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Herein, fast fracture initiation in glacier ice is modeled using a Material Point Method and a simplified constitutive law describing tensile strain softening. Relying on a simple configuration where ice flows over a vertical step, crevasse patterns emerge and are consistent with previous observations reported in the literature. The model's few parameters allows identification of a single dimensionless number controlling fracture spacing and depth. This scaling law delineates two regimes. In the first one, ice thickness does not play a role and only ice tensile strength controls the spacing, giving rise to numerous surface crevasses, as observed in crevasse fields. In this regime, scaling can recover classical values for ice tensile strength from macroscopic field observations. The second regime, governed by ice bending, produces large‐scale, deep fractures resembling serac falls or calving events. Plain Language Summary: In ice sheets and alpine glaciers, fast‐flowing sections are often characterized by crevasse fields that play a significant role in the cryo‐hydrologic system by facilitating meltwater flow, enhancing basal sliding, weakening the ice, and impacting glacier thermodynamics. Modeling these fractures at the glacier scale remains challenging and often necessitates integrating diverse models which hinders the straightforward consideration of physical issues associated with crevasse fields on a large scale. Here, a new numerical framework allows us to conduct field‐scale experiments and paves the way for a scaling law to elucidate the macroscopic factors influencing fracture fields and to easily incorporate crevasse depth and spacing into large‐scale models. A newly discovered scaling law highlights the transition between a mechanical behavior where the regular crevasse spacing is unaffected by geometry to a regime where geometry plays a significant role, particularly in large‐scale fracture processes like glacier calving. While the numerical experiments in this paper focus on glaciers, the model and conceptual framework is versatile and can address the mechanical behavior of fractures in broader geophysical contexts such as snow, rock or ice avalanches, tectonics and landslides. Key Points: Fractures in glacier flow are modeled using material point method with elastoplasticity and tensile strain softeningA dimensional analysis reveals a key dimensionless number characterizing two different regimes of fast fractureOne regime predicts acknowledged ice tensile strength from field observations and characterizes the regular crevasse spacing [ABSTRACT FROM AUTHOR]

We investigated the paraglacial evolution and permafrost degradation of Val Viola (Upper Valtellina, Central Italian Alps) through a geomorphologic survey, cosmogenic dating, Schmidt's Hammer, and surface roughness measurements. Our results reveal that the previously mapped Val Viola rock avalanche is probably derived by three different events that occurred 7.7 ± 0.2 ka (Orthogneiss_ 1), 7.0 ± 0.2 ka (Paragneiss), and 5.0 ± 0.3 ka (Orthogneiss_2). Because the main valley bottom has been ice free since at least 12.6 ka, it is unlikely that the triggering factor of these events was the debutressing stress caused by the melting of local valley glaciers. Therefore, permafrost that formed in this area down to 2525 m a.s.l. at 9.3–8 ka and degraded successively between 7.8 and 6.5 ka was likely the main triggering factor of the first two rock avalanche events, as well as for the third event that happened during the warm and wet period of the Holocene Thermal Maximum around 5 ka. [ABSTRACT FROM AUTHOR]

The ability to predict the mobility of rock avalanches is necessary when designing strategies to mitigate the risks they pose. A popular mobility indicator of the flow front is the Heim's apparent friction coefficient μ H . In the field, μ H shows a decrease in value as flow volume V increases. But this correlation has been a mystery as to whether it is due to a causal relationship between V and mobility since: (1) field data of μ H do not collapse onto a single curve because typically widely scattered and (2) laboratory experiments have shown an opposite volume effect on the center of mass mobility of miniature flows. My numerical simulations confirm for the first time the existence of a functional relationship of scaling parameters where μ H decreases as V increases in unsteady and nonuniform 3D flows. Data scatter is caused by μ H that is affected by numerous other variables besides V. The interplay of these variables produces different granular regimes with opposite volume effects. In particular, μ H decreases as V increases in the regime characterized by a relatively rough subsurface. The relationship holds for large-scale flows that, like rock avalanches, consist of a very large number of fine clasts traveling in wide channels. In these dense flows, flow front mobility increases as flow volume increases, as channel width increases, as grain size decreases, as basal friction decreases and as flow scale increases. Larger-scale flows are more mobile because they have larger Froude number values. [ABSTRACT FROM AUTHOR]

We examined the possible factors affecting the spatial distribution of very low frequency earthquakes and tremors in the shallow megathrust of Nankai Trough (<30 km) using a dense network of prestack depth migrated profiles at the frontal wedge. Geometrical parameters examined were decollement roughness, taper angle, and underthrust thickness. Physical properties such as effective basal friction (μb) and pore pressure ratio (λ*) were calculated from the taper angle and p‐wave velocity. Regions of low λ* (0.39 ± 0.08) and smooth decollement showed no slow earthquake activity. In contrast, high activity of slow earthquakes was observed in areas with a rough decollement due to the presence of subducted seamounts or bathymetric highs. The low taper angle (3.8°) off Muroto where slow earthquakes also occur translates to a wide zone of low μb (0.21 ± 0.06) and high λ* (0.66 ± 0.06). However, our results also show that slow earthquakes don't always occur in areas with high λ*. Plain Language Summary: Slow earthquakes such as very low frequency earthquakes and tremors are different than typical earthquakes because they occur longer and can last for more than several days. They have been reported in numerous subduction zones around the world and the study of slow earthquakes has recently gained attention because they have been suggested as precursors to larger earthquakes albeit on rare occasions. Slow earthquakes show a clustered distribution in the Nankai Trough. We used a dense network of seismic reflection data acquired at the shallow portion of the Nankai Trough to examine why some areas have high activity and some areas have no activity. Our results showed that areas with no slow earthquake activity have a smooth decollement and low pore fluid pressure. On the other hand, areas with high slow earthquake activity have a rough decollement. The occurrence of slow earthquakes has been typically associated with high pore fluid pressure because it allows the two slabs of rock to slide easier. However, our results suggest that high pore fluid pressure may not always be a prerequisite for slow earthquakes to occur. Key Points: A smooth decollement due to absence of subducted seamounts or bathymetric highs, and low pore fluid pressure results in a slow earthquake gapSlow earthquakes don't always occur in areas of high pore pressure but in combination with other variables like decollement roughnessThe low taper angle off Muroto indicates a wide zone of low friction and high pore pressure possibly associated with subducted seamounts [ABSTRACT FROM AUTHOR]

Mountain tunnels portal often have to pass through slope terrain unavoidably, thus forming a shallow buried bias tunnel. During the construction of shallow buried bias tunnel, disasters such as slope sliding and tunnel collapse frequently occur. The failure mode of surrounding rock obtained by current research is based on the limit equilibrium theory, which cannot reflect the progressive failure characteristics of the surrounding rock of shallow buried bias tunnel. In order to reveal the failure mechanism of the gradual instability of surrounding rock of shallow buried bias tunnel, the problem of gradual failure of the surrounding rock is reduced to an elastic–plastic analysis problem for surrounding rock considering the strain-softening characteristics. Based on the elastic–plastic analysis of the failure process of shallow buried bias tunnel, MATLAB was used to compile a program to read the finite-difference calculation result file, extract the effective information such as shear strain and tensile strain at the center point of each unit, and establish the analysis method of the progressive failure mode of shallow buried bias tunnel. The reliability of the method proposed was verified by comparing the failure process of the model test with the development process of shear strain increment. Under the condition of no support, the formation mechanism of failure plane of surrounding rock on both sides of shallow buried bias tunnel is different. The shallow buried side is the shear failure plane formed by the collapse of surrounding rock, while the deep buried side of the tunnel is the shear failure plane formed by the collapse of surrounding rock and slope sliding. Under the conditions of excavation and support, the failure plane of the shallow buried bias tunnel can be divided into three parts according to the formation sequence and reasons. The part I is the failure plane, which is formed by active shear under the influence of tunnel excavation. The part II is the failure plane formed by tensile crack of slope top. The part III is the failure plane formed by passive shear under the push of the soil in the upper part of the slope. [ABSTRACT FROM AUTHOR]

Surface deformation caused by an earthquake is very important to study for a better understanding of the development of geological structures and seismic hazards in an active tectonic area. In this study, we estimated the surface deformation due to an earthquake along an active blind fault using Sentinel-1 SAR data. On 24 September 2019, an earthquake with 5.6 Mw and 10 km depth stroke near Mirpur, Pakistan. The Mirpur area was highly affected by this earthquake with a huge collapse and the death of 34 people. This study aims to estimate the surface deformation associated with this earthquake in Mirpur and adjacent areas. The interferometric synthetic aperture radar (InSAR) technique was applied to study earthquake-induced surface motion. InSAR data consisting of nine Sentinel-1A SAR images from 11 August 2019 to 22 October 2019 was used to investigate the pre-, co- and post-seismic deformation trends. Time series investigation revealed that there was no significant deformation in the pre-seismic time. In the co-seismic time, strong displacement was observed and in post-seismic results, small displacements were seen due to 4.4 and 3.2 Mw aftershocks. Burst overlap interferometry and offset-tracking analysis were used for more sensitive measurements in the along-track direction. Comprehensive 3D displacement was mapped with the combination of LOS and along-track offset deformation. The major outcome of our results was the confirmation of the existence of a previously unpublished blind fault in Mirpur. Previously, this fault line was triggered during the 2005 earthquake and then it was activated on 24 September 2019. Additionally, we presented the co-seismically induced rockslides and some secondary faulting evidence, most of which occurred along or close to the pre-existing blind faults. The study area already faces many problems due to natural hazards where additional surface deformations, particularly because of the earthquake with activated blind fault, have increased its vulnerability. [ABSTRACT FROM AUTHOR]

Clay‐rich rocks are integral to subduction zone dynamics and of practical importance, for example, as barriers in nuclear waste and CO2 repositories. While the effects of swelling strain on the self‐sealing capabilities of these rocks are relatively well‐established, the implications of polar fluids interacting with charged clay particles on the frictional behavior, and the role of swelling stress in initiating slip in critically stressed faults, remain ambiguous. To address these uncertainties, we conducted triaxial friction experiments using saw‐cut samples, with the upper half composed of Opalinus claystone (OPA) and the lower half of Berea sandstone (BER). The frictional strength of the non‐wetted OPA‐BER interface was estimated based on experiments at confining pressures of 4–25 MPa and constant axial loading rate (0.1 mm/min). Fluid injection friction experiments were performed using decane (non‐polar fluid) or deionized water (polar fluid) at 10 and 25 MPa confining pressures and constant piston displacement control. Macroscopic mechanical data were complemented by distributed strain sensing on the sample surface. Compared to decane, the frictional strength of the OPA‐BER interface tended to decrease when injecting water, which is attributed to phyllosilicate lubrication and the transition of the OPA from a solid rock to an incohesive mud near the saw‐cut surface. When injecting water, slip was initiated during initial hydration of the OPA‐BER interface, although the apparent stress state was below the yield stress. To explain this behavior, we propose that the swelling stress is a crucial factor that should be integrated into the effective stress model. Plain Language Summary: Clay‐rich rocks are important in subduction zones and for practical applications like nuclear waste containment and CO2 storage. A unique property of clay is the ability to swell by incorporation of water. If swelling deformation is constrained, swelling stress can develop. While the enhanced sealing ability of fractures due to swelling is well‐known, the effect of water‐clay interactions on friction and the contribution of swelling stress to fault reactivation remain unclear. We studied these effects with laboratory experiments where Opalinus claystone (OPA) was sheared against Berea sandstone. First, using experiments without fluids, we established that our set‐up is representative for claystones. In further experiments, we injected a non‐polar fluid that does not interact with clay. We compared these with experiments where we injected water, which is polar and therefore interacts with the charged clay. The frictional strength tended to decrease when injecting water, likely due to water acting as a lubricant and transforming OPA into a slurry. Surprisingly, movement along the interface started although the applied stress was below the threshold. We explain this by the contribution of swelling stress to the overall stress state. These findings improve our understanding of clay‐rich rock behavior in nature and practical applications. Key Points: The frictional strength of clay‐rich rocks tends to decrease in the presence of a polar fluid compared to a non‐polar fluid or no fluidFrictional slip in clay‐rich rocks may be initiated although the apparent effective stress state is below the yield stressH2O‐clay interactions may contribute to reactivation of faults by altering the mechanical properties and the build‐up of swelling stresses [ABSTRACT FROM AUTHOR]

The forest could be a protective structure to reduce rock avalanches in the Sichuan-Tibet Mountains. When rocks propagate down a forested slope and hit trees, they are blocked, modified in trajectory, slowed down, and deposited, which weakens their destructive effect directly on the downstream. To better understand the protective effect of forests against rock avalanches, a novel material point method (MPM) introducing two contact models describes the rock avalanches' movement on slope and interaction with trees, respectively. Carry out simulations on an idealized scenario of rock avalanches to conduct extensive parametric studies, which give the shape, volume, thickness, and runup height of rock accumulations, showing how shapes, species, and layout of trees have vital effects on blocking the rock avalanches. Finally, an optimal green protective structure for a vegetation-free slope in a 3D valley is given, and the blocking-baffle mechanism of vegetation to rock avalanches on mountains is illustrated clearly through numerical calculations. [ABSTRACT FROM AUTHOR]

The seismic sliding of rock masses is an important phenomenon that is widely involved in earthquake geological hazards. Practical seismic sliding is a three‐dimensional problem, namely, the seismic loads may act in any direction and the rock masses may move in an arbitrary direction relative to the sliding plane. In the present work, the functions of two different seismic loading methods, that is, loading as body force time histories to the sliders or as displacement time histories to the base, are added to the program of the three‐dimensional discontinuous deformation analysis (3D‐DDA) method that is based on the contact theory to study the seismic sliding of rock blocks. The theoretical solutions of single‐block sliding on an incline under the two seismic loading methods are derived. By comparing the 3D‐DDA results of single‐block seismic sliding with the corresponding theoretical results, and comparing the 3D‐DDA results of seismic sliding of three‐stacked‐blocks under the two seismic loading methods, the correctness of 3D‐DDA for seismic sliding simulations is validated. Thereafter, the influence of three‐dimensional seismic components on single‐block sliding, and the movement of block groups under different seismic load conditions are investigated by 3D‐DDA simulations, which indicate the importance to consider rock mass seismic sliding as a three‐dimensional problem and the capability of 3D‐DDA for its analysis. This work builds a meaningful basis for the further numerical simulation study on the earthquake‐induced rock mass movements by 3D‐DDA. [ABSTRACT FROM AUTHOR]

The Texas Creek rock avalanche is a prehistoric deposit in the Fraser River Canyon, 17 km south of Lillooet, southwestern British Columbia, Canada. Original mapping suggested that the debris consisted of two landslides: a 45 Mm3 event deposited after the Mazama tephra but before about 2 ka ago, and a 7.2 Mm3 event about 1.1 ka ago. The proposed timing of the younger landslide was correlated with a decline in the First Nations population and was proposed as an agent of cultural collapse driven by its impact on salmon returns vital to the population's sustenance. We provide six surface exposure ages using 10Be from boulder tops, with three samples from each surface that were originally posited to be older and younger debris. The six samples yielded similar ages suggesting the landslide deposit represents a single event with an average age of 2.28 ± 0.19 (2σ external error) ka before 1950 AD. Evidently, the landslide played no role in the cultural collapse. Fraser River Holocene incision rates, estimated pre- and post-landslide are between 13 and 24 mm/yr, consistent with previous estimates for the mid-Fraser River region. Landslide timing is coincident with the explosive eruption of Mount Meager, 120 km to the northwest, and with a possible landslide at Mystery Creek 85 km to the west and 65 km south of Mount Meager. The landslide may have been seismically triggered, but attribution is speculative. [ABSTRACT FROM AUTHOR]

Studies show that weak structural faces in jointed rock masses can easily result in large deformations in tunnels, which significantly affect the safety and stability of supporting structures. To address this issue, the present study considers the Linpanshan Tunnel in a layered joint stratum as the case study, focusing on joint inclination and joint spacing. Numerical simulations and field monitoring were conducted to investigate the displacement and stress evolution in the surrounding rock and tunnel structure under various attitudes of the jointed rock mass. The results indicate that the stability of surrounding rock and tunnel structures is more influenced by joint inclination than joint spacing. The maximum surrounding rock displacement reaches its maximum value, measuring 1.889 mm, for the joint attitude of 0° + 0.5 m; the maximum shear stress occurs at the right arch foot of the lining and reaches 11.44 kPa under the 60° + 1.5 m joint attitude. When joint inclination varies within the range of 0–60°, the rock formations slide significantly along the structural faces, leading to higher tensile stresses on the arch apex, arch spandrels, and arch feet of the lining. Consequently, the tunnel structure becomes prone to asymmetric deformation and cracking. The present study analyses the deformation mechanism in surrounding rock and the cracking of lining structures in the 55° joint formation by incorporating the characteristics of the lining cracks in the Linpanshan Tunnel. As a reinforcement measure, the installation of additional anchors in the weak zone of the lining was proposed. Meanwhile, the performance of the proposed technique was verified through field monitoring data. The research results provide a technical reference for large deformation control in jointed rock masses. [ABSTRACT FROM AUTHOR]

The anti-dip bedding rock slopes have threatened global infrastructure construction and urban expansion seriously. Taking the Guang'an Village rockslide as an example, this paper firstly studied the deformation characteristics of the rockslide with anti-dip bedding structure based on in-situ investigation and monitoring, and then the relevant influencing factors were summarized. On this basis, a new evolution model of continuous-pushing-section pressing locked-section and the instability mechanism of the rock slope were proposed. Finally, the applicability of the model and the deformation tendency of the rock slope were further discussed. A catastrophic sliding event has once occurred in the Guang'an Village rockslide in 2017, after which the deformation of the potential source area III (PSA-III) was accelerating. The presence of the sliding-prone geological structure provides the basic conditions for the deformation of the rock slope and the development of the sliding zone. Rainfall is the major external trigger that promotes the deformation. As the sliding zone extends forward, the overlying deformation body will keep on pushing against the preceding rock mass, which will contribute to the forward extension of the sliding zone as well. When the final locked section is crushed, the rock slope will lose balance. According to the observation in the field, the PSA-III is in the late stage of the deformation-increasing phase currently. This study can provide a reference for the analysis of failure mechanism and the design of monitoring and mitigation of other large anti-dip bedding rock slides. [ABSTRACT FROM AUTHOR]

Domain-specific mesoscale landslide susceptibility mapping (LSM) and risk assessment was carried out along National Highway (NH44) of Jammu and Kashmir, Western Himalaya. The methodology proposed in this study broadly consist three stages including the (1) pre-field component for preliminary thematic map preparation, (2) field component for ground data collection and validation, and (3) post-field component for data updating, processing, and integration. High-resolution Earth Observation (EO) images (Cartosat-DEM-10 m, Cartosat-1 PAN image-2.5 m, Google Earth image-4 m) and other ancillary datasets (SoI topographic, and geological maps) supplemented with extensive field survey were used to generate main causative geo-factor maps for analysis. Slope facet used as a basic unit of mapping preliminarily classified the area into rocky (65.7%) and overburden covered (34.2%) slopes, respectively. An updated inventory of 117 landslide incidence zones comprising 50 debris slides, 34 rockfalls, 20 rock slides, 5 rock topples, 2 debris flows and 6 old slide zones was generated. Depending upon the type and nature of material involved in the slope failure, facets were further classified into debris slide domain, rock slide domain, cut-slope domain and no slide domain for detailed analysis and treatment. The geo-factor maps were weighted using knowledge driven ratings for each factor class as per domain-specific facet using Landslide Susceptibility Estimated Rating (LSER) scheme. The sum up of LSER values for individual causative factors calculated the Total Estimated Susceptibility Values (TESV) that classified the entire area into low, moderate and high susceptibility classes covering an area of 39.8%, 40.0% and 20.1%, respectively. The validation of LSM against high-resolution landslide inventory indicated a higher level of performance of the adopted methodology for the study area. About 80.0% and 10.4% of slope failure incidences coincided perfectly well with high and moderate susceptibility classes. Moreover, the human settlements, agriculture land, roads and bridges, stone crushers and other strategic civil structures (i.e., tunnels, electric line poles and towers, etc.) are the main elements at high risk in the area. [ABSTRACT FROM AUTHOR]

Rockfall and rock avalanches are common in steep terrain on Earth and potentially on other planetary bodies such as the Moon and Mars. Since impacting rocks can damage exposed bedrock as they roll and bounce downhill, rockfall might be an important erosive agent in steep landscapes, even in the absence of water. We developed a new theory for rockfall‐driven bedrock abrasion using the ballistic trajectories of rocks transported under gravity. We calibrated this theory using laboratory experiments of rockfall over an inclined bedrock simulant. Both the experiments and the model demonstrate that bedrock hillslopes can be abraded by dry rockfall, even at gradients below the angle of repose, depending on the bedrock roughness. Feedback between abrasion and topographic steering of rockfall can produce channel‐like forms, such as bedrock chutes, in the absence of water. Particle size has a dominant influence on abrasion rates and runout distances, while the hillslope angle has a comparatively minor influence. Rockfall transport is sensitive to bedrock roughness; terrain with high friction angles can trap rocks creating patches of rock cover that affect subsequent rockfall pathways. Our results suggest that dry rockfall can play an important role in eroding and channelizing steep, rocky terrain on Earth and other planets, such as crater degradation on the Moon and Mars. Plain Language Summary: Rockfall is common on Earth and other planets. Falling rocks bounce down rocky slopes and likely also erode them. However, it has not been explored how erosive this process is, nor what landforms it might generate. We developed a numerical model for this erosion process and calibrated it with experiments of dry grains hopping down an inclined erodible surface. Both experiments and modeling showed that bedrock erosion from rockfall can occur even on relatively low‐grade hills. Small hollows were carved by rockfall, which over time coalesced into larger troughs that captured the path of subsequent rocks. This process led to a self‐enhancing feedback that produced a bumpy surface with rocky chutes. Rock size had a larger effect on erosion amounts than the steepness of the hill. Our work suggests that dry rockfall can play an important role in the evolution of mountain slopes on Earth and craters on the Moon and other planets. Key Points: Rockfall can erode rocky hillslopes even below the angle of reposeGrain size has a dominant effect on impact abrasion; slope is of minor importanceTopographic steering of grain results in self‐formed bedrock channels [ABSTRACT FROM AUTHOR]

The crack initiation stress threshold ( σ ci ) is an essential parameter in the brittle failure process of rocks. In this paper, a volumetric strain response method (VSRM) is proposed to determine the σ ci based on two new concepts, i.e., the dilatancy resistance state index ( δ ci ) and the maximum value of the dilatancy resistance state index difference ( Δ δ ci ), which represent the state of dilatancy resistance of the rock and the shear sliding resistance capacity of the crack-like pores during the compressive period, respectively. The deviatoric stress corresponding to the maximum Δ δ ci is taken as the σ ci . We then examine the feasibility and validity of the VSRM using the experimental results. The results from the VSRM are also compared with those calculated by other strain-based methods, including the volumetric strain method (VSM), crack volumetric strain method (CVSM), lateral strain method (LSM) and lateral strain response method (LSRM). Compared with the other methods, the VSRM is effective and reduces subjectivity when determining the σ ci . Finally, with the help of the proposed VSRM, influences from chemical corrosion and confining stress on the σ ci and Δ δ ci of the carbonate rock are analyzed. This study provides a subjective and practical method for determining σ ci . Moreover, it sheds light on the effects of confinement and chemical corrosion on σ ci . Highlights: A volumetric strain response method (VSRM) is proposed to determine the crack initiation stress threshold from the volumetric strain curve. Two novel parameters, i.e., the dilatancy resistance state index and the maximum dilatancy resistance state index difference, are proposed to help the VRSM determine σ ci . Rock's compressive stage is divided into two stages: the interlocking stage and the shear sliding stage. The crack initiation stress threshold divides these two stages. Relationships between the crack initiation stress threshold and rock's mechanical properties (i.e., Young's modulus, Poisson's ratio, mobilized cohesion and friction angle) are analyzed. [ABSTRACT FROM AUTHOR]

Understanding the mechanical behaviour of jointed rock during seismic events is crucial for ensuring the stability of rock engineering. A series of uniaxial compression tests were conducted on granite specimens containing a persistent joint at strain rates (10−5–0.05/s). Acoustic emissions (AEs) were monitored to detect the rock fracturing, and the strain field on the specimen surface was measured by the digital image correlation technique. Three failure patterns of specimens were observed: rock splitting, joint slipping and mixed rock splitting–joint slipping. The shapes of typical strain–stress curves for the three patterns are different, but they are all characterised by multiple stress drops indicating significant rock fractures. When significant fractures occur, the frequency range of AEs expends and the dominant frequency of AEs becomes much larger. The specimen strength is affected by the strain rate, but this effect differs for different failure patterns of specimens. The joint inclination could influence the mode and profile of fractures near the joint, and the specimen strength and joint stiffness significantly decrease with increasing joint angle. This study could help better understand the behaviour of jointed rocks subjected to seismic loads. [ABSTRACT FROM AUTHOR]

Rock avalanches reach considerably greater runout lengths than predicted by Coulomb friction. While it has been known for a long time that runout length increases with volume, explaining the increase qualitatively is still a challenge. In this study, the widely used Voellmy rheology is reinterpreted and modified. Instead of adding a Coulomb friction term and a velocity-dependent term, the modified rheology assigns the two terms to different regimes of velocity. While assuming a transition between Coulomb friction and flow at a given velocity is the simplest approach, a reinterpretation of an existing model for the kinetic energy of random particle motion predicts a dependence of the crossover velocity on the thickness of the rock avalanche. Analytical solutions for a lumped mass on a simple 1D topography reveal the existence of a slope-dominated and a height-dominated regime within the regime of flow. In the slope-dominated regime, the kinetic energy at the foot of the slope depends mainly on the slope angle, while the absolute height relative to the valley floor has little effect, and vice versa. Both regimes can be distinguished by the ratio of a length scale derived from the rheology and the length scale of the topography. Long runout occurs in the height-dominated regime. In combination with empirical relations between volume, thickness, and height, the approach based on the random kinetic energy model reproduces the scaling of runout length with volume observed in nature very well. [ABSTRACT FROM AUTHOR]

Uniaxial compression experiments of limestone–coal specimens at different inclination angles (0, 15, 30, 45, and 60°) were conducted using acoustic emission and three-dimensional, extension test digital image correlation, and full-field strain measurement systems to examine how dip angles affect deformation failure. The findings indicate that: (1) specimen groups demonstrate plastic yield characteristics in the pre-peak stage. However, slight variations exist due to inclination angles. (2) The localization zone for deformation evolution closely correlates to primary crack initiation and propagation within coal specimens and to slipping at the rock's and coal's interface. Failure in the coal specimen triggers rebound deformation in limestone when the rock coal inclination angle is set at 15°. Both the rebound deformation amount and its rate exhibit upward trends as a function of the inclination angle. (3) The percentage of pre-peak elastic property density in the combined specimen is augmented from 98.56 to 88.08% as the inclination angle augments and reduces to 75.80%. External energy's conversion into missile performance shows an initial increase followed by a decrease. (4) The energy rate of the acoustic emission (AE) signal exhibits distinct temporal characteristics in the combined specimen that can be associated with quiet, active, and sudden increases. [ABSTRACT FROM AUTHOR]

Santa Maria dell'Isola is a rocky promontory surrounded by the Tyrrhenian Sea and located in Tropea municipality in Vibo Valentia Province (Calabria, southern Italy) (Fig. The preliminary results discussed herein suggest that the possible causes of the instability phenomena are imputable to the sandstone rocks' weak nature, the rock masses' high fracturing state, and the intense erosive processes by sea wave energy at the cliff foot. They show the topographic changes caused by rocks detached and the material accumulation at the foot of the cliff Conclusion Assessing the cause of the slope instability and focusing on site-specific geological characteristics are crucial steps before projecting suitable consolidation interventions. [Extracted from the article]

Highlights: The proposed method solves the difficulty of unstable sliding rock (USR) adjustment. The study provides a judgment criterion for the quantitative identification of USR. The improved method can provide a practical reference for engineers engaged in rapidly identifying USR. [ABSTRACT FROM AUTHOR]

Weak interlayers in rockslides often become the controlling factor for slope deformation due to their poor physical properties and tendency to undergo argillization. Achieving a comprehensive understanding of the weak interlayers will help us comprehend the mechanism of rock slope failure and protect people's property. Some weak interlayers will develop into clay interbeds after tectonic activity and long-term groundwater action. A comprehensive review of clay interbeds includes a discussion on the formation conditions, the governing factors of the argillization process, and the investigation methods. The clay minerals in clay interbeds, illite, montmorillonite, and Kaolinite, play a major role in the acceleration of the argillization process. The argillization process can be observed through scanning technology and investigated using nonlinear dynamics, statistics, and numerical modeling methods, which may result in limitations for extracting parameters. It is necessary to conclude a unified evaluation standard to find the basic commonness during the argillization process of clay interbeds. It would be a future trend to establish the quantitative relationships among the mechanical strength, micro-structure and content of clay minerals of the clay interbeds during the argillization process. [ABSTRACT FROM AUTHOR]

This study conducted water-induced fault slip experiments on saw-cut granite, sandstone, and limestone samples. Experimental results demonstrated that injecting 15 MPa pressurized water into the vicinity of a high-permeability sandstone fault could decrease the effective normal stress and induce fault slip but not significantly affect the stress of granite and limestone faults due to low permeability. When the pressurized water was injected into the fault plane, 1 MPa pressurized water could not significantly affect fault stress; however, the 15 MPa pressurized water caused a significant reduction in frictional strength and induced fault sliding. The actual pore pressure differed from the injection pressure and showed significant differences in three faults, resulting in the apparent difference in stress drop, slip duration, displacement, and sliding rate. Three faults showed velocity-strengthening properties at room temperature. The fault slip caused by 15 MPa pressurized water injection was a direct response of fault strength to the reduction in effective normal stress. The limestone fault was characterized by velocity-weakening behavior at 100 °C, and the sliding rate of the fault induced by the 15 MPa pressurized water injection was faster than that at room temperature. The experiment results suggest that high-pressure injection can dominate over velocity-dependent effects, inducing fault-unstable slips in velocity-strengthening faults, but is more likely to induce medium-strong earthquakes on the velocity-weakening fault. [ABSTRACT FROM AUTHOR]

In dynamic disasters involving rock slopes, wedge failures formed by complex structural discontinuities are more predominant, and the dynamic response associated with them remains a classic concern in rock slope engineering. To address this concern, this paper utilized refined modeling to analyze a wedge-shaped rock slope by inputting horizontal harmonics as loads. We conducted dynamic response analyses by varying the inclination of the structural surface on the wedge-shaped rock slope, the axial offset angle, the friction coefficient, and the configuration of the single sliding surface. The results in this paper indicate that for wedge-shaped and single-sliding-surface configurations of rock slopes, with an increase in the structural surface inclination angle, the dynamic response of the sliding body, stress distribution, excellent frequency, and spectrum values all increase. Furthermore, wedge-shaped rock slopes' dynamic responses are more significant than those of single-sliding-surface rock slopes. For wedge-shaped rock slopes, increases in the axial offset angle and structural surface friction coefficient reduce the dynamic response, excellent frequency, and spectrum values. Meanwhile, within the context of the axial offset angle conditions in wedge-shaped rock slopes, the dynamic response, excellent frequency, and spectrum values are better than the variations in the structural surface friction coefficient. Under the influence of these factors, stress concentration occurs at the sliding fronts of rock slopes. [ABSTRACT FROM AUTHOR]

Rockslides are a major hazard in mountainous regions. In formerly glaciated regions, the disposition mainly arises from oversteepened topography and decreases through time. However, little is known about this decrease and thus about the present-day hazard of huge, potentially catastrophic rockslides. This paper presents a new theoretical concept that combines the decrease in disposition with the power-law distribution of rockslide volumes found in several studies. The concept starts from a given initial set of potential events, which are randomly triggered through time at a probability that depends on event size. The developed theoretical framework is applied to paraglacial rockslides in the European Alps, where available data allow for constraining the parameters reasonably well. The results suggest that the probability of triggering increases roughly with the cube root of the volume. For small rockslides up to 1000 m3 , an exponential decrease in the frequency with an e -folding time longer than 65 000 years is predicted. In turn, the predicted e -folding time is shorter than 2000 years for volumes of 10 km3 , so the occurrence of such huge rockslides is unlikely at the present time. For the largest rockslide possible at the present time, a median volume of 0.5 to 1 km3 is predicted. With a volume of 0.27 km3 , the artificially triggered rockslide that hit the Vaiont reservoir in 1963 is thus not extraordinarily large. Concerning its frequency of occurrence, however, it can be considered a 700- to 1200-year event. [ABSTRACT FROM AUTHOR]

Rapid slip, at rates in the order of 1 m/s or more, may induce frictional melting in rocks during earthquakes. The short-lived melting has been thought to be a disequilibrium process, for decades. We conducted frictional melting experiments on acidic, basic, and ultrabasic silicate rocks at a slip rate of 1.3 m/s. The experiments and microstructural observations reveal that all minerals in the rocks are melted at temperatures below their known melting temperatures (Tm); e.g., quartz is melted at ~ 1000–1200 °C, not ~ 1720 °C, while olivine at ~ 1300 °C, rather than ~ 1700 °C. The low-temperature melting is incompatible with the conventional disequilibrium melting, and may be caused predominantly by grain size reduction and phase boundary reactions during the early and later stages of slip, respectively. The newly estimated Tm and the melting mechanisms should be considered for understanding the mechanics of earthquakes, landslides, and caldera collapses. [ABSTRACT FROM AUTHOR]

A catastrophic rock planar slide occurred in the parish of Palmeira de Faro, Esposende (N Portugal), on November 23, 2022, in the middle of the night, killing two people while they were asleep in the first floor of a building close to the affected cut slope. The collapsed slope presented a maximum height of about 23 m, and was excavated in a granitic rock mass strongly weathered, in some areas by mechanical means and, locally, with the support of blasting. The displaced material, with an estimated volume of 2000 m3, described an oblique trajectory with respect to the dip direction of the slope with a maximum length of about 44.6 m. The direction of the trajectory could be explained by the strong structural control of the instability trough three discontinuity sets which delimit the slid rock mass causing multiple damage on the above-mentioned building. Although further detailed studies are necessary to elucidate the causes of the landslide, the unfavorable geological conditions, the anomalous accumulated rainfall during the previous two months (more than double than in the historic records), and some excavations apparently performed on the cut slope could be related to this instability. Therefore, this recent landslide highlights the important influence of the rock mass structure on the development of rock planar slides. [ABSTRACT FROM AUTHOR]

To comprehensively understand the mechanical response of a rock-coal combination structure containing a weak layer, a series of laboratory static loading and impact loading experiments were conducted. The results showed that under static load, the sliding process of the rock coal structure was relatively slow, and fragments can be observed. Under the action of horizontal impact loading, the whole coal stratum slipped out rapidly, and the process lasted only 0.05 s. Under the horizontal and axial impact loads, the coal stratum remained stable first, and then it slipped out as a whole under the action of static load. Additionally, a sliding instability criterion of a rock coal structure containing a weak layer was established based on theoretical analysis. The key parameter P value was checked through a numerical simulation experiment. It was found that the value was linearly related to the mechanical properties of the weak layer and overburden stress, and the experimental results coincided with the theoretical results. Finally, the relationship between sliding rockburst and strain rockburst was discussed, and these results can provide an important scientific basis for the prevention and control of dynamic disasters in deep mining. [ABSTRACT FROM AUTHOR]

On 8 May 2022 and 12 April 2020, two large rock avalanches occurred in Zhijin County, China, in the villages of Baiyan and Baiwu, respectively. These long-runout rock avalanches had the same geological, hydrological, and topographical settings and similar triggering factors but different mobility, and this inspired a research interest in the failure and runout processes of large-volume mass movements. In this study, a detailed on-site field investigation was conducted with the aid of unmanned-aerial-vehicle-based photogrammetry and satellite imaging technologies. The results suggest that the two rock avalanches were, rather than a single factor, collaboratively triggered by multiple loading effects involving long-term underground coal-mining vibration, karstification, and cumulative precipitation. The cliff failure was dominated by the strength of the rock mass and development of the joints, while the runout was controlled by the dynamic performance of the soil on the potential sliding surface rather than the rock debris itself. The liquefaction performance of the sliding surface—consisting of coarse soils on an ancient eluvial slope in the transition area—indicates that the Baiyan avalanche had significantly longer runout and higher mobility than the Baiwu case. Although the two avalanches had different mobilities, they both briefly obeyed a physics-based statistical evaluation method—the energy line. [ABSTRACT FROM AUTHOR]

A rock mass is a system of various scale blocks embodied into one another. Inter-block layers are usually composed of weaker and fissured rocks. On the action of dynamic-static loads, it can induce slip instability between blocks. In this paper, the slip instability laws of block rock masses are studied. Based on theory and calculation analysis finding that the friction force between rock blocks varies with block vibration and the friction between rock blocks can drop sharply, resulting in slip instability. The critical thrust and occurrence time of block rock masses slip instability are proposed. The factors affecting block slipping instability are analyzed. This study has significance to the rock burst mechanism induced by slip instability of rock masses. [ABSTRACT FROM AUTHOR]

This paper present results of shaking‐table tests conducted in 2015 and 2018 on a free‐standing base sliding and rocking system, which allows sliding and uplifting. A full‐scale 10‐story reinforced concrete (RC) building equipped with cast iron plates on the bottom surface of the grade beams was used as a specimen for 2015 and 2018 experiments. In 2018, the static friction coefficients of the specimen were 0.48 and 0.49, which was higher than that of the rustproofed specimens in 2015. In the experiments of 2015 and 2018, the normalized base shear (NBS) values when the sliding length of the building reached ≥1 mm were 0.0035–0.1795 and 0.1744–0.2748, respectively. In the shaking‐table test corresponding to moderate earthquake motions, the 2018 specimen showed almost no lateral movement, whereas the 2015 specimen moved laterally. Therefore, more seismic energy was input into the specimen, and the maximum interstory drift ratio of the 2018 specimen was larger than that of the 2015 specimen. However, when the 50% amplitude excitation results of the 2015 seismic structural system are compared with those of the 2018 free‐standing structural system, the 2018 results are approximately 0.57 times smaller. Thus, a free‐standing structural system with cast iron plates to reduce earthquake energy could reduce damage to buildings. The 2018 specimen satisfies the concept of a free‐standing base sliding and rocking system that does not move laterally during small to moderate earthquake motions but moves laterally during strong earthquake motions to suppress structural damage. [ABSTRACT FROM AUTHOR]

This paper focuses on the seismic analysis and performance assessment of the self‐centering moment‐resisting frames with sliding rocking beams (SCMRF‐SRB) through a nonlinear numerical simulation study. In the SCMRF‐SRB systems, the beam is comprised of three segments with the rocking beam placed in the middle segment. The beam growth (expansion) problem due to the gap‐opening in the rocking joint is counteracted by the sliding movement of the rocking beam inside the beam brackets. The restoring force of such SCMRF‐SRBs is generated by two sets of preloaded disc springs mounted on each side of the web of the beam and the energy dissipation is provided by replaceable hysteretic dampers (RHD). The relative movement of the rocking beam inside the brackets generates a friction force that contributes to the energy dissipation capacity and strength of the system based on prior experimental observations. Load vs. displacement relationships of an SCMRF‐SRB modular structure were formulated and verified with nonlinear finite element analysis results. A three‐story building located in downtown Seattle was designed and its seismic performance was studied through nonlinear static and dynamic analyses. According to the results of the nonlinear dynamic analyses, the prototype structure met the expected performance criteria in terms of inter‐story drift ratio (IDR), re‐centering behavior, and responses of the frame member at design basis earthquake (DBE). In different parametric studies, the effect of the length and location of the rocking beam on the seismic performance of the prototype structure was investigated. Moreover, the effects of the energy dissipation capacity and post‐yielding stiffness on the structural responses of the prototype buildings were studied. It was also shown that an SCMRF‐SRB structure with a large energy dissipation ratio of up to 90% can be utilized without adversely affecting the self‐centering performance of the system. [ABSTRACT FROM AUTHOR]

Hillslope failure along the highway is one of the most hazardous natural phenomena that leads to economic loss. One such slope failure occurred during the 2019 and 2020 monsoon, along National Highway (NH-547) at Sillewani Ghat, Chhindwara, state of Madhya Pradesh, India. After the first failure (2019), the slope was reinstated by the construction of a gabion wall with a mattress. Again, in 2020, the downhill slope failed which resulted in the washing away of one outer lane of pavement while the uphill slope was stable. Detailed field and laboratory investigations were carried out to explore the possible causes of slope failure and recommendations for appropriate remedial measures. Field investigation includes reconnaissance survey, geophysical test (electrical resistivity tomography and seismic refraction tomography), and standard penetration test. Soil and rock samples were collected and different geotechnical characteristics were determined in the laboratory. Seepage coupled slope stability analysis was carried out simulating field conditions. The result of the geotechnical investigation indicates that rock formation is moderately weathered and stable while the downhill slope has four-layers of loose clayey sand, gravel soil, highly and moderately weathered basalt rock. Due to heavy rainfall in 2020, downhill overburden soil (sand and gravel) got saturated and water channel formed at the interface of soil and rock resulted in the slip failure of the slope due to a reduction in effective shear strength. Seepage analysis revealed that phreatic line was existing at shallow depth during heavy rainfall which also supported the failure. Different remedial measures were recommended to reinstate the pavement namely stabilization of slope using soil nailing with and without gabion wall and provision of proper surface/subsurface drainage systems. [ABSTRACT FROM AUTHOR]

In mountainous areas, rock avalanches swarm downslope leading to large impact forces on structures. Baffle systems are usually set up in torrent channels to dissipate the flow energy and reduce the destructive effects. In this paper, a crown-like baffle system is proposed to better dissipate the flow energy. The energy dissipation mechanism of this system was investigated based on DEM. The results reveal more than 90% of the kinetic energy of the granular flow was dissipated by particle-particle interaction. Two effects, the impedance effect and the deflection effect, were identified. The influence of these effects leads to the formation and growth of cushions behind the baffles, and these cushions enhance the particle-particle interaction. Two crown-like baffle systems were compared with a conventional baffle system based on the typical avalanche model. The results reveal the cumulative residual kinetic energy of the crown-like baffle system with square baffles decreased by 18.75% with the same concrete consumption as the conventional baffle system. For the crown-like baffle system with triangular baffles, the cumulative residual kinetic energy decreased by 6.22% with 83.94% of the concrete consumption of the conventional baffle system. Hence, the proposed baffle system is more cost-effective compared with the conventional baffle system. [ABSTRACT FROM AUTHOR]

The curious occurrence of perfectly spherical particle debris when a steel substrate is slid against a hard abrasive was first documented by Robert Hooke in the seventeenth century. Similar observations now abound in other abrasion-type processes, from industrial grinding to sliding rock faults. The prevalent hypothesis, originally proposed by Hooke, is that these particles form due to high local temperatures, resulting in particle ejection, melting and resolidification. In this work, we revisit this hypothesis, using a model steel-abrasive contact, a combination of in situ and post-process investigations, and complementary analytical calculations. Our results reveal two primary findings—firstly, the temperature of particles ejected from the contact zone is far from the melting point, and secondly, exothermic surface oxidation plays a critical role in actually melting the particle. Melting is either complete or partial, leading to spherical particles or 'slivers', as described originally by Hooke. Finally, we confirm that resulting particle surface patterns are typical of rapid solidification from the melt. Apart from throwing light on a centuries' old curiosity, our results precisely quantify the melting-resolidification process, with implications for a variety of applications, ranging from abrasion and powder production to the formation of micrometeorite dust. [ABSTRACT FROM AUTHOR]

The freeze-thaw (F-T) induced deterioration in rocks affects their durability, leading to various landslides, rockslides, and avalanches. The study focuses on estimating loss in rock strength using mineralogical properties under the influence of multiple FT cycles. The rock samples were collected from F-T affected north Indian Himalayan region. The rock specimens were subjected to multiple F-T conditioning (0th, 10th, 20th and 30th F-T cycles). The mineralogical properties (such as mineralogical indices and textural indices) and mechanical properties (such as uniaxial compressive strength; UCS and Brazilian tensile strength; BTS) were calculated before and after F-T conditioning. A correlation was developed among the various strength properties and mineralogical properties. The result shows a strong relationship between the UCS and BTS with mean grain size. Further, results were used to develop a mathematical model, based on mineralogical parameter and decay function, to predict the rock strength under the influence of multiple F-T cycles. [ABSTRACT FROM AUTHOR]

During the production of open-pit mines, the stability of slopes can be affected by various factors such as structural surfaces, production blasting vibrations, and mining areas. In this study, the researchers focused on the slope of the open-pit mine at Yinshan and employed UAV mapping technology to conduct an on-site geological engineering investigation. Information on the yield, trace length, spacing, and density of the structural surface of the south slope was obtained. The researchers also carried out vibration blasting tests in combination with the production blasting activities in the mine to determine the blasting vibration attenuation law and whether the blasting vibration speed met safety specifications. Additionally, numerical simulation methods were used to examine the influence of the mining area on the stability of the current slope and the designed excavation slope. The slope stability was evaluated using the limit equilibrium method, and the researchers separately discussed the influence of self-weight load and self-weight load plus blasting vibration force on the stability of the high slope of the open pit. The results showed the following: (1) The rock mass structural plane in the south slope of the mining area was mainly dominated by a medium-large dip structural plane, and three faults and joint fissures in the investigation area combined to form cutting and sliding surfaces in the rock mass that were prone to collapse and sliding. (2) The maximum blasting vibration speed met safety requirements. (3) There was no large range of plastic zone damage in the entire slope, and the overall stability of the slope was good. (4) The present slope was relatively stable when considering only self-weight stress and the blasting vibration force. However, there was a certain risk of instability in the design of the excavation slope. [ABSTRACT FROM AUTHOR]

The eastern slope of Garmaksla, a flat-topped mountain at the western margin of Billefjorden, Svalbard, is affected by mass movements of different types. Rotational rock slides, rock fall and a rock avalanche affecting the coastal cliff are shallow surface expressions covering a larger rock mass instability that is bordered to the west by the Balliolbreen Fault. This structural feature is part of the Billefjorden Fault Zone and accommodated multi-phase deformation since Devonian time. Based on a comprehensive morpho-structural analysis, the mapped surface features and rock slope failures are explained by a compound rock slide model that reveals a litho-structural control on the type and mechanism of slope instability. The Balliolbreen Fault serves as an inherited zone of weakness that is reactivated as the rear rupture surface of the rock slide. In addition, favourably oriented bedding planes and pre-existing fault zones serve as prime conditioning factors for the compound rock slide. A postglacial age of at least 6 ka is derived from 14C dated sediments of Garmaksla Lake, a perennial sag pond along the main scarp. Although the current state of activity of the compound rock slide is unclear, an increase of shallow slope instabilities is expected owing to climate warming. [ABSTRACT FROM AUTHOR]

The physical processes that facilitate long‐distance translation of large‐volume gravity slides remain poorly understood. To better understand these processes and the controls on runout distance, we conducted an outcrop and microstructural characterization of the Sevier gravity slide across the former land surface and summarize findings of four key sites. The Sevier gravity slide is the oldest of three mega‐scale (>1,000 km2) collapse events of the Marysvale volcanic field (Utah, USA). Field observations of intense deformation, clastic dikes, pseudotachylyte, and consistency of kinematic indicators support the interpretation of rapid emplacement during a single event. Furthermore, clastic dikes and characteristics of the slip zone suggest emplacement involved mobilization and pressurized injection of basal material. Across the runout distance, we observe evidence for progressive slip delocalization along the slide base. This manifests as centimeter‐ to decimeter‐thick cataclastic basal zones and abundant clastic dikes in the north and tens of meters thick basal zones characterized by widespread deformation of both slide blocks and underlying rock near the southern distal end of the gravity slide. Superimposed on this transition are variations in basal zone characteristics and slide geometry arising from interactions between slide blocks during dynamic wear and deposition processes and pre‐existing topography of the former land surface. These observations are synthesized into a conceptual model in which the presence of highly pressurized fluids reduced the frictional resistance to sliding during the emplacement of the Sevier gravity slide, and basal zone evolution controlled the effectiveness of dynamic weakening mechanisms across the former land surface. Plain Language Summary: Large‐volume volcanic landslides pose a low‐frequency but high‐impact natural hazard due to both their massive size and long‐runout distances that exceed predictions grounded in simple sliding models. Studying the deposits of past long‐runout landslides provides insight into the physical processes that reduce friction and aid movement of slide material for long distances over the land surface. We describe the deformation styles observed in the basal zone of the gigantic Sevier gravity slide of southwestern Utah to build a conceptual model for the physical processes associated with the slide's emplacement. Field observations indicate high fluid pressures beneath the slide promoted high‐velocity sliding. During slip, mechanical breakdown of rocks exposed at the slide plane and deposition of wear products allowed pressurized fluids to escape the basal zone and resulted in deceleration of the slide. Key Points: Field observations at the long‐runout Sevier gravity slide indicate high‐velocity emplacement aided by supralithostatic fluid pressuresSlip localization and low‐permeability volcanic rocks promote effective dynamic weakening mechanisms early in translation historyIncreasing damage, permeability, and slip delocalization result in deceleration and cessation of the Sevier gravity slide [ABSTRACT FROM AUTHOR]

We present and analyze a rockfall catalog from an active landslide complex in Brienz/Brinzauls of the Swiss Alps, collected with a new Doppler radar system. This radar system provides a complete and continuous time-series of rockfall events with volumes of 1m3 and bigger since 2018 and serves as automatic traffic control for an important cantonal road. In the period between January 2018 and September 2022, 6743 events were detected, which is two orders of magnitude higher activity than in stable continental cliffs. A few percent of all rockfall events reached the shadow zone, which hosts an important road and agricultural area. The Doppler radar data set allows us to investigate the triggering factors quantitatively. We found that the background rockfall activity is controlled by seasonal climatic triggers. In winter, more rockfalls are observed during thawing periods, whereas in summer the rockfall activity increases with hourly rainfall intensity. We also found that due to the geological setting in an active landslide complex, increased rockfall activity occurs clustered in space and time, triggered by local displacement hotspots. Thus, monitoring spatial and temporal variations of slope displacement velocity is crucial for detailed rockfall hazard assessment in similar geological settings. [ABSTRACT FROM AUTHOR]

Among the almost 1400 landslides triggered by the shocks of the 2016–2017 central Italy seismic sequence, only a limited number, all classifiable as rockslides, involved volumes larger than 1000 m 3. Four of these failures, including the three largest among the documented landslides, were described in terms of structural and geomechanical investigations in a previous paper. In this study, the estimated acceleration time histories at the rockslide sites were evaluated through a 2D simplified numerical model accounting for the attenuation phenomena and for the topographic effect of the rock cliffs from which the slide detached. Instantaneous stability analyses were carried out to obtain insights into the variability of the instantaneous margin of safety along the motion, over the entire spectrum of mechanisms that could be activated. Finally, some general suggestions on the pseudo-static verification method for 3D cases are proposed, which represent useful indications to hazard evaluation at local and regional scales. [ABSTRACT FROM AUTHOR]

The failure of high-positioned rock slope often occurs in alpine and gorge regions of southwest China, resulting in huge casualties and economic and property losses. At present, there are many research theories and physical models for rock landslides, but these theories and models ignore the structural characteristics of rock mass. However, for rockslides, the structural characteristics of rock mass not only control the failure mode of slope deformation, but also affect the fragmentation process of landslide after failure, and even the final hazard range. In this study the discrete element numerical simulation method is used to simulate the fragmentation process of rockslides under different strength of joint, densities of joint, directions of joint and strength of rock mass, and to examine the influence law and mechanism of joint and rock mass characteristics on rockslides fragment characteristics, propagation type and runout. The results show that (1) the horizontal runout of the center of mass increases with the increasing strength of the structural plane, the tensile strength of the structural plane increases by 10 times, and the horizontal runout of the center of mass increases by 3%. (2) The increase of the joint density increases the relative breakage ratio of blocks, but the runout and accumulation area show a downward trend. (3) Compared with other conditions, the runout of mass in the thin bedded rock sheared by the horizontal joint is reduced by about 10%, and the accumulation area is reduced by nearly 30%. (4) The block strength increases, the relative breakage ratio of blocks decreases, and the accumulation area is eventually reduced by 40%. When the block is intact, the runout eventually increases by about 15%. This research is helpful to further understand the fragmentation process of rock landslides and guide disaster prevention and mitigation in mountainous areas.

Massive rockslides are recognized as one of the most catastrophic hazards due to their rapid sliding velocity and high destructiveness. This study focuses on the progressive failure analysis of translational rockslides (PFTRs) on a cataclinal dip slope, whose shear failure develops mainly along the bedding plane of the underlying strata from the head to the toe of the rockslide. A force and energy equilibrium-based analytical method (FEE) is proposed, combining shear failure propagation and strength degradation, to analyse the stability based on static equilibrium and displacement based on energy equilibrium. A representative translational rockslide, the Shanshucao landslide in the Three Gorges Reservoir, China, is used as a case study. The results of the FEE are validated by comparison with the revised rigid limit equilibrium method (RLEM) and numerical simulation (NS). According to the RLEM and NS, when the shear failure of the slide surface develops to a position with a horizontal distance of approximately 225 m, the rockslide steps into the critical state from partial progressive deformation to failure of the entire rockslide. The FEE obtains a similar result, and the corresponding horizontal distance is 200 m. The rockslide displacement calculated by the FEE agrees well with the results of the NS. Before the critical state, the rockslide displacement is less than 0.05 m; afterwards, the displacement of the entire rockslide obviously increases. In addition, it is proven that the hydrostatic pressure in subvertical tension cracks and the post-failure shear surfaces are the primary impetus for accelerated deformation of rockslides and further development of failure surfaces. The validated results indicate that the FEE is a straightforward and effective method to analyse both the stability and displacement of PFTR, which is significant for rockslide early warning and risk mitigation. In addition, the FEE still has limitations with regard to generalization of the landslide geo-mechanical model and the method validation with observational data of historical events. [ABSTRACT FROM AUTHOR]