Advantages And Disadvantages Of Pneumatic Caisson

Pneumatic caisson provides dry working conditions, which is advantageous for soil excavation and concrete-sealing of the caisson bottom. It is also well suited in areas where other underground construction methods might cause adverse effects to adjacent ground structures. Pneumatic Caissons are divided into two types—Traditional Pneumatic Caisson and Modern Pneumatic Caisson, according to different soil excavation methods.

1) Traditional Pneumatic Caisson (Manned Pneumatic Caisson)

Soil excavation work is done by man-operated excavators in the working chamber or by manual labour, under high-compressed air condition through the whole excavation and sinking phase. Under this increasingly high-pressure working condition, operation workers, are exposed to risk of “caisson disease”.

Caisson disease is so named since it appeared in tunnellers when they left the compressed

As mentioned above, Traditional Pneumatic Caisson is relatively economic and it does not need complex automatic unmanned machines, but with air pressure increasing, people are unable to work under such circumstances. MPC cost more than the traditional method but soil excavation can be done successively even when air pressure rises higher than 0.5 MPa. A combination of the two types becomes more economical for deep-sinking caisson construction.

When caisson bottom reaches the underwater level, compressed air is pressed into the working chamber, soil excavation and discharge is still done by manual labor, or by man-operated machines. When the caisson sinks deeper and the air pressure increases higher than 0.2 MPa, the Manned Pneumatic Caisson is transformed to the MPC. Then the MPC will continue until the designed elevation.

4.5.4 Caissons Type