Efforts should be made to promote the use of soil generated from excavation during shield construction as a recycled resource.
Generated soil is a construction byproduct, and it is necessary to reuse it as a resource as much as possible based on the Recycling Law (1991).
There are several ways to use construction sludge as waste:
① Personal use
② Sale for a fee
③ Utilization of recycling system (recycling designation system, recycling certification system)
Construction sludge may be recycled through intermediate treatment in order to contribute to waste control and environmental conservation. In this case, it is necessary to conduct a test for the presence of harmful substances and to perform intermediate treatment according to the quality specified for the material, the required shape, etc., and the shield construction equipment.
When performing intermediate treatment, it is necessary to select the most appropriate treatment method, taking into consideration soil conditions, underground transportation method, shaft transportation method, shaft site size, disposal site conditions, etc. Procedures must be followed for equipment such as dehydration treatment facilities that have the processing capacity that requires notification.
Soil generated from shield construction must be properly treated and disposed of.
Among the materials discharged from shield construction, the sludge with high moisture content and fine particles is treated as inorganic sludge. As for waste, sludge must be properly treated and disposed of in accordance with the Waste Disposal Law. In general, a muddy condition is a condition in which piles cannot be piled up on standard dump trucks and people cannot walk on it.If we refer to this condition as an indicator of soil strength, the cone index is approximately 200kN. /m2 or less, or the unconfined compressive strength is approximately 50kN/m2 or less.
In addition, if the contractor performs the treatment himself, he must comply with the treatment standards stipulated in the Waste Management Law. In addition, when processing outsourced waste, the outsourcing standards must be complied with, such as confirming the license of the outsourced industrial waste treatment business, concluding a written outsourcing contract, and issuing an industrial waste management form (manifesto).
*An example of mud water circulation method
(muddy water shield method, reverse circulation method)
(Reference material: "Tunnel Standard Specifications - Shield Construction Method Established in 2006", Japan Society of Civil Engineers)
(environmental impact assessment)
Overview of the Japan-Korea tunnel