The stabilization of slurry properties in slurry shield tunneling is the key to form a slightly permeable filter cake on the excavation surface and to effectively balance the soil-water pressure in the ground. The deterioration of slurry properties due to seawater intrusion is mainly caused by the high salt concentration, especially the concentration of divalent cations such as Ca²⁺, Mg²⁺, etc. To address the issue of the deteriorating slurry properties due to seawater, study on the effects of adding sodium carbonate, ethylenediaminetetraacetic acid (EDTA), and xanthan gum were conducted to a slurry with bentonite to seawater ratio of 3:50. Variations in slurry density, Marshall's funnel viscosity and 2 h bleeding rate were measured. The experimental results indicate that: The addition of sodium carbonate increased the slurry density, while EDTA and xanthan gum alone have minimal impact on the slurry properties. However, when EDTA and xanthan gum were added with a ratio of 10:1, the 2 h bleeding rate of the slurry decreased by 50%. The characteristic particle size d₈₅ of the particles in the slurry and their zeta potential test results showed that the stability of the slurry and its colloidal properties were less relevant. The complex addition of EDTA and xanthan gum significantly improved the stability of the slurry, because EDTA chelated divalent cations in the seawater, which restored the thickening capacity of xanthan gum. The results are important guidelines for the development of cation-resistant thickeners to enhance the stability of seawater slurries.

The use of a phase change material (PCM) encapsulated in a steel ball in place of the coarse aggregate in concrete can improve the energy density and heat transfer in the energy pile which will reduce the underground space needed for the heat transfer. Cooling-heating loads are used in a traditional concrete energy pile and a PCM energy pile in a container containing unsaturated clay to experimentally study the thermal response of the piles and surrounding soil. The results show that the temperature influence range in the soil surrounding the phase change pile extends out to about 1.5 times the pile diameter during the cooling-heating processes with a larger temperature difference between the PCM energy pile inlet and outlet than with the traditional concrete energy pile, which indicates a larger heat transfer rate. The temperature differences in both the PCM pile and the traditional pile during heating are less than during cooling which shows that the heat transfer rates during cooling are larger than during heating for the same flow conditions. The results also show that the PCM increases the uneven temperature distribution during the cooling in the vertical and horizontal directions in the pile. In addition, irreversible settling of unsaturated clay is observed at the soil surface due to temperature induced soil consolidation and drainage.