engleski

The effect of suction on differential weathering and stability of soft rock cliffs on the example of Zenta Bay cliff (Split, Croatia)

The coastline of the Split area (Croatia) is characterized by soft rock cliffs formed in Eocene flysch deposits where the dominant soft rock lithotype is marl. Stratification of the flysch formations results in differential weathering between the layers of hard clays/soft rocks and hard rocks, causing undercutting of the hard rocks and ultimately leading to slope instabilities and rockfalls. Furthermore, physical weathering is usually caused by the process of wetting and drying and it can be assumed that this process is highly related to the development of suction in the pores. In this paper the problem of differential weathering and cliff instability is observed on the example of 14-meter-high steep slope of Zenta Bay cliff, located on the southern coast of the Split peninsula. Global stability control of the slope has shown that the slope is quasi stable and does not comply to Eurocode 7 requirements. Based on the two rockfall events in April and November 2019, where heavy rainfall after long dry periods caused slope movements, suction differential was analysed as the instability trigger and weathering agent for soft rock cliffs and slopes. The analysis conducted shows that changes in suction for different annual and monthly periods are significant considering the retention curves for marl, and monitoring weather conditions and trends, with emphasis on relative humidity and temperature changes prior to the rainfall occurrence and the associated suction changes, may contribute to the understanding of rockfall triggering mechanisms and the prediction of rockfall events.

Weathering ; Stability ; Soft rocks ; Cliffs ; Suction

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