Seismic isolation effect of a tunnel covered with coating material

A method to cover a tunnel lining with a sop and thin coating is discussed herein as a possible measure for mitigating seismic damage to tunnels. Long-term earthquake observations at different tunnel sites within a variety of alluvial soil deposits have demonstrated that a circular tunnel is liable to deform in such a way that its two diagonal diameters crossing each other expand and contract alternately. Narrowing clown vibration modes for discussion to this particular and the most important mode, any of the essential items of the soil-tunnel system-namely the soil, the coating and the tunnel lining-had only one degree of freedom, allowing the isolation effect to be simply evaluated in terms of a limited number of key parameters. (C) 2001 Published by Elsevier Science Ltd. All rights reserved.