Retrogressive Landslide Research Articles

Mapping Complex Landslide Scars Using Deep Learning and High-Resolution Topographic Derivatives from LiDAR Data in Quebec, Canada

This study evaluates deep learning (DL) models, particularly ResU-Net with attention mechanisms, for mapping landslides in Quebec, Canada, utilizing high-resolution digital elevation model (HRDEM) data and its seven derivatives (slope, aspect, hillshade, curvature, ruggedness, surface area ratio, and max difference from mean). Three scenarios were considered to assess the effectiveness of various features in landslide segmentation: training the model on all features, each feature individually, and on slope and hillshade. Model performance on individual features was significantly poor, while the model trained with hillshade and slope outperformed the model using all seven features, particularly in F1-score (improved by 8% for rotational landslides and 11% for retrogressive landslides) during validation. Furthermore, for the test dataset, model performance on all seven features was compared against slope and hillshade. As a result, for rotational landslides, slope and hillshade achieved F1-scores of 0.68 and 0.93 for rotational and retrogressive landslides, respectively, while the same metrics using all features were 0.61 and 0.83, respectively. This suggests hillshade and slope provide the most relevant information and reduce computational complexity. Overall, the findings enhance our understanding of HRDEM derivatives and emphasize the importance of feature selection in optimizing model performance and reducing computational complexity.

The role of platform margin collapses and slope landslides in the initiation and evolution of submarine canyons

The Zhongsha Platform is the largest modern isolated carbonate platform of around 8600 km2 in the South China Sea, providing a unique case study for sedimentary processes in pure carbonate settings. High-resolution multibeam bathymetric data, two-dimensional seismic profiles, and surface sediment cores are utilizes to reveal the initiation and evolution of submarine canyons on the northeastern slope of the Zhongsha Platform. Three submarine canyons are revealed within the survey area that incise the slope at water depths between 600 and 4100 m. C1 presents a linear pattern, whereas C2 and C3 exhibit dendritic morphologies. A large-scale scalloped collapse has deeply excavated the platform margin and slope. Within this catastrophic failure, C2 originated in a northeastward orientation and subsequently converted to an eastward direction with a length of 54.8 km. It is distinguished by the erosion of numerous tributaries in the upper course, the transition of flow direction in the middle course, and the presence of retrogressive landslides in the lower course. Slope landslides extend eastward from middle-lower slope towards the oceanic basin at water depths ranging from 2300 to 4200 m. A series of scarps and immature canyons have developed with escarpments showing pronounced relief at the landslide heads. The triggering mechanisms of platform margin collapses and slope landslides are attributed to sediment aggradation, slope oversteepening, gravity flows, relative sea-level changes, surface monsoon currents, and deep cyclonic circulation. The canyon evolution is explained through four stages: Inception stage, sediment instability on platform margin and slope-toe; Expansion stage, the presence of platform margin collapses and slope landslides; Development stage, the initiation of submarine canyons eroded by gravity flows with downslope and retrogressive erosion; Present stage, the upper slope canyon incised into the landslide area and ultimately integrated with the lower slope canyon, creating an elongated modern canyon. This work contributes to enhance our understanding of the detailed morphology, transport processes, and triggering mechanisms of submarine canyons in the pure carbonate systems.

Prediction of retrogressive landslide in sensitive clays by incorporating a novel strain softening law into the Material Point Method

Sensitive clays, when subjected to large strains, exhibit a unique strain-softening behavior, transforming into a remolded liquid with remarkably low shear strength. When a slope fails, this behavior leads to the remolded clay moving away from its original position, triggering subsequent failures and catastrophic outcomes. To accurately predict such scenarios, it is crucial to incorporate realistic strain-softening characteristics into the constitutive soil model. This paper presents a novel yet practical strain-softening law developed by the authors that effectively captures the post-peak behavior of sensitive clays down to their remolded strength. The softening law is implemented in an elastoplastic Mohr-Coulomb model and incorporated into Anura3D, an open-source software that uses the Material Point Method to simulate large deformations. The constitutive model is calibrated by simulating the stress-strain behavior through direct shear tests conducted at three sensitive clay landslide locations. The accuracy of the overall numerical framework is assessed by predicting the post-failure movements of these landslides. Notably, two of the landslides, Sainte-Monique (1994) and Saint-Jude (2010), have previously been analyzed using other numerical tools, allowing for a comparative analysis with the method presented here. The third landslide, the Saint-Luc-de-Vincennes landslide, representing a composite flow slide and spread, has been numerically simulated for the first time. The post-failure behavior observed in the landslide events is compared with field observations and other numerical analyses. The results show that the MPM models with the proposed strain-softening law can reasonably predict post-failure retrogression and runout distance, which are crucial parameters for determining the risk of landslides in sensitive clays.

Regional activity of landslide movements affecting the bank of meandering river: Insights using tree-ring based methods

Landslides on the banks of meander bends of lower rivers pose a potential risk to the navigability of rivers, but also to their potentially dangerous damming. To properly understand the relationship of river action on the stability of adjacent landslides, it is necessary to analyse the historical evolution and spatial extent of landslide activity. In this study, the results of a regional reconstruction of landslide movements on the lower reaches of the Váh River (central Slovakia) are presented, which allows for a more comprehensive disclosure of the river-slide relationship compared to classical case studies. Using data from a 408 tree-ring series of 204 disturbed trees, 43 reactivations of five landslides were dated over the last ca. 45 years. Analysis of the relationship between the spatial extent of landslide activity and distance from the river revealed that in two cases there was a direct relationship where landslide activity gradually decreased with increasing distance from the river (these were the landslides closest to the river). Given the absence of erosional forms on the riverbank, it is likely that the landslides are not being destabilized by lateral river erosion and the relief of their faces, but rather by the loading of their bodies due to rising groundwater during floods. On the other hand, one landslide (furthest from the river) showed increasing landslide activity towards the main scarp. This pattern is consistent with the retrogressive landslide development generally expected for other landslides in the wider region. For the remaining two landslides, no significant relationship between spatial landslide activity and distance from the river was found, which, however, cannot rule it out, but rather suggests that the influences on the initiation of landslide movements in this case are very complex and probably combine both the influence of groundwater level fluctuations and the occurrence of critical rainfall events.

Migration and controls of Shenhu submarine canyons in the upper continental slope of northern South China Sea: Insights from three‐dimensional seismic data mapping

AbstractSubmarine canyons, prominent features on continental margins, hold significant scientific and engineering implications. Despite extensive research on various types of submarine canyons, current understanding of those canyons developed on the upper continental slope, recognized as the most common type globally, remains limited. The Shenhu Canyons on the upper continental slope of the northern South China Sea, comprising over 19 subparallel features persistently developed from the Late Miocene to Quaternary, offer an excellent opportunity for in‐depth study. Previous assumptions suggested a unidirectional eastward migration of these canyons parallel to the host margin, primarily based on observations from two‐dimensional transverse seismic profiles. However, this study's analysis using three‐dimensional seismic data mapping reveals that not all canyons have migrated eastward; 28% display an opposite or a zigzag patterned migration, challenging previous assumptions. The eastward migration of the Shenhu Canyons on the eastern slope of the palaeo‐Pearl River shelf‐edge delta can be linked to the south‐east–southward progradation of the host margin and the palaeo‐shelf‐edge delta. However, the overall eastward migration pattern is complicated by submarine landslides and turbidity current processes. Landslides can influence the direction and magnitude of canyon migration through four mechanisms: turbidity current diversion; retrogressive development of canyon‐wall landslides; retrogressive landslides on surrounding open slopes; and emplacement of landslides in canyon thalwegs. These mechanisms may result in widening, bifurcation, confluence or obstruction of canyons, contributing to canyon migration. Erosion by turbidity currents can trigger canyon‐wall failures, which in turn promote the lateral migration of the canyons. If overspilled turbidity currents lead to the growth of levées in the lower reaches, canyon confinement increases, suppressing lateral migration. The inherited high‐gradient Palaeogene syn‐rift tectonic slope, combined with the depositional delta‐front slope of the palaeo‐shelf‐edge delta, creates favourable conditions for the initiation and persistent development of the straight Shenhu Canyons. This comprehensive analysis provides valuable insights into the complex dynamics and factors influencing the migration of upper continental slope submarine canyons.

Study on the Stability of Large Retrogressive Landslide and Treatment Technology

To study the catastrophic mechanisms of retrogressive landslides and assess the stability post treatment, it is essential to examine the internal factors contributing to landslides. This involves a detailed analysis of the characteristics of engineering geology, environmental conditions, and the impact of engineering construction activities on the landslide area. The comprehensive treatment schemes for landslides are determined using deep displacement monitoring and numerical analysis. It has been shown that the process of the landslide mechanism can be divided into four stages, i.e., primary structure breakage, rock mass damage deterioration, rock mass softening in water, and rainfall-induced instability failure. Rock mass damage and rainfall caused by slope excavation are the main causes and inducements of landslide instability. The monitoring results of deep displacement have shown that the sliding surface of a landslide is fully integrated. To mitigate the risk of secondary disasters, this study proposes a comprehensive set of measures based on the mechanisms of landslide instability and the support principle of a compensated traction zone. These measures include the implementation of prestressed anti-slide piles, the application of molten steel pipe grouting, and enhanced drainage techniques. The displacement of the slope was reduced, showing that the treatment scheme had a good reinforcement effect.

The study of the natural frequency evolution and numerical simulation of retrogressive landslides

A retrogressive landslide is influenced by the cyclical fluctuations in reservoir water levels is considered a common natural disaster. Tension cracks are important indicators for assessing landslide status in the case of retrogressive landslides. Displacement monitoring is a commonly used method and provides an intuitive reflection of the landslide deformation; however, it does not directly indicate the depth of the tension cracks. Based on the principles of vibrational dynamics, a retrogressive landslide is proposed to be initially classified as a single-mass spring oscillator model before the development of cracks. Following the development of tension cracks, the model can be classified as a double-mass spring oscillator model. The model patterns are verified through numerical simulations using ABAQUS. Based on the numerical simulations, with an increase in the number of reservoir water cycle fluctuations, the displacement and stress of the landslide exhibit periodic growth. However, during displacement growth, the tension cracks do not necessarily increase. As the tension cracks deepen, the landslide transitions from a single-mass spring oscillator model to a double-mass spring oscillator model, with the appearance of a second-order natural frequency. Moreover, as the tension cracks deepen, the numerical values of the natural frequency change. The maximum change in first-order natural frequency is 3.5 Hz. The maximum change in second-order natural frequency is 4.5 Hz. The variation in the natural frequency can reflect the depth of development of the landslide's tension cracks and, consequently, indicate changes in the stability state of the landslide.

A three-dimensional smoothed particle hydrodynamics analysis of multiple retrogressive landslides in sensitive soil

Numerical modelling and analysis of three-dimensional multiple retrogressive landslides of Saint-Jude landslide in sensitive clay is conducted. The investigations of the three-dimensional effects in determining the extent of landslides are concerned. To accurately simulate the extremely large deformation caused by progressive soil failure, a special form of SPH formulation known as finite particle method (FPM) is adopted. A hypoelastic–plastic model with strain softening is implemented to capture the key feature of the mechanical behaviour of the sensitive clay in undrained condition. The multiple progressive failure process, the final run-out stretch, and the retrogression distance of the Saint-Jude landslide are compared quantitatively with the data from site investigation. Furthermore, three-dimensional effects and influences of various factors, including slope morphology and soil properties, are discussed for better understanding of the development of retrogressive landslides in sensitive soil.

Updated Lagrangian nonlocal general particle dynamics for large deformation problems

The traditional general particle dynamics (GPD) has been successfully applied in modeling fracture propagation, frictional contact and stick–slip problems in rocks. In this study, the updated Lagrangian nonlocal general particle dynamics (UL-NGPD) method is proposed to solve large deformation problems. In the UL-NGPD, the continuity equation and momentum equation are reformulated in the integro-differential formulation by introducing nonlocal theories in the updated Lagrangian framework. The artificial viscosity and artificial force state are utilized to enhance the numerical stability and accuracy in modeling large deformation. The nonlocal velocity gradient in the deformed configuration is used to update the Cauchy stress rate from the Drucker-Prager elasto-plastic constitutive model with strain-softening behaviour for solids. The UL-NGPD paradigm is numerically implemented through an explicit Predictor-Corrector scheme for high-performance computing. The stability and accuracy of the UL-NGPD are verified by numerical tests on compression test, slope stability analysis and aluminum bar collapse experiment. Thereafter, simulations of granular soil collapse and retrogressive landslide in sensitive clays are presented to demonstrate its efficacy and robustness in modeling challenging geotechnical problems involving large deformation. The numerical results show that the proposed UL-NGPD is powerful and suitable for analyzing large deformation problems in geotechnical engineering.

Insight into the crack characteristics and mechanisms of retrogressive slope failures: A large-scale model test

Cracks in the crown area are one of the important indicators in the instability of the landslide headscarp, potentially offering early warnings for landslide hazards. Due to the complex causes of crack formation and numerous influencing factors, the understanding of crack development characteristics is still insufficient. In this paper, a large-scale soil slope model test is carried out through a large tilting platform to simulate the whole process of retrogressive slope failures including the first-time failure and the enlargement of the failure. The characteristics of crack development, the relations between internal slope parameters (e.g., internal strain and earth pressure) and cracks, and the evolutionary mechanisms of retrogressive failures are focused. The model test is monitored by high-tech equipment, including optical fibres, pressure gauges, and cameras. The results show that crack developments are divided into four stages based on crack location, quantity, and size. Optical fibre monitoring shows that the areas of tension crack development fall within the negative strain area in the slope model. In addition, the failure mode of the retrogressive landslides can be summarized in three stages: a deformation stage with sparse local cracks, a destabilizing stage with main cracks, and a retrogressive failure stage with dense secondary cracks. This study offers preliminary insights into the relations between crack development and the mechanisms in soil multiple retrogressive failures, which can be beneficial for better identifying and interpreting landslides at sites through crack monitoring.

Remoulding energy as a criterion in assessing retrogressive landslides in sensitive clays: a review and its applicability to Eastern Canada

Remoulding energy as a criterion in assessing retrogressive landslides in sensitive clays: a review and its applicability to Eastern Canada

Effect of initial failure geometry on the progress of a retrogressive seepage-induced landslide

Natural and man-made slopes can undergo a retrogressive landslide when subjected to seepage. Studying the mechanism of retrogressive landslides contributes greatly to the employment of effective mitigation approaches. A multi-stage limit equilibrium-based study was performed to explore how the geometry of initial failure affects the progress of a retrogressive, multiple-rotational landslide caused by seepage flow. Seepage-stability analyses were carried out on two silty sand slopes which were previously found to experience successive rotational failures upon raising the water table in centrifuge tests. Analyzed in prototype dimensions were the slope models with the height of 24 cm and inclinations of 45° (1V:1H) and 63.4° (2V:1H) tested at different centrifugal accelerations. According to the tests, the initial shallow failures were assumed to be circular initiating from the face and emerging from the toe of the slopes in the stability analyses. The impact of curvature and length of the initial failure surface (referred to as IFS) as well as the height of the scarp shaped at each failure episode were investigated. The results show that the landslide continues until the slope profile finds a stable curvature. For the landslides that occur in the 45° inclined slope, when the initial failure initiates at a higher elevation on the slope face, the landslide retrogresses further. In addition, with an increase in the length or curvature of IFS, the final retrogression distance decreases. Further, it was observed that the progress of landslides depends on the height of the scarp exposed at each failure episode.

Water-induced weakening retrogressive landslides: a study on the progressive failure process and formation mechanism of trailing edge fracture surfaces

Water-induced weakening retrogressive landslides: a study on the progressive failure process and formation mechanism of trailing edge fracture surfaces

Fiber optic monitoring of an anti-slide pile in a retrogressive landslide

Anti-slide piles are one of the most important reinforcement structures against landslides, and evaluating the working conditions is of great significance for landslide mitigation. The widely adopted analytical methods of pile internal forces include cantilever beam method and elastic foundation beam method. However, due to many assumptions involved in calculation, the analytical models cannot be fully applicable to complex site situations, e.g. landslides with multi-sliding surfaces and pile-soil interface separation as discussed herein. In view of this, the combination of distributed fiber optic sensing (DFOS) and strain-internal force conversion methods was proposed to evaluate the working conditions of an anti-sliding pile in a typical retrogressive landslide in the Three Gorges reservoir area, China. Brillouin optical time domain reflectometry (BOTDR) was utilized to monitor the strain distribution along the pile. Next, by analyzing the relative deformation between the pile and its adjacent inclinometer, the pile-soil interface separation was profiled. Finally, the internal forces of the anti-slide pile were derived based on the strain-internal force conversion method. According to the ratio of calculated internal forces to the design values, the working conditions of the anti-slide pile could be evaluated. The results demonstrated that the proposed method could reveal the deformation pattern of the anti-slide pile system, and can quantitatively evaluate its working conditions.

Progressive Formation of Retrogressive Landslide and the Lateral Length of Instability

Retrogressive landslide is caused by the lower rock mass sliding, so that the upper part loses support, is deformed, and starts to slide. In the process of highway construction, the incised slope often leads to retrogressive landslide, and the determination of the damage range of retrogressive landslide is of great significance for the control of the slope. Taking a highway retrogressive landslide in Hunan Province as the research object, the particle flow discrete element is used to numerically simulate the entire failure process of the slope. According to the complex geological conditions of the slope, the rock mass of each part of the slope model is divided, the displacement of key parts of the landslide is monitored, the whole failure process of the retrogressive landslide is simulated, and the lateral length of traction instability is calculated through the stability theory of the sliding pull-crack failure slope. The research shows that the incised slope is the root cause of the retrogressive landslide, and the rainfall is the direct cause. When the retrogressive landslide is treated in engineering practice, the lateral length of traction instability can be obtained according to the stability theory of the sliding pull-crack failure slope, to realize the accurate judgment of the traction failure range of the sliding body.

Experimental Study on Failure Mechanism and Mode of Fly-Ash Dam Slope Triggered by Rainfall Infiltration

The fly-ash dam is used to store the fly ash discharged from the thermal power plant. A fly-ash dam is a special slope built with fly ash, and rainfall infiltration is an important reason to induce the landslide of this kind of slope. In this paper, the laboratory tests of different slope ratios and initial seepage fields under rainfall were carried out, aimed at studying the failure mechanism, failure mode, triggering mechanism, and influence factors for the slope instability of the fly ash dam slope under rainfall infiltration. The results show that: (I) Three failure mechanisms were found in the tests: sliding failure, runoff erosion, and flow-slide failure. Due to the low density of fly ash, runoff erosion is more likely to occur under rainfall. Differently from clay slope, flow slide is an important failure mechanism of fly ash slope under rainfall. (II) Local erosion damages caused by runoff erosion and flow slide are the important triggering factors of the fly-ash dam slope failure under rainfall. (III) Three failure modes were observed in the test: the overall sliding failure of the slope, the retrogressive landslide caused by multi-stage local sliding, and the gradual erosion failure of the slope (caused by the combined action of runoff erosion and flow slide). (IV) The slope ratio has an important influence on the failure mode. With the decrease in slope ratio, the failure mode evolves from sliding failure to flow-slide failure and runoff erosion failure. The greater the slope ratio, the more obvious the sliding failure characteristics; the lower the slope rate, the greater the runoff erosion damage. The existence of an internal seepage field in the slope intensifies the occurrence of flow slide.

Successful emergency evacuation from a catastrophic loess landslide reactivated by the torrential rain in October 2021 in Tianshui, Ganusu, NW China

BackgroundAt the beginning of October 2021, the northwest China suffered torrential rainfall and several loess landslides were induced in Northwest China. This work presents a typical case (the Zhongzhai landslide) reactivated during this period in Niangniangba town, Tianshui, Gansu, China. The retrogressive failure was triggered again in the early morning of 5 October 2021 after a succession of torrential rain, and buried 2 houses and damaged another 2 houses. In this work, the geometric feature, soil composition, evolution history and failure process were preliminary described based on field investigation, history satellite images, and unmanned aerial vehicle photogrammetry.ResultsThe Zhongzhai landslide is mainly composed of Malan loess and the underlain silty slate, and the sliding surface is localized at their interface. The tensile cracks near the main scarp provide favorable channels for rainfall precipitation and the permeability difference between loess and silty slate enhances the liquefaction occurrence. The counter-tilt silty slate benefits water impoundment and exacerbates the flow-like slope failure. The lag effect is obvious in the Zhongzhai landslide due to the rainfall infiltration process and pore pressure generation.ConclusionsAlthough the Zhongzhai landslide is characterized with small scar and shallow sliding surface, it provides a classic case both for evolution history investigation of loess landslide and successful emergency evacuation. Based on our preliminary study, the unstable mass at the source of the Zhongzhai landslide with an area of approximately 3600 m2 that was slightly displaced in this event and has a high possibility to slide in future. Meanwhile, the Zhongzhai landslide is a retrogressive landslide and progressive failure occurred in the 2021 case, further analysis concerning the relationship among rainfall intensity, infiltration rate and pore water generation, as well as motion feature and runout prediction will be conducted.

Two-surface progressive failure mechanism and stability quantitative evaluation of water-induced weakening retrogressive landslides: case study for clay landslides, China

Two-surface progressive failure mechanism and stability quantitative evaluation of water-induced weakening retrogressive landslides: case study for clay landslides, China

The starting mechanism study on rainfall-induced sloop loose source in strong earthquake area

The 5.12 Wenchuan earthquake in 2008 led to a large number of loose deposits on the slope on both sides of the gully in the formation area. Under the triggering action of heavy rainfall, the previously unrecognized slope loose source in formation areas easily failed and started earlier than the overall start of the gully debris flow, which has practical significance for realizing the early warning of the gully debris flow starting. The special loose source conditions and postearthquake geological environment change the hydraulic mechanism of traditional debris flow start-up, which brings great difficulties to the monitoring and early warning of postearthquake debris flows. Therefore, based on hydraulics, on the premise of building a hydraulic model of groundwater level change of loose slope accumulation body, the characteristics and rules of groundwater level change are analyzed with the aid of hydraulic seepage theories, and the action characteristics of hydrodynamic pressure and hydrostatic pressure on the accumulation body are quantitatively studied. Based on field exploration data and average slope gradient, we divided the accumulation body in a reasonable manner; completed the sliding force, anti-sliding force and residual-sliding force mechanical expression and establishment; and performed a slope stability analysis. The research results show that the slope starting mode is divided into the thrust-type landslide and the retrogressive landslide mode of the subsection disintegration. The hydraulic deposit mechanism analytical results can also reverse the critical rainfall condition of slope failure. Finally, taking the Yindongzi gully in Dujiangyan as an example, the hydraulic mechanism of typical slope deposits in the formation area was analyzed and combined with the historical debris flow events in the study area to verify the physical simulation test, which was consistent with the field investigation results after the disaster.

How Can the Morphometric Characteristics and Failure Conditions of a Historic Gully Caused by Intense Rainfall Be Reconstructed?

In January 1980, during exceptional cyclonic rainfall, an atypical landslide, called déboulé, rapidly generated the permanent 700 m-long gully of the Ravine de l’Eglise on an inhabited plateau in Reunion Island (Indian Ocean). Retrieving the initial conditions that led to this historical process is both challenging and necessary for understanding the mechanism of gully incision and providing pointers for improving risk mitigation in relation to this phenomenon. In this study, we reconstruct the pre- and post-failure topographies using SFM (structure from motion) applied on archive aerial photographs. Based on the comparison of these digital elevation models, we estimate the volume of material eroded to be ca. 0.63 Mm3. Groundwater level increase, part of the triggering mechanism, is hindcast in the catchment of the gully using a lumped hydrological model. This model shows that in only a fortnight the groundwater level probably rose by 36 m, which could have caused a progressive increase in pore pressure and triggered formation of the gully by retrogressive landslides. We test this hypothesis by considering the pre-failure topography and the hindcast groundwater level in a deterministic model based on limit equilibrium equations to explore ground stability. The evolution of ground stability with a rise in the water table shows that the gully may have extended in a headward direction by retrogressive landslides. This is the first quantitative reconstruction of an exceptional historical event affecting the territory of Reunion Island. The methods used to investigate the Ravine de L’Eglise incision thus offer new complementary insights and challenges for understanding the mechanism and the temporality of gully formation.