A series of centrifuge model tests was conducted to estimate parametrically effects of the following factors on earth pressure and deformation of buried flexible pipes: pipe flexibility, pipe installation type, ground condition, and three burial dimensions (cover height, ditch width and bedding thickness). The tests yielded accurate measured data of circumferential distributions of normal and tangential earth pressures on the model pipes, circumferential distributions of bending strains in the pipe wall, and vertical pipe deflection, fully quantifying the effects of the investigated factors. It was found that Japanese current design standards, based on Marston-Spangler theory, do not conform to the test results by ignoring the effects of almost all the factors on the earth pressures, and, as a result, they specify definitely unsafe design values of bending moment and pipe deflection for the case when the pipes are buried by the open excavation method using sheet-piling.