Question

What is the purpose of piles, and why they could be more preferred compared to shallow foundations

Answer 1

when we have to design a foundation for a structure, our first choice always remains shallow foundation from economy point of view. Before foundation,a proper investigation of the soil (mainly bearing capacity and settlement analysis) is done. Some times we encounter with a soil of low bearing capacity and compressible starta at show depth and this bearing capacity goes on increasing with depth..So to take advantage of the hard rock at greater depths below it is always prefered to go for piles rather than shallow foundation. so the purpose of pile lies here "To increase the bearing capacity of soil, partly by friction along the length of pile and partly by tip resistance at base"

they are preffered because they could bear more loads and will transfer it to greater depths where we have hard rocks like soil avaliable..they are prrffered because they could resist horizontal loads also.