A thesis submitted in partial fulfilment of the requirements for the degree of Master of Engineering, School of Civil Engineering

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

This thesis is one of the programs of the international co-operation between Asian Institute of Technology (AIT) from Thailand, Hokkaido University (HU) and Port and Harbour Research Institute (PHRI) from Japan. The purpose of this international co-operation for this thesis is to map out the shear modulus profile at small strain by seismic cone penetration test and correlated it to the parameters from dilatometer test and electric cone penetration test. Otherwise the shear modulus will also be estimated as empirical equation from void ratio, e0 and effective overburden pressure, av' which are available in a routine site investigation. For the test site, this program focuses on soft clay deposited Bangkok clay which will be the database which this co-operation has derived from the different clays worldwide. The represented site of Bangkok clay were performed at two sites, which are Nong Ngoo Hao (NNH) and Asian Institute of Technology (AIT) site. The seismic cone penetration test performed at Bangkok clay, can provide the shear modulus at small strain with well coincided with laboratory bender element test. There were the unique correlation between shear modulus by seismic cone penetration test to the parameters to dilatometer and cone penetration test. An empirical relationship, G 1 = Ae.-1.s av 05 (kPa) (Shibuya and Tanaka, 1996) and G 1 = A( 1 + e 0 ) - 2 .4 av ' 0 · 5 (kPa) (Shibuya, Hwang and Mitachi, 1996), were used as platform empirical for Bangkok clay, for which A is the constant, e0 extended over a range between 1 and 5, and the overconsolidation ratio ranged roughly between 1 and 2. The constant A of Bangkok clay were about 5,000-6,200 and 25,950-31,200, respectively. The correlation between GsCPT to Eo and GsCPJ' to ( q, - a vo) for normally or lightly overconsolidated Bangkok clay, were proposed the constant of these unique correlation as 10-11 and 61-78 ,respectively. Otherwise the correlation between shear modulus and undrained shear strength proposed in the form of rigidity index (Gf/Su) by field vane shear test, dilatometer test and constant volume direct shear, were similar and the rigidity index spreads range between 400- 600 at soft clay layer.