Living Quicksand
نویسندگان
چکیده
The image of quicksand merciless swallowing a victim has inspired the fantasy of kids and helped writers and moviemakers to get rid of evil figures. Is this really possible? This is still disputed since till today it is not even clear what quicksand exactly is. In soil mechanics, the “quick-condition” is usually described as a liquefaction due to high water pressure essentially possible with any soil. However, previous studies have detected anomalous rheological properties from natural quicksand. Pushed by these contradicting points of view we set off to Lençois Maranhenses in North-East Brazil, where quicksands are common, to investigate rheology and strength in situ. We found that along very quiet drying lakes cyanobacteria cement an impermeable crust above a suspension of grains. Beyond a critical pressure, the crust fails releasing water from the collapsing colloidal structure and radically changing the depth dependence of the shear strength from a constant to a linear function. The sedimenting solid fraction and the rapid increase of shear strength can indeed trap an intruder endangering his life if the basin is sufficiently deep. As opposed to some previous studies, we find that this quicksand condition cannot be restored once it has collapsed. Finally, we also show some preliminary results from a contact dynamics model specially designed to mimic the living quicksand behavior.
منابع مشابه
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The discrete element method constitutes a general class of modeling techniques to simulate the microscopic behavior (i.e., at the particle scale) of granular/soil materials. We present a contact dynamics method, accounting for the cohesive nature of fine powders and soils. A modification of the model adjusted to capture the essential physical processes underlying the dynamics of generation and ...
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تاریخ انتشار 2008