METHODS OF GROUND IMPROVEMENT - Introduction to Soft Soil Geotechnique: Content, Context and Application - page 221

probably not horizontal, and the fact that geotextiles have a low modulus of
elasticity and are plastic and therefore tend to creep.

Pile-mattress
The pile mattress (Fig 13.13) is a type of load relief structure. The ground
pressure is reduced by a system of mat and piles that carry a part of the loading to
deeper-seated bearing layers. The mat may consist of a geotextile or reinforced grid
(chicken-foot system) which transfers the load to the pile heads, after a certain
settlement has taken place. As an alternative for the mat a mattress of reinforced
soil can be used, where the load transfer is realised by arching. The design of load
relief structures involves many aspects of geotechnical engineering: pile behaviour
(end-bearing and/or friction), settlements, horizontal deformation, arching, geogrid
strength and flexibility, durability and safety factors. Since 2005, a pile mattress
with a geogrid reinforcement and a sludge mixture (renewable material) as fill has
been tested as a relatively cheap and environmentally friendly method for road
foundation on very soft soils (Kyoto Road). The results are positive. The reduction
of the ground pressure is 50%, arching effects increase with time, and the various
available design methods predict reasonably well (van Eekelen).

road foundation road foundation

sand bed sand bed

separation textile separation textile

H H geogrid geogrid

H a H a

fill fill

a a

pile cap pile cap

s s

soft soil soft soil

pile pile

Figure 13.13 Pile mattress

E BIO - CHEMICAL TREATMENT
SmartSoils® are technologies, launched by Deltares, that can direct the
localisation and rate of natural soil processes that influence soil properties. By
influencing these processes, there is real potential to alter the properties of the soil
(for example, permeability and stiffness). Thus, by means of specific biological and
chemical technologies, one can generate soil to suit a desired purpose, such as
changing the natural soil to make it suitable as a foundation for construction. Some
successful examples are:
- Self-cleaning Road. A unique road construction for transformation and
remediation of contaminated dredged material over the lifetime of the road.
- Biosealing. A natural biological process for self-detection and sealing of leakage
in water impermeable barriers.