Performance of New Type of Foamed Concrete in Supporting Tunnel in Squeezing Rock

Abstract

For tunneling in squeezing rock, large deformation induced by tunnel excavation and creep of squeezing rock has been a great challenge during construction. This large deformation would keep growing for a long time, significantly threatening the stability of the tunnel. In this study, a new foamed concrete is introduced. Relative to conventional foamed concrete, the new foamed concrete has the characteristics of good ductility (it maintains its integrity and is not easy to crack), high compressive strength (the uniaxial compressive strength is 3.12 MPa, whereas for the conventional concrete it is about 0.9 MPa), and tight adhesion with cement concrete (proven by shear strength at interface between the foamed concrete and the cement concrete) as shown by laboratory tests. To evaluate its performance as a cushion material in the yielding support for a tunnel, the foamed concrete was applied in a yielding support for a deep-buried tunnel in squeezing rock by numerical simulation. Compared with the results of the stiff support, the contact and shear stress at the interface between the cushion layer and the second lining are very small, resulting from the capacity of the foamed concrete to endure great loads and absorb energies from the creep of surrounding rock, thereby improving the stress state of the second lining and reducing the deformation of the second lining.