Blast-induced liquefaction in silty sands for full-scale testing of ground improvement methods: Insights from a multidisciplinary study

In the engineering geology field increased attention has been posed in recent years to potential liquefaction mitigationinterventionsinsusceptiblesandformations.Insiltysandsthisisamajorchallengebecause,asthe finescontentincreases,vibratorymethodsfordensificationbecomeprogressivelylesseffective.Analternative mitigationtechnique canbetheinstallationofRammedAggregatePier® (RAP)columnsthatcanincrease the resistanceofthesoil,accountingforitslateralstressincreaseandforthestiffnessincreasefromsoilandRAP compositeresponse.Toinvestigatetheinfluenceofthesefactorsonliquefactionresistance,full-scaleblasttests wereperformedatasiltysandsiteinBondeno(Ferrara,Italy)whereliquefactionwasobservedafterthe2012 Emilia-Romagna earthquake. A multidisciplinary team of forty researchers carried out devoted experimental activitiesaimedatbetterunderstandingtheliquefactionprocessatthefieldscaleandtheeffectivenessofthe treatmentusinginter-relatedmethods.Bothnaturalandimprovedareaswereinvestigatedbyin-situtestsand 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 effectivenessduetotheimprovementofsoilpropertieswithintheliquefiablelayerandaconsequentreduction 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

Sintesi della ricerca internazionale su strategie di mitigazione della liquefazione cosismiche di sabbie svolta attraverso la liquefazione indotta da esplosioni in sabbie fluviali quaternarie nell’Avanfossa Appenninica, in un sito in cui la liquefazione naturale si era già manifestata durante i sismi del maggio 2012. Si è operato il confronto fra i fenomeni di liquefazione indotta in sabbie di riempimento di canale fluviale in condizioni naturali e dopo miglioria della risposta cosismica mediante la messa in opera di colonne drenanti.