JPH0142990B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a water stop agent used in underwater excavation methods in civil engineering work and the like.

Underwater excavation methods include the underground continuous wall method and the kaiso foundation method. For example, the underground continuous wall construction method is a construction method in which a wall-shaped trench is excavated underground, using bentonite mud to prevent the wall from collapsing, and a continuous wall made of unreinforced or reinforced concrete is constructed in this trench. When excavation is carried out using this method, if there is a sandy soil layer, a phenomenon occurs in which groundwater springs or bentonite slurry used as a stabilizer leaks into the sandy soil layer.

The present inventor has completed the present invention as a result of various studies aimed at solving these conventional drawbacks. That is, the present invention provides sand stabilizing liquid by adding a water-stopping agent mainly composed of a fibrous substance and neutralized red mud and/or its analogue to the stabilizing liquid and performing excavation. This prevents leakage into the sandy soil layer, and conversely also prevents groundwater from springing up from the sandy soil layer.

The red mud used in the present invention is a residue produced during the production of alumina from bauxite, for example, by the Bayer process. That is, insoluble matter is separated from a sodium aluminate solution obtained by extracting bauxite with an alkaline solution at high temperature. Its composition differs depending on where the bauxite is produced or how it is processed, but generally it includes Al ₂ O ₃ , SiO ₂ , Fe ₂ O ₃ , Na ₂ O,
It contains T ₁ O ₂ and other elements such as CaO, MgO, S, and P. When this material is used, it is neutralized. Neutralization treatment is usually performed by adjusting the pH to 6 to 8. Further, analogs of red mud include slag, blast furnace slag, and the like.

Examples of the fibrous material include waste pulp, waste paper, asbestos, synthetic fibers, pulp fibers such as cotton waste, other vegetable fibers, and chemical fibers.

When a fibrous material and red mud are used in combination as in the present invention, they become entangled with each other to form a three-dimensional network structure. Furthermore, when non-self-hardening cement is used in combination, the water-stopping effect is further improved.

Non-self-hardening cements include cement that is made non-self-hardening by adding a large amount of water to undergo a sufficient hydration reaction, and cement obtained by solid-liquid separation treatment of wastewater discharged from the manufacturing process of cement products. Examples include solid substances contained therein.

When the water-stopping agent of the present invention is used by adding it to a stabilizing liquid, etc., the water-stopping agent of the present invention forms a network structure in the interstices of sandy soil, filling the voids, and fine particles become entangled therein. This can effectively prevent leakage of the stabilizing liquid and gushing of underground water.

The mixing ratio of the fibrous substance and the red mud and/or its analogs used in the water-stopping agent of the present invention may be appropriately selected depending on the soil quality of the construction site where it is used, but in general, the fibrous material red mud and/or
or its analogues are added at 20-40%. Furthermore, the amount of water stop agent added to the stabilizing solution etc. also varies depending on the nature of the soil at the construction site.

As is clear from the above, by using the water stopper according to the present invention in the underwater excavation method, stable liquids such as bentonite mud do not leak into the soil and contaminate groundwater, and vice versa. Since it can also prevent groundwater leakage, it can also prevent a drop in the groundwater level.

EXAMPLES Next, Examples will be given to further specifically explain the present invention, but the present invention is not limited to the following Examples.

Example 1 Red mud 20 pre-neutralized to 100 parts by weight of waste pulp
A water stop agent was prepared by mixing parts by weight.

Example 2 Fibrous material made by putting waste paper into water and stirring it to loosen it
A water stop agent was prepared by mixing 100 parts by weight with 40 parts by weight of red mud that had been neutralized in advance.

Example 3 A water stop agent was prepared by mixing 30 parts by weight of slag with 100 parts by weight of waste pulp.

Example 4 A water stop agent was prepared by mixing 40 parts by weight of blast furnace slag with 100 parts by weight of waste pulp.

Example 5 A water stop agent was prepared by mixing 100 parts by weight of waste pulp with 20 parts by weight of red mud and 20 parts by weight of blast furnace slag.

Example 6 A water stop agent was prepared by mixing 100 parts by weight of waste pulp with 20 parts by weight of non-self-hardening cement and 20 parts by weight of red mud.

Test example: When a continuous underground construction method using bentonite mud as a stabilizing liquid was carried out, the leakage rate of the bentonite mud was 40%.

Further, when construction work was carried out under the same conditions by adding 1% of the water stop agent prepared in Example 1 to the bentonite mud, the leakage rate of the bentonite mud was 5%.

Claims (1)

[Claims] 1. A water stop agent for underwater excavation whose main ingredients are a fibrous substance and at least one selected from neutralized red mud, slag, and blast furnace slag.