Paper contribution

Rockfall triggering mechanisms in soft rocks - climatic factors and suction changes effects

Natasa Stambuk Cvitanovic; Ana Duhovic

Proceedings
EUROCK 2026
Pages
1133-1138
Submitted
28 January 2026
Accepted
15 June 2026
Published
12 August 2026

Summary

Abstract

Wetting and drying cycles controlled by atmospheric changes, which result in transitions between saturated and unsaturated states and strong changes in suction, are one of the main reasons for weathering and degradation in soft rocks. Split area (Croatia) is characterized by coastline cliffs in Eocene flysch formations, where the recession of soft rock cliffs is caused by the weathering. Differential weathering between the layers of marly materials and hard rocks causes undercutting of hard rocks, which together with other geological, marine erosion and climatic factors leads to slope instabilities. Two rockfalls occurred in 2019 at the location of Zenta Bay cliff in Split, which is 14-meter-high steep slope with a promenade at the cliff toe. Both rockfalls were triggered by heavy rainfall following dry periods. To better understand triggering mechanisms, these rockfalls were analyzed with regard to slope stability, climatic factors, and suction changes in the surface zone. The stability analyses in accordance with Eurocode 7 demonstrated that the slopes were in quasi-stable state with a safety factor greater than 1.0. Assuming that relative humidity (RH) in the surface pores and the atmosphere is equal, suction in the weathered surface zone was calculated using Kelvin’s equation, and daily/monthly/seasonal climatic factors (temperature, precipitation, RH) analyses were conducted using the data from the local meteorological station Marjan-Split. Suction difference for different time periods was analysed as an additional instability trigger and weathering agent. It was shown that the rockfalls were caused by a combination of the lowest (monthly and annual) suction value and the highest RH on the day of the rockfall, together with previous significant precipitation after a prolonged dry period and temperatures lower than the average monthly and on a decreasing trend. Such analyses may contribute to the understanding of rockfall triggering mechanisms and the prediction of future rockfall events.

Contributors

Authors

  1. Natasa Stambuk Cvitanovic University of Split, Faculty of Civil Engineering, Architecture and Geodesy, Croatia ORCID 0000-0003-1728-0021
  2. Ana Duhovic University of Split, Faculty of Civil Engineering, Architecture and Geodesy, Croatia ORCID 0000-0002-7094-7174

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References

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