One of the most pleasant things to do in a summer is to spend a few hours on the beach. Do you aware that there are quite a few geotechnical phenomena while you stay on the beach?
You may see loads of kids building sand castles on the beach. Some of them may use very wet sand and some may use relative dry sand. How to make a strong sand castle? To answer this question, you first need to understand what makes a sand castle stand firmly? It is capillary force produced by water within sand. That is suction coming from surface tension, which holds sand particles together. The finer the sand particles, the stronger the capillary forces. That is why you cannot make gravel castle due to the too big particle sizes. And you cannot make strong sand castle using very wet sand, because there is no capillary force if the sand is saturated by water. There should be both air and water existing within the sand. To make a strong sand castle, the optimum ratio of water to sand by weight is between 1:10-1:5.
In my next blog, I will introduce other geotechnical phenomena on the beach.