PURPOSE: Titled adhesive that is prepared by adding a specific acid-decomposition type foaming agent to unsaturated polyester resin and keeps the foaming magnification constant regardless of water content and temperature by completing the decomposition reaction before the curing reaction.

CONSTITUTION: (A) The major material consisting of (a) an unsaturated polyester resin, (b) a curing accelerator such as tertiary amine, (c) an acid and (d) water is combined with (B) a curing agent consisting of (e) an organic peroxide, (f) a filler, and (d) acid-decomposition type foaming agent such as alkali or alkaline earth or ammonium carbonate or bicarbonate with less than 250, preferably less than 150μ particle sizes on application. Preferably the amounts of each component are 100pts.wt. of component a, 0.05W1.0pt. of b, 0.1W10pts. of c, 0.1W10pts. of d and 0.5W5pts. of g.

USE: Reinforcement of soft and weak rock beds in various kinds of tunneling work.