Face stability is one of most important factors to excavate safely a shallow tunnel by NATM in a sandy ground under water level. The results of a investigation aimed at evaluating the improvement effect of a sandy ground in tunnel improved by chemical grouting are prsented herein. In this investigation, the permeability test and the triaxial compression test in triaxial cell were used to detemined the permeability and the strength of undisturbed specimens obtained by the block sampling method from the improved sandy ground in tunnel face.
The results showed the followings.
(1) The grouting had sufficiently the effect to improve the strength and the waterproof of the sandy ground under water level.
(2) The laboratory tests of the undisturbed specimen gained by block sampling in this report were useful to evaluate the grouting effect.