Cost reduction of diaphragm wall excavation using air foam and case record

A novel stabilizing liquid using air foam rather than bentonite clay slurry, i.e. an air foam suspension method, was employed in order to stabilize the trench wall surface during a diaphragm wall excavation. This method reduces the construction costs of working on an underground diaphragm wall. An air foam suspension is created by mixing excavated soil with air foam made from a surfactant. The performance of the air foam suspension depends on its density and consistency, that is, its table flow value (TF). By comparing the trench stabilization capacity of an air foam suspension with that of bentonite clay slurry in model tests, the performance of air foam suspension was confirmed. A cost evaluation of the use of air foam suspension for diaphragm wall excavation is presented with an actual trial construction case record, which shows the superiority of air foam suspension to bentonite clay slurry as a stabilizing liquid.