Seismic Soil-Structure Interaction Analyses and Computational Simulation of Tunnels in Soft Ground Subject To Cascadia Subduction Zone Earthquake


Abstract eng:
The main objective of this paper is to describe the framework and main assumptions for the nonlinear dynamic analysis and design of a tunnel lining in a cohesionless sand and gravel soil. The tunnel is subjected to heavy earthquake excitation in the Cascadia subduction zone. In order to study the influence of the design parameters, Finite Element and Finite Difference Methods (FEM and FDM) and Soil-Structure Interaction (SSI) analyses were used. Also included in this paper is the selection of the lining shape, using a variety of assumptions, including a zone of improved material due to the use of umbrella pipes above the tunnel crown and the effects of the excavation sequence. This study is based on simulated ground motions and other parameters from various earthquake records and highlights the aspects of SSI analyses leading to the support required to accommodate the excavation sequence. This approach provides a practical method for the design and construction of tunnel linings in cohesionless soft ground. From a case study, a feature, interpreted as an unexpectedly deep moraine, was encountered while driving a hard rock tunnel using drill and blast techniques. The depth of the tunnel crown was 60 m below ground surface. This moraine is dense sand with rounded boulders, cobbles and gravel. In order to deal with the effects associated with this cohesionless moraine material, an umbrella pipe system with ports for grouting was driven in order to provide the cover required to install the lattice girders and shotcrete required as initial support to provide a safe and stable opening during the construction. The initial support was designed to support the static loads during the construction. The permanent support, incorporated the temporary support, consisted of additional shotcrete and rebar, and was designed to perform satisfactory for the earthquake of Annual Exceedence Frequency (AEF) of 1/2,475 year. Grouted hollow bar anchors were used in the sidewalls. Four earthquake time histories, including a subduction earthquake, were used to check the adequacy of the design. For construction control various types of geotechnical instruments such as convergence arrays and MPBX (Multi Purpose Borehole Extensometers) should be installed and monitored to check the design assumptions for deformations.

Contributors:
Conference Title:
Conference Title:
16th World Conference on Earthquake Engineering
Conference Venue:
Santiago (CL)
Conference Dates:
2017-01-09 / 2017-01-13
Rights:
Text je chráněný podle autorského zákona č. 121/2000 Sb.



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 Record created 2017-01-18, last modified 2017-01-18


Original version of the author's contribution as presented on USB, paper 4865.:
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