1

Flexible retaining structure for evaluation of debris-flow hazards mitigation

NSC 95-2622-E-324-009

95 11 01~ 96 10 31

0.30.450.5580%0.3560.3%40% 0.6598.88%0.3560%

Abstract

The retaining structure adopted by this research has both functions of a permeably flexible energy dissipation structure and a previous rock gabion dam. As it is not full of soils and sediments in the retaining structure, then it is the function of flexible energy dissipation structure. As it is full of soils and sediments in the retaining structure, then it becomes the function of rock gabion dam naturally. In coordination with the Program to Upgrade Industrial Technology and Enhance Human Resources of National Science Council, we set up an on-site debris-flow retaining structure in the upstream of Shan Pu Keng River, Shanan Village, Shueili Township, Nantou County to assess the effect of such debris-flow retaining structure and to shrink its size to move to the indoor for a test of debris-flow tank.

For the volume concentration reduction rate, the result of indoor tank test shows that the volume concentration for all cases after passing the dam is reduced to below 03.As the initial volume concentration is 0.45 and 0.55, the volume concentration reduction rate is more than 80%.For the initial volume concentration of 0.35, then the reduction rate is 60.3%.The dam-passing rate will be reduced as increasing the volume concentration, which is less than 40% before the dam reaches the full level. The higher the volume concentration is, then the better the grain deposition rate is. As the volume concentration is 0.65, the grain deposition rate can reach 98.88%. And as the

2

volume concentration is 0.35, the grain deposition rate will be down to 60%. Under the strike of debris-flow again and again, we use the displacement meter and the vibration meter to measure the impact fore of sediments in the auxiliary dam and in front of the dam and the acceleration of sediments in the dam and find that they are significantly reduced. Therefore, through the test, we can find that we can truly make use of the characteristics of a retaining structure to retain & deposit the debris flow. Key WordDebris Flow, Flexible Retaining Structure, Volume Concentration Reduction Rate, Dam-passing Rate, Grain Deposition Rate

2.1

2.2

19922-1

2.3

2-2

(a) (b)(c)(d)(e)

2-1

2-2 (a)(b)

(c)(d)(e)

3

1980 (grid-type sabo dam) 2-3

max/ DL =1.52.0 max/ DL

L Dmax

L L L L

2-3

1989L maxD

(1) pC pC max/ DL

(2) L R (%)

81601.0max/4318.53 DLR (2-1) R

(3)

max

6429.06126.0D

LQQ

w

p (2-2)

pQ

wQ

(4)

(5) max/ DL < 2.0

(1k

k

EE

)50% 1k

E

2.4

(1999)

22

21

21 ImvE (2-3)

m [kg] Mass v [m/s] Velocity I [mkg] Rotation Mass of Inertia [l/s] Rotation Velocity

(Impluse)

tpFav

(2-4) p = t t = Fav =t

3.1

3.1.1

4

8.22

1957 23 5.12 () 3600 960 411 19 334 15 147 1420

071 3-1

3-1

3.1.2

3.2

3-1

3-2

3-1 (kg) 1173.5 (m3) 0.576 (t/m3) 2.037 (t/m3) 1.917 (%) 5.0 (%) 77.6 #200 (%) 4.1

0.1mm (%) 5.3 - NP - NP

3.3

3-3 7.5m 6m() 3m4.5m 50cm 40cm 80cm120cm 1m

5

3-4

3-3

3-4

3.4

96 8 6 8 8 96 8 8 8 98 13 101.5mm 3-5

50m 12m 15m 3-7 4m 8~10 20~30cm14~16 50~60cm 1m

3-5

(96.08.12~96.08.14)

8 14 2/3 ( 2m) 1/4( 40cm) 3-6

3-6(96.08.14)

3-7(96.08.14)

6

8 12 8 13 7 25 19.5cm 8cm

4.1

1980 grid-type sabo dam

max/ DL =1.52.0 max/ DL 124 2"1"0.5" 4-1 #4#4

#40.1mm 5.3 %1991 0.1mm 10 %

0

10

20

30

40

50

60

70

80

90

100

0.010.11101001000

(mm)

(%

)

2"1"0.5"

4-1

4.2

4.2.1

(1) 40 cm 40 cm 600 cm 420 cm#4 0324-2

(2) 130

(3) 320 cm 200 cm 10 cm 4-3

4-2

4-3

7

4.2.2

30cm 5.08cm(2")

15cm 30cm2.54cm(1")

40cm 30cm2.54cm(1")

30cm 2.54cm(1")

4-4

4-5

4.3

4.3.1

4-1

4-1

Test1 0.65 23 1" 3 Test2 0.55 23 2" 3 Test3 0.65 23 2" 3 Test4 0.6 23 1" 3 Test5 0.55 23 1" 3 Test6 0.45 23 1" 4 Test7 0.35 23 1" 4 Test8 0.55 23 0.5" 4 Test9 0.45 23 0.5" 4 Test10 0.35 23 0.5" 4

4.3.2

(1) LVDT

(2)()

(3)( 30)

(4)

(5) 34

(6)

5.1

34 5-1

5.2

11 3 mm

8

5-3

5-1

5-2

5-3

5.3 Rv

Rv Rv

%1000

10 C

CCRV

C0 C1

0

0.20.4

0.60.8

11.2

0 1 2 3 4 5

(%)

0.35 0.5"0.45 0.5"0.55 0.5"

5-4

(Dmax=0.5")

0

0.2

0.4

0.6

0.8

1

1.2

0 1 2 3 4 5

(%)

0.35 1"0.45 1"0.55 1"

5-5

(Dmax=1")

5.4 Rp

V0 V1Rp

%1000

1 VVRP

V0 V1

9

0%5%

10%15%20%25%30%35%40%45%

0.3 0.35 0.4 0.45 0.5 0.55 0.6 0.65 0.7Cv

%

5-6

0.35 40.25% 0.65 1.13% 0.35

5.5

Rs

%100 PTTRS

T P

0.45 90% 0.35 60.0% 5-7 0.45 0.450.35 91.6%~98.9%60%

60%

65%

70%

75%

80%

85%

90%

95%

100%

0.3 0.35 0.4 0.45 0.5 0.55 0.6 0.65 0.7 Cv

%

5-7

5.6

- LVDT

Excel 5-8 6%42% =L1-L2/L

Test 4

-100

1020304050607080

1 1.5 2 2.5 3 3.5 4 4.5(s)

LVDT

(mm)

5-8

5.7

5-95-11 X

10

0.262(cm/s2) 0.054(cm/s2) 0.016 (cm/s2)

Test 3

-1

-0.5

0

0.5

1

0 0.5 1 1.5 2 2.5 3 3.5 4sec

Vlo

t

X

5-9

Test 3

-1

-0.5

0

0.5

1

0 0.5 1 1.5 2 2.5 3 3.5 4sec

Vlot

X

5-10

Test 3

-1

-0.5

0

0.5

1

0 0.5 1 1.5 2 2.5 3 3.5 4sec

Vlot

X

5-11

1.

2..

3. 0.35 40.25% 0.65 1.13% 0.35

4. 0.45 90% 0.35 60.0%

5.

6%~42%

0.262(cm/s2) 0.054(cm/s2)0.016 (cm/s2)

(NSC 95-2622-E-324-009-CC3)

1. - 1851992

2. No.11437-441980

3.

11

No.20B-2 1-311977

4. ()87 1998

5. 452000

6. 1994

7. No.23B-21980

8. ()No.1391993

9. No.74 21-281999

10. 1989

11. 1999

12. Johnson, A.M. and Rodine, J.D., Debris Flow, Slope Instability, John Wiley & Son Ltd., pp. 257-361,1984.

13. Halliday, D. and Resnick, R.,Fumdamentals of physicsJohn Wiley & SonsInc.pp.102~103N.Y., 1970.

14. Timoshenko, S., Strength of Materials, Partl1 Elementary Theory and Problems, D.Van Nostrand Company, Inc.,pp.301~302,N.Y., 1956.