Poulos, H.G. (2001b). Methods of Analysis of Piled Raft Foundations. Report to Technical Committee TC 18 on Piled Foundations. International Society on Soil Mechanics and Geotechnical Engineering, 46 p.
In addition to those given by panars, Tomlinson's Foundation Design and Construction has some good discussion. Also, back in the 70s, there was an English engineer (Hooper) that issued quite a lot of papers on the subject in the Proceedings of the Institue of Civil Engineers (ICE). If you can get a hold of these, you will find them quite good. One of Hooper's references is:
Hooper, J.A., "Observations on the behaviour of apiled raft foundation on Lond Clay," Proceedings of the Institution of Civil Engineers, Vo. 55, pages 855-877 (1973).
He probably has a good list of references if I remember the paper correctly. I actually have it stuck in a deep box in Toronto sadly.
Also try:
Cooke, R.W., et al. Some observations on the foundation loading and settlement of amulti-storey building on a piled raft foundation in London Clay, Proc ICE, No. 107(1), pages 433 to 460, (1981).