Mud boil

one of the main railway roadbed diseases

has a direct effect on the safe run of trains

because it may cause the decline of roadbed elasticity through softening of bed and hardening of ballast. It is proved practically that chemical grouting can do with it. For evaluating the positive role of the selected super polymer to the soil in roadbed

this paper operates the dynamic triaxial test by simulating the proper ties of soil

the static stress

the cyclic dynamic stress and drainage condition in site. The results show that dynamic strength of the modified soil by super polymer increases in a considerable degree. The dynamic properties also get a conspicuous reformation. Subsequently the positiverole is affirmed in engineering practice.