During the construction of south anchorage open caisson of Ma’anshan Yangtze-River Bridge

the settlement of the open caisson

the earth pressure under the cross wall

the stress of the bottom steel plate of cross wall were monitored. It is found that the super-large open caisson has the characteristics of both strip footing and block foundation. As large settlement is acceptable for the first lifts

the open caisson settlement control method is more suitable than the soil bearing capacity control method. The earth pressure under the common cross wall is smaller than the division cross wall; and the ultimate bearing capacity of soil under the common cross wall is also smaller. When the limit equilibrium state for soil under the common cross wall is reached

the load added during the following lifts is taken by the division cross wall (or the side wall). The stress in the bottom steel plate of cross wall is determined mainly by the concrete pouring of the very first lift

and it is less affected by other following lifts. The stress of the bottom steel plate of cross wall is smaller at the inner part

and bigger at the outer part. The tensile stress near the open caisson side wall can be reduced remarkably by sound compaction of soil backfilled outside.