Effects of Soil Properties and Input Motion on Liquefaction Zones in Backfill and Subsoil of Quay Walls

Abstract

The damage caused to port structures, especially quay walls during large earthquakes, is mainly attributed to the extent to which backfill soil reduces to liquid state. The failure of quay walls due to liquefaction of surrounding soil became a major issue in the Niigata earthquake of 1964, Hyogo Ken Nanbu earthquake of 1995, and many other earthquakes world over. Even in India, the Gujarat earthquake of 2001 and Sumatra earthquake of 2004 in Andaman and Nicobar Islands showed liquefaction induced damages to port facilities. Since these damages are catastrophic and can cause huge economic loss, it becomes essential to mitigate against the failure of port facilities during earthquake. Hence, the understanding of mechanism of failure of port facilities such as quay walls due to liquefaction, factors influencing such failure and proposing possible mitigation measures have gained a lot of importance in research. A detailed study on the impact of properties of backfill and subsoil on the zones of liquefaction is conducted using GEOSTUDIO, a finite element software for geotechnical studies. In the present study, Finn and Seed mode (Martin et al. in J Geotech Eng Div ASCE 101:423–438, 1975) [8] employed effective stress-based approach to consider the changes in water pressure causing liquefaction due to earthquake loading. An analytical model of quay wall system consisting backfill, subsoil and quay wall is prepared and analysed in 2D plane strain system. The emphasis is on the location and extent of liquefaction and pressure due to water. The soil properties such as internal friction, unit weight of backfill for both backfill and subsoil and earthquake shaking such as varying amplitudes, frequency, and duration of input acceleration, have a huge impact on the liquefaction zones in the surrounding soil which is focused in the present study. This type of study can enhance the understanding of mechanism of failure of structures due to liquefaction, effects of different properties of ground and shaking on the extent and location of liquefaction and hence can provide a paradigm shift towards performance-based design of geotechnical structures under earthquake effects. This paper concentrates on presenting the extent and location of liquefaction zone in backfill and subsoil during the behaviour of quay walls under dynamic loads.KeywordsLiquefactionBackfill soilSubsoilSeismic performance of quay wallsFinite element studies of geotechnical facilitiesSeismic mitigationPerformance-based design