TUNNEL CONSTRUCTION METHOD

PURPOSE:To prevent the substantial consumption increase of mortar and avoid a cost increase by mixing foamed synthetic resin particles with the mortar before forced supply when the mortar is forcibly supplied through the executed portion of a tunnel for back-filling at the outside of a shielding material. CONSTITUTION:A bonding agent of synthetic polymer emulsion type is preliminarily added to water to be kneaded with cement and the like in a mortar mixer 15. Then, after a water solution containing a small amount of a surface active agent is preliminarily deposited on foamed synthetic resin particles, cement is kept in contact with the aforesaid particles and a cement film is deposited and formed on the surface of the particles. As a result, affinity between the foamed synthetic resin particles and the mortar increases and a difference in specific weight thereof decreases, enabling an easy kneading process to be applied. On the other hand, a tank 20 is supplied with the foamed synthetic resin particles from 1 foaming machine 45 via a pump 46. Also, the foaming machine 45 contains a solution of synthetic resin and is capable of manufacturing the foamed synthetic resin particles from the solution whenever necessary.