Rock Mechanics
Seyed S. Mousavi; M. Nikkhah; Sh. Zare
Abstract
In this work, we tried to automatically optimize the cost of the concrete segmental lining used as a support system in the case study of Mashhad Urban Railway Line 2 located in NE Iran. Two meta-heuristic optimization methods including particle swarm optimization (PSO) and imperialist competitive algorithm ...
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In this work, we tried to automatically optimize the cost of the concrete segmental lining used as a support system in the case study of Mashhad Urban Railway Line 2 located in NE Iran. Two meta-heuristic optimization methods including particle swarm optimization (PSO) and imperialist competitive algorithm (ICA) were presented. The penalty function was used for unfeasible solutions, and the segmental lining structure was defined by nine design variables: the geometrical parameters of the lining cross-section, the reinforced feature parameters, and the dowel feature parameters used among the joints to connect the segment pieces. Furthermore, the design constrains were implemented in accordance with the American Concrete Institute code (ACI318M-08) and guidelines of lining design proposed by the International Tunnel Association (ITA). The objective function consisted of the total cost of structure preparation and implementation. Consequently, the optimum design of the system was analyzed using the PSO and ICA algorithms. The results obtained showed that the objective function of the support system by the PSO and ICA algorithms reduced 12.6% and 14% per meter, respectively.
M. Nikkhah; Seyed S. Mousavi; Sh. Zare; O. Khademhosseini
Abstract
The joints between segmental rings can withstand a certain amount of bending moment as well as axial and shear forces. Generally, in the structural analysis of tunnel segmental lining, the joints can be modeled as elastic hinges or rotational springs, and their rigidity should be demonstrated in terms ...
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The joints between segmental rings can withstand a certain amount of bending moment as well as axial and shear forces. Generally, in the structural analysis of tunnel segmental lining, the joints can be modeled as elastic hinges or rotational springs, and their rigidity should be demonstrated in terms of the rigidity of the joints or their rotational stiffness. Therefore, the bending moment acting on the tunnel lining is reduced. Hence, the tunnel designers are free to choose a lining with a lower cost. In this research work, especially considering the joints, the structural analysis of the segmental lining with variation in the flexural stiffness of the joints ( ), soil resistance coefficient ( ), number of segmental lining joints, and joint arrangement of segmental lining were carried out by the Force-Method equations. The imposed bending moment and axial forces were computed based on the Beam-Spring method, which is widely used to analyze the internal forces of segmental lining, and compared them with the results of the Force-Method equations. Then the effects of joint arrangement patterns and joint rotational spring stiffness on the results of the Beam-Spring analysis were evaluated. Finally, the optimum characteristics of the reinforced concrete segmental lining design were evaluated using the interaction diagram of bending moments and axial forces. The results obtained showed that the presented pattern for the segmental lining at the Chamshir tunnel was imposed against the external pressures on the segmental lining with an acceptable safety factor.
