Preparation Of Soft Clay For Bearing Capacity Of Model Tests And Study On Installation Of Suction Caissons

Suction caisson is a new style of offshore platform foundation. Although it has been installed in various locations around the world, understanding of the concept is still limited. The main investigations consist of the following parts.In order to investigate the bearing capacity of model caissons, it is necessary to prepare soft clay which is used for laboratory experiments. For this purpose, we constructed two large deposits of soft clay. One of them is homogenized clay, and the strength of the other sample is increasing with depth. During the preparation, Settlement of sample and weight of evacuated water were monitored to control water content of the model clay. The results of the vane shear test, used to measure the clay foundation's shear strength, are also briefly analyzed.Second, a series of caisson installation tests were undertaken in homogenized soft clay. The penetration resistance, required pressure and allowable pressure developed during caisson's penetration are presented. Some comparison analysis was made between the results of the analytical predictions and the measured results. Good comparison was found between measured allowable underpressure and predictions. The calculated limit aspect ratio was found to be 2.9% to 19.2% higher than the measured. The friction factor was back calculated using data recorded from experiments. The penetration resistance measured during self-weight penetration produced an alpha factor between 0.12 and 0.19 while the test installed by suction produced an alpha factor between 0.35 and 0.4.Finally, we conducted lab experiments to study the bearing capacity of suction caissons. Two kinds of model caisson made of stainless steel with diameters of 76mm and 114mm were used for model tests. They had an aspect ratio of six and four, respectively. The performance of suction caissons under three kinds of load inclination angle and the failure mode were presented. The paper also includes a description of experimental facility and the testing procedure.