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

Displacement rates of mountain slope deformations that can affect entire valley mountain flanks are often measured spatially distributed in‐situ without spatial significance. The spatially explicit measurement and recording of time series of slope deformations is a challenge, as the unstable slopes are often disintegrated into several subdomains, which move with different deformation rates. The current state‐of‐the‐art monitoring systems detect slow to very slow deformation rates between mm/a and several m/a. Using the examples of slope deformations in Saalbach‐Hinterglemm and the deep rock slide Marzellkamm in Austria this paper presents the results of terrestrial laser scans, extensometer measurements, Spaceborne InSAR data, unmanned Aerial System Photogrammetry (UAS‐P), and fixed‐point measurements. The different measurements complement each other and are optimally aligned for different application areas. InSAR data can help to identify hot spots on regional and local scale, while UAS‐P enables for spatially high level accuracy in the detection of subdomains moving at different speeds. For local warning systems TLS, extensometers and GBInSAR deliver higher accuracy. [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]

In spring 2008 a rock slide detached from one of the walls in the quarry 'Frauenmühle' locally used as climbing park, mobilizing a volume of 50 m3. The binary granite is relative fresh on the bottom of the walls, but the weathering increases significantly to the natural surface. The bedrock shows an orthogonal joint system enabling the so-called 'Wollsackverwitterung'. Mapping of the joints followed by a kinematic analysis of the quarry wall by DIPS (Rocscience) indicates the slope failure to be of a planar sliding type on a medium-steep dipping plane. As the contributing factor for the slide, weathering along the plane has to be considered. Thereby the destruction of rock bridges downgrades the overall shear strength. A stability analysis based on the reconstructed block geometry and the determined shear parameters verifies the instability of the block. For today's situation, the kinematic analysis detects some critical intersections of joints being able to generate slide wedges. [ABSTRACT FROM AUTHOR]

This Hans Cloos lecture paper develops general reflections inspired by Ian McHarg's () book, 'Design with Nature' and concerning engineering geology. Three case studies are illustrated: landslides in reservoirs, gallery excavation in a shield volcano, large rockslides and rock avalanches. For these three case studies, the potential and limits of conceptual and numerical models are discussed. [ABSTRACT FROM AUTHOR]

Abstract: The Pisciotta landslide is a slow-moving deep-seated rock slide in the Campania region of southern Italy, which has damaged a provincial road several times in the last decades and currently poses a hazard to the national railway that intersects the toe of the landslide. The landslide involves an Oligocene turbidite series, which is composed of intercalated calcarenites, marls and mudrocks. The principal objectives of this study were to investigate the morphological evolution of the unstable slope, quantitatively analyse ground deformations and construct an engineering-geological model that is consistent with the spatial features of the landslide. The long-term evolution of the unstable slope was assessed through the examination of available aerial photos from 1943 to 2006. Kinematic analyses of the ground deformations were conducted based on observed progressive displacement of the road, as evident from the topographic maps and orthophotos (1955–2006), and the bi-weekly displacement survey of 50 targets distributed across the landslide area (September 2006–March 2009). The engineering-geological model of the landslide was reconstructed from the stratigraphic data obtained from the study of borehole data and monitoring of inclinometers as well as from geological, structural and geophysical surveys. The analysis of the aerial photographs revealed an early stage of deformation in 1943, which has been gradually widening since then. In addition to the main scarp and the landslide flanks, other significant landslide structures such as the longitudinal and transverse cracks as well as the positive or negative morphologies were monitored and mapped in the subsequent years. These studies indicated a progressive erosion of the upper part of the slope and a bulging of the foot. Long-term kinematic analysis based on the progressive displacements of the road allowed the measurement of the ground deformations from 1955 to 2009, which revealed a cumulative horizontal displacement of up to 53m and an average velocity of 0.98myear−1, which has increased in the recent decades. In addition, the recent monitoring of the ground deformations demonstrated a continuous activity with an approximately constant rate of displacement and a composite kinematic history of the landslide body through differential displacements and associated velocities. The engineering-geological model of the landslide was found to be controlled by specific stratigraphic and structural constraints. The landslide involves a stratigraphic interval of the Saraceno Formation (Nord-Calabrese tectonic unit) with a largely marly–argillaceous composition whose structural setting displays complex folding (at the mesoscale) and faulting with an approximately monocline attitude of bedding and a downslope dip direction at the macroscale. The left flank of the landslide rests on a normal fault. [Copyright &y& Elsevier]

Mining induced seismicity was anticipated at the Tasmania Mine (formerly the Beaconsfield Gold Mine) before the commencement of modern production in 1999. Consideration of available stress measurement data from throughout Tasmania, coupled with rock material property data gathered at the Tasmania Mine during project feasibility investigations, suggested that the onset of mining induced seismicity could be expected at depth around 700 m below surface. That proved to be the case, with mining induced seismicity regularly observed from 760 m and below from 2002. Before 2006, management of seismicity was strictly controlled through geotechnical investigation and application of geotechnical control of all mining activities. The local stress regime was measured, understood and modelled in 2003. A temporary seismic monitoring system was operational from April 2004 and it was replaced with a permanent array in mid 2005. In late 2005, mining methods at the narrow vein Tasmania Mine were typical of mining methods employed at similar operations the world over. A substantial difference was the degree to which external opinion was sought, innovative techniques and methods were implemented, and a peer review of the entire process was undertaken. It was not enough: a seismically induced rockfall on 25 April (Anzac Day) 2006 took the life of a colleague. That the entire world was appraised of the accident was of secondary importance. An extensive coronial investigation found that no corporation or individual erred in respect of the Anzac Day accident. The clear message from that finding was that generally acceptable techniques for the management of mining induced seismicity, while at the limit of extant engineering experience, were below the expectations of the wider community. Management of seismicity at the Tasmania Mine post Anzac Day is a multidisciplinary activity that involves the entire workforce at every turn. Extensive seismic monitoring, saturation level instrumentation, development of innovative mining (and in particular stoping) methods, detailed 'first principals' ground support and reinforcement designs, exclusion and re-entry protocols surrounding all stope blasts, and the continued professional peer review of all geotechnical aspects of the operation, are part and parcel of the continued operation of the Tasmania Mine. This paper describes the latest developments in that process. [ABSTRACT FROM AUTHOR]

Abstract: The analysis of the three-dimensional rockfall scar geometry provides clues for the understanding of the failure mechanisms acting on cliffs, of the conditioning factors, and on the frequency of the events. In this paper, a supervised step-by-step methodology is presented for establishing the statistical magnitude–frequency relation of rockfall scar volumes, using a point cloud from Terrestrial Laser Scanner (TLS) data. The methodology includes a procedure for identifying discontinuity surfaces, calculating the areas of those which are exposed, and the height of rockfall scars. In the estimation of the rockfall scar volume a key issue is the consideration of the minimum spacing of the discontinuity sets to differentiate between step-path surfaces and undulated ones. Having obtained the distributions of both the basal area and height of the scar across the slope, the volume of the rockfall scars is calculated stochastically by multiplication of these two parameters by means of a Monte Carlo simulation. Both distributions of the basal area and of the rockfall scar volume are found to be power-law, with the exponent b ranging from 0.9 to 1.2. The relation obtained might be used as a first approach of rockfall magnitude–frequency curves in large cliffs. [Copyright &y& Elsevier]

Following a rockslide in a former quarry near the town of Dürnstein/Wachau, extensive remedial measures were necessary to restore the damaged rail infrastructure and ensure long term safety. To provide for safe working conditions during the phase of construction of additional protection measures, a geotechnical risk management system based on the observational method per EC 7 was developed and implemented. Geotechnical monitoring was a key safety management element. The paper discusses the specific challenges, practical approaches and general experiences associated with the use of the observational method for the monitoring of cliff faces. Nach einem Felssturz in einem ehemaligen Steinbruchgelände nahe der Ortschaft Dürnstein/ Wachau waren umfangreiche Maßnahmen zur Wiederherstellung und langfristigen Sicherung der stark beschädigten Bahnlinie erforderlich. Um während der Sanierungsphase die Sicherheit gewährleisten zu können, wurde ein Risikomanagement in Anlehnung an die Beobachtungsmethode nach EC 7 geplant und umgesetzt. Zentraler Bestandteil des Sicherheitsmanagementplans waren geotechnische Messungen. Der vorliegende Beitrag berichtet über die speziellen Herausforderungen, konkreten Problemlösungsansätze und allgemeinen Erfahrungen bei der Anwendung der Beobachtungsmethode zur Überwachung von Felswänden. [ABSTRACT FROM AUTHOR]

Abstract: Many gentle dip translational rock slides have taken place in the Three Gorges Reservoir, China. In order to study the mechanism of these translational rock slides, the authors use the Anlesi landslide as a typical case study to investigate in detail. Field investigations show that the slip zones of the Anlesi landslide were formed from a white mudstone in Jurassic red strata. X-ray diffraction and infrared ray analysis showed that the main mineral components of the slip zones are montmorillonite, illite, feldspar and quartz. Laboratory tests indicate that the slip zone soils are silty clay, of medium-swelling potential, the shear strength decreasing significantly as the slip zone attracts water and saturates. The main factors contributing to the Anlesi landslide are recent tectonic activity, incompetent beds, and intensive rainfall. Recent tectonic activity had caused shear failure along the incompetent beds, and joints within the sandstone. With the effect of intensive rainfall, water percolates to the incompetent beds along tectonic fissures, resulting in swelling of the soil material and high groundwater pressures within fissures in the strata. As a consequence, the Anlesi slope is prone to slide along these incompetent beds. Flac3D software was used to simulate the mechanism of the Anlesi landslide considering the rheological properties of soil and rock. The simulation results demonstrate that the stress, displacement and failure area changes with simulated creep time. The maximum displacement in the X direction reaches 7.59 m after 200-year simulated creep. Therefore, the mechanism of the Anlesi landslide can be illustrated considering the rheological properties of Jurassic red strata. [Copyright &y& Elsevier]

Abstract: River rejuvenation forms convex slope breaks that can destabilize nearby slopes, leading to gravitational deformation and, in some cases, catastrophic sliding of the slopes during heavy rainstorms. Such landslides were induced by Typhoon 0514, which passed to the west of Kyushu Island, Japan, on 6 September 2005. Five large, catastrophic rockslides occurred, aligning along convex slope breaks 150 to 300 m above the present river bed of the Mimi River; the slope breaks are inferred to have been formed by rejuvenation of the river. Geological and geomorphological investigation revealed that these slides occurred in sandstone and mudstone of the Cretaceous Shimanto Group and were preceded by slope deformation, which generated gravitational folds and faults that appeared as scarplets at the tops of the deformed areas. The slopes seem to have been in critical condition just before catastrophic failure, which was triggered by the rainstorm. [Copyright &y& Elsevier]

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

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

• 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]