JP3244496B2 - Backfill material for underwater construction and underwater construction method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a backfill for underwater construction.

[0002]

2. Description of the Related Art When constructing artificial shores and shores and shores and seawalls where thick, soft clayey soil is deposited, and when constructing or repairing quays or seawalls, it is necessary to prevent uneven settlement after the formation or repair. In order to reduce the amount of subsidence, lightweight embankment material below the water surface and backfill material in the water behind the revetment are needed.
For example, in Japanese Patent No. 2,864,301, the locally generated soil is adjusted so that the contents of clay and silt are increased, and then a cement-based solidifying material, a thickener, and a foaming agent are added, and the underwater construction is performed. It is described that a backfill material is manufactured and is cast at a casting speed of 75 cm / sec or less. In this technology, a thickener is added to the backfill material,
Also, by placing at a flow rate of 75 cm / sec or less, separation of the backfill material in water is prevented. In addition, since there are few locally generated soils having a high content of clay and silt of 80% or more, as described in the 49th Annual Scientific Meeting of the Japan Society of Civil Engineers, pages 1518 to 1519, It is known to incorporate commercially available bentonite.

[0003]

However, when the flow velocity of the backfill material is set to a low speed, the number of constructions decreases, and the cost required for the construction increases. In addition, if the distance of the backfill material moving in water becomes particularly long, the separation resistance in water may decrease.Therefore, even when the movement distance in water is long, a backfill material having high separation resistance may be used. Requested. Also,
Thickeners are relatively expensive compared to other components, so even if the amount of thickener added is small or no thickener is added, a backfill material with high separation resistance in water can be obtained. Requested.

[0004] It is an object of the present invention to provide an underwater backfill material having a high resistance to underwater separation.

According to the present invention, a muddy water containing at least 15% by weight of solid content of one or more clays selected from the group consisting of bentonite, metakaolin and apatalgite, and a cement milk are separately prepared. And a cement milk, which are obtained by kneading, and have a high resistance to separation in water, and a backfill material for underwater construction, and wherein the backfill material is poured into water. It relates to an underwater construction method.

The inventor of the present invention added cement milk prepared separately from the muddy water to a muddy water containing 15% by weight or more of a specific type of clay such as bentonite, and kneaded to mix the backfill material. I got When this backfilled material was poured into water and subjected to a separation resistance test in water, it was found that the pH of water was prevented from rising to the alkaline side, and the amount of suspended matter in water was significantly reduced. I found it. Furthermore, even if this backfill material is cast in water at a high speed of 150 cm / sec, the dispersion in density, strength, and water content after solidification in water is significantly suppressed, and the separation resistance in water is significantly improved. The inventors have found that the present invention has been achieved.

The reason why such remarkable effects are obtained is not clear. However, in muddy water in which bentonite clay is dispersed, for example, it is considered that the bentonite particles repel each other. When the cement milk is added here, the cations contained in the cement milk quickly diffuse into the mud. The action of the diffused cation neutralizes the repulsive force of bentonite,
It is considered that the bentonite particles aggregate, and at this time, other solid components also aggregate.

The solid content in the muddy water may be locally generated soil, or commercially available landfill or backfill soil. The present invention is particularly economical in that it can be applied to locally generated soil such as dredged soil. The type of soil is not particularly limited. Geotechnical Society Standard (JGF M1
11-1990), according to the engineering classification method of soil (Japan Unified Soil Classification Method), soil is roughly divided into clay components (particle diameter 5 μm).
), Silt (particle size: 5 μm-74 μm), sand (particle size: 74 μm-2 mm), and gravel (particle size: 2 mm or more). The soil to be treated in the present invention preferably contains a total of 30% by weight or more of a clay component and a silt component.

[0009] The clay selected from the group consisting of bentonite, metakaolin and apattalite preferably comprises more than 10% by weight of solids in the muddy water, more preferably more than 15% by weight; Particularly preferably, it accounts for 25% by weight or more. Although there is no particular upper limit of this ratio, when it is necessary to add and mix clay selected from the above group to locally generated soil and the like, from the viewpoint of economic efficiency, it is preferably 50% by weight or less. .

[0010] Bentonite, metakaolin and apattalite may be contained in one kind, two or three kinds. Among them, from the viewpoint of resistance to separation in water, bentonite and apatalite are more preferable, and bentonite is more preferable.

As the cement constituting the cement milk, there can be used a cement cement which is generally known as a cement for solidifying the ground, a Portland cement, a blast furnace cement and the like.

When the water content in the muddy water is 100 parts by weight, the solid content is preferably 15-60 parts by weight. The content of cement in cement milk is 1
It is preferably 0 to 30 parts by weight, and the water content is 5 parts by weight.
Preferably, it is -30 parts by weight.

The backfill material of the present invention may contain additives such as a thickener and a foaming agent. These additives are
It may be added to the mud or to the cement milk. Further, the order of addition of each component when producing the muddy water is not limited, and the order of addition of each component when producing cement milk is not limited.

[0014]

EXAMPLES (Experiment A) Each backing material of Example 1 of the present invention and Comparative Example 1 was produced. Concretely, the dredged soil off Haneda was used temporarily. The water content is 41% by weight, the sand content is 35% by weight, the silt content is 44% by weight and the clay content is 21% by weight. 170 kg of this soil, 630 kg of water and 50 kg of bentonite were mixed to obtain muddy water. Separately from this, 120 kg of cement-based solidifying material (ground improvement solidifying material for high water content "TABLOCK 6" (manufactured by Sumitomo Osaka Cement Co., Ltd.), 72 kg of water, and a foaming agent "Synthetic surfactant Sumishield" A "(manufactured by Sumitomo Osaka Cement Co., Ltd.) was mixed to obtain cement milk, and the muddy water and cement milk were kneaded to obtain a backfill material of Example 1 of the present invention.

On the other hand, 170 kg of soil, 702 kg of water and 50 kg of bentonite as in Example 1 of the present invention were mixed, and 120 kg of the same cement-based solidifying material as in Example 1 of the present invention was added thereto. The same foaming agent was added and kneaded to obtain a backfill material of Comparative Example 1.

[0016] The "water-inseparable concrete manual" (Coastal Development Technology Research Center) "water separation resistance test" was followed. Specifically, 100
800 cc of water was placed in a 0 cc beaker, 230 g of the backfill material was divided into 10 equal portions or more, and the mixture was waited for 3 minutes. Thereafter, 600 cc of water was collected from the beaker, and its pH and suspended substances were measured. In the "Underwater-Inseparable Concrete Manual", concrete 5
00 g is put into the beaker. Since the density of concrete is 2.3 tons / m ³ , 500 g is 217 c
c. By making the volume of the backfill material approximately equal to 217 cc, it is necessary to prevent water from overflowing from the beaker. Here, the density of the backfill material is 1.05 ton / m ^3.
Therefore, 230 g is equivalent to 219 cc.

As a result, in the backfilled material of Example 1 of the present invention, p
H was 8.1 and suspended material was 11 ppm. The suspended solids were measured according to "JIS K0102" Industrial wastewater test method ". In the backfill material of Comparative Example 1, the pH was 12.6, and the suspended material was 36500 pp.
m.

As described above, the backfilling materials of the inventive example 1 and the comparative example 1 have exactly the same mixing ratio of soil, water, cement-based solidifying material, bentonite and foaming agent. Nevertheless, in Comparative Example 1, when the backfill material was put into water, the material was separated, the water in the beaker was mixed with the charge, the water was suspended, and the pH increased. On the contrary,
In Example 1 of the present invention, the separation resistance in water was remarkably improved, the pH did not increase, the amount of suspended substances was very small, and the recent strict water quality standards were satisfied.

(Experiment B) Each of the backfill materials of Invention Example 1 and Comparative Example 1 of Experiment A was cast in water. Specifically, a 500 liter water tank holds 400 liters of water,
100 liters of each backfill material was cast at a driving flow rate of 150 cm / sec. In addition, the backfill materials of Comparative Example 1 and Inventive Example 1 were collected for reference and cured in the air (Reference Example). With respect to the backfill material of each example, the distributions of density, strength, and water content were measured, and are shown in Table 1.

[0020]

[Table 1]

The reference example of "air curing" is the average value of the measured values of the backfilled materials of Example 1 of the present invention and Comparative Example 1, but there was almost no variation between them. When the backfill material of Comparative Example 1 was cast in water, the material was separated in water, and the density, strength, and water content varied greatly. That is, the material is separated in water, the soil and the solidified material settle at the bottom of the water tank, the density and strength at the bottom are increased, and the water content is low. On the other hand, in the upper part, which is mainly composed of those that have settled after floating in water, the density and strength have become smaller and the water content has become higher. This seems to be because the casting flow velocity is relatively large. Conversely, when the backfill material of the present invention example 1 was cast in water, the density, strength,
It is considered that the variation of the water content ratio is small and a substantially uniform ground is generated. In Example 1 of the present invention,
The density and water content are larger than those in the case of air curing.
This is probably because water entered the air bubbles during curing.

(Experiment C) In the same manner as in Inventive Example 1, backfill materials of Inventive Examples 2, 3 and Comparative Examples 2, 3, and 4 were produced. However, each clay shown in Table 2 was used instead of the bentonite used in Example 1 of the present invention. In addition,
"Dried clay" is "Sumi clay" (manufactured by Sumitomo Osaka Cement Co., Ltd.). Then, for each backfill material, the separation resistance in water was tested in the same manner as in Experiment A, and the pH and suspended substances in water were measured. The results are shown in Table 2.

[0023]

[Table 2]

As described above, in the case of using the bentonite, metakaolin, and apatalgite in the mixing ratio of the experiment A, the pH of water is particularly remarkably lowered to the neutral side, and the suspended matter is reduced. found.

(Experiment D) The amount of bentonite added in muddy water was variously changed as shown in Table 3, and
5, 6, and 7 backfill materials were obtained. Specifically, 170 kg of soil and 630 kg of water, the same as in Example 1 of the present invention, and each amount of bentonite shown in Table 3 were mixed to obtain muddy water. Separately, 120 kg of the same cement-based solidifying material as in Example 1 of the present invention,
72 kg of water and the foaming agent of each amount shown in Table 3 “Synthetic surfactant Sumishield A” (manufactured by Sumitomo Osaka Cement Co., Ltd.)
Was mixed to obtain a cement milk. Next, the muddy water and cement milk were kneaded to obtain each backfill material. In addition, a backfill material of Comparative Example 5 to which no bentonite was added was obtained. The underwater separation resistance of each backed material was tested in the same manner as in Experiment A. Table 3 shows the results.

[0026]

[Table 3]

When no bentonite was added, as in Comparative Example 1, the pH increased and the amount of suspended solids increased. In contrast, in Example 4-7 of the present invention, remarkable improvements were observed in both pH and suspended substances. In Invention Examples 4-7, when bentonite accounts for 15% by weight or more of the solid content in the muddy water (Invention Example 5-7), a further improvement is seen and accounts for 25% by weight or more. (Example 6 of the present invention,
7) showed a further improvement.

[0028]

As described above, according to the present invention, it is possible to provide a backfill material for underwater construction and a method for underwater construction having high resistance to underwater separation.

────────────────────────────────────────────────── ─── Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI E02F 7/00 E02F 7/00 D // C04B 111: 74 C04B 111: 74 (72) Inventor Hideo Takahashi 7 Toyo, Koto-ku, Tokyo -5-8 ESTEC Corporation Tokyo Branch (56) References JP-A-5-106224 (JP, A) JP-A-60-141989 (JP, A) JP-A-11-35361 (JP, A) JP JP-A-8-260454 (JP, A) JP-A-9-144058 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) E02D 15/10 C04B 14/10 C04B 25/02 E02B 3 / 18 E02F 7/00

Claims (2)

(57) [Claims] 1. A muddy water containing at least 15% by weight of a solid content of at least one clay selected from the group consisting of bentonite, metakaolin and apattalite, and a cement milk are separately prepared. A backfill material for underwater construction, which is obtained by kneading milk and has high resistance to separation in water. 2. A slurry containing at least 15% by weight of a solid content of at least one clay selected from the group consisting of bentonite, metakaolin and apattalite, and a cement milk; An underwater construction method comprising kneading milk and producing a backfill material for underwater construction having high resistance to underwater separation, and placing the backfill material into water.