Physical modelling of pipe piles under oblique pullout loads usingtransparent soil and particle image velocimetry

CAO Zhao-hu(曹兆虎)¹, LIU Han-long(刘汉龙)^{1, 2}, KONG Gang-qiang(孔纲强)¹, ZHOU Hang(周航)¹

(1. College of Civil and Transportation Engineering, Hohai University, Nanjing 210098, China;
2. Key Laboratory of New Technology for Construction of Cities in Mountain Area,
Chongqing University, Chongqing 400045, China)

Abstract:a small-scale physical modelling method was developed to investigate the pile bearing capacity and the soil displacement around the pile using transparent soil and particle image velocimetry (PIV) technique. Transparent sand was made of baked quartz and a pore fluid with a matching refractive index. The physical modelling system consists of a loading system, a laser light, a CCD camera, an optical platform and a computer for image analyzing. A distinctive laser speckle was generated by the interaction between the laser light and transparent soil. Two laser speckle images before and after deformation were used to calculate the soil displacement field using PIV. Two pipe piles with different diameters under oblique pullout loads at angles of 0°, 30°, 45°, 60° and 90° were used in tests. The load-displacement response, oblique pullout ultimate resistances and soil displacement fields were then studied. The test results show that the developed physical modelling method and transparent soil are suitable for pile-soil interaction problems. The soil displacements around the pipe piles will improve the understanding on the capacity of pipe piles under oblique pullout loads.

Key words:pipe piles; transparent soil; particle image velocimetry (PIV); displacement fields; oblique pullout loads