Optimization Study on Longitudinal Joints in Quasi-Rectangular Shield Tunnels

Abstract

There are large bending moments in quasi-rectangular shield tunnels due to their deviation from the circular shape, and as for other types of shield tunnels, the longitudinal joints are the most critical parts in the lining structure. A new type of joint with ductile iron joint panels (DIJPs) was installed in quasi-rectangular tunnels to solve these problems. The distance from the bolts to the segment’s inner surface was improved for better performance under specific bending moment types. Both tests and finite element modeling (FEM) simulations were conducted to investigate the effect of the bolt position improvements. The resistances to crack appearance increased by 33.6% and 18.0% for positive and negative moment cases, respectively. The resistances to crack penetration increased by 13.8% and 18.4% for positive and negative cases. From the FEM approach, it was found that the behavior of the joint under the design bending moment range can be divided into three stages, whereby the bolts are only active from the second stage on. The effects of other optimizing methods, such as enhancement of concrete properties and increase of bolt diameters and numbers, are explored. Through comparison, it is believed that optimizing the joint section to increase the lever arm between bolts and the compression zone can improve the joint behavior most effectively. This optimization direction is recommended when designing a shield tunnel joint with DIJPs.

Experimental and Theoretical Investigations of the Mechanical Behavior of Column-Free Quasi-Rectangular Segmental Tunnel Linings

“…Joint contact plates have also been partially extended from 450 mm to 550 mm to increase the height of joint surfaces [17]. Inspired by research findings indicating that bolt movement can effectively enhance the mechanical behavior of longitudinal joints and tunnel linings [8,9], corresponding measures are adopted in the design of the joints of the column-free QRST structure. Bolts of positive moment joints (intrados tension) have been inwardly repositioned, whereas bolts of negative moment joints have been outwardly repositioned, as shown in Figure 4.…”

“…Compared to circular segmental tunnels, quasi-rectangular segmental tunnels (QRSTs) exhibit characteristics of high space utilization with strong applicability in high-density urban areas. The applicability of typical QRST structures (with columns) has been substantiated through a series of joint and structural experimental investigations [8,9], leading to successful applications of QRSTs in numerous metro projects [7]. Due to the need for transportation network planning, it is necessary to set up a crossover section in a large two-way tunnel.…”

Influence of Interior Column on the Behaviour of Quasi-Rectangular Tunnel

“…Compared with a large circular tunnel, a quasirectangular tunnel allows for increasing the efficiency of underground space utilization by around 20% (Liu et al, 2018c;Zhang et al, 2020), and the tunnel depth can also be reduced by a corresponding proportion. Studies on the behavior of quasi-rectangular tunnel linings can be conducted using experimental methods (Liu et al, 2018a;2018b), analytical methods (Yuhang et al, 2019;Zhang et al, 2020;2022), and numerical methods (Liu et al, 2018a;Huang et al, 2018;Zhu et al, 2018;Nguyen et al, 2021;Zhang et al, 2021). Liu et al (2018aLiu et al ( , 2018b conducted a 1:1 scale structural experiment to investigate the mechanical behavior of the segmental lining for quasi-rectangular tunnels (Figure 1).…”

Material reduced tunnel lining segments for moderately swelling soils

“…24,25 Thus, on these, the future-oriented design should focus. 26 Figure 1 illustrates the generic cross-section of a segmental lining subjected to typical boundary conditions and introduces potential design alternatives with reduced thickness. The focus is clearly set on mechanized tunneling in general and on often faced moderately squeezing/ swelling ground conditions in particular.…”

“…Especially joints are sensitive to damage initiation 24,25 . Thus, on these, the future‐oriented design should focus 26 …”