A combined split-spoon sampler and spherical penetrometer: laboratory trials

Abstract

Full flow penetrometers (FFPs) such as T-bar and ball penetrometer provide reliable estimates of undrained shear strength (su) of soft-soil deposits. Several studies are reported in the literature on the field application of these penetrometers for offshore applications typically for the deep-water environment. However, the lack of sampling provision creates problem for identifying the accurate soil type from the load–penetration response. Information obtained from the field samples is vital in determining the stratigraphy and conducting several basic laboratory tests. This study proposes a new sampling-cum-penetration testing device, which uses a split-spoon sampler for sampling with a spherical cutting shoe. The cutting shoe was modified to increase the bearing area for enhanced accuracy in soft deposits. Strength assessment study was conducted in the laboratory using remoulded kaolin clay at various undrained shear strengths. To investigate the occurrence of plugging and the extent of influence zone during penetration, image-based deformation measurement technique was adopted. The modified ball penetrometer shows a strength factor of about 14·3 in remoulded kaolin clay.