To overcome increased skin friction and loss of weight due to buoyancy when well is sunk deeper, additional load known as kentledge is applied on well.

In order to assist sinking process, air pressure may be reduced for a short while. Sometimes explosive may be employed in this case, it is essential to make arrangements for immediate removal of fall fumes.

The cutting edge should have as sharp an angle of 30° practicable for knifing into soil without making it too weak to resist various stresses induced.

The method of construction of pneumatic caisson is similar to that for open caissons (well) except that working chamber is kept air tight.

The disadvantage of a circular well is that in direction parallel to span of bridge, diameter of well is much more than minimum size required.

Open caissons (?caisson? a French word) are called as wells.

Frictional resistance depends on roughness of surface of contact. For example, a smoothly plastered well steining surface is said to reduce frictional resistance.

In order to prevent leakage of air, arrangement of double gates is provided. The person enters first gate, where pressure is atmospheric.

As perimeter of circle is equidistant at all points from center of dredge hole, sinking is more uniform than or shapes.

The bottom-plug is made in bowl-shaped so as to have inverted arch actions.