1. PROJECT 4: REVIEW OF BLAKELY
MOUNTAIN DAM, ARKANSAS
CE 6313: DESIGN OF EARTH DAMS
Group 1
Mohammad Faysal, Yohannes Okubay & Asif Ahmed

2.  Project Description
 Review of Existing Design parameters
 Seepage flow analysis by flow net
 Flow analysis in Plaxis
 Slope stability analysis in Plaxis
 Dam Settlement Analysis
 Construction Plan and compaction methodology
 Dam instrumentation and Monitoring
Outline

3.  Blackly Mountain Dam located in Arkansas
 1200 ft long and 230 ft high earth dam
 Constructed between 1950to 1952
 Purpose of the dam flood control and hydropower
 Drainage area of 1105 sq.mi
 Has two tunnels one for power intake and one for flood
control
Blakely Dam
Project Description

4. Plan and Zonation of Dam

5. Borrow Area
6,687,000 cu yd
>3,800,000 cu yd

6. Review of Existing Design parameters
Soil Type Soil Classification
Impervious (I and II) Salty Clay , Sandy clay (I); clay sand , and clay
silt(II)
Fine random (III and V-a) Sandy silt , silty sand, and sand with more than
5 % finer than No.200 sieve (III); or a
combination of soil types I , II and or III where
individual soil strata are less than about 3 ft.
thick , containing more than 15 % finer than the
no.200 sieve and about 50 % or less gravel (V-
a).
Coarse random (V-b) A material with less than 15% finer than No.200
sieve and about 50% or more gravel.
Pervious (IV) Sand and /or gravel (less than 5% finer than the
no.200 sieve and or free drainage).
Borrow Materials

7. Design shear strength for mix 1, 2 and 3 Design curves for QT, QcT and DS

8. Task 2: Seepage Analysis
Two Methods:
 Flow net
 Impervious Foundation
 Pervious Foundation
 Plax Flow (FEM method using PLAXIS)
 Impervious Foundation
 Pervious Foundation Soil type
Qc Test
ϒm (pcf) ϒsat (pcf)
Permeability, k
(ft/day)
Elastic
Modul
us, E
(psf)
C (psf) ф ( ᵒ ) Kh Kv
Type I & II 700 25 131 135 0.06
6.91E-
03
1.04E+
06
Type III &
Va
700 25 131 135 0.0124
1.38E-
03
2.00E+
05
Type Vb 700 25 131 135
2.77E-
03
2.77E-
03
1.05E+
06
Type IV 0 35 131 135 0.138 0.138
1.05E+
06
Rock 16000 10 169 178 1.38 1.38
2.80E+
08
Gravel-
Sand 0 35 109 121 276.48 276.48
1.46E+
06

9. Task 2: Seepage Analysis
 Flow net
 Impervious Foundation
 Pervious Foundation

10. Task 2: Seepage Analysis
 Plax Flow (FEM method using PLAXIS)
 Impervious Foundation
 Pervious Foundation
Condition
Water
Elev. (ft)
Embankment
seepage,
gpd/ft
(Flownet)
Total Seepage,
gpd (Flow net)
Embankment
seepage,
gpd/ft (Plaxis)
Total
Seepage,
gpd
Steady State 592 0.48 350 3.51 2106
0
0.5
1
1.5
2
2.5
3
3.5
4
FlowVolume(gpd/ft)
Flow Net Plax Flow

11. Task 2: Seepage Analysis
 Plax Flow (FEM method using PLAXIS)
 Pervious Foundation
955
960
965
970
975
980
985
FlowVolume(gpd/ft)
Flow Net Plax Flow
Total Seepage Volume (per foot)
Condition
Water
Elev. (ft)
Total
seepage,
gpd/ft
(Flownet)
Total
Seepage, gpd
(Flow net)
Total
seepage,
gpd/ft
(Plaxis)
Total
Seepage,
gpd
Steady
State
592 965 580000 982 589200

12. Task 3: Stability Analysis (Circular Arc Method)

13. Task 3: Stability Analysis using PLAXIS (After Construction)
After Construction
Water Table at elev. = 380 ft,
F.S. = 1.73
Rapid Draw Down
Water Table at elev. = 610 to 480 ft,
Time Interval = 0.5 day (Assume)
F.S. = 1.19

14. Task 3: Stability Analysis using PLAXIS (After Construction)
Steady State
Water Table at elev. = 592 ft,
F.S. = 1.55
Condition
Water
Elev. (ft)
Critical
Location
FS (Report)
Critical
Slope
Plaxis
FS
(PLAXI
S)
Reqd. F.S.
Remark
s
After
Constructio
n (No
Seepage)
380 D/S 1.79 D/S 1.73 1.25 Stable
Steady State
Seepage
592 D/S 1.77 D/S 1.55 1.5 Stable
Rapid
Drawdown
610 - 480 U/S 1 U/S 1.19 1.00 Stable

15. Task 3: Stability Analysis using PLAXIS (After Construction)
Condition
Water
Elev. (ft)
Critical
Location
FS (Report)
Critical
Slope
Plaxis
FS
(PLAXIS
)
Reqd.
F.S.
Remark
s
After
Constructio
n (No
Seepage)
380 D/S 1.79 D/S 1.73 1.25 Stable
Steady State
Seepage
592 D/S 1.77 D/S 1.55 1.5 Stable
Rapid
Drawdown
610 - 480 U/S 1 U/S 1.19 1.00 Stable
0
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
1.8
2
After Construction (No Seepage) Steady State Seepage Rapid Drawdown
FactorofSafety
Factor of Safety Comparison
Circular Arc Method PLAXIS

16. Uplift Pressure

17. Task 4: Settlement
 Foundation Settlement
 Embankment Settlement

18. Settlement using 1-D analysis
εa= γd(ωc/γ)(1/Ds -1)*100
γd= 116 pcf
ωc= 0.136
e0= 0.428
Gs= 2.65
Ds= 0.842056075
γ 62.4 pcf
εa= 4.742138365 %

19. LayerNo Layer
Thicknes
s (ft)
Unit
Weight of
Soil (pcf)
Average
Stress
(psf)
Average
Stress
(tsf)
Void
Ratio,e
Vertical
Strain
TotalCompressioninLayer
(ft)
TotalCompressionbelow
TopLayer
CompressionofLayer
DuringConstruction
Compressionbelowtop
layerduringconstruction
PostConstruction
CompressionofLayer
Compressionpriorto
reachinglayertop
TotalSettlement
Settlementduring
Construction
PostConstruction
Settlement
1 23 135 1506.5 0.75325 0.402 1.8207283 0.418768 12.11204 0.418768 9.82493 0 9.82493 2.287115 0 2.287115
2 23 135 4611.5 2.30575 0.378 3.5014006 0.805322 11.69328 0.805322 9.406162 0 8.72969 2.963585 0.676471 2.287115
3 23 135 7716.5 3.85825 0.37 4.0616246 0.934174 10.88796 0.934174 8.60084 0 7.63445 3.253501 0.966387 2.287115
4 23 135 10821.5 5.41075 0.36 4.7619048 1.095238 9.953782 1.095238 7.666667 0 6.53922 3.414566 1.127451 2.287115
5 23 135 13926.5 6.96325 0.354 5.1820728 1.191877 8.858543 1.095238 6.571429 0.096639 5.44398 3.414566 1.127451 2.287115
6 23 135 17031.5 8.51575 0.345 5.8123249 1.336835 7.666667 1.095238 5.47619 0.241597 4.34874 3.317927 1.127451 2.190476
7 23 135 20136.5 10.06825 0.339 6.232493 1.433473 6.329832 1.095238 4.380952 0.338235 3.2535 3.076331 1.127451 1.94888
8 23 135 23241.5 11.62075 0.33 6.8627451 1.578431 4.896359 1.095238 3.285714 0.483193 2.15826 2.738095 1.127451 1.610644
9 23 135 26346.5 13.17325 0.327 7.0728291 1.626751 3.317927 1.095238 2.190476 0.531513 1.22409 2.093838 0.966387 1.127451
10 23 135 29451.5 14.72575 0.323 7.3529412 1.691176 1.691176 1.095238 1.095238 0.595938 0.41877 1.272409 0.676471 0.595938
12.11204 9.82493

20. Settlement using Parabolic Equation
 S = (γw/E)(h-y)y
 where,
 S= settlement of a point within the dam
 h= height of dam
 y= amount of fill beneath the point of interest
 E= 1-D secant modulus to a stress level equivalent to the mid height of dam

21. Settlement using Parabolic Equation
Fill Height
beneath point
"y" (ft)
γw
(pcf)
Heigh
t of
Dam,
ft
E50
Settleme
nt, S (ft)
230 131 230 240000 0
207 131 230 240000 2.5987125
184 131 230 240000 4.6199333
161 131 230 240000 6.0636625
138 131 230 240000 6.9299
115 131 230 240000 7.2186458
92 131 230 240000 6.9299
69 131 230 240000 6.0636625
46 131 230 240000 4.6199333
23 131 230 240000 2.5987125
0 131 230 240000 0
E50= 12000/0.05 = 240000 psf
5% strain rate

22. Comparison of Settlement
Method 1-D Analysis
Parabolic
Equation
Estimated
in Design
Phase
Settlement
Plate
Value
9.82 ft 7.21 ft 8 ft 6.5-7 ft

23. Cracking Potential
Cracking Potential
(u/s)
Cracking Potential
(d/s)
H (ft)= 230 230
β= 18.33 21.8
Max Post Construction
Settlement (ft) =
2.287 2.287
Cracking Potential=
Max Post Cons
Settlement/Hcotβ
Max Post Cons
Settlement/Hcotβ
=0.003294268 =0.003977108
Emery, 2011

24. Camber Design
Dam
Statio
n
Embankment
Height
1
Percent
of
Height
Post construction
Foundation
Settlement
Cambe
r (ft)
0 0 0 0 0
1 47.33333333 0.47333 0 0.5
2 94.66666667 0.94667 0 1
3 142 1.42 0 1.5
4 189.3333333 1.89333 0 2
5 230 2.3 0 2.5
6 180.3 1.803 0 2
7 135.3 1.353 0 1.5
8 90.2 0.902 0 1
9 45.1 0.451 0 0.5
10 0 0 0 0

25. Task 5: Compaction (Test Fill)
 Standard Proctor Test
 Modified Proctor
New Waddell Dam, Arizona

26. Dam Section

27. Description of Test Fill
Type of
Soil
Type II, Type III
Roller
Weight
2800 lb/ft
Tamping
Feet Area
7 sq Inch, 14 sq inch
Pressure
Intensity
600 psi, 300 psi
Number
of Passes
6,12,24
Moisture
Content
2% wet, 2% dry of
optimum
Section
Lift
Five 6 inch lift

28. Result of Type II Soil
121
122
118
121.5

29. Result of Type II Soil
12.5%

30. Result of Type II Soil

31. Result of Type III Soil
121 121
119
120

32. Result of Type III Soil
11%

33. Result of Type III Soil

34. 300 psi over 600 psi

35. Summary
 300 psi roller produced about 2 to 4 pcf greater density than the 600 psi roller
 Little gain in density beyond 6-8 passes
 300 psi, 6 passes, 6 inch lift, 1.5% dry to 1.5% wet of the optimum

36. Roller

37. Roller

38. Roller

39. Roller

40. Roller
Name Suitability Pressure
Sheepsfoot Fine grained soil 150-400 psi
Ruuber tire Coarse grained soil 60-80 psi
Smooth wheel roller Subgrade, fine grained soil High Pressure
Vibrating roller Coarse grained soil -
Sheepsfoot Roller, 60 inch dia, 14 sq inch tamping foot

41. Summary of Compaction
Zone
Compacte
d Layer
Thickness
Compaction
Equipment
Foot pressure
used (psi)
Number of
Passes
Fine
Material
6 Sheepsfoot Roller 300 6
Relatively
Pervious
Zone
12 Crawler Tractor 6-1/2 3
Filter
Blanket
18 Crawler Tractor 6-1/2 3

42.  The purpose of instrumentation and monitoring is to maintain and improve
dam safety by providing information to evaluate dam performance (as
expected) and warn of changes that could endanger the safety of a dam.
Common causes of earth dam failures are
Task 6: Dam Instrumentation

44.  Overtopping
 Seepage and Piping
 Uplift failure
 Deformation
 Settlement
Common causes of earth dam failures

45.  6 foundation 33 embankment piezometers
 1 Settlement measuring apparatus ( consolidation )
 3 Nos. 12- in out let drains to measure seepage
 Observation wells
 Rubber ball method
Evaluation of existing instrumentation of Blackly Dam
The existing instruments in the dam are working perfectly

46. Piezometer Data

47.  Perfect performance of the dam according to its design for nearly 63
years for seepage , Slope stability and consolidation are with in the
design limit
 Since the installed instruments are performing well , they need to be
maintained properly
 With availability of technology its recommended to automate the data
acquisition process to reflect the real time scenario
Proposed Instrumentation

48. Resistivity Imaging
56 Electrodes: 56*20 = 1120 ft (1120*0.2 = 224 ft)
40 ft
1200ft
H = 230 ft

49. THANK YOU