Drained Peak and Residual Interface Shear Strengths of Fine-Grained Soils for Pipeline Geotechnics

Abstract

This study presents the results of interface torsional ring shear tests conducted at intermediate normal stress levels that are usually prevalent at soil–pipeline interfaces under near-shore conditions. Four normally consolidated soils of different plasticity and five solid surfaces with diverse roughness were utilized in this single-stage shear testing program. The drained peak and residual soil and interface shear strengths were measured and compared with the relevant data available in literature. The analyses and interpretation of the study results revealed that the drained peak and residual interface efficiencies (i.e., the ratio between soil and interface friction angles) are almost equal. These efficiencies can be estimated using one simple correlation that is valid regardless of the effective normal stress range. The correlation helps in the preliminary estimation of pipe–fine-grained soil shearing resistance when the beta (or effective stress) approach is adopted.