Deformation characteristics and mechanism of an impoundment-induced toppling landslide in Baihetan Reservoir based on multi-source remote sensing

Impoundment and water level fluctuations in reservoirs can induce landslides,especially during initial filling and drawdown.Since the initial impoundment in April 2021,multiple landslides have occurred within the Baihetan(BHT) reservoir,which is located at the boundary of Sichuan and Yunnan province in southeast China.However,due to the complex terrain conditions of reservoir banks,traditional landslide research methods,such as surveys,deformation monitoring,and geotechnical experiments,cannot be effectively conducted in a timely manner.In recent years,the development of remote sensing technology has addressed the shortcomings of traditional landslide research methods that may not be promptly carried out.In particular,interferometric synthetic aperture radar(InSAR) technology,capable of measuring subtle deformations,and portable small unmanned aerial vehicles(UAVs) have played a significant role.This study integrates multiple remote sensing data sources,including InSAR results,optical remote sensing images,digital elevation model(DEM),and UAV imagery,to investigate and elucidate the deformation characteristics and mechanisms of the Xiaomidi(XMD) landslide developed on the left bank of Jinsha River,about 100 km from the BHT hydropower dam site.The spatial deformation distribution of the landslide before and after impoundment and the deformation time series during filling were examined.Monitoring water level variation and analysing the deformation process of the landslide were achieved by employing continuous synthetic aperture radar(SAR) intensity images and DEM.UAV photography was utilized to assist in the verification of ground deformation.The findings suggest that the weak strength of the reversed bedding strata structure and the steep slope eroded by the Jinsha River are inherent factors that contribute to the development of the landslide.The rise in the water level leads to softening of the rock mass at the slope toe,thereby directly facilitating the acceleration of landslide deformation.The toppling deformation of the lower rock mass initiates the formation of surface cracks and localized uneven subsidence in the overlying colluvial deposits.

Deformation and failure of a high-steep slope induced by multi-layer coal mining

During underground mining,accurate revelation on the deformation and failure mechanisms of a high-steep slope under multi-layer mining conditions facilitates the prevention and control of geological disasters in mines.Numerical simulation based on discrete element theory can be used to explore the characteristics and mechanism of action of deformation and failure of a slope under complex geological and multi-layer mining conditions.By utilising PFC2 D(particle flow code) software,the deformation and failure characteristics of a high-steep slope in Faer Coal Mine in Guizhou Province,China were investigated.Additionally,the mechanism of influence of different numbers of mining layers on the deformation and failure of the high and steep slope was elucidated.The result showed that after the goaf passed by the slope toe,multi-layer mining aggravated the subsidence and deformation of the slope toe:the slope toppled forward as it sank.The toppling of the slope changed the slope structures:the strata in the front of the slope were transformed from anti-dip to down-dip features.Extruded by collapsedtoppled rock mass,the slope toe and the rock mass located in the lower part of the slope toe generally exhibited a locking effect on the slope.Multi-layer mining degraded the overall stability of the slope,in that the total displacement of the slope was much greater than the total mining thickness of the coal seams.Based on the aforementioned research,ideas for preventing and controlling geological disasters during mining operations under a high-steep slope were proposed.