Cone penetration tests (CPTU) at Orkdalsfjorden test side, mid Norway

Earthquake induced cyclic loading has the potential to destabilize submarine slopes either by liquefaction in coarse-grained deposits or by cyclic softening in cohesive sediments. Vibratory cone penetration tests (VCPTU) represent a new approach for the evaluation of cyclic softening in fine grained sediments. In the past, VPCTU were utilized to evaluate liquefaction potential of sands, but cyclic softening of fine-grained marine sediments has not yet been tested with VCPTU in situ. At the study site in Orkdalsfjord, mid Norway marine clayey silt deposits are interbedded with coarse silt and clay layers. Static and vibratory CPTU were performed down to 19 m penetration depth using the Geotechnical Offshore Seabed Tool (GOST) and in addition, two gravity cores were taken for cyclic triaxial testing and geotechnical index tests. From static and vibratory CPTU a number of coarse silt layers with a distinct drop in cyclic cone resistance were identified. […]

地震引发的周期性荷载有可能通过粗粒沉积的液化作用或通过粘性沉积物的周期性软化作用，导致海底斜坡的不稳定。振动圆锥贯入试验（VCPTU）是评估细粒沉积物周期性软化的新方法。在过去，VPCTU被用于评估沙土的液化潜力，但尚未使用VCPTU进行原位测试以评估细粒海洋沉积物的周期性软化。在挪威中部奥克达尔斯峡湾的研究现场，海洋粘土质粉砂沉积层与粗粉砂和粘土层互层。使用地球工程技术海上海底工具（GOST）进行了直至19米贯入深度的静态和振动CPTU测试，此外，还采集了两个重力岩心以进行周期性三轴测试和地质指标测试。从静态和振动CPTU测试中，识别出多个粗粉砂层，其周期性圆锥阻力有显著下降。