New technical combination of seawater and ultrasound wave energy for excavation of highly plastic sticky clays in urban EPB tunneling

In urban tunneling with an earth pressure balance-tunnel boring machine (EPB-TBM), highly plastic clays or sticky clay containing fine-grained sediments makes tunneling conditions more difficult. The proper amount and consistency of the ground conditioning chemicals to be used for the excavation of these difficult or complex geological units are also controversial. Due to the lack of proper management and optimization of such chemical foaming agents in accordance with the excavation material and tunneling method, some environmental impacts may occur. However, environmental pollution and its effects, in other words, the ecological costs emerged as a result of exposure to these chemicals, can sometimes be ignored. In this study, the use of seawater is proposed as a ground conditioning agent in EPB-TBM operations and the use in addition of ultrasound wave energy application on fine-grained and highly plastic sedimentary clays conditioned with seawater. Preliminary analyses and evaluations of the new eco-technical combination indicate that the seawater can easily compete with existing sodium-based foaming agent (SLES) on a laboratory scale by providing the required dispersive effect, which can be enhanced with ultrasonic applications.