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Nanoparticles found in rock avalanches and natural faults were inferred to be the reason for the ultra-low shear resistance of the materials along the shear surface. Nevertheless, this inference has not been physically verified yet. To investigate the role of nanoparticles in the shear behavior of granular materials, we conducted a series of ring shear tests on silicon dioxide nanoparticles (SN), silica sand (S8), and mixtures of the S8 with different contents of SN, under varying normal stresses (σ) and shear velocities (V). Our results showed that the shear strength (μ) of SN is high when σ is small (≤ 215 kPa at our test range), even though the maximum shear velocity is about 210 cm/s, but shows a great decrease under higher σ (≥ 619 kPa). The shear strength of mixtures varied with SN content. For S8 (M0) and the mixture of 10% SN (M10), when sheared under small σ, μ first decreased slightly with increasing V when V is smaller than 1 cm/s, after that it increased slightly with further increase of V. Nevertheless, this kind of shear-rate dependent behavior was not observed in the tests under higher σ. When the content of SN in the mixture was <20%, μ increased with the increase of SN content. However, with further increase of SN content, μ decreased. Under high normal stress conditions, distinctive powder rolls were observed on the shear surface formed on the tests. When the mixtures with lower SN content (≤50%), the powder rolls were not observed. We inferred that powder rolls can be produced under high SN content and high normal stress conditions, and this structure altered the particle movement mode from sliding friction to rolling resistance, resulting in a significant decrease in the shear strength. These findings provide valuable insights into the shear behavior of granular materials with nanoparticles and then provide evidence for a better understanding of the high mobility of rock avalanches. • The shear strength of silica nanomaterial (SN) depends on the applied normal stress. • Shear velocity has no significant impact on the shear strength of SN. • The shear strength of the mixtures of sand with SN depends on the SN content. • Powder roll formation regulates the shear strength of mixtures with high SN content. [ABSTRACT FROM AUTHOR]

To improve the understanding of the dynamic disastrous process of field-scale rockslides, a novel numerical approach, Three-dimensional Discontinuous Smoothed Particle Hydrodynamics (3DSPH), was originally developed. This method comprehensively captures sequential stages of crack initiation and propagation, formation of contacts, frictional slip, catastrophic slides of rock masses, and final deposition, which was verified by three benchmark tests including the bouncing test of rigid balls, block sliding test and unconfined compression test of layered rock specimens. The approach was subsequently employed in the case of the Tangjiashan rockslide blocking valley event with particular attention paid to the influence of layered rock structure on the sliding and deposition processes. Field survey, geomorphological analysis and laboratory test of rock specimens were conducted to determine fundamental geological conditions and parameters required by the numerical simulation. Finally, 3D rockslide simulations with different rock layer thickness and strength subject to seismicity were conducted. The duration of the actual Tangjiashan rockslide's valley-blocking event (approximately 60 s) and the deposition area derived from the numerical simulation closely align with the field investigation. The rockslide mode is characterized by an 'en masse' motion with a peak sliding velocity of approximately 35–37 m/s. This single numerical code systematically elucidated the authentic attributes of the sliding process of large-scale rockslides, and realistically captured the characteristics of preservation of layered features within the sliding mass and 'high-speed and short-distance' movements with fluidization. These insights offer a fresh perspective for understanding the dynamics of large-scale rockslides with complex geological structures and subsequent accumulation processes. • A hybrid continuous and discontinuous method, 3DSPH, was originally developed for simulating rockslides. • 3D modeling of Tangjiashan rockslide was implemented with particular attention paid to the effect of layered structure. • 3DSPH realistically captured the characteristics of preservation of layered features within the sliding mass. [ABSTRACT FROM AUTHOR]

Newmark displacement analysis (NDA) has been widely used to study the initiation and kinematics of earthquake-induced landslides. The classical NDA for earthquake-induced wedge slides assumes that the wedge is a rigid block (assumption A1). The vertical and horizontal accelerations perpendicular to the sliding direction are neglected (assumptions A2 and A3). Moreover, the friction angles (friction coefficients) of the sliding surfaces are assumed to be constant during sliding (assumption A4). This study evaluates the influences of these four assumptions on the kinematics of huge wedges adopted, where the shear stress could not be identical to the sliding direction. Different rock wedge shapes subjected to synthetic seismic loads are modeled, and the sensitivity of removing unnecessary assumptions from the analysis is evaluated. A case study of the earthquake-induced Daguangbao landslide (wedge slide) is provided to assess the influence of the rigid wedge assumption and adopted strengths along wedge planes on the sliding kinematics. Our study shows that the rigid wedge method (RWM) incorporated into NDA (A1) always yields an unconservative prediction of permanent displacement comparing to maximum shear stress method (MSSM), particularly for huge, narrow wedges. The MSSM, which assumes that the shear stress perpendicular to the sliding direction equals the shear strength, should be considered owing to wedge deformation if huge rock masses are involved. Neglecting the vertical acceleration (A2) induced an underestimation of permanent displacement, particularly for narrow wedges with a gentle plunge of the intersection line. Although horizontal acceleration perpendicular to the trend of I-Line does influence the NDA results for asymmetrical wedges, the effect (A3) is insignificant. Assuming a constant strength on the wedge plane (A4) only predicted stick-slip behavior but not a frequently observed high-mobility phenomenon of huge landslides. Finally, the rapid and long run-out sliding of the Daguangbao landslide can be successfully predicted if the velocity-displacement dependent friction law is appropriately incorporated into NDA using MSSM. • Assumptions of the classical Newmark displacement analysis for a wedge slide are evaluated. • Considering inertial force and applying seismic loads on the base of the sliding wedge. • A deformable wedge incorporating velocity-weakening strength yields higher mobility. • Neglecting vertical acceleration yields underestimated permanent displacement. • Remove unrealistic assumptions; the kinematics of the Daguangbao landslide can be predicted. [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]

Abstract The North Nahanni rockslide (volume ~7.6 Mm3), Northwest Territories, Canada was triggered by the M w 6.6 Nahanni earthquake of October 5, 1985; the earthquake was followed by a M w 6.8 earthquake at approximately the same location in December 1985. The landslide occurred in a Palaeozoic carbonate sequence sliding along a thrust fault, which partly follows bedding and partly cuts across bedding in the source rock mass. The sliding surface thus consisted of two planes; the lower plane dipped at 20° while the upper plane dipped at 35°. Tilting table test of block samples from the sliding surface and field-measurements of large-scale sliding surface roughness indicated that the friction angle of the sliding surface was 24°. Two-dimensional (2D) slope stability analysis was performed for the slope before and during the earthquake using a discontinuum numerical technique (the distinct element UDEC code). 2D static slope stability analyses indicate that the simple-structured rock mass was marginally stable for sliding surface friction angles of 24°, and was constrained by the residual shear strength of the pre-sheared fault surface. 2D dynamic analyses of the co-seismic movements are conducted by comparing seismically-induced slope displacements computed in both UDEC and SLAMMER (a sliding-block analysis using real earthquake ground motions records of the December 1985 Nahanni earthquake). Both results are in good agreement. The dynamic analysis indicates that the slope becomes unstable for given seismic inputs that correspond closely to those estimated for the October earthquake at a friction angle of 24° for the sliding surface indicating that co-seismic rock slope movement was only possible on low-friction pre-sheared surfaces at residual strength. It also showed that the deformation behavior of the North Nahanni rock masses was dependent on the frequency of the seismic signals. Because the static slope stability analysis showed that the slope was close to instability prior to seismic shaking, the October 1985 Nahanni earthquake operated as a trigger event that accelerated the occurrence of the slide. Highlights • First numerical analysis of earthquake-triggered 1985 Nahanni rockslide • Bi-linear sliding surface corresponds to fault surface in a sedimentary rock mass. • UDEC used for high-resolution static and dynamic slope stability analysis. • Static and dynamic stability constrained by residual strength on pre-sheared sliding surface. • Slope became unstable for seismic inputs that correspond to triggering earthquake. [ABSTRACT FROM AUTHOR]

The radon problem in Kinsarvik, Ullensvang municipality in Western Norway, is among the most severe in the world. Annual average indoor radon concentrations as high as 56,000 Bq/m3 have been measured. The problem affects >100 houses, where average yearly indoor radon concentrations of 4340 Bq/m3 has been reported. Indoor radon concentrations vary during the year, which has been explained by thermally induced flows of radon-bearing air through a porous ice-margin deposit. Updated geological knowledge and new mapping methods (LIDAR data) have allowed for a re-examination of the problem. There is significant evidence that does not fit with the established geological understanding that classifies the Kinsarvik deposit to be an ice-marginal moraine. Instead, the landforms and internal structures of the deposit are characteristic of a rock-avalanche deposit. The LIDAR data suggests a rockslide deposit of approximately 50 million m3. Airborne and ground gamma-ray spectroscopy show elevated uranium content in the granitic bedrock north and east of Kinsarvik. These uranium-bearing rocks are also found in an open pit in the Kinsarvik deposit. Terrestrial cosmogenic nuclide dating of four surface boulders shows an average age of 10,900 ± 600 years. This suggests the rock avalanche fell immediately after the last deglaciation of Western Norway. Our results support that the radon problem in Kinsarvik is caused by uranium bearing bedrock and a porous rock-avalanche deposit that emanates radon, which in turn exhibits an alternating, temperature driven flow direction. • Extremely high indoor radon concentrations are documented in Kinsarvik Norway. • Granitic rocks have an increased uranium content that produces radon gas. • The actual deposit is proved to be a result of a rock avalanche. • The rock avalanche has crushed the uranium bearing rocks and makes for radon emanate easy. • The combination of uranium bearing rock and a rock avalanche can be a worldwide problem. [ABSTRACT FROM AUTHOR]

Better understanding the evolutionary mechanism of landslides is very important to predict their occurrence based on firm scientific grounds. The stability of a rock slope is often dominated by one or more locked segments along a potential slip surface with a large bearing capacity to resist instability. We propose three preliminary categories for locked segments and develop a physical model for predicting the instability of rock slopes with locked segments, by coupling a one-dimensional renormalization group model with a strain-softening constitutive model, based on the Weibull distribution. We found that the ratio of the strain at the peak strength point of a locked segment to the strain at its volume dilation point is exclusively dependent on the Weibull shape parameter m and is approximately constant at 1.48. The accelerating displacement of the slope can be observed from the volume dilation point of the locked segment due to unstable fracture propagation. The physical model for slopes with multiple locked segments is only related to the displacement corresponding to the volume dilation point of the first locked segment and the number of locked segments. Applying this model to two typical cases, the Yanchihe rockslide in China and the wedge rockslide in Libby Dam, USA, the results are in agreement with field records. This work will help to better understand the failure mechanism of slopes with locked segments and may provide guidelines for disaster mitigation and prevention. [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]

In this paper, static and dynamic analyses were performed considering the reconstituted geometry of a prehistoric 0.1 km 2 rockslide with an exposed stepped-planar failure surface using a distinct element code (UDEC®). The rockslide occurred on the northern slope of the Cerro Catedral mount, located in the headers of the Maipo river drainage basin (Main range of the Andes Cordillera) at the latitude of the Santiago city, Chile, between the Late Pleistocene and the Holocene. The remaining failure surface consists of two distinct sliding planes dipping at an angle of ~37° and connected by a sub-vertical step. The original geometry of the rock slope was estimated from a terrestrial laser scan elevation model (LIDAR), the deposit that remained in the valley, and the hill surface topography. The laser scan of the sliding surfaces and Schmidt hammer field measurements allowed the estimation of the sliding surface mechanical properties, whereas laboratory test results were used to estimate the rock mass material properties. Results from 2D static numerical analyses indicate that the rock slope requires the presence of at least one rock bridge at the sliding surface connecting step in order to be statically stable. Furthermore, we studied the effect of different acceleration time histories recorded during shallow crustal earthquakes, compatible with the regional seismicity, in the rockslide response. The dynamic numerical analyses show that the input earthquake records induce a pronounce topographic amplification in the rock slope, that the rockslide displacement highly correlates with the Arias Intensity, the peak velocity, and the peak acceleration calculated in the rock slope center of gravity, and that the rockslide may have been triggered by horizontal accelerations larger than 0.6 g in the free field. Finally, the slope's response is evaluated under the coupled action of horizontal and vertical accelerations. [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]

Toppling failure is a common mode of instability in layered and blocky rock slopes where rock blocks rotate about their toes and overturn. One of the most important types of toppling failure is slide-toe-toppling. In this failure, rock blocks at the toe of the slope are overturned by the pressure of sliding mass from the upper part of the slope. In the present study, this type of failure is examined through physical and theoretical modeling. The literature on toppling failures is reviewed briefly first and, then, the mechanism of slide-toe-toppling failure is described. To clarify the mechanism of the failure, a series of physical model tests is conducted under static condition by means of a new tilting table apparatus. Then, a theoretical approach is proposed based on limit equilibrium analysis and some new equations are developed for stability analysis of this type of failure. Finally, the results of physical modeling are compared with outcomes of proposed theoretical approach. This comparison shows a good agreement between the theoretical and experimental results. [ABSTRACT FROM AUTHOR]

In 2014 a small stepped-planar rockslide blocked a road near the town of San Germano Chisone in northwest Italy. Photographs of the rock cut that failed above the road were taken before and after the rockslide occurred. Some photos were acquired with the assistance of a UAV. These photos were used to conduct a forensic analysis of the rockslide. With the aid of photogrammetry software, it was possible to characterize the slope geometry and the larger geological structures that influenced the slope behaviour. A stepped-planar slip surface and the shape of the slabs of rock that failed were defined by discontinuities and these were well documented in the 3D photogrammetry models. The effective dilation angle was estimated from an assessment of the roughness of the discontinuity surfaces forming the slip surface. The stability of the rockslide was analysed as a stepped-translational failure mechanism. A two-block force equilibrium model of the rockslide was developed. With this analytic model, both deterministic and probabilistic methods were used to study the influence of water pressure as well as time-dependent shear strength degradation along the discontinuities and corrosion of rockbolts. The analysis suggests that the rockslide was caused by a combination of inadequate rock support, time-dependent shear strength degradation, and water pressure in the joints resulting from above average rainfall. [ABSTRACT FROM AUTHOR]

The remnants of rockslide dams are widespread in the deeply incised river valleys of the northwest Himalayas and adjacent Pamir Mountains of Central Asia. In January 2010 a major rockslide (estimated volume ~ 55 Mm 3 ) dammed the Hunza River (NW Pakistan) and a rockslide-dammed lake (Lake Gojal) immediately began to form. The lake overtopped the rockslide dam 145 days later through a spillway excavated in the surface of the debris by Pakistan authorities. Lake Gojal successively reduced in volume in response to spillway widening and deepening in engineering works up to May 2013; on August 28, 2015 (Day 2063 of impoundment) a remnant lake still remains. Using SRTM 3-arc-second digital terrain data and ten high-resolution satellite images from the period March 2010–August 2015, we document the river-damming environment of the Attabad rockslide, track and quantify the development of rockslide-dammed Lake Gojal and calculate lake areas and volumes at various stages of filling, stable overtopping, and partial draining to a final stable configuration. We introduce a method of delimiting lake shorelines by a pixel method which produces a mean elevation surface in the SRTM DEM; this technique results in accurate estimates of shoreline elevation and corresponding lake areas and volumes. We estimate the maximum volume reached by Lake Gojal, 51 days after overtopping, to have been approximately 455 Mm 3 . Using this data we also evaluate the mitigation works carried out by Pakistan authorities and find that i) they achieved an initial reduction of about 26% in the maximum possible volume of Lake Gojal that would have been reached without engineering intervention, and ii) as of August 28, 2015, in drawing down the lake by ~ 40 m, they had achieved a 72% reduction in the maximum volume reached by Lake Gojal after overtopping without a catastrophic release taking place. The emplacement of rockslide dams and the behaviour of their impounded lakes are critical hazards to communities and the development of infrastructure, including hydroelectric facilities, in this region of Central Asia. We show that a combination of high-resolution optical satellite imagery and SRTM 3-arc-second digital topography is very effective in producing key first-order data on rockslide-dammed lakes for geomorphic and hydrological analysis as well as the evaluation of engineering mitigation. [ABSTRACT FROM AUTHOR]

In this work, the concept of radial chain rockbursts (RCRs) was proposed for the first time. As a case study, RCRs that occurred in a deep tunnel excavated by TBM was analyzed. The occurrence process and geological characteristics of the RCRs were described. Though analyzing the microseismic (MS) temporal and spatial evolution characteristics, stress and energy evolution characteristics and fracturing mechanism of the RCRs, the development mechanism of the RCRs was revealed. The following results were obtained: (1) The RCRs is prone to occur under geological conditions with alteration zone and lithologic interface. (2) The time interval of adjacent rockbursts gradually increased, and RCRs exhibited the characteristics of time and space delay. The time interval of adjacent rockbursts was mainly affected by the adjustment of the excavation and support measures, and the stress gradually developed to the deep surrounding rock mass. (3) The stress and energy in the development stage were distributed in the deep surrounding rock mass and were released in the surface layer of surrounding rock mass in the occurrence stage. The apparent stress of the rock mass in the occurrence stage was higher than that in the development stage, and the stress gradually developed to the deeper zone during both the occurrence stage and the development stage. The repeated occurrence of RCRs was mainly controlled by three factors: the mechanical properties of the surrounding rock, stress conditions and multiple local shear slips in the rock mass near the alteration zone that are caused by TBM excavation disturbance. (4) The first two rockbursts were strain rockburst, and the latter two rockbursts were strain-structure slip rockburst that occurred along the alteration zone. The research has a guiding role for construction under similar engineering geological conditions, and provides a basis for the research on warning and mitigation of RCRs. • The phenomenon of radial chain rockbursts (RCRs) was found which lasts for a long time and seriously affects the construction schedule. • The characteristics of microseismic (MS) activity, stress evolution and energy evolution of the RCRs were studied. • The mechanism of the RCRs, including the fracturing mechanism, occurrence time and development process was revealed. [ABSTRACT FROM AUTHOR]

To better understand the dynamic process of rock avalanches blocking rivers, a novel numerical approach based on the coupled Eulerian-finite-discrete element method (CEFDEM) is proposed. The Samaoding paleolandslide blocking river event, which occurred at the upstream of the Jinsha River was used as a case study to further validate the new numerical approach. Field investigations, thermoluminescence dating, and geomorphological analysis were conducted to determine basic geological conditions and provide data for the numerical simulations. Then a calibrated 3D landslide blocking river simulation based on the CEFDEM was conducted. The landslide blocking river lasted for 70 s and landslide scale from the numerical simulation agrees well with the field investigation. The maximum overall feature speed of the entire sliding mass is 35 m/s, while part of the sliding mass can reach 69 m/s. Dynamic fragmentation of the rock slide is stratified such that the bottom of the sliding body has higher fragmentation degree than the top. The variation of kinetic energy, accumulated friction dissipation, and fracture energy of the sliding mass are also shown. The impulsive water wave is triggered immediately after sliding mass runs into river, and its maximum height is 132 m, while part of the wave can reach a speed of 64 m/s. The river water will be pushed by the subsequent sliding mass movement. A comparison of the CEFDEM model and particle flow code (PFC) model in landslide blocking river was conducted, and the advantages and limitations of CEFDEM model were discussed in detail. • A novel numerical approach of CEFDEM is proposed. • Continuity of rock and its fragmentation characteristics are considered and reflected well. • Dynamic process of a high-level rock slide blocking river in the deep valley is shown. [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]

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]

The Taihape landslide is a large, deep-seated, translational rockslide in central North Island of New Zealand, one of over 7000 large landslides mapped in the late Neogene deposits of this area. This study examined its patterns of movement using high temporal resolution, high-precision monitoring and explored the relationships between the movement and triggering mechanisms. During the 30-year monitoring period, movement was always extremely slow, but included periods of faster and slower motion due to a combination of simultaneous basal sliding, internal plastic deformation and seasonal soil shrinkage and swelling. The data suggested that movement rate was not controlled by pore-water pressure or any other monitored parameter. Intervals of more rapid movement appear to follow toe erosion that debuttress the landslide mass, an example of which occurred following a flood in February 2004 that had a return period of about 100 years. The high-temporal and spatial frequency of the monitoring and the measurement precision of the instruments have allowed new insights into the complex movement patterns of deep-seated, slow moving rockslides. The patterns of movement observed here, and the techniques described to collect and analyse the data, are applicable to many slowly moving landslides in New Zealand, and to those occurring in similar environments worldwide. [ABSTRACT FROM AUTHOR]

This paper presents the results of an investigation of the Gongjiafang landslide with the volume of about 500,000 m 3 in the Three Gorges Reservoir region (TGR), occurred on 23 November, 2008. In this study, detailed geological and geomorphological surveys, in-situ and laboratory tests, and numerical simulation are carried out to reveal the failure mechanism of this landslide. The anaclinal rock slope is characterized mainly by a set of outward dipping and non-persistent joints, a hard stratum (limestone) in the middle portion and an underlying soft base (argillaceous limestone interbedded with shale). Because of the long-term intensive river erosion caused by periodic fluctuation of the reservoir water level, the soft rock masses at the toe of the slope were softened, or even washed away, inducing the first sliding-toppling failure at the toe. The collapse at the toe leaves the hard strata in the middle unsupported, like a “beam”. Thus, a conceptual “cantilever beam” model is proposed to explain the failure mechanism of the landslide. The DEM simulation further highlights the failure process with a complex rock topple-rock slide failure mode, i.e., first composite sliding and toppling occurred at the toe, a composite shear and flexure failure of the middle “cantilever beam” and a simultaneous overall sliding failure of the rock masses in the upper part of the slope. The results imply that preventing water erosion at the toe could be an effective way in landslide prevention and treatment in the study area. [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]

The monitoring of the 410 000 m 3 coastal Gascons rockslide, began in 2009. This paper presents and analyzes combined in-situ and satellite-based monitoring data to interpret the kinematic behavior of the slide and the evolution of the rockslide and the possible mechanisms that can lead to an accelerating phase of movement. The available data are (1) relative displacements, measured by thirteen crackmeters and manually with an extensometer tape; (2) absolute displacements, obtained from inclinometers and vertical shape accelerometer arrays in boreholes, total station surveys, and satellite-based point-target-analysis-InSAR (PTA); (3) the settlement of the railway ballast monitored by two horizontal shape accelerometer arrays; (4) groundwater pressures from nine vibrating wire piezometers; and (5) weather conditions. The study indicates that the role of water on displacements varies spatially within the rockslide. The rockslide's kinematic behavior enables us to develop evolution scenarios of the rockslide, which could be useful to conduct a risk analysis. This leads to the identification of critical zones for railroad safety. The unique set of monitoring data helps to elucidate the complexity of the rockslide's behavior. [ABSTRACT FROM AUTHOR]

Strata consisting of massive, dipping layers of hard rock interbedded with thin, soft interlayers are common in Southwest China, and this structure is conducive to the formation of consequent bedding rockslides. The huge Jiweishan rockslide is an example that mobilized 5.6 million m 3 of massive, lower Permian limestone that was stratigraphically situated above a weak, 30 cm-thick layer of bituminous shale with a downslope dip of 21°. Field data and historical observations indicate that the rupture surface of this rockslide weakened gradually from the rear, upper part to the front. This evidence includes (1) a decrease in the thickness and areal extent of fracture-parallel calcite veinlets along the thin rupture zone. (2) the development of a wide, vertical tension fracture at the upper boundary of the slide block, about 50 years before the catastrophic failure; (3) a succession of small collapses that migrated from the upper to the lower parts of the slide block in the decade before the massive failure. This type of landslide is accordingly termed an advancing consequent bedding rockslide (ACB rockslide). An equation was developed to simulate the mechanical behavior of the rupture surface as a function of position and time. Finally, a computational model that incorporates this equation was used to simulate the evolutionary history using realistic mechanical parameters. The simulation results show how the size of an upper “driving block” progressively enlarges at the expense of a lower “ locking block” that restrains the slide mass, until the locking block becomes so small and weak that failure occurs. Good agreement between the simulation results and field data support the proposed evolution model, including the calculated size of the locking block prior to failure and the width of the upper tension fracture. [ABSTRACT FROM AUTHOR]

Rapid sliding in a rock avalanche may occur from strain- and strain-rate- weakening of the rupture-surface strength. However, existing research on rock-avalanche dynamics pays little attention to rupture-surface weakening. In this paper, we used high-speed-friction tests on limestone and shale of the Qixia Formation to determine strain- and strain-rate- weakening of the rupture surface of the Jiweishan rock avalanche. The strain- and strain-rate- weakening model inferred that the friction coefficient of the rupture surface decreased rapidly to a residual value of <0.1 within a short interval after rock-avalanche failure, which was collectively determined by shear rate and shear displacement. We used this rate-weakening in a numerical model to investigate the dynamics of the rock avalanche, and compared it with another model that used a constant value of friction. Our model results suggested that rupture-surface weakening could cause the disintegration of the sliding body and influence the post-failure motion of the Jiweishan rock avalanche. With strain- and strain-rate- weakening, a larger sliding-out velocity (~ 13–27 m/s) of the rock mass was modelled due to reduction of frictional energy consumption causing by rupture-surface weakening. Hence a strain and strain-rate- weakened rock mass could both fly farther in the air and strike the ground at a lower angle maintaining more kinetic energy. The transport distance of such a sliding rock mass would have been ~50–500 m longer than in a model without weakening. Our study suggested that strain- and strain-rate- weakening behavior of a rupture surface would significantly increase the rock-avalanche transport distance. Use of such a model might provide more accurate prediction of the disaster reach of rock avalanches. • Rupture-surface strength decreases rapidly after rock-avalanche initiation. • Rupture-surface strength is quantitatively studied by numerical modeling. • Rupture-surface strength weakening promotes the disintegration of a rock avalanche. [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]

The active deep-seated Marzellkamm rock slide is situated in the high mountainous region of Tyrol (Austria), which has been subjected to the most recent deglaciation since the Little Ice Age (LIA). This study presents the investigation of initial rock slide formation and deformation mechanisms with respect to the structural geological inventory and the recent glacier retreat of approximately 2.2 km in length and 160 m in thickness since 1893. An integrated approach comprising field-based rock mass characterisation, glacier reconstruction based on historical maps (1893–1949) and remote sensing data (1953–2017), multi-temporal morphological analysis (1971–2019), and 2D distinct element modelling was applied. We show that deformation features mapped on the surface are reproduced by numerical modelling, and that (i) rock slide formation and slab development originates along pre-existing fault zones, (ii) a sliding mechanism occurs along a predefined fully persistent, curved but non-circular basal shear zone, and (iii) meso-scale fractures (e.g. joints) have only a minor impact on rock slide formation. Glacier reconstruction and deformation analysis show that increased slope displacements are directly associated with accelerated deglaciation rates between 1893 and 2017. Stable slope conditions were obtained by modelling as long as half to one third of the lower slope was covered by glacier ice, i.e. before the 1969 glacier stage. Rock slide movement is assumed to have initiated during the basal shear zone formation from 1949 onwards. Triggered by the general sliding movement, shear displacement along pre-existing fault zones led to the formation of rock slide structures and the separation in individual slabs and blocks. Our study shows that detailed geological mapping and deformation monitoring in combination with numerical modelling techniques can create a promising rock slide model. • Pre-existing fault zones control rock slide formation and deformation behaviour. • Increased slope displacements coincide with rapid deglaciation rates. • Numerical modelling shows stable slope conditions before the 1969 glacier stage. • Numerical modelling indicates a predefined, fully persistent basal shear zone. • Rock slide slab development is attributed to slope acceleration phases. [ABSTRACT FROM AUTHOR]

The activity of large rockslides is dependent on a combination of interplaying factors that control strain localization within the slope. In some cases, continued deformation may lead to widespread disaggregation of the slide mass (i.e., loss of cohesion and development of debris). Layers with markedly different composition and strength may eventually form, making it difficult to assess the actual nature of hazards and related risks posed to the valley bottom. This paper provides updated insights into the highly disaggregated and rapidly evolving Ruinon rockslide (Central Italian Alps) based on more than a decade of monitoring by means of a Ground-Based Interferometric Synthetic Aperture Radar (GBInSAR). The rockslide was recently affected by a prolonged period of exceptional surface velocities—consistently exceeding 1 m/day. Monitoring data are examined in order to estimate the thickness of the rapidly moving layer of upper chaotic debris by means of the balanced cross-section method as well as determine the effects of hydrological forcing on the slope displacements. Finite-element modelling is then used to derive hypotheses concerning the deformation behavior of the slide mass at greater depth and different elevations. It is suggested that the upper debris moves at rates several orders of magnitude higher than the underlying substrate, and that in relative terms the sensitivity to sliding of the two layers is similarly governed by the increase of piezometric levels in the spring/summer. On lower slopes, the activity of the upper debris appears to be also influenced by precipitation events that are not accompanied by a notable increase of the piezometric levels measured at the rear of the slide. Our findings show the importance of implementing long-term GBInSAR monitoring at challenging sites like Ruinon, where fieldwork and installation of instruments on the slide mass are not feasible. • Long-term GBInSAR monitoring of the highly disaggregated Ruinon rockslide. • An exceptional reactivation event caused surface velocities to exceed 1 m/day. • Thickness of the rapidly moving upper debris estimated from balanced cross-sections. • Accelerations related with seasonal rises of piezometric level. • Deformation behavior at depth and different elevations inferred from FEM modelling. [ABSTRACT FROM AUTHOR]

The 2016 Italian seismic sequence was characterized by three main shocks that occurred on August 24th, on October 26th and 30th. The latter, a Mw 6.5 event, is the strongest seismic event recorded in Italy since the 1980, Mw 6.9 Irpinia Earthquake. In this time span between the first and the third shock of the 2016 sequence, more than 1000 seismic events of Mw greater than 3.0 and shallow hypocentral depth between 7 and 11 km were recorded, triggering more than of 1300 observed landslides. In this paper, the identification of the triggering models for four selected rock slides was performed together with the mechanical characterization of the affected rock masses both in situ and in laboratory. Large scale morphostructural setting was analysed to verify the role of regional tectonics in the failures. Discontinuity sets were identified at detail-scale using three-dimensional (3D) point clouds developed from structure from motion (SfM) reconstruction using unmanned aerial vehicles (UAVs). In situ and laboratory tests coupled to data from UAV 3D models were used for geomechanical characterization. Data were finally adopted as input of limit equilibrium static analyses, which allowed a better comprehension of the stability conditions prior to seismic events and clarify some aspects of the mobilized strength. • 3D Rockslides models were obtained from UAV surveys. • Structure from Motion (SfM) permitted to characterize the discontinuty sets. • The tectonic pattern of the area is controlled by NW-SE Quaternary faults. • Rockslides are locally controlled by more ancient discontinuity systems. • Failures of rock bridges were involved in the sliding. [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]

Prediction of multi-hazard slope stability events requires an informed and judicious choice of the possible scenarios. An incorrect definition of landslide conditions in terms of expected failure volume, material behavior, or boundary conditions can lead to inaccurate predictions and, in turn, to wrong engineering and risk management decisions. Reduced-scale experiments carried out two years before the Vajont disaster were carried out with a material not representative of the actual rockslide behavior and failed in not considering the simultaneous failure of the whole landslide body. Based on these inappropriate assumptions, the physical models led to wrong estimates of the safety operational level for the Vajont reservoir. This work uses the Particle Finite Element Method (PFEM) to analyze the implications of the wrong hypotheses considered in the pre-event experiments, simulating numerically the Vajont disaster for different sliding volumes and material properties. The use of the PFEM for the accurate assessment of the consequences of landslides impinging in water reservoirs has been already validated in a companion paper. In this work, we demonstrate the capabilities of a robust and reliable numerical modeling approach for the simulation of different scenarios, assessing what could have been a safe operational reservoir level in the case of a landslide generated impulse wave. The three-dimensional analyses were run with a high mesh resolution and demonstrate the suitability and robustness of the PFEM model for large-scale landslide and multi-hazard events simulation. • Application of a Lagrangian numerical method to the 3D simulation of Vajont landslide; • Analysis of the different multi-failure scenarios considered in the physical tests performed before the disaster; • Analysis of Vajont disaster for different initial water levels in the reservoir; • Comparison and discussion of the results given by the different configurations analyzed. [ABSTRACT FROM AUTHOR]

Large earth slides and rocks lides evolving into earth flows are quite widespread in the Northern Italian Apennines. Despite being simply referred to as landslides, many of them are, in fact, large complexes of landslides. They evolved through multiple and/or successive movements, undergoing partial and/or total reactivations. The reactivation of pre-existing landslide bodies is the prevalent mechanism for the known landslide events, as the historical records and the technical reports indicate. Landslide reactivation is, indeed, a relevant topic from the perspective of risk assessment and mitigation. A multi-parameter monitoring system was installed on a large complex of landslides that underwent partial or total reactivations after heavy rainfall events, causing damages to buildings and infrastructures. Two clusters of automatic piezometers—each coupled with an inclinometer—and a time-lapse resistivity deployment were the core of the monitoring system. A weather station, collecting data from subsurface thermometers, and a water content probe completed the system. After the construction of a new geological model of the slope, this study aimed at understanding the possible mechanisms leading to the reactivation of the landslide. This goal was achieved by gaining insights into the process of rainfall infiltration into the landslide deposits, by determining the groundwater flow and evaluating the landslide displacements. The monitoring system captured the processes that took place in the landslide bodies and the bedrock in response to a rainfall event in early February 2017, which followed a dry period of eight months. The recorded data provided indications on the variation of the hydraulic head in the groundwater within the landslide and the bedrock, particularly at the sliding surfaces. The electrical conductivity of the groundwater and the resistivity of the terrain varied across the failure surfaces. In particular, a sudden increase in the electrical conductivity was related to the locations of the main sliding surfaces. The joint analysis of time-lapse resistivity, hydraulic heads, and groundwater electrical conductivity helped identify the locations of weaker levels within the landslide masses, which were confirmed by data from inclinometers. This study improved the knowledge of the hydrogeological behaviour of a complex of landslides in heterogeneous low-permeability media. Moreover, the obtained results contributed to the understanding of the role played by different portions of the landslide complex in the evolution of the movement. • Dynamics of earth slides-earth flows within a complex of landslides. • Time-varying resistivity and borehole water conductivity reveal landslide activity. • Increase in the electrical conductivity of groundwater is related to sliding surfaces. [ABSTRACT FROM AUTHOR]

Heavy rainfall may increase the infiltration rate, raising the groundwater table after a short period time. Variation in the hydrostatic pressure on potential sliding surfaces and trailing edges of fissures in a rock slope may contribute to slope failure. The failure mechanisms of rainfall-triggered rock wedge slides have been widely studied in the literature. However, studies on the dynamic evolution of groundwater in rock failure are still limited. In this study, a typical rock wedge slide that occurred in Chengkou County, Chongqing, China is selected as a case study to analyze the stability of rock wedge with double planes and tension crack subjected to groundwater dynamic evolution. Model tests were designed and performed to reproduce the dynamic evolution of groundwater in the rock slope and analyze its role in wedge failure. Development and distribution characteristics of water pressure are investigated through monitoring the water pressure distributed along the surfaces of wedge failures. From the experimental study, it is found that the initial formation process of water pressure along the sliding surface consists of four types of distribution patterns, i.e., triangular distribution, Type I trapezoidal distribution, Type II trapezoidal distribution, and Type III trapezoidal distribution. Based on the model tests and theoretical analysis, the order of the calculated safety factors of the Chengkou rock wedge slide are: triangle > type I trapezoid > type II trapezoid > type III trapezoid. The existence of inflection points in the trapezoidal distribution mode significantly increases water pressure on both sides of rock wedge, which contributes instability. The new approach for investigation of the effect of dynamic evolution groundwater on stability of rock wedge slide is developed based on fundamental mechanism and experimental study. It can be adopted for stability assessment of similar rock wedge slides in other areas. • Development and distribution characteristics of water pressure for rock wedge slide are investigated by model tests. • Results of groundwater dynamic evolution along the sliding surfaces were adopted for stability analysis of the real event. • Initial formation process of water pressure along the sliding surface consists of four types of distribution patterns. • Maximum uplift pressure will be formed when the water pressure distribution is in a triangular pattern. [ABSTRACT FROM AUTHOR]

The paper describes the study of two extremely slow, active-continuous, deep-seated landslides located in the Isarco Valley (Eastern Alps, Italy): a Multiple Rotational Rock Slide (MRRS) and partial reactivation of a Deep-Seated Gravitational Slope Deformation (DSGSD). Both landslides interact with viaducts on the E45 highway. Extensive multi-method field investigation, monitoring of surface and subsurface displacements and limit equilibrium stability analyses were adopted to fully characterize slope dynamics. In order to overcome the limitations due to the systematic errors affecting each single monitoring system and analysis method, an operative framework based on redundancy and coherence tests was introduced to check the reliability of the data and results. In this framework, the geological and geotechnical models of the investigated slopes were progressively refined. This allowed assessment of the type of interaction between the slopes and the highway viaducts. • Study of large, composite and extremely slow landslides requires extensive multi-method monitoring of displacements. • Systematic errors affecting the measurements may mask the actual rate of movement. • Redundancy and coherence tests of monitoring data as a tool to check reliability of data and results. • The reliability of displacement monitoring is crucial to analyse large extremely slow landslides. [ABSTRACT FROM AUTHOR]

• The DDA simulates the mining-induced rock avalanche. • The failure process of the landslide was numerically identified. • The simulated failure process correlates well with the expert image and the local landform. This study numerically simulated the failure process of a mining-induced landslide at Nattai North, Australia. Results obtained using Discontinuous Deformation Analysis (DDA) matched the conceptual failure process suggested by local geologists and the observed maximum run-out distance. The maximum velocity of the sliding rocks exceeded 40 m/s. Computational results showed that the slope with inward sub-horizontal bedding planes and sub-vertical discontinuities remained stable if the mining-induced high principle stresses did not fracture the rocks near the slope toe. Failure of the rocks near the toe of the slope was a key causal factor in the subsequent landslide. This paper presents the first numerical simulation of the post-failure behavior of the mining-induced landslide at the Nattai North site. It also represents the first DDA simulation to clarify the chain reaction of a mining-induced landslide and demonstrate its applicability in such investigations. [ABSTRACT FROM AUTHOR]

• Baffles system can reduce the deposit area of rock avalanches by more than 13.5%. • Shape changing (cylindrical to arc-shaped) will up-regulate the fragment blockage degree; the following avalanches will take place close to the avalanche deposition, leading to a huge dissipation of kinetic energy. • Arc-shaped baffle system showed competitive blocking ability when Sc=3.5 and Sr=4.5. • The number of rows mainly affects the avalanches deposit area and the baffles blocking capacity. • Baffles' spacing Sc mainly affects its blocking efficiency. To reduce the flow energy of rockfall in rmountain area, a baffle array is set up in the protection zone. The optimized design can enhance the efficiency of hazard source energy dissipation project. In the present study, the arc-shaped baffles were studied as compared with the conventional baffles (square baffles and cylindrical baffles) based on practical engineering. The comparison of three types of baffles was discussed in detail by experimental studies, which primarily focused on the blocking ability and effectivity. In particular, by determining the optimal case using those different types of baffles, the effects of the optimization of baffle system [column spacing, row spacing and Ld (distance between first baffle row and chute terminal)] were investigated. According to the results, the arc-shaped baffle is the best case among those three types of baffle, i.e. the deposit area and runout are all shorter than those of any other cases with the same value of Sr. Shape changing (cylindrical to arc-shaped) will up-regulate the fragment blockage degree; the following avalanches will take place close to the avalanche deposition, leading to a huge dissipation of kinetic energy. Moreover, by comparing deposition, dimensionless velocity (U*) and velocity reduction ratio (VRR), arc-shaped baffle system showed competitive blocking ability when Sc = 3.5 and Sr = 4.5. With the rise in the Ld, the energy dissipation efficiency can be enhanced through the particle collision and particle friction during the geo-disaster movement. Furthermore, it can effectively narrow the deposit area and reduce deposit depth and deposit width. The results obtained from this study are useful for facilitating design of baffles against rock avalanches. [ABSTRACT FROM AUTHOR]

Rock slides triggered by strong earthquake or heavy rainfall may cause different degrees of blockage in flow channels, resulting in a significant impact on the continuity of mountainous rivers. Based on the extent of blocking, the blockage type is divided into three categories in this paper: no blockage (submerged dam), partial blockage, and complete blockage. The accumulation process of sliding materials in the course of rock slides is an important issue for understanding the formation of landslide dams. In this study, rock slide and river valley models are developed to investigate the typical kinematic process and emplacement of rock slides, and the factors that dictate the formation of landslide dams are critically analyzed. The experimental study suggests that there is a positive correlation between the deposit height and the rock slide volume despite differences of rock fragmentation and flow condition. In addition, the less fragmented rocks result in larger maximum deposit height (maxi-DH) and smaller minimum deposit height (mini-DH), while the better fragmented rocks result in smaller maxi-DH and larger mini-DH. Furthermore, the water depth has a significant impact on the river blockage type. A new Blockage Index (BI) that combines the landslide volume and the wet cross-sectional area is proposed to assess the damming capacity of rock slides. Then a method for predicting the river blockage type of rock slides is developed based on the relationship between Blockage Index and the ratio of maxi-DH or mini-DH and water depth. The model proposed in this work can be used to assist estimating the formation of landslide dam for similar rock slides in the future. • Model tests on typical process of the rock-slides dam formation were conducted. • Parametric analysis on deposition characteristics and blockage type is discussed. • New Blockage Index and regression models are suggested to assess the damming capacity and predict the type of river blockage. • The advantages and limitations of exploring the rock-slides dam formation using physical models are discussed. [ABSTRACT FROM AUTHOR]

Rockslides commonly form a shear zone to accommodate their displacements. As such, the landslide history and mechanism must be recorded in the structural features of the shear zone. We investigated the basal shear zone of a 60-m-thick rockslide body with a lateral displacement of 200 m on a dip slope and found the evolutionary mechanisms of a basal shear zone of a rockslide. A basal shear zone on a dip slope is initiated along a lithologic boundary that is characterized by a high competency contrast, such as pelitic rock and greenstone or chert, and develops in the weaker rock, which was pelitic rock in the present study. The basal shear zone first develops with fracture of the rock mass, followed by intragranular fracturing of rock fragments. Shear strain by landslide gradually localizes to a narrow zone in the fractured zone to form a clayey layer by cataclasis of rock fragments. The rock fragments in the clayey layer become rounded by attrition, and the clayey layer finally obtains shear surfaces with slickensides. • Direct observation of a basal shear zone clarifies the mechanism of a rockslide. • Rockslide proceeds with fracturing followed by attrition in the shear zone. • Shear strain gradually localizes in the shear zone to a zone of attrition. • A clayey layer with rounded fragments is the final product of the shear displacement. [ABSTRACT FROM AUTHOR]

On May 5th, 2013 a planar rock slide (~450 m3) occurred in the village of La Riba (NE Spain), which forced the closure of the road C-240z for 6 months. This slide left a hanging block (~130 m3) suspended on the slope forcing a controlled blasting, followed by rock slope stabilization works. The volume of rock displaced during the both events was deduced from LiDAR and photogrammetry data following two approaches: subtracting pre- and post-event data and reconstructing the volume by fitting planes on the structural surfaces after a structural analysis of the slope. Information about the natural rock slide was obtained from the records of two permanent broadband seismic stations located 10 km from the site. From these seismic records, the existence of a rock slide was confirmed and its time of occurrence was determined, information that would be otherwise unknown. In addition, despite the small volume displaced during the event, its location was deduced from a single seismic station analysis. The blasting process was recorded with two high-definition (HD) video cameras and by two temporary seismic stations deployed close to the site (<100 m). Both the seismic and video recordings enabled us to reconstruct the trajectories and propagation details of the blasted rock blocks, involving material of different size sliding on the slope, suspended in the air or bouncing and impacting along the slope and on the road. Potential and seismic energy ratios (E s /E p) for each event were calculated from seismic data analysis in order to investigate the possibility of estimating properties of the rockfalls, primarily volume. The potential energy of both events was deduced from the volumes calculated using remote sensing methods and ranged between 189 and 201 MJ for the natural rock slide and between 48 and 54 MJ for the artificially triggered rockfall. The seismic energy was calculated following two approaches; estimating pseudo local magnitudes and by classical wave propagation theory, obtaining E s values ranging from 2.0 × 10−1 MJ to 4.4 × 10−1 MJ for the natural rock slide and from 4.5 × 10−3 to 9.1 × 10−3 MJ for the artificial event. We estimated ranges of E s /E p ratios between 1.5 × 10−7 and 5 × 10−3 for the natural rock slide and between 8.5 × 10−5 and 1.1 × 10−4 for the artificial rockfall. The comparison of the volumes calculated using these ratios with the realistic volumes estimated from remote sensing data analysis, show that the seismic method is far less reliable for this task, specifically for small volumes (<500 m3) at long distances (>10 km). Partially, because only a part of the released energy is transmitted into the ground as seismic energy, and partially because the recorded seismic signal is highly dependent on the event characteristics and the geotechnical conditions of the ground materials. Nevertheless, seismic data is very well suited to detect and characterize in detail both rockfall events of different nature and size. Merging and integrating remote sensing techniques such as LiDAR or photogrammetry with seismic measurements should allow the implementation of rockfall early warning systems. • A small rockslide is characterized using a 3-component seismic record acquired at a station distant 10 km. • A blasted rockfall is analyzed with nearby (100 m) seismic data and video recordings • Rock volumes are estimated using LiDAR and photogrammetry, even without pre-event data • Rockfall seismic energies and Es/Ep ratios are estimated from seismic data • Combining remote-sensing and seismic data provide reliable data to study rockfalls [ABSTRACT FROM AUTHOR]