Fine-grained Sand Behaviorin a Dam Reservoir at the Middle Reaches of a River

Civil Engineering Research Institute of Hokkaido

〇 Tomonori ShimadaYasuharu Watanabe Hiroyasu Yasuda

The Saru River ・ Introduction

Outline

（１） Experiment on soil particle sedimentation　　 Experiment on soil particle entrainment

（２） To produce proposed equation

（３） To confirm the suitability of these equation　　　　→ Reproduction calculation for the flood

Experimental setup

（１）① Soil Particle Sedimentation

） （）＝（ velocityfallObserved×K+KvelocityFall sb

Influence of Water Tank

（１）① Soil Particle Sedimentation

003.1wasKtheofvalueAverage

2S/r=SWhere

.S.J,McNownS006.1+1=KsurfaceSidewall

erimentexpthisin

considertoneednowasThere

15>ifconsider1S/r=SWhere

H,BrennerS89

+1=KsurfaceBottom

s

s

ss

b

bb

） （ ： ・

） （

） （ ： ・

S1

S2S2

Coefficient of resistance to soil particles

（１）① Soil Particle Sedimentation

05.1D

D

Re

18.43=C

2+Re24

=C

Results from the experiment

Reynolds number

Coeffi

cie

nt

of

resis

tan

ce o

f sed

imen

tati

on

Proposed equations for falling velocity of soil

particles

（１）① Soil Particle Sedimentation

sgdsgd

w

velocityfallforequationsproposed

wCdt

dwmgmM

dt

dwM

motionofEquation

f

D

11.1305.1

21

11

)()38.32

1(

8

1-

2

1-)-(

　 　 　

　 　　　　　　

π　 　 　

　 　　　　

sgdsgd

ν36

sgd

ν36

3

2w 3

2

3

2

f

sgdν

sgd

32.38

1w

1.1131.05

f

（１）① Soil Particle SedimentationRubey’s Equation and Presented

EquationFall v

elo

cit

y o

f a s

oil p

art

icle

[c

m/s

]

Soil particle diameter [cm]

Rubey’s equationProposed equation

Experimental Setup

（１）① Soil Particle Entrainment

Experimental Setup

（１）① Soil Particle Entrainment

Volume of Entrainment vs. SS Concentration

Time of water flow [min]

Volu

me o

f En

train

men

t [c

m3] C

on

cen

tratio

n o

f su

sp

en

ded

sed

imen

t in

the w

ate

r [mg

/L]

Volume of EntrainmentSS Concentration

（１）① Soil Particle Entrainment

( )

)wΩu

gdρ

ρραK(=q

Cwqλ-1

1=

tz

f'*s

s*su

bfsu

－－

－－∂

∂

Proposed of the Entrainment Rate Equation

Proposed coefficient K=0.00027Conventional coefficient K=0.008

（１）① Soil Particle Entrainment

Calculation Results of the Reproduction

（ 3 ） To confirm the suitability of these equation

Reservoir bed

Bed

ele

vati

on

[m

]

Before floodSurveyedProposed equationConventional equation

Volu

me o

f sed

imen

t [

thou

san

d m

3]

Surveyed Proposed Conventional Equation Equation

• I explained fine grained sand behavior in a Dam reservoir.

• First, I explained the experiment on soil particle sedimentation, and then the experiment on soil particle entrainment.

• Next, I explained the method used to produce proposed equations.

• Finally, in order to confirm the suitability of these equations, I showed the results of a reproduction calculation.

• In conclusion, it is found that estimating the volume of sedimentation in the dam reservoir is possible through use of the equation.

Conclusion

Check dam

W ater flow

Cross Section of the Dam Before/After Flood (Downstream of the Check Dam)

Grain Size of Soil Particles

Grain size [ cm ]

Clay 0.0000 ～ 0.0005

Silt 0.0005 ～ 0.0075

Fine sand 0.0075 ～ 0.0250

Medium-grain sand

0.0250 ～ 0.0850

Coarse sand 0.0850 ～ 0.2000

Parameters in the entrainment experiment

Case １ Case 2 Case 3

Discharge [m3/s] 0.10 0.20 0.22

Bed slope 1/5000 1/5000 1/400

Water depth [cm] 75 55 21

Duration of water flow [min.]

30 30 30

Discharge and Water Level (Calculated)