In the realm of geotechnical engineering, the calculation of undrained strength and deformation of saturated soils has long been a contentious and complex issue. However, a recent study published in *Yantu gongcheng xuebao* (Journal of Geotechnical Engineering) by SONG Erxiang from the School of Civil Engineering at Tsinghua University, Beijing, China, aims to demystify this critical topic. The research delves into the intricacies of undrained soil behavior, offering insights that could significantly impact the energy sector and other industries reliant on stable foundation design.
SONG Erxiang’s study systematically explores the challenges and contradictions surrounding the calculation of undrained strength and deformation. He begins by discussing the total stress method and effective stress method for undrained analysis, highlighting their respective limitations. “Regardless of the method used, it is crucial to distinguish between the two types of pore water pressures and those of the total stresses,” SONG emphasizes. This distinction is fundamental to accurate calculations and engineering applications.
One of the key contributions of the study is the examination of Skempton-Henkel’s formula for calculating excess pore pressure under different stress paths. By combining this formula with the Mohr-Coulomb (MC) strength criterion, SONG proposes an undrained strength model for saturated soils. This model provides a more nuanced understanding of soil behavior under isotropic and anisotropic consolidations, offering valuable guidance for selecting strength parameters in engineering calculations.
The study also addresses the practical implications of using the consolidated undrained strength index (CU index) in various engineering scenarios. SONG warns that direct use of the CU index can lead to significant errors, particularly in calculating the bearing capacity of foundations. “Only when the total stress path in the soils is the same as that in the tests for determining the CU index, this index can be directly used for calculation to give accurate results,” he explains. This insight is crucial for ensuring the safety and economy of foundation designs in the energy sector, where accurate calculations are paramount.
Moreover, the research proposes new methods for calculating bearing capacity and short-term settlements of saturated foundations. These methods, based on a deep understanding of the influencing mechanisms, offer more accurate predictions under both drained and undrained conditions. The proposed formula for bearing capacity, in particular, can enhance the safety and economic efficiency of foundation designs, a critical factor for energy infrastructure projects.
SONG’s study also tackles the issue of the inclination angle of the sliding surface when undrained ultimate soil pressures occur, a topic that has puzzled many in the field. By providing a comprehensive analysis, the research offers clarity and practical solutions to this longstanding challenge.
The implications of this research extend beyond theoretical advancements. For the energy sector, where stable and reliable foundation designs are essential for infrastructure projects, the findings offer a more accurate and efficient approach to geotechnical calculations. This can lead to improved safety, reduced costs, and enhanced project outcomes.
As the energy sector continues to expand and evolve, the need for precise and reliable geotechnical engineering methods becomes increasingly critical. SONG Erxiang’s research represents a significant step forward in this field, providing valuable insights and practical solutions that can shape future developments. By addressing the complexities of undrained soil behavior, the study offers a foundation for more accurate and efficient engineering practices, ultimately benefiting the energy sector and other industries reliant on stable foundation design.