• Geomechanics and Engineering
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• v.29 no.4
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• pp.471-486
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• 2022

The effect of segmental joints is one of main importance for the segmental lining design when tunnels are excavated by a mechanized process. In this paper, segmental tunnel linings are analyzed by two numerical methods, namely the Beam-Spring Method (BSM) and the Solid-Interface Method (SIM). For this purpose, the Tehran Subway Line 6 Tunnel is considered to be the reference case. Comprehensive 2D numerical simulations are performed considering the soil's calibrated plastic hardening model (PH). Also, an advanced 3D numerical model was used to obtain the stress relaxation value. The SIM numerical model is conducted to calculate the average rotational stiffness of the longitudinal joints considering the joints bending moment distribution and joints openings. Then, based on the BSM, a sensitivity analysis was performed to investigate the influence of the ground rigidity, depth to diameter ratios, slippage between the segment and ground, segment thickness, number of segments and pattern of joints. The findings indicate that when the longitudinal joints are flexible, the soil-segment interaction effect is significant. The joint rotational stiffness effect becomes remarkable with increasing the segment thickness, segment number, and tunnel depth. The pattern of longitudinal joints, in addition to the joint stiffness ratio and number of segments, also depends on the placement of longitudinal joints of the key segment in the tunnel crown (similar to patterns B and B').

• Journal of the Society of Disaster Information
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• v.10 no.1
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• pp.61-70
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• 2014

Synthetic fiber reinforced concrete is applicable to many applications for construction material. In general, synthetic fibers have low tensile strength and elastic modulus, but they have many advantages such as high crack resistance, impact resistance, chemical resistance, flexural behavior and corrosion free in fiber reinforced concrete. Recently, fiber reinforced concrete with macro synthetic fibers has been used to improve performance of structures in tunnel shotcrete, precast segmental lining and bridge slab and precast concrete structures. This study investigated the influence of bundled type polyamide fiber reinforced concrete on the flexural behavior in accordance with ASTM C 1609 and KS F 2566 standards.

• Korean Journal of Bronchoesophagology
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• v.7 no.1
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• pp.40-45
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• 2001

Management of laryngotracheal stenosis remains one of the most challenging problems facing the otolaryngologist. The key to success is to obtain adequate rigid circular support with normal mucosal lining. Four Patients with laryngotracheal stenosis were surgically treated in our institution in 2000. All the patients were male adults. The cause of stenosis were longterm or repeated endotracheal intubation and tracheostomy in our patients. All patients were successfully decannulated following segmental resection of the stenotic portion including the anterior arch of the cricoid cartilage and end-to-end anastomosis after suprahyoid laryngeal release. The time between treatment and decannulation was just one day in three patients. These results suggest the Possibility of early decannulation even if the cricoid cartilage was partially resected. It is better to prevent laryngotracheal stenosis rather than to treat it once it has occurred.

• Maxillofacial Plastic and Reconstructive Surgery
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• v.33 no.5
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• pp.435-439
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• 2011

Ameloblastoma is an aggressive benign odontogenic epithelial tumour that may arise from the enamel organ, remnants of dental lamina, or the lining of an odontogenic cyst. It is usually categorized into solid or multicystic, unicystic, and peripheral types. Treatment ofameloblastomas include conservative methods such as marsupialisation, enucleation, and curettage; and radical treatments such as marginal or segmental resection. Radical treatments have resulted in lower recurrence rates; however, may also encounter esthetic, functional, and reconstructive problems. Unicystic ameloblastoma has been considered less aggressive and a lower recurrence tendency. Thus, many authors have recommended conservative treatment in cases of unicystic ameloblastoma. An 11 year-old boy presented with displaced second and third molars by luminal unicystic ameloblastoma in the mandible. Cyst enucleation, curettage, and third molar extraction were done. No signs of recurrence or esthetic problems such as facial asymmetry were seen radiologically and clinically, up to 8 years 2 months postoperatively.