关键词: 敞开式TBM　, 数值模拟　, 破坏机制　, 滞后支护　, 支护优化

Abstract: The open-type tunnel boring machine (TBM) has been widely adopted in underground coal mine roadway excavation
projects,owing to its significant advantages including high tunneling efficiency,minimal disturbance to surrounding
rock,superior construction safety,and strong adaptability to complex geological conditions. However,in the engineering practice
of TBM-driven roadway construction,particularly in deep coal mines characterized by high in-situ stress and strong mining disturbance,
roof collapse,instability,and other failure accidents are frequently encountered during the delayed support stage following
TBM excavation. This prominent engineering challenge has become a key technical bottleneck restricting the large-scale
application of TBM tunneling technology in coal mine roadway construction,and has also severely challenged the precise control
of surrounding rock stability as well as the safe and efficient production of underground coal mines. To address the above technical
constraints,the TBM excavation project of the floor gas drainage roadway in Wangfeng Coal Mine,Shaanxi Province,China,
is taken as the engineering background and research object in this paper. As a core infrastructure for mine gas disaster prevention
and control,the floor gas drainage roadway has strict requirements for the long-term stability of its surrounding rock. In
addition,the roadway is subject to strong horizontal tectonic stress at the project site,which further intensifies the difficulty of
surrounding rock control during the delayed support stage. A three-dimensional numerical calculation model consistent with the actual engineering geological conditions and TBM excavation process was established. Using this model,the evolution laws of
the plastic zone,displacement field,and stress field of the surrounding rock in the TBM-excavated roadway under horizontal
tectonic stress were systematically analyzed. On this basis,the control performance of two support schemes full bolt support and
bolt-cable combined support on roadway roof deformation,plastic zone expansion range,and surrounding rock stress distribution
under different delayed support distances was systematically compared and quantitatively evaluated. Based on the numerical
simulation results and field engineering requirements,an optimized delayed bolt-cable combined support scheme tailored to the
TBM-driven roadway of this project was proposed,and a full-scale field industrial test was conducted. The engineering reliability,
surrounding rock control effect,and long-term service performance of the optimized scheme were comprehensively verified
via continuous field monitoring data. The key research findings are summarized as follows:① Under horizontal tectonic stress,
an oblate plastic failure zone dominated by shear plastic damage is formed in the surrounding rock of the TBM-excavated roadway.
The continuous development and expansion of this plastic failure will not only induce large-scale fragmentation and loosening
of the roadway roof,but also trigger significant convergence deformation of the two roadway ribs,this is the intrinsic mechanism
leading to roof collapse and instability accidents during the delayed support stage. ② For the full bolt delayed support
scheme,the anchorage section of the rock bolts cannot fully penetrate the roof plastic zone,resulting in insufficient effective anchoring
force;thus,its surrounding rock control effect cannot meet the safety requirements of engineering construction. For the
bolt-cable combined support scheme,the surrounding rock control performance gradually degrades as the delayed support distance
increases;accordingly,the reasonable delayed support distance should be strictly controlled within 4 m to ensure active
and effective control of the roadway surrounding rock. ③ At the same delayed support distance,the optimal surrounding rock
control effect is achieved by the bolt-cable combined support scheme compared with the full bolt support scheme:the maximum
roof displacement of the roadway is reduced by 41. 71%,and the shear plastic zone area is reduced by 46. 25% relative to the
unsupported scheme. In addition,the compressive stress level of the roadway surrounding rock under the bolt-cable combined
support is significantly elevated,and it is fully demonstrated that the proposed delayed support scheme can effectively improve
the self-bearing capacity of the surrounding rock mass and realize active and stable control of the surrounding rock in TBMdriven
roadways. It is confirmed by the field monitoring results that the optimized delayed bolt-cable combined support system
can effectively restrain roof deformation of the TBM-driven roadway,with the full-section deformation of the roadway controlled
within the allowable range for engineering safety. As a result,the on-site engineering problem of frequent roof collapse and instability
is successfully solved,and the safe and efficient tunneling of the TBM roadway is ensured. The research methods and
conclusions presented in this paper can not only provide direct technical guidance and field basis for surrounding rock control
in this project,but also serve as an important theoretical reference and engineering paradigm for the design and optimization of
delayed support schemes for similar TBM-driven roadways in deep,high-stress coal mines.