Investigation of long-term behaviour of thermal wall by finite element analysis

Abstract

Energy foundations utilise the natural thermal energy stored underground for the space heating and/or cooling of buildings. This technology can be used for lowering carbon dioxide gas emissions. However, there has been very limited research on the effects of cyclic heating and cooling on the structural performance of thermo-active diaphragm walls (thermal walls). An investigation of the long-term behaviour of a thermal wall is conducted in this study by a finite element analysis. The complex thermo-hydro-mechanical (THM) responses due to the operation of the thermal wall are analysed. With no operation of the thermal wall, the earth pressure and the wall movement change due to the dissipation of the excess pore pressure developing from the construction. However, there is only a small change in the bending moment of the wall. With the operation of the thermal wall, the thermal differential across the diaphragm wall induces thermal strain, and therefore, an increase in curvatures, resulting in an increase in the bending moment compared with no operation of the thermal wall. This study shows the necessity of examining the thermally induced effects of a thermal wall in the design, including variations in the bending moment of the wall, the cyclic changes in the earth pressure acting on the diaphragm wall, and the thermally induced soil shrinkage/expansion.