Model study on refined interpretation of internal friction angle of marine soil based on CPTu

The Cone Penetration test (CPT) has become an increasingly widely used and cost-effective method for determining marine soil properties. The internal friction angle, a critical indicator of shear strength, has been predicted from CPT data by numerous studies. However, existing methods for predicting the internal friction angle are prone to significant errors and generalized conditions of use. This study proposes a method for calculating the internal friction angle of various soil types based on CPT data, in conjunction with Soil Behavior Type (SBT) maps, and validates it with experimental data. The reliability and potential applicability of this method are also investigated. The results demonstrate that: (1) Marine sediments in the Ningbo area are predominantly silty clay and muddy clay, with considerable variation in stratigraphic distribution; (2) The internal friction angle of marine soils is generally proportional to grain size and inversely proportional to the SBT index; (3) A new method capable of classifying soils and accurately predicting the angle of internal friction of different soil types is presented; (4) The prediction results show that approximately 91.7% of data points fall within a 30% error margin, and about 72.5% fall within a 15% error margin, significantly outperforming existing models.