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This paper presents the analyses of toppling response of layered reverse-dip slopes under the influence of geometric factors of slope angle, strata thickness and dip. The toppling response of reverse-dip slopes under different geometric factors is obtained by using the discrete element code UDEC. Then, a prediction model for toppling deformation is developed by utilizing support vector machine and the toppling-prone combinations of these geometric factors are determined from a total of 120 samples of reverse-dip slopes. The study has shown that the geometric model is a quarter of a spheroid with a slope angle of 80°, a strata dip of 80°, and a strata thickness of 0.19 m as the center. The length of the long equatorial radius of the spheroid is 31° (strata dip axial), that of the short equatorial radius is 21° (slope angle axial), and the polar radius is 0.075 m (strata thickness axial). And the ratio of long equatorial radius, short equatorial radius, and polar radius is 2.48:1.68:1.00.

Rocky desertification is an economic, social, and environmental problem, which refers to the processes and human activities that transform a karst area covered by vegetation and soil into a rocky landscape. The effects of different types of soil cover on ecohydrological processes during the revegetation of areas undergoing karst rocky desertification remain unclear. Taking different measures for different ecohydrological situations will benefit re-vegetation in karst rocky desertification areas. Monthly/heavy rainfall hydrochemical data and the δ13C of dissolved inorganic carbon (DIC) in karst water samples from January 2017 to December 2019 were obtained. This revealed the controlling mechanisms on hydrochemical processes by δ13CDIC under different soil cover conditions in the dip/anti-dip slopes of a karst trough valley in Ganxi Town, Chongqing City, southwestern China. Hydrochemical variations are controlled by climate, soil, and vegetation and show clear seasonality. The δ13CDIC values (−16.88‰ to −3.49‰) in the study area were higher than the theoretical value (−14.00‰). In addition, it was observed that rain accelerated soil erosion (R2=0.7) in the karst trough valley and human activities (exogenous acid) resulted in DIC loss. The slopes, soil, and bare rock cover on the dip slope were different from that on the anti-dip slope, leading to the difference in their re-vegetation statuses. In this study, we found that different vegetation restoration schemes and treatment measures should be implemented between the dip and anti-dip slope. The protection of soil and water resources, especially soil, is the key to ecological restoration in rocky desertification areas.

To clarify the scale effect of slope deformation, this study investigates the behaviors of dip slopes with various heights and geological properties using centrifuge and numerical modeling. Three types of physical and numerical models with different rock layer thicknesses and weak plane angles were constructed for analysis and validation. The models were subject to toe submersion to simulate the wetting deterioration condition. Based on the analysis results, the deformation, sliding, and debris accumulation of small slopes (a few meters high) may be insignificant. However, the deformation behaviors of higher slopes with the same angle (with a height of tens to a hundred meters) can be more severe and affect the whole slope, especially if the slope has a high weak plane angle with alternating thin rock layers. Some early warning signs, such as bulging-induced tension cracks close to the toe or the relative sliding of layers at the slope surface or crest, can produce more massive landslides or debris accumulation of the dip slopes, especially for high slopes.

Anti-dip slope that fails in the form of flexural toppling is commonly encountered in rock engineering. This paper presents an approach to calculate the local failure probability of the anti-dip slope susceptible to flexural toppling. The realization of this approach consists of four major steps: (1) establishing geo-mechanical model of the slope and generating physical parameters randomly using Monte Carlo simulation, (2) determining the demarcation of the toppling and sliding failure zones, (3) evaluating the stability state of each single column, and (4) deriving the local failure probability by an iterative calculation. A case study of the Mari landslide is analyzed by employing the proposed approach, and the Maxwell model is applied to reduce physical parameters with time. The results show that the instability grade increases gradually throughout the whole evolution process of the slope. In the incipient stage, particular attention should be paid to the middle–upper columns, which have the highest failure probabilities. However, as the slope deformation increases, all the columns should be taken into account since they have approximately the equal possibility of failure. A simplified slope model is employed to perform a parametric analysis. The results show that (1) the local failure probability of the slope tends to decrease with increases in the rock friction angle, rock tensile strength or interface friction angle, while increasing the rock unit weight leads to a higher probability of local failure; (2) the computation results are more sensitive to the uncertainty in the interface friction angle than that in the other three above-mentioned parameters; and (3) the maximum failure probability depends on the geometric parameters, including the column interface angle, slope angle, crest angle, slope height and column thickness.

A large catastrophic rock avalanche with a total volume of ~18.0 × 106 m3 occurred at 5:38 am, 24th June 2017, at Xinmo Village, Maoxian, Sichuan, China, resulting in 102 casualties (10 deaths, 3 injuries, and 89 missing). We have been conducting a geological and geomorphological investigation in and around the Xinmo landslide site since 2015, and we present our results here, including data obtained before and after the landslide event. The landslide, which had an initial volume of 4.46 × 106 m3 of its source area, was induced by rainfall on a previous landslide scar near the ridge top. This initial landslide then struck and remobilized older landslide deposits in the middle and lower parts of the slope, which subsequently buried Xinmo Village at the landslide toe. The landslide occurred on a dip slope of Triassic calcareous psammitic and pelitic schists. The bedding plane, which dips downslope to the south with an orientation of N80°W/48°S, and high-angle NE–SW striking joints bounded the landslide source area at its base and sides, respectively. Satellite image analysis and field observations of the slope of the landslide scar before and after the landslide strongly suggest that the beds in the source area had already begun gravitationally deforming (e.g., buckling) prior to the 2017 landslide. Moreover, pits on the slip surface were likely the result of the dissolution of calcareous material. Dissolution probably reduced the rock strength along the bedding plane. A rainfall event from the 16th to 24th of June 2017 probably dominated the groundwater drainage, and finally triggered the catastrophic rock avalanche. In addition to the 2017 landslide, the hillslope just to the east of the Xinmo landslide exhibits pronounced gravitational slope deformation, including “A-tent”-like structures and warps induced by buckling. This suggests that this slope could also fail like the Xinmo rock avalanche during a future rainfall or earthquake event.

A dip slope contains weak planes in the same dip direction along the slope face. In this study, a discrete element simulation was implemented to investigate the behavior of a dip slope under shaking table tests. The simulated dip slope model was first verified by testing under different horizontal excitations. Then, the influence of the slope angle and dynamic force on the deformation characteristics of the dip slopes was explored. The simulations provide detailed descriptions of the deformation processes and potential sliding mechanisms associated with the dip slopes. The results of this study are summarized as follows: (1) Two types of slope sliding, namely differential and complete, were recognized. The model with a dip angle lower than 20° was more stable, and differential sliding developed gradually during external excitation. In the model with a dip angle higher than 20°, the external excitation easily triggered complete sliding. (2) For threshold slope angles higher than 20°, the behavior of the dip slope model changed from deformation to sliding, and the displacement within the models increased with increasing slope angle. (3) An increase in frequency led to a decrease in the trigger time for slope sliding. In addition, the slope angle was negatively correlated with the triggering time for sliding. (4) The amplification factor of peak ground displacement (PGD) increased as the slope angle increased. The amplification factors corresponding to low excitation frequencies were considerably lower than those for high excitation frequencies. In contrast to the trends for PGD, the amplification factor of peak ground acceleration (PGA) decreased as the slope angle increased.

At 5 am 24th June 2017, a catastrophic landslide hit Xinmo Village, Maoxian County, Sichuan Province, China. The slide mass rushed down from an altitude of 3400m and traveled 2700 m in a high velocity. The 13 million m3 deposition buried the whole village and caused about 100 deaths. The source area of the landslide is located in a high steep slope, average slope angle is 40o and maximal angle is 65o. The strata are interbedded Triassic Zagunao Formation metamorphic sandstone and slate with the dip slope angle of 45°. Based on high-resolution satellite remote sensing image, UAV image, DEM data, and field investigation, failure mechanism, travel features, and deposit characteristics were analyzed. The results showed that this landslide was influenced by Songpinggou Fault zone. According to the topography before the failure, the landslide is located in the back scarp of an antecedent landslide induced by Diexi Earthquake in 1933. The bedding slope provided potential rupture surface. Historical seismic activities and long-term gravitational deformation caused rock mass accumulated damages. Weathering and precipitation weakened the rock mass and finally induced shearing and tension failure. A huge block detached from the top rock slope, pushed the past landslide deposits in the middle part, rushed out of the slope bottom in a high velocity and buried the Xinmo Village. The rapid movement entrained and brought the soil into the Songping Gully which recoiled with and bounced back from the opposite mountain.

This study investigated the effect of internal discontinuity on the dynamic response of a dip slope and evaluated the performance of Newmark’s theory on the sliding of a dip slope with multi-slip planes. A series of shaking table tests were performed under various geometric conditions to explore the dynamic behavior of a dip slope under different external excitations. The test results, including for deformation processes and critical accelerations, under various slope angles, slope sizes, and seismic intensities were examined and further compared with Newmark’s theory. The results of this study are summarized as follows: (1) two types of slope sliding (differential and complete) were determined. (2) Increasing the slope angle and the height of sliding mass tended to shorten the duration of slope deformation. (3) Critical acceleration of the slope increased gradually with increasing peak ground accelerations of input excitations; when the slope height and dip angle increased, the critical acceleration decreased. (4) The triggering time became earlier as the frequency of input excitation increased; the magnitude of sliding mass greatly depended on the amplitude of the input excitation. (5) By comparing critical acceleration between the experimental and theoretical results, Newmark’s theory was determined to overestimate critical acceleration during seismic-induced dip slope failure. This may cause unsafe evaluations, and sliding along existing discontinuities develops more easily in reality.

On June 24, 2017, a catastrophic landslide (Xinmo landslide) occurred on the left bank of Songping river in Diexi town, Sichuan Province, China. Based on field investigations, this paper tries to reveal the cause and mechanism of the initiation and development of the Xinmo landslide. Xinmo landslide is located in the so called “Minshan block.” This tectonic block is very active and generates many earthquakes. Among them, the 1933 Diexi Ms 7.5 earthquake which had an indispensable effect on the occurrence of the Xinmo landslide, whose distance to the recent Xinmo landslide is only 8.7 km. The 1933 earthquake triggered the collapse of the Qianxin gully, which damaged the rock mass forming the source of the Xinmo landslide and creating a free prominent ridge. The later 1976 Songpan Ms 7.2 earthquake and the 2008 Wenchuan Ms 8.0 earthquake further damaged the integrity of the rock mass in the source area of the 2017 Xinmo landslide. The Xinmo landslide developed on a typical bedding dip slope with metasandstone intercalated with a few thin bedded slate layers. The slate intercalation gives the slope a very low shear strength in the dip direction and the long term rainfall may have softened the slip zone and the locked section. These two aspects have promoted the occurrence of Xinmo landslide.

Slope failure is a widely observed phenomenon in the mountainous areas in Taiwan due to rainy climatic and fragile geological conditions. Landslides easily occur after intense rainfall, especially from typhoons, and, accordingly, cause a great loss of human life and property. At the northern end of the Western Foothill belt in northern Taiwan, Huafan University is founded on a dip-slope about 20° toward the southwest composed of early Miocene alternations of sandstone and shale. Data from continuous monitoring using inclinometers and groundwater gauges reveal that 6–10 mm/month of slope creeping occurs, and a potential sliding surface is then detected about 10–40 m beneath the slope surface. To understand the potential runout process of the dip-slope failure at the campus, particle flow code 3D models based on a discrete element method are applied in this study. Results of the simulation reveal a critical value of the friction coefficient to be 0.13 and that more than 90% of the campus buildings will slide down in 100 s when the friction coefficient is reduced to half the critical value. The weakening of the shear zone due to the rise of groundwater during rainstorms is assumed to be the main factor. Some suggestions for preventing landslide disasters are to construct catchpits to drain runoff and lower the groundwater table and to install a sufficient number of ground anchors and retaining walls to stabilize the slope.

Several related pre-event environment indices coupled with a 200-year event of Typhoon Morakot were used in this study to analyse landslide risk/scale for mapping and verifying the danger grade of watershed landslides. Risk analysis was modelled using maximum daily rainfall of the tested event as the hazard factor, and a complex indicator derived from indices of return period, road development and green deterioration as the vulnerability factor. The vulnerability factor was then modified using the slope to adjust the weight for excluding the flat areas and increasing impact of steep areas. A comprehensive indicator integrated from indices of river concave, headward erosion and dip slope was provided as the hotspot of potential large-scale landslides which were modified by vegetation index to correct sediment yield due to antecedent effects. Finally, sites with high potential large-scale landslide could be interpreted by the danger grade calculated from collapse risk/scale analysis. The results show that the higher the danger grade, the greater the collapse ratio; and the coefficient of determination for the relationship is greater than 0.9. The model developed in this study for accurately estimating the risk/scale of rainfall-induced landslide can be fulfilled.

Dip-slope mapping is a fundamental task for landslide investigation and mitigation. However, most dip-slope mapping methods involve visual interpretations and manual processes that are inevitably subjective and time consuming. The advent of high-resolution digital elevation models (DEM) and increases in computing power have provided opportunities to improve the dip-slope mapping process. This study proposes a polygon auto-tracing method for generating dip-slope maps based on airborne Light Detection and Ranging (LiDAR) data and a customized spatial analysis toolset developed in Python. This method requires the input of strata boundaries produced for sedimentary terrain based on 2 m resolution LiDAR DEMs. The method begins by deriving the raster layer of the dip direction of the bedding, and it then executes a series of raster calculations among the three raster layers slope, aspect, and dip direction to extract the dip-slope raster cells. Using the clustering pattern of the dip-slope raster cells, we implement the Point-Density analysis tool to determine the dip-slope areas. The ArcGIS ModelBuilder platform is used to lay out an automated workflow for the proposed polygon auto-tracing method using the customized toolset. For demonstration purposes, we successfully mapped 298 dip slopes in the study area, which frequently experiences dip-slope landslides and is located in the sedimentary terrain of northern Taiwan. The dip-slope mapping results were compared and validated against two government-funded visually interpreted dip-slope maps. Our dip-slope mapping results were also used in a daylight analysis along major freeways to identify potential locations of daylighted dip slopes.

Based on the combination of FLAC3D software and strength reduction method, the applicability of three kinds of instability criterion of the stability of dip slopes with interbeddings of weak and hard rocks is studied. Then the failure process, failure mode and stability of the slopes are analyzed. The results show that: (1) the maximum unbalance rate affects the final calculated results; there is no certain relation between the convergence of calculation and the slope stability. The convergence of the displacement curves of key points and the ultimate displacement values should also be concerned to determine the slope stability. The maximum unbalance rate and the amplitude of the reduction affect the determination of the characteristic point in the displacement curve. It is difficult to quantitatively evaluate the shear strain rate when judging the slope stability, the judgment is not convenient and the error is large. Combining with calculation convergence criterion and feature point displacement mutation criterion is helpful to improve the accuracy of judgment on the limit state of the slope. (2) Slope deformation and failure process can be roughly divided into four stages qualitatively; the rock mass has buckling failure can be divided into three stages according to the deformation characteristics. The potential shear export of slope with buckling failure locates above the slope toe. Different combinations of weak and strong rock thickness does not affect the failure mode of slope, which all bellows to buckling failure mode, but it will affect the slope stability coefficient; with the increase of the thickness of strong rock and weak rock, the stability coefficient increases. If the thickness of the strong rock increases, the stability coefficient increases as well when the thickness ratio is constant.

The 17 June 2017 rock avalanche in the Karrat Fjord, West Greenland, caused a tsunami that flooded the nearby village of Nuugaatsiaq and killed four people. The disaster was entirely unexpected since no previous records of large rock slope failures were known in the region, and it highlighted the need for better knowledge of potentially hazardous rock slopes in remote Arctic regions. The aim of the paper is to explore our ability to detect and locate unstable rock slopes in remote Arctic regions with difficult access. We test this by examining the case of the 17 June 2017 Karrat rock avalanche. The workflow we apply is based on a multidisciplinary analysis of freely available data comprising seismological records, Sentinel-1 spaceborne synthetic-aperture radar (SAR) data, and Landsat and Sentinel-2 optical satellite imagery, ground-truthed with limited fieldwork. Using this workflow enables us to reconstruct a timeline of rock slope failures on the coastal slope here collectively termed the Karrat Landslide Complex. Our analyses show that at least three recent rock avalanches occurred in the Karrat Landslide Complex: Karrat 2009, Karrat 2016, and Karrat 2017. The latter is the source of the abovementioned tsunami, whereas the first two are described here in detail for the first time. All three are interpreted as having initiated as dip-slope failures. In addition to the recent rock avalanches, older rock avalanche deposits are observed, demonstrating older (Holocene) periods of activity. Furthermore, three larger unstable rock slopes that may pose a future hazard are described. A number of non-tectonic seismic events confined to the area are interpreted as recording rock slope failures. The structural setting of the Karrat Landslide Complex, namely dip slope, is probably the main conditioning factor for the past and present activity, and, based on the temporal distribution of events in the area, we speculate that the possible trigger for rock slope failures is permafrost degradation caused by climate warming. The results of the present work highlight the benefits of a multidisciplinary approach, based on freely available data, to studying unstable rock slopes in remote Arctic areas under difficult logistical field conditions and demonstrate the importance of identifying minor precursor events to identify areas of future hazard.

Bedding dip has an important influence on soil detachment and flow hydrodynamics in a karst trough valley. The laboratory rainfall simulation was conducted with three bedding dips (bare slope, dip slope and anti-dip slope) under three rainfall intensities (30, 60, 90 mm h−1). The characteristics of soil detachment and hydrodynamic parameters were assessed, including water flow shear stress, stream power, unit stream power and unit flow energy. The significant effects of bedding dips and rainfall intensities and their interactions on soil detachment and hydrodynamic parameters were examined. The results showed that (1) the soil detachment rate decreased with increasing rainfall duration, and the soil detachment rate in 30° bedding dip of dip slope was much larger than those in bare slope and anti-dip slope in most rainfall intensities; (2) the 60° bedding dip of dip slope was the threshold that controlled the stream power, unit stream power and unit flow energy increased or decreased under different rainfall intensities; and (3) the soil detachment rate had extremely significant positive power relationships with water flow shear stress, stream power, unit stream power and unit flow energy. Meanwhile, the stream power was the most suitable parameter for predicting soil detachment in a karst trough valley slope. Therefore, these results could provide useful information for soil erosion prediction in a karst trough valley.

Existing fan-delta depositional models for lacustrine basins do not adequately address significant wave- and storm-related processes. However, in many lakes, such high-energy processes can be effectively driven by winds. As such, the prevailing wind direction determines the propagation direction of wind-induced waves. Observations from modern examples show that wave-dominated deposits commonly exist on one side of the lake, and their sedimentary processes are completely distinct from those on the opposite side. However, equivalent deposits have seldom been identified from subsurface data. We present an ancient example from the Upper Tongbomiao Formation in the Tanan Depression (Tamtsag Basin, Mongolia), which was previously interpreted as a fan-delta depositional system. Based on extensive core investigations, eighteen lithofacies, six lithofacies associations and two genetic deposition systems are identified, and a new sedimentological interpretation is proposed comprising a wave-dominated clastic littoral system in the western half-graben dip slope and a fluvial-dominated fan-delta system in the eastern half-graben. Sediments within the eastern half-graben unit include braidplain, fan-delta front and prodelta environments, while those within the western half-graben dip slope unit comprise dominantly alluvial fan, wave-reworked beach, storm-affected shoreface and offshore sediments. The strikes of the sediments in the western half-graben dip slope unit are parallel to the westward shoreline trend, while the progradation direction of sediments in the eastern half-graben unit is perpendicular to the eastern shoreline. This indicates approximately northwestward-propagating waves that were possibly driven by southeasterly winds, which has implications for understanding the prevailing wind direction in Northeast Asia during the depositional period. Other factors contributing to the preservation of these two distinct sedimentary systems are the paleotopography and subsequent climate shift towards more humid climatic conditions which intensified sediment supply and hydrodynamic conditions that were able to rework the sediments.

Natural soils often exhibit rotated transverse anisotropy due to various geological processes (e.g., tectonic movement, filling and soil deposition), and the trend of soil strength usually changes with depth. This study combines rotated transverse anisotropy with non-stationary random field (RF) to investigate the reliability and failure mechanism of a slope under undrained conditions. Two scenarios of non-stationary RF are considered: (a) the trend of soil strength increases along depth; (b) the trend increases along the direction perpendicular to bedding. It is found that the expected performance levels of slope reliability would be significantly different under different directions of the trend. When the undrained shear strength increases along the direction perpendicular to bedding, the changes of slope reliability and sliding consequence would be sensitive to the dip angle of strata. Besides, the failure mechanism can be affected by the direction of the trend and strata orientation. Generally, shallow failure is more likely to occur on the dip slope when soil strength increases along the direction perpendicular to bedding, while for reverse slope with soil strength increasing perpendicularly to the bedding, deep failure mechanism is significantly dominant.

A natural hillslope developing into a landslide shows ground cracks and topographic deformation. Geomorphological and subsurface investigations using appropriate methodology are essential to understand the failure mechanisms and stability of a hillslope. Huafan University campus located on a dip slope in northern Taiwan is facing a potential landslide hazard. Slope movement was detected through the development of ground cracks and persistent deformation of campus buildings and facilities. To monitor the sliding behavior of the dip slope, a nail network consisting of 144 ground monitoring points was set in 2001, and its coordinates were measured using conventional traverse surveying twice a year until 2017. The 17-year surficial surveying results were presented as a time series of displacements with constraints of geometry and distribution of ground cracks and underground observations. The long-term surveying results reveal multiple potential sliding blocks within the Huafan University campus. A model of landslide movement with a listric sliding surface is proposed. Additionally, from the velocity field derived from the monitoring points, the horizontal strain rates of the slope are estimated. The pattern of strain rates indicates that a plausible fault passing through the campus may have affected the movement of the dip slope. The long-term surface monitoring of a potential landslide slope in this study provides a reliable and economical way to understand the mechanism of movement behavior of the slope and evaluate slope stability.

Large rock avalanches often result in loss of life and catastrophic damage to infrastructure far from their initial failure positions, predominantly due to their tremendous volumes, high velocities and long runouts. Studies of the surface morphologies and internal structures of rock avalanche deposits can reveal evidence of their movement and deposition mechanisms. Through field survey, satellite image interpretation and particle-size distribution analysis, we studied the ancient, long-runout Linka rock avalanche, which is next to the Nujiang River, southeast Tibetan Plateau. The Linka rock avalanche, with a source volume of ~310 Mm3 originated from a high, steep dip slope and then transformed into a channelized rock avalanche, showing high mobility with a superelevation back-calculated maximal velocity of 42 m/s, a travel distance of ~6200 m and a Fahrboschung of 0.24. The slope failure sequence consisted of an initial failure of an outer limestone slab and a second failure of an inner sandstone slab. The limestone avalanche had 2 or 3 surges, while the sandstone avalanche probably had only one surge. The high mobility of the Linka rock avalanche predominantly resulted from a buckling failure occurred on a high relief source, low-energy dissipation during the channelized flow, intensive rock fragmentation in the basal facies and possible water lubrication when propagating bi-directionally along the Waqu River. Our findings for the Linka rock avalanche support previous knowledge that multiple mechanisms have different roles at different stages in a long runout rock avalanche.

Geometry of planner geological structures can interact with topographic slope and cause different types of slope failure (e.g. wedge failure, dip slope failure, and toppling etc.). This study focus on how the tectonic foliation influences the landslide pattern in the southern Central Range of Taiwan. The tectonic foliations in this area range from pencil cleavage to schistosity depending on the increasing of metamorphic grade, and different foliations have different influences on the landslide behaviors. To describe the relation between foliation and topographic slope, we create the θ D value as the angle between the foliation dip direction azimuth and the topographic downslope direction azimuth at a given location. The location of landslides in the area with pencil cleavage has no preferential θ D value, and it suggests the landslide distribution has no correlation with foliation. The location of landslides in the area with well-developed slaty cleavage is mostly in the lower θ D value, which suggests the landslides are more likely located in the area where the foliation dip direction is parallel to the topographic downslope direction. The location of landslide in the area with schistosity is mostly in the high θ D value area, which suggests the landslides are more likely located in the area where the foliation dip direction is opposite to the topographic downslope direction.

A consequent slope comprises weak planes in the same dip direction along a slope face. This study investigated scale effects on the gravitational deformation of consequent slopes. A series of centrifuge model tests under simplified environmental conditions were performed. Particle image velocimetry (PIV) was then adopted to evaluate the displacement distribution from the centrifuge model test results. On the basis of the PIV results, the relationship between slope deformation and surface settlement was investigated. Subsequently, the discrete element method (DEM) was used to execute simulations to provide detailed descriptions of the crack development and failure mechanisms associated with consequent slopes at different scales. The results of this study are summarized as follows. (1) The slopes exhibited similar deformation patterns in the centrifuge model tests. As the gravitational force increased, the magnitude of slope deformation increased significantly. (2) A modified dimensional relationship of material parameters was proposed for DEM simulation. According to this relationship, the simulated deformation patterns were in strong agreement with the actual deformations at various slope scales. (3) According to the DEM simulations, for the slopes with the same slope and weak plane angles, more cracks and displacements were generated in the higher slopes, leading to a greater sliding volume.

Rock dip angle plays a significant role in surface hydraulic characteristics and leads to different spatial distribution of water and soil loss in Karst Trough Valleys. In this study, the rock dip angle effect on the hydraulic characteristics and soil detachment rate on dip/anti-dip slopes was explored via rainfall simulations and a steel experimental flume. The rainfall intensities ranged from 30 to 90 mm·h−1, and the rock dip angles varied from 10° to 60°. The results revealed that i) surface runoff on the dip slope was higher than that on the anti-dip slope, whereas underground runoff presented opposite results. The 30° rock dip angle presented the critical flow velocity for the anti-dip slope, and the flow velocity reduced as the rock dip angle of the dip slope increased. ii) Laminar water flow occurred on the dip/anti-dip slope (Re was

The Huafan University campus is located in the Ta-Lun Shan area in northern Taiwan, which is characterized by a dip-slope covered by colluvium soil of various depths. For slope disaster prevention, a monitoring system was constructed that consisted of inclinometers, tiltmeters, crack gages, groundwater level observation wells, settlement and displacement observation marks, rebar strain gages, concrete strain gages, and rain gages. The monitoring data derived from hundreds of settlement and displacement observation marks were analyzed and compared with the displacement recorded by inclinometers. The analysis results revealed that the maximum settlement and displacement were concentrated on the areas around the Hui-Tsui, Zhi-An, and Wu-Ming Buildings and coincided with periods of heavy rainfall. The computer program STABL was applied for slope stability analysis and modeling of slope failure. For prevention of slope instability, a drainage system and tieback anchors with additional stability measures were proposed to discharge excess groundwater following rainfall. Finally, threshold value curves of rainfall based on slope displacement were proposed. The curves can be applied for predicting slope stability when typhoons are expected to bring heavy rainfall and should be significant in slope disaster prevention.

Morphometric analysis and flash floods assessment were conducted for the watersheds of Ras En Naqb escarpment, south Jordan. The study area comprises of twelve small watersheds occupying the faulted-erosional slopes, and the dip slopes. The drainage network shows that dendritic and sub-dendritic patterns dominated the dip slopes, whereas trellis pattern characterized the faulted-erosional slopes. Stream orders range from fourth to sixth order. The mean bifurcation ratios vary between 4.2 and 5.38 for the dip slope basins, and between 3.5 and 5.0 for the faulted-erosional slope watersheds, indicating a noticeable influence of structural disturbances (i.e., faulting and uplifting), and rejuvenation of drainage networks. All watersheds have short basin lengths, ranging from 23.8 km to 42.2 km for the dip slope basins, and between 15.3 km and 45.4 km for the faulted-erosional slope catchments. This is indicative of high flooding susceptibility associated with heavy rainstorms of short duration. The circularity ratios range from 0.177 to 0.704 which denote that the catchments are moderately circular on the faulted-erosional slopes, and to some extent elongated on the dip slopes. The length of overland flow values ranges from 0.854 to 0.924 for the dip slope catchments, whereas LO values for the faulted-erosional slopes vary from 0.793 to 0.945 denoting steep slopes and shorter paths on both dip slope and faulted-erosional slope watersheds. Values of stream frequency range from 1.509 to 1.692 for the dip slope, and from 1.688 to 2.0 for the faulted-erosional slope catchments. FS values are also indicative of slope steepness, low infiltration rate, and high flooding potential. The watersheds of the dip slopes show lower values of form factor varying from 0.079 to 0.364, indicating elongated shape and suggesting a relatively flat hydrograph peak for longer duration. Similarly, values of Dd are high for catchments on the dip slope basins (1.709 - 1.85) and the faulted-erosional slope watersheds (1.587 - 2.0) indicating highly dissected topography, high surface runoff, low infiltration rate, and consequently high flooding potential. Furthermore, high relief values exist, ranging from 388 m to 714 m for the dip slope basins, and from 421 m to 846 m for the faulted-erosional slope catchments indicting high relief and steep slopes. Morphometric analysis, and flash flood assessment suggest that ten watersheds (83.3%) are categorized under high and intermediate flooding susceptibility, and the faulted-erosional slope catchments are more hazardous in terms of flooding. Thus the protection of Ma’an, El Jafr rural Bedouin settlements, and Amman-Aqaba highway from recurrent flooding is essential to ensure sustainable future development in Ras En Naqb-Ma’an area.

The first area is rock instability in conglomerates walls, and the second area is soil instability in a slope composed of sand gravel and shale in the south of the study area. In the first area, rock slopes were studied by fractures condition, slope morphology, measured engineering features of rocks, and then interpreted by Dips software to define the fracture types for analysis of block toppling. The rock slope of the area was modeled by Rock plan by adding water penetration and earthquake. The results showed that in dry condition these slopes were stable, but by penetrating water and saturation of the open spaces of the fractures, the block toppling will occur. Also, seismic activities in the area caused the instability of the slopes, and landslide will happen. In the second area, landslides were spoon-shaped type. To investigate the soil slope stability, the condition of slope was modeled by using soil engineering properties and measuring the morphological condition of the slope such as slope dip, layers thickness, layers dip and slope elevation. It was shown instability of the soil slopes. To stabilize the sliding areas, the dip changing method and formation of stepped-style slope were done. However, the new condition changed the formation of sliding areas in the upper most part of the stairs. The retaining walls formed from the local materials were applied to the slope to provide the desire stability.

The traditional slope stability analysis used the Factor of Safety (FS) from the Limit Equilibrium Theory as the determinant. If the FS was greater than 1, it was considered as “safe” and variables or parameters of uncertainty in the analysis model were not considered. The objective of research was to analyze the stability of natural slope, in consideration of characteristics of rock layers and the variability of pre-stressing force. By sensitivity and uncertainty analysis, the result showed the sensitivity for pre-stressing force of rock anchor was significantly smaller than the cohesive (c) of rock layer and the varying influence of the friction angle (ϕ) in rock layers. In addition, the immersion by water at the natural slope would weaken the rock layers, in which the cohesion c was reduced to 6 kPa and the friction angle ϕ was decreased below 14°, and it started to show instability and failure in the balance as FS became smaller than 1. The failure rate to the slope could be as high as 50%. By stabilizing with a rock anchor, the failure rate could be reduced below 3%, greatly improving the stability and the reliability of the slope.

This study proposed an in-depth multiscale analysis procedure to identify the dip slope area and assess dip slope stability and influencing area. The proposed analysis procedure comprised five stages: (1) identifying the potential area of a dip slope, (2) analyzing the possible failure types of the dip slope, (3) evaluating slope activity, (4) analyzing dip slope stability under the influence of possible triggering factors, and (5) assessment of the deformation and deposition area. To validate the proposed procedure, the Chaochouhu region of Taiwan was analyzed as a dip slope case. In stages (1) to (3), the scale of the utilized map and the precision of associated data were evaluated to identify the potential area of a dip slope, the possible failure types, and the activity of each slope unit. In stages (4) and (5), the processes of deformation and sliding in a high-activity slope unit were simulated using the discrete element method. The numerical model was first verified using in-situ monitoring data obtained from inclinometers. Subsequently, the model was used to predict the slope behavior under conditions of wetting deterioration of geomaterial. The multiscale analysis revealed comprehensive information regarding the dip slope. The application of the proposed approach would be useful to civil engineers for evaluating dip slope stability as well as to relevant authorities for planning hazard mitigation strategies.

Due to various geological processes, rotation of anisotropic soil fabric is commonly observed in nature. This paper investigates the effect of rotated anisotropy on slope reliability evaluation that considers conditional random field. In this investigation, slopes under undrained and drained conditions are studied under two kinds of sampling patterns. It is observed that the rotated anisotropy is a significant factor that influence the conditional simulation. For the conditional simulation, the uncertainty of the factor of safety (FS) and failure scale is generally the highest when the sampling points are distributed along the fabric orientation, and under such circumstance, the corresponding probability of failure Pf is observed to be the highest. Besides, a given sampling pattern leading to the uncertainty reduction relative to the unconditional simulation under the commonly investigated horizontal fabric pattern may not guarantee the uncertainty reduction under other fabric patterns for anisotropically deposited soils. Also, it is interesting to observe that due to the controlling to uncertainty by the conditional simulation, under rotated anisotropy a dip slope may be estimated to be safer than a reverse slope, and for a given fabric orientation, different sampling patterns may lead to significantly different probabilities of failure.

Rockslides commonly form a shear zone to accommodate their displacements. As such, the landslide history and mechanism must be recorded in the structural features of the shear zone. We investigated the basal shear zone of a 60-m-thick rockslide body with a lateral displacement of 200 m on a dip slope and found the evolutionary mechanisms of a basal shear zone of a rockslide. A basal shear zone on a dip slope is initiated along a lithologic boundary that is characterized by a high competency contrast, such as pelitic rock and greenstone or chert, and develops in the weaker rock, which was pelitic rock in the present study. The basal shear zone first develops with fracture of the rock mass, followed by intragranular fracturing of rock fragments. Shear strain by landslide gradually localizes to a narrow zone in the fractured zone to form a clayey layer by cataclasis of rock fragments. The rock fragments in the clayey layer become rounded by attrition, and the clayey layer finally obtains shear surfaces with slickensides.

On September 15, 2012, torrential rains carried by the peripheral circulation of Typhoon Sanba and the northeast monsoon induced a translational landslide near Pingguang Road in Xindian District of New Taipei City, Taiwan. The total volume of the landslide was ~162,000 m3. The sliding mass destroyed two houses across the stream and formed a landslide dam at the toe of the slope, constricting the stream. For the purpose of reducing sediment-relative hazard around mountainous area, the paper attempts to explore the dynamics and phenomenon of the landslide on dip slope. This study interpreted remote sensing images and terrestrial LiDAR scanning, conducted onsite surveys to obtain material parameters, and performed simulations using the discrete element method to reconstruction the post-event, in order to elucidate the mechanisms involved in the landslide process. Survey results revealed complex geological conditions with tension cracks spreading in all directions at source area. This facilitated the infiltration of surface runoff into weak surfaces and raised groundwater levels. Slope failure may occur along the stratum boundary once the intrinsic shear strength of regolith drops below a critical value. The results of numerical simulation reveal that at 80 s after the Pingguang stream landslide began, a maximum deposition depth of 20 m had been reached. The sliding mass cut off the stream and pushed the stream flow roughly 35 m to the southeast. Because the slope materials surrounding the study area and the landslide-inducing mechanisms are similar, the top of the slopes to the northwest of the study area requires close monitoring. Finally, a detailed potential landslide mapping and interpretation from the high-resolution digital elevation model also present to prevent further landslides. The investigation indicates that the occurrence of landslide is highly related to seepage effect of accumulated rainfall, toe erosion by surface runoff, and local unstable geological structure.

The Italian cultural heritage is one of the most noticeable in the world; an important part of it is subjected to natural hazard and risk conditions. Religious buildings, due to their location on impervious sites are particularly exposed to landslides. In this paper we study the hermitage of Cerbaiolo (Tuscany, central Italy). The hermitage, founded in the 8th century as a Benedictine monastery is now a Franciscan Women Institute seat. The buildings are on the edges of a limestone plate overlapped to a clayey formation. Falls, toppling and slides are present along the limits of the plate due to the geomechanics properties of the rock and to the contrast between the two lithological complexes. In order to identify the main joint sets affecting the rock mass a structural-geological survey was carried out and four sets are identified. The rock plate was classified according to Bieniawski, Barton and Geological Strength Index approaches. The outcomes confirm the predisposing factors to mass movements, corresponding to the intensity and characteristics of fracturing of the rock mass. With regard to the slope stability analysis, a failure mechanism involving sliding along a single plane (plane failure) was assumed on the first approximation. The analyses take into account the presence of tension cracks as an indicator factor for the instability phenomenon. The results of stability analyses, performed in static and seismic conditions, indicate a widespread instability condition. The dip slope direction, the properties and type of discontinuities and the local variation of composition influence the hazard assessment.

This study uses three periods of airborne laser scanning (ALS) digital elevation model (DEM) data to analyze the short-term erosional features of the Tsaoling landslide triggered by the 1999 Chi-Chi earthquake in Taiwan. Two methods for calculating the bedrock incision rate, the equal-interval cross section selection method and the continuous swath profiles selection method, were used in the study after nearly ten years of gully incision following the earthquake-triggered dip-slope landslide. Multi-temporal gully incision rates were obtained using the continuous swath profiles selection method, which is considered a practical and convenient approach in terrain change studies. After error estimation and comparison of the multi-period ALS DEMs, the terrain change in different periods can be directly calculated, reducing time-consuming fieldwork such as installation of erosion pins and measurement of topographic cross sections on site. The gully bedrock incision rate calculated by the three periods of ALS DEMs on the surface of the Tsaoling landslide ranged from 0.23 m/year to 3.98 m/year. The local gully incision rate in the lower part of the landslide surface was found to be remarkably faster than that of the other regions, suggesting that the fast incision of the toe area possibly contributes to the occurrence of repeated landslides in the Tsaoling area.

International audience; We present Contact Dynamics discrete element simulations of the earthquake-triggered Jiufengershan avalanche, which mobilized a 60 m thick, 1.5 km long sedimentary layer, dipping similar to 22 degrees SE toward a valley. The dynamic behavior of the avalanche is simulated under different assumptions about rock behavior, water table height, and boundary shear strength. Additionally, seismic shaking is introduced using strong motion records from nearby stations. We assume that seismic shaking generates shearing and frictional heating along the surface of rupture, which, in turn, may induce dynamic weakening and avalanche triggering; a simple "slip-weakening'' criterion was adopted to simulate shear strength drop along the rupture surface. We investigate the mechanical processes occurring during triggering and propagation of an avalanche mobilizing shallowly dipping layers. Incipient deformation forms a pop-up structure at the toe of the dip slope. As the avalanche propagates, the pop-up deforms into an overturned fold, which overrides the surface of separation along a decollement. Simultaneously, uphill layers slide at high velocity (125 km/h) and are folded and disrupted as they reach the toe of the dip slope. The avalanche foot forms a wedge that is pushed forward as deformed rocks accrete at its rear. We simulated five cross sections across the Jiufengershan avalanche, which differ in the geometry of the surface of separation. Topographic and simulated surface profiles are similar. The friction coefficient at the surface of separation determined from back analysis is abnormally low (mu(SS) = 0.2), possibly due to lubrication by liquefied soils. The granular deposits of simulated earthquake- and rain-triggered avalanches are similar.