The influence law of local expansion of expansive
loess on the safety of tunnel support is key to keeping surrounding rock
stable. Based on a loess tunnel, the temperature stress field is built to
simulate the humidity stress field generated by the humidification of expansive
loess, and thermalmechanical coupling module of FLAC
3D software is used to study the influence of expansive loess on the safety of
support under the condition of local expansion (tunnel arch, arch waist, side
wall, and inverted arch) when encountering water. The results show that: (1)
Structure deformation in local expansion area is obvious; inverted arch deforms
obviously not only when it is located in local expansion area, but also when
affected by the expansion of other parts, thus it is the main deformation
position; under the effect of local expansion, the deformation of arch crown is
the largest, the deformation of the arch waist and the side wall is the second,
and the wall foundation is the weakest. (2)The maximum principal stress of
support in waterimmersed expansive area increases with
the expansive force, and most of them increase linearly; when the expansive
force is between 200 kPa and 300 kPa, the tensile stress of support structure
in expansive area exceeds the standard value of C25 concrete axis tensile
strength（1.27 MPa）. (3)The
failure of surrounding rock in local expansion area is mainly tensile failure;
the surrounding rock under inverted arch shows tensile failure under its own expansion
and local expansion of other parts, which is the stress concentration part. (4)
By using the method of structural safety factor, the maximum expansion pressure
and deformation value of different parts of the structure are determined; the
maximum local expansion pressure of the tunnel arch, arch waist, side wall， and invert arch are 223 kPa, 260 kPa, 292 kPa， and 238 kPa respectively, and the corresponding deformation is 87
mm, 36 mm, 47 mm， and 27 mm respectively.
ZHANG Yiteng, SUN Xingliang, YANG Bo, SUN Yunjie
. Influence of Local Expansion on Safety of Tunnel
Support[J]. Tunnel Construction, 2021
, 41(S2)
: 306
-312
.
DOI: 10.3973/j.issn.2096-4498.2021.S2.039
