[H-DS18] 海底地すべりとその関連現象

[HDS18-P03] せん断層形成に伴う砂の孔隙率および浸透率の変化－貯留層と海底地すべりの評価に向けて－

*木村 匠¹、金子 広明¹、野田 翔兵¹、伊藤 拓馬²、皆川 秀紀¹ (1.国立研究開発法人産業技術総合研究所メタンハイドレートプロジェクトユニット、2.国立研究開発法人産業技術総合研究所（現・地球環境産業技術研究機構）)

キーワード：せん断層、孔隙率、浸透率、孔隙径分布、砂層、リングせん断

As a part of a Japanese National hydrate research program (MH21, funded by METI), we performed a study of porosity and permeability changes due to shear zone development in sandy sediment. It is key factor to investigate the characteristics of fault and slip surface in seafloor for the evaluation of gas/oil reservoir and landslide. In this study, to reveal the relationship shear zone development and porosity/permeability change in sand, the shear and permeability tests under constant normal stress were carried out by ring-shear device, and microstructures and grain size analyses were conducted in the samples taken from the shear zone of the specimens after shearing tests. The permeability and porosity after shearing decreased with increasing effective normal stress values in the range of 0.5-8.0 MPa and stress dependency of permeability and porosity was clearly found. On the other hands, the change of permeability and porosity during shear at the effective normal stress of 8.0 MPa was investigated. The permeability and porosity drastically decrease with increasing shear displacement. And the examinations of shear rate effect on permeability at 8.0 MPa were conducted by 2-20 mm/min. The shear rate effect was not significant at tested shear rate range. These are reflected by the porosity reduction, pore size distribution and grain size reduction due to grain crushing in a localized shear zone.