Search

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]

Quaternary glaciations have repeatedly shaped large tracts of the Andean foreland. Its spectacular large glacial lakes, staircases of moraine ridges, and extensive outwash plains have inspired generations of scientists to reconstruct the processes, magnitude, and timing of ice build-up and decay at the mountain front. Surprisingly few of these studies noticed many dozens of giant (≥10 8  m 3 ) mass-wasting deposits in the foreland. We report some of the world's largest terrestrial landslides in the eastern piedmont of the Patagonian Ice Sheet (PIS) along the traces of the former Lago Buenos Aires and Lago Puyerredón glacier lobes and lakes. More than 283 large rotational slides and lateral spreads followed by debris slides, earthflows, rotational and translational rockslides, complex slides and few large rock avalanches detached some 164 ± 56 km 3 of material from the slopes of volcanic mesetas, lake-bounding moraines, and river-gorge walls. Many of these landslide deposits intersect with well-dated moraine ridges or former glacial-lake shorelines, and offer opportunities for relative dating of slope failure. We estimate that >60% of the landslide volume (∼96 km 3 ) detached after the Last Glacial Maximum (LGM). Giant slope failures cross-cutting shorelines of a large Late Glacial to Early Holocene lake (“glacial lake PIS”) likely occurred during successive lake-level drop between ∼11.5 and 8 ka, and some of them are the largest hitherto documented landslides in moraines. We conclude that 1) large portions of terminal moraines can fail catastrophically several thousand years after emplacement; 2) slopes formed by weak bedrock or unconsolidated glacial deposits bordering glacial lakes can release extremely large landslides; and 3) landslides still occur in the piedmont, particularly along postglacial gorges cut in response to falling lake levels. [ABSTRACT FROM AUTHOR]

This paper describes a recent large rockslide, which occurred at Su village in Lishui, Zhejiang Province, China, on September 28, 2016. In the past decade, a vegetation-free deformed surface was clearly visible and frequent rockfalls were noticed. Due to strong sustained rainfall, approximately 0.4 million m3 of granite blocks rapidly descended from the upper part of the hillside. The mass rushed into the V-shaped valley resulting in the formation of a barrier dam and dammed lake. The catastrophic rockslide caused 27 deaths and more than 20 houses were destroyed. The evolutionary process before the rockslide is clearly captured by high-resolution remote sensing images and photos. Video of the rockslide and field investigations show entrainment of superficial material in the middle and lower parts of the slope. [ABSTRACT FROM AUTHOR]

Two deadly rockslides, triggered by heavy precipitation and open-pit mining, were reported in Emei County, Sichuan Province, China, from 2011 to 2015. About 6.0 million m3 of rock detached from the upper slopes, pushed the pre-sliding deposits, and hit the opposite mountains at average velocity of 18 to 36 km/h. Detailed field investigation, geological mapping, and UAV aerial photographic interpretation are presented to analyze the failure mechanisms of the events. The results suggest that the high-speed consequent bedding rockslides were triggered by the failure of rock mass, which were influenced by the engineering activities and climate change. Key contributive factors were weathered and fragmented basalts that were affected by open-pit mining and frequent blasting, as well as the weak underlying tuffs with swell-shrink potential. Persistent rainfall was the direct trigger in initiating and reactivating the landslide. Water affected the slope stability by increasing the slope material’s unit weight and penetrating into joints and cracks to make the tuffs degrade and causing a reduction in effective stress. The mechanisms for the two landslide events are a high-speed regressive consequent bedding (RCB) rockslide in 2011 and a reactivated high-speed advancing consequent bedding (ACB) rockslide in 2015. This paper can provide an insight into large-scale consequent bedding rockslides associated with the interaction between the rainfall and open-pit mining slopes instabilities. [ABSTRACT FROM AUTHOR]

Rock avalanches represent a serious risk for human lives, properties, and infrastructures. On June 24, 2017, a catastrophic landslide destroyed the village of Xinmo (Maoxian County, Sichuan, China) causing a large number of fatalities. Adjacent to the landslide source area, further potentially unstable masses were identified. Among them, a 4.5-million m3 body, displaced during the landslide event by about 40 m, raised serious concerns. Field monitoring and a reliable secondary risk assessment are fundamental to protect the infrastructure and the population still living in the valley. In this framework, the use of distinct element methods and continuum model methods to simulate the avalanche process was discussed. Various models (PFC, MatDEM, MassMov2D, Massflow) were used with the aim of reproducing the Xinmo landslide and, as predictive tools, simulating the kinematics and runout of the potentially unstable mass, which could cause a new catastrophic event. The models were all able to reproduce the first-order characteristics of the landslide kinematics and the morphology of the deposit, but with computational times differing by several orders of magnitude. More variability of the results was obtained from the simulations of the potential secondary failure. However, all models agreed that the new landslide could invest several still-inhabited buildings and block the course of the river again. Comparison and discussion of the performances and usability of the models could prove useful towards the enforcement of physically based (and multi-model) risk assessments and mitigation countermeasures. [ABSTRACT FROM AUTHOR]

Modern subaerial catastrophic mass-wasting (rockslides, rock avalanches) are identified as being huge bulky masses with a surface littered with boulders to blocks. The identification of partly preserved deposits of 'fossil' subaerial catastrophic mass-wasting, in contrast, requires assessment of deposit fabrics. In the Alps, within the synorogenic Gosau Group (Turonian to Ypresian) that accumulated in an oblique-convergent setting, we had identified a 'megabed' (Wäschkogel megabed) up to 95 m thick that is interpreted as a vestige of a subaerial rock avalanche deposit. This megabed is an extremely poorly sorted, disordered, clast-supported deposit of sand- to boulder-sized dolostone fragments from an upper Triassic succession that comprises the local bedrock. In the megabed, numerous clasts display crackle, jigsaw and mosaic fabrics with fitted subclast boundaries. The matrix is a lithified gouge of fragmented dolomite crystals. In its upper part, the megabed displays very thick planar parallel stratification. Across strata, no change in sediment fabric is discerned. The distinctive features of the megabed, i.e., the sharp intercalation between fluvial deposits, large bed thickness with a uniform fabric, abundant clasts fractured in situ, and the gouge matrix all indicate that the megabed and lateral correlatives accumulated from a rock avalanche. The planar stratification in the upper part of the megabed is interpreted as a dynamic feature produced by internal simple shear during a terminal phase of rock avalanche propagation. Bedrock geology and the distribution of other Gosau Group deposits in the area suggest that the rock avalanche propagated along a SSW–NNE striking incised valley. This is the first identification of a subaerial rock avalanche deposit in the Gosau Group. Our case study may help to consolidate the awareness of deposits of fossil subaerial catastrophic mass-wasting. [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]

An intense rainstorm on 21 May 2016 resulted a total of 34 natural terrain landslides in the vicinity of Sai Kung Sai Wan Road in the Sai Kung East Country Park, Hong Kong. One of these landslides was a large-scale failure with a source volume of about 2100m3. It was almost an order of magnitude larger than all the others. The debris severely eroded a road embankment, undermining the road and resulting in road closure. The nature of the landslide was unusual in that it was a structurally controlled rockslide, with a basal failure surface formed from a persistent, planar sheeting joint within columnar jointed tuff rock with a maximum depth of about 12 m, while the other landslides that occurred in the country park during the same rainstorm involved only shallow failures within the regolith. An investigation of this unusual landslide was undertaken to diagnose the probable mechanism and causes of the failure. As there was concern about further large-scale instability occurring in the adjacent hillside where the sheeting joint was inferred to extend into, the potential for further large-scale instability was assessed as part of the investigation. The key components of the investigation included detailed engineering geological mapping, ground investigation and engineering analyses. This paper presents the findings of the investigation. [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]

Abstract: To clarify the geological causes of rockslides induced by rainstorms in accretionary complexes, the geology and geomorphology of two large rockslides (volumes > 106 m3) induced by the heavy rainfall of Typhoon Talas in the Shimanto Belt, Kii Mountains, Japan in 2011 are investigated. Our analysis reveals that thrusts with brittle crush zones controlled the occurrence of the rockslides. The properties and distribution of thrusts were poorly constrained before this study. Flooding during the rainstorm removed surface materials along rivers, allowing thorough geological mapping to be performed. Gravitationally deformed slopes were studied using GIS analysis of 1 m digital elevation models (DEMs) and fieldwork, and X‐ray diffraction (XRD) analysis, permeability, and direct shear tests were used to characterize the mineralogy and geotechnical properties of fault gouge. The Kawarabi thrust has a brittle crush zone up to 6 m thick and acts as the sliding surface for both landslides. The thrust dips 34° downslope and is cut by high‐angle faults and joints along one or both sides of each landslide body. Prior to failure, the upper part of the slope contained small scarps, suggesting that the slopes were already gravitationally deformed. The slope instability can be attributed to long‐term river erosion, which has undercut the slope and exposed the thrust at the base of the slope. The groundwater level, monitored in boreholes, suggests that the Kawarabi thrust is a barrier to groundwater flow. The weak and impermeable nature of the thrust played an essential role in the generation of gravitational slope deformation and catastrophic failure during periods of increased rainfall. Thrusts are a common feature of accretionary complexes, including in the Shimanto Belt, and the mechanism of slope failure stated above can be typical of rockslides in accretionary complexes and provide new insights into landslide disaster mitigation. [ABSTRACT FROM AUTHOR]

There exists a transition between rockfalls, large rock mass failures, and rock avalanches. The magnitude and frequency relations (M/F) of the slope failure are increasingly used to assess the hazard level. The management of the rockfall risk requires the knowledge of the frequency of the events but also defining the worst case scenario, which is the one associated to the maximum expected (credible) rockfall event. The analysis of the volume distribution of the historical rockfall events in the slopes of the Solà d’Andorra during the last 50 years shows that they can be fitted to a power law. We argue that the extrapolation of the F-M relations far beyond the historical data is not appropriate in this case. Neither geomorphological evidences of past events nor the size of the potentially unstable rock masses identified in the slope support the occurrence of the large rockfall/rock avalanche volumes predicted by the power law. We have observed that the stability of the slope at the Solà is controlled by the presence of two sets of unfavorably dipping joints (F3, F5) that act as basal sliding planes of the detachable rock masses. The area of the basal sliding planes outcropping at the rockfall scars was measured with a terrestrial laser scanner. The distribution of the areas of the basal planes may be also fitted to a power law that shows a truncation for values bigger than 50 m2 and a maximum exposed surface of 200 m2. The analysis of the geological structure of the rock mass at the Solà d’Andorra makes us conclude that the size of the failures is controlled by the fracture pattern and that the maximum size of the failure is constrained. Two sets of steeply dipping faults (F1 and F7) interrupt the other joint sets and prevent the formation of continuous failure surfaces (F3 and F5). We conclude that due to the structural control, large slope failures in Andorra are not randomly distributed thus confirming the findings in other mountain ranges. [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]

The main objective of this paper is to consider the influence of Quaternary faults as likely triggering factor for rockslides occurrence in the Central Pre-Andes, a region with intense shallow seismic activity. A rockslide deposit was selected as study case, placed in the western flank of La Dehesa and Talacasto (DT) range (31°3′37″ S and 68°46′ 8″ W). Applied methodology includes the characterization of main discontinuities, reconstruction of the topography using a high-resolution digital elevation model, safety factor calculation along the sliding surface and, Newmark displacements estimation for three different hypothetical seismic scenarios, recreated from existing neotectonic local information. Equilibrium-limit method's results confirm that study case, La Dehesa rockslide (LDR), had a stable and safe slope's configuration under static conditions. However, a seismic horizontal coefficient between 0.2 and 0.3 decreases safety factor below the safety threshold. Newmark's displacements for different seismic reconstructed scenarios varies between 4.1 and 15.9 cm, values that agreed with a coherent failure process, likely triggered by Pleistocene to Holocene seismogenic sources in Central Pre-Andes. LDR trigger could be assigned mainly to an earthquake related to La Dehesa Quaternary fault (LDF) activity; however, similar movements produced by neighboring faults should not be discarded. LDR triggering related to climatic conditions is despised. Finally, the methodology presented in this work is easy to reproduce and may be applied to other rockslides located in the mountainous areas of the Central Pre-Andes of Argentina. [ABSTRACT FROM AUTHOR]

Landslides caused by a low magnitude earthquake swarm (2.8 ≤ M ≤ 3.6) in 2012 were documented at the Santa Rosa Canyon in northeastern Mexico. Disrupted landslides from falls and slides, in both rocks and soils, were identified based on fieldwork and high-resolution satellite imagery along stream banks from natural cliffs and along the road cut in the epicentral area. Most of the landslides occurred on slopes greater than 40°, where geological features played a key role in triggering slope instabilities. The maximum distance limit for disrupted slides from the epicentral area was 7 km. The area affected by landslides during the early stage of the seismic sequence (July through August 2012) was 90 km2. Landslide identification was limited in some areas by the resolution of the satellite imagery and dense cloud coverage. Both the epicentral distance and the area affected by landslides are above the global bounds reported in literature. The final landslide inventory is the first documented case of earthquake-induced landslides in northeastern Mexico. [ABSTRACT FROM AUTHOR]

In 2010, the south flank of Mount Meager failed catastrophically, generating the largest (53 ± 3.8 × 106 m3) landslide in Canadian history. We document the slow deformation of the edifice prior to failure using archival historic aerial photographs spanning the period 1948-2006. All photos were processed using Structure from Motion (SfM) photogrammetry. We used the SfM products to produce pre-and post-failure geomorphic maps that document changes in the volcanic edifice and Capricorn Glacier at its base. The photographic dataset shows that the Capricorn Glacier re-advanced from a retracted position in the 1980s then rapidly retreated in the lead-up to the 2010 failure. The dataset also documents 60 years of progressive development of faults, toe bulging, and precursory failures in 1998 and 2009. The 2010 collapse was conditioned by glacial retreat and triggered by hot summer weather that caused ice and snow to melt. Meltwater increased pore water pressures in colluvium and fractured rocks at the base of the slope, causing those materials to mobilize, which in turn triggered several secondary failures structurally controlled by lithology and faults. The landslide retrogressed from the base of the slope to near the peak of Mount Meager involving basement rock and the overlying volcanic sequence. Elsewhere on the flanks of Mount Meager, large fractures have developed in recently deglaciated areas, conditioning these slopes for future collapse. Potential failures in these areas have larger volumes than the 2010 landslide. Anticipated atmospheric warming over the next several decades will cause further loss of snow and glacier ice, likely producing additional slope instability. Satellite- and ground-based monitoring of these slopes can provide advanced warning of future landslides to help reduce risk in populated regions downstream. [ABSTRACT FROM AUTHOR]

The Daguangbao landslide is the largest co-seismic landslide triggered by the Wenchuan earthquake (Ms 8.0) occurred on 12 May 2008. The landslide, which is 4.6 km long and 3.7 km wide, involves a volume of approximately 1.2 × 109 m3. An exposed slip surface, situated at the southern flank of its source area, was observed with a length of 1.8 km along the main sliding direction and an area of 0.3 km2. To study the geological and tectonic characteristics of the source area and their contributions to the landslide formation during the earthquake, detailed geological investigations were firstly conducted. And it is reached that the landslide occurred on the northwestern limb of the Dashuizha anticline with its scarp showing several geological structures, including joint sets, local faults, and folds. These tectonic-related structures potentially influenced the failure of the landslide. Secondly, further investigations were focused on the inclined planar sliding surface using 12 exploratory trenches, nine boreholes, a tunnel, borehole sonic data, and micro-images. These data reveal that the rock mass along the sliding surface was the fragmented rock of a bedding fault. A pulverized zone was observed on the sliding surface, which was the zone of shear localization during the landslide. This suggests that the shear failure of the Daguangbao landslide developed within the bedding fault. The rapid failure of the landslide was associated with the degradation of the rock mass strength of the bedding fault both before and during the 2008 Wenchuan earthquake. With this study, we propose that a pre-existing large discontinuity within a slope may be the basis for initiating a large landslide during earthquake. [ABSTRACT FROM AUTHOR]

Slopes with interbedded rock layers are widely distributed around the world and have experienced numerous landslide disasters. This study used physical model tests and the distinct-element method to identify the failure mechanisms of slopes with interbedded sandstone and mudstone. First, physical model tests were designed and carried out to investigate the effects of river incision and mudstone wetting-softening on the deformation and failure modes of such slopes. Subsequently, a distinct-element simulation was conducted to back-analyze the physical model tests and to investigate the effects of the boundary conditions and joint sets on the slope failure mechanisms. The physical model tests reveal that river incision alone may not be sufficient to cause a landslide. However, this situation may change instantaneously depending on the exposure and wetting-softening of deep mudstone layers. The results of the physical model tests were then used to verify the results of the distinct-element simulation. The simulated displacement distribution and failure mode agreed well with the measurements and observations from the physical model tests. The numerical simulation indicated that numerous tensile micro-cracks form in the upper part of the slope due to river incision, and several micro-cracks may develop into macro-cracks as a result of mudstone wetting-softening. In addition, a preliminary numerical parametric study indicates that the slope failure mode does not change when the left boundary condition varies from free to roller conditions, and the layers are continuous instead of discontinuous. However, the simulation shows that penetrative tension cracks are less likely to form in the river incision process of a slope without joints. In this case, landslides do not tend to occur because it is difficult for rainfall to seep into the slope and converge to mudstone layers, which are prone to softening in water. [ABSTRACT FROM AUTHOR]

A massive rockslide occurred in the Soutpansberg Mountains of the Limpopo Province ~20,000 years ago that blocked the course of the eastern flowing Mutale River forming Lake Fundudzi, which is the only known true inland lake in South Africa. The landslide occurred in the northwestward dipping and highly jointed Fundudzi Formation of the Soutpansberg Group. The failed slope was observed to be a homogenous jointed sandstone rock slope which is quartzitic in places. Cluster analysis, which uses fuzzy clustering in Rocscience Dips, revealed three major joint sets (JS1, S0 and JS3) in the rock mass with an average dip and dip direction of 85°/237°, 15°/283° and 73°/157°, respectively. The main failure plane best correlated with JS3, which dips towards the lake. The kinematic analysis also revealed that the mechanism of failure was planar which is in agreement with site observations. The strong rock material classification of the sandstone from a laboratory index and mechanical tests was one of the indicators that failure could have been mostly structurally controlled. The technique of back-analysis was employed using RocPlane in order to investigate the geotechnical conditions that may have resulted in failure. The results obtained from the sensitivity analysis in RocPlane showed that the joint roughness coefficient (JRC) followed by the residual basic friction angle (ϕr) were the main influential shear strength parameters on the factor of safety, F, as opposed to the joint wall compressive strength (JCS) which has very little impact on F for the range of values considered. Results from back-analysis show a range of possible combinations of JRC and ϕr values under different groundwater and seismic conditions. Whilst the groundwater shows more impact than the seismic coefficient, the field evidence points to seismic activity as a more plausible trigger than groundwater. This study shows the usefulness of back-analysis techniques in assessing various conditions of failure that may have resulted in ancient rockslides. Although it may not result in a unique set of geotechnical parameters that may have resulted in failure, it, however, gives an insight into probable causes of failure and, thus, can be useful in mitigation of future failures. [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 this study a combination of different topographic data from historic topographic maps and remote sensing is used to reconstruct and monitor the behaviour of the high alpine ice contact rockslide system Marzell and its response to glacial debuttressing in the Eastern Alps. Topographic data from archives (historical topographic maps, national glacier inventories, aerial images, orthoimages and ALS data) and data from monitoring campaigns (geodetic measurements, terrestrial laser scanning and UAV imaging campaigns) are processed to georeferenced images and/or elevation data, respectively. The data from different data sources is compiled and analysed with the aim to i) reconstruct the extent, thickness and volume changes of the glacier since 1893 and ii) to analyse the rockslide deformation evolution by extracting information about the displacement direction, dip angle, velocity and partial failure of rockslide slabs since 1951. The rockslide is compound of different rockslide slabs which move downwards as rigid blocks along basal shear zones. The analyses and interpretation of the data suggest a rotational type of rockslide failure mechanisms. The rockslide activity correlates with the ice volume loss at the adjacent part of the glacier. In the period between 1971 and 1997 the annual average rockslide activity was about 0.05 m/a and the annual average ice thickness loss was 0.1 m/a. Since the end of the last century the annual average ice thickness loss increased dramatically to 5 m/a. In that period the rockslide activity accelerated. The highest rockslide activity (up to 1.5 m/a) was observed in the 2000s when half of the slope toe was exposed because of glacier retreat. Since 2010 a deceleration of the rockslide can be observed. In the vicinity of the rockslide the glacier almost disappeared and lost 99.88% of its ice volume between 1893 and 2014. The geomorphological and geological information gathered about the rockslide evolution and the glacier retreat form the base for further rockslide analyses and allow to study and model the influence from glacial debuttressing. [ABSTRACT FROM AUTHOR]

The focus of the present study is to explain the stair-step brittle deformation evolutionary pattern of the landslide and reveal the corresponding internal physical mechanism. Based on the concept of high strength geological body (HSGB), similar to rock bridges in the intermittence jointed rock masses, a conceptual geological model and the corresponding mechanical model are successively outlined. Through reanalysing typical stair-step displacement records of a wedge rockslide, it was found that the HSGB model can reasonably explain the stair-step deformation feature and reveal its internal essence. Finally, a displacement criterion is derived through combining the two-dimensional renormalization group model with the shear creep constitutive model. By means of this displacement criterion, one can quantitatively describe the displacement ratio between the onset of the accelerating creep and brittle rupture of HSGB. In order to make the reader understand this displacement criterion better, a detailed application process is demonstrated through a case study. To some extent, the present study has shed light on the failure prediction of the HSGB-type landslide, whose stability is mainly controlled by HSGB. [ABSTRACT FROM AUTHOR]

The Jiweishan rockslide of June 5, 2009 in China provides an important opportunity to elucidate the kinetic characteristics of high-speed, long-runout debris flows. A 2D discrete element model whose mechanical parameters were calibrated using basic field data was used to simulate the kinetic behavior of this catastrophic landslide. The model output shows that the Jiweishan debris flow lasted about 3 min, released a gravitational potential energy of about 6 × 10^13 J with collisions and friction dissipating approximately equal amounts of energy, and had a maximum fragment velocity of 60–70 m/s, almost twice the highest velocity of the overall slide mass (35 m/s). Notable simulated characteristics include the high velocity and energy of the slide material, the preservation of the original positional order of the slide blocks, the inverse vertical grading of blocks, and the downslope sorting of the slide deposits. Field observations that verify these features include uprooted trees in the frontal collision area of the air-blast wave, downslope reduction of average clast size, and undamaged plants atop huge blocks that prove their lack of downslope tumbling. The secondary acceleration effect and force chains derived from the numerical model help explain these deposit features and the long-distance transport. Our back-analyzed frictions of the motion path in the PFC model provide a reference for analyzing and predicting the motion of similar geological hazards. [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]

This study combines remote sensing data from ground- and satellite-based radar to calculate 3D displacement vectors for the Jettan rockslide, Troms, northern Norway. Using 3D displacement vectors, aspect data and strain rates in conjunction with structure (foliation, faults, fractures), geomorphological elements (ridges, scarps, terraces, depressions), topography and borehole data, we identify zones undergoing displacement, e.g., extension and compression, displacement into- or out-of-the-slope and/or various degrees of tilting. Our results show variable 3D displacement velocities, from north to south, that segment the rockslide into distinct domains. Displacement patterns are structurally controlled, as spatial variation in azimuth and plunge of 3D displacement vectors can be related to variation in attitudes of the host-rock foliation, faults and fractures. In the north, a complex graben system surrounded by orthogonal NW-SE and NE-SW-trending geomorphological elements, shows a repeated stepping 3D displacement pattern. This may indicate a complex fault geometry at depth, including stepped and discontinuous slide surfaces. We interpret 3D displacement into-the-slope in the upper part, and out-of-the-slope in the lower part, to be back-rotation of antithetic blocks with planar fractures becoming curved/listric gliding surfaces with depth. Downslope reduction in velocity indicates compression and stacking of blocks. In the southern area, N-S-trending geomorphological elements are arranged parallel to the hillslope. 3D displacement vectors show a more homogenous displacement pattern indicating movement along planar, hillslope-parallel, fracture sets at depth. We propose a structuralcontrolled slope displacement model including alternate planar- and wedge-failure, in addition to displacement along planar and listric fractures merging into foliation at depth. Using the Jettan rockslide as a case study, we show how remote sensing data may aid examination of structural and topographic controls on rockslide kinematics, thus giving new insights into subsurface geometry. [ABSTRACT FROM AUTHOR]

The potential of long-term, real-time surface displacement monitoring by ground-based radar interferometry (GB-InSAR) to improve the understanding of mechanisms and set up objective early warning criteria for complex rockslides is explored. Monitoring data for a rockslide in the Central Italian Alps, collected since 1997 by ground-based and remote-sensing techniques, are examined. A unique 9-year continuous GB-InSAR monitoring activity supported an objective subdivision of the rockslide into 'early warning domains' with homogeneous involved material, mechanisms and sensitivity to rainfall inputs. Distributed GB-InSAR data allowed setting up a 'virtual monitoring network' by a posteriori selection of critical locations representative of early warning domains, for which we analysed relationships among rainfall descriptors and displacement rates. The potential of different early warning criteria, depending on the instability mechanisms dominating different domains, is tested. Results show that (a) rainfall intensity-duration-displacement rate relationships can be useful tools to predict displacements of 'rainfall-sensitive' rockslide sectors, where clear trigger-response signals occur, but are unsuitable in rockslide domains affected by the long-term progressive failure of the rock slope and (b) effective early warning strategies for collapse scenarios (entire rockslide, specific domains) can be enforced by modelling real-time, high-frequency GB-InSAR data according to the accelerated creep theory. [ABSTRACT FROM AUTHOR]

Rock slope failures can lead to huge human and economic loss depending on their size and exact location. Reasonable hazard mitigation requires thorough understanding of the underlying slope driving mechanisms and its rock mass properties. Measurements of seismic ambient vibrations could improve the characterization and detection of rock instabilities since there is a link between seismic response and internal structure of the unstable rock mass. An unstable slope near the village Gondo has been investigated. The unstable part shows strongly amplified ground motion with respect to the stable part of the rock slope. The amplification values reach maximum factors of 70. The seismic response on the instable part is highly directional and polarized. Re-measurements have been taken 1 year later showing exactly the same results as the original measurements. Neither the amplified frequencies nor the amplification values have changed. Therefore, ambient vibration measurements are repeatable and stay the same, if the rock mass has not undergone any significant change in structure or volume, respectively. Additionally, four new points have been measured during the re-measuring campaign in order to better map the border of the instability. [ABSTRACT FROM AUTHOR]

Deep-seated rock slides (DSRSs), recognised as one of the most important mass wasting processes worldwide, involve large areas and cause several consequences in terms of environmental and economic damage; they result from a complex of controlling features and processes. DSRSs are common in Calabria (southern Italy) where the complex geo-structural setting plays a key role in controlling the geometry of the failure surface and its development. This paper describes an integrated multi-disciplinary approach to investigate a DSRS in Palaeozoic high-grade metamorphic rocks of the Sila Massif; it focuses on the definition of the internal structure and the predisposing factors of the Serra di Buda landslide near the town of Acri, which is a paradigm for numerous landslides in this area. An integrated interdisciplinary study based on geological, structural, and geomorphological investigations—including field observations of weathering grade of rocks, minero-petrographic characterisations, geotechnical investigations and, in particular, fifteen years of displacement monitoring—is presented. Stereoscopic analysis of aerial photographs and field observations indicate that the Serra di Buda landslide consists of two distinct compounded bodies: (i) an older and dormant body (~ 7 ha) and (ii) a more recent and active body (~ 13 ha) that overlies the previous one. The active landslide shows movement linked to a deep-seated translational rock slide (block slide); the velocity scale ranges from slow (1.6 m/year during paroxysmal stages) to extremely slow (< 16 mm/year during stable creep stages). The geological structures and rock weathering have played a key role in the landslide's initiation and further development. Steep slope angles, rugged topography, river deepening and erosion at the toe of the slope are also responsible for the formation of this landslide. In particular, the landslide shows a strongly tectonic constraint: the flanks are bounded by high-angle faults, and the main basal failure surface developed inside an E–W southward-dipping thrust fault zone. The entire active rock mass (total volume of approximately 6 Mm 3 ) slid at one time on a failure surface that dipped < 27°, and the maximum depth, as determined by inclinometer measurements, was approximately 58 m. Petrographic and mineralogical analyses suggest that the rocks in the thrust zones, where the failure surfaces develop, are highly affected by weathering processes that significantly reduce the rock strength and facilitate the extensive failure of the Serra di Buda landslide. Finally, the landslide's internal structure, according to geotechnical investigations and displacement monitoring, is proposed. The proposed approach and the obtained results can be generalised to typify other deep landslides in similar geological settings. [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]

Ground-Based Interferometric Synthetic Aperture Radar (GB-InSAR) campaigns were performed in summer 2011 and 2012 in the Romsdalen valley (Møre & Romsdal county, western Norway) in order to assess displacements on Mannen/Børa rock slope. Located 1 km northwest, a second GB-InSAR system continuously monitors the large Mannen rockslide. The availability of two GB-InSAR positions creates a wide coverage of the rock slope, including a slight dataset overlap valuable for validation. A phenomenon of rock slope breathing is detected in a remote and hard-to-access area in mid-slope. Millimetric upward displacements are recorded in August 2011. Analysis of 2012 GB-InSAR campaign, combined with the large dataset from the continuous station, shows that the slope is affected by inflation/deflation phenomenon between 5 and 10 mm along the line-of-sight. The pattern is not homogenous in time and inversions of movement have a seasonal recurrence. These seasonal changes are confirmed by satellite InSAR observations and can possibly be caused by hydrogeological variations. In addition, combination of GB-InSAR results, in situ measurements and satellite InSAR analyses contributes to a better overview of movement distribution over the whole area. [ABSTRACT FROM AUTHOR]

On 22 February 1756 the largest historically recorded rockslide in Norway took place at Tjelle in the Langfjord (Western Norway). The rockslide created three displacement waves of up to 50 m in height that caused 32 casualties and destroyed most houses and boats along the shores of the Langfjord. The trigger and contributing factors leading to the Tjellefonna rockslide are largely unknown and even seismic triggering has previously been suggested. This study provides a thorough back-analysis of the Tjellefonna rockslide using detailed geomorphological, engineering geological and tectonic field mapping in combination with topographic reconstructions, bathymetry analysis, volume estimations and numerical slope stability analysis. The back-scarp and eastern flank of the Tjellefonna scar form several tens of meter high rock walls, while the basal failure surface and other parts of the scar are covered by rock avalanche debris that extend from the back-scarp down to the bottom of the Langfjord. The rockslide occurred in granodioritic gneisses with variably developed metamorphic foliation that is folded and strike parallel to the fjord. Two prominent fault zones are present in close proximity to the Tjellefonna scar; one is steeply SE-dipping (Tjelle fault), while the other one is sub-horizontal to shallow SE-dipping (Ritlehamran fault). Both fault zones are linked to the Møre-Trøndelag Fault Complex, with one of its branches forming the Langfjord lineament and probably also the faults at Tjellefonna. Additionally, there are four persistent joint sets that together with the metamorphic foliation and the Tjelle fault define the back-scarp of the rockslide and give a fracturing of the rock mass corresponding to a Geological Strength Index (GSI) of 45–55. The GSI decreases significantly to 10–20 in the fault zones, which form distinct weakness zones in the rock slope. Volume estimates based on a reconstruction of the ante-rockslide topography range from 9.3 to 10.4 million m 3 , which is lower than previous volume estimates (12–15 million m 3 ). Large portions of the failed rock mass remained on land and only approximately 3.9 million m 3 entered the fjord. The observed discontinuities in the rock mass at Tjellefonna do not allow for a simple kinematic failure mechanism due to the lack of moderately SE-dipping structures. The basal failure surface was most likely not composed of a single structure, but of a complex interplay of fault zones, metamorphic foliation, joints and broken rock bridges. Numerical slope stability modelling highlights that weak fault zones are essential for the development of the failure surface over a long time. This progressive failure was likely aided by low- to medium-magnitude earthquakes that are frequent in the region. Numerical slope stability modelling and historical accounts suggest, however, that heavy, long-lasting rainfall was the triggering factor for the 1756 Tjellefonna rockslide rather than an earthquake. [ABSTRACT FROM AUTHOR]

Rock glaciers are distinct landforms in high mountain environments indicating present or past permafrost conditions. Active rock glaciers contain permafrost and creep slowly downslope often forming typical flow structures with ridges and furrows related to compressional forces. Rock glaciers are widespread landforms in the Austrian Alps (c. 4600). Despite the high number of rock glaciers in Austria, only few of them have been studied in detail in the past. One of the best studied ones is the 950 m long Dösen Rock Glacier located in the Hohe Tauern Range. This rock glacier has been investigated since 1993 using a whole suite of fieldbased and remote sensing-based methods. Research focused on permafrost conditions and distribution, surface kinematics, internal structure and possible age of the landform. Results indicate significant ground surface warming of the rock glacier body during the period 2007-2015 accompanied by a general acceleration of the rock glacier surface flow velocity (max. 0.66 m/a) over the last two decades. This speed-up is possibly related to higher ice temperature and water content. As judged from various geophysical measurements, the maximum thickness of the rock glacier is about 30-40 m with an active layer of several meters depending on the location. The permafrost thickness beneath the active layer was quantified to be between 10 m (at the margins) and 40 m (at the central and upper parts). Massive sedimentary ice has not been observed or detected by geophysics so far at the central and lower part but might exist to in the rooting zone of the rock glacier as indicated from field evidences. The Dösen Rock Glacier is primarily a talus-derived rock glacier although a small glacier might have existed some times in the past in the eastern part of the rooting zone. Age estimations of the rock glacier by using the Schmidt-hammer exposure-age dating method indicate a formation period of several thousand years with alternating periods of faster and slower evolution. Research findings at this typical alpine rock glacier in the Austrian Alps clearly point out that the morphogenesis, the internal structure as well as the climaterock glacier relationship is complex but typical for such peculiar alpine landforms. [ABSTRACT FROM AUTHOR]

One of the largest concentrations of giant landslides (≥108 m3) in Patagonia is in the eastern part of Lago Cochrane/Pueyrredón (LP) valley in Argentina. In addition to minor earthflows and rock slides, this landslide cluster is dominated by rock and debris avalanches that affect the northern slope of Meseta Belgrano, the largest of which have volumes >1 km3 and a runout of >10 km. To determine the chronology of these large landslides and their relationship to the geological setting and the glacial history related to the Last Glacial Maximum (LGM) ∼20–18 ka ago, we combined geomorphological mapping with absolute dating (luminescence and radiocarbon dating) and numerical modelling of slope stability. Dating and cross-cutting relationships with glaciolacustrine deposits suggest that some of the largest rock avalanches collapsed directly into a glacial lake between ∼17 and ∼12 ka, soon after deglaciation, but some were pre-glacial and landslide activity continued until today, posing a potential hazard to the area. In agreement with these data, numerical modelling suggests that slope stability was only marginally affected by ice retreat and glacial lake drainage, and landslides were most likely favoured by relatively low rock strength, related glacially-conditioned topography, and, possibly, seismic activity. A newly identified active fault at the base of the Meseta Belgrano, whose activity was likely enhanced by postglacial rebound, was probably the key factor that concentrated postglacial rock avalanches into the LP valley. We conclude that exceptionally large (km-scale) landslides can occur on slopes made of relatively weak rocks in a glacially-conditioned topographic setting even without a strong direct triggering effect of deglaciation, while fatigue due to long-term seismicity may promote collapse. • Meseta Belgrano hosts the largest rock avalanches in Patagonia. • Most of the landslide volume mobilized between ∼17 and 12 ka. • Recurrent landslides continuing to a lesser extent in the Holocene. • Long-term seismicity is a likely cause of slope instability. • Largest rock avalanches likely triggered by stronger postglacial earthquakes. [ABSTRACT FROM AUTHOR]

• Engineering properties of ISWZs investigated considering genesis and fabric. • The Baihetan ISWZs are divided into single-layer and multilayer structures. • A new multi-index engineering rock mass properties classification method is proposed. • A strength parameters estimation method is proposed for the small-scale ISWZs. The interlayer shear weakness zones (ISWZs), which are a kind of large-scale infilled discontinuity, are frequently considered the most hazardous potential slip surface in the rock masses. Based on laboratory and field investigations, the engineering characteristics of ISWZs (i.e., genesis, fabric, structure, mineral composition, water-physical properties, shear strength properties, and engineering classification) embedded in and around the Baihetan hydropower station area are systematically examined. The results of the laboratory and field show that ISWZs have complex occurrence features, undulating and spatial inconsistency in thickness, and variation in mineral composition, fabrics, and structures. Moreover, based on variabilities in various features and extend, ISWZs are categorized into single-layer structures (Type-A) and multilayer structures (Type-B). An engineering geological classification approach for large-scale ISWZs is developed based on the two essential index such as clay proportion and infilled ratio. This classification method not only involves the influence of the undulating state of ISWZs on their shear properties but also considers the physical and mechanical properties of weak interlayer materials. The results of this investigation contribute to a proper understanding of mechanical properties and rock mass classification, especially for large-scale ISWZs. [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]

• Progressive failure of the tunnel-type anchorage (TTA) is studied by using DIC. • The rock mass fracture and TTA instability are reproduced in a simulated model. • Propagation features of rock mass crack of TTA during loading are obtained. • The anchorage-rock interface gradually slides during rock mass crack propagating. • TTA's gradual failure is the result of rock mass cracking and interface sliding. The instability of shallow tunnel-type anchorages (TTAs) installed in soft-rock strata is a progressive process; however, these have not been completely investigated. Hence, in this study, the pullout behaviours and crack-propagation characteristics of TTAs are investigated using the digital image correlation (DIC) technique. Digital images of the anchorage are captured during an experiment and are processed using the DIC to obtain the surrounding-rock deformation fields. Subsequently, the TTA pullout performance and the mechanical response of surrounding rock are analysed, and propagation of cracks in different load-bearing stages of the TTA are investigated. The results show that TTA failure gradually changed from single failure of rock mass to dual failure of rock mass and interface slip and debonding. Losing of bearing capacity of TTAs is caused by the continuous propagation of cracks, leading to the weakening of the clamping effect of rock mass and deteriorating of the shear capacity of interface. [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]

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]

Rockfalls and rockslides are significant geomorphic processes on high alpine proglacial rock slopes. In this study, we quantitatively evaluate sediment transport on a recently deglaciated rock slope that is directly connected to the shrinking Gepatschferner glacier, by multi-temporal terrestrial and airborne LiDAR observations. According to the LiDAR measurements, sediment transport by gravitational mass movements on this single proglacial rock slope (0.2 km 2 ) yielded 159 GJ/a geomorphic work. The most significant part (141 GJ/a) was released by rockfall while 18 GJ/a were performed by the sliding activity of a 1,250,000 m 3 large unstable rock mass. The results indicate that slope development and talus formation in proglacial environments may be a rapid process despite of being caused by continuous rockfall activity over several millennia. [ABSTRACT FROM AUTHOR]

The origin and evolution of Iskanderkul Lake are studied in relation to geomorphic hazards within a broader area of interest. It is shown that the giant Kchazormech rockslide with its volume of masses of approximately 1 km3entirely blocked the Iskanderdarja river valley, likely in the Middle Holocene, impounding thus the palaeolake of Iskanderkul. Geomorphological evidence indicated that the palaeolake suddenly decreased its volume by 83% and its areal extent by 65% and released 0.84 ± 0.1 km3of water. The present-day Iskanderkul Lake is therefore considered as a remnant of a much larger palaeolake of Iskanderkul. Recent slope movements, incision and backward erosion of rockslide accumulation leading to the formation of a bypass gorge are documented. Current geomorphic hazards are outlined and the near-future evolution of Iskanderkul Lake is discussed with respect to the ongoing climate change suggesting a relatively low longevity of lakes in the Tien Shan. [ABSTRACT FROM AUTHOR]

In this paper, we discriminate the contribution of the different sediment sources into a river situated in the semiarid region of northern Chile, differentiating the ones driven by the paraglacial response from the ones yielded to the tributary-junction alluvial fans or the ones coming from the hillslopes. The sedimentary infilling is accurately described in the main landforms such as alluvial fans, alluvial terraces and landslides in the current valley floor where twenty-six 14 C AMS samples were picked up. The 14 C age data indicate that the aggradation in the uppermost part of the valley immediately postdates the glacial retreat at ∼15,000 14 C years cal. B.P. and spans the whole Holocene starting at 11 ka. B.P. and finishing about 2 ka B.P. The main sources for lateral inputs are debris flows from tributary catchments in the portion where the river is embedded in between 1000 and 2000 m a.s.l as well as catastrophic landslides. Additionally, an extensive detailed geomorphological mapping is provided to discuss the meaning of the ages together with an assessment of where the samples came from. Finally, the dataset and field criteria provided in this work contribute to better perform paleoclimatological interpretations for the semiarid fluvial systems of northern Chile. These interpretations usually consider the increased influence of the westerlies during the Holocene and the span of time that the paraglacial response delivers glacigenic sediments into the system. [ABSTRACT FROM AUTHOR]

In the Indian Himalayan region (IHR), landslide-driven hazards have intensified over the past several decades primarily caused by the occurrence of heavy and extreme rainfall. However, little attention has been given to determining the cause of events triggered during pre- and post-Indian Summer Monsoon (ISM) seasons. In the present research, detailed geological, meteorological, and remote sensing investigations have been carried out on an extreme rainfall landslide event that occurred in Sadal village, Udhampur district, Jammu and Kashmir Himalaya, during September 2014. Toward the receding phase of the ISM (i.e., in the month of September 2014), an unusual rainfall event of ~ 488.2 mm rainfall in 24 h took place in Jammu and Kashmir Himalaya in contrast to the normal rainfall occurrence. Geological investigations suggest that a planar weakness in the affected region is caused by bedding planes that consist of an alternate sequence of hard, compact sandstone and weak claystone. During this extreme rainfall event, the Sadal village was completely buried under the rock slides, as failure occurred along the planar weakness that dips toward the valley slope. Rainfall data analysis from the Tropical Rainfall Measuring Mission (TRMM) for the preceding years homogeneous time series (July-September) indicates that the years 2005, 2009, 2011, 2012, and 2014 (i.e., closely spaced and clustering heavy rainfall events) received heavy rainfalls during the withdrawal of the ISM; whereas the heaviest rainfall was received in the years 2003 and 2013 at the onset of the ISM in the study region. This suggests that no characteristic cyclicity exists for extreme rainfall events. However, we observe that either toward the onset of the ISM or its retreat, the extreme rainfall facilitates landslides, rockfall, and slope failures in northwestern Himalaya. The spatiotemporal distribution of landslides caused by extreme rainfall events suggests its confinement toward the windward side of the Himalayan front. [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]

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]

Deep-seated rockslides, which are characterised by slow to extremely slow rates of movement, frequently occur in foliated metamorphic rock masses (schists, phyllites, paragneiss series). Many case studies indicate that slope displacement is predominantly localised at basal and internal shear zones. Thus, the deformation and stability behaviour of rockslides is influenced primarily by the properties of these soil-like shear zones. In this study, new findings concerning the structure, mineralogical composition and geomechanical characteristics (residual friction angle, grain size distribution) of the shear zones of deep-seated rockslides are presented. The characteristics of these shear zones are shown by case studies in paragneissic rock masses of the polymetamorphic Austroalpine Ötztal-Stubai crystalline complex in Tyrol, Austria. Differences between the laboratory scale and the in situ scale are discussed, as well as the evolution of the shear zones. Within the framework of this study, structural investigations of the shear zones were performed from surface and subsurface surveys and core logs, as well as mineralogical laboratory analyses, grain size analyses and ring shear tests. The shear zones are characterised by a complex fabric of lensoid-shaped layers of clayey-silty fault gouges embedded in sandy-gravelly fault breccias and block-in-matrix structures. The mineralogical analyses indicated high amounts of phyllosilicates, such as mica and chlorite. Swelling clay minerals were observed in small amounts in very few instances. The ring shear tests of the rockslide fault gouge samples, performed under various normal stress conditions, resulted in residual friction angles in a wide range between 19° and 28°, reached after rather short displacements. [ABSTRACT FROM AUTHOR]

The Österreichische Raumordnungskonferenz (ÖROK) set up a partnership in 2011 to deal with 'Risk management for gravitational natural hazards in landuse planning'. As gravitational natural hazards have a decisive influence on development in the Alpine Region, standard procedures were developed for the assessment of the relevance of these processes for landuse planning. This paper describes the recommended procedure for the assessment of hazards affecting permanent settlements from rockfall in a top-down approach. The first step to define potential conflicts between the maximum run-out of rockfall processes and the presence of settlements is a conservative empirical assessment based on rock outcrops serving as potential detachment zones and the maximum reach of such rockfalls, leading to a hazard indication map. This approach is only based on existing cartographic information, field investigations are not necessarily involved at this stage. To ensure conservative results, the use of a high-resolution 1 m ground model to identify rock outcrops is re commended. The next step includes a thorough examination of those areas in the hazard indication map with conflicts between the maximum reach/run-out of falling blocks and settlements. This stage includes field investigations with mapping of maximum reach blocks, block size distributions, underground conditions of the transit zone and the condition of rock outcrops that act as potential detachment zones. All this information is subsequently integrated into a 3D rockfall simulation. As a result the modelling enables a delineation of areas out of reach (no rockfall hazard), areas with potential impact energies ≤ 100 kJ (low intensity) and areas with potential impact energies > 100 kJ (high intensity). [ABSTRACT FROM AUTHOR]