Runout Behavior Research Articles

Effect of particle shape and initial orientation on the kinematics and runout behavior of rockfalls

Effect of particle shape and initial orientation on the kinematics and runout behavior of rockfalls

Investigation of granular flow run-out behavior under dilative and compressive Coriolis conditions using DEM simulation

Centrifuge modeling allows granular flows to be simulated under stresses characteristic of full-scale flows, while maintaining repeatability. However, the impact of the Coriolis effect on the run-out behavior of dry granular flows is not fully understood. In this study, using the discrete element method (DEM), we conducted simulations of dry granular flow both with and without Coriolis (dilative and compressive) conditions to analyze the impact of the Coriolis effect on granular run-out mobility, flow structure, and granular interaction. For unsteady flows, the dilative Coriolis force increased the moving distance of the flow centroid by 60%–70% and increased the maximum kinetic energy by 5%–17%, whereas those parameters were reduced by 30% and 2%–9%, respectively, under compressive Coriolis conditions. Results showed that selecting a lower centrifugal acceleration by reducing the rotational angular velocity in physical modeling is ineffective for realizing a weaker Coriolis effect. This study established that using a larger centrifuge could mitigate the Coriolis effect, but that this outcome became less notable as the centrifugal radius increased. Additionally, we suggest a preliminary relation that could be used to correct the results of experimental granular flow final run-out distance obtained using a geotechnical centrifuge.

Comprehensive Analysis of the Failure Potential of a Motorway Landslide in Dabu County, China

Because the failure potential of a landslide is difficult to assess, a motorway landslide that has obviously deformed was used as a case study in this research. Several multi-integrated geotechniques, including field investigation, drilling, electrical resistivity tomography (ERT), stability analysis, and numerical simulations, were used to achieve this goal. Field investigation with drilling was used to roughly determine the failure potential mass boundary and the material composition ERT technique was further used to distinguish the structure and composition of underground materials; the results agreed well with the field investigation, as well as the drilling data in the lithology judgement. The above investigations also showed the failure potential mass is in a slow sliding state and the slip surface roughly follows the contact zone between the upper soil and bedrock. Next, stability analysis based on the limit equilibrium method (LEM) was used to judge the current stability status of the slope, and its factor of safety (FOS) was 1.2 under the natural condition, 1.05 under the earthquake condition, and 1.15 under the rainfall condition. Based on the assessed potential slip surface and digital elevation data, a three-dimensional smoothed particle hydrodynamics (SPH) model was used to simulate the failure potential process. The dynamic information of the run-out behavior, including velocity, movement distance, and frictional energy, can be obtained, which is useful for hazard prediction.

Kinetic characteristics and runout behavior of the rainfall-induced Hoengseong landslide at a solar power plant on 9 August 2022 in Gangwon Province, Korea

Kinetic characteristics and runout behavior of the rainfall-induced Hoengseong landslide at a solar power plant on 9 August 2022 in Gangwon Province, Korea

Centrifuge modeling of the run-out behavior of fly ash deposits subjected to a loss of confinement

Numerous industries are concerned by the humanitarian, environmental, and economic consequences of debris flows, landslides, and material run-outs. However, the run-out behavior following a loss of confinement, e.g., dam failure, is not well understood. The material’s complex constitutive behavior means multiple mechanisms contribute to the deformation, e.g., slope instability, seepage forces, erosion, or static liquefaction. In this study, centrifuge models of fly ash deposits, with varying initial deposit density and water table height, were subjected to a rapid loss of lateral confinement. Deformation, pore pressure, and water content measurements were used to investigate and separate the mechanisms governing the run-out. Static liquefaction was observed in deposits initially looser than the critical state and led to a rapid material outflow. Slope instability was the initial failure mechanism for denser deposits or those with reduced water tables, with transient stability due to dilation-induced negative excess pore pressures followed by progressive failures caused by seepage pressures from drainage and pore pressure dissipation. Cone penetration tests, performed before the loss of confinement at different penetration rates, were used to characterize the material run-out and volume change tendencies and demonstrate a practical tool for assessing the run-out risk of deposits in the field.

Numerical modelling of an alpine debris flow by considering bed entrainment

Numerical models have become a useful tool for predicting the potential risk caused by debris flows. Although a variety of numerical models have been proposed for the runout simulation of debris flows, the performances of these models in simulating specific events generally vary due to the difference in solving methods and the simulation of the entrainment/deposition processes. In this paper, two typical depth-averaged models have been used to analyze a well-documented debris-flow event that occurred in the Cancia basin on 23 July 2015. The simulations with and without bed entrainment are conducted to investigate the influence of this process on the runout behavior of the debris flow. Results show that the actual runout can be reproduced only by considering bed entrainment. If basal erosion is not taken into account, part of the debris mass deviates from the main path and both models predict unrealistic bank overflows not observed in the field. Moreover, the comparison between measured and simulated inundated areas shows that both models perform generally well in the terms of simulating the erosion-deposition pattern, although the DAN3D model predicts a greater lateral spreading and a thinner depositional thickness compared to Shen’s model. A simple numerical experiment obtains similar consequences and further illustrates the possible reasons that cause these differences.

Modeling the runout behavior of the July 23rd, 2015 Cancia debris-flow event using two numerical models

On 23 July 2015, a typical volume-enlarging debris flow was triggered by heavy rainfall that occurred a few days before the event. The available data corresponding to this event is obtained from detailed field investigations conducted before and after the event, as well as the monitoring station installed in June 2014. This study aims to reproduce the July 23 debris-flow event using two different numerical methods, analyse the influence of entrainment on the runout behavior of the debris flow and compare the performance of different numerical methods when simulating the same debris-flow event. The results showed the following: (1) The expanded inundated area and unrealistic overflowing were observed in the scenario without entrainment while the simulation that takes entrainment into account presented more perfect results. It illustrates that entrainment is a non-negligible factor for the simulation of these volume-enlarging debris flows. (2) Two models considering the entrainment performed a good match between the simulation and the field survey. However, some noticeable differences can be observed in terms of the erosion-deposition distribution because different numerical schemes were adopted in the two models. Specifically, the DAN3D code always gives higher mobility and larger lateral spreading relative to the Shen model.

Keynote lecture. Towards reliability-management for debris flow risk assessment

Recent progress in data-integrated simulation methods excelled our understanding of debris flows including triggering mechanisms and dynamic run-out behavior. Research groups and geohazard practitioners worldwide successfully integrate advanced simulations into workflows for hazard mapping. However, many challenges remain in predictively applying such tools for accepted decision support. One reason is our lack of a systematic approach to managing the simulations’ reliability. In this contribution, we present results on an investigation to which extent the choice of data used for calibration influences the simulation’s reliability. We start with introducing building blocks of a modular and extendible data-integrated debris flow simulation toolchain developed by our group. Next, we introduce reliability as one quality measure of a holistic debris flow simulation and discuss how it can be assessed. Based on a synthetic example, we then show how different types of observed calibration data, such as impact area, deposit volume or localized velocity measurements impacts on the subsequent forward simulation’s posterior probability distribution, hence the simulation’s reliability. We conclude by discussing how linking a debris flow simulation’s reliability to type, scope and resolution of the calibration data could offer a novel pathway towards reliability management for debris flow risk assessment.

Characteristics and controls of the runout behaviour of non-Boussinesq particle-laden gravity currents – A large-scale experimental investigation of dilute pyroclastic density currents

One of the most dangerous aspects of explosive volcanism is the occurrence of dilute pyroclastic density currents that move at high velocities of tens to about a hundred of metres per second outwards from volcanic vents. Predicting the runout behaviour of these turbulent flows of hot particles and air is complicated by strong changes in the flow density resulting from entrainment of ambient air, sedimentation of particles, as well as heating and expansion of the gas phase. Current hazard models that are based on the behaviour of aqueous gravity currents cannot capture all aspects of the flow dynamics, and thus pyroclastic density current dynamics remain comparatively poorly understood. Here we interrogate the runout behaviour of dilute pyroclastic density currents in large-scale experiments using hot volcanic material and gas. We demonstrate that the flows transition through four dynamic regimes with distinct density and force characteristics. The first, inertial regime is characterized by strong deceleration under high density differences between the flow and ambient air where suspended particles carry a main proportion of the flows' momentum. When internal gravity waves start to propagate from the flow body into the advancing flow front, the currents transition into a second, inertia-buoyancy regime while flow density continues to decline. In this regime, subsequent arrivals of fast-moving internal gravity waves into the front replenish momentum and lead to sudden short-lived front accelerations. In the third regime, when the density ratio between flow and ambient air decreases closer to a value of unity, buoyancy forces become negligible, but pressure drag forces are large and constitute the main flow retarding force. In this inertia-pressure drag regime, internal gravity waves cease to reach the front. Finally, and with the density ratio decreasing below 1, the current transitions into a buoyantly rising thermal in regime 4.Unlike for aqueous gravity currents, the Froude number is not constant and viscous forces are negligible in these gas-particle gravity currents. We show that, in this situation, existing Boussinesq and non-Boussinesq gravity current models strongly underpredict the front velocity for most of the flow runout for at least half of the flow propagation. These results are not only important for hazard mitigation of pyroclastic density currents but are also relevant for other turbulent gas-particle gravity currents, such as powder snow avalanches and dust storms.

Three-dimensional large deformation modeling of landslides in spatially variable and strain-softening soils subjected to seismic loads

Landslide is a common dynamic large-deformation disaster of mobilized soils, which poses a serious threat to the lives and economic properties of surrounding people. Both the strain-softening effect and spatial variability of soil are reported to have significant impacts on landslide behaviors. This study investigated the coupled effect of strain softening and spatial variability on the occurrence, evolution, and runout behavior of landslides induced by seismic loads, using three-dimensional (3D) large-deformation finite-element method. The results show that both the strain-softening behavior and spatial variability of soil dramatically affect the sliding velocity and runout distance. Their coupled effect further weakens the soil strength, resulting in a larger runout distance. Secondly, the runout distance in the 3D deterministic analysis is always smaller than the minimum value in the corresponding random analysis, which completely differs from the result from the two-dimensional (2D) analysis. This finding indicates that 2D analysis can result in a conservative estimation on the runout distance for spatially variable soils and highlights the advantages of 3D modeling on landslides. Thirdly, a linear formula was proposed to quantify the runout distance based on the horizontal peak acceleration, which can provide some guidelines for the safety design in practical slope engineering.

The influence of slope gradient and gully channel on the run-out behavior of rockslide-debris flow: an analysis on the Verghereto landslide in Italy

Rockslide-debris flow may cause catastrophic damages because of its high speed and long run-out distance. The influences of slope gradient and gully channel on the entrainment, deposition, and run-out behavior of this type of landslide were not sufficiently investigated by previous studies. To achieve a better understanding toward this type of landslide, a recent rockslide-debris flow that occurred in the Northern Apennines of Italy is studied through field investigation and numerical simulation. The run-out process of this landslide is simulated by an improved depth-averaged model, paying special attention to analyzing the influence of slope gradient and gully channel. The simulation results are compared with the detailed field data of entrainment and deposition distributions. It shows that the depth-averaged model can reasonably simulate the entrainment and deposition characteristic of this landslide by adopting different basal friction strengths for the rockslide region and debris flow region. Entrainment occurs in both high and low slope gradient zones. However, entrainment can only be observed in the high slope gradient zones, while in the low gradient zones, the post-failure topography shows accumulation and deposition. The simulation results also demonstrate that the presence of a gully channel is a key factor in determining landslide mobility and run-out distance. In comparison to a landslide with similar size and geological settings but without a gully channel, the run-out distance is much less, and the landslide does not develop into a flow.

Numerical study of the runout behavior of the Kamenziwan landslide in the Three Gorges Reservoir region, China

Numerical study of the runout behavior of the Kamenziwan landslide in the Three Gorges Reservoir region, China

Simulation of runout behavior of submarine debris flows over regional natural terrain considering material softening

Evaluation of regional submarine debris flows is critical for quantitative assessment of vulnerable areas and reasonable design of geohazard mitigation measures. In this article, an efficient numerical model for kinematics of regional submarine debris flows is developed. The proposed model can simulate the runout process and morphological evolution of submarine debris flows over natural 3D terrain by solving 1D depth-averaged governing equations in a geographic information system (GIS). A strength softening equation is introduced to capture the degradation of sliding material strength during the runout process. The model is validated by a flume test, two slump tests, and a real case history of submarine debris flow (St Niklausen slide). Applications to Shenhu area, South China Sea, are presented to demonstrate the ability of the proposed model over complex natural terrain and the importance of considering material softening. Results show that the proposed model is capable of simulating the whole debris flow process and tracking the propagation of the sliding material. Simulation of submarine debris flow without material softening will underestimate the disaster consequences. In addition, the influences of the ambient fluid and the yield strength of the sliding material on its runout behavior are also discussed.

Exploring new methods to analyse spatial impact distributions on debris‐flow fans using data from south‐western British Columbia

AbstractPredicting the spatial impact of debris flows on fans is challenging due to complex runout behaviour. Debris flow mobility is highly variable and flows can sporadically avulse the channel. For hazard and risk assessments, practitioners typically base the probability of spatial impact or avulsion on their experience and expert judgement. To support decision‐making with empirical observations, we studied spatial impact distributions on 30 active debris‐flow fans in south‐western British Columbia, Canada. We mapped 146 debris‐flow impact areas over an average observation period of 74 years using orthorectified airphotos, satellite imagery, topographic base maps, LiDAR data, orthophotos, and field observations. We devised a graphical method to convert our geospatial mapping into spatial impact heat maps normalized by fan boundaries, enabling comparison of runout distributions across different fans. About 90% of the mapped debris flows reached beyond the mid‐points of fans, while less than 10% avulsed more than half‐way across the fan relative to the previous flow path. Most avulsions initiated at distances of 20% to 40% of the maximum fan length from the fan apex and upstream of the fan intersection point. Large volume events tend to be more mobile in the down‐fan direction, but the relation between volume and cross‐fan runout (e.g., avulsions) is more complex. Differences in spatial impact distributions can be explained, in part, by the degree of fan incision and whether a fan is truncated at its toe by a river or lake. There were no significant differences in spatial impact distributions based on the geology of the source area, sediment supply condition, or hydrogeomorphic process classification.

Quantitative hazard analysis and mitigation measures of rockfall in a high-frequency rockfall region

The runout behavior of rockfall is mostly determined by the terrain and its mechanical parameters. The two factors can be significantly changed in a short period of time due to rockfall deposits in high-frequency rockfall regions. In this paper, a self-evolution process of rockfall from the Hongshiyan post-earthquake rock slope is observed and analyzed. This self-evolution process of the rockfall is the consequence of the re-occurrences of a large number of rockfall events in a short period of time, which lead to an increase in the elevation, slope angle, and hardness of the terrain, and aggravate further the severity of subsequent rockfall disasters. In order to analyze the self-evolution process, numerical simulations based on a probabilistic model were carried out on eight different conditions to analyze the interaction between the rockfall and different ground surface. The corresponding rockfall hazard was then analyzed according to a quantitative assessment method. The statistics of the average class (AC) and mitigation index (MI) of the rockfall were proposed to quantify the rockfall characteristics in different conditions. The effectiveness of structural and non-structural rockfall protection measures in high-frequency rockfall areas was discussed. An interim non-structural measure that addresses the self-evolution of rockfall is proposed to improve the mitigation efficiency, which can also reduce the maintenance cost.

Probabilistic analysis of a discrete element modelling of the runout behavior of the Jiweishan landslide

AbstractLandslide is one of the most destructive geohazards around the world. The destruction of a landslide can be estimated from its deformation and runout behaviors, which might be simulated with numerical software such as particle flow code (PFC). In the PFC simulation of the runout behavior of a landslide, the results are dependent upon the particle‐particle contact micro‐parameters (e.g., contact modulus and friction coefficient). The calibration of the micro‐parameters of the PFC models is a challenge and various uncertainties are involved. The uncertainty in the selection of the modelling parameters leads to uncertainty in the simulated runout behavior of the landslide. As a result, the damage potential of the landslide cannot be accurately evaluated. To this end, this paper presents a probabilistic analysis of the runout behavior of the Jiweishan landslide, in which the uncertainty in the selection of the particle‐particle contact micro‐parameters is explicitly considered. Here, the input micro‐parameters are modeled as discrete random variables, the possible realizations of which are obtained through an orthogonal analysis of the PFC simulation‐based uniaxial compression tests. The derived possible realizations of the micro‐parameters are then adopted as the inputs to the built model of the landslide. With the results obtained from these PFC simulations, the runout behaviors of the Jiweishan landslide, such as the runout distance and the deposit thickness, are studied probabilistically. The results provide an improved estimate of the landslide runout behavior and further aid in making an informed risk assessment of the landslide.

A comparative analysis of attabad landslide on january 4, 2010, using two numerical models

This study determines the runout behavior (Attabad landslide, Hunza, Pakistan) of one of the biggest landslides in Pakistan's history, along the highest and strategically most important highway of the world. On January 4, 2010, at 08:36 local time, 45 Mm3 of rock mass flowed down the hill slope for 1060 m and fell in Hunza River, thus blocking the river's flow and making an artificial dam. This paper examines the landslide's failure process based on seismic data obtained from a published paper. The average velocity of the slide was found to be 14.32 m/s. To better understand the landslide dynamics and failure phenomena, a numerical simulation was conducted using DAN3D to simulate displaced materials' runout behavior. Simulation results indicate that the slope's failure lasted for 70 s, which is in good agreement with seismic wave recordings of 70 s. The combined frictional–Voellmy model obtained the most accurate results for simulation. Further, to verify the results, another simulation was run using RAMMS debris flow software; it was found that the results of both the software's are in good agreement. It is expected that the selected model and its parameters will help understand similar kind of rock avalanches in the area, which will help concerned agencies improve landslide prediction along Karakoram Highway.

Influence of biopolymers on the rheological properties of seafloor sediments and the runout behavior of submarine debris flows

Submarine debris flows are mass movement processes on the seafloor, and are geohazards for seafloor infrastructure such as pipelines, communication cables, and submarine structures. Understanding the generation and run-out behavior of submarine debris flows is thus critical for assessing the risk of such geohazards. The rheological properties of seafloor sediments are governed by factors including sediment composition, grain size, water content, and physico-chemical conditions. In addition, extracellular polymeric substances (EPS) generated by microorganisms can affect rheological properties in natural systems. Here we show that a small quantity of EPS (~ 0.1 wt%) can potentially increase slope stability and decrease the mobility of submarine debris flows by increasing the internal cohesion of seafloor sediment. Our experiments demonstrated that the flow behavior of sediment suspensions mixed with an analogue material of EPS (xanthan gum) can be described by a Herschel–Bulkley model, with the rheological parameters being modified progressively, but not monotonously, with increasing EPS content. Numerical modeling of debris flows demonstrated that the run-out distance markedly decreases if even 0.1 wt% of EPS is added. The addition of EPS can also enhance the resistivity of sediment to fluidization triggered by cyclic loading, by means of formation of an EPS network that binds sediment particles. These findings suggest that the presence of EPS in natural environments reduces the likelihood of submarine geohazards.

Experiments on granular flow behavior and deposit characteristics: implications for rock avalanche kinematics

Experimental dry granular flow with a flume configuration is a basic model used for simulating rock avalanches. Despite the establishment of many empirical relationships between single parameters and runout behavior, very limited attention has been focused on the corresponding mechanisms. To address this issue, the granular flow behavior and associated deposit characteristics are researched herein via a series of flume tests with varying grain size and volume conditions. The results show that the flow behavior is correlated with the grain size and volume of the granular flow. With decreasing grain size and increasing volume, a transition of the internal shear behavior from uniformly distributed shear-to-shear localization at the bottom is found, which is claimed to affect the global shear behavior. The global shear behavior, which is characterized by the global shear rate, is found to be correlated with the granular flow mobility. The reduction in the global shear rate related to the grain size decreases the equivalent friction angle, thus increasing the flow mobility. On the other hand, the Savage number correlates positively with grain size, indicating a transformation from a dense regime to an inertial regime with increasing grain size. This transformation results in discontinuous deformations in deposits, such as the attenuation of flow-like morphologies and increases in particle mixing.

Investigation and dynamic analyses of rockslide-induced debris avalanche in Shuicheng, Guizhou, China

On July 23, 2019, a large catastrophic landslide occurred in Shuicheng, Guizhou, China. It was a rapid and long run-out landslide that resulted in more than 50 casualties. The displaced materials traveled an approximate distance of 1250 m, with a descending height of around 465 m. In this paper, seismic record analyses and numerical simulation were conducted to determine the run-out behavior of the Shuicheng landslide. To determine the main characteristics of the landslide, geological and climatic settings were obtained by conducting a detailed field survey. The DAN3D model was used to simulate the propagation and run-out process of the landslide. It was observed that a combined Frictional-Voellmy model provides assuring results in simulating the Shuicheng landslide. The total duration of the landslide is 60 s with an average velocity of 20 m/s. The maximum velocity is estimated to be 40 m/s along the right bank of the valley, while a high initial velocity of 24 m/s was recorded at the initiation of the landslide. Seismic records obtained from the nearby seismic stations were used to calculate the location of the event and interpret the dynamic process of the landslide. The Arias intensity, Hilbert-Huang transform, and Empirical mode decomposition were used to obtain a detailed time history of the landslide. The results of the numerical simulation and seismic record analyses are expected to portray the process of similar landslides. This will improve the accuracy of landslide hazard mapping in the region.