RMPE - Suggest you look into Tomlinson's Design and Construction of Foundations book and any Indian geotechnical text where they will call this type of construction a "well foundation". It is used extensively in India - much more, I think, than in many other parts of the world. If you need references, I can find them for you.
after some thought, it is simply a compression ring and the compressive stress is very small on concrete walls. Tip design is most critical as the cutting shoe must be durable and not shear off and take ring compression as well as ring tension when the plug is made. Then the bouyancy after the caisson is pumped dry must be consdiered before the superstructure is built during the screens installation. Bottom slab is big round plate with large pressure load. An old Foundations of Structures text has old cutting shoe details and some basic info.
RMPE - what old structures text? Just interested in knowing. A personal view is that many engineers don't study the older texts and engineering papers - thinking - the 1950s? 1960s? Come on!!! But, they do come in handy at the right time for the right project! Cheers
