Abstract
Soft soils are often improved through a grouting technique that injects grout at multiple ground locations. Soils surrounding the injected areas are displaced and compressed. The subsequent consolidation provides additional reinforcement. The overall soil stiffness is hence improved. Although various methods have been traditionally used to evaluate the improvement of the soil stiffness, for example, SPT, CPT, and pressuremeter test, they all provide local results highly dependent on test location. The seismic surface-wave (MASW) method can provide a macro-scale assessment of grouting effectiveness. Multiple MASW surveys were conducted over an area near Navegantes, Santa Catarina, Brazil, where the Federal highway was being duplicated and soft soils existing in the region were being improved by a grouting technique. The survey results showed that, compared to the virgin soil, the shear-wave velocity (Vs) increase at grouting depths (2-8 meters below ground surface) is up to 200 m/sec, which corresponds to approximately 80 MPa and 240 MPa in shear modulus and Young's modulus, respectively. Key data acquisition and processing steps included the active-passive survey and data analysis using a special algorithm.