MPM analysis of wetting-induced failure in collapsible loess slopes

Numerical simulation of rock avalanche dynamics using a coupled fragmentation-flow model: insights from the Liangshui Village landslide

Hazard assessment of landslide-induced impulse wave in high-dam reservoirs requires explicit quantification of the cascading processes from slope instability to wave impact. Previous methods often decouple the failure probabilities of slopes from hydrodynamic consequences, hardly considering the nonlinear amplification of cascading hazards. In this study, a physically-based hazard assessment framework from probability to consequence is established for the reservoir landslide in the upstream of the dam. The failure probabilities and models of slope under different reservoir levels are quantified via a Monte Carlo-based limit equilibrium approach. The failure models of slope are then simulated by the multiphase smoothed particle hydrodynamics (SPH) model, for considering landslide impact, wave evolution, and dam interaction. Reservoir level has a dual effect on hazard assessment via the failure probability of the slope and wave impact intensity. The secondary and localized failure of slopes under normal water level produces amplified wave heights due to enhanced impulse transfer and reduced energy dissipation, resulting in comparatively higher integrated risk. In contrast, other failure modes exhibit lower wave amplification despite comparable instability probabilities. Overall, this study provides a quantitative and physically-based framework for assessing landslide-induced wave hazard in high-dam reservoirs, supporting risk-informed safety management and hazard mitigation.

Extreme precipitation in the Eastern Himalaya is increasingly associated with coupled hillslope-floodplain hazards. This study examines the 17th-18th September 2020 rainfall event in Arunachal Pradesh initiating landslides and its downstream impacts in Assam, India, using multi-sensor satellite data and long-term rainfall records. Sentinel-2 imagery was used to map landslides and debris flows, Sentinel-1 SAR data to delineate flood extent, and IMD gridded rainfall (1996-2020) to analyse rainfall spell characteristics. The event triggered widespread slope failures, localized landslide damming, and a subsequent breach, generating sediment-laden flows that inundated ~ 100 km2 of the Dhemaji floodplain. A backscatter-derived Relative Flood Volume Index (RFVI) indicates spatial variability in inundation intensity, although it does not represent absolute flood volume. Rainfall analysis suggests that antecedent wetness from preceding spells preconditioned slopes, while peak daily rainfall (> 170mm day-1) initiated landsliding. Power-law scaling shows negligible dependence of intensity on duration (R2 ≈ 0.0004), whereas cumulative rainfall exhibits a stronger relationship with duration (R2 ≈ 0.54). These results indicate distinct roles of rainfall intensity and accumulation in controlling landslide initiation and downstream flooding, respectively, highlighting the importance of compound rainfall forcing in rapid hydrogeomorphic cascades.

Malappuram district, Kerala, ranked 7th among the most landslide-prone districts in India, according to the Landslide Atlas of India 2023 from the National Remote Sensing Centre (NRSC). The aim of this study is to map landslide susceptibility zones at the district level in Malappuram, Kerala, using GIS-based Weighted Overlay Analysis (WOA). The most commonly used factors for slope failure preparation were slope, elevation, aspect, curvature, land use/land cover, annual rainfall, distance to road, distance to river, soil depth, geology, LS factor, drainage density, Stream Power Index, and Topographic Wetness Index. The AHP technique has been applied to weight the 14 conditioning factors, and Pearson correlation has been used to assess the relation among these variables and between these variables and the landslide points. We have found that most variables are independent, with a maximum correlation coefficient of 0.72. Five respondents ranked 14 conditioning variables using a structured AHP matrix in a paired comparison. The Consistency Ratio obtained is 0.047, which is < 0.10. Slope was given the highest weightage (18%), followed by geology (13%) and annual rainfall (10%), which have the highest contributions to slope failures. The 14 conditioning factors were reclassified into five categories with values ranging from 1 to 5. The 14 classified factors were then combined to produce the landslide susceptibility map of the study area. The landslide susceptible maps were classified into low (39%, ~ 1384 km2), moderate (51%, ~ 1811 km2), and high landslide susceptibility zones (10%, ~ 355 km2). The high landslide susceptible areas are distributed over, in, and around the north-east highland of the district and are characterised by a combination of high slopes, charnockite geology, and high rainfall. The model has been validated using historical landslides point and random non-landslide points. The ratio of landslide and non-landslide points is 70:30 for training and testing, respectively. We obtained AUC values of 0.921 and 0.897 for training and testing, respectively. At the village level, the most affected villages due to landslides have been selected based on the percentage of land area falling within the highly landslide susceptible zones among all 135 revenue villages of the district. The most susceptible villages, in descending order, are Kerala Estate, Chokkad, Akampadam, Karulai, and Kurumbalangode. A detailed landslide susceptibility map of Malappuram district will enable scientists and authorities to plan mitigation actions, regulate construction activities in highly affected areas, and implement an early warning system at the local level.

We explore the mechanisms leading to the formation of the Disentis and Sedrun fans, which represent the largest and thickest Quaternary fan systems in the headwater area of the Alpine Rhine. These fans are several km 2 in size and underlain by tens of meters-thick, non-consolidated breccias. The sedimentary fabric of these deposits is matrix-supported, suggesting deposition by debris flows. In addition, concentrations of in-situ 10 Be in detrital quartz minerals that are embedded in these deposits reveal high paleo-denudation rates of nearly 2 mm yr −1 . These rates are substantially higher than the mean denudation rates <1 mm yr −1 that we measured for the headwaters of the Alpine Rhine. This confirms the view where the fan deposits at Disentis and Sedrun record a time interval when material supply occurred through sedimentary pulses. In addition, regional studies reveal that the construction of the investigated fan systems postdates the formation of moraines that were dated to the Egesen Stadial during the Younger Dryas. We thus propose that the accumulation of the sedimentary material at Disentis and Sedrun most likely occurred during the same epoch as the Flims rock avalanche. This was the largest mass failure event in the European Alps and resulted in the accumulation of tens of meter-thick, non-consolidated breccias on the valley floor some kilometers farther downstream. The result was the formation of a lake upstream of the rock avalanche deposits and the rise of the base level on the valley floor. We thus envisage an interpretation where the higher base level together with the release of large volumes of sediment caused the construction of the fans at Disentis and Sedrun. Once the lake was breached and the hillslope sediment reservoirs were exhausted, the Alpine Rhine started to incise into the previously deposited material, thereby leaving distinct cut levels at the toes of these fans. We acknowledge that we lack precise numerical ages for the time period when the fan systems at Disentis and Sedrun were constructed. Nevertheless, based on the available information, we conclude that the fan sediments in Alpine valleys serve as suitable archives for improving our understanding of the environmental response to climate warming. • We present 10Be-based paleo-denudation rates recorded by terrace deposits in the Alpine Rhine. • The results show that these sediments, which accumulated after the change from the cold period of Egesen Stadial to the Boreal warm period, record the occurrence of sedimentary pulses. • The accumulation of the sedimentary material at Disentis and Sedrun most likely occurred at the same time as the Flims rock avalanche, the largest mass failure event in the European Alps. • Based on our research, we consider that terrace sediments and breccia deposits in Alpine valleys as suitable archives for improving our understanding of the environmental response to climate warming.

Rainfall-Induced Slope Failure in Bukit Barisan

Satellite-derived seasonal fluctuations in surface displacement and soil moisture: Implications for landslide activity

ABSTRACT The prediction of rainfall-induced shallow landslides depends not only on rainfall characteristics but also critically on geoenvironmental conditions. However, current empirical rainfall thresholds are typically developed neglecting spatial variations in geoenvironmental settings and are applied uniformly across heterogeneous terrain, limiting their predictive capability. To this end, we propose a novel framework that adaptively partitions the study area into sub-regions where homogeneous geoenvironmental conditions give rise to consistent landslide patterns, and derives localised, pattern-specific rainfall thresholds. The framework first evaluates geoenvironmental conditions at the slope unit scale and leverages Gaussian mixture modelling to segment the area based on similarity. For each sub-region, the separability between triggering and non-triggering rainfall events is quantified to assess the consistency of rainfall-landslide response patterns, validating the segmentation. Guided by this assessment, an adaptive procedure optimises the predictors and segment number, yielding sub-regions exhibiting consistent landslide patterns and associated probabilistic rainfall thresholds. The framework is applied in Zhuji, China. Results show that it improves the prediction of historical landslides, increasing the AUC from 0.936 to 0.966 over a 16-year rainfall record. A real-time early-warning case further demonstrates a reduction in false alarms by over 20% while maintaining a high hit rate, outperforming conventional thresholds.

ABSTRACT Physically based models like TRIGRS are utilized to assess regional shallow landslide hazards. However, TRIGRS accuracy is limited by spatial heterogeneity in geotechnical properties, especially colluvial thickness and shear strength. To address this limitation, we propose an enhanced Physico-Data TRIGRS model. First, a physico-data coupled soil zoning optimization integrating frequency ratio analysis and Random Forest (RF)-based dominant factor identification for improved soil zoning. Then, a physically constrained estimation of colluvial thickness by combining field data with an improved slope-thickness function, enhancing the model's applicability in complex terrains. Finally, Monte Carlo simulation is incorporated to represent the spatial variability of shear strength parameters and to transform deterministic factors of safety into slope failure probabilities under four rainfall scenarios: no rainfall, 10-, 50- and 100-year return periods. Pingyang County is selected as a case study. Results indicate that the proposed model improves the accuracy of landslide hazard by 10%, increasing the AUC from 0.708 to 0.843. Monte Carlo simulation effectively captures parameter uncertainty, enabling robust dynamic probabilistic hazard evaluation under different rainfall conditions. Overall, the proposed framework improves both the physical interpretability and predictive precision of TRIGRS, providing a more flexible and accurate approach for landslide hazard assessment.

As sudden-onset geological disasters, the dynamic behavior of rock avalanches is significantly influenced by the size of the debris particles formed during rock mass disintegration. In this study, 59 sets of laboratory model tests were conducted to systematically investigate the effects of particle size on the characteristic parameters of landquake signals (Arias intensity, mean of the envelope, mean frequency, and vibration energy), and to explore the roles of release height and particle mixing. The results indicate that as particle size increases, the intensity-related parameters (Arias intensity, mean of the envelope, and vibration energy) exhibit exponential growth, while the mean frequency decreases exponentially. This suggests that larger particles release higher energy at lower frequencies-a particle size effect that is independent of release height and thus of universal validity. Granular flows with mixed particle sizes display an inverse grading characteristic during movement, causing the landquake signal characteristics to be biased toward those of the finer particles. This confirms that the landquake signal is primarily generated by the interaction between the lowermost layer of particles and the base plate. These findings provide a theoretical foundation for inverting rock avalanche particle size characteristics from landquake signals and for disaster early warning.

Landslides pose substantial hazards in karst regions such as Bijie. However, the conventional subsidence metrics fail to represent the hydro-mechanical processes triggering slope failure. To address this limitation, the Skeleton Elastic Storage Coefficient (SKE) is proposed as a physically interpretable indicator. SKE was derived by integrating SBAS-InSAR deformation with GRACE-FO/GLDAS water storage data. To evaluate the performance of the SKE, a systematic comparison of 24 model-feature-sampling combinations was conducted, including traditional machine learning (SVM, RF, XGBoost) and deep learning models (MLP, LSTM, Transformer), two feature sets (SKE vs. subsidence), and two negative sampling schemes. The F1-score and AUC were used for evaluation. The results show that the SKE combinations consistently outperformed the subsidence metrics combinations, increasing the best F1-score by 4.50% and AUC by 3.61%. The best performance was achieved by the combination of Transformer with SKE and terrain-factor-filtered negatives (F1-score = 0.9498; AUC = 0.9905), reflecting its ability to capture long-range spatial dependencies. High-susceptibility zones concentrate along steep slopes and river corridors in Nayong, Hezhang, and Qixingguan. By linking surface deformation to subsurface hydrogeological processes, the SKE provides a more sensitive and interpretable basis for landslide susceptibility mapping than traditional deformation-only approaches.

ABSTRACT Slope failures are a significant concern in geotechnical engineering, often resulting in catastrophic consequences for infrastructure and human safety. Real-time monitoring and early warning systems are critical to mitigating these risks. This research focuses on the development of a Smart Wired Module (SWM) designed for real-time slope failure tracking. The proposed system integrates soil moisture, vibration, accelerometer, force-sensitive resistor and temperature sensors, wired communication technologies, and data analytics to provide accurate and timely information on slope stability. Design and develop a SWM will help to monitor the present condition of the soil slope, which will ultimately help to take the preventive measures to avoid slope failure. It will help to improve the efficiency of real-time data analysis for slope failure monitoring systems. The study reveals an inverse relationship between water flow rate and the time to detect variations: at 0.023 L/s, changes appeared in 280 s; at 0.05 L/s, in 148 s; at 0.027 L/s, in 210 s; and at 0.067 L/s, in just 84 s. This demonstrates that higher discharge rates result in shorter detection times.

The Numerical Manifold Method (NMM) introduces two independent cover systems-mathematical and physical-allowing discontinuities associated with crack propagation to be represented in a natural manner. To clarify the instability pattern and crack evolution of stratified rock slopes under top loading, this study implements a quadrilateral NMM framework incorporating the LT criterion, formulated from the Mohr-Coulomb strength theory, together with a damage factor. The LT criterion is used to determine the onset and propagation of cracks, while the damage factor serves to distinguish crack types. The proposed framework is first examined through a Brazilian splitting test, which confirms its capability to resolve crack development in a transparent and physically consistent way. It is then applied to systematically investigate the failure pattern and crack propagation characteristics of stratified slopes containing cracks of different inclinations or randomly distributed bedding cracks under overload conditions. The results show that, as crack inclination increases, the failure pattern of top-loaded stratified slopes shifts from shallow bedding-parallel shear failure to deep sliding-tensile composite failure. For slopes with randomly distributed bedding cracks, progressive failure follows a sequence of dispersed crack initiation, coalescence, penetration, and subsequent layered sliding-splitting. The proposed method captures the complex discontinuous failure process with high fidelity, demonstrating its effectiveness for stability analysis of stratified slopes with inherent cracks. The findings provide a theoretical basis for hazard assessment and protective design of top-loaded stratified rock slopes.

Nepal’s Himalayan terrain, characterized by extreme elevational gradients and heterogeneous lithology, presents region-specific challenges for slope stability and infrastructure resilience. This study evaluates the geotechnical properties of soils from five climatically distinct regions—Kathmandu Valley (subtropical urban basin), Pokhara (humid alluvial valley), Chitwan (forested sub-Himalayan tract), Mustang (arid trans-Himalayan zone), and Terai Plains (tropical lowland)—to establish predictive relationships between soil behaviour, environmental factors, and slope failure mechanisms. Laboratory analyses, including triaxial shear testing under unsaturated conditions and advanced permeability profiling were paired with limit equilibrium stability modelling. Results demonstrate that moisture content (R² = 0.87, p &lt; 0.01) and clay mineralogy dominate stability outcomes, with safety factors (FoS) ranging from 0.8 (Terai) to 2.5 (Mustang). A novel regional classification framework is proposed to guide slope management in Nepal’s rapidly developing landscapes.

Slow gravitational failures of mountain peaks and ridges are poorly understood. Herein, we report on 50 years of studies at a slowly spreading castellate ridge at Bald Eagle ridge in the Sawatch Range in central Colorado. The orientations of geomorphic-structural features indicate that the fractured Precambrian granitic rock underlying the ridge has extended and spread northwestward toward the formerly glacier-covered Busk Creek valley. Results from surveying, field-based geomorphic-structural mapping using lidar, rock mass quality measurements, a passive seismic survey, and satellite radar provide a major update to research started by U.S. Geological Survey researchers in the 1970s and 1980s. New insights include a recognition that the entire ridge has slowly moved by concurrent sliding along an inferred northwest dipping, compound basal-slip surface (or zone), and through the formation of multiple grabens by normal faulting and flexural toppling along sets of pre-existing fractures that dip moderately (~45°) to the southeast. We were unable to distinguish the presence of a sudden and strong contrast in seismic velocity across the inferred slip surface. Movement during the 50-year study period has been episodic and gradually decreasing, in correspondence with decreasing cumulative annual precipitation and increasing mean annual air temperatures. The fastest moving area, just upslope from the glacier trimline, had an average horizontal velocity of 3 – 4 mm/yr. Evidence suggests that movement started as a paraglacial response mechanism, but because of the site’s proximity to the Rio Grande Rift, we cannot exclude earthquake shaking as a mechanism for initiation or enhancement of slope movement. An estimate of longer-term horizontal movement from the exposed basal-slip surface at the uphill side of the ridgetop graben is ~1.1 mm/yr for the 13 – 14 ky post-glacial period. Broad implications of our work are that: (1) long-term measurements (decades or longer) of slope movement can add insights into how sackungen form and evolve through time; (2) the identification of thrust faults and toes in zones of compression near valley bottoms can be crucial for interpreting sackung failure mechanisms, and (3) the use of passive-seismic techniques to identify the depth to a slip surface may not be successful in granitic terrain dominated by planar fractures and subtle changes in rock-mass characteristics. • A chronicle of 50 years of studies at a slowly spreading castellate ridge in Colorado. • Results from surveying, mapping, rock mass quality, a seismic survey, and InSAR. • Episodic movement decreased with decreasing precipitation and increasing temperatures. • Ridge is failing by concurrent sliding and toppling along pre-existing fractures.

Multi-parameter seismic metrics for detection and classification of rock and ice-rock avalanches

Under continuous dynamic compaction and vibration, slope instability and failure in the Loess Plateau region may occur. Many previous studies focused on the overall stability of the slope, but the damage mechanism of the loess slope seldom discussed. To analyze the cause and degree of loess slope damage under dynamic compaction, this paper proposes the basis of judging slope soil damage by analyzing its porosity–resistivity relationship. Unlike previous studies focusing on postfailure analysis or overall stability, this study proposes a nondestructive, in situ method to quantify progressive internal damage during the compaction process itself. Combined with the field test, the soil mass of two different loess slopes in the field was tested by the multielectrode resistivity method, and the change in internal resistivity of slope soil before and after dynamic compaction was analyzed. The results revealed that the damage degree of different parts of a slope caused by different tamping positions is different. The resistivity of slope soil can reflect the degree of soil damage and deterioration. The resistivity of some measuring points decreases in the early period of dynamic compaction, because the fine particles in the soil gradually fill the pore space under vibration, and the density of soil particles increases. Under continuous dynamic compaction, the resistivity of the particles inside the slope increases gradually, and the damage and deterioration degree of the soil is greater than zero. This level of deterioration indicates significant structural weakening that may precipitate failure under subsequent environmental loading. According to the test results, the maximum damage and deterioration degree of slope soil can reach 27%. The pore volume of the soil increases, the cohesiveness weakens, the cement between the soil particles gradually breaks, and the damage in the slope is intensified, which further reduces the stability of the slope soil. Compared to intrusive methods, the high-density electrical method provides a rapid, spatial assessment of subsurface damage, offering real-time guidance for optimizing construction sequencing and mitigating slope instability.

Deriving and assessing forest gap thresholds to prevent shallow landslides in Swiss mountain forests

Mechanisms of rainfall-induced shallow landslides regulated by hydrological subsurface structures: Cases in granite and granodiorite areas in Northern Abukuma Mountains, Japan