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.
This paper aims to present several approaches for fluid–solid coupling applied in landslide river blocking simulations based on the Abaqus software. These approaches include the coupled Eulerian ...Lagrangian (CEL) model and the finite element method-smoothed particle hydrodynamics (FEM-SPH) model, which use discrete finite element meshed blocks to simulate landslides, and use continuum models of Eulerian material and SPH material for river simulations, respectively. Another approach is to use the Eulerian model with Eulerian material to simulate landslides and river at the same time. A physical model of an elastic plate subjected to time-dependent water pressure was applied to validate the selected methods in the fluid–solid coupling. The process was recorded and corresponding numerical simulations were performed. The results show that the simulated plate and water behavior is consistent with the physical model in all simulations. Afterwards, the methods were applied to a real-scale rock avalanche river blocking simulation and the processes of sliding mass movement, impulse wave behavior, and the formation of landslide dams were described and analyzed. Applied Eulerian materials and discrete finite element meshed blocks were used to simulate the sliding mass and similar sliding movement characteristics were obtained. However, discrete blocks have shown better potential for simulating more complex situations and processes leading to better mass movement and deposition results. In addition, discrete finite element meshed blocks and other similar discontinuum models can better reflect the structural characteristics of the source rock in the simulation. As for the impulse wave, the use of Eulerian model for simulating the sliding mass will lead to an abnormally high wave height. Whether to consider a water effect and how to consider it affect the shape of the landslide dams and the simulation results show the importance of fluid–solid coupling in the landslide river blocking simulation. Similar and accurate results can be obtained using the Eulerian method and the SPH method for water simulation. However, it is worth noting that the existence of the Eulerian boundary makes the Eulerian method a better option for simulating more complex flow conditions compared to the SPH method. The meshless characteristics of the SPH method make it more computational efficient provided the fluid volume is constant and the final scale of the model is uncertain.
This study used a three-dimensional model based on the finite-discrete element method-smoothed particle hydrodynamics (FDEM-SPH) coupling approach to reconstruct the 11 October 2018 Baige landslide ...that blocked the Jinsha river. The numerical model simulated the dynamic process of the landslide by FDEM, while the SPH simulated the behavior of the river water. The landslide deposit area and the water-eroded area in the FDEM-SPH simulation agree well with the results of the field investigation. According to the simulation, the main duration of the Baige landslide was 80 s. The peak average speed of the landslide was 34.4 m/s, while the local speed of the sliding mass reached a maximum velocity of 70 m/s. The tensile effect and the shear effect caused isotropic dispersive stress which caused the dynamic and violent fragmentation of the landslide. The model also simulated the variation of kinetic energy, the accumulated friction dissipation, and the fracture energy of the sliding mass with time. After the sliding mass ran into the river, the landslide triggered a wave, which rapidly dispersed due to the subsequent mass movement. The front part of the sliding mass pushed some of the river water to the opposite bank where the wave reached a height of 120 m. The results of the FDEM-SPH model, the particle flow code (PFC) model, and the depth-integrated shallow-water flow (DISWF) model are compared and analyzed concerning studying landslides that block rivers. Three types of evolution mechanisms of high-level flow-like landslide-induced waves in deep river valleys are proposed in this paper.
•A novel fluid-solid coupling approach based on FDEM-SPH is used for landslide blocking river.•Dynamic process of the Baige landslide blocking river is shown clearly.•Evolution modes of high-level fluid-like landslides blocking rivers in deep valley area are proposed.
Tensile cracks in soil slopes, especially developing at the crown, have been increasingly recognized as the signal of slope metastability. In this paper, the role of crown cracks in natural soil ...slopes was investigated and its effect on stability was studied. A numerical modeling of slope and simulation of tensile behavior of soil, based on the Extended Finite Element Method (XFEM), was used. A numerical soil tensile test was applied to validate the use of XFEM on tensile behavior of soil before the simulation. Slope failure was simulated by using the Strength Reduction Method, which determines the potential slip surface of slope. The simulation results indicate forming of crown crack in natural soil slopes when the plastic zone starts penetrating. Therefore, it is reasonable to consider the crown crack as the signal of slope metastability. A sensitivity analysis shows the effect of cracking on slope stability if cracks are at the position of the tension zone. The stress variation analysis, from the surface slip deformation, reveals that the slope is at a state of compressive stress. When plastic zone starts penetrating, the upper part of slope generates tension zone, but the extent of tension zone is restricted by the slope failure. This suggests why tensile cracks are difficult to form and stretch in the deep part of the slope. The implementation of XFEM on slope stability analysis can be used for assessing the tensile strength of soil and forecasting the time of slope failure related disaster.
A large number of landslides have occurred in the upstream reaches of the Jinsha River, Tibetan Plateau due to the intensity of tectonic movement in the area. Remote sensing and field investigation ...indicate that one of them, the Samaoding paleolandslide, previously blocked the river. Various river-blocking phenomena are well preserved, including the old landslide dam and deposits, fluvial sediments, and hydrostatic sandy sediment. To better understand the evolution of the Samaoding landslide, the authors carried out thermoluminescence (TL) dating and numerical simulations. The TL analysis shows that the landslide occurred at 10.6 ± 0.5 Ka BP. Discrete element method (DEM) simulation of the landslide based on landform restoration provided results that are consistent with field observations. The simulation indicates that the entire landslide process lasted for 80 s, and the sliding mass reached a maximum velocity of 64 m/s. The landslide formed a landslide dam with a length of 1900 m, a width of 600 m, and a depth of 200 m. The simulation results show that the level of the riverbed at that the time of the landslide was at least 25 m higher than it is today. On the combined basis of the simulation results and field observations, the authors propose explanation that the following valley evolution sequence occurred after river blocking. The landslide dam experienced flood overtopping and then was eroded until it had mostly had been transported away by river flow, and the river then rapidly incised the bedrock to form the present-day landform. Based on the field investigations, the authors summarize the failure mechanism of steep-inclined antidip rockslides and found that tectonics play an important role in the formation of landslide dams (or trigger of landslides) and the failure of landslide dams in an active tectonic environment of Tibetan Plateau.
•The Samaoding paleolandslide occurred at 10.6 ± 0.5 Ka BP according to TL analysis.•Detailed run out process of the Samaoding paleolandslide was well reproduced by DEM simulation.•The relative incision rate of the study area is at least 250 cm/ka in the past 10,000 years.•The evolution of the Samaoding paleolandslide is proposed.•Failure mechanism of steep-inclined antidip rockslides is summarized.
Catastrophic landslides occur frequently at large waste dumps, causing huge losses of lives and environmental degradation. In this study, Zhujiabaobao iron mine waste dump was surveyed and found to ...be unstable during a field investigation in April 2016. A failure potential assessment was undertaken for the waste dump; this is crucial for the prediction and mitigation of landslides hazards. Reconnaissance, geomorphological analysis, and laboratory experiments were carried out to provide basic data, and a three-dimensional waste dump model was constructed. To consider ground cracks in the waste dump and acquire information about potential sliding mass, an extended finite element model (XFEM) based on strength reduction technique was applied. An analysis shows that the factor of safety (FOS) of waste dump is 1.22, not very stable according to “The technical code for building slope engineering (GB50330-2013)” published by Chinese ministry of Housing and Urban-Rural Development, and the potential failure volume is 45 × 104 m3. Then, the potential landslide and debris flow due to slope failure were simulated using the software SFLOW based on a free-surface shallow water model (SWM). The landslide simulation considers different water contents of sliding mass, reflected in parameter Cv (sediment concentration by volume), whereas debris flow simulation was designed for 20, 50, 100, and 200-year return periods. The results show that with the decrease in Cv, the speed of sliding mass increases, and the run-out distance of landslide increases. However, even the farthest influence distance does not reach downstream buildings. The debris flow can pile up in front of gully mouth and even run into the Jinsha River. Therefore, once a landslide has occurred or when a lot of loose material is present, corresponding management measures (such as cleaning the material or setting the retaining wall) and a forewarning system should be developed to prevent huge damage caused by debris flow.
•A method combining FEM and SWM for assessing waste dump failure potential.•The cracks have been considered in the model of stability analysis via XFEM.•The numerical model can fully consider real topographical conditions.
The objective of this study was to identify the areas that are most susceptible to landslide occurrence, and to find the key factors associated with landslides along Jinsha River and its tributaries ...close to Derong and Deqin County. Thirteen influencing factors, including (a) lithology, (b) slope angle, (c) slope aspect, (d) TWI, (e) curvature, (f) SPI, (g) STI, (h) topographic relief, (i) rainfall, (j) vegetation, (k) NDVI, (l) distance-to-river, (m) and distance-to-fault, were selected as the landslide conditioning factors in landslide susceptibility mapping. These factors were mainly obtained from the field survey, digital elevation model (DEM), and Landsat 4–5 imagery using ArcGIS software. A total of 40 landslides were identified in the study area from field survey and aerial photos’ interpretation. First, the frequency ratio (FR) method was used to clarify the relationship between the landslide occurrence and the influencing factors. Then, the principal component analysis (PCA) was used to eliminate multiple collinearities between the 13 influencing factors and to reduce the dimension of the influencing factors. Subsequently, the factors that were reselected using the PCA were introduced into the logistic regression analysis to produce the landslide susceptibility map. Finally, the receiver operating characteristic (ROC) curve was used to evaluate the accuracy of the logistic regression analysis model. The landslide susceptibility map was divided into the following five classes: very low, low, moderate, high, and very high. The results showed that the ratios of the areas of the five susceptibility classes were 23.14%, 22.49%, 18.00%, 19.08%, and 17.28%, respectively. And the prediction accuracy of the model was 83.4%. The results were also compared with the FR method (79.9%) and the AHP method (76.9%), which meant that the susceptibility model was reasonable. Finally, the key factors of the landslide occurrence were determined based on the above results. Consequently, this study could serve as an effective guide for further land use planning and for the implementation of development.
The Qulong paleolandslide dam event lies in the Benzilan-Batang zone of the upper Jinsha River. The Jinsha River is one of the most extensive water resources in southwest China. Here, the geological ...environment is complex, and the tectonic activity is intense. Thus, landslide dam events occur frequently, forming large barrier lakes. Analyzing and understanding these events is vital to ensure the safe development and utilization of land and water resources in the Jinsha River valley. In this study, the Qulong paleolandslide dam event, which formed a large barrier lake, is analyzed in detail. The topographic and grain-size analyses of the barrier lake's Qulong gully and lacustrine sediments imply that the Qulong paleolandslide occurred during the last interglacial period. The instability of moraine in the source area caused the landslide dam event that forms a rapid landslide and then transformed into a high-speed clastic flow. Historical data indicate that more than 90% of barrier lakes along the Jinsha are earthquake-triggered landslides, so the relationship between magnitude and epicenter distance of earthquake that induced the Qulong paleolandslide are calculated by Newmark method. The SFLOW software has been used to examine the post-failure evolution and movement characteristics of the Qulong paleolandslide. The results show that the speed of clastic flow reaches 41 m/s or so, and the clastic flow blocks the ancient Jinsha River channel whose thickness reaches 100 m or so, the largest up to 111 m, and its length is more than 4.5 km. Moreover, the high-speed clastic flow runs over the front of the Yinduba platform.
With the rapid process of urbanization, more and more infrastructures are inevitably built on problematic soils, which require improvement and reinforcement. In this study, a novel material ...Sulfur-Free Lignin (SFL), which is a by-product of bioethanol industry, was used to improve the soil's geotechnical behavior as a sustainable, non-toxic and eco-friendly stabilizer. To systematically investigate the geotechnical properties of SFL-stabilized soil, the natural soil was modified by adding five different contents (3, 7, 10, 12 and 15%) and then a series of geotechnical experiments including Unconfined Compressive Strength (UCS), Atterberg limits tests, electrical resistivity and pH were carried out after 1, 7, 28, 60-days curing. In addition, to investigate the stabilization mechanism, the mineral composition, function group and microstructure characteristic were also studied through X-Ray Diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR), Mercury Intrusion Porosity (MIP) and Scanning Electron Microscopy (SEM) tests. The test results demonstrate that with increasing SFL content, the electrical resistivity gradually decreases, on the contrary, the Atterberg limits show a slight increase. However, the pH values are unchanged indicating the SFL would not lead to pH contamination risk. The 10% SFL-stabilized soil after 60 days of curing shows the greatest strength, which increases about 600% compared to the natural soil. Furthermore, the relationship between stiffness and UCS is generally proportional. According to the results of MIP and SEM, the strength improvement can be attributed to a smaller total volume of pores, reduction in the mean size of the pores and stronger bonds formed by SFL between isolated grains. The results of XRD and FTIR tests reveal there is no new mineral nor function group generated after adding SFL. Above all, the natural soil stabilized by SFL shows a satisfactory engineering performance and it would be a win-win solution to utilize SFL as a soil stabilizer for soil improvement in civil engineering and for waste elimination in bioethanol industry.
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•SFL is a sustainable and eco-friendly by-product from green bioethanol production.•SFL was used to stabilize soft soil as earth-work material (such as subgrade and foundation).•SFL would not lead to pH contamination problems like traditional chemical stabilizers.•SFL-stabilized soil had a significant mechanical improvement reaching 1165 kPa at 10% content.•The stabilization mechanism was by physical bonds rather than chemical reactions.
In the Eastern Himalayan syntaxis, massive Quaternary loose deposits represent a typical product of abrupt topographic changes. Influenced by the Qinghai‐Tibet Plateau uplift and rapid river ...incision, the partial or complete failure of these deposits is a recurrent phenomenon in alpine‐gorge regions, posing substantial threats to major infrastructure development. Through topographic interpretation and field investigation, this study clarifies the geological features and genetic mechanisms of the Baimu ancient landslide deposit (BALD), located on the northern margin of the East Himalayan syntaxis. The surface deformation time series spanning October 2017 to December 2019 was estimated using employing multitemporal synthetic aperture radar interferometry. Then, the spatiotemporal deformation characteristics of the BALD was analysed by superposing terrain factors, and hazard division was implemented. The results indicate that high‐hazard zones are mainly distributed on high and steep free faces of the BALD. Deformation evolution and rainfall time series showed obvious correlation. Lastly, a generalized failure model is established for the BALD, which will serve as a valuable reference for disaster prevention and is applicable to the study of similar deposits in the Qinghai‐Tibet Plateau.
Through topographic interpretation and field investigation, this study clarifies the geological features and genetic mechanisms of the Baimu ancient landslide deposit (BALD). The spatiotemporal deformation characteristics of the BALD were analysed using SBAS‐InSAR, and hazard division was implemented by superposing terrain factors. The deformation evolution of the BALD showed an obvious correlation with rainfall time series. Erosion‐type progressive multistage failure emerges as a typical failure mode of the BALD.
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