Evaluating the feasibility of muck from slurry shield tunnels as a growth medium for landscaping

Abstract

ABSTRACT Muck from slurry shield tunnels (MSST) is a complex mixture. Directly transporting this muck to dumping grounds not only increases the costs but also raises environmental concerns due to its unusual properties. In this study, a formula has been studied that can turn the MSST into an environment friendly soil. The treatment process can realize the harmless disposal and effective utilization of MSST. In the laboratory study, three different types of growing media (MSST, MSST with 1% fly ash, and local garden soil) were used to grow ryegrass in a series of pot experiments, and the seed germination, chlorophyll content, root characteristics, root activity and physical and chemical properties of the growing media were examined. The results showed that MSST and MSSTF (MSST with added fly ash) can be used as a soil matrix for ryegrass because they exhibited a technical performance comparable to that of local garden soil (LGS), and the physicochemical parameters of the soil matrix were enhanced compared with the standard values of CJT 340–2011. Although the additive (fly ash) and different types of substrates can affect plant growth and the properties of harvested soils, the level of variation decreases with the stage of growth. As waste recycling is the primary objective of this work, MSSTF is the ideal substrate to use. The treatment process is easy to handle, and represents a sustainable option and an environmentally friendly, beneficial use of MSST.Implications: Muck discharged from slurry shield tunnel construction has put great pressure on the environment and construction cost because of a large number shield tunnels emerging in cities. Directly transporting the discharged muck waste to dumping site not only increases the machinery and labor costs but also raises environmental concerns. Therefore, we explore the way of recycling the discharged muck from slurry shield tunnel as a growth medium for landscaping which was proved to be feasible by a series of pot experimental study. Recycling the discharged muck from shield tunnel as the growth medium for landscaping instead of using purchased raw materials not only can dramatically reduce project costs but also can obviously minimizing the consequent environment pollution. Such technology can contribute to sustainable developments and cleaner construction of infrastructures.