There exist many technical
issues of thickly-filled open-cut tunnel with highly-filled and deeply-excavated foundation, such as high load-bearing
capacity of structure, complex foundation treatment, and uneven settlement
deformation. A case study is conducted on the Guangzhou-Zhanjiang high-speed railway, and the
structural load bearing characteristics of open-cut
tunnel and pile arrangement plans are analyzed, proposing a rational structural
design plan. The load bearing capacity calculation methods of the pile in
various specifications are compared, and the evolution pattern of negative
frictional resistance around the pile under the action of soil properties and
stacking pressure is examined, clarifying the calculation principles load
bearing capacity of pile. Additionally, the calculation methods of the
foundation settlement in composite strata are summarized, and feasibility
assessment is conducted, proposing settlement control measures in transition
section between filling and excavation. The research results reveal the
following: (1) Inclined wall, flat bottom, and large arch foot structure with
large-diameter and large span piles should be adopted
for the open-cut tunnel in the filled section, whereas
straight wall and inverted arch structure should be adopted for that in the
excavated section. (2) The allowable stress method is more conservative than
the probabilistic limit state method in calculating pile foundation load. The
negative friction resistance around the pile is dissipated, thus a single-time backfill thickness should be controlled and the unfavorable
strata around piles should be conditioned. (3) The foundation settlement of the
open-cut tunnel in the filled section can be calculated
as the rigid piles and using the pile compression method. The plain concrete
piles can be used to effectively connect drilling piles and cement fly-ash gravel piles, and the thickness of the pile top cushion can be
adjusted to achieve a uniform transition of foundation settlement.
FENG Tianwei
,
MENG Qingyu
,
ZHANG Qingbo
,
MA Zhifu
. Key Design Technology of
Thickly-Filled Open-Cut Tunnel of High-Speed Railway With Highly-Filled and Deeply-Excavated Foundation[J]. Tunnel Construction, 2024
, 44(S2)
: 406
-415
.
DOI: 10.3973/j.issn.2096-4498.2024.S2.041
