671017.pdf

p/ x = 0 p/ x = 0

Plane strain

50m 3.5m

3m

10m

50m

pw=2.21M Pa

s=5.97M Pa

III

A-A

(a)

(b)

Figure 16: Plane strain roadway model: (a) boundary conditions;
(b) the finite element mesh.

upon top boundary. No-flow conditions are imposed on the
three boundaries of the rectangular domain. The initial water
pressureontheroadwaysboundariesis0MPa.Allthegov-
erning equations described previously are implemented into
COMSOL Multiphysics, a powerful PDE-based multiphysics
modeling environment. The model is assumed to be in a state
of plane strain (with no change in elastic strain in the vertical
direction) and static mechanical equilibrium.

4.6. Results and Discussion

4.6.1. Stress Distribution.Adverse performance of the rock
mass in the postexcavation stress field may be caused by
either failure of the anisotropic medium or slip on the

50

45

40

35

30

25

20

15

10

5

0

0 5 10 15 20 25 30 35 40 45 50

3

2. 5

2

1. 5

1

0. 5


1. 1558 × 106
   × 106


2. 8969 × 104

Figure 17: Contours of the first principal stress for휃=15∘case.

0

0. 1


1. 2


2. 3


3. 4


4. 5


5. 6


6. 7


7. 8


8. 9

1

1. 1

0 5 1015202530354045 50

Fi

rst

pri

nci

pal

st

ress

(MPa)

Coupled result

Decoupled result

Displacem ent from le side of A-A section (m)

Figure 18: Contrast of first principal stress between coupled and

decoupled model.

weakness planes [ 3 ]. The elastic stress distribution around

the roadways directly influences the deformation of rock and

thus determines the design process.

Figure 17shows the contour of first principal stress cou-

pled with the seepage process. The orientation and magnitude

of maximum principal stress controlled the distribution of the

stress concentration in the heterogeneous media. The sim-

ulation result shows that the principal stress concentration

zones appear mainly in rock surrounding the roadways. There

exist maximum stress concentration areas in the arch foot and

floor. Measures should be taken to control the deformation

and assure the construction safety.

To characterize the response of the stress to the hydraulic

mechanics, a comparison of two scenarios is also presented

as shown inFigure 18. The first principal stress in the stress-

seepage coupled model along the horizontal section A-A耠

where푦=27is compared with a decoupled models.

The result shows that the first principal stress increases

when the seepage process is considered.Figure 19shows