It is difficult to maintain the pressure of the soil
chamber when the earth pressure balance(EPB) shield tunnels in the waterrich
gravel sandy strata. Therefore, it is necessary to improve the residual soil of
the shield to reduce its permeability and improve the pressure holding effect
of the soil chamber. A case study is conducted on the Xiaocaiyuan stationNorth Railway station section shield tunnel project of Kunming metro
line 4, and the response characteristics of waterrich
gravel sandy strata tunneled by shield under soil conditioning are examined
using numerical simulation and field monitoring data. The results show the
following: (1) With the declining permeability of conditioned soil, the pore
water pressure on excavation face gradually increases, and when the
permeability coefficient of conditioned soil in soil chamber decreases to 5×10-5 cm/s, the
pore water pressure on excavation face will approach to the initial pore water
pressure, which indicates that the conditioned soil with relatively low
permeability has a good waterproof performance. With the rising groundwater
level, the pore water pressure on excavation face gradually increases,
indicating that the waterproof performance of conditioned soil is more
important for the EPB shield tunneling in stratum with high groundwater level.
(2) The permeability of conditioned soil in the Xiaocaiyuan stationNorth Railway station section is relatively low that the excavation
face is of waterresisting condition to some extent. In
the process of shield tunneling, a certain excess pore water pressure will be
developed near the excavation face. The affected area of excess pore water
pressure is mainly 1.5 times of the tunnel diameter in front of the shield. The
soil displacement of the excavation face is far less than that of the
excavation face when instability occurs, indicating that the stability of the
excavation face is high. (3) Due to the low permeability of conditioned soil, a
relatively high excess pore water pressure will be developed around the shield
during tunneling. Meanwhile, the conditioned soil with low permeability can
effectively limit the free seepage of groundwater in front of the excavation
face, which can improve the stability of excavation face, and reduce the
construction ground settlement. (4) With the rising groundwater level, the
ground settlement and excess pore water pressure tend to increase, causing the
support pressure required to maintain the stability of excavation face
increases rapidly, which indicates the groundwater level has notable impact on
the support pressure on excavation face.
WANG Shuying, WANG Lai, YANG Peng, GONG Zhenyu
. Ground Response of Shield Tunneling in WaterRich Gravel Sandy Strata Under Soil Conditioning[J]. Tunnel Construction, 2023
, 43(S1)
: 87
-97
.
DOI: 10.3973/j.issn.2096-4498.2023.S1.011
