The cracks of a complete
super-long cast-in-place concrete section of an open-cut tunnel
are investigated to explore its early cracking mechanism. Sensors are embedded
in central lines of the sidewall and roof structure to continuously monitor the
temperature, humidity, and strain. Finally, the early cracking mechanism of the
tunnel concrete is analyzed using temperature stress theories and field crack
investigation. The results reveal the following: (1) The temperature rise of
hydration heat generated by the sidewall and roof structure of a tunnel after
concrete pouring reaches over 40 °C, and the strain
variation trend of the tunnel roof structure is primarily affected by
temperature. (2) The tensile stress caused by the temperature shrinkage in the
cooling stage under the constraint of the construction joint is the main reason
for cracking. The strain difference along the length direction, the nonuniform
shrinkage caused by the temperature difference between the inside and the
surface, and the dry shrinkage caused by the decrease in humidity further
increase the cracking risk. (3) The maximum temperature difference between the
center and the outer surface of the structure is over 12 °C higher than the maximum temperature difference between the center
and the inner surface of the structure, and the outer surface of the structure
is more prone to cracking. (4) The middle part of the section under continuous
external constraint is more prone to cracking. (5) Cracks on the surface of the
structure gradually spread, causing cracks to appear in areas where the risk of
cracking is low.
XIAO Bihong
,
JIANG Li
,
LIANG Zhenyu
,
LIU Tangjin
,
HAO Xiaohu
,
FU Jinyang
,
WANG Shuying
. Field Test on Early
Cracking Mechanism of Super-Long
Section Cast-in-Place Concrete of Open-Cut Tunnels[J]. Tunnel Construction, 2024
, 44(10)
: 1982
-1992
.
DOI: 10.3973/j.issn.2096-4498.2024.10.007
