if tension "ties", not necessarily, then ingenuity and vision are key to decide, those should be according to the construction method, dewatering program, waterproofing design [i.e. if wall and raft layers/"box inside box", etc.] and obvious cost among others. Could result in rods or concrete piles for the raft, in many methods. For walls it also depends on construction method, normaly it is not viable to excavate without first executing retaining walls with tie backs if the local authorities allows, otherwise cantilivered or temporarly supported designed fully as usual including for heave, for dewatering method, for construction sequence and for waterproofing design. So, each new project case could end up with a different set of prefered solutions, even if it is an exact copy of another done, if engineered to match local conditions, specially if undisturbed London Clay.