Interaction of piled foundation with a rupturing normal fault

Abstract

Post-seismic observations in the 1999 Kocaeli earthquake in Turkey have indicated that piled foundations may be less suitable than stiff mat foundations in defending a structure against a major normal fault rupturing underneath. This paper explores the interplay of such a rupture, as it propagates in a moderately dense sand stratum, with an embedded two by four pile foundation (typical of common highway overpass bridges). An experimentally validated numerical scheme and constitutive law for sand are utilised in the analysis, with due attention to realistically modelling the non-linear pile–soil interface and the structural inelasticity of the piles. Parametric results identify and elucidate the development of different rupture mechanisms as a function of the exact location of the group relative to the fault and of the magnitude of the tectonic displacement (the fault offset). It is shown that even for a moderate fault offset (less than 0·5 m), lightly reinforced piles will fail structurally, while also forcing the pile cap and the bridge pier on top to undergo substantial rotation and displacement. Even heavy reinforcement might not prevent potentially disastrous displacements. Pile inelasticity is unavoidable and should be acceptable as part of a ductility-based design. However, despite the possible survival of the piles themselves, letting them reach the limit of their ductility capacity may lead to large cap rotation and displacements, which are likely to impose severe demands on the superstructure. Piled foundations may indeed be inferior to rigid raft foundations in protecting a structure straddling an active seismic fault, but with few notable exceptions.

Nonlinear Lateral Response of RC Pile in Sand: Centrifuge and Numerical Modeling

“…Following the hybrid approach outlined in Anastasopoulos et al (2013), the pile was modelled with linear beam elements, circumscribed by "dummy" hexahedral brick elements.…”

“…The design of piles against lateral loading is crucial for loads induced by wind, waves, and earthquakes (e.g., Bhattacharya et al 2011;Anastasopoulos et al 2013). It is a complex problem as it involves small-strain soil nonlinearity, and also large-strain (post-peak) strain softening in the case of dense (and hence dilative) sand.…”

“…Figure 3. 3D finite element model: (a) mesh and boundary conditions; and (b) "hybrid" pile modelling(Anastasopoulos et al 2013). All dimensions in m (prototype scale)Figure 4.…”

Centrifuge modeling of normal faulting and underground tunnel in sandy soil deposit

“…Johansson & Konagai, 2004, 2007Bransby et al, 2008a, b;Ahmed & Bransby, 2009;Loli et al, 2012;Rasouli & Fatahi, 2019;Agalianos et al 2020;Tsatsis et al, 2019) along with numerical modeling tests (e.g. Yilmaz & Paolucci, 2007;Lin et al, 2007;Anastasopoulos et al, 2007;Loukidis et al, 2009;Baziar et al, 2012;Anastasopoulos et al, 2013;Oettle & Bray, 2013;Lee et al, 2012;Baziar et al, 2015;Tsai et al, 2015;Mortazavi Zanjani & Soroush, 2019;Thebian et al, 2018;Ghadimi Chermahini & Tahghighi, 2019). General findings include the realization that both normal and reverse fault propagations through soil is a progressive event, and the final surface emergence of the fault rupture is dependent on soil layer depth, soil properties, dip angle and fault mode.…”

Αριθμητική Ανάλυση Απόκρισης Επιχώματος Οδοποιίας Από Διάρρηξη Υποκείμενου Ενεργού Ρήγματος

“…ΑΔΕΘΑ). Για τον σκοπό αυτό, μεταξύ άλλων πραγματοποίησαν μελέτες για επιφανειακές θεμελιώσεις(Anastasopoulos and Gazetas 2007c;Anastasopoulos et al 2009;Gazetas et al 2007;Gazetas et al 2008;Αναστασόπουλος 2005), για βαθιές θεμελιώσεις με πασσάλους(Anastasopoulos and Gazetas 2007c;Anastasopoulos et al 2013;Gazetas et al 2007;Gazetas et al 2008) και εγκιβωτισμένες θεμελιώσεις κιβωτοειδούς διατομής(Gazetas et al 2007;Loli and Anastasopoulos 2011;Loli et al 2011a;Loli et al 2012;Loli et al 2011b). Όπως και για την περίπτωση του ελεύθερου πεδίου, ο έλεγχος της αξιοπιστίας του προσομοιώματος μέσω δεδομένων από δοκιμές φυγοκέντρισης προηγήθηκε των αναλύσεων.Τα αποτελέσματα των αναλύσεων επαλήθευσαν το συμπεράσματα που προέκυψε από παρατηρήσεις πεδίου με βάση το οποίο θεμελιώσεις/κατασκευές που εδράζονται πάνω ή κοντά σε ενεργά ρήγματα μπορούν να σχεδιαστούν έτσι ώστε να αντέχουν σε τεκτονικές διαρρήξεις.…”