Objective: As a novel foundation pit support system, a permanently integrated prefabricated diaphragm wall exhibits two mutually constrained characteristics: single-wall bearing and fully prefabricated production. However, these characteristics demonstrate a significant trade-off relationship: the structural volume must be increased to enhance structural mechanics capacity, which adversely impacts the efficiency of the prefabricated production and construction supply chain. Meanwhile, improving supply chain efficiency requires reducing the structural volume or material consumption, which compromises the structural mechanics capacity of the single-wall system. Traditional structural performance evaluations typically rely on a single evaluation metric, failing to synergistically balance mechanical properties and supply chain efficiency for identifying optimal integrated solutions. Given the escalating scale of engineering projects in the complex geological environment, there is an urgent need to develop a novel integrated performance evaluation model to provide actionable guidance for the design decisions of high-strength, low-carbon structural solutions. Methods: This study first establishes a theoretical flexural-load-bearing performance evaluation model based on mechanical experiments. Subsequently, a carbon emission assessment model is developed based on the analysis of the construction process. Using these models, a "mechanical-carbon" dual control evaluation framework is formulated specifically for the permanently integrated prefabricated diaphragm wall system to quantify carbon emission efficiency—defined as construction-related carbon emissions per unit of flexural-load-bearing performance. Finally, a comparative analysis of carbon emission efficiency is conducted between the permanently integrated prefabricated diaphragm wall system and a conventional permanently separated structural system using this dual control model. Results: Research findings indicate that, utilizing single-wall load bearing, the permanent-temporary integrated prefabricated diaphragm wall achieves higher flexural-load-bearing performance than the dual-wall separated system, with performance increasing by 74.5 kN·m (an increase of 4.55%) during the construction stage and 426.5 kN·m (an increase of 26.05%) during the service stage, attributable to the use of high-strength prefabricated concrete. Concurrently, thanks to the removal of a temporary support, average carbon emissions per ring (calculated as the CO₂ equivalent) are reduced by 8.05 t (a decrease of 30.99%). Meanwhile, the solid permanent-temporary integrated prefabricated diaphragm wall exhibits 81 kN·m (an increase of 5.07%) higher flexural-load-bearing capacity than cavity-containing configurations and incurs an additional carbon emission of 1.21 t (an increase of 6.98%). Further dual control evaluation reveals that the cavity-containing configuration exhibits 0.2 t (a reduction of 1.81%) lower carbon emissions per unit flexural-load-bearing performance than the solid configuration, indicating that the carbon emission efficiency of the scheme with the cavity configuration is better. Conclusions: This study demonstrates that the cavity-optimized permanently integrated prefabricated diaphragm wall configurations outperform the solid permanently integrated prefabricated diaphragm wall and conventional permanently separated structural systems in terms of carbon emission efficiency, achieving equivalent flexural-load-bearing performance with reduced carbon emissions and resource consumption. This research further indicates that, in the future, more key indicators can be integrated to establish a more complete and adaptive decision-making performance evaluation framework and method for underground structure construction technology. This research offers a scientific evaluation methodology for high-performance, low-carbon construction technologies in the complex geological environment, advancing the green transformation of underground engineering practices.