Research on evaluation of sustainable capacity of large-scale civil engineering

Large-scale civil engineering should be sustainable, but Sustainable capacity of it can not evaluate by certain method till now. Emergy method and ecological footprint method based on ecology are the direction of sustainable evaluation method. But two of them can not be directly applied to civil engineering. Emergy method take energy as the basis of comparison, however it only can identify input and output of ecosystem energy without limit. Ecological footprint can give direct result by the impact that human impose on ecosystem, whereas its disadvantage lies in exaggerating environment pressure. On the foundation of two methods, Emergy-feedback footprint method integrates the advantages of them. The first, it use energy unit as comparing limit and distinguish consumption emergy, pollution emergy and output emergy ; the second, take ecological capacity as a limit, ldquofeedback output landrdquo variable is brought forward; The third, civil engineering sustainable capacity is defined and judgment criterion is provide. In addition, calculation module and procedure are put forward. Finally scientificity and utility of it is proved by Huning expressway example.