The present invention relates to a method for forming a barrier or filling with self-foaming phenolic resins, especially in the mining field. Method, characterised in that it consists in mixing two components, namely a foaming resin comprising sodium bicarbonate as foaming (pore-forming) agent and a catalyst containing, in particular, sulphonic acids, in order to produce, even at low temperature, almost instantaneous conversion into foam with very fast expansion, without requiring contiguous and leaktight shuttering to be positioned. <IMAGE>
