Damage assessment of tunnels caused by the 2004 Mid Niigata Prefecture Earthquake using Hayashi’s quantification theory type II

Mountain tunnels, being underground structures and situated deep within rock layers, are generally considered to suffer appreciably less damage from earthquakes than surface structures. However, it has been reported that many tunnels were damaged by the 1923 Great Kantou earthquake, the 1995 Great Hanshin Earthquake, the 1999 Taiwan Chi-Chi Earthquake, the 2004 Mid Niigata Prefecture Earthquake and the May 2008 Great Wenchuan Earthquake in China. In this study, the damaged tunnels resulted of the 2004 Mid Niigata Prefecture Earthquake are the study objects. The damage patterns are analyzed, and the information which is considered to be of influence, such as the distance to epicenter, the completion time, the geological conditions, etc., are collected. A database of the damaged tunnels has been created using a Geographic Information System (GIS). The influence ranking for these factors has been analyzed using Hayashi\u27s quantification theory II. The degree of the tunnel damage has also been assessed using GIS and Hayashi\u27s quantification theory II. The field investigation is in close agreement with the assessment results following Hayashi\u27s quantification theory II

Influence of shear wave velocity reversals on one-dimensional site response of spatially varied profiles

Spatial variability and uncertainties that exist in natural deposits are often modeled in one-dimensional (1D) site response analysis through multiple spatially varied shear wave velocity (VS) profiles. These spatially varied VS profiles usually exhibit VS reversals that might not be observed in the natural deposits. This study investigates the consequences of allowing VS reversals in spatially varied VS on the 1D site response characteristics. Two sets of sixty (60) spatially varied VS profiles, with and without VS reversals, were generated. Results of the 1D site response analysis showed that allowing VS reversals in spatially varied VS profiles can lower the median surface response up to 10% at periods shorter than the fundamental site period. The difference in surface response becomes more significant for the higher intensity input motions. The variability in the median surface response was not significantly influenced by the presence of VS reversals

A proposed seismic velocity profile database model

We describe the data model that we intend to use in a publicly available site profile database under development for the United States. The initial implementation of the database contains data from California. Currently, our prototype data model consists of JavaScript Object Notation (JSON) format files for storing metadata and data. For a site to be included in the database, the minimum metadata requirements are geodetic coordinates and elevation values, and the minimum data requirement is a shear-wave velocity profile. The JSON files are structured in a hierarchal manner to store metadata and data using a nested structure consisting of location, velocity profiles, dispersion curve data (for surface-wave methods), geotechnical data, and horizontal-to-vertical spectral ratios. The database schema at the current stage of the project, and as we continue to develop the data model we will consider including other relevant data, as well as evaluate other file formats to increase the efficiency of data storage and querying. In the current data model, location information includes site geodetic values (latitude, longitude, and elevation) and various site descriptors related to surface geology, geomorphic terrain category, slope gradient at various resolutions, and a geotechnical site category. Velocity data include the geophysical method(s) used to obtain the shear-wave velocity profile, type of data recorded, modeled primary- and shear-wave velocity as a function of depth, modeled profile maximum depth, and the calculated VS30 value. In the case of surface-wave based data, dispersion curve data can be recorded in data structure as phase velocity versus either wavelength or frequency. Geotechnical data includes boring logs penetration resistance, cone penetration test sounding logs, and laboratory index test results. Horizontal-to-vertical spectral ratio plots are given as a function of frequency

Numerical analysis of the support system in the transition zone of the Esfahan subway project

This paper presents the design and 3D numerical modeling of the temporary support system for the twin tunnels in the transition zone of the Esfahan subway project. Ground movements caused by tunneling beneath urban areas can have a significant impact on adjacent structures and therefore require consideration when choosing the excavation method and the type of support system. Due to the old buildings in the historical city of Esfahan, this research requires parametric studies for the use of simulation techniques. This paper focuses on 3D stability analysis and design of the support system required to control the critical strain and ground movement due to excavation of the transition area of the twin tunnels in the Esfahan subway project. A numerical model is developed to estimate the excavation effects on the critical strain and ground settlement and also the effect of reinforcement measures. In the 3D numerical model, a constitutive law characterized by the time-dependent stiffness and strength of the shotcrete is employed. Results show that the suggested support is sufficient to control the settlement and critical strain due to tunneling. Comparison between the 2D model prediction and the results of corresponding 3D model indicates that the conformity between 2D and 3D analysis results decreases in the transition region. One of the most useful methods to determine the induced seismic loads, the use of time-history dynamic analysis is usually done for major projects. In this paper, for the twin tunnels of subway, Fast Lagrangian Analysis of Continua (FLAC) software is used for this purpose. © 2014 Saudi Society for Geosciences