Long Runout Landslides Research Articles

Process dependence of grain size distributions in rock avalanche deposits

Rock avalanches are a form of hazardous long-runout landslide and leave fragmented deposits of complex sedimentology that, if studied in detail, can provide insight into their emplacement processes. Complexity arises due to the myriad overlapping factors known to contribute to the final deposit fabric, such as source structures, lithology (i.e. material properties), topographic feedback, substrate interaction and emplacement processes (i.e. internal factors), as well as our reliance on (un)suitable exposures. Herein, we present sedimentological data from two carbonate rock avalanche deposits (Tschirgant in Austria and Flims in Switzerland), where changes in lithology can be eliminated from the causal equation due to their largely mono-mineralic composition. We further eliminated the effects of external influences such as topography or substrate interactions by detailed facies mapping of the deposit interior. Since sedimentary properties locally vary within less than 1-m2 outcrop area, emplacement processes are the only causes that remain to explain the different fabrics. Characteristic (fractal) grain size distributions of three distinctive sub-facies in the interior of these, and other, rock avalanche deposits—jigsaw-fractured, fragmented, and shear zone facies—can be linked to specific processes acting during emplacement. We suggest that a heterogeneously distributed and progressively increasing particle breakage in the moving granular mass best explains the ranges of fractal dimensions and associated features for the respective sub-facies, from simple breakage along pre-existing planes, through dynamic fragmentation which locally minimises coordination number, to zones of shear concentration. No exotic emplacement mechanisms (such as air-layer lubrication or fluidised substrates) are required to produce these features; continued, heterogeneous degrees of fragmentation of an initially intact source rock best explains the sedimentary record of rock avalanches.

Comment on “The Reduction of Friction in Long-Runout Landslides as an Emergent Phenomenon” by Brandon C. Johnson, Charles S. Campbell, and H. Jay Melosh

Comment on “The Reduction of Friction in Long-Runout Landslides as an Emergent Phenomenon” by Brandon C. Johnson, Charles S. Campbell, and H. Jay Melosh

Mechanism of two rapid and long-runout landslides in the 16 April 2016 Kumamoto earthquake using a ring-shear apparatus and computer simulation (LS-RAPID)

Around hundred landslides were triggered by the Kumamoto earthquakes in April 2016, causing fatalities and serious damage to properties in Minamiaso village, Kumamoto Prefecture, Japan. The landslides included many rapid and long-runout landslides which were responsible for much of the damage. To understand the mechanism of these earthquake-triggered landslides, we carried out field investigations with an unmanned aerial vehicle to obtain DSM and took samples from two major landslides (Takanodai landslide and Aso-ohashi landslide) to measure parameters of the initiation and the motion of landslides. A series of ring-shear tests and computer simulations were conducted using a measured Kumamoto earthquake acceleration record from KNet station KMM005, 10 km west of Aso-ohashi landslide. The research results supported our assumed mechanism of sliding-surface liquefaction for the rapid and long-runout motion of these landslides.

Experimental and numerical investigations of a catastrophic long-runout landslide in Zhenxiong, Yunnan, southwestern China

On 11 January 2013, a catastrophic landslide of ∼0.2 million m3 due to a prolonged low-intensity rainfall occurred in Zhenxiong, Yunnan, southwestern China. This landslide destroyed the village of Zhaojiagou and killed 46 people in the distal part of its path. The displaced landslide material traveled a horizontal distance of ∼800 m with a vertical drop of ∼280 m and stopped at 1520 m a.s.l. To examine the possible mechanism and behavior of the landslide from initiation to runout, the shear behavior of soil samples collected from the sliding surface and runout path was examined by means of ring shear tests. The test results show that the shear strength of sample from the sliding surface is less affected by shear rate while the shear rate has a negative effect on the shear strength of runout path material. It is suggested that the source and runout path materials follow the frictional and Voellmy rheology, respectively. Post-failure behavior of the landslide was modeled by using a DAN-W model, and the numerical results show that the selected rheological relationships and parameters based on the results of ring shear tests may provide good performance in modeling the Zhenxiong landslide.

Self-sustained lift and low friction via soft lubrication

Relative motion between soft wet solids arises in a number of applications in natural and artificial settings, and invariably couples elastic deformation fluid flow. We explore this in a minimal setting by considering a fluid-immersed negatively buoyant cylinder moving along a soft inclined wall. Our experiments show that there is an emergent robust steady-state sliding regime of the cylinder with an effective friction that is significantly reduced relative to that of rigid fluid-lubricated contacts. A simple scaling approach that couples the cylinder-induced flow to substrate deformation allows us to explain the elastohydrodynamic lift that underlies the self-sustained lubricated motion of the cylinder, consistent with recent theoretical predictions. Our results suggest an explanation for a range of effects such as reduced wear in animal joints and long-runout landslides, and can be couched as a design principle for low-friction interfaces.

Long-runout landslides and the long-lasting effects of early water activity on Mars: COMMENT

Long-runout landslides and the long-lasting effects of early water activity on Mars: COMMENT

Long-runout landslides and the long-lasting effects of early water activity on Mars: REPLY

Long-runout subaerial landslides (>50 km) are rare on Earth but are common features shaping Mars’ Valles Marineris troughs. In this study, we investigated the highly debated emplacement mechanisms of these Martian landslides by combining spectral and satellite-image analyses. Our results suggest that hydrated silicates played a decisive role in facilitating landslide transport by lubricating the basal sliding zone. This new understanding implies that clay minerals, generated as a result of water-rock interactions in the Noachian and Hesperian (4.1–3.3 Ga), exert a long-lasting influence on geomorphic processes that shape the surface of the planet.

How unusual is the long-runout of the earthquake-triggered giant Luanshibao landslide, Tibetan Plateau, China?

In the Tibetan Plateau, active tectonic deformation triggers frequent earthquakes, and giant landslides associated with active faults produce serious consequences. A study of the characteristics and mechanism of a historical long-runout landslide in Luanshibao (LSB), Tibetan Plateau, China, finds a maximum sliding distance (L) of 3.83km with an elevation drop (H) of 820m. The landslide volume (V) was ~0.64–0.94×108m3, and it produced a long-runout (H/L=0.21). Recent surface offset along the sinistral strike-slip Litang-Dewu fault passes through the middle part of the landslide, which initiated on the hanging wall of the fault. Geological mapping, geophysical prospecting, trenching, and 14C dating together indicate that the LSB landslide occurred in jointed granite ca. 1980±30YBP, probably triggered by a large earthquake. Compilation of volume and runout distance data for this landslide and other previously published data for volcanic and nonvolcanic long-runout landslides yields a composite runout length-volume relation (L=12.52V0.37) that closely predicts runout of the LSB landslide, although substantial variation is noted in runout length around the central tendency.

Surface roughness dating of long-runout landslides near Oso, Washington (USA), reveals persistent postglacial hillslope instability

Establishing regional landslide chronologies is necessary to advance from hazard recognition to risk assessment, and to understand the evolution of landslide-prone terrain. Despite recent advances in landslide mapping due to the availability of high-resolution lidar imagery, estimating the timing of slope failures remains a challenge. Here we present a new integrated approach to dating landslides on a regional scale by augmenting quantitative surface roughness analysis with radiocarbon dating and numerical landscape modeling. We calibrate a roughness-age curve, which we use to date 25 deep-seated landslides in glacial sediment surrounding the catastrophic A.D. 2014 Oso landslide along the North Fork Stillaguamish River in Washington State (USA). Lidar bare-earth images show a high density of long-runout landslides in this region. Using our roughness-age curve, we estimate an average Holocene landslide frequency of 1 every 140–500 yr, and show that the 2014 Oso landslide was the latest event in an active history of slope failures throughout the Holocene. With each landslide, substantial sediment is delivered to the North Fork Stillaguamish River, driving shifts in the active channel that ultimately affect the pattern of landslides across the valley. The high frequency of landslides in this area, where river incision and isostatic uplift rates have dropped dramatically since peaking soon after ice retreated from the region, shows that landscapes inundated by glacial sediment do not require dramatic changes in base level to remain highly unstable for tens of thousands of years.

Long-runout landslides and the long-lasting effects of early water activity on Mars

Long-runout subaerial landslides (>50 km) are rare on Earth but are common features shaping Mars’ Valles Marineris troughs. In this study, we investigated the highly debated emplacement mechanisms of these Martian landslides by combining spectral and satellite-image analyses. Our results suggest that hydrated silicates played a decisive role in facilitating landslide transport by lubricating the basal sliding zone. This new understanding implies that clay minerals, generated as a result of water-rock interactions in the Noachian and Hesperian (4.1–3.3 Ga), exert a long-lasting influence on geomorphic processes that shape the surface of the planet.

A probabilistic approach for landslide hazard analysis

We present a general framework for probabilistic landslide hazard analysis. With respect to other quantitative hazard assessment approaches, this probabilistic landslide hazard analysis has the advantage to provide hazard curves and maps, and to be applicable to all typologies of landslides, if necessary accounting for both their onset and transit probability.The method quantifies, for a given slope location, the exceedance probability of being affected by a landslide with a specific local intensity within a reference time interval, i.e. the hazard curve, under the common assumption that landslides behave as a Poisson process. Hazard maps are calculated, reducing the hazard curve to single values by choosing a fixed probability of exceedance following standards or regulation requirements. The method is based on the assessment of a landslide onset frequency, a runout frequency for long-runout landslides, and the local definition of landslide intensity, which can be expressed through different parameters, according to landslide typology. For long runout landslides, the runout and spatially-varying intensity and uncertainty are considered.Hazard curves and maps play a fundamental role in the design and dimensioning of mitigation structures, in land planning and in the definition of risk and hazard management policies. Starting from the general framework, we apply the methodology for rockfall hazard analysis, and we test it in an area affected by the Christchurch 2011 earthquake, New Zealand, which triggered a large number of rockfalls, killing five people.

A study of remote sensing image features of typical landslides

The image features of landslides with different kinds of geological conditions,types and runout distances show great difference in remote sensing images with different resolutions.For long-runout landslide and complex landslide,the available interpretation keys are few,so that the identification of landslide mainly relies on ground survey.On the basis of the achievements of landslide remote sensing investigation obtained both in China and abroad and the remote sensing investigation projects for geological hazards,the authors analyzed the remote sensing image features of typical landslides,including Daqingkan Landslide,Qianjiangping Landslide,Wulong Landslide and 102 landslide group in Tibetan region.Then,the interpretation keys to landslides,especially to the high-speed and long-runout landslides,were summarized for colleagues'reference.

토석류 유동성 평가를 위한 링 전단시험장치 개발 및 활용

산사태는 토사, 거석, 유목 등 산사태 물질의 중력사면 이동현상이다. 산사태는 수리학적, 지형학적, 지반공학적 요인에 따라 다양한 흐름 및 퇴적특성을 보인다. 흐름특성은 아주 느리게 움직이는 산사태(활동, 이류 등)에서 아주 빠르게 움직이는 산사태(토석사태, 토석류 등)까지 다양하다. 이런 점에서 산사태 발생과 확산 메커니즘의 이해를 위해 전단변형률에 따른 전단강도특성에 대한 연구가 필요하다. 본 연구는 한국형 산사태에 적합한 링 전단시험장치의 개발과 활용성에 대한 것이다. 링 전단시험장치는 산사태 유형별 피해 및 영향성 평가에 사용되는 전단강도를 측정할 수 있으며, 전단속도에 따른 산사태의 유동성을 평가하기 위한 장치이다. 비배수 전단강도 측정용 링 전단시험장치는 기존에 개발된 링 전단시험기의 수정보완형으로 '포화-압밀-배수-전단' 순으로 시험조건을 자유롭게 조절할 수 있다. 링 전단상자내 흙 시료의 전단강도의 정확한 측정을 위해 미끄럼 방지, 밀폐성 및 회전성 향상 기능을 갖춘 시험장치이다. 링 전단시험장치는 모래와 자갈 시료에 대한 예비실험을 수행하였으며 기존 시험결과와 비교하여 신뢰할 만한 결과를 확인하였다. 회전속도 100 mm/sec 로 구속할 때 배수조건에 따른 일시적 액상화 현상으로 인한 강도저하 현상이 관측되며, 전단면에 따른 입자파쇄 현상이 뚜렷하게 나타났다. 마지막으로 토석류 유변학에 기초하여 링 전단시험장치를 이용한 산사태 유동성 평가기법을 제안하였다. Landslides are known as gravitational mass movements that can carry the flow materials ranging in size from clay to boulders. The various types of landslides are differentiated by rate and depositional features. Indeed, flow characteristics are observed from very slow-moving landslides (e.g., mud slide and mud flow) to very fast-moving landslides (e.g., debris avalanches and debris flows). From a geomechanical point of view, shear-rate-dependent shear strength should be examined in landslides. This paper presents the design of advanced ring-shear apparatus to measure the undrained shear strength of debris flow materials in Korea. As updated from conventional ring-shear apparatus, this apparatus can evaluate the shear strength under different conditions of saturation, drainage and consolidation. We also briefly discussed on the ring shear apparatus for enforcing sealing and rotation control. For the materials with sands and gravels, an undrained ring-shear test was carried out simulating the undrained loading process that takes place in the pre-existing slip surface. We have observed typical evolution of shear strength that found in the literature. This paper presents the research background and expected results from the ring-shear apparatus. At high shear speed, a temporary liquefaction and grain-crushing occurred in the sliding zone may take an important role in the long-runout landslide motion. Strength in rheology can be also determined in post-failure dynamics using ring-shear apparatus and be utilized in debris flow mobility.

Late-Holocene evolution of a floodplain impounded by the Smrdutá landslide, Carpathian Mountains (Czech Republic)

Landslides affecting narrow mountainous valleys might significantly determine sedimentation dynamics of floodplains. We present here a detailed study of the sedimentary archive within a landslide-controlled impounded floodplain (Smrdutá site, Czech Flysch Carpathians) using geochronological (14C and 137Cs), sedimentological and pollen evidence. A sedimentary sequence deposited above the landslide dam points to three highly discontinuous and instantaneous depositional events dated to 4.6 and 2.0 cal. ka BP, whereas the last cycle started approximately in the 17–18th centuries and has continued to recent times. Such sedimentary pulses characterized by the duration of several decades to a few centuries originated as a consequence of the blockage and/or reduction of the valley floor width by successive long-runout landslides from a slope formed by tectonically and lithologically anisotropic flysch bedrock. Stages of mass movement activity revealed by the Smrdutá landslide correlate well with major humid late-Holocene oscillations suggesting its high sensitivity to century-scale climatic deteriorations. The character of lithological units forming individual sedimentary pulses, erosional hiatuses and sedimentary traces caused by the July 1997 extreme flood indicate a decisive role of large flood events during accretion and erosion of the floodplain-impounded section.

Slippery sliding on icy Iapetus

Enigmatically, some landslides flow farther than normal frictional resistance allows. Cassini images of Saturn’s icy moon Iapetus reveal a multitude of long-runout landslides that may have been enabled by flash heating along the sliding surface.

Massive ice avalanches on Iapetus mobilized by friction reduction during flash heating

The great distance travelled by long-runout landslides, observed previously on the Earth and Mars, requires a mechanism of friction reduction. Identification and analysis of long-runout landslides on Saturn’s moon Iapetus suggests that the Iapetian landslides are enabled by flash heating of the icy sliding surface.

Catastrophic slope failure and its origins: Case of the May 2010 Girová Mountain long-runout rockslide (Czech Republic)

One of the largest long-runout landslides in the modern history of the Czech Republic originated on the southern slopes of the Girová Mountain (Outer Western Carpathians) at the end of extreme rainfalls in May 2010. The structurally predisposed Girová Mountain rockslide occurred very quickly within fault-weakened, deeply-weathered flysch bedrock. Its main phase, during which a wedge-like block collapsed in the upper part of slope, lasted for a few hours. The overloaded slope collapsed and its motion lasted for the following 3days. The May 2010 Girová Mountain rockslide is an excellent case of a recurrent long-runout landslide nested within a deep-seated gravitational slope deformation with a long history of Late Quaternary mass movements. The chronology of slope failures within the studied slope was reconstructed by means of radiocarbon dating and dendrogeomorphological analysis. At least one Holocene long-runout landslide (7.4calka BP) and several smaller failures (~1.5 and ~0.6calka BP) preceded this recent catastrophic failure. Dendrogeomorphological analysis showed that the failure had been preceded by at least 80-year-long creep movement that accelerated over the years due to extreme rainfall events. Despite the fact that extreme precipitation of May 2010 represented the last incremental change before catastrophic collapse of the slope, its main reason was gradual weakening of rock massif and concentrated creeping (with some accelerated phases) in the upper part of the slope deformation.

The largest prehistoric landslide in northwestern Slovakia: Chronological constraints of the Kykula long-runout landslide and related dammed lakes

This study deals with the chronology of the largest long-runout landslide in the northwesterrn part of the Western Flysch Carpathians (Kysucké Beskydy Mts, Slovakia). Despite the impossibility of using direct radiocarbon dating method, time constraints for the evolution of the landslide were determined on the basis of the dating of various sedimentological/geomorphological elements situated on and adjacent to the landslide body. The results show that the landslide evolved between ∼ 10.3 and 9.0 ka 14C BP, i.e. in the wider transitional phase between the Late Glacial (LG) and the Holocene. The main mass movement activity took place at the turn of the Younger Dryas/Preboreal chronozones, whereas retrogressive activity continued up to the Preboreal/Boreal transition. Radiocarbon dating together with pollen analysis and sedimentology of landslide-dammed palaeolakes and colluvial peat bogs revealed almost continuous Holocene palaeogeographical records between ∼ 10.3 and 3.3 ka 14C BP. Periods of enhanced sediment supply to the reservoirs in ∼ 9.9–9.0, ∼ 8.4–8.2, ∼ 6.9–6.5 and ∼ 4.5 ka 14C BP correlate well with palaeogeomorphic and palaeohydrological records from nearby Polish Carpathians. The study confirms that the LG/Holocene transition represented a favourable period for the evolution of large landslides not only in glaciated high mountain areas, but also in medium-high mountains of Central Europe.

Flow experiments with gravel and blocks at small scale to investigate parameters and mechanisms involved in rock avalanches

Laboratory experiments play an important role in improving the modelling of rock avalanches since they contribute to a better understanding of the mechanisms that characterise propagation and to identifying parameters influencing velocity and deposit characteristics. Tests analysed in this paper consist of unconstrained flows of gravel and small blocks down an inclined board, which ends with a horizontal part where the mass flow comes to rest. The varied parameters are fall height, volume, material, slope inclination and friction angle. When blocks, i.e. small bricks of 1.5 cm × 3.1 cm × 0.8 cm, are used, two different starting arrangements are considered: poured in randomly into the release container or piled orderly one on top of the other. Runout, width and length of the final deposit are measured manually while mass front velocity and deposit morphology are derived with specific processing from films and images. The fringe projection method, an optical technique, allows retrieving the thickness of the final deposit and then computing the position of its centre of mass. Therefore, the analysis of the experimental results is no longer limited to data such as runout and apparent friction angle (Fahrböschung), but it also allows to consider the distance travelled by the mass centre. By analysing the velocity of the mass front as it enters the accumulation zone, it is possible to observe an initial uniform decelerated motion under the effect of friction followed by a transitory part, where the impulse given by the rear part of the mass affects this motion and causes a relative acceleration. This provides experimental evidence to theories by Heim [Heim, A., (1932): Bergsturz und Menschenleben. Frets und Wasmuth, 218.], Van Gassen and Cruden [Van Gassen, W., Cruden, D.M., (1989): Momentum transfer and friction in the debris of rock avalanches. Can. Geotech. J., V.26, 623–628.] and Legros [Legros, F., (2002): The mobility of long-runout landslides. Eng. Geol., V.63, 301–331.] which state that a transfer of momentum occurs between the rear approaching part and the front part slowing down ahead, inducing the mass to spread and consequently the front to travel further. The greater the volume of the mass, the greater the duration of the interaction between the rear and front parts and the longer is the runout. Conversely, no change in the travel distance of the centre of mass is observed. The experimental results suggest that the concept of a straight energy-line based on a simple frictional model is not adequate to evaluate the distance travelled by the centre of mass. As stated by Legros [Legros, F., (2006): Landslide mobility and the role of water. In Landslides from massive rock slope failure. Edited by Evans, G.S., Scarascia Mugnozza, G., Strom, A., and Hermanns, L.R. NATO Sciences Series, IV. Earth and Environmental Sciences, vol. 49, 233–242.], only models that take into account a velocity dependent term of energy dissipation, such as the Voellmy model, should be used. Moreover, the energy line seems to depend on the geometry of the set-up. The tests with bricks piled orderly at the start seem to provide experimental evidence for the phenomenon described as the spreading of a coherent mass by Davies and McSaveney [Davies, T.R.H., McSaveney, M.J., (1999): Runout of dry granular avalanches. Can. Geotech. J., V.36, 313–320.]. First, the mass behaves as a compact body (the bricks remain packed together) and energy dissipation takes place mainly through friction at the base. Then, it shatters and energy is mainly dissipated through friction/collisions between the bricks. Having “spared” a part of the energy in the first part of the sliding, the mass enters the accumulation zone with a higher velocity and consequently travels further than a mass sliding as a loose material from the start. This mechanism of propagation could partly explain the large travel distance of rock avalanches.

Increased mobility of bidisperse granular avalanches

The unexpected behaviour of long-runout landslides has been a controversial subject of discussion in the geophysics community. In order to provide new insight into this phenomenon, we investigate the apparent reduction of friction resulting from the presence of a second species of smaller particles in the bulk of the granular material that forms the avalanche. Results obtained by means of a two-dimensional soft particle discrete element numerical simulation are presented. The numerical experiments consider an avalanche of two-size particles, originally placed over an inclined plane. The friction coefficient for the particle–particle and wall–particle contacts is held fixed. The granular mass is allowed to evolve with time, until it comes back to rest on a horizontal plane. The position of the centre of mass is located, such that the runout length Lcm/Hcm could be measured, with Lcm and Hcm being the horizontal distance travelled and the height lost by the avalanche centre of mass, respectively. Many simulations were performed keeping the area of the avalanche constant, varying only the area fraction of small particles. The results show that the runout length increases with the area fraction of small particles, reaching a maximum for a given area fraction of small particles. A detailed analysis of the particle distribution in the granular mass indicates that the apparent friction coefficient is affected by the formation of a layer of small particles at the base of the avalanche. This layer is identified as the source of ‘lubrication’. Furthermore, since there is a dependence of the runout on the fall height and the volume in real avalanches, some simulations with different areas and different fall heights were performed. The results show a tendency of the runout to increase with area, and to decrease with the initial fall height, which is in agreement with what is observed for geological events.