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Creep Behavior and Long-Term Strength Evolution of Unsaturated Red-Bed Mudstone Fill: Matric Suction Regulation and Viscous Response Modeling.

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Bibliographic Details
Title:	Creep Behavior and Long-Term Strength Evolution of Unsaturated Red-Bed Mudstone Fill: Matric Suction Regulation and Viscous Response Modeling.
Authors:	Yin, Fengjie¹ (AUTHOR) 22110347@bjtu.edu.cn, Cai, Guoqing² (AUTHOR) guoqing.cai@bjtu.edu.cn, Liu, Hengshuo³ (AUTHOR), Mi, Minghao¹ (AUTHOR) 22110342@bjtu.edu.cn, Li, Jian³ (AUTHOR) jianli@bjtu.edu.cn
Source:	Journal of Geotechnical & Geoenvironmental Engineering. Jul2026, Vol. 152 Issue 7, p1-18. 18p.
Subject Terms:	Mudstone, Creep testing, Geotechnical engineering, Soil moisture, Durability, Viscoelasticity
Abstract:	Understanding the creep behavior and long-term strength evolution of unsaturated fill materials is a key scientific challenge for ensuring the long-term stability and serviceability of high embankment subgrades. Red-bed mudstone, widely used as a fill in western China, exhibits significant time-dependent deformation under unsaturated conditions, posing potential risks to the structural performance of geotechnical infrastructures. In this study, a series of multistep triaxial creep tests was conducted under controlled matric suctions (100, 200, and 300 kPa) using an unsaturated Global Digital Systems (GDS) triaxial testing system. The axial strain, volumetric strain, creep rate, and rate sensitivity characteristics of unsaturated red-bed mudstone were investigated systematically. Three approaches were adopted to determine the long-term strength: the normal isochronous curve identification (NICI) method, the isochronous strain rate (ISR) method, and a newly proposed peak strain rate (PSR) method. The applicability and consistency of these methods were compared to determine the dominant role of matric suction in affecting the long-term strength formation. Furthermore, viscous coefficient and average viscous coefficient parameters were introduced, and an SLogistic1-based evolution model was developed to capture their variation against suction, stress, and time. Results demonstrate that matric suction exerts a synergistic strengthening effect by enhancing structural stability, suppressing deformation rate, and improving the long-term strength. The average viscous coefficient serves as a key input parameter for constitutive modeling and long-term performance prediction of unsaturated soils. The findings provide theoretical guidance and parameter support for long-term deformation control and serviceability assessment of high-fill subgrades constructed with unsaturated red-bed mudstone fill. [ABSTRACT FROM AUTHOR]
Database:	Energy & Power Source

Description
Abstract:	Understanding the creep behavior and long-term strength evolution of unsaturated fill materials is a key scientific challenge for ensuring the long-term stability and serviceability of high embankment subgrades. Red-bed mudstone, widely used as a fill in western China, exhibits significant time-dependent deformation under unsaturated conditions, posing potential risks to the structural performance of geotechnical infrastructures. In this study, a series of multistep triaxial creep tests was conducted under controlled matric suctions (100, 200, and 300 kPa) using an unsaturated Global Digital Systems (GDS) triaxial testing system. The axial strain, volumetric strain, creep rate, and rate sensitivity characteristics of unsaturated red-bed mudstone were investigated systematically. Three approaches were adopted to determine the long-term strength: the normal isochronous curve identification (NICI) method, the isochronous strain rate (ISR) method, and a newly proposed peak strain rate (PSR) method. The applicability and consistency of these methods were compared to determine the dominant role of matric suction in affecting the long-term strength formation. Furthermore, viscous coefficient and average viscous coefficient parameters were introduced, and an SLogistic1-based evolution model was developed to capture their variation against suction, stress, and time. Results demonstrate that matric suction exerts a synergistic strengthening effect by enhancing structural stability, suppressing deformation rate, and improving the long-term strength. The average viscous coefficient serves as a key input parameter for constitutive modeling and long-term performance prediction of unsaturated soils. The findings provide theoretical guidance and parameter support for long-term deformation control and serviceability assessment of high-fill subgrades constructed with unsaturated red-bed mudstone fill. [ABSTRACT FROM AUTHOR]
ISSN:	10900241
DOI:	10.1061/JGGEFK.GTENG-14431