Ground Improvement Business

Business Outline
Ground Improvement Technologies
Fudo Tetra Technologies
ICT Ground Improvement

Foundation of Ground Improvement
Pioneer of the Sand Compaction Pile Method

In 1956 Fudo Tetra was first in the world to develop the sand compaction pile method, which is now the most common method of ground improvement.
We have continued research and development since that time, and now as experts in geotechnical engineering
we have a wealth of design and implementation technologies and long experience in installation work.

All types of structures—buildings, roads, bridges and so on—are built on the ground. The condition of the ground is not fully apparent to the naked eye. To preclude damage from subsidence, landslips and similar threats to built structures, a thorough understanding of the nature of the ground is essential to prepare it for the type of structure to be built on it. In 1956 Fudo Tetra succeeded in developing the sand compaction pile method (traded as the Compozer method) as a world-wide first, and since then has used its expertise to develop many ground improvement technologies, contributing to ground preparation both in Japan and overseas.

Overseas activity of Fudo Tetra Corporation

Ground Improvement Technologies

Settlement Reduction Stability Increase Liquefaction Mitigation Water Cutoff Walls Building Foundations Others

Problem:

When ground is highly compressible, problems such as consolidation settlement or negative friction on piles occur. There are concerns that, after building is finished, subsidence in the ground could cause a structure to tilt or underground pipes to be damaged.

Answer:

Settlement countermeasures (improving compressibility): Example:
Advance completion of consolidation settlement through sand columns and advance earth filling equivalent to the load of the structure.

Suitable Methods

Problem:

In weak ground, such issues as slipping failure of earth fill, loss of foundation bearing capacity, wall stability problems or inadequate lateral resistance of piles occur. Slippage damage occurs because the foundation ground lacks shear strength.

Main countermeasures:

Stability increase (improvement for shear characteristics): Example:
Shear strength of weak ground is boosted by mixing methods etc.

Suitable Methods

Problem:

When the friction force binding together sand particles in low density sandy ground breaks down due to seismic shaking, the ground becomes sand floating in water and this phenomenon is called liquefaction.
Liquefaction can cause the subsidence or tilting of structures.

Countermeasure:

Liquefaction mitigation: Example:
By installing large-diameter well compacted high-density sand piles in loose sandy ground, the ground is stabilized, mitigating liquefaction.

Effect:

Effect of liquefaction countermeasures in ground damaged by seismic shaking:
* Great East Japan Earthquake, Tohoku, 2011

In the Great East Japan Earthquake of 2011, liquefaction occurred over a wide expanse of 42km2 of reclaimed land in the Tokyo Bay area.
However, it was confirmed that no damage was suffered at locations where Fudo Tetra had undertaken ground improvement work.

Built facilities

Outside area of improved ground

Area of ground improved by Fudo Tetra

See details: River embankments

Outside area of improved ground

Area of ground improved by Fudo Tetra

Highways

Outside area of improved ground

Area of ground improved by Fudo Tetra

● Great Hanshin Earthquake (1995)

In the Great Hanshin Earthquake of 1995, liquefaction occurred widely in areas of loose sandy soil along coastal zones and in reclaimed land such as Port Island and Rokko Island in Kobe, causing considerable structural damage. However, there were no reports of liquefaction in areas of improved ground where Fudo Tetra had implemented compaction methods, despite the very strong seismic shaking.

Kobe Port Island

Outside area of improved ground

Area of ground improved by Fudo Tetra

Outside area of improved ground

Area of ground improved by Fudo Tetra

Close

Main Countermeasure Methods

Problem:

In locations adjacent to rivers where the groundwater level is high, raised water level outside the embankment causes water pressure to rise and flooding then occurs.

Countermeasure:

Water Cutoff: Example:
Cutting off water to the permeable layer beneath an embankment prevents a rise in water level in the ground inside the embankment.

Methods:

Problem 1

Concerns are raised that voids may develop under foundations or uneven subsidence may occur in the surrounding ground due to piles damaged by liquefaction or post-liquefaction ground subsidence.

Countermeasure 1

For both pile foundations and ground improvement: Example:
Ground improvement of the liquefaction layer prevents liquefaction occurring during an earthquake and also increases lateral resistance of the piles, reducing the cost of foundation piles.

Problem 2

Concerns are raised that when lengthy supporting piles are needed the cost increases, and additionally that if liquefaction occurs piles may be damaged and consolidation settlement may lead to negative friction.

Countermeasure 2

Spread foundations: Example:
Spread foundations through ground improvement are a measure to combat insufficient support, settlement and liquefaction. If subsidence is not a problem, improvement can be taken to middle layer, saving on costs.

Main Countermeasure Methods

Total Re-soil System

Construction-generated soil from digging operations, concrete rubble from demolition work, or upheaved soil from sand pile installation is recycled locally for effective use as compaction material for ground improvement work with a Compozer, or as lightweight mixed soil.
Soil or rubble generated on site is usually transported off site for disposal, but this system avoids this transportation cost and its impact on the local environment. It also avoids the cost of purchasing and transporting sand or other compaction material plus the environmental impact of its extraction and transportation.

Outline of Total Re-Soil System

Eco-Gaia-Stone

Earth Pile Foundations and Ground Improvement

A new filling material for use in the sand compaction pile method, made from steel industry slag. Grain size and expansion rate are controlled.
Coastal Development Institute of Technology validation #10001
NETIS registration KTK-140002-A

〔Eco-Gaia-Stone Features〕

Has the same compactability and ease of use as sand materials
Possible to control consolidation quality by hydraulic regulation
Environment-friendly
Controls expansion stability

Fluidized Sand

A material in which anion-type fluidizing agent L1, and cation-type plasticizing agent P1 that has the effect of aggregating the fluidizing agent, are mixed with sand. This material delivers fluidity due to L1’s ability to hold water, allowing passage through pipes and installation in the ground, the generation of an internal friction angle when compacted in the ground, and loss of fluidity after implementation. It has frequently been used as a liquefaction countermeasure in confined locations with the SAVE-SP method. It’s also a material that can possibly be used for filling voids after pile extraction etc.

Fudo Tetra’s Technologies

Consolidation, drainage and compaction Consolidation Acceleration Compaction Solidification Water Cutoff Lightweight Soil Drainage Others