Foam forming compositions comprising a particulate inorganic material

1. An aqueous composition for forming a foam, the composition comprising a surfactant and a particulate inorganic material,

wherein the surfactant absorbs onto the particulate inorganic material;

wherein the particulate inorganic material is talc or a combination of talc and a particulate inorganic material selected from the group consisting of perlite, bentonite, wollastonite, an alkaline earth metal carbonate or sulphate, calcium carbonate, natural calcium carbonate, and/or precipitated calcium carbonate, magnesium carbonate, dolomite, gypsum, an aluminosilicate, kaolin, mica, diatomaceous earth, vermiculite, pumice, magnesium hydroxide, aluminium trihydrate, zinc oxide, and combinations thereof; and

wherein the weight ratio of particulate inorganic powder to surfactant is in the range of 500:1 to 1:1.

2. An aqueous composition according to claim 1 , wherein the surfactant comprises one or more anionic surfactants, or one or more cationic surfactants, or one or more amphoteric surfactants, or one or more non-ionic surfactants, one or more fatty acid amines, or any combination thereof.

3. An aqueous composition according to claim 2 , wherein the surfactant comprises a sodium salt of an ethoxylated C 12 to C 14 -alcohol sulphate.

4. An aqueous composition according to claim 2 , wherein the surfactant comprises an alkyl trimethyl ammonium halide, tetradecyl trimethyl ammonium bromide, dicocodimethylammonium chloride, dihydrogenated tallowoylethyl hydroxyethylmonium methosulfate, or a polymeric quaternary ammonium ester.

5. An aqueous composition according to claim 1 , wherein the talc comprises microcrystalline talc, macrocrystalline talc, microlamellar talc, or a mixture thereof.

6. An aqueous composition according to claim 1 , wherein the talc is a microcrystalline talc having a d 50 of 10 μm or lower.

7. An aqueous composition according to claim 1 , wherein the ratio of surfactant to water is in the range of 0.05 to 5 wt. %.

8. An aqueous composition according to claim 1 , wherein a ratio of particulate inorganic powder to water is in the range of 1 to 60 wt. %.

9. An aqueous composition according to claim 1 , wherein a weight ratio of particulate inorganic powder to surfactant is in the range of from 500:1 to 1:1.

10. An aqueous composition according to claim 1 , wherein the particulate inorganic material is perlite or a mixture of perlite and talc.

11. An aqueous composition according to claim 1 , wherein the composition further comprises a contaminant.

12. A method of preparing an aqueous composition according to claim 1 , comprising the steps of

providing a surfactant;

providing a particulate inorganic material; and

providing water; and

mixing the provided components in any order.

13. An aqueous composition according to claim 1 , wherein the composition comprises 5 wt.-% water or less.

14. An aqueous composition according to claim 13 , wherein the particulate inorganic material is talc and the surfactant is a cationic surfactant, tetradecyl trimethyl ammonium bromide, or dicocodimethylammonium chloride.

15. An aqueous composition according to claim 3 , wherein sodium salt of an ethoxylated C 12 to C 14 -alcohol sulphate is sodium lauryl ether sulphate.

16. An aqueous composition according to claim 11 , wherein the contaminant is a clay.

17. A method comprising:

preparing an aqueous composition comprising a surfactant and a particulate inorganic material, wherein the surfactant absorbs onto the particulate inorganic material;

using the aqueous composition to prepare a foam; and

applying the foam during tunnel excavation

wherein the surfactant absorbs onto the particulate inorganic material;

wherein the particulate inorganic material is talc or a combination of talc and a particulate inorganic material selected from the group consisting of perlite, bentonite, wollastonite, an alkaline earth metal carbonate or sulphate, calcium carbonate, natural calcium carbonate, and/or precipitated calcium carbonate, magnesium carbonate, dolomite, gypsum, an aluminosilicate, kaolin, mica, diatomaceous earth, vermiculite, pumice, magnesium hydroxide, aluminium trihydrate, zinc oxide, and combinations thereof; and

wherein the weight ratio of particulate inorganic powder to surfactant is in the range of 500:1 to 1:1.

18. The method of claim 17 , wherein applying the foam during tunnel excavation prevents the clogging of a wide boring apparatus by excavated spoil.

19. A method of stabilizing an aqueous foam, comprising the steps of

providing a surfactant,

providing a particulate inorganic material,

providing one or more soil conditioning polymers, viscosity increasing polymers, anti-settling agents, and

mixing the components into an aqueous foam,

wherein the surfactant absorbs onto the particulate inorganic material;

wherein the particulate inorganic material is talc or a combination of talc and a particulate inorganic material selected from the group consisting of perlite, bentonite, wollastonite, an alkaline earth metal carbonate or sulphate, calcium carbonate, natural calcium carbonate, and/or precipitated calcium carbonate, magnesium carbonate, dolomite, gypsum, an aluminosilicate, kaolin, mica, diatomaceous earth, vermiculite, pumice, magnesium hydroxide, aluminium trihydrate, zinc oxide, and combinations thereof; and

wherein the weight ratio of particulate inorganic powder to surfactant is in the range of 500:1 to 1:1.