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Experimental Verification of Joint Effects on Segmental Tunnel Lining
Supot Teachavorasinskun Associate Professor
Department of Civil Engineering, Faculty of Engineering, Chulalongkorn University, Phayathai Rd., Pathumwan, Bangkok, Thailand Tanan Chub-Uppakarn Department of Civil Engineering, Faculty of Engineering, Chulalngkorn University, Phayathai Rd., Pathumwan, Bangkok, Thailand
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ABSTRACT |
A simple experiment has been conducted to explore the load carrying capacity of a small model segmental tunnel lining. Scaled segmental tunnel (f 15 cm) was made from PVC having nominal thickness of 8.5 mm. A few joint orientations (variation of joint number and stiffness) were constructed and tested to verify its load carrying capacity. Joint stiffness was first obtained from a series simple beam support tests. It was found that 4-joint segmental tunnel can react like a full liner as recognized in the literature. When the number of joints increased, the load carrying capacity was greatly dependent on the values of joint stiffness. Namely, the weaker the joint is, the smaller is the bending moment that can be transferred through. In general design practice, a specific value of moment reduction factor is usually selected either using the empirical relation or picking up a value given in the design codes. However, there is no practical consideration for variation in joint stiffness. The present paper proposes that the bending moment reduction factor should be determined from the simple beam support test carrying out using the equivalent liner and joint materials and joint characteristics. Once the bending moment reduction factor is determined, the detail designs of the liner can then proceed.
Keywords: Segmental tunnel, tunnel liner, Bending moment
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