention will be described below.

Colloidal silica used as a raw material for the main ingredient of grout used in the method of the present invention is a colloidal solution in which fine particles such as silicic acid and aluminum silicate are dispersed in an aqueous medium, and 10 to 50 as SiO ₂ per 100 parts by weight of the composition. Parts by weight, preferably 15 to 40 parts by weight, more preferably 20 to 30 parts by weight.

The size of these particles is preferably 100 mμ or less.

Since the colloidal silica used in the present invention is used for the production of grout, it prevents the separation phenomenon from occurring, reduces the increase / decrease in viscosity due to temperature changes, and prevents freezing at low temperatures, and
In order to obtain a high-strength cured product by reaction with carbon dioxide, which is a curing agent, it is preferable to preliminarily make an alkaline atmosphere.

Therefore, it is advisable to add a water-soluble compound that does not act as a curing agent, such as a hydroxide, carbonate, or silicate of an alkali metal such as Na or K as an alkaline component.

The addition amount of the alkali component, for example in the case of Na compounds, 3-14 parts by weight Na ₂ O per 100 parts by weight of the composition, preferably 4 to 11 parts by weight, even more preferably in the range of 5 to 9 parts by weight.

Specifically, 1 to 9 parts by weight as Na per 100 parts by weight of the composition, preferably 2 to 7 parts by weight, more preferably 3 to 6 parts by weight.
When at least one part by weight of sodium hydroxide, sodium carbonate and the like is added in combination with 0.4 to 5 parts by weight, preferably 0.6 to 4 parts by weight, more preferably 0.8 to 3 parts by weight of water-soluble powdered sodium silicate. Good.

To produce grout for use in the method of the present invention,
The composition of the present invention containing colloidal silica is optionally diluted with water according to the curing time of the grout suitable for the construction purpose or the desired strength of the cured product, and the diluted composition is used as the main agent liquid for injection. Usually 1 as SiO ₂ per 100 base liquids for injection
It should contain 0-40kg.

Carbon dioxide used as a curing agent in the present invention is usually a high-pressure gas or liquid filled in a predetermined container, and there is no limitation on its use in the method of the present invention.

It is possible to produce grout by extracting carbon dioxide in a gaseous state from a filling container through a pressure reducing valve and mixing it with the main agent liquid by using a method or a reactor disclosed in JP-B-58-14894.

Alternatively, as shown in Japanese Patent Publication No. 58-53678,
A method of producing carbonated water by absorbing and dissolving carbon dioxide in water using a gas-liquid contact device such as a packed tower, a stirring tank, a line mixer, and a two-fluid nozzle, and mixing the obtained carbonated water with the main agent liquid is Is preferred as an embodiment of the present invention. When dissolving carbon dioxide in water, high-concentration carbonated water can be obtained by keeping the inside of the gas-liquid contactor under pressure with carbon dioxide.

The device for mixing the carbon dioxide and the main agent liquid is not limited in its structure in the present invention, but preferably has a structure capable of well mixing both, for example, Y which is commonly used for ground injection of grout. A character structure, a simple double pipe structure, an orifice contactor, a fluid mixing element, a two-fluid nozzle, a static mixer and the like are preferably used. In order to prevent carbon dioxide from volatilizing at the time of pouring grout, a pressure-holding structure such as a valve, a cock, and a nozzle may be provided on the outlet side of the mixing device.

The amount of carbon dioxide used as a curing agent is preferably in the range of 1 to 1/6 mol equivalent as CO _{2 with} respect to 1 mol of Na ₂ O contained in the main agent liquid.

The amount of carbon dioxide used is CO with respect to 1 mol of Na ₂ O in the main agent liquid.
_{If the} amount is less than 1/6 mol, the curing time of the grout becomes long, and even if the grout is gelled, the strength of the gel produced is extremely low and the solidification is not sufficient. On the other hand, if the amount of CO ₂ is more than 1 mol equivalent to 1 mol of Na ₂ O in the main agent liquid, carbon dioxide cannot be completely reacted and bubbles are generated in the grout, or even bubbles are not generated. It is not preferable for ground stabilization because the gel condition becomes non-uniform.

The amount of carbon dioxide used is adjusted according to the curing time of the grout suitable for the construction purpose.

The grout obtained by mixing the main agent liquid and the curing agent is injected into the ground and cured.

Even when the grout is produced by directly contacting the gaseous carbon dioxide with the main agent liquid, the reaction becomes easier and more uniform when the main agent of the present invention is used, as compared with the case of using the conventional sodium silicate aqueous solution. It is possible to obtain a strong grout and to make the treated ground more solid.

〔The invention's effect〕

 According to the present invention, the following effects can be obtained.

1) It is possible to obtain a high-strength cured product that could not be obtained by the conventional solution-type inorganic grout containing sodium silicate as a main component.

2) The required amount of carbon dioxide as a curing agent can be saved more than ever before.

3) In the case of using carbonated water as the curing agent, it is possible to use carbonated water having a lower concentration than before in order to obtain grout having the same curing time, and it is possible to drastically reduce the pressure for producing and handling carbonated water. it can.

As a result, not only the carbonated water production facility, but also various devices such as infusion pumps, pipes, and infusion pipes can have a simple structure, which is extremely advantageous in terms of energy saving.

4) When using gaseous carbon dioxide as the curing agent,
The amount of unreacted carbon dioxide is small, and the ground can be stabilized without increasing the pressure in the ground.

〔Example〕

Hereinafter, the present invention will be specifically described with reference to Examples and Comparative Examples.

Example-1 and Comparative Example-1-Preparation of main agent liquid (liquid A); water was added to the colloidal silica-containing composition (CS) to prepare 200
As the solution A, various concentrations were prepared.

For comparison, a liquid A for comparison was prepared in the same manner as JIS No. 3 sodium silicate (SS).

・ Preparation of curing agent (liquid B); Packed absorption tower (stainless steel, diameter 270 mm, height 1800 m
m, S type terraret filling), water was supplied from the upper part, while carbon dioxide was supplied from the lower part to produce carbonated water.

Liquid B was prepared by adjusting the carbon dioxide concentration in the carbonated water by adjusting the tower internal pressure by a mechanism that controls the water and carbon dioxide supply rates and the carbon dioxide flow rate to control the tower internal pressure. .

The grout injection pipe used was one in which a static mixer was installed at the confluence of both liquids A and B at the tip thereof, and a spring type pressure holding valve capable of holding the pressure in the confluence was provided at the outlet of the mixer.

Using a pump, the liquid A was supplied to one inlet of the merging portion and the liquid B was supplied to the other inlet at a rate of 3 / min. Both liquids A and B were mixed instantaneously in the confluence to obtain grout.

The obtained grouts were poured into a mold filled with standard sand, and the uniaxial compressive strength of the sand gel after each hardening time and one day after hardening was measured, and the results are shown in Table 1. The test temperature was 20 ° C.

Generally, JIS No. 3 sodium silicate contains 28-30% by weight of SiO _2.
Contains. In this example, even when the SiO ₂ content in the grout is lower than that in the comparative example, a grout suitable for the instant-setting method can be obtained with a curing time of 10 seconds or less to several seconds, and the obtained sand gel is compressed. The strength is dramatically improved.

Example-2 and Comparative Example-2.-Preparation of main agent liquid (liquid A): In accordance with Example-1, a colloidal silica-containing composition (C
S) and JIS No. 3 sodium silicate (SS) for comparison
Water was added to 100 to make 200 each to prepare solution A.

-Preparation of curing agent (solution B): The apparatus used in Example 1 was used to adjust the amount of CO _{2 in} solution B according to the method according to Example-1 to prepare solutions B having various concentrations.

The obtained solutions A and B are mixed in equal volumes to obtain grout,
The curing time of each was measured.

The temperature of solution A and solution B was 20 ° C.

From these results, the curing time of grout-CO _{2 in} liquid B
The corresponding values of quantity-operating pressure are shown in Table 2.

As shown in Table 2, when the operating pressure of the absorption tower for producing the liquid B is increased, the amount of CO ₂ in the liquid B is increased and the curing time of the obtained grout is shortened. However, in the case of using the main ingredient-colloidal silica-containing composition of the present invention to obtain grout showing the same curing time, the absorption tower is compared with the case of using the conventional JIS No. 3 sodium silicate. It is possible to greatly reduce the internal pressure by more than 10 kg / cm ² -G.

It should be noted that when conventional technology JIS No. 3 sodium silicate is used, gas is generated from the grout when attempting to shorten the curing time of the grout to less than 10 seconds, which is a problem for practical use for ground stabilization work. However, it cannot be used under such conditions.

Claims (1)

[Claims] 1. A method of stabilizing a ground using a silicate-based ground stabilizer containing carbon dioxide as a hardening agent, wherein a composition containing colloidal silica as a main component is used. Stabilization method.