Numerous deepburied tunnel projects in western China have failed to avoid some
active faults due to key line control. Large deformation and damage phenomena
of surrounding rocks, such as encroachment, offset pressure, collapse, and
bottom failure, often occur across the fault zone, which seriously affect the
safe and sustainable development of tunnel construction and operation. The risk
of large deformation of the tunnel surrounding rock in the fault fracture zone
can be controlled by adopting technical solutions such as advance grouting,
multilayer steel arch passive support, and anchor cable active support.
However, the low strength of the surrounding rock in the fracture zone
contributed to the failure of advance grouting and active support anchoring. Therefore,
the authors introduce a double-gradient grouting
technology to enhance the strength of the surrounding rock of tunnels in the
fault fracture zone, establish a double-gradient
grouting conceptual model, and construct three double-gradient
grouting modes to address the aforementioned problem. The adapting conditions
of the grouting material particle size gradient and the grouting pressure
gradient under specific working conditions are also determined. Finally, the
double-gradient grouting mechanism and its control
effect are explored through theoretical analysis, physical model tests, and
field tests. Results show that the stability of surrounding rock is
substantially affected by the tunnel arch shoulder and the structural stress
with the increase in excavation sequence. Under the action of double-gradient grouting, the grout diffusion effect is good, the
surrounding rock does not suffer large-scale detachment
and damage, and the stress of the rock mass around the tunnel is evenly
distributed. The double-gradient grouting forms a hard
cross-grout vein skeleton, achieving a stress
compensation effect and reducing the surrounding rock mass. The amount of rock
deformation is controlled from the original 3 100 mm to less than 278 mm,
achieving the goals of "zero arch replacement, zero intrusion limit, and
zero inrush", which establishes a theoretical and practical foundation for
the control of large deformation of surrounding rock in similar tunnel
projects.
TAO Zhigang
,
SUN Jihao
,
CAO Zhensheng
,
HU Cai
,
GUO Longji
,
HE Manchao
.
Mechanism of Double-Gradient Grouting for Large Deformation Control of Surrounding Rock in Tunnels Crossing Fault Fracture
Zones
[J]. Tunnel Construction, 2024
, 44(6)
: 1194
-1213
.
DOI: 10.3973/j.issn.2096-4498.2024.06.007
