DESIGN OF REACTANGULAR UNDER GROUND WATER TANKTank size 10.00 x 4.00 x m

Tank capacity 120 cum mm

Angle of repose 30 Degree = 17.00 kN/m3

Conrete M 20 = #### N/m3

Steel fy 415 N/mm2

Tensile stess = 150 N/mm2

scbc 7 N/mm2

m = 13

Nominal cover 35 mm = 9.81 N/mm3

1 Solution, general:- There are four components of design.

(I) Design of long wall (II) Design of short wall

(III) Design of roof slab (IV) Design of base slab

The design of walls will be done under two condition.

(a) Tank full with water, with no earth fill out side.

(b) Tank empty, with full earth pressure due to saturated earth fill.

2 Design Constants:- For HYSD Bars = 20

sst = 150 N/mm2

= N/mm2

scbc = 7 N/mm2

m = 13

j=1-k/3 = =

R=1/2xc x j x k = =

3 Design of Long wall :-

(a) Tank empty with pressure satureted soil from outside.

Pa = KaY'H +YwH

1 - sin 30

1 + sin 30

Cutailment of reinfocrement. Since B.M. is proportional to h3, we have:

Asth h3 Asth

1/3

Ast H3 Ast

Direct compression in long walls:- The earth pressure acting on short walls will cause compression

in long walls, because top portion of shorts walls act as slab supported on long walls

At h = 3.00 / 4 = 0.75 or 1.00 m above the base of walls .

=

This direct compression devloped on long walls and wall section.

This will be well taken by distribution steel and wall section

unit wt. of water

Cocrete M

wt. of concrete 25000

3.00

120000

Saturated soil unit wt

unit weight

Here, Ka = =

k=m*c

=

x

0.333

0.378m*c+sst

0.874

1.155

The base slab will be designed for uplift pressure and the hole tank is to be tasted against floatation. As the

L/B ratio is greater than 2 the long wall will be designed as cantilever. The bottom one metre ( >H /4) of short

walls will be designed as cantilever while the top portion will designed as slab supported by long walls .

Pa=KaY' (H-h) + Yw (H-h)

PLC =Pa.x B/2

= = From which h = H

H B

Q=DISCHRAGE IN CUMEC

MANNING'S COEFF FOR CONCRETE N=0.014

V=VELOCITY IN M/S

A=AREA OF CROSS SECTION OF DRAIN

P=PERIMETER OF DRAIN=2D+B

R=A/P

S=LONGITUDINAL SLOPE, GENERALLY 1IN 500 TO 1IN 750

Drain

dia Area(sq.cm)Spacing Perimeter No wt/m L

10 0.7854 200 c/s 3.5 6 21 0.6165 12.947

8 0.5027 200 L 1 19 19 0.3946 7.4971

8 0.5027 200 L 1 19 19 0.3946 7.4971

2

1

3

21

SRN

AQ =

10 0.7854 250 c/s 3.5 5 17.5 0.6165 10.789

38.731 kgs

Cover Slab Total Weight= 3600 X 38.73= 139.43 MT

dia Area(sq.cm)

8 0.5027 200 c/s 1 6 6 0.3946 2.3675

8 0.5027 200 L 1 6 6 0.3946 2.3675

8 0.5027 200 c/s 1 6 6 0.3946 2.3675

8 0.5027 200 L 1 6 6 0.3946 2.3675

9.47

Total Weight= 3600 X 9.47= 34.092 MT

Total quantity of steel=Dtrain+Cover Slab= 173.52 MT