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The road that crosses the Haibat Sultan Mountain in the northern part of Iraq; is one of the dangerous roads in this region. To perform a slope stability analysis for the dangerous parts of the road, we have used Bejerman’s Method. We have reviewed satellite images of the road and all those potential areas were checked in the field; accordingly, eleven stations were recognized. Landslide Possibility Index was determined at the studied stations following Bejerman’s field method. The road climbs the southern face (dip slope) of the mountain through very hard carbonate rocks of the Pila Spi Formation, where the bedding planes daylight in the slope face near the road cuts. This produced many large landslides. Along the northern face of the mountain, the road runs through soft clastic rocks where joint planes in the rock mass intersect and daylight in the slope face near the road cut. In order to prevent future wedge failures, a 30 m offset was created from the toe of the slope to the road. In almost all cases, the Landslide Possibility Index indicated a moderate to very high likelihood for failure along all road cuts.

A slow-moving landslide on the Huafan University campus, which is located on a dip slope in northern Taiwan, has been observed since 1990. However, reliable monitoring data are difficult to acquire after 2018 due to the lack of continuous maintenance of the field measurement equipment. In this study, the multitemporal interferometry (MTI) technique is applied with Sentinel-1 SAR images to monitor the slow-moving landslide from 2014–2019. The slow-moving areas detected by persistent scatterer (PS) pixels are consistent with the range of previous studies, which are based on in situ monitoring data and field surveys. According to the time series of the PS pixels, a long period gravity-induced deformation of the slow-moving landslide can be clearly observed. Moreover, a short period seasonal surface fluctuation of the slow-moving landslide, which has seldom been discussed before, can also be detected in this study. The seasonal surface fluctuation is in-phase with precipitation, which is inferred to be related to the geological and hydrological conditions of the study area. The MTI technique can compensate for the lack of surface displacement data, in this case, the Huafan University campus, and provide information for evaluating and monitoring slow-moving landslides for possible landslide early warning in the future.

Geological structures precondition hillslope stability as well as the processes and landslide mechanisms which develop in response to deglaciation. In areas experiencing glacier retreat and debuttressing, identifying landslide preconditions is fundamental for anticipating landslide development. Herein, the ~ 150 M m3 Mueller Rockslide in Aoraki/Mount Cook National Park, New Zealand, is described; and we document how preconditions have controlled its morphology and development in response to thinning of the adjacent Mueller Glacier. A combination of geomorphological and geotechnical mapping—based on field, geophysical and remote sensing data—was used to characterise the rock mass and morphology of the rockslide and surrounding hillslope. Mueller Rockslide is identified as a rock compound slide, undergoing dominantly translational failure on a dip slope. The crown of the rockslide is bounded by several discontinuous, stepped scarps whose orientation is controlled by joint sets; these scarps form a zone of toppling that is delivering rock debris to the main rockslide body. Surface and subsurface discontinuity mapping above the crown identified numerous joints, fractures and several scarps that may facilitate continued retrogressive enlargement of the rockslide. The presence of lateral release structures, debuttressing of the rockslide toe and steeply dipping bedding suggest that the rockslide may be capable of evolving to a rapid failure.

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.

As the scale and depth of mines increase, large deformations of high-steep slopes progressively become prominent. Compared with the ordinary cables, negative Poisson’s ratio (NPR) cables can provide a constant resistance force and high deformation inhibition during slope deformation, avoiding the occurrence of slope instability hazards. Consequently, the control effects on the toppling failures of slopes were necessary to be researched. Changshanhao open-pit gold mine was taken as an example; based on the field geological investigation and rock mechanics testing, a three-dimensional engineering geological model of open-pit mine was constructed. Subsequently, the stability of open pit in current situation and final boundary situation was estimated with FLAC3D software, for the potential slope vulnerable areas to be comprehensively identified. Finally, the control effects of ordinary cables and NPR cables on the instable W13 slope section were compared and studied through FLAC3D simulations, and the reinforcement effects of NPR cable on the anti-dip slope were proved as significant; meanwhile, the corresponding reinforcement methods in the failure mine areas were proposed, laying a reference for the instability failure control and reinforcement of similar anti-dip slopes.

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.

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.

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.

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.

The left bank of the cushion pond of Baihetan hydropower station is a slant and dip slope. The gently inclined intra-layer fault zones, the steep-dip faults and the unloading fissures cutting the slope to form several potentially unstable blocks. The computational results show that the stabilities of the blocks are controlled by inclined intra-layer fault zones. A method of treatment applying deep replacement caverns and load-reduction excavation was proposed to reinforce the unstable blocks. In order to study the reinforcement mechanism of the deep replacement caverns for the giant slope blocks controlled by inclined intra-layer fault zones, the 3D simulation analysis of the slope treatment construction was carried out by use of FLAC3D software, and a 3D geo-mechanical model was developed to carry out experimental research. The results of the calculation and experiment show that the deep concrete replacement caverns effectively control the shear and sliding deformation of the bottom slide surface and improve the stability of the blocks combined by structural surfaces. In the process of slope strength reduction and overloading, the slope deformation and cracking are gradually extended from the surface to the inner part, and shear stresses of the front deep replacement cavern are the largest of all the caverns. Therefore, it is more beneficial to control the deformation of the slope and improve the stability of the giant blocks by increasing the size of the front deep replacement cavern. The research results have important guiding significance for the reinforcement treatment of the giant blocks in the left bank of Baihetan cushion pond and similar projects.

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.

This study examined the slope area of the Huafan University campus, within the entire Ta-Lun Shan area. Situated at 550 m above sea level, the area is geographically classified as a dip slope. For sustainable development of the campus, a variety of continuous monitoring equipment has been set. This study continues to analyze the monitoring data in the previous period, but focuses on the observation and comparison of the horizontal displacement at different depths recorded by inclinometers with time. At the same time, the relationship between the groundwater variation caused by heavy typhoon rainfall and the driven deep displacement of the slope is studied. In addition, this study has also been extended to the whole Ta-Lun Shan area, the observation data of cracks inside and outside the campus are analyzed. The displacement and sliding data collected over the years by the inclinometers are used to study the potential sliding surfaces distribution of the slope, combined with the influence of the typhoon rainfall. This study also continues to obtain the relationship between groundwater level and rainfall, such as the time lag and groundwater level changes, and reviews the effectiveness of the implementation of two catchpits at the campus. In the process of renovation, a Shape Acceleration Array (SAA) is used for measuring the instantaneous displacement to monitor if the displacement has increased during the implementation of the catchpits. The SAA measurement is taken as the reference basis for hazard prevention and maintenance of the slope, thus reducing and preventing the occurrence of disasters in the area. Then, a series of shear tests are carried out. Finally, the software Geostudio is applied to analyze the relationship between rainfall infiltration, groundwater level, and the displacement of the entire slope. The numerical analysis results are compared with the monitoring results in order to comprehensively discuss the slope safety.

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.

Toppling failure of rock slopes is a complicated mode due to a combination of both continuous and discontinuous deformation, especially in dealing with anti-dip rock slopes. In this paper, a novel continuum-based discrete element method (CDEM), which is useful in modeling the entire progressive process from continuous to discontinuous deformation, is proposed to analyze the deformation characteristics, the failure mechanism and the evolution process of a large-scale open pit slope with a typical anti-dip structure. To simulate the slope deformation, the shear strength reduction method (SSR) is adopted to represent the strength degradation of rock mass in the deterioration process. The simulated results are validated using data obtained from a field investigation and continuous monitoring by employing an advanced remote sensing technique called ground-based interferometric synthetic aperture radar (GB-InSAR). To analyze the evolution trend of the anti-dip slope, the subsequent toppling failure mode is predicted using the validated CDEM models. Based on a case study of a slope at the Fushun open pit mine (in Fushun, China), the unique geological structure with various joints and discontinuities, ground-water, intense rainfall, and mining activities are identified as the main triggers for different failure stages. The comparison between the field data and the simulation shows that CDEM accurately depicts the rock deformation and the failure pattern of the studied slope. The proposed numerical modeling techniques can be used for predicting failures of other similar excavated rock slopes. The simulated evolution process and the recorded deformation patterns help engineers to gain a better understanding of rock mass movement of anti-dip slopes, and the presented methodology could be utilized for similar studies and engineering designs. (C) 2015 Elsevier B.V. All rights reserved.

Characteristic landscapes (e.g., cuesta, cliff and overhang of caprock, or stepped terrain) formed by differential erosion can be found in areas composed of variable geology exhibiting different resistances to weathering. Parallel retreat of slopes, defined as recession of slopes without changes in their topography, is sometimes observed on slopes composed of multiple strata. However, the conditions needed for such parallel retreat have not yet been sufficiently clarified. In this study, we elucidated the conditions for parallel retreat of rock slopes composed of alternating layers using a geometric method. In addition, to evaluate whether various rock slopes fulfilled the conditions for parallel retreat, we analyzed topographic data obtained from periodic measurement of rock slopes in the Aka-kuzure landslide, central Japan. Our geometric analysis of the two-dimensional slopes indicates that dip angle, slope gradient, and erosion rate are the factors that determine parallel retreat conditions. However, dip angle does not significantly affect parallel retreat conditions in the case of steep back slopes (slope gradient > 40°). In contrast, dip angle is an important factor when we consider the parallel retreat conditions in dip slopes and gentler back slopes (slope gradient

The relationship between large deep-seated landslides and geologic structures characteristic of accretionary complexes were examined in the Chichibu belt on the eastern part of the Kii Peninsula, central Japan. In the Chichibu belt, bedrock consists of Jurassic accretionary complexes composed of basalt, limestone, chert, Permian–Triassic boundary siliceous shale (PTBS), mudstone, sandstone, and melanges with sheared shale matrices. The landslides treated in this paper include prehistoric examples involving volumes greater than one million cubic meters (located in the Karako, Sono, Kasagi, and Aso areas), and the modern Kasugadani landslide that was triggered by the Typhoon Meari on 29–30 September 2004. The age of the landslide in the Sono area was estimated at 20,440 ± 70 BP and 20,820 ± 70 BP based on AMS-14C ages of wood fragments embedded in the dammed lake sediments, while ages of the other prehistoric slides are not known. All of the landslides occurred on dip slopes. The bedding, foliation, and fault planes of the rocks in the area generally trend E–W and dip to the north, although those in the Kasugadani area dip to the south as a result of local folding. The landslides selectively slid along the planes of (1) PTBS horizons that were less strong than those of underlying chert, (2) lithologic boundaries with physical contrasts, or (3) boundary faults between melange units. These geologic structures, including the north-dipping bedding/cleavage/fault planes, were formed during Jurassic subduction–accretion and later uplift processes. The movement directions estimated for the 269 landslides and unstable slopes in this region are also N–NNE, and their slip planes are subparallel to the general bedding/cleavage planes in this area. Thus, future slides are also likely to occur on north-facing slopes.

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.

Based on numerical simulation, this study investigates the triggering factors and evolution of deep-seated gravitational deformation in a dip-slope consisting of a shale-dominated sequence of sediments. Results from continuum-based (finite difference) numerical modeling demonstrate that long-term strength degradation of a rock mass is a prerequisite for the development of gravitational slope deformation, and that river incision, resulting in change of slope geometry and corresponding stress concentration and redistribution, is a major driving mechanism for the progressive evolution of deep-seated gravitational slope deformation (DSGSD). Numerical simulation considering the influence of weak planes indicates that the bedding planes control the strength of rock mass and form a structural constraint on the development of gravitational slope deformation. A satisfactory correlation between the distribution of numerically simulated plastic shear bands and weak zones in drill cores demonstrates that the weak zones within the slope are formed due to gravitational slope deformation. Furthermore, numerical simulation shows a link between geomorphological development and internal deformation of the slope, which aids in the understanding of relationships between interior deformation of the slope, the exterior geomorphology and related effect factors including river incision and strength degradation.

The paper discusses structural considerations relating to landform development on Mt. Babia Góra (1,725 m a.s.l.), the highest massif in the flysch section of the Western Carpathian Mountains. The Babia Góra massif consists of folded Palaeogene-age sediments, including resistant Magura sandstone and less resistant sub-Magura layers, with numerous tectonic faults. The area has inverse-type geomorphology. The monoclinal ridge of the massif itself consists of the resistant Magura sandstone dipping southwards. Since the Miocene, the development of the massif’s relief has involved a number of processes, including: tectonic uplifting, removal of a thick layer of rocks, exposure of sub-Magura layers over a large area, the staged development of valleys dissecting the pediments surrounding the ever higher ridge, and slope retreat due to deep landsliding. Axes of linear terrain forms, escarpments of landslide scars and of headwater areas follow two main intersecting fracture lines present within the massif. Large quantities of colluvial material are transported away from the massif along these lines. The development of the land relief has led to the elongation of slopes as local elevation differences increased. Landsliding has developed in an uphill direction, which means that the youngest relief is observed on the highest sections of steep slopes. The development of the massif’s northern slope, which has formed a high and precipitous cuesta, began to accelerate only after a nearly complete exposure of the sub-Magura layers at its foot. Following this exposure the profile of the massif’s N-S cross-section has begun to become asymmetrical. With time, the degree of general remodelling of the massif has tended to decrease. As a result, the geomorphological contrast between the northern and southern sides of the massif has become well established. The description of the probable development of the Babia Góra relief is based on the author’s fieldwork, an analysis of geological maps and aerial photos, and on literature.

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.

The western foothills geological zone of Taiwan contains sedimentary rocks such as conglomerate, sandstone, shale, and mudstone. These formations often cause severe damage to life and property during a natural disaster such as earthquake and rainstorm, especially on a dip slope. This paper presents the results of long-term ground monitoring on a high sliding potential dip slope located in the western foothills of central Taiwan. The slope has been went through substantial movements induced by rainstorms during the monsoon season or after a typhoon. By comparing the rainfall data and long-term in-situ measurement of ground displacement using total station and inclinometer, we find that the movement of this slope is highly related to regional rainfall. The slide mechanism can be attributed to the infiltration of rainfall that tends to increase the driving force of the upper sliding mass and decrease shear resistance on the interface between sandstone and shale.

The slurry spread rule in fissure is the theoretical basis of grouting technology. In order to study the rule in fissure, the model of tilt fissure grouting in condition of flowing water is derived according to Newton's law of friction resistance and force of equilibrium law. By analyzing the slurry spread rule of the influence of water flow and the tilt Angle ,we can conclude that spread radius is the largest when slurry spreads in dip slope (θ = 1800 ) and parallel flow , the spread radius is minimum when slurry spreads in escarpment slope (θ = 00 )and counter flow, escarpment slope and counter flow have bigger influence on spread radius, fissure inclination and the water flow all importantly influence the slurry spread, whose influence depends on the grouting pressure and static water pressure in fissure.

In this paper, the authors present a probabilistic back-analysis of a recent slope failure at a site on Freeway No. 3 in northern Taiwan. Post-event investigations of this failure found uncertain strength parameters and deteriorating anchor systems as the most likely causes for failure. Field measurement after the event indicated an average slip surface of inclination 15°. To account for the uncertainties in input parameters, the probabilistic back analysis approach was adopted. First, the Markov Chain Monte Carlo (MCMC) simulation was used to back-calculate the geotechnical strength parameters and the anchor force. These inverse analysis results, which agreed closely with the findings of the post-event investigations, were then used to validate the maximum likelihood (ML) method, a computationally more efficient back-analysis approach. The improved knowledge of the geotechnical strength parameters and the anchor force gained through the probabilistic inverse analysis better elucidated the slope failure mechanism, which provides a basis for a more rational selection of remedial measures.

A fundamental long-standing question regarding Mars history is whether the flat and low-lying northern plains ever hosted an ocean. The best opportunity to solve this problem is provided by stratigraphic observations of sedimentary deposits onlapping the crustal dichotomy. Here, we use high-resolution imagery and topography to analyze a branching network of inverted channel and channel lobe deposits in the Aeolis Dorsa region, just north of the dichotomy boundary. Observations of stacked, cross-cutting channel bodies and stratal geometries indicate that these landforms represent exhumed distributary channel deposits. Observations of depositional trunk feeder channel bodies, a lack of evidence for past topographic confinement, channel avulsions at similar elevations, and the presence of a strong break in dip slope between topset and foreset beds suggest that this distributary system was most likely a delta, rather than an alluvial fan or submarine fan. Sediment transport calculations using both measured and derived channel geometries indicate a minimum delta deposition time on the order of 400 years. The location of this delta within a thick and widespread clastic wedge abutting the crustal dichotomy boundary, unconfined by any observable craters, suggests a standing body of water potentially 105 km2 in extent or greater and is spatially consistent with hypotheses for a northern ocean.

The Zenzano Fault scarp has been developed on the top of a 475 m-high erosional escarpment underlain by an upper brittle sequence and a lower halite-bearing evaporitic formation. The 1850 m-long fault, with a maximum displacement of 45 m and parallel to the escarpment, has offset the back of a dip slope, generating an antislope scarp with prominent triangular facets up to 38 m high and obstructing consequent transverse drainages (defeated streams). Both gravitational and tectonic interpretations were previously proposed for this active surface rupture. The fault scarp has been investigated by detailed geological and geomorphological mapping, geophysical surveys (GPR and ERT) and two trenches excavated across the fault in disrupted drainages. The geophysical profiles clearly imaged the fault, helping to site the trenches and roughly estimate the thickness of the deposits accumulated in the downthrown block. Although the maximum displacement to length ratio (Dmax/L) of the fault fall within the range of tectonic faults of similar length, according to the world database, the geological and geomorphological context, together with several parameters reveal that this structure corresponds to a gravitational failure: (1) anomalously high vertical displacement per event (> 1.4 m); (2) high apparent vertical slip rate (~ 0.6 mm/year); and (3) short recurrence interval of faulting events. The negligible horizontal displacement component on the dip-slip fault, as well as the presence of very large caprock collapse sinkholes and saline springs, strongly suggest that interstratal karstification of the halite-bearing evaporites has played a primary role in the development of the gravitational failure. The formation of this morphostructure has been favoured by pre-existing tectonic faults, erosional unloading related to the removal of an overburden ca. 800 m thick, and enhanced groundwater recharge due to the blockage of the drainage. This work illustrates that the proposed multidisciplinary approach allows the identification of features and calculation of parameters that may help to elucidate whether an active failure has a gravitational or a tectonic origin.

A catastrophic dip slope failure incident took place at 14:33 of April 25, 2010, at Da-Pu section of National Freeway No. 3 in northern Taiwan. It resulted in a nearly 200,000 m3 debris mass on the freeway and caused five deaths. In an effort to identify root causes of such a disastrous failure, a forensic investigation committee was formed to conduct a comprehensive failure analysis. Progress of completed forensic investigation is reported in this paper. Purpose of this paper is hoped to introduce the applications of forensic investigation technologies in similar forensic investigations, as well as appropriate means of adapting numerical modeling in a forensic investigation.

Japan Islands fundamentally consisted of the accretionary wedges. The stratum of accretionary wedges inclined, and it made dip slope and opposite slope. Granite magma intruded among accretionary wedges, and later granite itself became decomposed soil. Much annual precipitation of nearly 2000 mm, caused by monsoons, attacks forest roads, so innovative technologies for road construction are required. From ancient days, numerous circular slips and deepseated landslides occurred. For the inclined stratum at Shimanto belt composed of sedimentary rocks, deep excavation for preparing structural road foundation was invented. After deep excavation until the depth that ensured the road width, about 30 cm thick blocks of compacted subsoil were piled up. It is difficult to make high cutting slope on smooth soil area, and the retaining wall with log structure is effective both for cutting and fill slopes at spur roads. Underground water that comes out through crushing zones is often troublesome. When crashing zone and dip slope overlap, the valley head is unstable causing landslide. This makes this area inadequate for road construction. Some forest road retaining technologies have been introduced recently in Japan. When crossing the crushing zone by simple structures, cage or L-shaped steel retaining wall is effective because the weight of stones and rocks in the structure presses down the road foundation with high water permeability. It is important to adopt the most appropriate road construction method in accordance with the soil, geology and terrain conditions to provide sustainable forestry.

This paper presents a numerical procedure to explore how hydraulic conductivity anisotropy and strength anisotropy affect the stability of stratified, poorly cemented rock slopes. The results provide information about the anisotropic characteristics of the medium, including the orientation of bedding planes, the anisotropic ratios of the hydraulic conductivity and the geological significance of the hydraulic conductivity anisotropy on the pore water pressure (PWP) estimation of finite slopes. Neglecting the hydraulic conductivity anisotropy of a slope with horizontal layers leads to a 40% overestimation of the safety factor. For a dip slope with inclined layers with θ = 30°, including the strength anisotropy caused a 25% reduction of the safety factor compared to the cases which isotropic strength is assumed. This paper highlights the importance of the hydraulic-conductivity anisotropy and the strength anisotropy on the stability of stratified, poorly cemented rock slopes.

Uncertainty is inherent in geotechnical design. In regard to estimating the stability state of dip slopes, most of the uncertainty lies in the geologic model assumed and the geotechnical parameters used in the evaluation. Biplanar (or active-passive) sliding in dip slopes occurs along a slope-parallel sliding surface with toe breakout occurring at the base of the failure. Internal shearing is required to facilitate kinematic release. All three of these release surfaces work together for the slope to fail, but with different degrees of importance depending on the dip-slope inclination. Increased efficiency and value with respect to the site investigation resources can be gained by working toward minimizing the uncertainty of those parameters that have the greatest bearing on the outcome of the slope stability analysis. This can be done quickly and inexpensively by performing scoping calculations facilitated by the use of Spearman rank correlation coefficients. This paper demonstrates that for shallow-dipping dip slopes, stability is primarily dictated by the shear strength of the slope-parallel sliding surface, and therefore, efforts should be focused on constraining the shear strength of this surface. For steep dip slopes, the shear strength related to the toe breakout and internal shear release surfaces becomes dominant, and therefore, the rock-mass shear strength and that for any adversely dipping persistent discontinuities should be the focus of the geotechnical investigation. DOI: 10.1061/(ASCE)GT.1943-5606.0000515. © 2012 American Society of Civil Engineers. CE Database subject headings: Slope stability; Uncertainty principles; Rocks; Rock masses; Site investigation. Author keywords: Dip slope; Uncertainty; Rock engineering; Reliability; Rock-mass rating; Geological strength index.

Among the extensive failed slopes in the 2004 Niigata-ken Chuetsu Earthquake, Japan, a dip slope at Yokowatashi, Ojiya, was investigated intensively. The sliding plane was along a weak thin tuff sandy layer which had been deeply weathered. Triaxial compression tests and plane strain compression tests were performed on undisturbed specimens obtained by block sampling and boring sampling to evaluate the strength that was mobilized on the sliding plane. Stability analysis based on the test results reveals that, at normal time, without earthquake and without an extremely high groundwater level, the slope is stable. Furthermore, the calculation of earthquake-induced displacement provides a reasonable simulation of the failure of this slope.