Embankments Damaged in the Magnitude M_w 6.4 Petrinja Earthquake and Remediation

Abstract

The main shock of the Petrinja earthquake occurred on 29 December 2020 with a magnitude Mw = 6.4. The earthquake and the aftershocks caused most of their damage in the alluvial plains of the rivers Kupa and Sava, where liquefaction occurred in the loose layers of sands and silty sands. Maybe most important was the damage to some of the embankments built in the mid-20th century to protect the area from floods. Longitudinal cracks along the embankments, in some places transverse cracks, followed by settlement, with some sandy ejecta near the embankments, were obvious consequences of liquefaction in the lower layers, and lateral spreading. The presence of the sandy layers at a depth of 6 to 8 m was known from previous investigations performed in order to improve the flood protection system. Representatives of the Croatian Waters Authorities (Hrvatske vode) who own, manage, and maintain the embankments, inspected all the embankments and, in the first days after the earthquake, carried out the necessary emergency repairs or built temporary secondary embankments. Soon after, the necessary investigation and design of the remediation began. In 2022, construction got underway. This paper gives an overview of the damage, an interpretation of the failure mechanisms, the rationale for the reconstruction methods and the solutions, together with a short overview of the liquefaction analysis performed.

Keywords

• embankment
• earthquake
• liquefaction
• analysis
• remediation