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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 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]

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]

We propose a numerical model of laboratory earthquake cycle inspired by a set of experiments performed on a triaxial apparatus on sawcut Carrara marble samples. The model couples two representations of rock matter: rock is essentially represented as an elastic continuum, except in the vicinity of the sliding interface, where a discrete representation is employed. This allows to simulate in a single framework the storage and release of strain energy in the bulk of the sample and in the loading system, the damage of rock due to sliding, and the progressive production of a granular gouge layer in the interface. After independent calibration, we find that the tribosystem spontaneously evolves toward a stick‐slip sliding regime, mimicking in a satisfactory way the behavior observed in the lab. The model offers insights on complex phenomena which are out of reach in experiments. This includes the variability in space and time of the fields of stress and effective friction along the fault, the progressive thickening of the damaged region of rock around the interface, and the build‐up of a granular layer of gouge accommodating shear. We present in detail several typical sliding events, we illustrate the fault heterogeneity, and we analyze quantitatively the damage rate in the numerical samples. Some limitations of the model are pointed out, as well as ideas of future improvements, and several research directions are proposed in order to further explore the large numerical data set produced by these simulations. Plain Language Summary: Earthquakes are due to sudden sliding in faults several kilometers in the ground. A common laboratory practice is to reproduce such sliding events on dedicated lab devices. In this work, we present a novel numerical model aiming to reproduce such experiment in a computer simulation, in order to enhance our understanding of the phenomena at stake. This model is novel because it couples two different representations of the rock matter, namely a continuous and a discrete one. It therefore allows to reproduce in the same framework the bulk deformation of rock and the granular phenomena occurring at the sliding interface. The model is calibrated and leads to the spontaneous occurrence of unstable sliding, that is, of earthquakes of the same kind as those observed in the lab. We further explore into more detail some typical sliding events, and focus our attention of the interface damaging and wear during sliding. This work is likely to clarify our interpretations of sliding events in the lab. Key Points: A coupled Discrete‐Continuum model of a laboratory earthquakes experiment leads to the spontaneous development of numerous seismic cyclesThe stress fields on the fault are found to be very heterogeneous. Typical events of various sizes are analyzed in detailsDamage and wear of the interface are quantified during sliding, and their rates are found to follow different laws [ABSTRACT FROM AUTHOR]

Herein, the mechanisms underlying the slip and failure of a coal-rock parting-coal structure (CRCS) under biaxial compression with horizontal unloading were investigated using numerical simulations and field observations. The failure and instability characteristics were studied, including fracture, slip, and energy release characteristics, as well as the mechanisms whereby different factors influence the failure and instability characteristics of the structure. Based on a rockburst triggered by rock-parting slip in the field, the results obtained from the numerical simulations were verified. In particular, the microseismic (MS) effects of rock-bursts were revealed in detail. The following four points were addressed: (1) a linear positive correlation between the peak value of axial stress and the actual value of the horizontal stress was found under biaxial compression; (2) shear stress of the discontinuities and local stress concentration were the leading factors for the failure and instability of the CRCS under both biaxial compressional stress and horizontal stress unloading conditions; 3) higher horizontal stress or higher unloading speed easily induced instability (fracture or slip) of the CRCS, while the fracture and slip degree weakened with the increasing unloading speed; and 4) the MS signals of the rockburst were characterized by a wide range of frequencies and high amplitudes, in which the low-frequency part was related to the slip of the rock parting and the high-frequency part reflected fractures of the coal-rock mass. This work is relevant for understanding the mechanism underlying coal-rock dynamic disasters triggered by the slip and instability of CRCS in coal mines. Highlights: Microscopic features of shear slip and failure in coal-rock parting-coal structures were researched. Dominant factors for slip and failure of coal-rock parting-coal structures were investigated. Stress and unloading speed have significant effects on shear slip and failure of coal-rock parting-coal structures. Field investigations confirmed the instability characteristics of coal-rock parting-coal structures. [ABSTRACT FROM AUTHOR]

On 30 October 2020, a large Mw = 7.0 earthquake occurred north of the island of Samos, Greece. Here we present the characteristics of the seismic fault (location, geometry, geodetic moment) as inferred from the processing of geodetic data (InSAR and GNSS). We use the InSAR displacement data from Sentinel-1 interferograms (ascending orbit 29 and descending 36) and the GNSS offsets from fourteen (14) stations in Greece and Turkey to invert for the fault parameters. Our inversion modelling indicates the activation of a normal fault offshore Samos with a length of 40 km, width of 15 km, average slip of 1.7 m, a moderate dip-angle (37°) and with a dip-direction towards North. The inferred fault is located immediately north of, and adjacent to Samos with the top of the slip ~ 0.6 km below surface, and ~ 1 km offshore at its closest to the island. Near the fault, the earthquake caused the permanent uplift of the island up to 10 cm with the exception of a coastal strip along part of the northern shore that subsided 2–6 cm. The co-seismic horizontal motion of GNSS station SAMO was 35.6 cm towards south and 3 cm towards west. A post-seismic signal (22–33% of the co-seismic on the vertical component) was observed at GNSS stations SAMO and SAMU, with a time constant of 30 days. The effects of the earthquake included liquefaction, rock falls, rock slides, road cracks and deep-seated landslides, all due to the strong ground motion and associated down-slope mobilization of soil cover and loose sediments. [ABSTRACT FROM AUTHOR]

Forecasting the slip behavior of a non-uniformly pressurized, heterogeneous creeping rock fracture, either aseismic creep or dynamic slip, is challenging based solely on laboratory and field measurements. Here we reported a simple, robust method to determine whether an aseismic creep is maintained or transitions to a dynamic slip during fluid injection. We reproduced the non-uniformly distributed fluid pressure and the resulting heterogenous aseismic creep on a critically stressed fracture and revealed the ratio of shear stress and frictional resistance corresponding to the fluid pressure front reaching or exceeding unity at the occurrence of dynamic slip. The determination of frictional resistance is based on the Mohr-Coulomb failure criterion with fluid pressure and friction coefficient on discrete segments of the fracture, and the length of fluid pressure front is calculated from hydraulic diffusivity and elapsed time. We used the experimental results of 9 shale fractures and 3 granite fractures to verify this method. We can also observe how the fluid pressure front propagates until the ratio of shear stress and frictional resistance approaches unity or is constrained with the ratio far below unity. This method has the potential for rapidly forecasting the injection-induced slip on a low-permeability rock fracture and simply characterizing the slip behavior of a natural, large-scale fracture during fluid injection. • The study reveals the fundamentals of aseismic creep transitioning to dynamic slip due to fluid injection. • A simple, robust method is developed to assess whether an aseismic creep is maintained or transitions to a dynamic slip. • This method rapidly forecasts injection-induced slip of a non-uniformly pressurized, heterogeneous creeping rock fracture. [ABSTRACT FROM AUTHOR]

The strength of rock under combined compression and shear loading has been paid more and more attention, but still lacks a theoretical model that incorporates both compression–shear characteristics and influence of dip angle to estimate the strength of the rock. This work is aiming to solve the issue by combining experimental and theoretical methods. First, in the laboratory, 112 rock samples with different sizes were applied to obtain the dip effect characteristics of strength via combined compression–shear tests. The ratio of compression–shear strength to uniaxial compression strength is called the compression–shear coefficient, which is used to characterize the degree of dip effect. Second, according to the compression–shear load characteristics of inclined rock samples, a strength model was established considering both compression–shear characteristics and dip angle by the Mohr–Coulomb failure theory. This strength model is an extension of the Mohr–Coulomb criterion and was verified by experimental data. The verification results are consistent with experimental results. Finally, the mechanism of dip effect on strength was explained from the resistance to the sliding and stress path of the rock sample. The results show that the dip effect is an inevitable strength weakening characteristic of rock materials under combined compression–shear loading. Compared with the vertical rock sample loaded under pure pressure, the resistance to the sliding of inclined rock samples decreases and the stress path is changed, which reduces the ability of the rock sample to resist external loads, resulting in the decrease of strength. [ABSTRACT FROM AUTHOR]

Costs for installation and maintenance of protective structures are increasing while alpine hazards progressively threaten alpine communities, infrastructure and economics. Thus, reliable process‐based anticipation and early warning strategies offer a cost‐effective and smart solution for alpine societies in the near future. However, only few comprehensive pre‐failure observations of alpine rock slopes have been reported so far. This paper demonstrates pre‐failure observations of a rapidly deforming rock mass (potentially 260,000 m3) at the Hochvogel (Allgäu Alps, 2,592 m a.s.l.) and a geotechnical monitoring and warning concept. This is implemented in the complementary multi‐method approach of the AlpSenseBench project and the basis for an effective and reliable early warning system. Since 2014, overall displacement rates in the range of 2 to 10 mm/month in the main decametre deep fracture are observed. It is expected that predictive acceleration patterns will appear in the final pre‐failure stage. A detailed knowledge of multiple anticipative signals in correlation with accelerating rock slope deformations will contribute to an advance in accuracy and reliability of rock slide early warning. [ABSTRACT FROM AUTHOR]

Rock is a heterogeneous material with primary damage and defects, which can greatly affect the mechanical properties of the rock and the slip on a fault. Additionally, slip on a fault can generate secondary damage in the surrounding rock. Therefore, this paper focuses on investigating injection-induced seismicity considering the heterogeneity and secondary damage in surrounding rocks with the FEM-based numerical code COMSOL. First, a heterogeneous model was established using the digital image processing technique, and the elemental microscale parameters were determined through comparison with testing results from a homogeneous model. Subsequently, using the defined damage variable and the rate and state friction law, numerical modeling was performed with the established homogeneous and heterogeneous models while considering the heterogeneity, fluid pressure, and generated secondary damage. The results showed that fluid pressure and heterogeneity can significantly influence injection-induced earthquakes. With increasing fluid pressure, the initial time for shear stress drop decreases, both the stress drop and the area of secondary damage increase, and the probability of unstable slip increases in a homogeneous rock matrix. Compared with the homogeneous numerical model, the heterogeneous model has a reduced time, a higher stress drop, a higher probability of seismicity, and a larger area of secondary damage. In addition, secondary damage is generated at two ends of the fault. The area of the secondary damage zone increases when unstable slip is induced, and the rate increases with slip velocity. The findings in this paper could facilitate better understanding of the mechanisms of fluid injection-induced seismicity and hence may be helpful for predicting, evaluating, and controlling induced seismicity. [ABSTRACT FROM AUTHOR]

The behavior of foliated rock masses presents challenging engineering issues. This paper presents the formulation of a constitutive model to simulate the behavior of foliated rock mass. The 3D elastoplastic constitutive model, called Comba, accounts for the presence of arbitrary orientations of weakness in a nonisotropic elastoplastic matrix. The paper presents simulation results for two example applications in rock mass engineering: the stability of a valley in foliated rock involving sliding and toppling mechanisms; and the analysis of the deformation of a dam foundation in columnar basalt. The analyses demonstrate aspects of the modeling capabilities of the Comba model for application to rock masses with tight multijoint sets in general, and with columnar basalt features in particular. [ABSTRACT FROM AUTHOR]

A rock bridge along the potential sliding surface of a rockslide has a relatively large bearing capacity and governs the stability of the rock slope. The physical and mechanical properties of specimens representing four rock bridge lengths were researched by direct shear experimentation. The micromechanism associated with the change in shear strength parameters was analyzed by PFC2D numerical simulations that corresponded to the experiments. The results revealed a rock bridge length effect, through which the peak shear strength increases with rock bridge shortening, accompanied by an increase in cohesion and a decrease in internal friction angle and main fracture surface roughness. Rock bridge shortening decreased the density of the microcracks at the shear stress peak point, changing the cohesive strength and frictional strength. The decrease in the internal friction angle could change the critical stress intensity factors to make shear cracks preferentially initiate over tensile cracks. Fracture roughness therefore decreased, inducing a lower residual shear strength. As a result, the difference in the peak and residual strengths increased with rock bridge shortening, which would promote brittle failure of the corresponding rock slope. [ABSTRACT FROM AUTHOR]

In this work, a geomechanical study performed on a natural rock slope located in north-eastern Italy (Tagliamento River valley, Friuli Venezia Giulia Region) is presented. The detailed geomechanical survey has provided a large bulk of field data proving that the investigated limestone slope is characterized by strong rock mass damage, thus resulting in a critical stability condition. Field evidence includes: (1) local faults crossing the rock mass and representing internal sliding surfaces; (2) slickensides and fault slips within the rock mass; (3) fracture joints of gravity-induced origin; (4) strong rock mass damage in over-stressed zones of the slope; and (5) slope monitoring data recorded by some installed devices. Three failure scenarios have been identified: a wedge failure involving a limestone block of 110,000 m3 (failure scenario 1: BLOCK1); a larger wedge failure involving an assembled limestone block of 200,000 m3 (failure scenario 2: BLOCK1-2-3); and a retrogressive failure involving a rear dolomitic block possibly triggered by the collapse of the limestone slope, mobilizing a maximum volume of 335,000 m3 (failure scenario 3: DOLOMITIC BLOCK). This paper shows that to comprehensively study stability problems involving natural rock slopes we must consider the interaction between pre-existing discontinuities, internal sub-blocks subdividing the unstable slope, rock mass strength and gravity-induced fractures that form during the delicate phase preceding slope collapse. Gravity-induced joints can be differentiated on the field from those of tectonic origin on the basis of some geometrical features, in particular their lower persistence and higher joint roughness. [ABSTRACT FROM AUTHOR]

Scour of rock is a challenging and interesting problem that combines rock mechanics and hydraulics of turbulent flow. On a practical level, rock erosion is a critical issue facing many of the world's dams at which excessive scour of the dam foundation or spillway can compromise the stability of the dam resulting in significant remediation costs, if not direct personal property damage or even loss of life. This interaction between the blocky rock mass and water is analyzed by directly modeling the solid and fluid phases—the individual polyhedral blocks are modeled using the discrete element method (DEM) while water is modeled using the lattice Boltzmann method (LBM). The LBM mesh is entirely independent of the DEM discretization, making it possible to refine the LBM mesh such that transient and varied fluid pressures acting on the rock surfaces are directly modeled. This provides the capability to investigate the effect of water pressure inside the fractured rock mass, along potential sliding planes, and can be extended to rock falls and slides into standing bodies of water such as lakes and reservoirs. Results show that the coupled DEM–LBM implementation is able to accurately capture the interaction between polyhedral rock blocks and fluid by analytically solving for the solid volume fraction in the coupling computations using convex optimization and simplex integration; however, further performance improvements are necessary to simulate realistic, field-scale problems. Particularly, adaptive mesh refinement and multigrid methods implemented in a parallel computing environment will be essential for capturing the highly computationally intensive and multiscale nature of rock–fluid interaction. [ABSTRACT FROM AUTHOR]

The coal wall and floor of the longwall face in the steeply inclined coal seam are prone to damage, which seriously affects the advance of the working face.By establishing theoretical model, bottom friction experiments, numerical calculations, etc., the characteristics of coal seam roof breaking and caving rock sliding are studied, and the coal wall failure mechanism under different coal seam occurrence and mining conditions is revealed. The concrete measures to prevent coal wall damage and floor slip are put forward.The study shows that the caving rock from the roof of the longwall face in steeply inclined coal seams will form different degrees of filling in the goaf. From bottom to top, it forms three sections including "compact filling section", "uneven filling section"and "non-filling section".However, due to insufficient filling in the upper part of the working face, the dynamic pressure phenomenon is obvious, which is likely to cause serious coal wall slab and bottom plate slip phenomenon, and the working condition of the support will also become worse, which becomes the most unstable surrounding rock of the whole working face.The fragile area seriously affects the safe and efficient production of the working face, and is the key area for the surrounding rock control of the working face.The stability of the working floor is significantly affected by the stability of the coal wall.In actual production, it is found that when the coal seam occurrence and mining conditions are different, the coal wall failure generally presents three failure modes: "plastic-flow", "extrusion-slip"and "shear-slip".The use of a pseudo-tilt arrangement at the working face not only can significantly improve the stability of the coal wall and the bottom plate, but also effectively prevent the hydraulic support from falling and sliding, and can also avoid the occurrence of flying gangue at the working face.With the integration of conveyor and the "flexible reinforced coal wall", it is possible to realize the safe and efficient mining of longwall working face in steep coal seam, and effectively solve a series of rock formation control problems faced by the mechanized mining of steep coal seam. [ABSTRACT FROM AUTHOR]

Rock burst mitigation and monitoring is a challenge during deep coal mining. Theoretical analysis, numerical simulation, laboratory tests and field monitoring are all used for researching this issue. First, the occurrence mechanisms of three types of rock burst(i. e. , strain rock burst, fault slip rock burst and hard roof rock burst) are researched. Second, two new burst liability indexes are proposed to improve the evaluation system of burst liability, which makes theburst liability evaluation system more suitable for deep coal mining. Third, the precursor information characteristics of the three rock burst types are given. Forth, the corresponding monitoring-warning and combined pressure relief methods are proposed. At last, synchronization technique of drilling and monitoring is developed. Main conclusions are as follows:(1) Deep strain rock burst is the result that the energy accumulation of surrounding rock system is larger than that of superposition of energy release and energy dissipation. Compared with shallow mining, the released energy of deep hard roof fracturing increases and deep fault slips more easily. (2) When evaluating burst liability of deep strain rock burst and hard roof rock burst, burst energy speed indexes of unloading confining pressure and combined coal-rock need to be added except the national standard, respectively. For deep fault slip rock burst, the two new indexes are all need to be added. (3) Monitoring and warning of deep strain rock burst and deep hard rock burst should depend on energy and stress criteria, while for deep fault slip rock burst, energy criterion is the priority. (4) Priorities for mitigating deep strain rock burst are protective seam mining, large-diameter drilling, floor fracturing and water infusion. Priorities for hard roof rock burst are protective seam mining, roof fracturing, large-diameter drilling, floor fracturing and water infusion. Priorities for fault slip rock burst are protective seam mining, large-diameter drilling and water infusion. (5)When using the synchronization technique of drilling and monitoring, drilling powder and stress change can be monitored for potential burst warning during drilling process. System establishment of control technique based on scientific classification still will be the direction of future research. [ABSTRACT FROM AUTHOR]

The goal of this paper is to evaluate the post-failure behavior of the Hsien-du-shan rock avalanche, which was triggered by Typhoon Morakot in 2009, using a three-dimensional (3D) discrete element program, namely, 3DEC. The 3D slope topography and local joint sets are explicitly considered in the calculations, and the joint sets cut the sliding rock mass into blocks with arbitrary shapes. The modeled blocks exhibit the elastic behavior of the local rocks. The analysis successfully simulates the wedge failure at the initiation of the landslide. Additionally, the 3DEC results clarify the local rock sliding phenomena at the boundaries of the source area. The simulated depositional area correlates well with the actual area affected by the Hsien-du-shan rock avalanche. In addition, the erosion of a ridge by the sliding rock near the southwestern margin of the area at an elevation of 590 m has a significant influence on the shape and size of the impacted area. The interlocking effect between blocks is also considered. [ABSTRACT FROM AUTHOR]

Subsurface reservoirs are generally highly fractured, whereby fractures constitute a natural fluid flow path and define the preferential flow direction. Slip accumulated during the faulting process alters also the petrophysical properties of the host rock. Although the mechanical alteration of the host rock, and related porosity and permeability changes, due to fault slip has been previously described, a predictive physics-based model has not been scaled with fault length in reservoirs to provide an initial porosity permeability alteration model yet. In this study, we develop a predictive model to quantify how accumulated fault slip changes porosity and permeability in a porous medium, by combining deformation modeling based on triangular dislocations and linearized poro-elasticity equations. We applied our model the Ghawar field fault map and rock-types. We conducted a Monte-Carlo simulation, varying fault roughness and accumulated slip, to quantify the corresponding variation in porosity and permeability using a 5 km long strike-slip fault and three different rock-types. Our Monte-Carlo simulation shows that long-term accumulated slip on rough strike-slip fault surfaces change porosity by ± 1 % , leading to an absolute permeability change of up to 22.5%. We further used these results as a benchmark for the elastic response of porous rocks to accumulated slip scaled to certain fault length. Using these benchmark results for Ghawar field reservoir rocks, we determined the slip-related porous medium permeability changes for every fault on the Ghawar fault map, accounting for their length, location, and orientation. In doing so, we found that fault roughness, slip amount, and shear sense all affect the medium's permeability, creating substantial permeability anisotropies. Locally, these anisotropies are further enhanced by superposition of permeability changes of individual faults that constitute the fault system. We suggest the resulting permeability distribution model should be used as the initial permeability model for porous media in fractured reservoirs. • Host rock deformation due to fracture growth by recurrent slip. • Coupling the linearized equations of triangular dislocation and poro-elasticity. • Assessing the effects of roughness on porous rock deformation. • Monte Carlo simulation on parameter space of fault and rock properties. • Benchmarking the deformation and scaling it up to fault networks in geo-reservoirs. [ABSTRACT FROM AUTHOR]

The Ötz Valley and adjacent regions in Tyrol (Austria) have been repeatedly affected by large rockslope failures following deglaciation. Six rockslides, each over 10 7  m 3 in volume, were emplaced into the Ötz and Inn valleys, five of which formed persistent rockslide dams. Even though catastrophic rockslope failures are short-lived events (commonly minutes) they can have long-lasting impacts on the landscape. For example, large fans have built in the Ötz Valley and knickpoints persist at the former dam sites even though the Ötz River has eroded through the deposits during the past thousands of years; exact age-constraints of rockslide dam failure, however, are still scarce. Empirical, geomorphic stability indices from the literature successfully identified the least and the most stable dams of this group, whereas the rest remain inconclusive with some indices variably placing the dams in the stable, unstable, and uncertain categories. This shows (a) that further index calibrations and (b) better age constraints on dam formation and failure are needed, and (c) that the exact processes of dam failure are not always trivial to pinpoint for ancient (partially) breached dams. This study is a contribution towards better constraining the nature and landscape impact of dam formation following large rockslope failures. [ABSTRACT FROM AUTHOR]

Landslides are common phenomena in mountainous regions worldwide. Over the past two decades, catastrophic rockslides in mountainous regions have caused serious damage and fatalities. To develop effective preventive countermeasures, it is important to estimate the kinematic behavior of displaced masses after slope failures, such as the velocity, run-out distance, and extent. Discontinuous deformation analysis (DDA) is an appropriate tool to analyze the dynamics, kinematics, and deformability of a block assembly. Many studies have reported applications of DDA to kinematic analyses of rockslides on two-dimensional (2-D) terrain. However, because of the restrictions of numerical techniques, few kinematic analyses of rockslides on three-dimensional (3-D) terrain have been performed using DDA. This study developed a new DDA model for the analysis of rockslides on 3-D terrain. First, contact treatment techniques for the 3-D model were developed to create an accurate and efficient computational scheme. The new model was then verified by the benchmark tests on the four basic types of block motion on 3-D terrain. Finally, the new model was applied to a designed rockslide with complex terrain to demonstrate its practical applicability. The results indicate that the new 3-D DDA model is an effective tool to analyze 3-D rockslides and could potentially be used to optimize protection designs for rockslides. [ABSTRACT FROM AUTHOR]

This study investigates the predisposing geological and anthropogenic factors and indicative precursors preceding the fatal 5 June 2009 Jiweishan rock avalanche. It began as a rockslide and transformed into a rock avalanche that killed 74 people and caused major property loss due to misdiagnosis of the failure mode, and underestimation of volume and travel distance. Besides topography, structure and stratigraphy that favoured failure, mining below the failed rock mass had changed the state of stress and altered groundwater flow. The anthropogenic factors caused deformation and accelerated failure of the slope, and therefore were important contributions. Cracks and a karstic zone had developed along regional joints and defined several boundaries of the failed rock mass. Furthermore, a 2-m-wide crack developed since 1958 revealed a potential basal failure surface at the contact between karstic limestone and an underlying pre-sheared thin shale aquiclude. Increasing magnitude and frequency of rockfalls and tension cracks at the front end of the sliding block appeared three days before the event and implied the likely movement direction of the sliding rock mass. These could have warned of a developing giant failure. Topography included a large elevation difference between the toe of the failure surface and the cliff base, a narrow valley to channel debris, and the steep gradient of the downstream Tiekuang Creek, could have suggested that failure might lead to a rapid and long-runout rock avalanche. However, access to the densely vegetated source area before the failure was difficult, and local investigators did not have all of the evidence that might have led them to recognize that potential danger was more than continuing rockfalls. [ABSTRACT FROM AUTHOR]

In mountain ranges deep-seated gravitational slope deformations (DSGSDs) and extremely rapid mass wastings of rock > 10 5 m 3 in volume (catastrophic rock-slope failures, CRF) are present, yet their mutual relation is poorly documented. Near the Brenner Pass (1370 m asl) in the eastern Alps, five catastrophic rock-slope failures of medium- to high-grade metamorphites are clustered (‘Brenner Pass Cluster’; BPC), and three of them are related to DSGSDs. The catastrophic rock-slope failures involved volumes from 12 to 110 Mm 3 and show fahrboeschung angles of 10–27°. Numerical dating ( 14 C, 234 U/ 230 Th) suggests that all catastrophic slope failures of the BPC occurred between ≤ 13.5 and 6.2 ka. Three of the CRF events may have occurred during the Younger Dryas (12.7–11.7 ka), whereas two events occurred during the Holocene. Backwater basins dammed up by the CRFs range from 2.5 km 2 (Ridnaun rock avalanche) to 15.5 km 2 (Stilfes rock avalanche). Three of the catastrophic rock-slope failures are associated with and developed as a partial failure of a DSGSD. This suggests that progressively slow deformation of slopes ultimately exceeded a stability threshold, resulting in catastrophic rock-slope failures. The initial kinematic mechanisms of failure vary between large-scale toppling, wedge sliding, and planar sliding and are strongly controlled by the structural setting of the slopes. A direct connection of catastrophic mass wasting with specific palaeoclimatic conditions (e.g., phases of enhanced precipitation) is not indicated; however, this does not exclude specific meteorological situations (e.g., occurrence of short-term heavy rainfall) that may have expedited slope instability and perhaps even triggered catastrophic events. Attempts to correlate catastrophic rock-slope failures with specific palaeoclimatic regimes are still encumbered by substantial methodical uncertainties and imprecisions as well as the scarcity of dated CRF events. The mapped distribution of CRFs unequivocally indicates that structural predisposition is the most significant long-term control in forming CRF clusters. [ABSTRACT FROM AUTHOR]

• The damage and failure process of roadway in deep inclined rock strata was reproduced based on both physical model test and numerical simulation. • The effect of rock mass structure and ground stress on the damage and failure of roadway in deep inclined rock strata was clarified. • The support suggestions for roadways in deep inclined rock strata were put forward. Underground engineering excavation can lead to sharp stress change in the rock mass around the excavation surface, which can cause different degrees of rock damage, ultimately resulting in instability failure. Especially for inclined stratified rock mass that is ubiquitous on Earth, the evolution characteristics, development law and formation mechanism of an excavation damage zone are highly complicated due to its significant asymmetry. Therefore, the evolution mechanism and deformation failure properties of a typical deep roadway in inclined rock strata in Jinchuan Mine of China were investigated by means of a field investigation, theoretical analysis, similar model test and numerical simulation. The results indicate that the deformation failure of a roadway in deep inclined rock strata shows a prominent asymmetry and time sequence. Ground stress has a great influence on the development mode and evolution characteristics of the surrounding rock damage zone. However, as a deep ground stress environment tends to cause hydrostatic pressure, its leading role is gradually weakened. The structural planes control the damage evolution mode of the surrounding rock, an excavation damage zone developed parallel to the interface is formed around the goaf, and an overall instability of the roadway is caused by the sliding of surrounding rock along the structural plane. The conclusions of this study should provide a theoretical reference and demonstrate the key technologies that support underground engineering under similar geological conditions. [ABSTRACT FROM AUTHOR]

It is well known that satellite radar interferometry (InSAR) is capable of measuring surface displacement with a typical accuracy on the order of millimeters to centimeters. However, when the true deformation vector differs from the satellite line-of-sight (LOS), the sensitivity decreases and interpretation of InSAR deformation measurements becomes challenging. By combining displacement data from extensive ascending and descending TerraSAR-X datasets collected during the summer seasons of 2009–2014, we estimate two-dimensional (2D) InSAR surface displacement. Displacement data are decomposed into vertical and west/east deformation, dip and combined deformation vector, and validated using Global Navigation Satellite System (GNSS) data. We use the decomposed dataset to visualize variations in surface velocity and direction on unstable slopes in a periglacial environment with sporadic permafrost in northern Norway. By identifying areas with uplift and subsidence, and detecting velocity changes (downslope acceleration/deceleration) and related areas of extension and compression, we are able to explain driving and controlling mechanisms and geomorphology in two rockslides and one area with solifluction landforms. [ABSTRACT FROM AUTHOR]

Movements, instability and failures in open pit mines can pose important geotechnical problems, leading to major impacts on the safety of personnel and the mining operations. In particular, large slope scale rockslides represent a significant challenge, as these types of instabilities require accurate observations and monitoring. However, in many cases engineers can only rely on surface displacements for their interpretation of the failure mechanism because there is no information on the extension of the deformation into the slope. More recently, several attempts have been made to monitor the volume of rock of unstable slope in open pit and natural slopes, using the microseismic technique. Nevertheless, the link between ground deformations, failure mechanism and microseismic data was rarely addressed in the details of these studies. In this paper, a case study of the SW Wall instability at Century mine (Queensland, Australia) is discussed. Since 2009, the pit wall has been affected by several multi-batter failures, associated with continuous bedding planes. Geotechnical investigations, supported by numerical modelling, have interpreted those instabilities as potential development of deep-seated failure. Consequently, in early 2013, the slope angle at the base of the slope was reduced and a buttress was left to avoid further progression of the instability into the lower section of the wall. Slope performance while mining has been primarily managed through surface monitoring (geodetic prisms and ground-based radar). However, as there were still concerns, a microseismic monitoring program was proposed by MMG geotechnical personnel and subsequently implemented. Our work integrated the approaches, analysing both ground deformation and microseismic data in order to reach a more complete understanding of rock damage at depth and mechanisms of instability. [ABSTRACT FROM AUTHOR]

Chemical corrosion of rock masses commonly exists in natural environment (e.g., rock masses immersed in acidic groundwater) and in rock engineering practice (e.g., acid fluid injection in unconventional reservoirs). Rock fractures as the primary paths for fluid flow are susceptible to the chemical treatment, which may lead to geologic hazards (e.g., induced landslides and earthquakes). Here we show the transitional behaviors of rock fractures between stick-slip and stable sliding due to the chemical corrosion, which is characterized by a sequence of fast rupture followed by one or more slow ruptures. The chemical corrosion also modifies the frictional properties of rock fractures, in terms of friction rate parameters, characteristic weakening distance, stiffness ratio, and frictional property ratio. Our results indicate that the chemical corrosion essentially reduces the critical stiffness of the fracture and makes it approach the stiffness of the loading system, resulting in the occurrence of slip transition. The slip transition is strongly influenced by treatment duration and shear process, and the real area of contact density is a physical control linking fracture surface topography and frictional responses, such as AE energy and shear stress drop. The understanding of slip transition can improve our ability to interpret the seismic data and to predict the slip behaviors. • Slip transition of rock fractures occurs between stick-slip and stable sliding due to chemical corrosion. • Slip transition of rock fractures is strongly influenced by chemical treatment duration and fracture shear process. • Real area of contact density is a physical control linking fracture surface topography and frictional responses. [ABSTRACT FROM AUTHOR]

Soil-rock-mixture (SRM) slopes widely exist, and their failure may cause serious damage to infrastructures and endanger human lives. Thus, it is important to study the mechanical behaviors of SRM slopes. Analyzing these behaviors is complicated and typically involves soil-rock-structure interactions. Fortunately, numerical methods can provide adequate descriptions of these behaviors. Discontinuous deformation analysis (DDA) is a powerful method that can be used to simulate the behavior of solid blocks, including rocks and structures. Smoothed particle hydrodynamics (SPH) can effectively simulate the behavior of fluid flows and soil materials. To take advantage of both methods, the coupling of DDA and SPH is investigated in this study, where the coupled DDA-SPH method is used to study the mechanical behaviors of SRM slopes. Two verification tests are investigated to demonstrate the accurate calculation of the interaction force and impact force using the coupled method. A series of simulations are then performed considering different shapes, sizes and contents of rocks and their distributions in SRM slopes. Results show that the deformation of the SRM slope is proportional to the roundness but inversely proportional to the sorting coefficient of the rock blocks. Additionally, the deformation of the SRM slope with rocks distributed along the potential sliding surface is much smaller than that with rocks distributed in the sliding body. In addition, the runout distance of an SRM landslide and the maximum impact force on nearby buildings increase with higher rock contents, which is more destructive to nearby structures and human lives. • Applied coupled DDA-SPH method to study SRM slopes. • Developed a technique to easily generate SRM slope models. • Validated coupled method for impact force calculation. • Investigated effects of rock features in SRM slopes. [ABSTRACT FROM AUTHOR]

High temperatures lead to thermal fracture in the rock, which can greatly impair the rock's mechanical properties. During Jiweishan landslide, rocks on the sliding surface generate high temperatures due to frictional heating. Studies on thermal fracture during landslides and its influence on the sliding process are unclear. Here we use thermogravimetry and dilatometry to study the thermal expansion and thermal fracture of the rocks at the base of the 2009 Jiweishan landslide. Experimental results show that rocks generate a large number of thermal fractures and thermal expansion while reaching temperatures of up to 827.3 °C. The generation of CO 2 gas also significantly produces and promotes thermal fractures. This indicates that the rapid heating process during the Jiweishan landslide could have caused thermal fractures on the sliding surface during the landslide, which could have then weakened the mechanical properties of the rock, making the sliding surface more susceptible to entrainment. As a result, the sliding surface lost frictional resistance during the landslide, resulting in a faster sliding velocity and a longer sliding distance. In addition, we infer that thermal fracture is beneficial for CO 2 gas to be released from the rock and enter the sliding zone, which may produce pore pressure, reduce the effective normal stress on the sliding surface, and which also contributes to the lubrication. • Sudden increase of the coefficient of linear thermal expansion is result of thermal fracture. • The generation of CO 2 gas can cause thermal fracture. • Thermal fracture contributed to lubrication in the Jiweishan landslide. [ABSTRACT FROM AUTHOR]

Uplifting mountains are denudated by gravitational deformation, landslides, and glacial or fluvial erosion. We investigated the response of valley slopes to glacial and fluvial erosion along the Kali Gandaki (KG) River, one of the largest rivers that flows through the High Himalaya southward from Tibet to India and diagonally cuts the strikes of gneiss and slate foliations. Satellite images with 2.5 m resolution and 5-m Digital Elevation Models (DEMs) were used for the investigation. Within a 20-km reach of the KG River, we found a series of 11 landslides, which vary from a total area of 0.58 to 12 million m2 each. The foliations generally strike NW–SE and dip at 30° to 50° to the NE, so the left bank slopes are anaclinal and the right bank slopes are cataclinal. On the cataclinal slopes, buckling of beds occurs, and gradual deformation proceeds in slate and two-mica gneiss, while in the more competent calc gneiss, buckling deformation develops into a rock avalanche. Such rock avalanches are represented by the largest Dhampu-Chhoya landslide, which once blocked the KG River and drastically changed the river morphology. Anaclinal slopes of two-mica gneiss were toppled and transformed into rock avalanches on three slopes. The KG River has a prominent fluvial knickpoint, which is currently at an elevation of 1800 m, and it has slope breaks on the left bank that are 200–400 m above the riverbed downstream of the knickpoint. Toppling was observed on slopes higher than slope breaks, which suggests that toppling began before the formation of slope breaks by fluvial incision and that the lower slopes did not adapt to the younger fluvial incision. In contrast, slope breaks are scarcely found on the right bank, probably because slow-moving DGSDs, which followed the river incision, erased them. • The Himalayan mountains respond to erosion based on geological structures. • Buckling and gradual deformation proceed on dip slopes of incompetent rock. • Buckling of competent rock develops into catastrophic failure. • On anaclinal slopes, toppling and catastrophic failure occur. • Upstream migration of a fluvial knickpoint induced a series of mass movements. • Glacial erosion and deglaciation destabilized the feet of dip slopes, inducing buckling deformation. [ABSTRACT FROM AUTHOR]

Knowledge about the detailed processes linked to the existence of permafrost in rockslide fractures is sparse. Large parts of the Jettan rockslide are located right below the discontinuous permafrost limit in the arctic part of the alpine landscape of northern Norway. Combining four years of meteorological and rockslide deformation data with temperature measurements from different parts of open fractures, shallow bedrock boreholes and air, as well as daily snow cover observations, allows a detailed identification of the key processes involved. These field data are the basis for the development of a permafrost controlled rockslide model. Seasonally, the deformation has a very distinctive pattern with high deformation starting abruptly right after snowmelt in May, and lasting until snow isolation in winter. Then there is a gradual transition to medium deformation as the ground is cooled further for another 1–2months. Finally, the winter period, when maximum snow occurs in the fractures, is characterized by limited or almost no deformation. The primary controlling deformation process is meltwater percolation into fractures in summer with significant refreezing, ice formation and temperature increase in the lower part of the fractures from −1°C to 0°C. Sporadic permafrost exists below the discontinuous permafrost limit, and may extend into open fractures and sliding planes. Another primary process is the significant cold air accumulation in fractures in early winter, due to the Balch effect, which significantly cools the fracture and surrounding rock promoting permafrost development. Finally, the cold air effect is stopped by snow isolation once enough snow has accumulated in the fracture by late winter. The deformation itself is thought to be controlled by changing shear strength of the brecciated sliding planes due to either changing ice temperatures and/or variations in water infiltration to the unsaturated sliding zones. The overall system is very locally controlled driving itself, and the effect of a future climate change can thus be of minor importance. [ABSTRACT FROM AUTHOR]

The slow movement of active deep-seated slope gravitational deformations (DSGSDs) and deep-seated rockslides can cause damage to structures and infrastructures. We use Permanent Scatterers Synthetic Aperture Radar Interferometry (PSInSAR™) displacement rate data for the analysis of DSGSD/rockslide activity and kinematics and for the analysis of damage to buildings. We surveyed the degree of damage to buildings directly in the field, and we tried to correlate it with the superficial displacement rate obtained by the PSInSAR™ technique at seven sites. Overall, we observe that the degree of damage increases with increasing displacement rate, but this trend shows a large dispersion that can be due to different causes, including: the uncertainty in the attribution of the degree of damage for buildings presenting wall coatings; the complexity of the deformation for large phenomena with different materials and subjected to differential behavior within the displaced mass; the absence of differential superficial movements in buildings, due to the large size of the investigated phenomena; and the different types of buildings and their position along the slope or relative to landslide portions. [ABSTRACT FROM AUTHOR]

Abstract: The Aresawa rockslide in the Japanese Alps, which partially collapsed in May 2004, produced a number of new tension cracks in the head area. This paper discusses the dynamics of the rock slope and controls on the surface velocity, based on the results of on-site monitoring of the surface movement and meteorological parameters (air and ground surface temperatures, precipitation and snow depth). The rock mass deformation progressed at ca. 60cmyr−1 mainly along a slip plane dipping downslope at ca. 50°. The surface velocity of the slipping rock mass showed a significant seasonal variation in response to the water infiltration. The velocity was small (≤1mmday−1) in winter. Subzero air temperatures and a heat-insulating snow cover, and resulting growth of seasonal frost, prevent water infiltration into the bedrock and contribute to the rock slope stability. Most of the movement in this period is attributed to gravitational deformation originating from the overburden pressure. In contrast, the surface velocity increased (up to 10mmday−1) during snow-melting and snow-free periods. Snowmelt and rainfalls promote water infiltration into the bedrock, destabilizing the rock slope and accelerating the rock slip. Such a rapid movement is attributed to water-induced sliding superimposed on gravitational deformation. [ABSTRACT FROM AUTHOR]

Abstract: In this paper, we present a structurally controlled, deep-seated, gravitational slope deformation, located in the Fusch Valley, Eastern Alps, Austria, which is potentially endangering infrastructure. In the framework of a landslide risk analysis, a danger characterisation of this slope is presented. The characterisation is based on strong geomorphological, geological, and hydrological evidence, on which both a kinematical and a stability model of that slope could be developed. Unlike the majority of case studies where type and position of basal slip surfaces remain unknown, the present models seem capable of delivering characterisations on the classification of the potential slope instability, its spatial extents, and likely physical reasons for its pre and post failure behaviour with high consistency and likelihood. [Copyright &y& Elsevier]

Abstract: The monitoring of slope displacements over time provides the basis for most rockslide early warning systems, yet the prediction of catastrophic failure from these records is highly problematic and tenuous, especially if the underlying kinematics and instability mechanism are poorly understood. An example is the moving slope above the town of Randa in the Swiss Alps. This slope is considered typical of those in crystalline rock that lacks a natural, highly persistent, weakness plane dipping towards the valley that can serve as a through-going detachment surface for kinematic release. In Part I (the companion paper to this), the findings from a comprehensive geological and geophysical investigation to image the internal structures of the unstable rock mass were presented. In this paper we develop a kinematic model that describes the pattern of displacement vectors for the rock mass along these structures, both on surface and at depth. The displacements were estimated from 5 years of data from an extensive monitoring system which included surface geodetic and crackmeter measurements, borehole inclinometer and extensometer measurements (up to 120 m depth), and microseismicity. The results showed that the displacement field is highly heterogeneous. Internal deformation is accommodated by both shear and opening-mode dislocation of faults and fracture zones which dip moderately to steeply into the slope. Microseismicity is most intense near the front of the scarp where surface translation in large part reflects the toppling of blocks accommodated by slip along the steeper dipping fractures. The small displacement rates at the study site of up to 2 cm/year coupled with a modest deviation of up to 15° from vertical of the boreholes posed severe problems for the estimation of horizontal displacements from the inclinometer data. We describe the error analysis of these data in some detail since it is relevant for similar installations elsewhere. Conclusions drawn from this work highlight the importance of integrating various types of data in order to better understand the complex block-kinematic processes whose evolution governs the long-term progressive failure of unstable rock slopes. [Copyright &y& Elsevier]

Abstract: In 1991, the steep slope above the village of Randa in southern Switzerland failed during two successive rockslide events three weeks apart. The failures, which resulted in the release of approximately 30×106 m3 of material, occurred in fractured gneissic rock whose principal foliation, faults and fracture zones dip into the slope. Above the scarp of the second rockslide, the mountain continues to move at rates of up to 2 cm/year. In an attempt to understand failure mechanisms in fractured crystalline rock masses, we have carried out a comprehensive multidisciplinary study that included detailed geological mapping, borehole logging and imaging, and surface and borehole geophysical surveys. An integrated interpretation of the resultant data has revealed the presence of three prominent fault- and fracture zone sets that define the internal structure of the rock mass. Some faults and fracture zones could be traced up to 85 m into the subsurface using borehole radar reflection methods. The dips of the faults and fracture zones estimated from surface mapping matched those from radar reflection and borehole televiewer surveys. No evidence was found for significant faults or persistent weakness planes that paralleled the 1991 rockslide failure surfaces. Instead, the new observations were consistent with dominant failure mechanisms that involve the progressive development of major shear and brittle fracture zones and the eventual destruction of intact rock bridges immediately prior to catastrophic collapse. This integrated study provides the first reliable model of the 3-D fault structure associated with and contributing to a large rock slope instability in a brittle crystalline rock mass. [Copyright &y& Elsevier]

Based on a study of 45 large slow-moving landslides, it is apparent that for a landslide to travel slowly after failure, the sliding is most likely to be active or reactivated, on a basal rupture surface at or close to residual strength. The likelihood of slow movement after failure is also increased when the inclination of the basal rupture surface is less than the residual friction angle. The slow-moving landslides are all of low rock-mass strength with varying degrees of disaggregation, or they possess soil strength. The influence of lateral margins on landslide restraint is generally small, with landslide movement typically controlled by fluctuations in piezometric pressure. The most commonly observed slow large landslides are mudslides and translational debris–rock slides, followed by particular forms of translational rock slides and internally sheared compound slides. Some mudslides display evidence of short periods of up to moderate velocities. Sur la base d’une étude de 45 grands glissements à mouvement lent, il appert que pour qu’un glissement bouge lentement après rupture, le glissement doit être actif ou réactivé sur une surface de rupture à la base qui soit à la ou près de la résistance résiduelle. La probabilité d’un mouvement lent après rupture augmente aussi là où l’inclinaison de la surface de rupture à la base est inférieure à l’angle de frottement résiduel. Les glissements lents sont tous d’une faible résistance de masse de la roche avec différents degrés de désagrégation, ou ont une résistance de sol. L’influence des marges latérales pour contenir le glissement est généralement faible, alors que le mouvement du glissement est typiquement contrôlé par des fluctuations dans la pression interstitielle. Les grands glissements lents les plus communément observés sont des glissements de vase et les glissements par translation des débris/roches et les glissements composés par suite de cisaillements internes. Certains glissements de vase montrent une évidence de périodes courtes de vélocité allant jusqu’à modérée. [ABSTRACT FROM AUTHOR]

This study presents a multi-disciplinary approach for combining geological-geomorphological field mapping with different surface deformation monitoring techniques (i.e. extensometer, tachymetry, photogrammetry, airborne laser scanning (ALS), terrestrial laser scanning (TLS), uncrewed aerial vehicle (UAV)) to evaluate the impact of structural features on the formation process and deformation behaviour of the deep-seated Marzellkamm rock compound slide. The investigated rock slide is located in a high-alpine, glacier retreat environment in Northern Tyrol (Ötztal Alps, Austria) and formed in a well-foliated, fractured metamorphic rock mass. The total volume of the rock slide of approximately 13 Mm3 was estimated based on geographic information system (GIS) analysis by comparing the surface topography and reconstructed geometry of the basal shear zone. In the upper part of the rock slide, annual mean velocities of up to 0.3 m/year were measured by a combined tachymetric-global navigation satellite system (GNSS) procedure. Based on multi-temporal terrain model analyses, the highest sliding velocities were obtained at the central slope foot area, reaching more than 1 m/year. Geological-geomorphological field mapping showed that the rock slide can be subdivided into two large rock slide systems with different geometry, formation age, and current activity. Furthermore, structural and geomorphological features (i.e. main and minor scarps, graben-structures, downhill- and uphill-facing scarps, tensile fractures, trenches), as well as surface deformation data, indicate the formation of six rock slide slabs. These slabs move downwards at different velocities and are separated by discrete shear zones, where slope displacement primarily accumulates. Large offsets along these shear zones indicate that internal slab deformation has only limited influence on the overall rock slide behaviour. At the Marzellkamm rock slide, pre-existing tectonic fault zones and planes were reactivated and used as weakness zones, playing a crucial role in the overall rock slide geometry and internal separation of the rock mass into slabs. Field survey and monitoring data suggest that a fully persistent, curved, non-circular basal shear zone has developed. Based on comprehensive analyses of mapping and deformation monitoring data, a geological-geometrical and kinematical model of the Marzellkamm rock slide was developed, providing a basis for site-specific hazard assessment and numerical modelling. • Two rock slide systems of six rock slide slabs of different deformation behaviour • Significant influence of pre-existing geological structures on rock slide formation • Deformation is controlled by the magnitude of shearing on separating shear zones. • Field survey indicates a fully persistent, curved, non-circular basal shear zone. • Two rock fall/avalanche events occurred at the lower part of the most active slabs. [ABSTRACT FROM AUTHOR]

To simulate the entire process of the progressive failure of rock slopes, a series of techniques are incorporated into the original NMM (numerical manifold method). To reflect the stress concentration near the crack tip, the Williams' displacement series is adopted to enrich the global displacement function of the NMM. Furthermore, the most recently proposed strength-based LT criterion, which can account for tensile cracks, tensile-shear cracks and compressive-shear cracks, is adopted to determine the crack propagation direction and length. Three typical numerical examples, including a Mode-I crack problem, a Mode-II crack problem and a Brazilian disc problem are adopted to verify the numerical model. The numerical results indicate that the numerical model is capable of accurately simulating the Mode-I crack propagation problem, the mode-II crack propagation problem and the failure process of Brazilian disc. Furthermore, the numerical model is adopted to investigate the entire progressive failure process of two rock slopes. The corresponding results indicate that the numerical model can not only simulate the propagation and coalescence of multiple cracks in rock masses but also the opening/sliding of rock blocks along discontinuities. The proposed numerical model warrants further investigation. [ABSTRACT FROM AUTHOR]

Glacier retreat is one of the most significant consequences of 20th and 21st century temperature rise in the European Alps, most obvious at glacier tongues but also at glacier cirques. As cirque headwalls deglaciate, internal stress redistribution occurs and atmospheric forcing intensifies rendering deglaciating headwalls particularly prone to rock slope failure. Fractures intersecting these rock masses represent potential planes of weakness. Their dynamics may thus reveal information about the magnitude and timing of stability-relevant processes. The present study focuses on the need for quantitative data from unstable, recently deglaciated rock slopes, essential for better understanding the increasing risk on high-alpine infrastructure.Here, we investigate the deformation regime of an open fracture, which is of direct geotechnical relevance for a popular cable car station at the Kitzsteinhorn (3203 m a.s.l.). The fracture is situated immediately up slope of the detachment zone of a recent rock slide (2012) and was glacially covered until the 1980s. Two crackmeters are operated to measure horizontal and vertical crack deformation with a resolution of ±0.003 mm as well as crack top temperature. To decipher thermo-mechanical from cryogenic forcing, thermal expansion coefficients for both horizontal and vertical directions were calculated in order to model purely thermomechanical deformation. Based on a 2.5-year monitoring campaign, this study aims to decipher and quantify stability-relevant processes and their temporal occurrence, and addresses the following research questions: (i) Are fracture dynamics dominated by thermo-mechanical expansion/contraction of the inter-cleft rock mass? (ii) Do cryogenic processes, i. e. freeze-thaw dynamics and ice segregation, affect fracture opening/closing? (iii) Can irreversible crack deformation patterns and destabilisation be observed?(i) Fracture dynamics are dominated by thermo-mechanical expansion and contraction of the inter-cleft rock mass during sustained snow-covered and snow-free periods. Calculated thermal expansion coefficients of 7E-006 along and 14E-006 perpendicular to foliation highlight material anisotropy of the calcareous micaschist.(ii) Significant deviations from the thermo-mechanical deformation regime occur mainly during spring and autumn zero curtain periods due to freeze-thaw action. Peak vertical deformations are triggered by rainfall events providing liquid water onto the rock surface and into the fracture system. Subsequent refreezing rather than hydrostatic pressure build-up is assumed to cause the mechanical response of the rock. Lower magnitude deviations in the horizontal component arise in autumn and early winter, which are referred to segregation ice growth. Besides cryogenic processes, other mechanisms seem to affect fracture dynamics such as wedged rock fragments impeding maximum fracture-closing during snow-free periods.(iii) Irreversible fracture opening, pointing towards acute, high magnitude rock slope instability, was not observed. However, enhanced cryogenic deformation in spring and autumn may lead to shallow, low magnitude rock detachments. Our results highlight the importance of liquid water intake in combination with subzero-temperatures on the destabilisation of glacier headwalls. Randkluft systems may favour intense frost action and ice segregation, serving as important preparatory factors of paraglacial rock slope instability. [ABSTRACT FROM AUTHOR]

In order to understand and identify the influence of the structure of the rock mass on rock slide formation and deformation processes, the highly active, deep-seated "Marzell" rock compound slide in the Ötztal valley (Tyrol, Austria) has been examined. The investigated rock slide is situated at the SE-facing slope above the Marzell valley glacier and measures about 400 m in width and 600 m in height (main scarp at 2850 m a.s.l.). Geologically, the rock slide is located within the fractured, foliated poly-metamorphic rocks of the Ötztal Crystalline basement (i.e. paragneisses, mica schists and banded amphibolites).A multi-disciplinary approach comprising of i) geological-geomorphological mapping, ii) tachymetric and GPS survey campaigns, iii) analyses of airborne laserscanning data (ALS), iv) analyses of historic and current ortho-images, and v) manual wire-extensometer measurements, was applied to reconstruct the rock slide evolution and to develop a geometrical-kinematical rock slide model. Given that rock discontinuities influence the geomechanical failure behaviour and thus the failure geometry, a major focus was set on rock mass characterization based on discontinuity mapping. Additionally, kinematical analyses considering the structural inventory was carried out to identify modes of rock mass failure and preliminary discrete element modelling (UDEC) was performed to study rock slide kinematics and failure mechanisms.Geomorphological features such as primary and secondary scarps, uphill and downhill facing scarps, graben structures, trenches and tension fractures indicate the evolution of two time-delayed rock slide systems. Geodetic survey results show a high recent activity of the rock slide of several decimetres per year. Based on the geological structures and the measured displacement rates, six individual rock slide slabs can be identified. These slabs are separated by discrete failure surfaces/shear zones that were formed partly or totally along pre-existing NNE-SSW and E-W trending fault systems. The detailed discontinuity analyses of foliation planes, joints, and brittle fault zones show a major influence on the rock slide failure mechanism, failure geometry and kinematics. Kinematically, the SE directed slope movement caused extensional structures near the head scarp (horst and graben, trenches, fractures) and to bulging and slope steepening at the lower part of the rock slide. Results from the numerical 2-D discontinuum model are discussed with respect to: i) the structural influence on failure geometry (from pre-failure to current failure state), ii) the internal structures (e.g. horst and graben) and deformation behaviour of the sliding mass, and iii) the existence and formation process of a basal shear zone. [ABSTRACT FROM AUTHOR]