نشریه مهندسی تونل و فضاهای زیرزمینی
سال یکم شماره 1 (زمستان 1391)

This research aims to introduce an optimized design with minimum possible fiber content while having the maximum possible energy absorption capacity. A series of laboratory tests were conducted with various additive and fiber contents to reach this goal. General recommendations for achieving the optimized results were proposed based on experimental results. Beam and panel tests were used to account for energy absorption capacity.

In this paper, an elasto-plastic analytical-numerical method for the analysis of underwater tunnels, excavated in a strain-softening and Hoek-Brown rock mass is proposed. Seepage flow and secondary permeability of the rock mass due to the mechanical-hydraulic coupling are taken into accounts for plastic zone. Meanwhile, a modified accurate seepage model is used for elastic zone. As the analytical equations do not have closed form solutions, a computer program has been provided.

Performance analysis and accurate prediction of Penetration Rate (PR) of a TBM have been the ultimate goals of many research works. A reliable prediction of a TBM performance is necessary in budget control and also time schedule planning in underground excavation projects. Evaluating the optimum operational parameters of machine using Artificial Neural Networks (ANN) method is the main objective of this research work which has not been estimated and reported in previous studies in this field of study.

Segment joints of the lining should be capable of withstanding a certain amount of bending moment, axial and shear forces, and considering that the force-displacement correlation may behave linearly within a certain range of the applied load, the bending moment applied on the lining might be reduced. Hence, the lining thickness could be reduced once smaller internal forces are involved. In the structural analysis of the lining segment, joints could be modeled as elastic tubes and their stiffness could be expressed in terms of rigidity.

Various underground spaces such as tunnels are constructed in urban areas for different purposes. These spaces are often located in soil media near to ground surface. In EPB tunneling, the face pressure (P) and backfill grouting pressure (G) are the most important factors to prevent the surface settlement. The 7th line of Tehran subway project is excavated by EPB machine. In this paper four section of 7th line tunnel are selected and the influence of face pressure on surface settlement are investigated numerically by PLAXIS Tunnel software. In two section of tunnel the results of numerical models are verified by monitoring instruments. In next two sections of tunnel, four status of face pressure: P=P0 (estimated initial pressure), P=1.5P0, P=2P0 and P=4P0 and for each state, five status of backfill grouting pressure: G=0, G=P, G=P+0.5 bar, G=P+1 bar and G=P+2 bar are considered and surface settlement are analyzed. Results show that an increase of %400 for face pressure lead to a decrease of maximum 5 mm in surface settlement. So in this project the influence of face pressure is trivial but the influence of backfill grouting pressure is more significant.

Using underground spaces is one of the new approaches in sustainable urban developments. This approach is intended to solve some urban problems such as shortage of spaces، traffic and environmental issues. This research aims to introduce various underground spaces، their aspects and benefits in the context of urban underground development. In this paper، after defining the problem and explaining its importance، the concepts of sustainable development and underground spaces are described. Underground spaces are then analyzed from climatic، traffic and environmental viewpoints. As a case study، the underground development of Tajrish Square is proposed. In the past ages، underground spaces have been used due to traditional needs and reasons; but in the contemporary age، extensive construction and use of underground spaces are a new approach in urban development in the world and especially in Iran. Studying the history of the subject indicates that today with the advent of technical inventions and modern evolutions، the development of such spaces especially urban infrastructure are essential due to increasing unfavorable climatic conditions، transportation problems، lack of space on the surface، and environmental pollutions، in addition for the purpose of safety and security improvement. A new approach is introduced in this paper to solve urban problems and supply urban needs such as urban infrastructure، tunnels، underground parking، storages and refineries. Methodology and Approaches: Underground development approach has been used in this research considering historical، descriptive and analytical methods in a case study. The methods and software programs used in this research include GIS، AutoCAD، and other software programs for analyzing، designing and rendering. Results and The results of this paper show that underground spaces have basic and positive potentials in the sustainability context. These potentials consist of having a constant temperature، sustainability in harsh climates، stability in critical conditions and accidents، source of space، energy، etc. Urban underground development approach can be used for solving urban problems and upgrade sustainability. In Tajrish Square، transportation problems، unfavorable climate، lack of space، in addition to distinctive natural، historical and cultural features are observed. Using people-oriented qualities of urban design and alternatives of underground development from minimum intervention to maximum intervention are presented. After the assessment of the above-mentioned influencing factors the best alternative is selected. Ultimately urban underground space design framework and guideline with emphasis on Tajrish Square are presented in this research