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García Martínez, Maria F
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- PublicationOpen AccessBlast-induced liquefaction in silty sands for full-scale testing of ground improvement methods: Insights from a multidisciplinary study(2020)
; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; In the engineering geology field increased attention has been posed in recent years to potential liquefaction mitigation interventions in susceptible sand formations. In silty sands this is a major challenge because, as the fines content increases, vibratory methods for densification become progressively less effective. An alternative mitigation technique can be the installation of Rammed Aggregate Pier® (RAP) columns that can increase the resistance of the soil, accounting for its lateral stress increase and for the stiffness increase from soil and RAP composite response. To investigate the influence of these factors on liquefaction resistance, full-scale blast tests were performed at a silty sand site in Bondeno (Ferrara, Italy) where liquefaction was observed after the 2012 Emilia-Romagna earthquake. A multidisciplinary team of forty researchers carried out devoted experimental activities aimed at better understanding the liquefaction process at the field scale and the effectiveness of the treatment using inter-related methods. Both natural and improved areas were investigated by in-situ tests and later subjected to controlled blasting. The blast tests were monitored with geotechnical and geophysical instrumentation, topographical surveying and geological analyses on the sand boils. Results showed the RAP effectiveness due to the improvement of soil properties within the liquefiable layer and a consequent reduction of the blast-induced liquefaction settlements, likely due to soil densification and increased lateral stress. The applied multidisciplinary approach adopted for the study allowed better understanding of the mechanism involved in the liquefaction mitigation intervention and provided a better overall evaluation of mitigation effectiveness2131 40 - PublicationRestrictedComparative Study of CPTU and SDMT in Liquefaction-Prone Silty Sands with Ground Improvement(2022)
; ; ; ; ; ; ; ; ; ; ; ; ; ; ;; ;Following the 2012 Emilia-Romagna seismic sequence, widespread liquefaction of silty sands was observed, providing the opportunity to enhance our knowledge of the influence of fines content on seismic hazard and mitigation works. This paper presents the results of a thorough geotechnical investigation performed in connection with full-scale controlled blast tests in Bondeno, Italy, a small village that suffered liquefaction in 2012. Piezocone (CPTU) and seismic dilatometer (SDMT) tests were performed in natural and improved soils after rammed aggregate pier (RAP) treatment to a depth of 9.5 m to provide accurate soil characterization, evaluate liquefaction, and verify the effectiveness of the ground improvement. The combined use of piezocone (CPTU) and flat dilatometer (DMT) data provided reliable estimates of the overconsolidation ratio and at-rest earth pressure coefficient and highlighted the soil improvement in silty sands between 4 and 9 m in depth. Shear-wave velocity measurements showed a low sensitivity to RAP installation. The treatment effectiveness was also confirmed by the use of the simplified procedures for liquefaction assessment, underlining the important influence of the adopted fines profile and by the blast-induced liquefaction. CPTU and DMT parameters remained approximately unchanged between the piers after the detonation.141 77