Slope Destabilization Research Articles

Finite element modelling of landslide prone slopes around Rudraprayag and Agastyamuni in Uttarakhand Himalayan terrain

Himalayan mountain chains are neo-tectonically active and significantly susceptible to frequent geohazards like landslides, earthquakes, cloudburst and flash floods, etc. Himalayan slopes are characterized by highly fractured, jointed and sheared rock mass. This affects the strength of the rocks and thus largely influences the stability characteristic of slopes which have been aggravated by human intervention. The ongoing developmental activities, particularly in the last two decades, are responsible for large-scale destabilization of slopes. In rugged terrain, safer designs along hill-cut roads must be ensured. Despite extensive geotechnical works for slope stabilization done in the Himalayan range, slope sections evolve due to various natural and man-made factors are need to be understood in greater details. Proper evaluation and treatment were done on the cut slopes that are severely affected during Kedarnath disaster of June 2013. One of such roads is national highway from Rudraprayag to Gaurikund near Kedarnath. In this study, the stability of vulnerable road cut slopes from Rudraprayag to Agastmuni was investigated. Three key road cut slopes were considered. Finite element analysis was conducted using PLAXIS simulator. Factors of safety, stress, strain, horizontal and vertical displacement have been determined for each slope. The most unstable slope had a factor of safety (FoS) equal to 0.935, while the most stable slope had FoS equal to 2.56. Outcomes from simulation are in good agreement with the prevailing field conditions. Slope stability evaluation must be performed to ensure better safety and to achieve disaster mitigated design.

Timing of paraglacial rock‐slope failures and denudation signatures in the Cantabrian Mountains (North Iberian Peninsula)

AbstractGlacial erosion of hillslopes and stress changes induced by the transition from glacial to nonglacial conditions exert a strong influence on slope instability and are considered among the scope of paraglacial geomorphology. Failure mechanisms and coupling between paraglacial rock‐slope failures (RSFs) and fluvial erosion are difficult to define. Here we show a preliminary spatio‐temporal framework of paraglacial RSFs in a small catchment of the central Cantabrian Mountains, the San Isidro valley, with a dense concentration of RSFs. Preliminary radiocarbon dates obtained from two floodplain sequences deposited upstream from RSFs indicate that their sedimentation started as consequence of valley impoundment by RSFs after glacier retreat (after approximately 16.1 ka), consistent with the deglaciation pattern of nearby valleys. RSFs continued during the Holocene. Glacier erosion, debuttressing, and stress‐release conditions played an important role in slope destabilization as preparatory factors in all cases and probably triggered the oldest events. However, the long prefailure endurance (approximately 12 ka) between RSFs points to other factors such as rainfall and fluvial down‐cutting of hillslopes as triggers for Holocene events. Postglacial fluvial incision rates of 2.2–2.5 mm a−1 were estimated along gullies carved into bedrock areas nonaffected by RSFs. These values are one order of magnitude higher than previous rates based on other geomorphological proxies (~ 0.2 mm a−1), suggesting accelerated fluvial incision following the last deglaciation. Local RSFs contributed to increase in fluvial incision rates by a factor of three. This study provides a quantitative perspective of postglacial land degradation relevant for understanding postorogenic landscape evolution.

Stability and sensitivity analysis of Himalayan road cut debris slopes: an investigation along NH-58, India

The complex geological environment due to active tectonics and varied lithology with multiple phases of deformation and metamorphism led to a rugged topography and large destabilization of slopes in the Himalayan region. However, the ever-rising activities due to various ongoing developmental and urbanization processes in the region are contributing to instability of slopes. The significant number of causalities and massive economic loss is deliberately endangering Himalayan ecosystem due to landslide-related phenomena. Transportation corridors within Himalayan terrain experience frequent landslides, particularly the sections manifested by debris slopes. From several decades, the national highway-58, in Uttarakhand, Himalayas, has been endangered due to diverse and incessant slope failures. The present investigation demonstrates the stability appraisal along the strategic transportation corridor. These studies incorporate the various issues and causes pertaining to debris slides from Rishikesh to Devprayag, Uttarakhand. The numerical simulation assessment was undertaken by deterministic and sensitivity analyses by conventional limit equilibrium methods which is being augmented by much advanced and robust finite element tool. Factor of safety for each slope was determined, and correspondingly, best efficient slope stabilization remedies were proposed to enhance the stability of slopes. It is recommended that such strategic slope stability assessment should be performed within different vulnerable sections of the Himalayas and likewise regions for fruitful and sustainable step toward disaster mitigation.

Tensile Strength of Moso Bamboo Rhizome Affects Slope Stability

Recently bamboo forests unmanaged spread into steep slopes raising concern that such changes in vegetation might lead to slope destabilization. Thus knowledge on the tensile strength of bamboo rhizomes is needed for evaluating the effect of bamboo rhizomes on slope stability. However there are not many reports on the subject. In addition, because bamboo rhizomes and woody roots have different organization structures, these need to be tested for bamboo. This paper reports the tensile strength of Moso bamboo (Phyllostachys pubescens) rhizomes based on tensile tests considering their organization structure and on living rhizomes. Tensile strength was weaker in nodes than in internode of Moso bamboo, and structure observation revealed that, tensile strength decreased in areas where tissue fibers were discontinuous. The sectional area of the epidermal layer that affected tensile strength was directly proportional to cross sectional area. Because according to aprevious report rhizome diameter was smaller in unmanaged than in managed bamboo forests, so unmanaged bamboo forests might reduce slope stability.

Minimising Backbreak at the Dewan Cement Limestone Quarry Using an Artificial Neural Network

Abstract Backbreak, defined as excessive breakage behind the last row of blastholes in blasting operations at a quarry, causes destabilisation of rock slopes, improper fragmentation, minimises drilling efficiency. In this paper an artificial neural network (ANN) is applied to predict backbreak, using 12 input parameters representing various controllable factors, such as the characteristics of explosives and geometrical blast design, at the Dewan Cement limestone quarry in Hattar, Pakistan. This ANN was trained with several model architectures. The 12-2-1 ANN model was selected as the simplest model yielding the best result, with a reported correlation coefficient of 0.98 and 0.97 in the training and validation phases, respectively. Sensitivity analysis of the model suggested that backbreak can be reduced most effectively by reducing powder factor, blasthole inclination, and burden. Field tests were subsequently carried out in which these sensitive parameters were varied accordingly; as a result, backbreak was controlled and reduced from 8 m to less than a metre. The resulting reduction in powder factor (kg of explosives used per m3 of blasted material) also reduced blasting costs.

Are Icelandic rock-slope failures paraglacial? Age evaluation of seventeen rock-slope failures in the Skagafjörður area, based on geomorphological stacking, radiocarbon dating and tephrochronology

In Iceland there are numerous rock-slope failures, especially in the Tertiary basaltic formations of the northern, eastern and northwestern regions. The temporal pattern of rock-slope failures is fundamental for understanding post-glacial events. In the Skagafjörður district, central northern Iceland, 17 rock-slope failures were investigated to determine the age of their occurrence. A geomorphic survey was carried out to identify and characterize landform units, both on the rock-slope failures and in their immediate vicinity. In this coastal area, we used geomorphological stacking which included the relationship between rock-slope failures and raised beaches caused by glacial isostatic rebounds, the chronology of which was established in previous studies. We searched for depressions on the rock-slope failures to then excavate a series of pits and map the stratigraphy. The resulting stratigraphic framework was then validated using (i) radiocarbon dating of wood remains, and (ii) tephrochronology, both of which were complemented by age-depth model calibration. The results confirm that all the rock-slope failures potentially occurred before the Boreal (8ka), while 94% occurred before the Preboreal (10ka). They all potentially occurred after the glacial retreat following the maximal ice extent and the Preboreal. More precisely, 11 of them potentially occurred between the Preboreal and the first half of the Holocene. This study demonstrates the relationship between the deglaciation and destabilization of slopes during the paraglacial phase (debuttressing, decompression, glacial isostatic rebound, seismic activity, etc.), which are also controlling factors favouring landsliding, but are difficult to identify for each individual rock-slope failure.

PAULOWNIA ELONGATA SY HU IN FUNCTION OF IMPROVING THE QUALITY OF THE ENVIRONMENT

Interest in paulownia got its momentum around the world. With its fast-growing nature and large leaf surfaces this species can absorb significant amounts of sulfur dioxide and dust particles. The cities of Tuzla and Lukavac, as most other Bosnian-Herzegovinian towns, have a number of geo-ecological problems, and the most pronounced one is negative anthropopressing on the atmospheric complex and pedospheric cover. This area, especially during the winter period, has a disrupted air quality where the greatest polluters are individual heating places, transport, industry and energy sector. The pedologic cover of the wider area of Tuzla and Lukavac has suffered significant changes and is largely devastated. The processes of destruction of soils lead to complete destruction or formation of a new land with modified characteristics. High rainfall is a major cause of destabilization of slopes, but also is the negative anthropogenic activity in the area. Landslides have caused significant material damages, particularly in the residential structures of slope zones of the mentioned cities and suburban areas. This paper presents the basic biological characteristics of woody species paulownia elongata, and the possibility of planting it in areas that are now unused so to improve the quality of air, as well as on surfaces that are threatened by landslides.

Transport processes induced by metastable boiling water under Martian surface conditions

Liquid water on the Martian surface is expected to be metastable owing to low atmospheric pressure. Experiments at Martian conditions reveal that water and briny flows induce grain saltation and slope destabilization, with geomorphic consequences.

Large‐scale margin collapse during Messinian early sea‐level drawdown: theSWValencia trough,NWMediterranean

AbstractIn this study, detailed mapping of the ‘Messinian markers’ and examination of their geometrical relationships in theSWValencia trough (Western Mediterranean) have revealed the style and depositional processes associated with emersion of continental margins during the Messinian Salinity Crisis (MSC). Based on multichannel seismic profiles and well data, this article evidences the existence of two Messinian depositional units in intermediate basins (Complex Unit and Upper Unit) and four main Messinian erosional surfaces (Margin Erosion Surface, Bottom Surface, Top (Erosion) Surface and Intermediate Surface). Results show that (1) initial rapid sea‐level drawdown and exposure of the shelf and upper slope of the Valencia margin induced large‐scale destabilization of the continental slope and deposition of large detrital bodies at the base‐of‐slope in the form of major mass‐transport deposits (MTD); (2) as sea level continued to drop, the development of the Margin Erosion Surface attained full development on the margins and eroded the clastic units (MTDs) deposited during initial drawdown. At the same time, a submarine drainage network formed in the deepwater Valencia trough; (3) persistent lowstand and restrictive conditions in the area resulted in deposition of the evaporites that form the Upper Unit in theSWValencia trough.

Slope mass rating and kinematic analysis of slopes along the national highway-58 near Jonk, Rishikesh, India

The road network in the Himalayan terrain, connecting remote areas either in the valleys or on the hill slopes, plays a pivotal role in socio-economic development of India. The planning, development and even maintenance of road and rail networks in such precarious terrains are always a challenging task because of complexities posed by topography, geological structures, varied lithology and neotectonics. Increasing population and construction of roads have led to destabilisation of slopes, thus leading to mass wasting and movement, further aggravation due to recent events of cloud bursts and unprecedented flash floods. Vulnerability analysis of slopes is an important component for the “Landslide Hazard Assessment” and “Slope Mass Characterisation” guide planners to predict and choose suitable ways for construction of roads and other engineering structures. The problem of landslides along the national highway-58 (NH-58) from Rishikesh to Devprayag is a common scene. The slopes along the NH-58 between Jonk and Rishikesh were investigated, which experienced very heavy traffic especially from March to August due to pilgrimage to Kedarnath shrine. On the basis of slope mass rating (SMR) investigation, the area falls in stable class, and landslide susceptibility score (LSS) values also indicate that the slopes under investigation fall in low to moderate vulnerability to landslide. More attentions should be paid to the slopes to achieve greater safe and economic benefits along the highway.

Interaction between tunnel and unstable slope – Influence of time-dependent behavior of a tunnel excavation in a deep-seated gravitational slope deformation

A back analysis of old tunnels in an unstable slope context leads to consider several situations of tunnel entering a slope: cross-cutting tunnel to the slope, oblique tunnel to the slope, or shallow tunnel parallel to the slope. Identified pathologies of structures vary depending on these situations. In the context of a shallow tunnel, the tunnel excavation leads to a slope destabilization due to a more or less important deconfinement of the surrounding massif. Construction techniques influence, on one hand, slope surface displacement acceleration, on the other hand, structural damages in the tunnel lining. Nevertheless, the interaction between tunnel and unstable slope depends on the distance between the slope surface and the tunnel lining plot according to the tunnel diameter (D) and on the geological, geomorphological, hydrological and seismic contexts of the slope. This research focuses on different mechanisms of slope instability in a glacial unloading context, especially in creeping contexts, and on damages affecting the structure of tunnels parallel to the slope. Through numerical simulations, the influence of the construction techniques was studied; so was the choice of the tunnel situation, more or less away from the slope surface. Mainly the delay time before tunnel structure implementation) on the damage lining processes, the interaction between tunnel and slope surface displacements and their time evolution have been taken into account for the most critical tunnel situation in the slope. The different situations of tunnel in the slope permit to set in evidence the safety distance from the slope in the context of a slow glacial unloading mechanism.

Deep-seated gravitational deformation of mountain slopes caused by river incision in the Central Range, Taiwan: Spatial distribution and geological characteristics

Fluvial undercutting can cause the large-scale destabilization of mountain slopes and induce deep-seated gravitational slope deformation (DGSD) that eventually leads to catastrophic failures. This study analyses these processes in the catchment of the Dahan River, northern Taiwan. The area has experienced phases of river incision of up to 600m since the middle to late Pleistocene, and middle Pleistocene paleosurfaces at higher elevations were incised to form V-shaped valleys. A DGSD inventory was compiled by visual interpretation of high-resolution images, and field surveys were conducted to clarify the geological structures associated with DGSDs and major rockslide-avalanches. The observed relationships between DGSDs and the topography modified by long-term river incision show that about 53% of all DGSDs occurred on slopes along the rims of paleosurfaces, which is approximately 2 and 2.5 times as many as in the incised valleys and on the paleosurfaces, respectively. A comparison of the power-law scaling exponents of cumulative frequency–area distributions shows that the frequency of DGSDs along the rims of the paleosurfaces decreases less rapidly with DGSD area than for DGSDs on other slopes. Geological investigations suggest that there are two dominant types of DGSD: one is flexural toppling of slate and argillite with high-angle cleavage, and the other is buckling of alternating beds of sandstone and mudstone on parallel or underdip cataclinal slopes. Catastrophic landslides observed along or below the rims of paleosurfaces were preceded by buckling of alternating beds of sandstone and shale. These beds dipped at 50° to 58°, and each bed was 10−1–100m thick. This study suggests that the peripheral zones of the paleosurfaces may be most susceptible to future catastrophic landslides, particularly on parallel or underdip cataclinal slopes comprising alternating beds of sandstone and mudstone dipping at 50° to 60°. Thus, an understanding of the geological characteristics, spatial distribution of DGSD occurrence, and landscape evolution within a particular area can provide important information for landslide hazard-level zoning.

Micro-meteoroid seismic uplift and regolith concentration on kilometric scale asteroids

Seismic shaking is an attractive mechanism to explain the destabilisation of regolith slopes and the regolith migration found on the surfaces of asteroids (Richardson, J.E., Melosh, H.J., Greenberg, R. [2004]. Science 306, 1526–1529. http://dx.doi.org/10.1126/science.1104731; Miyamoto, H., et al., 2007). Here, we use a continuum mechanics method to simulate the seismic wave propagation in an asteroid. Assuming that asteroids can be described by a cohesive core surrounded by a thin non-cohesive regolith layer, our numerical simulations of vibrations induced by micro-meteoroids suggest that the surface peak ground accelerations induced by micro-meteoroid impacts may have been previously under-estimated. Our lower bound estimate of vertical accelerations induced by seismic waves is about 50 times larger than previous estimates. It suggests that impact events triggering seismic activity are more frequent than previously assumed for asteroids in the kilometric and sub-kilometric size range. The regolith lofting is also estimated by a first order ballistic approximation. Vertical displacements are small, but lofting times are long compared to the duration of the seismic signals. The regolith movement has a non-linear dependence on the distance to the impact source which is induced by the type of seismic wave generating the first movement. The implications of regolith concentration in lows of surface acceleration potential are also discussed. We suggest that the resulting surface thermal inertia variations of small fast rotators may induce an increased sensitivity of these objects to the Yarkovsky effect.

Susceptibility mapping and estimation of rainfall threshold using space based input for assessment of landslide hazard in Guwahati city in North East India

Abstract. Slopes are the most common landforms in North Eastern Region (NER) of India and because of its relatively immature topography, active tectonics, and intense rainfall activities; the region is susceptible to landslide incidences. The scenario is further aggravated due to unscientific human activities leading to destabilization of slopes. Guwahati, the capital city of Assam also experiences similar hazardous situation especially during monsoon season thus demanding a systematic study towards landslide risk reduction. A systematic assessment of landslide hazard requires understanding of two components, "where" and "when" that landslides may occur. Presently no such system exists for Guwahati city due to lack of landslide inventory data, high resolution thematic maps, DEM, sparse rain gauge network, etc. The present study elucidates the potential of space-based inputs in addressing the problem in absence of field-based observing networks. First, Landslide susceptibility map in 1 : 10,000 scale was derived by integrating geospatial datasets interpreted from high resolution satellite data. Secondly, the rainfall threshold for dynamic triggering of landslide was estimated using rainfall estimates from Tropical Rainfall Measuring Mission Multi-satellite Precipitation Analysis. The 3B41RT data for 1 hourly rainfall estimates were used to make Intensity-Duration plot. Critical rainfall was estimated for every incidence by analysing cumulative rainfall leading to a landslide for total of 19 incidences and an empirical rainfall intensity-duration threshold for triggering shallow debris slides was developed (Intensity = 5.9 Duration-0.479).

Landslide risk assessment using a multi-method approach in Hashtchin region (NW of Iran)

Landslide risk assessment methods can be carried out at the regional or site scales. In the present study, logistic regression method (a quantitative method) and the fuzzy sets theory (a semi-quantitative method) have been used for landslide hazard and risk assessment, respectively, at a regional scale. The hazard potential and resource damage potential have been obtained from the hazard zonation and the land cover / land use maps. The landslides occurrence probability has been estimated based on the causal factors responsible for slope destabilization, in a specified period of time. At this stage, 75 % of the pixels with landslide have been entered to the model as the estimation group, in which new landslides have occurred with a moderate to high intensity or at least have displaced once or more in the past 50 years. The accuracy of the results from the statistical estimation of landslide occurrence probability have been evaluated and validated based on 25 % of the remaining landslide pixels. Landslide hazard assessment representing the accuracy of prediction model is 83.2 %. The risk zonation was performed by combination of the hazard potential and resource damage potential and using the fuzzy algebraic product operator in the region. Results show that 62.9 % of the area is placed in low and very low risk categories and 19.5 % of the rangeland areas are located in class of high risk zone. Proposed method was used for landslide risk assessment in Hashtchin region (in the northwest of Iran), and obtained results can be used in the land use planning, developmental activities and implementation of building.

Influence of inherited topography on gravitational slope failure: three‐dimensional numerical modelling of the La Clapière slope, Alpes‐Maritimes, France

AbstractGravitational slope failure involves rock slopes at various scales. Nowadays, it is accepted that different factors influence slope destabilization, including topography. In many cases, slope failure occurs between tributary valleys cutting the slope. In this study, we ask what influence tributary valleys have on slope failure. To tackle this question, we developed a 3‐D numerical model of the La Clapière Slope and then examined a series of simplified 3‐D models with different geometries of tributary valleys (spacing and depth). Our results show that: (1) whatever considered in situ stresses are, including the third dimension reduces the destabilization threshold compared with 2‐D models; and (2) the spacing and the depth of tributary valleys influence slope failure. For shallow incisions, increasing the lateral spacing between tributary valleys does not affect failure localization but does increase slope damage (to a stable value from 2000 m). However, deeper incision does not affect slope damage but does contribute to failure localization. When the spacing is less than 1500 m, the part of the slope between tributary valleys is not involved in the failure process, but for spacings above 1500 m slope failure occurs between tributary valleys.

Slope destabilization during the Messinian Salinity Crisis

During the Messinian Salinity Crisis, ~6Myr ago, deep canyons were incised when a huge sea-level drawdown of ~1.5km affected the Mediterranean Sea. Nearly contemporaneously, more than 2km of evaporites accumulated in the basin. This event was the consequence of a complex interaction of tectonic movements and global sea-level variation associated with climatic evolution. This unusual event ended with the reflooding of the Mediterranean area. In this paper, using seismic line interpretation, we show that several landslides occurred in various parts of the Mediterranean Basin during this crisis. Three of these landslides are well preserved, and their dynamics were analyzed. Modeling of the slope stability demonstrates that these landslides may have been due to (i) the relief created by the deep erosion, and/or (ii) the reflooding, which triggered a pore pressure increase. The relatively small run-out distances of the three landslides suggest propagation in a submarine environment and triggering by sea-level rise.

A Late Holocene deep-seated landslide in the northern French Pyrenees

A very large deep-seated landslide (DSL) in the northern Pyrenees with over ∼1.4×109m3 was mapped and dated based on sedimentation rates and 10Be terrestrial cosmogenic radionuclide surface exposure (CRE) dating. Our analysis on the landslide reveals the role of inherited structures in the landslide process, and highlighted typical gravitational morpho-structures and a small lake trapped at the toe of the landslide head scarp. The rate of lake sedimentation (0.86±0.57mmyr−1) also provided us with the approximate age of the landslide: 1106±540yr. The CRE dating result highlights two main slope destabilization phases. Then we discussed the history of DSL activity and its controlling factors. Information related to historic markers and the absence of particular climate markers and changes during the Medieval Dark Ages point to a single event in AD 1380 due to a major seismic event (Lavedan earthquake).

Geological map of the Mount Ciantiplagna rock avalanche (Chisone Valley, Italian Western Alps)

The 1:10,000 scale geological map of the Mount Ciantiplagna rock avalanche, located in the upper Chisone Valley, encompasses an area of 21.4 km2 affected by the most extensive rock slope failure identified in the Italian Western Alps. The landslide, originated at 2605 m a.s.l., involved massive calcschist with subordinate intercalations of serpentinite and metabasite of the Cerogne-Ciantiplagna Unit (Piedmont Zone, Pennidic Domain). The blocky accumulation covers an area of 3.88 km2 with a corresponding volume of 157 × 106 m3. The rock avalanche traveled a horizontal distance of 4.6 km with a vertical drop of 1460 m and stopped at 1150 m a.s.l. against a transverse moraine situated at the mouth of the Rio del Laux Valley. The landslide deposits created a cross-valley barrier with the development of a large fluviolacustrine basin extending 4 km upstream and with a maximum depth of 120 m. Detailed field mapping and numerous drillholes highlighted that the rock avalanche deposits rest above an earlier rock slide that involved a huge ophiolitic mass of serpentinite and metabasite. In the valley bottom the original surface of the rock avalanche accumulation is not preserved. Several fluvial terraces suspended up to 120 m above the Chisone river have been interpreted as the product of erosion by the stream network at the expense of the blocky deposit. Destabilization of the Mount Ciantiplagna southern slope due to the emplacement of the rockslide can be reasonably invoked as the most likely triggering factor. Extreme rainfall and the seismic activity (I o = VII–VIII) that affects the central sector of the Italian Western Alps can be regarded as further potential triggers. The precise age of the rock avalanche is not known: nevertheless the overlapping of the distal portion of the accumulation over late-glacial moraines, the presence of some late Copper Age archaeological sites close and within the landslide perimeter and the deep dissection of the blocky deposit are in agreement with an early post-glacial age. The geological map presented here provides detailed morphological and stratigraphical information allowing the reinterpretation of the kinematics of the Mount Ciantiplagna landslide.

Modeling permafrost extension in a rock slope since the Last Glacial Maximum: Application to the large Séchilienne landslide (French Alps)

Recent dating performed on large landslides in the Alps has revealed that the initiation of instability did not immediately follow deglaciation but occurred several thousand years after ice down-wastage in the valleys. This result indicates that debuttressing is not the immediate cause of landslide initiation. The period of slope destabilization appears to coincide with the wetter and warmer Holocene Climatic Optimum, indicating a climatic cause of landslide triggering, although the role of seismic activity cannot be ruled out. A phenomenon which may partly explain the delay between valley deglaciation and gravitational instability is the temporal persistence of thick permafrost layers developed in the Alps since the Last Glacial Maximum (LGM). This hypothesis was tested through 2D thermal numerical modeling of the large Séchilienne landslide (Romanche valley, French Alps) using plausible input parameter values. Simulation results suggest that permafrost vanished in the Séchilienne slope at 10 to 11ka, 3000 to 4000years following the total ice down-wastage of the Romanche valley at 14.3ka. Permafrost persistence could have contributed to the failure delay by temporally strengthening the slope. Numerical simulations also show that the permafrost depth expansion approximately fits the thickness of ground affected by gravitational destabilization, as deduced from geophysical investigations. These results further suggest that permafrost development, associated with an ice segregation mechanism, damaged the rock slope and influenced the resulting landslide geometry.