Monitoring ground improvement using in situ tests in Guayaquil, Ecuador

Abstract

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, in order to compare the variation of the geotechnical parameters in the analyzed deposits, also combining DMT and CPTu results in sandy deposits to estimate the overconsolidation ratio (OCR), 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 then 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) approaches for a design ground motion. The results show a certain sensitivity of the DMT over the CPTu tests to the ground improvement into the layer composed by sands and sandy silts, while VS values show a limited increase in the treated area