Ultimate capacity of a segmental grey cast iron tunnel lining ring subjected to large deformations

Abstract

Understanding t he behaviour of existing tunnels subjected to in - service deformations, as a result of the construction of underground works (e.g. new tunnel s ) in their proximity, is of importance in order to safeguard infrastructure within the u r ban environment. The associated deformations that t ake place during tunnelling have to be carefully assessed and their impact on the existing tunnels need s to be considered . A half - scale segment al grey cast iron (GCI) tunnel lining ring was tested as part of an extensive research project investigating the impact of new tunnel excavations on existing tunnels conduc ted at Imperial College London. A sophisticated experimental arrangement was developed to deform the ring in a variety of modes under combined displacement and load control. This paper reports on experiments carried out to assess its structural response when subjected to large deformations . The test s reported are the first to be conducted on a realistic scale model under carefully controlled conditions, and provide valuable insight into the behavio ur of a G C I segmental ring during distortions commonly observed in reality . Details of the experiments , including the adopted test set - up and the instrumentation employed , are presented. The measured bending moments around the ring, as a result of the appl ied deformations, are determined and compared with th os e predict ed using the well - known equations given by Morgan (1961) and Muir Wood (1975) , often used in industry , as well as those obtained assuming an elastic continuous ring

Analytical approach for circular‐jointed shield tunnel lining based on the state space method

“…However, their stiffnesses depend on some factors, such as the geometrical configuration, properties of gasket and bolt, and internal forces direction of joints. Model tests are considered to be the most reliable approach to obtain the joint stiffness and have been widely used and reported in literature . Herein, the sign convention is as illustrated in Figure , in which the directions of the arrows signify the positive.…”

“…Model tests are considered to be the most reliable approach to obtain the joint stiffness and have been widely used and reported in literature. 22,23,27,29,[33][34][35] Herein, the sign convention is as illustrated in Figure 2, in which the directions of the arrows signify the positive. Based on the test results reported in the literature, Lee et al 14 found that the rational joint stiffness k φ depended on the direction of the bending moment and that the rotational stiffness when a joint is subjected to a negative bending moment (denoted by k φ− ) is only 1/3~1/2 of that when a joint is subjected to a positive bending moment (denoted by k φ+ ).…”

Behaviour of bolted cast iron joints

“…One of the objectives of the overall project was to study the behaviour of grey cast iron (GCI) tunnel linings. To this end, experimental tests were performed on a model tunnel lining (Yu et al, 2017, Afshan et al, 2017 which consisted of six segments bolted together to form a full ring with dimensions scaled to be 50% of those of the running tunnel linings of the Central Line in the LU network ( Figure 1). This was the smallest size that could be manufactured with GCI while maintaining true proportionality of all dimensions, particularly the skin of the segment.…”

“…The purpose of the FE analysis was not to merely reproduce the two-segment test but to provide insight into the behaviour of the joint under different boundary conditions. The ultimate aim of the FE analysis was to help establish the experimental setup for the model tunnel lining (Yu et al, 2017, Afshan et al, 2017. Therefore, the FE mesh employed in the analyses presented here forms part of the FE mesh adopted in the analysis of the full ring, consisting of six bolted GCI segments, as explained later.…”

“…The two-segment experiments described in this paper and the full ring experiments described by Yu et al (2017) focused on the application of load under serviceability limit state. The full ring experiments were subsequently taken to large deformations and failure as detailed by Afshan et al (2017).…”