In order to study the influence of eccentric unloading
induced by excavation of foundation pit on the existing shield tunnel, a
refined threering shield segment model is established by using software MIDAS/GTS
NX. The initial confining pressure of shield lining ring is calculated based on
the modified routine method, and the additional confining pressure generated by
excavation and unloading of the foundation pit is calculated based on the
Mindlin formula. By applying the total confining pressure on the shield segment
model, the transverse deformation and internal force of the shield lining are
simulated and calculated. Additionally, the ellipticity is adopted as an index
to evaluate the safety of tunnels, and the influence of the eccentric unloading
of the foundation pit on the shield tunnel is studied. The results show that:
(1) During the eccentric unloading process, the oblique "flattening"
effect would be occurred to lining structure and showing "oblique
ellipse" deformation. (2) Due to the stress concentration, the stress is
large at the joint between two segments, and the maximum stress of concrete is
between the adjacent block and the standard block. (3) The maximum stress of
concrete and bolts increases with increasing ellipticity. (4) As the
displacement of the retaining structure of the foundation pit increases, the
stress release coefficient β of the sidewall will
increase gradually, and the horizontal displacement of the tunnel will also
increase. Therefore, during excavation of foundation pits, the displacement of
retaining structure should be strictly controlled to ensure the safety of the
shield tunnel.
LIU Yayu
,
LIU Jiawan
,
WEI Gang
,
HUANG Rui
.
Study on Mechanical Deformation of Shield Tunnel Crosssection
under Eccentric
Unloading of Side Foundation Pit Excavation
[J]. Tunnel Construction, 2020
, 40(9)
: 1333
-1340
.
DOI: 10.3973/j.issn.2096-4498.2020.09.012
