Closed-Form Models for Nonisothermal Effective Stress of Unsaturated Soils

2020

E3S Web Conf.

Self Cite

Near-surface unsaturated soils can be exposed to elevated temperatures due to soil-atmospheric interactions under drought events, wildfires, heatwaves, and warm spells, or the heat induced by emerging geotechnical and geo-environmental technologies such as geothermal boreholes and thermally active earthen systems. Elevated temperatures can affect the hydro-mechanical characteristics of unsaturated soils, which in turn can alter lateral earth pressures developed in the backfill soil. The main objective of this study is to quantify the effect of elevated temperatures on active and passive earth pressures of unsaturated soils. For this purpose, the paper presents the derivation of an analytical framework to extend Rankine’s earth pressure theory to account for the effect of temperature under hydrostatic conditions. The equations are derived by incorporating the effect of temperature into the soil water retention curve and a suction stress-based effective stress representation. The proposed effective stress equation considers the temperature-induced changes in the contact angle, surface tension, and enthalpy of immersion. To investigate the impact of temperature on active and passive earth pressures, the proposed method is then used in a set of parametric studies to determine active and passive earth pressure profiles for three hypothetical soils of clay, silt, and sand at different temperatures. Results suggest that elevated temperatures can cause variation in active and passive earth pressures for all the soils considered. The findings of this study can contribute toward analyzing earth retaining structures subjected to elevated temperatures.

Section: Resultsmentioning

confidence: 99%

Section: Temperature-dependent Suction Stress Profile Versus Depth Unmentioning

confidence: 99%

Section: Temperature-dependent Suction Stress Profile Versus Depth Unmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Effect of Elevated Temperatures on Lateral Earth Pressures in Unsaturated Soils

Thota

2020

E3S Web Conf.

Self Cite

“…Temperaturedependency of matric suction is accounted for by quantifying the role of temperature on the surface tension, soil-water contact angle, and adsorption by the enthalpy of immersion. Similar formulations are employed by Vahedifard et al (2018b) and Vahedifard et al (2019) to consider the effects of temperature on the SWRC and effective stress, respectively.…”

Section: General Functional Formmentioning

confidence: 99%

Temperature-Dependent Model for Small-Strain Shear Modulus of Unsaturated Soils

J. Geotech. Geoenviron. Eng.

Thota

Cao

et al. 2020

Self Cite

Near-surface soils in geotechnical and geoenvironmental applications are often unsaturated, and natural or imposed changes in temperature may lead to a softening effect at constant suction that causes a change in stiffness. To capture thermal effects on the stiffness of unsaturated soils, this paper presents an effective stress-based, temperature-dependent model for the small-strain shear modulus of unsaturated soils, with an emphasis on silts. Temperature dependency of the model is accounted for by employing temperature-dependent functions for matric suction and effective saturation characterized using the soil-water retention curve. To validate the proposed model, laboratory tests using a modified triaxial apparatus with bender elements are carried out on Bonny silt to measure the small-strain shear modulus at 23 and 43°C for varying matric suctions of 0 to 110 kPa. The results from the proposed model are in a reasonable agreement with the experimentally measured values, and demonstrate the importance of considering temperature effects on the shear modulus of unsaturated soils. The accuracy of the model is further validated by comparing the predicted values with laboratory test results on silts reported by two independent studies reported in the literature.

Thermo‐hydro‐mechanical modeling of unsaturated soils using isogeometric analysis: Model development and application to strain localization simulation

Shahrokhabadi

Cao

Num Anal Meth Geomechanics

2019

SummaryThis study presents a thermo‐hydro‐mechanical (THM) model of unsaturated soils using isogeometric analysis (IGA). The framework employs Bézier extraction to connect IGA to the conventional finite element analysis (FEA), featuring the current study as one of the first attempts to develop an IGA‐FEA framework for solving THM problems in unsaturated soils. IGA offers higher levels of interelement continuity making it an attractive method for solving highly nonlinear problems. The governing equations of linear momentum, mass, and energy balance are coupled based on the averaging procedure within the hybrid mixture theory. The Drucker‐Prager yield surface is used to limit the modified effective stress where the model follows small strain, quasi‐static loading conditions. Temperature dependency of the surface tension is implemented in the soil‐water retention curve. Nonuniform rational B‐splines (NURBS) basis functions are used in the standard Galerkin method and weak formulations of the balance equations. Displacement, capillary pressure, gas pressure, and temperature are four independent quantities that are approximated by NURBS in spatial discretization. The framework is used to simulate strain localization in an undrained dense sand subjected to plane strain biaxial compression under different temperatures and displacement velocities. Results show that an increase in the displacement rate leads to reduction in the equivalent plastic strain while an increase in the temperature leads to an increase in the equivalent plastic strain. The findings suggest that the proposed IGA‐based framework offers a viable alternative for solving THM problems in unsaturated soils.