Search

We explore the viability of modeling dynamic problems with a new formulation of an impulse‐based Level‐Set DEM (LS‐DEM). The new formulation is stable, fast, and energy conservative. However, it can be numerically stiff when the assembly has substantial mass differences between particles. We also demonstrate the feasibility of modeling deformable structures in a rigid body framework and propose several enhancements to improve the convergence of collision resolution, including a hybrid time integration scheme to separately handle at rest contacts and dynamic collisions. Finally, we extend the impulse‐based LS‐DEM to include arbitrarily shaped topographic surfaces and exploit its algorithmic advantages to demonstrate the feasibility of modeling realistic behavior of granular flows. The new formulation significantly improves the performance of dynamic simulations by allowing larger time steps, which is advantageous for observing the full development of physical phenomena such as rock avalanches, which we present as an illustrative example. [ABSTRACT FROM AUTHOR]

Rock avalanches onto glaciers are rare in Norway. Here, we examine a rock avalanche that spread onto the regenerated Brenndalsbreen, an outlet glacier from Jostedalsbreen ice cap. The rock avalanche is intriguing in that limited information exists with respect to the exact time of failure, location of detachment area, and preparatory and triggering processes. Based on an analysis of ice stratigraphy and photographic documentation, we assess that the event happened between mid-March and June 4, 2010. A potential triggering factor could have been heavy snow and rainfall combined with above freezing air temperatures on March 18–19, 2010. We use digital terrain models to determine that the detachment area is at an almost vertical rock slope in a narrow gorge above Lower Brenndalsbreen. The deposit volume is estimated to 0.130 ± 0.065 Mm3, and the H/L ratio and fahrböschung are 0.45 and 24°, respectively. We apply a Voellmy flow model to confirm the detachment location and volume estimate by producing realistic runout lengths. Although glacial debuttressing may have been a likely preparatory process, the detachment area was exposed for 45–70 years before the rock avalanche occurred. The supraglacial rock avalanche debris was separated into two branches with a distinct melt-out line across the glacier. The debris reached the glacier front in 2019 and 2020, where it started being deposited proglacially while Lower Brenndalsbreen kept receding. The 2010 Brenndalsbreen rock avalanche may not be a unique event, as deposits constituting evidence of an old rock avalanche are currently melting out at the glacier front. [ABSTRACT FROM AUTHOR]

Debris avalanches and dry granular flows exhibit similar characteristics. In order to comprehend the fundamental mechanisms and improve the accuracy in predicting disasters such as landslides, debris flows, and rock avalanches, the collapse characteristics of a binary granular column are investigated through a three‐dimensional discrete element model. A novel approach is proposed by incorporating the concept of local granular velocity fluctuation and applying a cluster analysis method. Then, the flow mechanism of the binary granular column is analyzed, by considering the inhomogeneous particle size distribution. The research results show that: (1) The normalized final packing height of the granular column gradually increases when the content of coarse particles exceeds 20% and when the coarse‐fine particle size ratio increases. Conversely, the normalized run‐out distance of the granular column decreases gradually with the increase in coarse particle content and the coarse‐fine particle size ratio. (2) The particles with higher granular velocity fluctuations tend to move together and form clusters, demonstrating dynamical heterogeneity. As the coarse particle content and coarse‐fine particle size ratio increase, there is a greater tendency for particles to assemble into larger‐scale active clusters. This means that a larger number of particles exhibit collective behavior during the collapse process, resulting in increased resistance to shear deformation. Ultimately, this leads to a greater packing height and a reduced run‐out distance when observed from a macroscopic perspective. [ABSTRACT FROM AUTHOR]

This study presents the Flexible Rocking Model on Concentrated Springs (FRMCS), developed to investigate 2D laterally flexible oscillators rocking and sliding on deformable support media during ground excitations. In this model, concentrated vertical springs and viscous dampers simulate the contact forces from support medium at the corners of the body; the tensionless vertical contact element is linear in compression. Horizontal concentrated springs and linear viscous dampers simulate the frictional behaviour at the corners; the constitutive law for the springs models elastic deformations and sliding (according to Coulomb's friction law). With these elements, FRMCS can model the response of a rocking body which can experience sliding and free‐flight phases of motion. The consideration of the flexibility of the support medium enables the evaluation of the forces exerted by the support medium on the structure during an impact. In this study, the FRMCS response is first compared to a previous model where the support medium deformability and the effects of sliding and free‐flight are ignored. Then, the responses of four configurations, which feature either stiff or soft lateral springs and stiff or soft high‐grip support media, are examined under the influence of pulse excitations. Finally, to understand the potential influence of sliding, a configuration with a low‐grip support medium is explored. The comparative influence of lateral flexibility and support medium deformability and sliding is quantified with stability diagrams and various response spectra, describing structural force and moment demands. [ABSTRACT FROM AUTHOR]

Two major earthquakes of Mw7.8 and Mw7.5 ruptured the Southern East Anatolian Fault (SEAF) and the Savrun‐Çardak‐Sürgü fault (SCSF), devastating southeast Türkiye and northwest Syria on 6 February 2023. We adopt innovative nonlinear and linear approaches to analyze the coseismic ground displacements and estimate the complex slip geometry. Unlike conventional analytical solutions that simplify crust heterogeneity, finite‐element fault models invert the displacement data and simulate the dual‐fault geometry with non‐uniformly distributed shallow crustal materials. Our results suggest the west‐dipping SEAF and north‐dipping SCSF accommodate earthquake slips of >10 m. Their respective slip distributions and proximal aftershocks correlate spatially with local seismic velocity anomalies (i.e., ΔVp and ΔVs), which implies differences in structural control along these two faults and provides insights into assessing the seismic hazard of mixed incipient‐mature fault systems. Plain Language Summary: In early February of 2023, southeast Türkiye and northwest Syria experienced two devastating earthquakes that claimed more than 50,000 lives and caused substantial economic loss. The epicenters are located near the active tectonic boundary between the Anatolian and Arabian Plate. The complex seismic rupture occurred over two faults, the Southern East Anatolian Fault (SEAF) and the Savrun‐Çardak‐Sürgü Fault (SCSF). Satellite interferometric images and global positioning networks capture large‐scale ground movements. Our study adopts a novel approach to analyze the slip pattern and explore the fault orientation and slip distribution. The result highlights that the fault rupture, aftershock, and local velocity anomalies are correlated, but the correlation pattern differs between the SEAF and SCSF. This improves our understanding of the earthquake hazard along the plate boundaries that host faults of different maturity levels. Key Points: Coseismic slip distribution of the 2023 Kahramanmaraş Earthquake is estimated from the ground displacements observed by SAR and global navigation satellite system dataInnovative nonlinear‐crossover‐linear inversion method combined with finite element elastic models simulating rock heterogeneityEarthquake slips and aftershocks correlating spatially with velocity anomalies imply structural controls and different fault maturity [ABSTRACT FROM AUTHOR]

Mobility of long-runout catastrophic landslides (debris flows, debris and rock avalanches) can be characterized by several parameters. Those, allowing predicting exposure of elements at risk that might be threatened by such hazardous natural phenomena if they will occur—the affected area and runout, are most important for risk assessment. They can be estimated using two general approaches—one based on the numerical modeling and another one based on the empirical relationships between runout and affected area on the one hand and parameters characterizing the potential source zone on the other hand. The latter are volume of the anticipated rock slope failure and height of the unstable slope. Both can be assessed prior to failure with certain accuracy by contrast with the height drop defined as the elevation difference between headscarp crown and the deposit tip. The optimal input parameter is the product of the unstable slope height and possible failure volume that is, in general, proportional to the potential energy of the unstable rock massif. According to the analysis of the Central Asian rockslides/rock avalanches database that includes quantitative parameters of 515 case studies with defined confinement, the relationships of such product with runout and affected area have high correlation coefficients regardless of the confinement conditions and, therefore, allow prediction of the parameters in question with sufficient reliability. It is pointed out that requirements to the accuracy of slope height and failure volume assessment depend on a large extent on the variability range of these parameters within the inventories used to derive the empirical relationships. [ABSTRACT FROM AUTHOR]

A widespread case of discontinuity shearing is found among local shallow rock blocks sliding along non-planer, rough, non-anchored discontinuities, which is characterized by an initial normal load in addition to free subsequent changes in local normal load/stiffness, provoked by shear dilatancy (INL). The existing direct shear apparatuses of rock discontinuities fitted for those cases are rare, and there is a lack of understanding of the shear behaviours of discontinuities under such INL boundary conditions. Here, we develop an INL direct shear tester of discontinuities for shear strength. This tester takes advantage of the direct shear test apparatus modified after the YZ-5 model without a servo-controlled system to permit the accomplishment of those boundary conditions. Shear behaviours of unfilled and infilled discontinuities under INL boundary conditions are investigated. Moreover, the possible influence of clay content on those shear behaviours of infilled discontinuities is clarified. The developed tester made it possible to test the shear performance of the local shallow rock blocks sliding along non-planer, rough, non-anchored discontinuities. This work contributes to a limited body of research on the shear behaviours of discontinuities under those INL boundary conditions. Limitations of this work are also revealed. [ABSTRACT FROM AUTHOR]

Although numerous recent studies have explored the relationship between permafrost degradation and rock slope failure, there is still a need for in‐depth investigations to develop relevant hazard assessment approaches. We investigate the predisposing, triggering and propagation processes of a rock avalanche (c. 225,000 m3) that occurred in Vallon d'Étache (France) on 18 June 2020, whose scar was coated by ice and water. Weather records and energy balance models show that the rock avalanche occurred right after the warmest spring and winter since at least 1985, but also right after the spring with the highest water supply anomaly (snowmelt and rainfall). Measured ground surface temperature and geoelectrical surveys reveal that relatively ice‐rich permafrost could exist in the NW face (release area) while it is inexistent below the SE face, contradicting certain permafrost maps. Heat transfer simulations suggest that the rock avalanche occurred during a transition from cold to warm permafrost conditions at failure depth (30 m), with a temperature increase of up to 0.6°C per decade since 2012 (when considering potential snow cover effect), and current temperature ranging between −3 and −1°C, depending on the applied model forcing. This warming certainly contributed to predispose slope to failure. In addition, the shift towards warm permafrost and water infiltration potentially enhancing permafrost degradation along fractures through heat advection or favouring the development of high hydrostatic pressures may have played as triggering factors. Finally, propagation simulations show that the rock avalanche involved several phases with different rheological properties due to the incorporation of snow and material segregation within the deposit. These new insights at various scales highlight the complexity of the triggering and propagation processes of rock slope failure occurring in high mountains, a significant part of which can be linked to snow effects on ground temperature, water supply and rheological properties. [ABSTRACT FROM AUTHOR]

The relatively uncontrolled dynamic behavior of a rigid block resting on a flat surface under ground motion has been well studied. In contrast, a block with a gently inclined V- or W-shaped sliding key would ensure dynamic self-centering or resetting performance under various seismic conditions. To better understand the nonlinear responses of rigid blocks having this type of interface where both rocking and sliding movements are possible, an event-based algorithm is put forward to cover various types of motions, including the transition stages between different types of motions. A comprehensive study is carried out to examine the dynamic responses of blocks of different sizes and aspect ratios. Moreover, the simplified pure rocking model and pure sliding model are also adopted to obtain rough estimates of dynamic response for comparison. The results show that the simplified models are reliable for some special cases only, e.g. squat blocks and slender blocks. The study also evaluated the influence of the coefficient of friction and slope inclination on the resetting capabilities of typical sliding-prone and rocking-prone systems. For those cases that are prone to toppling or excessive sliding under strong earthquakes, the provision of vertical post-tensioning can effectively ensure stability and resetting performance. Such findings provide insight into the performance of precast segmental bridge columns with resettable sliding joints. [ABSTRACT FROM AUTHOR]

Rock avalanches typically entail the flow-like motion of angular rock blocks and fragments of diverse size. Numerical simulations are instrumental in understanding their dynamic process, supporting hazard and risk assessments. Simplified failure criteria, such as the Mohr-Coulomb or Drucker-Prager, are commonly adopted in landslide models relying on the material point method (MPM). However, these criteria cannot capture the transitions between solid-like, liquid-like, and gas-like behaviors exhibited by granular materials. Here, we relied on the moving least-squares MPM, which offers high computing efficiency and stability, and adopted a nonlocal μ(I) rheology model implemented by Haeri and Skonieczny (Comput Methods Appl Mech Eng, 2022). This approach can account for the rate-dependent, pressure-dependent, and size-dependent characteristics of friction in granular materials. By simulating a small-scale flume experiment as well as a large-scale event (the Nayong rock avalanche in Guizhou, China), we verified that the nonlocal μ(I) rheology model can capture the motion and deposition processes in rock avalanches effectively. This feature can be advantageous in physically based hazard assessments of such events. [ABSTRACT FROM AUTHOR]

Natural fault zones are complex, spatially heterogeneous systems. Rock deformation experimental studies simplify the complexity of natural fault zones either as a surface discontinuity between intact rocks (bare‐rock surfaces) or as a few mm‐thick gouge layer. However, depending on the simplified fault type and its slip history, the response to applied deformation can vary. In this work, we conduct laboratory experiments for investigating the evolution of mechanical parameters of simulated faults made of calcite gouge subjected to multiple (four) identical seismic slip‐rate pulses. We observed that, as the number of applied slip‐rate pulses increased, (a) initial friction and steady‐state friction remained approximatively constant, (b) peak friction and normalized strength excess increased and, (c) the slip distances to achieve peak and steady‐state friction, Da and Dc, decreased. The greatest changes occurred between the first and the second slip‐rate pulse. From this pulse onward, the dissipated energy of the calcite gouge fault was similar to those obtained in bare‐rock surfaces experiments. Microstructural analysis showed that, strain is localized in up to two (recrystallized) principal slip zones (PSZ) with sub‐micrometric grain size, surrounded by low porosity sintered and non‐sintered comminuted gouge domains. We conclude that previous seismic slip episodes impact on both the structure and the strain localization processes within a fault, contributing to its shear fabric evolution. We highlight that the strain localization process identifies the PSZ, dissipating the least amount of energy within the entire experimental fault zone. Plain Language Summary: Earthquakes are caused by the propagation of seismic ruptures and sliding of rocks along geological structures called faults. Within the fault, seismic ruptures propagate in mm‐cm thick slip zones that cut cm‐ to meters‐thick fault cores. Both slip zones and fault cores typically exhibit microstructural assemblages different from those of nearby rocks. Laboratory experiments are used to investigate the processes that result in the decrease of fault strength with slip and slip‐rate and govern seismic rupture propagation. However, experiments are performed on simplified fault cores consisting of either a surface discontinuity between intact rocks (i.e., slip zone = "bare‐rock surfaces") or a mm‐thick layer of powdered rocks (i.e., slip zone in a "fault gouge"). In this work, we investigate how slip zones form and evolve in an experimental fault (gouge) core depending on seismic slip history. We apply repeated pulses of seismic slip and show that (a) in the first pulse a slip zone with similar microstructure and friction properties to bare‐rock is formed, (b) in subsequent pulses these slip zones are abandoned and new slip zones are formed in the fault core. Notably, these structural changes, occur to minimize the mechanical energy dissipated in the FC. Key Points: Friction experiments applying up to four consecutive seismic slip‐rate pulses (1 m/s), in fault gouge and bare‐rock surfacesThe greatest changes in dissipated energy occurred between the first and the second slip‐rate pulseStrain localization in the principal slip zones minimizes the energy dissipated within the whole experimental fault zone [ABSTRACT FROM AUTHOR]

Determining the shear‐velocity dependence of dry granular friction can provide insight into the controlling variables in a dry granular friction law. Some laboratories believe that the quality of this study is at the forefront of the discipline for the following reasons. Results suggest that granular friction is greatly affected by shear‐velocity (v), but shear experiments over the large range of naturally occurring shear‐velocities are lacking. Herein we examined the shear velocity dependence of dry friction for three granular materials, quartz sand, glass beads and fluorspar, across nine orders of magnitude of shear velocity (10−8–2 m/s). Within this range, granular friction exhibited four regimes, following a broad approximate "m" shape including two velocity‐strengthening and two velocity‐weakening regimes. We discuss the possible physical mechanisms of each regime. This shear velocity dependence appeared to be universal for all particle types, shapes, sizes, and for all normal stresses over the tested range. We also found that ultra‐high frequency vibration as grain surfaces were scoured by micro‐chips were formed by spalling at high shear velocities, creating ∼20 μm diameter impact pits on particle surfaces. This study provides laboratory laws of a friction‐velocity (μ‐v) model for granular materials. Plain Language Summary: Numerous phenomena of earth science can be simplified to shearing granular systems, such as landslide gouge and rock avalanches. It is believed that friction varies with shear velocity, and this is no exception for dry granular materials. Studying the law of friction variation over as large a range of velocity changes as possible aids in establishing a full life‐cycle hypothesis for landslides from initiation, through movement to cessation. We sheared granular materials across nine orders of magnitude, from 10−8 to 2 m/s and obtained an "M" shape law for the variation of friction with velocity. By analyzing the acoustic frequency of shear experiments at different velocities, we discovered that the acoustic frequency increased with shear velocity. By comparing the microscopic morphology of the particle surface before and after high‐velocity shearing, we hypothesized that the impact pits may be left by particle collisions during high‐velocity shearing. We proposed that the role of ultra‐high frequency vibration on high‐velocity shear weakening should be considered, which provides a basis for accurately revealing the physical mechanism of granular friction variation with velocity. Key Points: This paper examines the shear velocity dependence of friction for dry granular materials, across nine orders of magnitude in shear velocity (10−8–2 m/s)An "M‐shaped" law for the variation of friction with velocity is obtained including two velocity‐strengthening and two velocity‐weakening lawsThere is microscopic evidence that ultra‐high frequency vibration may cause high velocity shear weakening [ABSTRACT FROM AUTHOR]

Rockslides are one of the most dangerous hazards in mountainous and hilly areas. In this study, a rockslide that occurred on 30 November 2022 in Castrocucco, a district located in the Italian municipality of Maratea (Potenza province) in the Basilicata region, was investigated by using pre- and post-event high-resolution 3D models. The event caused a great social alarm as some infrastructures were affected. The main road to the tourist hub of Maratea was, in fact, destroyed and made inaccessible. Rock debris also affected a beach club and important boat storage for sea excursions to Maratea. This event was investigated by using multiscale and multisensor close-range remote sensing (LiDAR and SfM) to determine rockslide characteristics. The novelty of this work lies in how these data, although not originally acquired for rockslide analysis, have been integrated and utilized in an emergency at an almost inaccessible site. The event was analyzed both through classical geomorphological analysis and through a quantitative comparison of multi-temporal DEMs (DoD) in order to assess (i) all the morphological features involved, (ii) detached volume (approximately 8000 m3), and (iii) the process of redistributing and reworking the landslide deposit in the depositional area. [ABSTRACT FROM AUTHOR]

Assessing the stability behavior of deep-seated rock slides in the surroundings of large dam reservoirs requires an understanding of the geometry, the kinematics, the groundwater situation, and the rock mass and shear zone properties. This study focuses on the influence of rock slide geometry on stability evolution during initial reservoir impounding. Therefore, nine different rock slide models, mainly taken from published case studies with a well-explored geometry, were analyzed. Based on the assumption that the rock slides are close to limit equilibrium in a no-reservoir scenario, reservoir impounding causes a reduction in the factor of safety (FoS). The results show a large impact of the water level for rotational slides where the majority of the rock mass is located at the lower part of the slope. This results in a maximum reduction in the FoS of up to 12%. In contrast to this, translational rock slides are less affected by reservoir impounding. The stability analysis shows that the change in FoS is strongly controlled by the kinematics of the rock slide and the geometry near the foot of the slope. Consequently, a comprehensive in situ investigation of the geometry and kinematics is necessary in order to reliably assess the influence of initial reservoir impounding. [ABSTRACT FROM AUTHOR]

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]

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]

Many landslide models assume a fully deformable body without any resistance against deformation. However, in reality, landslide bodies can display negligible to large deformation during motion. Examples for limited deformation include the prehistoric giant landslides of Flims and Köfels, or the Vajont landslide of 1963, where the structure of rock largely remained intact and the slides did not evolve into rock avalanches. Here, we propose a novel mechanical model for the controlled deformation of landslides. The model is based on the principle of material strength or resistance and includes a user‐specified function that reflects the mechanisms (internal friction, cohesion, viscosity, and yield strength) that act against the deformation induced by the free‐surface or the hydraulic pressure gradient of the landslide. This controls the landslide deformation and, in turn, also the motion and run‐out, and offers a unique possibility to describe the landslide motion ranging from a fully non‐deformable body sliding along the mountain slope to a completely fluidized motion without any resistance against the force associated with the free‐surface pressure gradient. The latter is the situation often considered for the motion of granular flows such as avalanches of snow or rock, or debris flows. The former can play a substantial role in the dynamics, however, has not yet been considered in mass flow simulations, severely limiting the applicability of those models. We demonstrate the performance of the new model and its applicability, also with the advanced open‐source computational mass flow simulation tool r.avaflow. Plain Language Summary: When simulating the movement of landslides on a computer, most of the models which have been used until now assume a very strong deformation of the moving mass, almost like flowing water. However, this is only suitable for some landslides, but not for all. Many landslides rather move as rigid blocks rather than flowing water. Here, we introduce a simple mechanical model for the controlled landslide deformation which is able to automatically simulate landslides moving as rigid blocks, and also landslides which behave in a way that is in between a rigid block and flowing water. We integrate this model in a computer program which is freely available to use, and present some tests on simple computer‐generated landscapes to demonstrate that the model is working well. Key Points: We propose a novel mechanical model for the controlled deformation of landslidesThe model is based on the principle of material strength acting against the deformation induced by the hydraulic pressure gradientThis offers a unique possibility to describe the landslide ranging from a fully non‐deformable body to a completely fluidized motion [ABSTRACT FROM AUTHOR]

The discontinuation of pumping and drainage activities upon the cessation of mining operations leads to the gradual accumulation of groundwater. This inflow into mined-out areas affects the properties of the rock, disturbing the previously stable goaf and exacerbating instability. In this study, we advance an existing theoretical framework pertaining to the residual deformation of mines by delineating the mechanisms through which groundwater influences the degradation of the overlying strata in goaf areas. Using analogous material simulation experiments and rigorous theoretical analyses, we clarify the specific mechanisms by which groundwater causes structural damage to these regions. The deformation of overlying rock is divided into three different forms: the compressive deformation of rock, the sliding instability of rock, and the rotational instability of rock. The main contributions of this study are its refinement of the existing theory of the residual deformation of mines, an analysis of the damage mechanisms of groundwater, and suggestions regarding technical support for targeted treatment measures in affected mines. [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]

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]

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]

The flow of granular materials such as soil, sand, and gravel is a common occurrence in mountainous area in the form of geological disasters, such as debris flows, landslides, and rock avalanches. A solid comprehension of the propagation and impact behavior of granular flow is imperative for the disaster prevention and mitigation. However, due to the intricacy of granular flow, it is difficult to predict the propagation and impact behavior of dry granular flows although some pioneering research works have been presented in the literature. In this paper, physical model experiments and numerical simulations based on the Particle Flow Code (PFC) are conducted to analyze the motion process, accumulation pattern and impact force of dry granular flow, and discuss the effects of slope angle, particle size and baffle height. Based on the high similarity between experimental and numerical results, it indicates that the run-out distance and peak velocity of the granular flow increases with the slope angle and particle size. Rigid baffle can significantly reduce the kinetic energy of the granular flow and decrease the run-out distance. The impact force of granular flow on the rigid baffle increases with the slope angle, particle size, and height of the baffle. The magnitude and distribution of the impact force on the baffle are in accordance with the contact force between the granular material and the baffle. These studies can contribute to better understand the characteristics of granular flow disasters and provide a reference for corresponding protection engineering. [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]

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]

As a result of climate change, rockfalls and rock avalanches as well as landslides lead to an increasing hazard for settlement areas and infrastructures. The hazards of such mass movements mean that numerous protective structures must be planned and built. In addition to building such constructions, the refurbishment of existing protective structures is also playing an increasingly important role. Some of these protective structures are rigid structures consisting of concrete and/or steel elements. Due to the difficult accessibility, flexible net constructions are often considered. Embankment constructions are normally erected to protect against large mass movements. The choice of the right type of construction is based not only on geotechnical and geographical conditions, but also on the occurring energies and the impact of rockslides on the protective structure. In this study, small-scale laboratory experiments with different protective structures are presented. Rigid and flexible structures as well as reinforced embankments are investigated. Based on the results of the experiments, the impacts and deformations are recalculated numerically using the discrete element method (DEM). From the small-scale laboratory experiments and numerical simulations, the differences regarding the construction type of the protective structure can be investigated. An essential main point concerns the relationship between the flexibility of the barrier and the total impact load. The presented work is limited to the investigation of strongly fragmented gravitational mass movements such as rock avalanches. Highlights: The results from model experiments are shown and analyzed to investigate the impacts on protective structures due to highly fragmented granular mass movements (rock avalanches). The behavior of protective structures, such as rigid barriers, flexible barriers, and embankments, is investigated. Numerical simulations based on the discrete element method (DEM) are used to calculate the flow characteristics of the granular mass, the force–time behavior of the impact on the different types of barriers, and the deformations of the flexible barriers. Based on the model experiments and DEM simulations, a limit value is determined depending on the deformation, at which an increased load on flexible protective structures should be taken into account. [ABSTRACT FROM AUTHOR]

The North Bengkulu-Lebong Mountain Road is prone to landslide disasters due to its geological susceptibility to land movement. This study aims to measure and assess the sliding plane on the mountain road, particularly in the layer with a soft rock structure, such as clay rock. The study utilizes 2D and 3D Electrical Resistivity Tomography (ERT) methods with the Wenner- Schlumberger configuration to measure the resistivity of the rock layers.The research includes one 2D measurement point and one 3D ERT measurement point, estimating actual resistivity values in each rock layer. Our results identify triggering and controlling factors for landslide disasters in the research area. The geological conditions consist of layers of clay (200-500 Ωm), wet clay (500-900 Ωm), dry clay (1000-3000 Ωm), weathering clay (500-1000 Ωm), aquifer (10-65 Ωm), perched aquifer (100-200 Ωm), weathering igneous rock (>10000 Ωm), and massive intrusive rock (>20000 Ωm). These geological conditions significantly influence the strength of landslide materials, with the sliding of the soft rock layer causing landslides and resulting in a large volume of landslide material. Other contributing factors to landslides in this location include slope, topography, and hydrology, with extreme slopes ranging from 33° to 55°, making it a very steep area with high potential for landslides. [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]

Rock fragmentation plays a critical role in rock avalanches, yet conventional approaches such as classical granular flow models or the bonded particle model have limitations in accurately characterizing the progressive disintegration and kinematics of multi-deformable rock blocks during rockslides. The present study proposes a discrete-continuous numerical model, based on a cohesive zone model, to explicitly incorporate the progressive fragmentation and intricate interparticle interactions inherent in rockslides. Breakable rock granular assemblies are released along an inclined plane and flow onto a horizontal plane. The numerical scenarios are established to incorporate variations in slope angle, initial height, friction coefficient, and particle number. The evolutions of fragmentation, kinematic, runout and depositional characteristics are quantitatively analyzed and compared with experimental and field data. A positive linear relationship between the equivalent friction coefficient and the apparent friction coefficient is identified. In general, the granular mass predominantly exhibits characteristics of a dense granular flow, with the Savage number exhibiting a decreasing trend as the volume of mass increases. The process of particle breakage gradually occurs in a bottom-up manner, leading to a significant increase in the angular velocities of the rock blocks with increasing depth. The simulation results reproduce the field observations of inverse grading and source stratigraphy preservation in the deposit. We propose a disintegration index that incorporates factors such as drop height, rock mass volume, and rock strength. Our findings demonstrate a consistent linear relationship between this index and the fragmentation degree in all tested scenarios. [ABSTRACT FROM AUTHOR]

Rock avalanches are generally difficult to prevent and control due to their high velocities and the extensive destruction they cause. However, barrier structures constructed along the path of a rock avalanche can partially mitigate the magnitudes and consequences of such catastrophic events. We selected a rock avalanche in Nayong County, Guizhou Province, China as a case to study the effect of the location and height of a retaining wall on the dynamic characteristics of rock avalanche by using both actual terrain-based laboratory-model tests and coupled PFC3D–FLAC3D numerical simulations. Our findings demonstrate that a retaining wall can largely block a rock avalanche and its protective efficacy is significantly influenced by the integrity of the retaining wall. Coupled numerical simulation can serve as a powerful tool for analyzing the interaction between a rock avalanche and a retaining wall, facilitating precise observations of its deformation and destruction. The impact-curve characteristics of the retaining wall depend upon whether or not the rock avalanche-induced destruction is taken into account. The location of the retaining wall exerts a greater influence on the outcome compared to the height and materials of the retaining wall, while implementing a stepped retaining-wall pattern in accordance with the terrain demonstrates optimal efficacy in controlling rock avalanche. [ABSTRACT FROM AUTHOR]

An editorial focuses on the potential for increased catastrophic flow events in alpine glacier zones due to climate change, using the Chamoli rock-ice avalanche as a case study. It highlights the severe instability of alpine slopes as a consequence of glacial retreat and warming temperatures, suggesting that such events are likely to become more frequent and severe. It emphasizes the need for ongoing monitoring and assessment of these high-risk areas to mitigate future disasters.

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]

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]

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]

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]