Reuse of Discharged Soil from Slurry Shield Tunnel Construction as Synchronous Grouting Material

Abstract

Soil discharged from slurry shield tunnel construction has put great pressure on the environment and construction cost because of the increasing number of shield tunnel projects in cities. This paper aims to investigate the possibility of reusing the soil from slurry shield tunnels as a synchronous grouting material in the construction of the Wangjiang Road tunnel in Hangzhou, China. Laboratory tests were carried out with Uniform Design Tables U15* (154) by varying the water dosage to binder (i.e., cement and fly flash) ratio (w/b), the binder to river sand ratio (b/s), the slurry shield discharged soil to water ratio (sw/w), and the fly ash to cement ratio (f/c) in the ranges commonly used in engineering practice. Moreover, the response surface method (RSM) optimization approach is introduced to determine the optimum w/b, b/s, sw/w, and f/c ratios to fulfill field demands. The tests results show that slurry shield discharged soil can replace the bentonite as part of synchronous grouting raw material, and its optimal performance is highly dependent on the proportional relationships between w/b, b/s, sw/w, and f/c. The presented guiding framework for recycling the discharged soil from slurry shield tunnel construction for synchronous grouting not only can dramatically reduce the purchase costs of raw material but also eliminates transport and treatment costs of the discharged soil, as well as enhance a portion of the environmental benefits.