In tunneling technology, Earth Pressure Balance-Tunnel Boring Machine (EPB-TBM) technology operations require altering excavated soil rheology through soil conditioning, a vital aspect for optimal counterpressure control and soil extraction. This transformation is achieved by introducing additives like foam, and inherits its time-dependent behavior. Having observed a discrepancy in the stability of two foams generated with different flow rates, the core objective of research is exploring the influence of this parameter on time-dependency of mechanical properties of conditioned soil. This aspect is then studied also through a semi-quantitative analysis aimed to investigate correlations between the generation flow rates, the Foam Expansion Ratio, and used Foam Injection Ratio with the time-stability of conditioned soil properties.

During the construction of coastal projects, the formation of seepage channels within the soil body, induced by fluctuating water pressure, can result in consequential damage to the soil structure, ultimately culminating in sudden water gushing sand disasters. In order to investigate the impact of static and dynamic seepage pressures on sand flow and water flow conditions, an intelligent water pressure loading device was devised to consistently apply a confining pressure of 60 kPa to the specimens. The three static seepage pressures and nine fluctuating seepage pressures were applied to the specimens under the condition of constant confining pressure to study the effect of static and dynamic seepage pressures on sand flow and flow conditions. The outcomes of the experiments revealed that, when the base water pressure of the dynamic seepage pressure is the same as the static seepage pressure, the cumulative seepage volume and permeation velocity of the dynamic seepage pressure are always larger than that of the static seepage pressure. Moreover, higher static pressures increase forces on particles, enhancing permeation velocity, and cumulative seepage volume. Notably, longer periods of pressure fluctuations in dynamic seepage pressures and lower basic water pressures weaken the effect of dynamic seepage pressures.