Research on Stress Characteristics of Segment Structure during the Construction of the Large-Diameter Shield Tunnel and Cross-Passage

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.

Centrifugal Model Test Study on the Mechanical Characteristics of Shield Tunnels Influenced by Different Types of Openings for Cross Passages

“…(4) Structural stress. Previous studies have demonstrated that the influence of the opening on the mainline tunnel stress is concentrated at the opening position and 1-2 rings nearby [12,17]. Considering the symmetry, for each opening, three couples of strain gauges (one inside and one outside) are arranged longitudinally along the tunnel, to analyze the stress concentration degree and influence range, as shown in Figure 6a.…”

“…The research methods to investigate the mechanical characteristics, e.g., stress state, deformation pattern of shield tunnels include theoretical analysis [13][14][15], numerical simulations [1,2,16,17], field monitoring [2][3][4][5], and model tests [18][19][20][21]. The combination of the cross passages and main tunnels is a complex three-dimensional structure, which is unrealistic to utilize classical theoretical methods such as beam-spring models or homogeneous ring models to perform analysis.…”

“…Three-dimensional models were established to investigate the structural behavior of the tunnel openings, and the results showed that a lintel effectively transfers the load above the opening to the adjacent lining rings [8]. Tan et al (2020) [17] established threedimensional discontinuous contact numerical tunnel models, including segments, joints, and bolts, to investigate the mechanical characteristics of the mainline tunnel at the opening. However, it is still challenging to accurately simulate the details of the segmental joints such as bolts and bolt holes, mortises and tenons, and sealing liners for problems involving tunnels of a larger scale.…”

“…The maximum measured increment of earth pressures was about 0.2 MPa, smaller than the anticipated value. Tan et al (2020) [17] conducted field tests of earth pressures, stresses of steel bars and concrete, and the internal forces of bolts on the segmental linings around the opening for the cross passages. The stress characteristics and dangerous sections were identified according to the results of the field tests.…”

Field Tests on the Stress Characteristics of Enriched Water Tunnel Invert

“…Thus, many studies have focused on the tunnel structure and surrounding rock failure. Tan et al based on the Wangjing tunnel project studied 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 [4]. Fang et al and Zhang et al calculated the seepage-induced effective stress around a tunnel in an elastic half-plane [5][6][7].…”