The employment of large-scale mechanized tunnel construction represents an effective method
to ensure the safety, efficiency, and environmental sustainability of tunnel
excavation. Typically, this method involves full-face
tunneling, characterized by large excavation areas and rapid excavation rates,
often precipitating face instability. The stability of the tunnel face,
consequently, holds paramount importance for the overall safety of tunnel
construction. Accordingly, the authors introduce the material point method to
the investigation of the various stability modes and failure characteristics of
the tunnel face. Initially, the numerical model utilizing the material point
method is validated through a comparative analysis with experimental results,
revealing a strong concordance in the magnitude, extent, and evolution of shear
strain zones within the surrounding rock across both models. Subsequently,
considering factors such as the unsupported length (L), the cohesion (c) of the
surrounding rock, and the friction angle (φ), a total of 120 distinct
working conditions are simulated using the material point method model. The
results indicate that: (1) The stability of tunnel face presents three modes,
stable face (Mode Ⅰ), temporarily stable face (Mode Ⅱ), and unstable face (Mode Ⅲ). The failure
mode for Mode Ⅱ is characterized by a combination of
parabolic or elliptical shapes with rectangular forms, while Mode Ⅲ exhibits an elliptical shape accompanied by a logarithmic spiral.
(2) A critical boundary exists between c/D/γ and φ (where D represents
the tunnel diameter and γ represents
the bulk density). When c/D/γ≤0. 09 or φ≤11°, the
stability mode of the tunnel face under varying L consistently aligns with Mode Ⅲ stability. Moreover, an increase in L correlates with a reduced likelihood
of encountering Mode Ⅱ stability.
WANG Mingnian
,
YANG Henghong
,
WANG Xu
,
LIU Siyang
,
YU Li
,
LIU Dagang
. Material Point Method
Analysis for Stability of Tunnel Face in Sandy Stratum[J]. Tunnel Construction, 2024
, 44(S2)
: 73
-83
.
DOI: 10.3973/j.issn.2096-4498.2024.S2.007
