نشریه مهندسی تونل و فضاهای زیرزمینی
سال سوم شماره 2 (زمستان 1393)

This paper aims to use pushover analysis for performance-based seismic assessment of linings of shallow tunnels constructed in soil that are subjected to vertical shear waves. Pushover analysis is a nonlinear static analysis that works base on pushing laterally 2D numerical nonlinear model of soil with tunnel statically. This analysis considers just ovaling/racking deformation of a lining and compared to the other existing seismic analysis approaches، it has the advantage of using directly a standard acceleration response spectrum as seismic demand. Initially in this paper، responses of a typical tunnel due to four earthquakes were calculated using pushover analysis. In continue، the approach of employing a typical standard acceleration response spectrum as seismic demand was presented using the building’s standard spectrum of FEMA 302 provisions. All the resultant performance points of pushover analyses were then evaluated by carrying out nonlinear dynamic time history analyses and the pushover method was verified. However، further studies are required to propose an acceptable response spectrum for the geotechnical nature of soil deposits containing shallow tunnels as their seismic demand.

Considering private and public rights in regard to underground developments is an important matter. Inattentiveness to such rights might lead to injustice and dissatisfaction of landowners towards such developments and as a result limited success in the construction and use of underground spaces. Ownership of subsurface spaces varies in different countries. This paper aims to indicate the importance and necessity of ownership and legal considerations in different countries using a comparative approach based on researches carried out in different locations of the globe and case studies. Following an analytical review on the necessity of the use and expansion of underground spaces، relevant laws of different countries are compared and discussed. It is shown that legal obligations and challenges of ownership in the development and expansion of underground spaces especially in urban areas play an important role in urban management and different decision-making processes، and therefore require legislations in order to overcome some of the current challenges and problems in urban development. Introduction Considering private and public rights in regard to underground developments is an important matter. Inattentiveness to such rights might lead to injustice and dissatisfaction of landowners towards such developments and as a result limited success in the use of underground spaces. Ownership of subsurface spaces varies in different parts of the world. Methodology and Approaches This paper aims to indicate the importance and necessity of ownership and legal considerations in megacities. A comparative approach has been taken in this study، based on researches carried out in different countries and case studies provided partly by reports of theInternational Tunnelingand Underground SpaceAssociation and research carried out in the capital Tehran. Relevant laws and ownership regulations relevant to underground spaces in different countries are briefly compared and discussed. As there is no standard model for such regulations، each country follows their own sets of rules in this regard. Current regulations in Iran are then reviewed and suggestions made for legislations in regard to the use of underground spaces. Results and Conclusions It is shown that legal obligations and challenges of ownership in the development and expansion of underground spaces especially in urban areas play an important role in urban management and different decision-making processes، and therefore require legislations in order to overcome some of the current challenges and problems in urban development.

A new analytical solution for stress state around gas storage cavities، under constant internal pressure، is presented in this study. Rock mass was assumed to behave as isotropic، linear elastic materials. Due to complexity of the problem for noncircular cross-section configuration of cavities، Muskhelishvili complex potential functions combined with conformal mapping was used. Finally، the results predicted by analytical solution were compared with those obtained by phase 2 finite element software for both weighted and weightless models which showed a good agreement except for some points of the cavity wall where large curvature and high stress concentration exist.

To extend the application of earth pressure balance (EPB) machines to different geological conditions، the soil to be excavated must be treated with soil conditioning additives. The additives are injected at several points on the EPB machine; ahead of the cutting head، in the pressure chamber and along the screw conveyor. The behavior of the excavated soil، from mixing to extraction، depends mainly on the workability of the conditioned soil. Workability is the ease with which the excavated soil can be mixed with additives، compressed in a pressure chamber، flow freely from the face and be extracted by a screw conveyor. Workability is an indicator of the plasticity of the support media and the cohesiveness of the soil and is thus a criterion for applicability of EPB tunneling. The factors that affect the workability of the conditioned soil are water content، soil grade and size، additives and conditioning parameters. In this study، the effect of soil grade and size on the workability of conditioned soil for EPB-TBM tunneling was assessed using a laboratory slump test. The influence of fine grains on the workability of conditioned soil was investigated by testing mixtures with different soil-foam contents. The test results show a quantitative relationship between fine-grains and workability for the application of EPB shields. The results clearly show that decreasing the fine grain content became stronger with an increase in the slump of the conditioned soil. It was concluded that a fine grain content of 25% to 60% produced the most normal behavior of the percentages tested in this study.

Circular Tunnels are used in urban transportation these days. One of the major applicable is metro tunnel which is built by T. B. M. an investigation of these structures during an earthquake should be considered in design of these structures.

for studying on dynamic behavior of tunnel under earthquake motion، PLAXIS software which is based on finite element code is used. In this study، the method of seismic analysis of tunnel with PLAXIS is explained. For more accuracy the data are used based on Tabriz tunnel properties. The dynamic properties of soil and also the method of iterative process for finding acceptable shear strain are obtained from previous study and also result of some dynamic tests. Numerical analyses are performed in both linear and Mohr-Culomb model for soil. Approaches: In order to investigation the effect of tunnel on earthquake motion، the diametric deflection of final lining is calculated on each analysis. The major forces such as bending moments and axial forces are happen in maximum deflection in diameter. For finding the effective parameter on dynamic behavior of tunnel، sensitive analyses are performed. In these analysis variation of dynamic parameter such as maximum acceleration، damping and shear modulus of soil are mentioned. Moreover، other mechanical properties of medium like friction angel of soil are selected for sensitive analysis. Geometrical properties of final lining such as thickness and diameter of lining are also used to calculate the flexibility ratio. Allowable stress and strain is also calculated and compare with existence result.

the results show that stress and strain are not different on acceleration blow 0. 5g but the different in result are more mentioned for acceleration more than 0. 5g. In addition on sensitive analysis in friction angle of soil، the rate of dynamic forces is decrees up to 30 degree and after that، the results showing no variation. These effects are more significant for tunnel with high depth. Investigation on variation of dynamic results versus fallibility ration show that with increasing this ratio، the rate of degradation of dynamic forces are decrees and in F=25 and for more، these variation is disappear and the results are independent of diameter of tunnel.