ICSV18, Rio de Janeiro, Brazil, 10-14 July 2011 1 EXPERIENCE WITH RANDOM PROCESS THEORY ON PREDICTION OF GROUND BORNE VIBRATION FROM UNDERGROUND METRO SYSTEMS Salih Alan, Mehmet Çalışkan Department of Mechanical Engineering, Middle East Technical University, Ankara, 06800 Turkey. e-mail: caliskan@metu.edu.tr This paper outlines experiences with random process theory in prediction of ground borne vibrations. Several track systems as ballasted and direct fixation have been incorporated in a modified form of an existing model. Vehicle model is considered as a one-eighth car model. Hertzian contact stiffness is introduced along with uneven spacing of wheels. Bogie mass and suspension characteristics are employed to produce a discrete model coupled with the tunnel and soil dynamics. Excitation due to rail irregularities has been taken into account. The flex- ibility and effectiveness of random process theory in prediction of ground borne vibrations have been demonstrated by several examples from underground metro lines under construc- tion in Europe. 1. Introduction Underground metro systems have been a remedy for the public transportation difficulties of modern cities. Ground borne vibrations are generated due to the railway traffic of the underground vehicles. These vibrations occur due to the interaction of the train with the track and they can propagate in the tunnel and soil around the tunnel. The interaction between the wheel and the rail causes dynamic loading due to irregularities of the wheel and the rail. The buildings above the ground and the people inside these buildings will be affected by the vibrations transmitted to the foundations of the buildings. The buildings and the people are affected by the disturbance due to vibrations in the frequency range of 1-80 Hz and due to the re-radiated noise in the range of 1-200 Hz 1 . The work presented in this paper aims to predict analytically the ground borne vibrations due to railway traffic. The modelling is based on the formulation given by Forrest and Hunt 2, 3 . The formulation given by Forrest and Hunt 2, 3 is modified by Sarıgöl 4 to take into account different as- pects of the structure of the system. Further modifications and improvements are made by the au- thors of the current paper in order to make the much detailed analysis. The procedure described in this work is implemented on a computer code. System parameters are used to predict the ground borne vibration due underground traffic with the implemented code. The organization of the paper is as follows. The second section of the paper introduces the original formulation given by Forrest and Hunt 2, 3 . In the third section, the modifications on the original formulation are presented. Case studies with different track configurations are given in the fourth section. In the last section, the conclusions of the study are summarized.