Cheese-loving habits

Maybe it was waking up for the first time in a student house with a strange-looking housemate, or, for those from the tropical side of the world, the realisation that the sun is indeed capable of setting at nine o’clock at night. Surely the initial shock has been tempered by the frequent, inexplicable rain showers, but either way, from one international student to another: welcome to Delft.

If memory serves, the international introduction week should have equipped you with the basic ‘survival skills’ needed to survive your first weeks. These skills are nothing if not basic, so here are a few from my survival guide.
First, the bike. Get a bike, but not just any bike, a good sturdy bike that can survive the frequent assaults of the weather but yet not too flashy to catch the bike thief’s eye. In safe little Delft, bike crime is about the only kind of crime we have to worry about. But that also means the cops have time to fine you for riding around at night without a bike light. Always make sure you’re equipped with some form of active illumination. Also, start learning how to ride a bike during ‘bike rush hour’.

Right around 8:25 a.m. it’s a free for all on the bike paths on and around the university grounds, so if you doubt your abilities to cut across people’s paths while sending text messages and holding an umbrella all at the same time as you ride, then this no time for you to be on the move.
Second, cheese and bread go with everything. The Dutch are very defensive of their cheese-loving habits. Never come between a Dutchman and his cheese love. And yes, cheese not only goes with every meal, it can in fact be a meal in itself. And bread is usually not too far from the table if there is cheese around. Heck, there’s always bread around. And it’s also a meal in itself. If, as an international student, it seems amazing that there’s a rack dedicated to fifty different types of bread and cheeses, your awe is better saved for something else.

Finally, punctuality: 8 o’clock means 8 o’clock. If you have issues with the clock, 7:50 is good, 8:00 is acceptable, and 8.10…well you may as well get used to meeting with yourself. Punctuality is right up there with cheese on the list of important Dutch things. If you want to start off on the right foot with a Dutchman, (or for that matter to get a chance to even see his foot), be there on time. Welcome aboard.”

Francis Ndonga, from Kenya, is a third-year BSc student studying aerospace engineering. He can be contacted at: fdude85@gmail.com

Delta 30-08-2007
‘If the technique developed by Leon van Paassen works well, houses will no longer sag and trains can rumble over rail embankments without a problem.’ 

Traditionally, when soils need to be stabilized, this is done by various methods, such as injecting cement into the soil – a process called grouting. Such methods are elaborate and expensive, however. For his PhD project, Leon van Paassen investigated the possibilities of flushing sandy soils with solutions of bacteria, ureum and calcium chloride. The bacteria transform the added chemicals into calcium carbonate, which functions as a type of natural cement between the grains of sand. The result: sandstone.

The principle underlying this process, known as biogrouting, had already been demonstrated in laboratories. Van Paassen conducted additional lab research in order to determine, among other things, how much calcium chloride needs to be added to arrive at a certain soil strength, and to test the mechanical properties of the resulting sandstone. Another important aspect of his research was to try and make the process work in larger scale soil experiments. “This turned out quite well”, Van Paassen says. “We conducted a successful experiment with a 5-meter long soil column. After that, we found a contractor who was willing to carry out some additional testing, and we then conducted a successful experiment in which we reinforced the sand in a sandbox measuring 8 x 5 x 2.5 meters.”

Van Paassen also made calculations based on practical applications for this technique, such as, for instance, stabilizing the soil beneath railroad tracks. “It’s a common problem that railroad tracks situated on top of weak soil deform”, Van Paassen explains. “There is for example a stretch of track between Gouda and Woerden with weak soil underneath it, topped with a layer of sand. Trains can only travel over this stretch of track at limited speeds, because otherwise the load of the passing train would deform the soil too much and thereby risk a derailment. I calculated that if you reinforce the layer of sand underneath these tracks using biogrouting, the train could travel over this stretch of track at speeds of up to 20 percent faster.”

There is however a ‘but’: the cost. The raw materials for this type of biogrouting are rather expensive. Plus, when calcium carbonate forms, ammonium chloride is formed as a by product, and this compound needs to be flushed out of the soil after the process is complete, which is also costly. “At the end of my project I looked into alternatives for the current bacterial process”, Van Paassen adds. “It is for instance also possible to use denitrifying bacteria, which leads to less harmful byproducts.” A Dutch company, Deltares, is now continuing the development of this process and trying to find a suitable client and location for a pilot project. Van Paassen is partially involved in this through his research. The rest of his time he spends teaching at TU Delft, where he now holds the position of lecturer.