Delta Life 9

Using the Deltares Large Diameter Sampler (DLDS), project engineer Dennis Peters and his team can calculate the stability of dikes better. C an dikes still protect us adequately from floods or are they in urgent need of upgrading? To test dikes, we need to know which soil layers are present in the subsurface because soft layers such as clay and peat can undermine stability. The larger the soil sample from the subsurface, the better Dennis Peters and his team can calculate the strength of the dike. The newly-developed Deltares Large Diameter Sampler can take a soil sample from depths down to about ten metres below the surface. As the name suggests, the diameter of the samples is larger than in the past. Existing techniques provide samples of up to 65 millimetres; the DLDS produces samples with a diameter of 400 millimetres. Eight old soil samples could fit in one of the new samples. It is also possible to work at greater depths: it was possible to obtain large soil samples before but never from depths of more than about two metres. After drilling, researchers analyse the soil samples in the laboratory and use the measured strength parameters in calculations of dike stability. The results are now much more accurate and so water authorities can tailor dike upgrades accordingly and make major savings. 'This may even be a new market,' says Dennis Peters. 'We recovered the bone of a calf and a medieval pot shard.' LARGE SOIL SAMPLES FOR SAFER DIKES The vacuum switch ensures that air or water can escape from the sampling tube during the operation. When it is closed, the soil sample is kept in the sampling tube. Six hydraulic plungers deliver extra force. The sampler goes into the ground at an angle of 10 degrees. The cylinder contains the sampling tube with the soil sample from soft soil layers such as clay and peat. TESTING GROUND