Development of Deformable Protective System for Underground Infrastructure Using Cellular Grouts
M. Nehdi, Ashfaq Khan, and K. Y. Lo
Appears on pages(s):
grout; strain; stress.
With population growth and urban congestion, there is a growing need to use underground structures simply because available economical space is increasingly scarce at the surface. Underground structures and tunnels are employed in a growing range of applications encompassing transportation and storage facilities; military bases; hydroelectric, nuclear, and thermal generating stations; and processing and disposal facilities for radioactive and chemical waste. Many of these underground structures and tunnels, however, will have to be constructed in soft soil, rocks with time-dependent deformations, and other situations in which tunnel lining segments will be exposed to excessive deformations of the surrounding rock/soil that may lead to their failure. This study aims to develop a cost-effective grouting system that can serve as a deformable buffer layer between tunnel lining segments and the excavation line and therefore accommodate excessive rock/soil deformations. The effects of water-cement ratio (w/c), foam content, and sand addition on the mechanical properties of cellular grouts were studied using uniaxial and triaxial compression tests. Brittleness index and shear strength parameters of these grouts were also determined. The findings of this study suggest that low-density nonsanded cellular grouts have superior plastic behavior under triaxial states of stress and may be used to accommodate excessive deformations around tunnel linings, pipelines, and other buried infrastructure.