Abstract
Due to population growth and urban congestion, the space available for the development of public infrastructure is sharply decreasing. Engineers are therefore resorting to the efficient use of underground space, which involves the construction of tunnels and other underground structures. Many such projects will be located in rock/soil with time-dependent behavior or under high overburden pressure. Thus, under such stress conditions, there may be a need for a deformable supporting system that can serve as a buffer layer to protect tunnel linings from time-dependent deformations of the excavated rock/soil. This paper investigates the use of cement mortars containing crumb recycled tire rubber to develop a flexible interface material for such applications. The effects of the w/c ratio, rubber content, and particle size on the mechanical properties of rubber filled mortars were studied using uniaxial and triaxial compression tests. A statistical factorial experimental plan was designed to obtain response surfaces for the parameters under study. A model tunnel was made, instrumented, and tested in a specially designed pressure cell under hydrostatic pressure to investigate the effect of using flexible rubber-filled mortar layers around tunnel linings on the development of stresses. The findings of this research suggest that cement mortars containing crumb tire rubber have superior ductility and may be used to accommodate deformations around tunnel linings, pipelines, and other buried infrastructure.
