The cross-sectional ovalization of tunnels is often neglected in the analysis
of longitudinal deformation in existing shield tunnels caused by the excavation
of an overlying foundation pit. The authors propose a discontinuous deformation
differential solution that accounts for the influence of cross-sectional ovalization. A two-stage
analytical approach is adopted. First, the additional stresses due to
excavation unloading are computed using a modified Mindlin solution. The
existing tunnel is then modeled as a short Euler-Bernoulli
beam on a Pasternak foundation. The rotational stiffness of tunnel joints is
derived from a parametric expression considering cross-sectional
ovalization. The proposed method is validated through two engineering case
studies. Furthermore, the influence of joint stiffness and the number of
longitudinal reinforcement rings on the tunnel′s
longitudinal deformation is analyzed. The results show that: (1) The proposed solution
aligns well with measured tunnel uplift, while ignoring cross-sectional ovalization underestimates uplift displacement and joint
opening and overestimates joint dislocation. For large excavation areas,
ovalization has a diminished effect on uplift displacement but still
significantly affects joint deformation. (2) Increasing joint rotational
stiffness reduces uplift displacement and joint opening but increases joint
dislocation. Increasing shear stiffness reduces both uplift displacement and
joint dislocation but increases joint opening. (3) Longitudinal reinforcement
effectively mitigates tunnel uplift due to overcrossing excavation; however,
the marginal benefit decreases as the number of reinforcement rings increases.
DENG Wenwu
,
HUANG Dawei
,
SONG Yi
,
ZHANG Zhiwei
. Differential Solution for
Longitudinal Deformation of Existing
Shield Tunnel Induced by Upper Excavation of a
Foundation Pit Considering Cross-Sectional Ovalization[J]. Tunnel Construction, 2025
, 45(6)
: 1120
-1130
.
DOI: 10.3973/j.issn.2096-4498.2025.06.007
