Abstract
With the intensive development of China’s high-speed railway network and intercity railway network, the construction of the large-diameter shield tunnels and cross-passages is gradually increasing. The construction of large diameter shield tunnels and the excavation of cross-passages puts forward higher requirements for the stability and safety of segment structure. Based on the Wangjing tunnel project, this paper studies the segment displacement and mechanical response of the shield tunnel with a diameter of 10.5 m in the process of shield construction and cross-passage construction. The results show that during the construction of large diameter shield tunnels, the vault and invert produce inward displacement, the invert uplift usually is more severe than the vault settlement, and the arch waist on both sides produces outward displacement. Near the segment K (capping block), the mechanical performance of the segment is close to that of the hinge or chain rod, which can only effectively transmit the axial force but cannot resist the bending moment and shear force. During construction of the cross-passage, the maximum deformation and stress of shield tunnel segment are symmetrically located at the interface of the main tunnel and cross-passage. The upper and lower edges of the segment at the interface tend to change from compression to tension. At the same time, the steel bars on the inside and outside of the segment vault and the arch waist change from compressive stress to tensile stress, which can easily lead to segment damage, so these positions can be reinforced by erecting section steel frames before construction.
Highlights
With the rapid development of infrastructure construction such as highways, railways and urban rail transit, the segment design technology of shield tunnels in China tends to mature
From the test data of the left-line tunnel, it can be seen that the surrounding rock pressure of the segment around the cross-passage was between 0.06 and0.56 MPa, and the maximum value of surrounding rock pressure was in the ring 673 segment
The maximum value occurred in ring 672, and the minimum occurred in ring 670
Summary
With the rapid development of infrastructure construction such as highways, railways and urban rail transit, the segment design technology of shield tunnels in China tends to mature. During the construction of cross-passage of a standard shield tunnel (the outer diameter of the tunnel is 4.1–6.2 m), the segment will produce an additional horizontal displacement moving in the direction of the connecting channel [13,14]. None of the above studies involve the influence of large-diameter shield tunnels construction and cross-passage construction on segments, which restricts the technical progress of tunnel engineering. In this paper, based on the Wangjing tunnel of the Beijing–Shenyang high-speed railway with a diameter of 10.9 m, the mechanical characteristics of the segment structure of a large-diameter railway shield tunnel and the mechanical response of the segment structure of large-diameter railway shield tunnel during the construction of a cross-passage were investigated by comparing the results of numerical analysis with the field testing data. The research results of this paper are helpful in improving the quality of tunneling and design [20]
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