The Architecture Puzzler
Created by Dave Guadagni
Solution to Last Week's Puzzler
Architecture Puzzler #246
Clay soils are sticky (cohesive) and can be excavated to a much steeper angle than sandy soils. This cohesion is partially due to the size and shape of its particles. Clay particles are small and flat shaped. Sand particles are larger and rounder. If a clay particle were the size and shape of a sunflower seed, would a medium-size sand particle be, proportionally, about the size of a golf ball? A basketball? Ten feet (3 meters) in diameter? Or 100 feet (30 meters) in diameter?
Relative to a sunflower seed-sized clay particle, the sand particle would be 100 feet (30 meters) in diameter. Part of the cohesion of clay soils is due to particle-to-particle attractions that are the result of electrical charges on the faces of microscopic minerals. This does not occur between sand particles.
Dave Guadagni, AIA, is an architect with Robertson/Sherwood/Architects
Quizzical Pursuit is Copyright 2005, Dave Guadagni.
Excavating for a New York subway.