Comparison of in-situ testing methods for monitoring the liquefaction mitigation by vibro-replacement stone columns-Article

Article

Pdf Summary

The study evaluates how seismic dilatometer tests (SDMT), piezocone tests (CPTu), and shear-wave velocity measurements detect liquefaction mitigation from vibro-replacement stone columns at a wastewater treatment plant in Guayaquil, Ecuador. The columns were 15 m long, 0.55 m in diameter, spaced 2 m apart, and installed in a variable, interbedded soil profile.<br /><br />Although the columns extended to 15 m, measurable improvement was concentrated in sand and sandy-silt layers, roughly 3.2–6.6 m deep. In this interval, CPTu indicators changed only modestly: corrected cone resistance increased 6% and estimated relative density about 8%. SDMT indicators showed clearer changes: the horizontal stress index rose about 22%, constrained modulus 42%, and shear-wave velocity 26%. Combined CPTu–SDMT estimates indicated increases of about 65% in the modulus-to-cone-resistance ratio, 98% in overconsolidation ratio, and 16% in the at-rest lateral earth-pressure coefficient. The authors conclude that SDMT and combined parameters were more sensitive to improvement than CPTu alone. Limited deeper improvement was attributed to silt-rich and cohesive interlayers that restrict densification and energy transfer.<br /><br />Liquefaction assessments using CPTu, DMT, combined CPT–DMT, and shear-wave velocity generally indicated reduced vulnerability after treatment. Depending on the method, severity indices and estimated settlements declined, though CPTu-based reductions were generally smaller. Different methods also produced different absolute hazard estimates.<br /><br />The findings support using multiple in-situ methods to monitor ground improvement, particularly in stratified soils where a single test may understate or misrepresent treatment effects. Interpretation should account for lateral soil variability: natural- and treated-soil tests were about 30 m apart, so some profile differences may reflect local conditions rather than improvement alone.

Keywords

seismic dilatometer test

SDMT

piezocone test

CPTu

liquefaction mitigation

vibro-replacement stone columns

shear-wave velocity

ground improvement

wastewater treatment plant

soil stratification