JPH0641691B2 - Underwater embankment method with self-hardening sand - Google Patents

Description

The present invention relates to an underwater embankment method using self-hardening sand for forming a hardened sand embankment on the water bottom for the foundation of landfills, offshore structures, and tunnel excavation. .

(Prior art and its problems) Generally, when embankment is carried out on the bottom of a lake or sea, a large amount of sand is used as an embankment material, and this is poured from the water to settle to form a sandy layer on the bottom of the water. Is commonly used.

In recent years, a method for excavating a sloped road from the land to the seabed in an embankment that fills the coast has been developed in the construction of an undersea tunnel, and sand is also used as the embankment material.

When such an embankment made of sand on the bottom of the water is poured from above the water and laminated on the bottom of the water, a sand ground having an N value of about 5 is obtained. Such a sand ground has the drawbacks that the water permeability is high and the bearing capacity is small due to the large gaps between sand particles, and this drawback is most manifested in the liquefaction phenomenon during an earthquake. Further, constructing a structure on such an embankment has a drawback that the amount of settlement is large.

Further, when the tunnel is excavated in such an embankment, the face is likely to collapse, and the shield excavator cannot be used.

Methods for improving these drawbacks include compaction by sand compaction piles and so-called deep-layer mixing processing in which cement milk is poured into the ground and stirred, but these are all uneconomical because they are improved after embankment. There is a problem that is.

In addition, a method of mixing a hardening material such as cement milk or a separation preventing material into the embankment material and pouring it into water at the time of embankment can be considered, but this cannot be directly applied to a sandy embankment material having large particle gaps. That is, in order for the embankment material to harden, it is a condition that the embankment material particles can be solidified with a hardening material, and the presence of fine-grained soil plays an important role in this solidification. If fine particles are not contained at all, or even if they contain a very small amount, if an attempt is made to obtain a predetermined strength, a part of the hardened material will be consumed as void filling material. It is uneconomical to increase. Furthermore, the strength of the ground after hardening increases to the same level as mortar, and it is almost impossible to control the strength arbitrarily. There were problems such as not being suitable for.

(Object of the invention) In view of the conventional problems as described above, the present invention is a method for embankment on the bottom of a water using sand containing no or only a small amount of fine-grained soil (clay content, silt content). Not to mention the construction of structures on the embankment, excavation of tunnels in the embankment, etc. Underwater embankment method with self-hardening sand that gives the desired strength according to the application of the embankment. For the purpose of providing.

(Means for Achieving the Purpose) The underwater embankment method using sand of the present invention for achieving the above object is to mix embankment sand, a gap filling material, a hardening material, and a separation preventing material, and then add water and knead them. And a step of charging the kneaded product into water and embankment on the bottom of the water.

(Function) In the underwater embankment method using sand, the gap between the sand grains is filled by mixing the fine granular gap filler with the sand, and therefore the amount of the hardening material such as cement for binding these is small. In this case, the curing is performed, and the strength after curing is changed by adjusting the mixing amount of the curing material.

(Example) Next, the Example of this invention is described.

A typical construction process of the method of the present invention is as follows.

(1) The powder of the hardening material, the gap filling material and the separation preventing material is dried and mixed with the sand.

(2) Add water to the above mixture and stir to make it viscous.

(3) Carry it by loading it on a transport machine such as a dump truck or a bottom opening barge.

(4) Embankment At the site of construction of the embankment, it is put directly from the water or put on the bottom of the water using a tremie pipe, and piled on the bottom of the water to make the embankment of the desired height.

As the hardening material, ordinary Portland cement, blast furnace cement, slaked lime, or the like is used.

As the gap filler, clay such as clay sand, fly ash or rock powder can be used.

Further, as the separation preventing material, a material for adding tackiness such as a mixture of a polysaccharide-based substance and an inorganic calcium salt which are usually used for underwater concrete can be used.

Typical examples of the composition of these embankment materials are as follows.

Sand 1500 kg Cement 100 〃 Separation preventive material 20 〃 Gap filler 50 〃 Seawater 450 〃 The uniaxial compressive strength of the embankment created by this composition after 14 days was 1.5 kgf / cm ² .

(Effects of the Invention) The underwater embankment method using self-hardening sand of the present invention is configured as described above, and a gap between sand grains is formed by mixing a hardening material such as cement and a fine-grained gap filler with sand. Clogging occurs, self-hardening can be obtained even if the amount of hardener is reduced, and the strength after hardening can be freely adjusted by adjusting the amount of hardener mixed, making it suitable for embankment applications. Accordingly, the required embankment can be obtained easily and economically.

In addition, the sand does not separate at the time of charging and has good fluidity when deposited on the bottom of the water, and moreover, the mixture as the embankment material has good peelability from other objects, and thus has good workability.

Claims (3)

[Claims] 1. A step of mixing embankment sand, a gap filling material, a hardening material, and a separation preventing material, and then adding water thereto and kneading the mixture.
An underwater embankment method using self-hardening sand, which comprises the step of placing the kneaded product in water and embanking it on the water bottom. 2. The underwater embankment method using self-hardening sand according to claim 1, wherein the gap filler is at least one selected from clay sand, fly ash, and rock powder. 3. An underwater embankment method using self-hardening sand according to claim 1, wherein the hardening material is one or more selected from ordinary Portland cement, blast furnace cement and slaked lime.