The effect of climate change on the behaviour of thermo-active diaphragm walls

Abstract

Energy geo-structures are becoming more common as a renewable energy solution which utilises shallow geothermal energy to provide heating and cooling to buildings and civil infrastructure projects. Previous studies have shown that diaphragm walls subjected to combined thermo-mechanical loading show overall increases in lateral displacements, bending moments, shear forces, axial forces, and settlements on the retained side with thermal cycles. This study uses a variation of a validated numerical model to predict the behaviour of thermo-active diaphragm walls in the longer-term including accounting for the influence of climate change under contrasting RCP2.6 and RCP8.5 scenarios. This numerical model also assesses the impact of different modelling assumptions on the model output by comparing a simplified (isothermal boundary condition) model with a more complex model where atmospheric temperatures affecting ground temperatures are included, to inform the interpretation of physical model test data which typically use isothermal (simplified) boundary conditions. The results from this study show increases in lateral displacement, maximum bending moments, positive and negative shear forces and axial forces (compressive and tensile). Significantly, the RCP2.6 model shows that these increases begin to stabilise over the 50-year period modelled, while under RCP8.5, values continue to increase linearly at the end of the modelling period. The study also demonstrates the importance of capturing realistic model boundary conditions in long term studies. The more simplified model underestimates lateral displacements and internal stresses. The underestimation of lateral displacements is significant as this is the main driver of settlements on the retained side of the wall and has been identified as one of the most critical factors affecting long term performance of thermo-active embedded retaining walls.