Shear behavior of undisturbed expansive soil under plane strain condition subjected to medium strain rate

• Published in: Bulletin of engineering geology and the environment 2024-07, Vol.83 (7), p.281, Article 281
• Main Authors: Gao, Zhiao, Kong, Lingwei, Wang, Shuangjiao, Li, Tianguo
• Format: Article
• Language: English
• Subjects: Behavior; Clay; Consolidation; Deformation; Design engineering; Design parameters; Dynamic loads; Earth and Environmental Science; Earth Sciences; Earthquakes; Expansive clays; Expansive soils; Foundations; Geoecology/Natural Processes; Geoengineering; Geotechnical engineering; Geotechnical Engineering & Applied Earth Sciences; Hydraulics; Hydrostatic pressure; Influence; Investigations; Loading rate; Magnetic resonance; Mechanical loading; Mechanical properties; Nature Conservation; NMR; Nuclear magnetic resonance; Nuclear safety; Original Paper; Plane strain; Pore pressure; Pore water; Pore water pressure; Scanning electron microscopy; Seismic activity; Seismic engineering; Shear strength; Shear tests; Shearing; Soil; Soil mechanics; Soil properties; Strain; Strain rate; Stress state; Triaxial loads; Vibration; Water pressure
• ISSN: 1435-9529; 1435-9537
• DOI: 10.1007/s10064-024-03773-z

Rapid dynamic loads, such as those caused by earthquakes or traffic, induce medium strain rates in expansive soil, impacting its mechanical properties, which are vital for geotechnical engineering design. This study aims to deepen understanding of the rate effect on expansive clay under plane strain conditions. It conducts various isotropic triaxial and plane strain shearing tests at different medium strain rates. Post-testing, the microstructures of the clay, affected by varying shearing rates, are examined using scanning electron microscope and nuclear magnetic resonance. The experimental findings revealed that the strength at higher strain rates surpasses that at lower ones. In addition, the strength under plane strain at the same consolidation stress level exceeds that under triaxial loading. The strain rate effect is more pronounced in the clay studied under low consolidation pressure, which is more significant in the triaxial state than under plane strain. Excess pore water pressure initially peaks at low strain rates before decreasing but increases at higher strain rates. The specimen’s intermediate principal stress coefficient ( b ) rises with the increase in consolidation pressure and strain rate. In addition, the expansion of fissures and changes in internal structure account for the strain rate effect in undisturbed expansive soil under specific loading rates. These new insights aid in better understanding the behavior of expansive clay under medium strain rates, enabling engineers to establish appropriate design parameters and criteria. This ensures the safety and stability of structures under dynamic loading.