http://www.tfl.gov.uk/tfl/press-cent...s-releases-con
tent.asp?prID=428
says they expect to have a full service running on the Circle/H&C
five days after the police have finished their investigations. I
don't think they would say that unless they were confident there had
been no major structural damage.
If the reports today (that the explosive was mostly Acetone Peroxide)
are correct, then it would be unlikely given the damage to the train
that any serious damage was done to the tunnel.
Since the rest of us aren't the explosive experts that you are, David,
perhaps you can explain that remark?