from the life-is-a-beach dept.
John R. Gillis writes in the NYT that to those of us who visit beaches only in summer, beaches seem as permanent a part of our natural heritage as the Rocky Mountains but shore dwellers know that beaches are the most transitory of landscapes, and sand beaches the most vulnerable of all. Today, 75 to 90 percent of the world’s natural sand beaches are disappearing, due partly to rising sea levels and increased storm action, but also to massive erosion caused by the human development of shores. The extent of this global crisis is obscured because so-called beach nourishment projects attempt to hold sand in place(PDF) and repair the damage by the time summer people return, creating the illusion of an eternal shore. But the market for mined sand in the US has become a billion-dollar annual business, growing at 10 percent a year since 2008. Interior mining operations use huge machines working in open pits to dig down under the earth’s surface to get sand left behind by ancient glaciers.
One might think that desert sand would be a ready substitute, but its grains are finer and smoother; they don’t adhere to rougher sand grains, and tend to blow away. As a result, the desert state of Saudi Arabia brings sand for sandblasting all the way from Australia. Huge sand mining operations are emerging worldwide, many of them illegal, happening out of sight and out of mind, as far as the developed world is concerned. "We need to stop taking sand for granted and think of it as an endangered natural resource," concludes Gillis. "Beach replenishment — the mining and trucking and dredging of sand to meet tourist expectations — must be evaluated on a case-by-case basis, with environmental considerations taking top priority. Only this will ensure that the story of the earth will still have subsequent chapters told in grains of sand."
A study led by Assistant Professor Darren Chian Siau Chen from the Department of Civil and Environmental Engineering at the National University of Singapore's Faculty of Engineering has found that when a projectile is fired at a sand block at high speed, it absorbs more than 85 per cent of the energy exerted against it. This ability to resist the impact increases with the speed of the projectile, even at high velocities.
While sand has been used traditionally for military fortification, very little is known about the unique energy absorption capability of the material. In a recent study, a team of researchers from the National University of Singapore's (NUS) Faculty of Engineering found that sand can absorb more than 85 per cent of the energy exerted against it, and its ability to resist the impact increases with the speed of the projectile, even at high velocities. In contrast, steel plates have poorer energy absorption capacity against high speed projectiles. This novel finding suggests that sand can potentially be used as a cheaper, lighter and more environmentally friendly alternative to enhance protection of critical infrastructure as well as armour systems.
[Editor's note: We've previously discussed an impending shortage of sand..]