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

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This paper describes the use of the seismic dilatometer test (SDMT) and the piezocone test (CPTu), to assess the effects of ground improvement in preventing liquefaction damage at a wastewater treatment plant in Guayaquil, Ecuador. The ground improvement consisted of 15 m-long, 0.55 m-diameter and 2 m-spacing stone columns built with vibro-replacement technique. The tests were carried out both in natural and in treated soils to compare the variation of the geotechnical parameters in the analyzed deposits, combining DMT and CPTu results in sandy deposits and estimate the overconsolidation ratio (OCR). The study also considered the at-rest lateral earth pressure coefficient (K0) and the ratio between the constrained modulus and the corrected cone resistance (M/qt). Due to the presence of liquefiable soils at the trial site, the test results were used to evaluate the pre and post-treatment liquefaction severity indexes using different methods based on CPT, DMT, combined CPT-DMT, and shear wave velocity (VS) approach for a design ground motion. The results show specific sensitivity of the DMT over the CPTu tests to the ground improvement into the layer composed of sands and sandy silts, while VS values show a limited increase in the treated area.

Keywords:ground improvement, liquefaction, in situ testing

D. Falquez, F. Ripalda Zenck, D. Besenzon, R. Luque Nuques, F. Illingworth, F. Molina-Gómez S. Amoroso

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