To study the impact of delayed steel support
construction on the axial force of steel supports, displacements, and bending
moments of retaining piles, and internal force of the crown beam, a case study
is conducted on the foundation pit of an opencut and
buried tunnel. Monitoring data is used to analyze the variation laws of
retaining pile displacement and axial force of steel support during delayed
steel support construction. The internal force and the deformation of the
retaining structure under the actual delayed, normal construction, and delayed
conditions of single steel supports are obtained through a numerical
simulation. Moreover, the influence coefficient is introduced to quantify the
impact of delayed steel support construction on the horizontal displacement and
the bending moment of the deep layer of the retaining pile, the axial force of
the steel support, the bending moment, and shear force of the crown beam. The
results show the following: (1) The horizontal displacement of the deep layer
of the retaining pile is mainly affected by the first steel support, and the
influence range is larger than that of earthwork excavation. In contrast, the
influence range of the bending moment of the retaining pile is consistent with
that of earthwork excavation. (2) The crown beam is more susceptible to bending
than shearing. (3) Under the delayed construction, the axial forces of adjacent
steel supports can share part of the axial forces of the delayed steel support,
whereas the sum of axial forces of steel support in the same section is still
less than that of timely support. (4) The bending moment of retaining pile, the
horizontal displacement of deep layer, and the axial force of the steel support
at the junction of earthwork and trenchless excavations are all in their maximum
in the adjacent range.
KONG Qian
,
YANG Rui
. Influence of Delayed Steel Support on Support System
of Foundation Pits[J]. Tunnel Construction, 2021
, 41(12)
: 2113
-2120
.
DOI: 10.3973/j.issn.2096-4498.2021.12.012
