This research aims to study the variation of the undrained shear strength values of Bangkok Clays from different interpretation methods. The study areas include Chulalongkorn University, Kasetsart University and AIT campus. The testing programs consist of 2 field tests: Field Vane test (FV) and Standard Penetration Test (SPT), and 2 laboratory tests: Unconfined Compression test (UC), and Consolidated Isotropically Undrained Compression triaxial (CIUC). The undisturbed Bangkok clay specimens were collected from the soft clay layer until the first sand layer of Bangkok subsoils. The totally 44 undisturbed samples, which are consisted of 29 soft to medium clay samples and 15 stiff clay samples, were tested in laboratory for each test. The testing results were interpreted based on well-known theoretical and empirical methods to determine the undrained shear strength values. These values were then compared among each others to investigate the variations from each test. The results indicate that the FV test provide the highest value of the undrained shear strength following by the CIUC test and the UC test respectively. The SPT N-values could be evaluated using linear regression analysis to indicate the relationship with the undrained shear strength values. Additionally, the results could also be used to determine the relationship of the undrained shear strength values toward the effective vertical stress as well as the undrained Young’s modulus at 50% of yield strength.
