<p>Geothermal heat pump systems are increasingly integrated into urban infrastructure due to their potential for reducing carbon emissions and energy consumption. Diaphragm walls, commonly employed as retaining structures in deep excavations, offer dual functionality when equipped with thermal exchange systems. This study investigates the long-term thermo-mechanical behavior of insulated diaphragm walls in geothermal applications, analyzing their response to seasonal heating and cooling cycles over a 30-year period using PLAXIS 2D. A numerical model based on the Dean Street Station project in London was developed to simulate various thermal conditions. The model incorporated soil-structure interaction, thermal insulation, and geothermal heat pump operation under winter and summer cycles. Results show that thermal insulation on the excavation side stabilizes internal wall temperatures and reduces mechanical deformation. Thermally activated diaphragm walls with insulation offer promising potential for sustainable geotechnical design. The findings support the optimization of energy geo-structures by evaluating the long-term effects of temperature fluctuations on mechanical integrity.</p>