Abstract
In this paper, a series of parametric three-dimension numerical simulations were carried out to estimate the face stability and to calculate the minimum allowable slurry pressure of pipe jacking tunnel in frozen ground for the first time. In total, 5120 of simulation schemes were done with different ground temperature, diameter and cover thickness of tunnel, cohesion and friction angle of frozen soil. In order to figure out the optimal grouting pressure, 4 groups of additional simulations are computed with the uniform face support pressure of 0.5, 1.0, 1.5 and 2.0 times of horizontal stress, σH, at tunnel axis. The qualitative analysis of heading face deformation mechanism and quantitative analysis between deformation profiles and influential factors were implemented to comprehend the heading face deformation characteristics when conducting pipe jacking tunnel in frozen ground. The results show that ground temperature plays a dominant role to control the face deformation of jacking tunnel in frozen ground. And, factors of tunnel diameter and cover thickness have relatively greater influence on the deformation regulation than that of shearing parameters of frozen soil, cohesion and friction angle. Finally, the minimum allowable slurry pressure for each simulation schemes are obtained, which may be used in construction the pipe jacking tunnel in frozen ground.
Highlights
And perennially frozen ground occupy about 24.91×106 Km2, including glaciers and ice sheet, nearly 25.6% of the land surface in the Northern Hemisphere (Zhang, Barry, Knowles, Ling, & Armstrong, 2003; Zhang, Heginbottom, Barry, & Brown, 2000), where some cities aggregate with the underground construction activities
The identification of minimum allowable slurry pressure refers to the suitable face support pressure applied on the jacking face to ensure that allowable value of y-direction happens on the heading face
The minimum allowable slurry pressure becomes larger with the increasing tunnel diameter and cover thickness, and becomes smaller with the increasing cohesion and friction angle of frozen soil
Summary
And perennially frozen ground occupy about 24.91×106 Km2, including glaciers and ice sheet, nearly 25.6% of the land surface in the Northern Hemisphere (Zhang, Barry, Knowles, Ling, & Armstrong, 2003; Zhang, Heginbottom, Barry, & Brown, 2000), where some cities aggregate with the underground construction activities. Freezing of soil pore moisture increase the strength of frozen soil, which reduces the ground deformation and enhance the stability of tunnel face, compared with that of normal soil, which causes the discrepancy if continuing employing the conventional slurry pipe jacking method in the cold regions. Pipe jacking is a non-destructive trenchless technique used for installing pipes under the ground using a tunnel boring machine and hydraulic jacks located inside a launch jacking pit (Chapman & Ichioka, 1999; Choo & Ong, 2015; Khazaei, Shimada, Kawai, Yotsumoto, & Matsui, 2006; Pipe Jacking Association, 1995; Rahjoo, Najafi, Williammee, & Khankarli, 2012; Shimada, Khazaei, & Matsui, 2004). Till no literature reports about the application of pipe jacking technology in frozen ground can be found. In order to promote the development of slurry pipe jacking technology, this paper is presented to explore the issues esr.ccsenet.org
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