These are some of the SHC 410 handwritten notes I made during my time at the University of Pretoria. These notes cover examples, explanations and additional research. They are written on either the given lecture slides or in a separate notebook.
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t } Gravity force in
pgtthxsinco flow direction
)
I #
← .
To×P×L } Shear force
↳ Perimeter
To
%
xPL=pgAL×sinco )
since sinlojretancofs .
} Shallow slope
To=pgA#
P
To=pgRSo
↳
boundry stress
mean .
, Forcesonpartickso
-
#
£§€Ecaag#
-
a-
-
to
00800000
* shear force on bed W' (Ps p)
xgxvs ( weight)
= -
force
* on a
grain .
Unit area :
Ap Areaotpartice
=
nr of particles a. Ape
Total area D 502
To A FD xttp D 50 size of
passing
ooo : 50%
D 502
* Point where a particle is about to move :
Cf angle of repose
-
To =
Tcr
* if To > Ter -
unstable
To shear force particles will move
by water &
-
.
Ten -
force required to move the particle .
xDf
'
Tcr A
Cps pg xtanc
-
x
Volume
Tcr_ A ( Q)
( ps ptg xD
- Itxgttpxtan
, Incipent hreshd lmotiono .co 400
To =p
xgxRx5←{ When Rett 7400 →
TCR =
0,056 x (Ps p
-
)gxD5O
↳ Flow is turbulent around the bed
material fully
.
Read value from
When Re* L 400 →
graph
↳ Tcr x (Ps
Pg xD 50
-
number ← Re* 1,14×10-6 Mls
U*yD5o_
2
Reynolds
=
V
=
,
t
kinematic
viscosity .
& U*
=p# Density of the fluid
f p
-
.
Shear
velocity
:{
HRS valid
Dso is
only when D= 1,65
=Ps
=
IEEE ↳
*
assumptions .
z¥
, falllsettlingjveloc.it# submerged
of sediment
gelatine density
diapmeter
Fallingeocity LIFE
f- ilgbd and D=
lPs#
Constant & function of CD
Assume - Sf for
t
=L and CD -2
large D
form factor and CD -
24
REI
Consider a
falling particle :
( Ps p
)xgxt=LzCDxPxAxVFs2
-
ps-plxgxtTDT3-ICDxpxltgdxUFSZVFSZ-kxbgxf.DE
(
)
thus
VFs=y/¥×tg×d
VF5-AxilgxdxD.AT/IzxITFallVelocity:-
given
Rough VFs=T/2zgD⑦
a) sediment - CD -2
b) Fine sediment →
6=24*2
yr-s-yftfxrffxg.AT
& Re*=VFSxD
T
:tFs=gy
o
, Scourestimationo
→
Complexities:
* Non
Homogeneous mixtures of water a sediment
-
* 3D flow patterns
*
Difficulty establishing actual geometries .
actual scour depths
*
Observing
*
Highly variable properties .
long term t short term @ Piers & abutments
enteral
^
p
Total scour =
EG t contraction + Local scour
Alluvial channel scour →
Cohesive bed channel scour →
Scouring : As
ooo
a
Velocity
river scours the
decreases
depth
→
increases
scour potential increases
Scourcountermeasureso
① Hydraulic countermeasures
River Berms
↳
training
↳ Bed armour
structures →
Spurs ,
Dykes ,
ing →
Riprap Gabi ons
,
ing
↳ Local scour armour →
② Structural →
Foundations
③
During maintenance →
{ EROSION If Hydraulic
Fwriaggestation }
:
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