Anyone from Nature Physics<\/a><\/p>\n<\/td>\n<\/tr>\n<\/table>\n","protected":false},"excerpt":{"rendered":" Nature Physics magazine explains the secret for building the perfect sand castle – but only 7 people in the world can understand it, and none of them has ever been to the beach… Anyone who has built a sandcastle recognizes … Continue reading ![](\"http:\/\/cyber.law.harvard.edu\/blogs\/static\/dowbrigade\/kastle.jpg\")
Nature
\n Physics<\/em><\/a> magazine explains the
\n secret for building the perfect sand castle – but only 7 people in the
\n world can understand it, and none of them has ever been to the beach…<\/em><\/p>\n
\n who has built a sandcastle recognizes that adding liquid to the sand
\n grains
\n increases
\n the overall
\n stability.
\n However, measurements of the stability in wet granular materials often
\n conflict with theory and with each other. The friction-based
\n Mohr-Coulomb model, distinguishes between granular friction and
\n interparticle friction, but uses the former without providing a physical
\n mechanism.
\n A frictionless model for the geometric stability of dry particles on
\n the surface of a pile is in excellent agreement with experiment. However,
\n the same model applied to wet grains overestimates the stability and
\n predicts no dependence on system size. Here we take a frictionless
\n liquid-bridge model and perform a stability analysis within the pile.
\n We reproduce
\n our experimentally observed dependence of the stability angle on system
\n size, particle size and surface tension. Furthermore, we account for
\n past discrepancies in experimental reports by showing that sidewalls
\n can significantly increase the stability of granular material.<\/p>\n