Effect of Undercrossing Shield Tunnels Excavation on Existing Rectangular Pipe-Jacking Tunnels

Abstract

Shield tunneling underneath existing rectangular pipe jacking can often lead to uneven settling. To solve the problem of excessive deformation of the existing underground pedestrian passages, excavated via the rectangular pipe-jacking method due to the adjacent shield tunnels construction beneath, a safety control plan has been proposed based on the shield tunnels constructed beneath a well-type underground pedestrian passage in Hohhot Subway. This plan involves the use of both numerical simulations and on-site monitoring to investigate the deformation patterns of the rectangular pipe jacking. The results suggest that the combined approach of interlayer soil grouting and steel support reinforcement is not only appropriate but also feasible for on-site implementation. It can be concluded that interlayer soil grouting for reinforcement was applied successfully to improve the strength of surrounding soils. Steel support reinforcement is advantageous for controlling the relative deformation between pipe segments. The maximum settlement induced by the shield tunneling for Passage A and Passage B was measured at 17.67 mm and 10.08 mm, respectively, with the final settlement distribution of the rectangular pipe jacking taking on a “W” shape. This study could provide a reference for the design and construction of shield tunnels that undercross existing rectangular pipe-jacking tunnels.

Displacement Monitoring of Subway Tracks and Tunnels According to Adjacent Construction

“…The change in the vertical displacement of Section C (TL-2) was the largest, and the vertical displacement resulting from the adjacent excavation work decreased by approximately 1.634 mm. Table 3 lists the safety evaluation results for the subway tunnel structure [14,[16][17][18][19][20][21][22]. The safety evaluation results of the subway tunnel structure, shown in Table 3, revealed that the minimum value considering the standard deviation for sensor TL-2 in Section A was approximately (−)0.937 mm.…”

“…Table 4 lists the safety evaluation results for the subway track structures. The Seoul Metropolitan Rapid Transit Corporation track maintenance standards were applied to the field maintenance criteria of the track bed settlement sensor [14,[16][17][18][19][20][21][22].…”

A Segmented Calculation Method for Friction Force in Long-Distance Box Jacking Considering the Effect of Lubricant

“…The lubricant significantly influenced the controlling factors of the friction force; there was only one lubricate condition in the whole jacking length in previous numerical simulation studies [28][29][30], which does not reflect the changing lubrication condition in practical construction.…”

“…(2) Construction process: (i) Use the birth and death element method to excavate the soil, simulating the forward jacking of the box via displacement control [28][29][30]. (ii) Neglect axial offset and box deflection during jacking, assuming the box jacks forward in a straight line.…”