Question

. A section of an immersed tube tunnel is made up of a pair of hollow steel cylinders,

attached side by side and sealed at each end. Each cylinder is 300 feet long and has a

diameter of 50-feet. If the specific gravity of the hollow cylinders is 0.8, what is the

volume of concrete (SG = 2.4) that is necessary to start sinking the tunnel section into

seawater (SG = 1.03)

Answer 1

l=300 ft

d= 50 ft

Specific gravity of hollow cylinder (SGcyl)=0.8

Specific gravity of concrete(SGcon,)=2.4

Specific gravity of seawater (SGsw,)=1.03

Volume of cylinders is

V=2(3.14*r^2*l)

=2*(3.14*(50/2)^2*300)

=1177500 ft^3

To start sinking, overall specific gravity must be equal to a specific gravity of seawater.

Overall specific gravity is

SG=

1.03=(0.8*1177500+2.4*Vcon)/(1177500)

Vcon=112843ft^3

hence volume of concrete that is necessary to start singing the tunnel section into sea water is112843ft^3.