UBC Theses and Dissertations
Response of underground power transmission cables subjected to earthquake induced permanent ground deformation Ahmadnia, Alireza
The aim of this study is to evaluate the response of underground power transmission cables subjected to earthquake induced permanent longitudinal and lateral ground movements. The experimental work related to this research involved full-scale physical modeling. The testing facility used for this project comprises a 2.5 m x 3.8 m soil chamber, with the capacity to subject buried transmission cables to large relative displacements. The buried cables were subjected to axial and transverse soil movements, and the corresponding longitudinal and horizontal transverse soil loads were measured. A total of 15 axial pullout tests and 10 lateral pullout tests were conducted for the cable with different burial depths. In the absence of guidelines available for buried underground cables, the results of the full-scale experimental studies, which provide first-hand information on the cable-soil interaction behaviour, were compared with the response predicted from previous research work and also those based on current pipeline design guidelines such as ASCE (1984) to assess the applicability of those guidelines for buried power transmission cables. To better understand the cable-soil interaction behaviour, 3D numerical models were created to simulate the longitudinal and transverse experimental test set-ups. Numerical models, with the help of parameters derived from the laboratory element testing, were calibrated and validated based on the experimental testing. A parametric study was conducted to study the effect of the cable/soil relative stiffness, the material model parameters, burial depths and cable/soil interface friction on the response of buried cables. Furthermore, numerical models were developed to study the effect of out-of-straightness in the cable on the longitudinal soil loads. An analytical procedure, verified with numerical simulation, was developed to calculate the additional axial soil loads on the buried cable with out-of-straightness. Based on the results of experimental and numerical simulation, nonlinear longitudinal and horizontal transverse soil spring models were developed. Then, the response of buried cable subjected to the longitudinal and transverse permanent ground deformation was assessed as a function of different ground deformation parameters. Finally, analytical procedures were also developed for the quick assessment of the response of the buried cable subjected to PGD.
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