Study on the Classification and Evaluation Method of the ...cem.uaf.edu/media/138837/caichu-xia.pdf · Study on the Classification and Evaluation Method of the Frost Susceptibility

Department of Geotechnical Engineering

Tongji University ,Shanghai , China

The International Symposium on Systematic Approaches to Environmental Sustainability in Transportation (ISSAEST) , August 2-5, 2015, Fairbanks.

Caichu Xia Jihui Huang

Study on the Classification and Evaluation Method

of the Frost Susceptibility of Rock Mass

4rd, August , 2015

2 Study on the Classification and Evaluation Method of the Frost Susceptibility of Rock Mass C.C. Xia

Layout

BACKGROUND

FROST HEAVE RATIO OF ROCK AND FRACTURES 2

FROST HEAVE RATIO OF SATURATED ROCK MASS 3

CONCLUSION 5

EVALUATION OF THE FROST SUSCEPTIBILITY OF ROCK MASS 4

1


1.BACKGROUND

• The frost heave of rock mass is considered a main reason for frost damage in cold-region constructions.

• Little attention has been paid to the frost heave of rock mass, because the expansion of rock upon freezing is less noticeable due to the constrain of rock itself.

The classification and evaluation of the frost susceptibility of rock mass is significant to the design of constructions in cold regions.

The severe frost damage phenomenon in tunnels


2. FROST HEAVE RATIO OF ROCK AND FRACTURES

2.1 Frost Heave Ratio of Saturated Rock

Tao (1990)

Matsuoka(1990)

Kang et al.(2012)

0.00

0.50

1.00

1.50

2.00

2.50

3.00

3.50

4.00

4.50

0 10 20 30 40 50

Creep of ice

9% volume expansion

of porous water

closedr 02.17%n

Fro

st

he

av

e r

ati

o η

rclo

se

d (

%)

Porous ratio n0 (%)

Fig.1 The experimental relation of frost heave ratio

and porosity of saturated rock under closed system

Closedr 2.17%n

Openr 02.17% n

Frost susceptibility Rock

type

Porous

ratio n0

(%)

Frost heave ratio(%) Openr

Closedr

average

average

Closed

system Closedr

Opened

system Closedr

Frost susceptible

Tuff -1 39.3 0.300 0.536

158.46% Tuff -2 45.5 0.203 0.327

Tuff -3 45.3 0.407 0.552

Non-frost susceptible Andesite 22.5 0.116 0.125 102.11%

Table 1. Frost heave ratio of rocks

The frost heave ratio of

rock is caused by 9%

volumetric expansion of

porous water upon

freezing.

For all kinds of rock: N is porous ratio.

In opened system, the frost heave ratio of the rock increases because of the effect of water migration from the external water resource. It can be evaluated using the following equation:


2. FROST HEAVE RATIO OF ROCK AND FRACTURES

2.2 Frost Heave Ratio of Saturated Fractures

Freezing direction Freezing direction

Ice

Ice

IceIc

eIc

eIc

e

Rock

Rock

Rock

Rock

Rock

Rock

Extrusion

of water

Water

migration

Water

migration

Extrusion of water

Extrusion of water(a)(b)

(e) (f)

(c) (d)

Dilation

Dilation

Dilation

Dilation

No dilation

No dilation

Fig.2. Typical Freezing dilation of saturated fractures upon freezing

In open

fractures:

When rock or the

filler is frost

susceptible:

In closed

fractures:

Water is extruded with the

progression of the freezing

process.

No dilation f 0

Water migrates toward the

freezing zone.

Water is trapped.

Dilation f 3%


3. FROST HEAVE RATIO OF SATURATED ROCK MASS

3.1 Frost Heave Ratio of Various Lithological Rock Masses

z

N

E

e

L

2

1

3

f

Fig. 3 Rock mass with a set of

parallel fractures

The distribution of fractures in rock masses can be simplified as parallel and characterized with an interval L, width e , trend Ɵ, and plunge ɸ , as illustrated in Fig. 3

1

2 r f

3

1 3 0 00 0 sin cos 0 00 0 1 0 1 3 0 0 sin sin 0

0 0 cos0 0 0 0 1 3

e e

L L

1 2 3 r f

1

1 (sin cos sin sin cos )n

i i i i i

i

e en

L L

max f r f f1 3n n

arctan1 arctan 2

f /n ne L is the volume ratio of the fracture.

The value of is calculated for different grades of rock

mass using the parameter provided by the code for design of

road tunnel, the national standard of China.

fn

(1)

(2)

(3)

The frost heave strain of rock mass can be described as a tensor in following equation.

The frost heave ratio of rock mass is described equation 2.

The maximum frost

heave ratio of rock

mass with n set

fracture is described

equation 3.



3.2 Calculation Method of the Frost Heave Ratio of Rock Mass

The frost heave ratios of typical lithological rock masses under open system are computed using Eq. 3 with parameters in Tab. 2 and Tab. 3

The volume ratio of the fracture of Grade V of rock mass is largest, equals to 9.0%.







It can be seen from Tab. 3 that: First， the greater the porous volume of rock, the greater the frost heave ratio, It is less than 1.42% for rock masses composed of non-frost susceptible rock and less than 2.09% for rock masses composed of frost susceptible rock. Second， the frost heave ratio increases with the grade of rock mass. Third， the frost heave ratio increases with the grade of weathering.


4. EVALUATION OF THE FROST SUSCEPTIBILITY OF ROCK MASS

4.1 Water Supply Condition

Water is indispensable for frost heave of rock mass, the water

supply condition should be considered while the evaluation of

frost susceptibility of rock mass.

rock mass

under open system

the rock mass

under closed system

the rock mass can be considered saturated

for frost susceptibility evaluation.

no frost heave occurs



4.2 Classification of The Frost Susceptibility for Rock Mass

The degree of potential damage to the construction as a result of

the frost heave

In the code for engineering geological investigation of frozen ground, the national standard of

China

Three factors in the process

of the classification are

considered:

The elastic modulus of frozen rock is 7.5 times that of frozen

soil

Table 4. The classification of the frost

susceptibility of soil and rock mass according

to their frost heave ratio



4.3 Evaluation Method of Frost Susceptibility

the frost susceptibility of

the rock and fracture filler

the grade of the rock mass

evaluation of the

frost susceptibility

of rock mass

the porosity of the rock

Table 5. Evaluation of the frost susceptibility of

rock mass in force-based design

In table 5, the frost susceptibility of rock mass is classified into 5 degree

of frost susceptibility ，that is, non-frost, weakly, moderately, strongly,

and very strongly susceptible.



4.4 Application

Table 6. Frost susceptibility of surrounding rock of the No. 1 Baimang

Snow Mountain Tunnel using the proposed method

The No. 1 Baimang Snow Mountain Tunnel is located in the Yunnan Province, China.

The altitude of the tunnel is 4070—4113 m above sea level.

The surrounding

rock in the No. 1

Baimang Snow

Mountain Tunnel

is non-frost

susceptible to

strongly frost

susceptible.


EVALUATION OF THE FROST SUSCEPTIBILITY OF ROCK MASS

4.4 Application

Table 7. Frost susceptibility of the surrounding rock of

the Jianglulin tunnel

The Jianglulin Tunnel is located in the Qinghai Province of China.

Most of the

surrounding rock

of the Jianglulin

Tunnel is non-frost

susceptible, but the

surrounding rock

near the fracture

zone and the tunnel

entrance is non-

frost susceptible to

moderately

susceptible.

This evaluation is based on the survey report and should be updated during excavation. These

results provide references for anti-frost damage design of the tunnel.


5. Conclusion

• A calculation method for the frost heave ratio of rock is developed by fitting the experiment data.

• The frost susceptibility of rock mass is classified into 5 types according to its frost heave ratio and based on the frost heaving classification of the soil.

• The frost susceptibility of the surrounding rock is assessed in two cold-region tunnels.

Frost heave ratio of

rock and fractures

Frost heave ratio of

saturated rock mass

Evaluation of the frost

susceptibility of rock mass

Classification and evaluation method of the frost susceptibility

of rock mass


ACKNOWLEDGMENTS

This work has been supported by the National Natural Science Foundation of China (Grant No. 41472248), Key Technologies Research and Development Program of China (No. 2014BAG05B05), and two China Ministry of Communications Western Construction Science & Technology Projects(project numbers: 20113184901070; 2011318799740).


Thank you!

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Study on the Classification and Evaluation Method of the ...cem.uaf.edu/media/138837/caichu-xia.pdf · Study on the Classification and Evaluation Method of the Frost Susceptibility