TUNNEL BORING METHOD USING MUD WATER

摘要

PROBLEM TO BE SOLVED: To perform a tunnel boring work while economically and surely preventing the quality deterioration of mud water even in a clay-containing excavation ground by adding an unsaturated carboxylic polymer salt in combination with sodium carbonate. SOLUTION: This boring method contains a mud water management process to mix excavation mud water with (A) an unsaturated carboxylic acid polymer salt having a polymerization degree of <=500 in combination with (B) sodium carbonate at weight ratio (A:B) of 1:(0.5-15) in terms of pure component and keep the concentration of the component A (in terms of pure component) in the mud water to 100-5,000ppm. Preferably, the method also contains a step to separate and remove fine soil particles mixed into the mud water by centrifugal separator and a step to recycle the mud water after the separation of the fine soil particles. The component A is preferably sodium polyacrylate or a sodium salt of a copolymer of acrylic acid and sulfonic acid.