Proposal of a new sampling and sounding method using vibration for geotechnical investigation of seabed

抄録

In the construction of offshore civil engineering structures or the exploitation of energy and mineral resources in the shallow part of the seabed, it is necessary to investigate mechanical properties of the foundation ground or various characteristics of reservoirs and mineral deposits. Thus, Vibro Sampling and Cone Penetration Test (VS-CPT) was devised for economical and effective submarine geotechnical investigation of the surface layers, about 20 mbsf. To examine an appropriate shape of the probe, model probes were made and driven into the model sand ground. As the results demonstrated that the drivability and sample recovery were not bad when the aperture ratio of the probe, Ra, was 0.5 or higher, a prototype apparatus (Mark 1) was manufactured with Ra = 0.67. Driving test using a vibratory hammer on a saturated dense sand ground, however, revealed that the tip of the sampler was clogged in the surface layer, and the drivability was low. In addition, the cone resistance is found not suitable for sounding as its measured values were zero.