Road, train or sea travel is supposed to be handled exactly in the same way than air travel, with a border check when entering the Schengen area. As an Indian citizen, you will therefore need to have a Schengen visa and to have your passport stamped. In any case, finding a way into the area (say over some mountain road, with a private craft, or something) does not exempt you from any of the legal requirements to enter it.
In the case of Eurostar, there is in fact a full airport-like check before boarding the train, see Train passport control from London to ParisTrain passport control from London to Paris
