Abstract
The longitudinal gradient existed in shield-driven tunnel crossing river or channel has a longitudinal gradient, which is often ignored in most stability analyses of the tunnel face. Considering the influence of the longitudinal gradient into A(a) continuous velocity field, the present paper, conducting a limit analysis of the tunnel face in undrained clay, adopted to yield the upper-bound solutions of the limit pressure supporting on a three-dimensional tunnel face. The least upper bounds of the collapse and blow-out pressures can be obtained by conducting an optimization procedure. These upper-bound solutions are given in the design charts, which provide a simple way to assess the range of the limit pressure in practice. The influence of the longitudinal gradient becomes more significant with the increase of γD/su and C/D. The blow-out pressure for tunneling in a downward movement could be overestimated and the collapse pressure for tunneling in an upward movement could be conversely underestimated, with ignoring the influence of the longitudinal gradient.
Highlights
Shield-driven excavation is widely used in a subway or road tunnel crossing the river or channel
Their studies are limited to the excavations in a horizontal ground surface, and they cannot be used to predict the supporting pressure on the face of tunnels crossing a river or channel. e purpose of this study is to investigate the influence of the longitudinal gradient on face stability of the tunnel crossing the river or channel. e continuous velocity field of Mollon et al [14] is adopted here to obtain the upper-bound solutions of supporting pressure of circular tunnels in undrained clay
Based on the continuous velocity field of the tunnel face, an analytical approach is derived for the face stability of the shield-driven tunnel with a longitudinal gradient
Summary
Shield-driven excavation is widely used in a subway or road tunnel crossing the river or channel. There are many shielddriven excavations in construction for railway and gas-insulated line (GIL) crossing the river, and the longitudinal gradient may exceed 5% and even reach 10%. Advances in Civil Engineering field proposed by Mollon et al [14] to analyze the face stability of longitudinally inclined tunnels in anisotropic purely cohesive soils. Their studies are limited to the excavations in a horizontal ground surface, and they cannot be used to predict the supporting pressure on the face of tunnels crossing a river or channel. Their studies are limited to the excavations in a horizontal ground surface, and they cannot be used to predict the supporting pressure on the face of tunnels crossing a river or channel. e purpose of this study is to investigate the influence of the longitudinal gradient on face stability of the tunnel crossing the river or channel. e continuous velocity field of Mollon et al [14] is adopted here to obtain the upper-bound solutions of supporting pressure of circular tunnels in undrained clay
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