The authors present a case study to investigate the
damage and destabilization mechanisms of broken and soft surrounding rocks and
provide a reasonable support scheme design for an inclined shaft bored using a
tunnel boring machine(TBM). This study is conducted on the Kekegai subinclined
shaft bored by a TBM in Yulin, China. A discreteelementsimulation software, UDEC, is employed to analyze the stability of
the surrounding rocks as well as the support effects under four conditions: no
support, anchornetwork shotcrete support, anchornetwork shotcrete cable support, and anchornetwork
shotcrete cable + steel belt support. Based on the numerical results, a supportoptimization scheme is proposed and applied in practice.
Accordingly, the following results are verified: (1) The rock destabilization
in the TBM tunnel demonstrates ovalshaped plastic
damage, which is dominated by shear plasticity and controlled by tensile
plasticity, requiring the timely adoption of support means. (2) The anchor rod,
anchor cable, shotcrete, and steel belt support can effectively limit the
deformation and damage to the surrounding rocks. Therefore, the anchornetwork shotcrete cable + steel belt support exhibits the best
support effect compared with all the other support types, with a reduction of
50.9% and 99.85% of the roof displacement and the tensile plastic area of the
surrounding rocks, respectively, compared with those of the system without any
support. The anchornetwork shotcrete cable scheme is
finally used as the support solution, and a Wtype
steel belt is added to strengthen the support in the roof area, which displays
a falling risk. The adopted support scheme can effectively control the
deformation of shallow surrounding rocks and plastic expansion of deep
surrounding rocks, thereby achieving precontrol of
sudden falls.
LI Anyun
,
ZHANG Kai
,
XU Jinfeng
,
XIE Xiongyao
,
KANG Yuanfeng
. Stability of Surrounding Rock and Support Optimization
of a Broken SoftRockInclined
Shaft Bored by Tunnel Boring Machine: A Case Study of
Kekegai SubInclined Shaft[J]. Tunnel Construction, 2023
, 43(11)
: 1924
-1934
.
DOI: 10.3973/j.issn.2096-4498.2023.11.012
