Tapered piles are a type of piles with a variable cross-section

which can effectively improve the skin friction of the piles. Thus far

however

little effort has been made to investigate the installation effect of the tapered piles. By using transparent soil materials and the particle image velocimetry (PIV) technique

a series of model tests is conducted to investigate the soil displacement of the surrounding soil in installing a tapered pile. The displacement field of the surrounding soil is determined by analyzing the distinctive laser speckle pattern generated by the interaction between the laser and transparent soil when the light goes through the transparent soil. The images of the laser speckle pattern is obtained by CCD (charge-coupled device) camera and analyzed using the PIV technique. For comparison

a model test on the installation of a constant cross-section pile is also carried out and analyzed. Finally

this result is compared with those of the model test on the installation of a variable cross-section pile and the cavity expansion theory

showing the accuracy and reliability of tapered pile installation model test using transparent soils. The results show that the model test on installing a tapered pile in transparent soil can effectively simulate the installation process of a tapered pile

and the radius of influence due to tapered pile installation is found to be about 1.2 times that of the equal section pile installation.