Effects of anti-clay agents on bubble size distribution and stability of aqueous foam under pressure for earth pressure balance shield tunneling

Abstract

The earth pressure balance (EPB) shield inevitably encounters heavy clay soils during tunneling, which form mud cakes on the cutter head. To prevent this, it is necessary to add anti-clay agents to foam agents. However, the effect of anti-clay agents on foam properties and its optimal concentration under different conditions remain unknown. In this study, the bubble size distribution and half-life of foam produced by foam agents and anti-clay agents under pressure were measured and analyzed. The results show that the mean bubble radius decreases with the addition of anti-clay agents at 0 bar but increases at a pressure of 1 bar or 2 bar. The anti-clay agents weaken the stability of foam, and optimal concentrations of anti-clay agents for different test pressures are proposed. The test results obtained provided guidance for selection of the optimal concentration of anti-clay agents to be used in EPB shield tunneling.