Experimental Study on Static and Dynamic Characteristics of Tunnel Slag as Road-Base Material

Growing body of research focused on utilizing tunnel slag as a substitute for natural aggregate in road-base fillers, aiming to mitigate the environment impact of slag deposits. However, as a load-bearing material, the tunnel slag could have considerably permanent deformations due to long-term traffic loads during the whole service life which eventually leads to very large settlement on road. To reveal the long-term deformation mechanism of the tunnel slag, a series of static and cyclic large-scale triaxial tests were conducted under three levels of confining pressures mimicking practices. Most importantly, special attention was placed on investigating the effect of particle gradation and cyclic stress amplitude. Experimental results demonstrated that the particle gradation had various effects on both static and cyclic characteristics since different spatial skeleton-void structures. More specifically, under static loadings, specimens with an uneven skeleton-void structure exhibited superior strength than ones with pure or suspended skeleton structures, while in dynamic tests the pure skeleton structure leads to the highest modulus with a minimal long-term deformation. Cyclic cumulative deformation of specimens overall increases as the increase of coarse content and cyclic stress amplitude, but their relationship gradually changes from linear pattern following the mechanism of plastic shakedown, to non-linear patterns following plastic creep and incremental collapse. Finally, for a given gradation, confining pressure was found to display a positive correlation with resilient modulus so negative with cumulative strains.