A thesis submitted in partial fulfillment of the requirements for the degree of Master of Engineering of the Asian Institute of Technology, Bangkok, Thailand

Thesis (M.Eng.) - Asian Institute of Technology, 1977

This thesis presents the results of an investigation on the effect of rate of loading on the triaxial compressive shear strength of Soft Rangsit Clay. Undisturbed samples were taken from 4.50 m to 6.00 m below the existing ground level at a site at the Asian Institute of Technology. Anisotropically consolidated triaxial tests were performed on 5.13 cm diameter by 10.16 cm high specimens. In-situ effective pressures and pore pressures were used as consolidation pressures and back pressures, respectively. The samples were generally sheared undrained under strain-controlled and load-controlled conditions. In addition, some undrained creep tests and drained tests were also run. It was found that the undrained shear strength of Soft Rangsit Clay decreased with time to failure, while the drained shear strength appeared to be independent of rate of loading. The Skempton's pore pressure parameter A at failure of undrained tests was found to increase with time to failure. The peak values of normalized excess pore ·pressure had an average of 0.4 and appeared independent of rate of loading. The creep test results showed that the higher the shear stress applied on the samples, the shorter will be the time to failure. The axial strain during creep predicted using Sample's equation and that of Singh and Mitchell agreed well with the experimental data for tests with shear stress below the yield value. There appeared to be a relationship between the creep strain rate and creep rupture life.