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Problem 7'19

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... basis of arch-rib analysis, design an arch dam 50 m high for a V-shaped canyon. The width of the canyon at its bottom is 10 m and the width at 50 m is 70 m. The ... – PowerPoint PPT presentation

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Title: Problem 7'19


1
Problem 7.19 Estimate the dry specific weight of
a reservoir sediment deposit composed of 35
sand, 28 silt, and 37 clay by weight 10 yr
after deposition. By how much will the porosity
of this deposit change after an additional 15 yr
of consolidation? Assume that the sediment is
always submerged and that the specific gravity of
the sediment particles is 2.65. Use W
(weight of sediment) to calculate porosity change
as a function of time.
2
Specific Weight of Deposited Sediment
W specific wt. (dry) of sediment deposit
(lb/ft3 , kg/m3) T age of deposit (years) B
constants that relate to the compaction
characteristics of the soils Subscripts 1, 2, 3
for sand (1), silt (2), and clay (3), respectively
gt
lt
3
Problem 7.19 Sediment always submerged W1
93 W2 65 W3 30 B1 0 B2 5.7 B3
16.0 Sand 35 Silt 28 Clay 37 W
(sand/100)W1 B1 log T gt (35/100) 93
0 log T (silt/100)W2 B2 log T
gt (28/100) 65 5.7 log T (clay/100)W3
B3 log T gt (37/100) 30 16 log T _at_T
10 yrs W 69.4 lb/ft3 _at_T 25 yrs W 72.4
lb/ft3 Porosity (p) 1 (solids vol. /total
vol.) 1 (W / s.g. ?w) s.g. 2.65 ?w 62.4
lb/ft3 _at_T 10 yrs p 0.58 _at_T 25 yrs p 0.56
4
Problem 8.13 On the basis of arch-rib analysis,
design an arch dam 450 ft high to span a 740 ft
wide U-shaped canyon. Use 500 psi as the
allowable compressive stress in concrete. In
an arch dam, a rib of minimum (most efficient)
volume is found for a central angle of ?
133?34? (in practice the central angles vary b/t
100? to 140?) 2 sin (?/2) 2 cos (90?-
?/2) 2 cos (23?15?) 20.919 B 740 ft ?w
500 psi
5
Problem 8.13
For constant-center, constant-radius, U-shaped
dam At base, t 0.35 450ft 157 ft At
top, t 10 ft constant thickness is
assumed at upper portion of dam
6
Problem 8.14 On the basis of arch-rib analysis,
design an arch dam 50 m high for a V-shaped
canyon. The width of the canyon at its bottom is
10 m and the width at 50 m is 70 m. The maximum
compressive stress in the concrete is 4200 kPa.
Central angle of ? 133?34? 2 sin (?/2) 2
cos (90?- ?/2) 2 cos (23?15?) 20.919 ?w
4200 kPa At h 0, B 10m At h 70, B 50
m As the height increases, so does the r t as
a function of width (B) changes
7
Problem 8.14
8
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9
EXTRA CREDIT ASSIGNMENT (Optional, of course)
Write a report on two (2) different sections of
the UFWTF. In this report you are to complete an
analysis (all five points) of two sections in the
plant similar to what is required in your
semester project. Included in the report
should be a short introduction theoretical
description of the sections you are evaluating
calculation of BOD, reoxygenation and
deoxygenation rates of those sections
conclusions about what your evaluation
uncovered. Individual reports, 7-10 pages
typed No same sections from two members of same
group 25 points added to overall homework
points Due Friday, December 6th class time (No
late assignments taken)
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