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

Thesis (M.Eng.) - Asian Institute of Technology, 1969

This report presents the results of a laboratory investigation of the influence of strain rate on the effective stress-strain behavior of saturated Soft Bangkok Clay. Undisturbed samples were taken from depths of 23 to 27 ft. and 17 to 19 ft. below the existing ground surface at the new AIT site at Rangsit. Consolidated-undrained triaxial compression tests were performed on 1.4 in. diameter and 2.8 in. long specimens at three different strain rates, viz. 0.0012, 0.00024 and 0.000048 in. per min. The samples were either isotropically, normally consolidated or overconsolidated before shearing. Pore pressure was measured in all tests from the base of the specimen. The results indicated that in the isotropically, normally consolidated samples, the undrained shear strength increases with increasing strain rate, and that the excess pore pressure is lower in fast tests. In the isotropically overconsolidated samples, the undrained shear strength is higher in the fast tests; however, the difference in the deviator stress between fast tests and slow tests decreases with increasing overconsolidation ratio. The excess pore pressure is lower in fast tests for samples with overconsolidation ratios of 2 and 4. However, the excess pore pressure is-lower in slow tests of samples with overconsolidation ratios of 8 and 16. The effective angle of shearing resistance 5 of both the normally consolidated and overconsolidated clay decreases by 1.2° when the strain rate is decreased from 0.0012 to 0.00048 in per min. The cohesion intercept c of the overconsolidated samples decreases slightly when the strain rate is decreased.