Land reclamation from the sea is increasingly common in coastal areas in China as its urban population continues to grow and the construction of subways in these areas becomes an effective way to alleviate transportation problems. Earth pressure balance shield (EPBS) tunneling in reclaimed lands often faces the problem of seawater erosion which can significantly affect the effectiveness of soil conditioning. To investigate the impacts, in this work, the stratum adaptability of EPBS foaming agents in seawater environments was evaluated based on a series of laboratory tests. The Atterberg limits and vane shear tests were carried out to understand the evolution characteristics of mechanical properties of clay-rich soils soaked in seawater and then conditioned with foams. The results revealed that, for the same foaming agents, the liquid limit and plastic limit of soils soaked in seawater were lower than those in deionized water due to the thinning of bound water films adsorbed on the surface of soil particles. Similarly, soils soaked in seawater had lower shear strength. In addition, the results indicated that the foam volume (FV) produced by foaming agents using seawater as the solvent was slightly higher than that when using the deionized water due to the higher hydration capacity of inorganic salt cations in seawater compared with organic substances. It was also shown that seawater had negative effects on the half-life time (T1/2) and the dynamic viscosity (eta) of foaming agents due to the neutralization reaction between anions in the foaming agents and Na+ present in seawater. The test results also confirmed that 0.5 % of the tackifier (CMC) can alleviate the issue of thin foam films caused by seawater intrusion and improve the dynamic viscosity of foaming agents more effectively, leading to superior resistance to seawater intrusion in EPBS tunnel constructions.

Wildfires are an ever-increasing issue due to the driving forces of climate change. Weather events that lead to higher wildfire potential are likely to increase and thus new fire management methods via more sustainable fire suppressant class A foams rather than retardants are being developed. However, despite their adherence to regulations, foam impact on targeted ecosystems, namely forests and forest trees is poorly studied. We aimed to investigate how three tree species (Pinus sylvestris, Alnus glutinosa and Picea abies) will react to a one-time class A foam application. Two separate trials were conducted. During the first the foam was applied to seeds and during the other - to 1-year-old seedlings. Tree growth and physiological status were evaluated. Stress criteria for cellular damage, non-antioxidant and antioxidant stress response and photosynthesis efficacy were measured. Results showed an obvious species effect, as all three reacted differently. The dose effect was also notable, with the higher application rate leading to a proportionally bigger response. Overall, pines were negatively impacted, spruce were positively affected, and alders didn't experience a notable change. This leads us to conclude that pending the limitation of this experiment the tested foam while phytotoxic in some cases, is unlikely to affect tree survival rates under field conditions and any physiological responses are likely transient in nature.