Scattering Of Elastic Waves By Underground Circular Lined Tunnels

Scattering and diffraction of earthquake waves by the large, underground tunnelstructures can affect the ground motion near the tunnels, still, it can also affect thebuildingsonthegroundnearby.Therefore,tosolvethiskindofproblemhasimportantmeaningonboththeoryandengineeringapplication.In this paper, a special boundary integral equation method will be used to studythe scattering of elastic P,SV and Rayleigh waves by underground, circular linedtunnel. The total wave field is superposed by free field and scattered field. Based onthe theory of simple layer potential, scattered wave field is constructed by distributedlinesources onthe virtual source plane. The densityofthe virtual wavesource can begained by solving the equations which are derived by boundary conditions. Finally,thewholewavefieldcanbeachieved.The accuracy of the numerical result is checked up by the analytic solution andresidual errors of boundary conditions. At the same time, the effects of some factorssuch as the frequencyof the incident waves, the incident angle, the lining's propertieson the surface ground motion of the lined tunnels and the lining's properties on thehoop stress amplitude on the wall of the lined tunnel are illustrated. The numericalresults show that, the underground tunnel will amplify the amplitude of the surfaceground motion and the dynamic stress concentration factor, the tunnel with soft linerhas great effect on the low frequency incident waves, while the tunnel with stiff linerhas great effect on the high frequency incident waves, and the tunnel with stiff linercan also decrease the stress in the half-space. And some useful conclusions arederived in this thesis, which have great significance both in theoryand in engineeringapplication and provide foundations for the anti-seismic design of undergroundcavities.