Tertiary semi-diagenetic rocks were sampled from the water-rich section of the Wangjiazhai tunnel for particle screening, X-ray diffraction, and scanning electron microscopy tests. Based on
the dry density of the field samples, remolded samples were prepared for
triaxial compression tests to examine their mineral composition,
microstructure, and mechanical properties. Finally, a construction disaster
analysis of the tunnel was conducted using Mod-Flow
simulation of groundwater levels. The research findings reveal the following:
(1) The grading of tertiary semi-diagenetic rocks from
the Wangjiazhai tunnel is uneven, with weak cementation characteristics leading
to notable water sensitivity and water softening under low moisture content. As
moisture content increases, the shear strength of the samples first rises and
then declines, peaking at 459.03 kPa when the moisture content is 11%. When the
moisture content is below 12%, clay minerals form cements that fill particle
gaps, enhancing sample cohesion. However, with further moisture increase, a
large volume of free water accumulates in the particle gaps, disrupting the
cementation structure and significantly reducing shear strength. (2) The water
inflow simulation results for the Wangjiazhai tunnel indicate that water
inflows in two typical water-rich sections are 2 805
and 5 025 m3/d, respectively, suggesting a high
likelihood of water inflow disasters during tunnel excavation, with substantial
water volumes involved. (3) The physico-mechanical
properties of tertiary semi-diagenetic rocks show
strong water sensitivity and a tendency to soften in water. The high-pressure, water-rich environment, coupled
with engineering disturbances, are the primary factors inducing geological
disasters during the Wangjiazhai tunnel excavation.
XU Hua
,
LIU Yushi
,
WEI Meng
,
WANG Qiuyi
,
ZHANG Haitao
. Engineering Properties of
Tertiary Semi-Diagenetic Rock and Risk
Analysis of Water Inrush Disaster in Wangjiazhai
Tunnel[J]. Tunnel Construction, 2024
, 44(9)
: 1811
-1819
.
DOI: 10.3973/j.issn.2096-4498.2024.09.010
