Temperature- and Displacement-Dependent Model for unsaturated Earth pressures behind thermo-active retaining walls

Earth pressures behind a thermo-active retaining wall can be influenced not only by the temperature-dependent response of the unsaturated backfill but also by the thermal expansion or contraction of the wall during the cooling and heating operations of a coupled heat pump. Such lateral deformations cause the unsaturated backfill to be placed in an intermediate passive or active state. In this study, an analytical framework is presented to compute the temperature- and displacement-dependent earth pressures of unsaturated soils behind embedded thermo-active retaining walls. The application of the proposed model is demonstrated by comparing its results with those from field-scale tests reported in the literature. A set of parametric studies is performed on a 6-m embedded thermo-active wall backfilled with three hypothetical soils (clay, silt, and sand) at 25 °C, 35 °C, and 45 °C. Further, unsaturated earth pressure profiles are generated for various thermally induced expansions and contractions during cooling and heating cycles. The results show that elevated temperatures decrease passive earth pressure and reduce the depth of tension cracks in at-rest and active states. Additionally, lateral wall expansion during the cooling cycle helps eliminate the tension zone. However, the heating cycle of the heat pump can be critical, as it leads to lateral contraction of the wall, thereby developing a tension-cracked zone, which can negatively affect the system’s efficacy. The presented framework is a useful tool for forensic studies as well as assessing the serviceability of embedded thermo-active retaining walls under working stress conditions by linking geotechnical and structural aspects.