Development of engineering-geological parameters evaluation system for hydrate-bearing sediment and its functional verification

Engineering-geological parameters are crucial for evaluation of geohazard potential in marine hydrate exploitation. The combination of piezocone penetration and vane shear test may help gain longitudinally continuous and reliable parameters for hydrate reservoir, which has great perspective in integrated engineering and geological field survey. However, application of these techniques to marine hydrate survey has remained vacant so far. To better understand the penetration or shearing behaviors and their influencing factors in hydrate-bearing sediment (HBS), we developed a novel engineering-geological parameters evaluation system, which may satisfy the need of five-bridge piezocone penetration test and vane shear test. The tip resistance, side frictional resistance, excess pore pressure, electrical resistance, and video along the penetration path could be obtained through five-bridge piezocone penetration test. The method of electrical resistivity tomography is firstly combined with piezocone penetration and vane shear technology in this system to explain the relationships between engineering geological parameters and hydrate saturation. The sandy sediment and clayey-silt sediment (free of hydrate) are involved to verify the functions of the system. The results show favorable fitness with the field-obtained data. Repeated experiments show high reproducibility of the data. This system proved the possibility of establishing quantitative evaluation models of engineering geological parameters in HBS, and also provided a basic platform for novel probing device test in the integrative engineering-and-geological hydrate survey.