THE INFLUENCE OF OFF-CENTER HITTING ON THE SIGNALS IN HIGH STRAIN DYNAMIC TEST

It is very easy to lead to off-center hitting when the gravity center of hammer and the top of the pile is not right or the drop hammer device frame is not vertical in a high strain dynamic test,which then produces a significant impact on the signals of sensors that are on a hammer and the side of a pile. This paper made simulation study of offcenter hitting for high strain dynamic test piles based on two different installation methods of sensors; it was analyzed in detail the reasonableness of two kinds of high strain dynamic tests and their correct installation schemes with an emphasis on the effects of off-center hitting to the speed of each part and strain of the pile. The simulation explains the phenomena found in the practice such as the strain severely affected by off-center hitting,and less impact on the speed,which corrects the misconception that big piles need more sensors to over the impact of the off-center hitting.