2015 秋季期刊

A solid foundation for piled embankments

Suzanne van Eekelen received her doctorate on 1 July at Delft University of Technology for her research into piled embankments reinforced with geosynthetics – and in so doing unveiled a new design model for the reinforcement of piled embankments.  

The application of piled embankments makes road building both quicker and safer. The new design model means further optimisation and application of the piled embankment technology. TenCate produces geosynthetics for constructions with piled embankments. Chris Lawson, managing director of TenCate Geosynthetics Asia, was a member of the doctoral committee.

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During the ceremony 

A piled embankment can be applied when laying a road or railway on a soft substrate with poor load-bearing capacity, such as clay. Because soft soil is compressible, a thick layer of sand is usually first deposited when a road or railway is to be built. The weight of this presses the soft soil together (and possibly outwards), and surface settlement, a process that can last for years, may cause damage to pipes and such features as culverts. Bumps and potholes appear in the road, making driving not only uncomfortable but also unsafe. Furthermore, where railways are concerned, this situation can lead to a derailment. 

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A piled embankment can be built quickly without harming the environment, and result in a stable low-maintenance road 

Arching effect 

A load in the ground tends to bend in the direction of stiffer elements, such as piles. This can cause an arching effect. Via the created ‘arch’, a large part of the load is directly transferred onto the piles. The load part not directly transferred to the piles rests on the geosynthetic material and possibly the underlying subsoil. The arching effect forms the basis of the majority of calculation models for designing geosynthetic reinforcement for piled embankments. The better the arching effect, the more efficient the piled embankment. The reinforcement must be sufficiently deformable, so that the arching effect can develop. The application of geosynthetic (geotextile) reinforcement to a piled embankment improves the arching effect.

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The objective of Suzanne van Eekelen’s research was to gain greater insight into the load distribution in a piled embankment reinforced with geosynthetics, and to develop an analytical calculation model for designing the reinforcement. There are already various design models throughout the world but they deliver different answers, which in turn have consequences for the reinforcement that must be laid – often much more than necessary, sometimes less than required. Designing a piled embankment is no easy matter; it is difficult to determine how strong and stiff the reinforcement must be. 


Reliable model

The new design or calculation model that stems from this doctoral research is much more reliable than existing models. It is now possible to achieve a design that is considerably more accurate, and this will encourage road builders to deploy piled embankments more frequently. This also means more stable and durable roads that can be built faster and require little maintenance. 

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Dr. ir. Suzanne van Eekelen

Representing TenCate Geosynthetics, Alain Nancey, Dick Janse and Jeroen Ruiter were substantively involved in the doctoral research. Suzanne van Eekelen is full of praise for their expertise and contributions. ‘TenCate has grown strongly on the Dutch market over the last few years.’ One of the independent members of the doctoral committee was Chris Lawson, managing director of TenCate Geosynthetics Asia. According to Suzanne van Eekelen, Chris Lawson is recognised internationally as an expert in this field. ‘As a member of the BS8006 committee in the eighties, he set the standard and is still an international topper.’

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Chris Lawson (right)

As he himself says, Chris Lawson has a long history in geosynthetics, particularly in the technology and application of piled embankments. This technology dates back to the eighties in the last century. According to him, the doctoral research of Suzanne van Eekelen also means that recognition and application of piled embankments will increase. ‘It’s a technically complex subject. She has improved the problem analysis and executed it correctly in technical terms. The match between measurements and calculation is convincing, the validation well documented, and so the discipline has moved forward.’ He expects this research to have an impact definitely in Western Europe, and probably internationally as well. ‘Highways and railroads are the driving force behind this technology, and geotextiles make the design more efficient and more cost-effective.’ 


Strategic priority
 

Within the strategy of TenCate Geosynthetics, piled embankments reinforced with geosynthetics play an important role. This infrastructure application currently enjoys priority within the sales strategy of TenCate Geosynthetics: growth in high-grade solutions for infrastructure. A combination of geogrids and geotextiles is a growing trend. The market group has a broad portfolio of geotextiles and geogrids (such as TenCate Geolon® PET and TenCate Miragrid® GX) to meet market demands, and can supply these materials all over the world.


Thesis

Blue fabric (Tecawork Blue 65287)