25 Jul 2022
25 Jul 2022
Status: this preprint is open for discussion.

A new analytical method for stability analysis of rock blocks with cavity in sub-horizontal strata by considering eccentric effect

Xushan Shi1, Bo Chai1,3,4, Juan Du1,2,4, Wei Wang1,3,4, and Bo Liu1 Xushan Shi et al.
  • 1School of Environmental Studies, China University of Geosciences, Wuhan, 430078, China
  • 2Centre for severe weather and climate and hydro-geological hazards, Wuhan, 430078, China
  • 3Hubei Key Laboratory of Yangtze Catchment Environmental Aquatic Science, Wuhan, 430078, China
  • 4Research Center for Geohazards Monitoring and Warning in Three Gorges Reservoir, Wanzhou, 404000, China

Abstract. The basal cavity of rock block formed due to differential weathering is an important predisposing factor for rockfall, in hard-soft interbedded rocks. The rock block falling due to eccentric effect with the failure modes of toppling or sliding is defined as biased rockfall in this study. Considering the non-uniform stress distribution due to eccentric effect, a new analytical method for three-dimensional stability analysis of biased rockfall is proposed. In addition, a set of factors of safety (Fos) against partial damage (compressive and tensile damage of soft underlying layer) and overall failure (toppling and sliding of hard rock block) are used to determine the rockfall susceptibility level. The analytical method was applied and validated with the biased rockfalls in the northeast edge of Sichuan basin in Southwest China, where a large amounts of rockfalls develops, composed of overlying thick sandstone and underlying mudstone. The evolution process of biased rockfalls is divided into four stages, initial state, cavity formation, partial unstable and failure. The proposed method is validated by calculating Fos of the typical unstable rock blocks in the study area. It is indicated that the continuous retreat of cavity causes the stress redistribution between hard and soft rock layers. Consequently, the development of eccentric effect leads to the damage of underlying soft rock layer and the further failure of hard rock block. The critical cavity retreat ratio is determined as 0.33 to classify the low and moderate rockfall susceptibility. The proposed analytical method is effective for the early identification of biased rockfall, which is significant for rockfall prevention and risk mitigation.

Xushan Shi et al.

Status: open (until 05 Sep 2022)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • CC1: 'Comment on egusphere-2022-658', Wei Qian, 28 Jul 2022 reply
  • CC2: 'Comment on egusphere-2022-658', Xin Liang, 31 Jul 2022 reply

Xushan Shi et al.

Xushan Shi et al.


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Short summary
A three-dimensional stability analysis method is proposed for biased rockfall with basal cavity. Four failure modes are considered according to rockfall evolution process, including partial damage of underlying soft rock and overall failure of hard rock block. This method is validated with the biased rockfalls in Sichuan basin, China. Critical cavity retreat ratio from low to moderate rockfall susceptibility is 0.33. This method could facilitate rockfall early identification and risk mitigation.