Abstract
Abstract Responses of the segmental tunnel liner to external forces are primarily dependent on complicated interactions among construction process, soil structural interactions, segmental (longitudinal) joint characteristic etc. However, most proposed liner’s design procedures and recommendations are basically empirical and experience based, especially when the roles of tunnel joint are concerned. In the present study, a preliminary design calculation for the segmental joint with consideration of three practical conditions was proposed. The method adopts two main assumptions; the stiffness reduction factor and simplified pre-stressed concrete blocks, so that the flexural capacity of the segmental joint and its interactions to the main reinforced concrete segment body can be designated. Calculation examples are given for three most probable cases, namely, 1) the unbolted joint without joint opening, 2) the bolted joint without joint opening and 3) the unbolted segmental joint with allowing joint opening. Based on these calculations, the required compressive strength of concrete, thickness of liner, steel reinforcement, bolts and number of segments of the liner could be specified. The proposed method could well provide an engineer a tool to determine the initial joint configuration and its interaction to the overall tunnel lining.
Highlights
Precast RC segmental tunnel has played an important role in urban underground developments for decades
The Official Report of the International Tunnelling Association [3] on the Guidelines for the Design of Shield Tunnel Lining merely suggests that the joint flexural capacity should be around 60 % of the flexural capacity of the main segment
Tunnel practitioners have recently started to adopt the unbolted segment joint. They believe that bolts in the segment joints are installed and used only for temporary reasons; i.e., 1) to ensure that the ring is erected inside the allowable construction tolerances, 2) to prevent joint opening when the liner is subject to its own weight before leaving the shield and 3) to ensure that the gasket between joint is compressed when leaving the shield as hoop force will not be acting before tail skin grout pumping
Summary
Precast RC segmental tunnel has played an important role in urban underground developments for decades. Tunnel practitioners have recently started to adopt the unbolted segment joint They believe that bolts in the segment (longitudinal) joints are installed and used only for temporary reasons; i.e., 1) to ensure that the ring is erected inside the allowable construction tolerances, 2) to prevent joint opening when the liner is subject to its own weight before leaving the shield and 3) to ensure that the gasket between joint is compressed when leaving the shield as hoop force will not be acting before tail skin grout pumping. There is limited novelty in the following proposed design methods, it provides 1) a simple tool for engineer to preliminary explore the possible structures and arrangements of precast segmental joint and 2) a linkage between tunnel construction practice and a design procedure regarding bolted and unbolted joints
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