Insight into the Permeability and Microstructure Evolution Mechanism of the Sliding Zone Soil: A Case Study from the Huangtupo Landslide, Three Gorges Reservoir, China

A large number of laboratory investigations related to the permeability have been conducted on the sliding zones.Yet little attention has been paid to the particular sliding zones of the slideprone Badong Formation.Here,we experimentally investigate the permeability nature and the mechanism of seepage in the viscous sliding zone of the Huangtupo Landslide.Saturated seepage tests have been performed first with consideration of six dry densities and thirteen hydraulic gradients,in conjunction with the mercury intrusion porosimetry test and scanning electron microscopy test for the microstructure analysis after seepage.The results show that seepage in the sliding zone soil does not follow Darcy’s Law,since there is a threshold hydraulic gradient(i0)below which no flow is observed and a critical hydraulic gradient(icr)over which the hydraulic conductivity(K)tends to be stable.The percentage of bound water could be responsible for the occurrence of i0 and icr.Furthermore,pore size distributions(PSD)less than 0.6µm and between 10 and 90µm exhibit positive and negative correlations with the i0,respectively,indicating that the i0 is related to the PSD.The mechanism accounting for this result is that pore water pressure forces fine clay particles into the surrounding large pores and converts arranged particles to discretely distributed ones,thereby weakening the connectivity of pores.The seepages in the sliding zones behave differently from that in the sliding mass and sliding bed in response to the permeability.

Centrifuge modelling of landslides and landslide hazard mitigation:A review

Landslides are serious geohazards that occur under a variety of climatic conditions and can cause many casualties and significant economic losses.Centrifuge modelling,as a representative type of physical modelling,provides a realistic simulation of the stress level in a small-scale model and has been applied over the last 50 years to develop a better understanding of landslides.With recent developments in this technology,the application of centrifuge modelling in landslide science has significantly increased.Here,we present an overview of physical models that can capture landslide processes during centrifuge modelling.This review focuses on(i)the experimental principles and considerations,(ii)landslide models subjected to various triggering factors,including centrifugal acceleration,rainfall,earthquakes,water level changes,thawing permafrost,excavation,external loading and miscellaneous conditions,and(iii)different methods for mitigating landslides modelled in centrifuge,such as the application of nails,piles,geotextiles,vegetation,etc.The behaviors of all the centrifuge models are discussed,with emphasis on the deformation and failure mechanisms and experimental techniques.Based on this review,we provide a best-practice methodology for preparing a centrifuge landslide test and propose further efforts in terms of the seven aspects of model materials,testing design and equipment,measurement methods,scaling laws,full-scale test applications,landslide early warning,and 3D modelling to better understand the complex behaviour of landslides.

Study on Geomechanical and Physical Models of Necking-Type Slopes

A simplified geomechanical model was proposed by considering three typical neckingtype slopes;this model lays a foundation for the further investigation of the deformation behaviors of such slopes.Three physical models of necking-type slopes were built according to the geomechanical model with slope evolution stages.Finally,preliminary calculations related to the arching effect in the physical model were conducted.Three evolution stages of necking-type slopes,namely,the initial stage,compression stage,and failure stage,were presented based on the formation and disappearance of the arching effect within the slope.The specific parameters of the geomechanical model were given.In the setup of the tilting test,the failure angle of the necking-type slope model was calculated to be approximately 50°with a large lateral resistance coefficient.The proposed geomechanical model and physical models of necking-type slopes provide guidance for the establishment of geomechanical and physical models of landslides at specific sites.