Development and verification tests of deep-sea sediment-structure interface equipment

The characteristics of deep-sea sediment-structure interface is one of the key problems in the design and calculation of offshore platform structures. However, there is a lack of experimental devices and methods for the characteristics of sea sediment-structure interface. Based on the geotechnical static-dynamic hydraulic triaxial shear apparatus in Dalian University of Technology, a set of structure-soil interface instrument is developed. The development ideas, technical advantages and application methods of the test devices are introduced. The reliability is verified through the tests on the characteristics of undrained deep-sea sediment structure interface under static and dynamic loads. The influences of roughness and dynamic load ICSR on the mechanical behavior and the development law of pore pressure of the interface are preliminarily discussed. The results show that there is no obvious strain-softening phenomenon in the development of the interface stress during the installation process of low roughness pile, while the stress curve shows a trend of strain-hardening under the influences of high roughness. From the pore pressure accumulation curve, the interface soil has experienced the trend of shear shrinkage first and then dilatancy, and with the increase of roughness, the failure surface gradually migrates from the interface to the soil. Under the dynamic cyclic loads, roughness II structure presents pull-up sliding phenomenon with the increase of cyclic times, and along with the accumulation of dynamic pore pressure, the interface presents stiffness-weakening phenomenon. The cumulative plastic strain of the interface tends to be stable when the cyclic times is 300, and finally the normalized dynamic pore pressure of the interface is 0.22. The instrument provides a precondition for the studies on the characteristics and mechanism of deep-sea sediment-structure interface as well as the establishment of constitutive model for the interface.