암반 분류법

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lecture_06 암반의 분류법

Rock Classification System

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MME_326암반공학 lecture_06_rock_classification_system 2

암반 분류법

암반역학과 암반공학의 차이점 (1) 암반역학(Rock mechanics)

- 암석 또는 암반을 매개체로 한 공학에 필요한 기본적인 역학을 다 루는 학문

(2) 암반공학(Rock engineering)

- 암반역학의 기본원리에 기초하여 실제로 공학적인 문제들을 풀기 위한 학문

세계적으로 가장 통용되는 분류법 - RMR 분류법(Rock Mass Rating) - Q 분류법(Q-system)

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RMR 분류법

RMR 분류법에서의 6가지 점수화 요소

(1) 암석의 일축압축강도 (strength of the Rock) (2) RQD

(3) 불연속면의 간격 (spacing of joints) (4) 불연속면의 상태 (condition of joint) (5) 지하수의 상태 (groundwater condition)

(6) 불연속면의 방향성의 영향을 고려하기 위한 보정

표 A : 위의 5가지 분류요소 상태에 따른 RMR 점수

표 B : 불연속면의 상태를 (표 A의 4항) 구체적으로 평가하기 위한 세부표

표 C : 불연속면이 터널공사에 미치는 영향을 구분하기 위한 세부표 (표 D에서 사용) 표 D : 불연속면의 방향성을 고려한 보정계수 (시설물별로 점수가 다르다)

표 E 및 F : 표 A~D로부터 합산된 RMR값에 따른 암반의 분류 종합 (Ⅰ~Ⅴ등급까지)

5

1

( )

i

RMR





암반분류 요소에 따른 점수 + 불연속면의 방향성 효과에 따른 보정

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RMR 분류법

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RMR 분류법

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RMR 분류법

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7

RMR 분류법 – 터널 설계에의 적용

표 7.3

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Discontinuities and Rock Mass

Example `1

Item Value or Description Rating

Strength of Rock 150 MPa

RQD 70%

Joint Spacing 0.5 m

Condition of Joints

Slightly rough surfaces Separation<1mm Hard joint wall rock

Groundwater Condition Water under moderate pressure

Total Score

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9

Discontinuities and Rock Mass

The tunnel has been oriented such that the dominant joint set strikes perpendicular to the tunnel axis with a dip of 30°against the drive direction.

This situation is described as from table 6.

Subsequently, a rating adjustment of is obtained and final score is

Finally, the rock mass is placed at Class

Item Value or Description Rating

Strength of Rock 150 MPa

RQD 70%

Joint Spacing 0.5 m

Condition of Joints

Slightly rough surfaces Separation<1mm Hard joint wall rock Groundwater Condition Water under moderate pressure

Total Score

69

59 unfavorable

III -10

12 13

20

4

20

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Q-분류법

Q-분류법의 6가지 요소 (1) RQD

(2) 불연속면군 (discontinuity set)

(3) 가장 불리한 불연속면의 거칠기 상태

(4) 가장 약한 불연속면의 변질상태와 충진상태 (5) 지하수 유입상태

(6) 응력조건

: `

: 응력감소계수 (stress reduction factor)

r w

n a

J J

Q RQD

J J SRF

  

J

n

J

r

J

a

J

w

SRF

9 ln 44

RMR



Q



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11

Discontinuities and Rock Mass

Q – RMR Relationship

Suggested by Bieniawski

RMR = 9 lnQ + 44

E _m – Q – RMR Relationship

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13

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암반분류법의 적용성

암반역학에서 응용 (암반정수 추정) 1) ^{강도론에의 이용}

(단, GSI > 25 인 경우)  Use in Hoek-Brown equation

2) 변형문제에의 이용

(단 RMR > 50 인 경우)

(단, GSI > 25, < 100 MPa 인 경우)

'

89 5

GSI



RMR



2 100( )

E

m 

RMR



GPa

' 89 15

10 40 ( ) 100

RMR c

E

m _



^^^_ ^ ^^^_

GPa



c

10 10

10 log

Q



E

_m  40 log

Q

25 log10

E

m 

Q

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암반분류법의 적용성

터널과 지하공간에의 이용

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암반분류법의 적용성

터널과 지하공간에의 이용

ESR : 굴착지보비 (Excavation Support Ratio)

= ,

ESR

스팬 또는 터널의 직경

터널의 등가직경

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Discontinuities and Rock Mass

Simplified Diagram for Design of Rock Support based on Q-System

Estimated Q values can be used for the design of temporary support of tunnel excavation

Equivalent Dimension (D _e ) = max (span, diameter or height (m))

ESR (Excavation Support Ratio)

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Discontinuities and Rock Mass

Excavation Support Ratio (ESR)

Excavation Category ESR

Temporary mine openings 3 ~ 5

Permanent mine openings, water tunnels for hydro power (excluding high

pressure penstocks) pilot tunnels, drifts and headings for large excavation 1.6 Storage rooms, water treatment plants, minor road and railway tunnels, surge

chambers, access tunnels 1.3

Power stations, major road and railway tunnels, civil defense chambers,

portals, intersections 1.0

Underground nuclear power stations, railway stations, sports and public

facilities, factories 0.8

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Discontinuities and Rock Mass

Example 2

A permanent mine opening is to be excavated in the limestone footwall of a lead-zinc ore body and it is required to find the span which can be left unsupported. The analysis is carried out as follows;

No. Item Description Value

1 Rock Quality Good

2 Joint Sets Two sets

3 Joint Roughness Rough

4 Joint Alteration Clay gouge

5 Joint Water Large inflow

6 Stress Reduction Medium stress

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Discontinuities and Rock Mass

Example 2

A permanent mine opening is to be excavated in the limestone footwall of a lead-zinc ore body and it is required to find the span which can be left unsupported. The analysis is carried out as follows;

No. Item Description Value

1 Rock Quality Good RQD =

2 Joint Sets Two sets J

_n

=

3 Joint Roughness Rough J

_r

=

4 Joint Alteration Clay gouge J

_a

=

5 Joint Water Large inflow J

_w

=

6 Stress Reduction Medium stress SRF =

80%

4 0.33 3

1.0 4

Q = ( ) х ( ) х ( ) ^RQD

J

_n

J

_r

J

_a

J

_w

SRF

= ( ) х ( ) х ( ) = ⁸⁰

4 3 4

0.33 1 5

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Discontinuities and Rock Mass

The maximum equivalent dimension (D

_e

) for an

unsupported excavation in this rock is 4m

ESR of a permanent mine opening is

1.6

Maximum unsupported span is

6.4m

Excavation Category ESR

Permanent mine openings, water tunnels for hydro power (excluding high pressure penstocks) pilot tunnels, drifts and

headings for large excavation

1.6

Storage rooms, water treatment plants, minor road and railway

tunnels, surge chambers, access tunnels 1.3 Power stations, major road and railway tunnels, civil defense

chambers, portals, intersections 1.0

Underground nuclear power stations, railway stations, sports and

public facilities, factories 0.8

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Discontinuities and Rock Mass

Example 3

What rock support would be necessary for a road tunnel when the diameter of tunnel is 5m and Q=1?

Excavation Category ESR

Permanent mine openings, water tunnels for hydro power (excluding high pressure penstocks) pilot tunnels, drifts and headings for large excavation

1.6

Storage rooms, water treatment plants, minor road and railway

tunnels, surge chambers, access tunnels 1.3 Power stations, major road and railway tunnels, civil defense

chambers, portals, intersections 1.0

Underground nuclear power stations, railway stations, sports and

public facilities, factories 0.8

ESR = 1.0

D _e = diameter/ESR = 5/1.0

= 5

Bolts and fibercrete

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암반분류법의 적용성

사면안정에의 응용 SMR 분류법

(1) : 사면과 불연속면 사이의 주향의 상관성을 고려하는 요소 (2) : 평면파괴(plane failure)인 경우 불연속면의 경사각

(평면파괴의 정의는 8장에서 서술할 것임)

(3) : 사면의 경사와 불연속면의 경사의 상관성을 고려하는 요소 (4) : 사면굴착방법의 영향으로 고려하는 요소

1 2 3 4

( )

slope basic

SMR



RMR



RMR



F F F

  

F

1

F

2

F

3

F

4

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암반분류법의 적용성

SMR 분류법

암반 분류법

lecture_06 암반의 분류법

Rock Classification System

암반 분류법

RMR 분류법

RMR



RMR 분류법

RMR 분류법

RMR 분류법

RMR 분류법 – 터널 설계에의 적용

Discontinuities and Rock Mass

Example `1

Item Value or Description Rating

Discontinuities and Rock Mass

69

59

unfavorable

III -10

12 13

20

4

20

Q-분류법

J J

Q RQD

J J SRF

J

J

J

J

SRF

RMR

Q

Discontinuities and Rock Mass

Q – RMR Relationship

RMR = 9 lnQ + 44

E m – Q – RMR Relationship

암반분류법의 적용성

GSI

RMR

E

RMR

GPa

E



GPa



Q

E

Q

E

Q

암반분류법의 적용성

암반분류법의 적용성

= ,

ESR

스팬 또는 터널의 직경

터널의 등가직경

Discontinuities and Rock Mass

Simplified Diagram for Design of Rock Support based on Q-System

Equivalent Dimension (D e ) = max (span, diameter or height (m))

ESR (Excavation Support Ratio)

Discontinuities and Rock Mass

Excavation Support Ratio (ESR)

Excavation Category ESR

Discontinuities and Rock Mass

Example 2

No. Item Description Value

1 Rock Quality Good

2 Joint Sets Two sets

3 Joint Roughness Rough

4 Joint Alteration Clay gouge

5 Joint Water Large inflow

6 Stress Reduction Medium stress

Discontinuities and Rock Mass

Example 2

No. Item Description Value

1 Rock Quality Good RQD =

2 Joint Sets Two sets J

E _m – Q – RMR Relationship

Equivalent Dimension (D _e ) = max (span, diameter or height (m))

Q = ( ) х ( ) х ( ) ^RQD

= ( ) х ( ) х ( ) = ⁸⁰

_e

D _e = diameter/ESR = 5/1.0