Engineering for Masonry Dams by William Pitcher Creager

Author:William Pitcher Creager
Language: eng
Format: epub, pdf
Publisher: J. Wiley & sons, inc.; [etc., etc.]
Published: 1917-03-25T05:00:00+00:00

102

SOLID NON-OVERFLOW GRAVITY DAMS [Chap. VI

TABLE XIY—Contintied

The maximum vertical compressive stresses for full reservoir is foimd to be:

, 2X395

|Z00^2-3-^)+937.5 = 12,5()0.

68.

For empty reservoir, Eq. (11a) * applies,

2(TF) = S(Tr)i,=497,300,

2X68.4 ..^ u = —^— = 45.6,

P«"=0.

The maximmn vertical compressive stress for empty reservoir is then fomid to be:

,_.2X497^/3X46^_ \ ^' " 68.4 V 68.4 l;+«-14,550.

For the maximum inclined compressive stresses in the dam, Eqs. (23o) and (236), of Art. 33, apply. Eqs. (24a) and (246) have no practical use imless the strength of the foundation is less than that of the masonry.

At the toe of the dam,

tan </>'=i^=0.752; tatf <t>' =0.566; sec^ <t>' =1.568. lo

At the heel of the dam,

tan</>"=^=0.0412; tan2 </»"=0.0017; sec2</>" = 1.0016. lo

For full reservoir,

tan ^=0.672; sec^ ^ = 1.455.

For empty reservoir,

tan^=0; sec2^ = 1.00.

Using these values in Eq. (23a), the maximimi inclined compressive stress for full reservoir is foimd to be:

p/ = (12,500Xl.568-30X62.5X0.566)

or 30X62.5 or 12,500X1.455, p/ = 18,540 or 1,875 or 18,200, p/ = 18,540, the greatest of these values.

* See foot-note, p. 89.

SOLID NON-OVERFLOW GRAVITY DAMS [Chap. VI

In the same way, from Eq. (236), the maximimi inclined compressive stress for empty reservoir is fomid to be:

p/' = (14,550-0) or 0 or 14,550X1.0016, Pi" = 14,550, the greatest of these values.

40. Comparison of Non-overflow Dams. A companson of high, solid, non-overflow dams is given in Fig. 23. With the exception of the OHve Bridge final section, the designs of these dams were all made in accordance with the same general theory, the differences in areas and shapes being affected solely by the assimip-tions, as indicated in Table XV.

The theoretical section of the Olive Bridge Dam was arbitrarily increased^o its final section, on accoimt of the importance of the structm-e.

TABLE XV

CoMPAKisoN OP Solid, Non-overflow Dams, Showing Assumptions

Used in Design

(See Fig. 23)

Dam.

Olive Bridge, theoretical eection

OUve Bridge, final section

New Croton

Elephant Butte

Wegmann's Practical Profile No. 3... Morrison and Brodie's example of

design

The author's Example No. 1

Unit Wt. of Masonry, in Lbs. per Cu.ft.

145.8 145.8 156.2 140.0 145.8

146.0 145.0

Percentage of Area of Base Subjected to Uplift.

661 661

0 33i

0

0

^

Total Ice

Pressure,

in Lbs.

per Lin.ft.

47,000 47,000

0

0

0

0 40,000

Maximum Allowed Vertical Pressures, in Lbs. per Sq.ft.

Toe.

40,000 12,200 33.400 22,000 16,800

28,000 18,000

Heel.

40.000 23,000 30,800 28,000 20,600

36.000 25,000

The maximum vertical pressures indicated for the Olive Bridge final section probably do not exist, as the maximum section is in a narrow gorge confined on both sides hy good rock, between which the dam is wedged, without the possibility of movement.

In the upper part of the New Croton Dam the vertical pressures were limited to 16,400 and 20,600 lb. at the toe and heel, respectively, and, in the lower part, 33,400 and 30,800. This difference in allowed pressures, in the top and bottom of this dam, has been severely criticised.

COMPARISON OF SECTIC

HIGH SOLID NON-OVERFU

SUPERIMPOSED WITH CC

WATER SURFACES

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