Expert: Veto Varma - 7/29/2006

Question
Hello Mr. Varma,  I pass by construction sites where   they are driving piles either for building foundations or highway foundations.  My question is that I see the piles are made of concrete (reinforced no doubt) and I was wondering why the concrete doesn't crumble or crack under the repeated impacts of the driver?  It would seem that if the pile was slightly bowed or had any flaw the pounding would cause it to deteriorate.   Thanks.

Answer
Hello,

What you see is impact driven concrete piles. These piles are either prestressed or precsat concrete piles and braced against lateral buckling. The pile hammer is aligned to hit the pile straight and a cushion is provided on top of pile. Again pile top is braced for impact either by steel top or thick concrete so it is not crushed at the top. Lateral buckling of the pile depends on the length of pile that is controlled in the design process. Usually the alignement of hammer and impact is now very well advanced but still we do see some pile failures during piling, in that case pile is replaced.

Regards
Veto