In case of fire,
the smoke is discharged by its thermal buoyancy for shallowburied
urban road tunnels with vertical shafts,
but the actual smoke exhaust situation remains unclear. To examine the
smoke diffusion characteristics of the tunnel main body and the smoke exhaust
performance of the shaft in summer,
three 1.58 ×1.58 m2
diesel fire experiments with different ignition points were conducted in two
tunnels in Nanjing in 2019, where the
smoke parameters under the ceiling and at the top/bottom of several shafts are
measured. It was found that the shafts near the fire source had substantial
smoke exhaust, with a maximum smoke
exhaust temperature of 47 ℃, a speed of 5 m/s, and a CO volume fraction of 18×10-4 , whereas shafts far from
the fire source had substantial backward smoke flow. The following are the
results of the analysis: (1) The longitudinal temperature/velocity distribution
of smoke flow under the ceiling obeys the law of power exponent attenuation, and the attenuation coefficient is
significantly influenced by the season,
the ignition position, the
upstream, and the downstream. (2) The
measured smoke exhaust of the shaft decreases gradually as the distance from
the fire source increases, and the
existing prediction models for smoke exhaust does not consider the backward
flow and uneven distribution of smoke. (3) The 〖WT5BX〗Ri′〖WT５《TNR》〗 number of the #6 shaft in the Shuiximen tunnel reaches 10.8 (Test
1) and 1.5 (Test 2), respectively, and the existing model with 〖WT〗Ri′c〖WT５《TNR》〗=1.4 is
unsuitable for evaluating the smoke flow state at the bottom of the shaft.
PENG Tao
,
TONG Yan
,
ZHANG Guangli
,
GONG Yanfeng
,
CHEN Zheng
,
GUO Yizhong
,
MAO Qin
,
LYU Gangyu
,
HUANG Weihao
,
DAI Baolian
. Field Experiments for Natural Smoke Exhaust Through
Vertical Shaft of Urban Road Tunnel Under Fire
Condition in Summer[J]. Tunnel Construction, 2023
, 43(7)
: 1170
-1179
.
DOI: 10.3973/j.issn.2096-4498.2023.07.010
