JPH01103691A - Sea water kneaded ditch wall stabilizer suspension composition for ground excavation - Google Patents

Abstract

PURPOSE:To obtain the title compsn. free from deterioration caused by contamination with cement, by dissolving sodium salt of carboxymethylcellulose and sodium acrylate in a particular sea water and suspending therein fine clay powder. CONSTITUTION:0.2-0.6pts.wt. sodium salt of carboxymethylcellulose and 0.1-0.4 pts.wt. low-MW sodium polyacrylate having a number-average MW of 10,000 or below are dissolved in 100pts.vol. sea water having a hydrogen ion concn. index adjusted to 10-11.3 by addn. of sodium carbonate and/or sodium hydroxide. Then, 1-5pts. fine powder of a montmorillonite clay mineral or a kaolinite clay mineral is suspended, thereby obtaining a sea water kneaded ditch stabilizer suspension compsn. Polysodium acrylate for use as a dispersant has pref. an average MW of 10,000 or below. When the average MW exceeds 10,000, the performance of the stabilizer suspension is likely to be deteriorated by contamination with cement.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a trench wall stabilizing liquid for ground excavation using seawater (hereinafter abbreviated as seawater mixing stabilizing liquid).

(Prior Art) In recent years, with the increase in offshore construction work such as waterfront development work and offshore artificial island development, the need for drilling stabilizing fluid that uses seawater is increasing.

Stabilizing solutions using seawater are usually made by adding fine powder of attapulgite or seviolite, which are said to be salt-resistant clay minerals, to salt-resistant carboxymethyl cellulose sodium salt (hereinafter referred to as CM).
It is known that the product is made by dissolving a substance (abbreviated as C) and suspending it in seawater.

(Problems to be Solved by the Invention) Conventionally known seawater mixing stabilizers often suffer from performance deterioration due to calcium hydroxide, a product of water use reactions, due to the mixing of cement during actual excavation work, and the stability of trench walls is affected. Since the stability cannot be maintained for a long time, it is necessary to replenish or replace the stabilizer with new stabilizer.

The present inventor aims to provide a seawater mixing stabilizer composition that does not use attapulgite or seviolite, which must be imported, and which does not easily lose groove wall stabilization performance when mixed with cement.

(Means for solving the problem) In general, excavation stabilizing fluid has a moderate viscosity, solid fine particles are stably suspended, trench wall stability is achieved, and its properties vary widely due to the presence of cement. It must be satisfied that no change occurs. The present inventor discovered that although montmorillonite clay minerals or kaolinite clay minerals are not stably suspended in seawater,
They discovered that sufficient suspension can be obtained by adjusting the hydrogen ion concentration (hereinafter abbreviated as RH) to 10 to 11.3 by adding and treating low molecular weight polyacrylic acid soda (hereinafter referred to as polyacrylic acid). (abbreviated as "soda") in seawater produces insoluble salts due to the Ca and Mg ions contained in it, reducing or losing its dispersion performance, but in seawater treated with sodium carbonate and/or sodium hydroxide, sodium polyacrylate It was discovered that it exerts its original dispersion function and significantly suppresses deterioration caused by cement contamination. .

The addition of sodium carbonate and/or sodium hydroxide to seawater to precipitate and remove Ca ions and aqueous ions from the aqueous phase as calcium carbonate and magnesium hydroxide, respectively, is a method of removing montmorillonite clay minerals or kaolinite clay minerals. It is effective in increasing the suspension stability of minerals and at the same time exhibiting its function as a dispersing agent for sodium polyacrylate.Furthermore, the calcium carbonate and magnesium hydroxide produced are well suspended in seawater as fine particles, and are also used as specific gravity increasers. This is convenient because it can be done.

In carrying out the present invention, there is no need to particularly limit the degree of substitution or molecular weight of CMC, and any CMC that is commonly used for civil engineering may be used.

Further, as a ground filler and a specific gravity increaser, any fine powder of a montmorillonite clay mineral or a kaolinite clay mineral, which is commonly used in civil engineering work, is suitable. In carrying out the present invention, the average molecular weight of the sodium polyacrylate used as a dispersant is preferably 10,000 or less.

When the average molecular weight exceeds 10,000, the performance of the stabilizer tends to deteriorate due to cement contamination. If the amount of sodium polyacrylate added is less than 0.1 part of seawater, the cement resistance will be insufficient, and if it is more than 0.4 part, the cement resistance effect will not change and it will only become uneconomical.

The reason for limiting the sea-island adjustment range is that when it is less than 10, the removal rate of Ca ions is low and the function of sodium polyacrylate is insufficient, and when it is more than 11.8, the stabilizer performance remains almost the same.

(Effects of the invention) By carrying out the present invention, there is no deterioration of the stabilizing liquid even in the case of a high mixing rate of cement components that can occur in actual excavation work, and processes such as settling, transporting, and separating excavated soil It maintains performance suitable for the excavation work, and there is no need to replenish or replace new stabilizing fluid during excavation work (smooth work execution is possible).

Embodiments of the present invention will be specifically described below.

(Example 1) Seawater 101 was used as a seawater kneading stabilizer based on conventional technology.
After stirring and dissolving 5 g of CMC with a degree of substitution of 1.2 in 00O using a magnetic stirrer, 20 g of attapulgite was added and stirred for 15 minutes with a household mixer. shall be.

Seawater line stabilizing solution B based on the present invention is prepared as follows.

Seawater 100100O! αC4g with a degree of substitution of 1.2
10 g of soda carbonate and 3 g of sodium hydroxide are added to the solution while stirring with a magnetic stirrer. The pH at this time was 11.0, and the liquid was cloudy. Add bentonite (Kunigel V from Kunimine Industries) to this liquid.
l) 20g and 2g of sodium polyacrylate having an average molecular weight of 6000 were added and stirred for 5 minutes using a household mixer.

The properties of the seawater kneading stabilizer A and the seawater stabilizer B obtained in this manner were as shown in Table 1. The values in Table 1 indicate the funnel viscosity, and the amount of water removed and the mud film thickness comply with the API regulations. The results of the filtration test are shown below.

Add 20g of cement and 50ml of water to these seawater mixing stabilizers.
After being left overnight, the viscosity of seawater stabilizer A decreased and the performance of the stabilizer deteriorated as shown in the table below, but seawater stabilizer B did not. It maintains its performance even after being left undisturbed for 4 days.

(Example 2) When sodium polyacrylate is not used in the formulation of seawater stabilizer B in Example 1 and the average molecular weight is 15,000
The seawater line stabilizers using sodium polyacrylate were designated as C and D, respectively, and the properties of these stabilizers were investigated, and as shown in Table 2, they were found to have good performance as a stabilizer. However, when cement was added to these stabilizers in the same manner as in Example 1 and left to stand overnight, the bentonite in both stabilizers C and D coagulated, and the supernatant liquids became quite transparent. It had lost its performance as a stabilizer.

(Example 3) A seawater line stabilizing liquid prepared in the same manner as in Example 1 except that kaolinite clay mineral fine powder (FC powder manufactured by Shoei Sangyo) was used instead of bentonite. The properties of E and the properties after adding cement were as shown in Table 3.

Claims (1)

[Claims] Seawater 100 whose hydrogen ion concentration index was adjusted to 10 to 11.3 by adding soda carbonate or/and caustic soda
part (volume) of carboxymethyl cellulose sodium salt 0.2 to 0.6 parts (weight) and an average molecular weight of 100
Low molecular weight polyacrylic acid sodium 0.1 to 0.00 or less.
A composition for stabilizing a seawater ditch wall for ground excavation, which comprises dissolving 4 parts (by weight) and then suspending 1 to 5 parts of fine powder of a montmorillonite clay mineral or a kaolinite clay mineral.