1) Akai, K., Yamamoto, J. and Ozawa, Y. (1962): "On the behavior of pore pressure during the shear of saturated clay," Trans. of JSCE, No. 85, pp. 1-6 (in Japanese).
2) Akai, K., Adachi, T. and Okano, M. (1972): "A constitutive equation for soils based on viscoplasticity," Proc. 27 th Annual Meeting of JSCE, Vol. III, pp. 149-152 (in Japanese).
3) Akai, K., Adachi, T. and Ando, N. (1974): "A stress-strain-time relation of saturated clays," Trans. of JSCE, No. 225, pp. 53-61 (in Japanese).