ABSTRACT: Cement-based grouting technique is normally applied to the crown area of the shallow tunnel so that the instant reinforcement and the long-term stability of a tunnel are assured. However, the assessment of the reinforcement effect has not been fully understood so far and engineering rules-of-thumb are still used in some cases. In this paper, two seismic test methods are performed in the construction field to investigate the soil reinforcement; specifically, Crosshole test and Spectral-Analysis-of-Surface-Waves (SASW) test are used to gain information on the tunnel site before and after the grouting injection.
As a result, it is found that the shear moduli of the injection area are increased up to 20%. Also, investigated in this paper is the numerical analysis scheme to quantify the reinforcement effect. For this, a permeation grouting theory is assumed and the joint stiffnesses of the rock masses are selected as the main parameters to be determined. The so called back analysis shows that, after grouting, the stiffnesses of the filled joint are increased up to 6 times compared with those of the fresh joint.
