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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.

We explore the controls of the litho-tectonic architecture on the erosional flux in the 370-km2 Glogn basin (European Alps). In this basin, the bedding and schistosity of the bedrock dip parallel to the topographic slope on the NW valley flank, leading to a non-dip slope situation on the opposite SE valley side. While the dip slope condition has promoted the occurrence of landslides (e.g. the c. 30-km2 deep-seated Lumnezia landslide), the opposite non-dip slope side of the valley hosts >100-m-deeply incised tributary streams. 10Be concentrations of stream sediments yield catchment-averaged denudation rates that vary between 0.27 ± 0.03 and 2.19 ± 0.37 mm a−1, while the spatially averaged denudation rate of the entire basin is 1.99 ± 0.34 mm a−1. Our 10Be-based approach reveals that the Lumnezia landslide front contributes c. 30–65% of the entire sediment budget, although it covers

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.

Piramagroon-Kani Khan (PK) valley runs parallel to Pira Magrun and Surdash anticlines almost in NW- SE trend and merges with the Lesser Zab River 9 kms southeast of Dokan town. The valley runs within the soft rocks of Shiranish, Tanjero and Kolosh formations. The valley bottom is gently sloping plain which divided longitudinally by Charmaga stream into two asymmetrical parts (northeast and southwest parts). The northeast part is wider than the other one mostly covered by Recent and Pleistocene coarse alluvium with a thickness of 1-20meters. The southwestern part is relatively narrow and mainly covered by slide debris and dislocated blocks of Sinjar Formation. Northern eastern side is formed by differential erosion and its slope is the dip slope since it nearly coincides with the dip of the strata of the Kometan and Qamchuqa Formations. The southwestern side is scarp slope which has lesser elevation and formed mainly by sliding processes and manly covered by slide debris. The surface of this part has hilly and hummocky topography. The alluviums are belonging to debris flow and river bed deposits. According to age of deposition, the alluvium is grouped in two types which are Holocene (Recent) and Pleistocene types. The first type has mainly caliber of gravels and sand which deposited on the valley bottom plains and suitable for cultivating. The second type has coarser grain sizes which consist of a mixture of blocks, boulder and graves. This type exists either on the hills or it form as isolated plateaus that about 30 high from the surrounding. Now, only as a small or large pachy remnant on the top of ridges and hills or exist as small plateaus which are transformed these elevated lands due to inversion of topography by erosion and weathering.

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.

“Triangle zone” geometry is well established in thrust tectonics, where the leading edge of a frontal thrust branches backward onto a hinterland-directed roof thrust, and the triangle zone thus formed defines the thrust system’s leading edge. Similar geometries occur in extension and inversion settings, where a triangle zone can form between a deep-seated master fault and a roof fault or backthrust located in a hanging-wall detachment. In basement-controlled extension, triangle zone development can occur when the shear strength of the master fault plane in the zone above a hanging-wall detachment cutoff exceeds that of a new or reactivated antithetic fault detaching on the hanging-wall dip slope. This structural style is characterized by pronounced hanging-wall synclines linked to detached extensional faults higher up the hanging-wall dip slopes. The same principles apply during early phases of inversion tectonics. The part of the master fault that is above the hanging-wall detachment cutoff may constitute a buttress that causes displacement to backthrust along any available detachment into accommodation structures such as emergent ramps. This structural style is characterized by compressional structures within the graben while there is minor or even no sign of inversion on the graben margin faults. These geometries could be accounted for by other processes, for example, localized deep-seated fault-controlled structures within graben, or salt redistribution. However, fieldwork and analog models demonstrate the admissibility of triangle zone kinematics across a range of tectonic settings in the presence of detachment layers that are thin relative to the overall stratigraphy — typically tens to hundreds of meters in thickness. These models can guide seismic interpretation of unusual fold structures in extensional and inverted graben. Seismic interpretation examples were evaluated from the North Sea and Saudi Arabia.

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.

A 12 million of m3 translational rockslide developed on a dip slope underlain by limestone with interlayered marls, and responsible for the destruction of the Montclus village in the fourteenth century, has been investigated by means of geomorphological and geophysical surveys. The combination of historical-geoarcheological, geomorphological, seismic refraction and electrical resistivity imaging datasets allowed the (1) reconstruction of the late Quaternary episodic evolution of the landslide, (2) characterization of the geometry and internal structure of the slid mass and (3) identification of preferential groundwater flow paths that favoured slope instability. The development of the landslide involved at least two different displacement episodes controlled by sliding surfaces at successively deeper stratigraphic positions. The first landsliding event, recorded by highly weathered landslide deposits situated above a perched failure plane, occurred approximately during the global Last Glacial Maximum (23–19 ka BP). The most recent event, which destroyed the Montclus village built on already slid rocks, is placed in the fourteenth century. Most probably, this reactivation event was triggered by the 1373 Ribagorza earthquake, with an estimated moment magnitude of M w 6.2. This work illustrates the benefits of combining geomorphological data with complementary geophysical technics in landslide investigation.

The Seymareh rock avalanche, first described by J. V. Harrison and N. L. Falcon in the 1930s, is the largest known subaerial non-volcanic landslide on Earth. The volume of its debris (44 Gm 3 ) is approximately equal to that of the largest known subaerial landslide of any kind, the 100 ka collapse of Mount Shasta volcano (45 Gm 3 ) and approaches those of gigantic landslides on Mars. Using satellite imagery, SRTM-3 data, and detailed field investigations, we gain a new understanding of the gigantic rock avalanche. The initial failure (38 Gm 3 ), involving a dip slope consisting of a relatively weak interbedded limestone–mudrock sequence capped by resistant Asmari Limestone, had an average thickness of 410 m along a 15.5 km width of the Kabir Kuh anticline. The rockslide transformed into a rock avalanche that travelled 19.0 km with a fahrboschung (the angle between the highest point of the pre-landslide source area topography and the distal limit of the debris) of only 3.6°. Initial failure involved complex planar sliding dictated by four structural elements: (1) bedding-parallel shears and (2) across-bedding break-throughs combined to produce a low-angle (11°) overall sliding surface that (3) broke out through the Asmari carapace at the toe of the failed slope while (4) tectonically weakened bedding-normal joints provided lateral release surfaces. Nine discrete bedding-parallel basal sliding surfaces divided the detached mass into nine stacked plates. The upper plate (23 Gm 3 ) included 20.7 Gm 3 of Asmari Limestone. Analysis of accelerator mass spectrometry radiocarbon dates from this study and by others indicates that the rock avalanche occurred between c . 8710 and 9800 14 C years BP. Supplementary material: A summary of the tectonics, stratigraphy and physiography of the Zagros Fold–Thrust belt together with a description of surficial gravity collapse structures in the region (Harrison & Falcon 1934, 1936) is available at www.geolsoc.org.uk/SUP18612.

Facies architecture and platform evolution of an early Frasnian reef complex in the northern Canning Basin of north-western Australia were strongly controlled by syn-depositional faulting during a phase of basin extension. The margin-attached Hull platform developed on a fault block of Precambrian basement with accommodation largely generated by movement along the Mount Elma Fault Zone. Recognition of major subaerial exposure and flooding surfaces in the Hull platform (from outcrop and drillcore) has enabled comparison of facies associations within a temporal framework and led to identification of three stages of platform evolution. Stage 1 records initial ramp development on the hangingwall dip slope with predominantly deep subtidal conditions that prevented any cyclic facies arrangements. This stage is characterised by basal siliciclastic deposits and a major deepening-upward facies pattern that is capped by a sequence boundary towards the footwall (north-west) and a major flooding surface towards the hangingwall. Stage 2 reflects the bulk of platform aggradation, significant platform growth towards the hangingwall and the development of reef margins and cyclic facies arrangements. Thickening of this stage towards the hangingwall indicates that accommodation was generated by rotation of the fault block and overlying platform. Stage 3 records a major flooding and backstep of the platform margin. The Hull platform illustrates important elements of margin-attached carbonate platforms in a half-graben setting, including: (i) prominent, but limited, coarse siliciclastic input that does not have a major detrimental effect on carbonate production near the rift margin in arid to semi-arid settings; (ii) wedge-shaped accommodation created by syn-depositional rotation of fault blocks and tilting of the hangingwall dip slope, resulting in shallow-water facies and subaerial exposure up-dip of the rotational axis and deeper water facies down-dip; and (iii) evolution of a ramp to rimmed shelf, coincident with a sequence boundary–flooding surface, that is accelerated by tilting of the hangingwall dip slope during fault-block rotation.

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.

Freeway No. 3 and Highway T-62 were cut through the same dip slope formation in northern Taiwan in the late 1990s. The former used an extensive tie-back system to hold back the cut slope; the latter adopted very limited slope stabilisation measures. On 25 April 2010, a catastrophic dip slope failure suddenly occurred at the cut slope of Freeway No. 3. Ironically, the cut slope of Highway T-62 remained stable. As found from the investigation, slope cutting and excavation of a bridge launching pit near the slope toe caused complete daylighting of the sliding plane of the freeway slope, whereas the sliding plane of the highway slope was not exposed by slope cutting. Owing to the poor corrosion protection of tie-back anchors installed in the freeway slope, a majority of tie-back anchors were seriously corroded and caused significant loss of tie-back load capacity. Although some sign of slope sliding was observed during the construction of the freeway slope, no proper measure was taken to effectively stop the dip slope from further sliding. The monitoring devices installed on the freeway slope also failed to identify the subsequent slope movement. Therefore, when the slope failed, the event came as a complete surprise to everyone.

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 study examined differences in landslide sediment production and sediment transportation abilities of reservoir watersheds in different geological environments after extreme rainfall. The watershed in this study covered an area of 109 km2; the upstream river banks of the reservoir contained interbedded shale and faulted shale and had a sandstone dip slope. This paper uses a LiDAR-derived DTM taken in 2005 and 2010 to investigate the landslide sediment production and riverbed erosion and deposition in the watershed. This study also applied the conservation of mass concept to analyze the sediment outflux in the subwatersheds. The research results indicated that although the right bank, which had interbedded shale and a sandstone dip slope, had a substantially greater number of landslides, the sediment production of it was less than that of the left bank, which had numerous deep-seated landslides caused by fault zones. However, affected by the higher sediment production of the left bank and under the same stream power, the left bank subwatersheds also had higher sediment outflux.

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.

A catastrophic dip slope failure occurred suddenly at an anchored cut slope of Freeway No. 3 in 2010 after 13 years in service. Among the factors contributing to this landslide, serious corrosion on tieback anchors was the most obvious factor in addition to the groundwater hydrology inside the slope. In the past, most of the ground anchors in Taiwan were constructed with limited or no corrosion protection. So, it is likely that the tieback anchors on slopes are suffering similar corrosion problem under the humid weather condition. So, the Ministry of Transportation and Communication (MOTC) of Taiwan government launched an extensive island-wide investigation program to check the status quo of existing anchored slopes along the highways, railways, and public roads. Not surprisingly, corrosion is found to be a common problem for the existing ground anchors. A national overhaul program for the anchored slopes along the highways and railways has been launched. This paper covers the findings from the anchored slopes inspection and the measures taken to improve the corrosion protection of the existing anchors. In addition, some minor modification on anchor tendon assembly and cement grouting process has been suggested to upgrade the corrosion protection of the new anchors.

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.

The late Wisconsin (c. 18,000 ybp) Saginaw–Huron Ice Stream (SHIS) of the Laurentide Ice Sheet was as much as 800 km long and 250 km wide in the Great Lakes basin of mid-continent North America. In its onset zone in the upper Lake Huron basin of Ontario, Canada it flowed south from the high standing Canadian Shield to move over gently dipping Ordovician and Silurian dolostones devoid of glacial sediment cover. The onset zone is recorded by a distinct ‘hard bed landform assemblage’ across ∼3000 km2 of north-facing escarpments (Niagara, Fossil Hill, and Kagawong) and dip slope pavements on the Bruce Peninsula and Manitoulin Island, and the adjacent floor of Lake Huron. A wide range of glacially-streamlined rock landforms were carved into dolostones below fast flowing ice. The largest are 30 km-wide bullet-shaped escarpment ‘promontories’ that face upglacier. Superposed on these are swarms of rock drumlins up to 5 km wide with downglacier lengths of as much as 10 km. Promontories and drumlins record streaming of dirty basal ice around escarpment highs and create a distinct ‘zig-zag’ planform to the escarpments. In turn, down-dip, trailing-edge dolostone pavements are corrugated by kilometre-long megagrooves and megaflutes cut by basal ice flowing around resistant high-standing bioherm mounds on dolostone bedding planes. The geomorphology of the Niagara Escarpment does not primarily reflect a lengthy history of preglacial Cenozoic fluvial erosion as classically argued, but geologically-brief episodes of accelerated abrasion and quarrying below ice streams within successive Pleistocene ice sheets.

It is a dip slope with mudstone and sandstone interbedded at the northward 363K National Highway NO.3. in Taiwan. The Figure 1 showed the slope sliding due to continuous heavy rain on August 19, 2010. This study analyses the slope stability by the finite element method of program PLAXIS-2D, and explores the suitability of various control engineering methods. It is named analysis before design with anchors in this study before September 2010. The aim is to search the original parameters of the ground by comparing a potential sliding surface with monitor data of site. Then countermeasure analyzes the impact based on the loss of anchor prestress and the row of piles set. From the results of analysis, sliding surface analysis and the data which was derived from the early monitor judgments are consistent. The ground anchor has been unable to achieve good stable slope effect for the slope sliding, due to heavy rains. However, the rows of pile construction significantly improved the stability of the slope.

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.

An extensive number of slopes failed in the 2004 Niigata-ken Chuetsu Earthquake. Among them, a dip slope containing a weak layer in Yamakoshi Village (currently Nagaoka City) was investigated intensively. Regarding its morphological characteristics, it is argued that the earthquake reactivated a pre-existing failure plane which then formed most of the present sliding plane. In order to reveal the strength properties of the weak layer that formed the sliding plane, including the behavior against cyclic loading, a series of triaxial compression tests and simple shear tests was performed on undisturbed specimens that were retrieved by block sampling from the site. Based on the test results, a stability analysis and the calculation of the earthquake-induced displacement were performed. By extending Newmark's sliding block analysis, while considering the effects of the irregular geometry of the sliding plane and its strain-softening properties, a reasonable simulation of the process of this slope failure could be provided.

In a case history of dip slope failure caused by the 2004 Niigata-ken Chuetsu Earthquake, it has been reported that the slope contained a thin sandy soil layer. The layer may have liquefied if it had been saturated at the time of the earthquake. Undrained cyclic triaxial tests comprise one of the available experimental approaches for evaluating the liquefaction behavior of such thin sandy soil layers. In this study, a series of undrained cyclic triaxial tests was performed on specimens containing an artificial sand layer in order to investigate the effects of system compliance that are possibly induced by partial drainage caused by the changes in volume of the filter paper used to saturate the sand layer and the local drainage at the interface among the specimen, the top cap and pedestal, and the rubber membrane. The observed liquefaction behavior depended on the thickness of the sand layer under otherwise similar conditions, suggesting the significant effect of system compliance. By conducting special tests, while correcting the partial drainage, it was possible to reduce its effect on the liquefaction behavior. Cylindrical specimens with a top cap and pedestal, all having the same diameter, exhibited a smaller effect from partial drainage than prismatic specimens with an oversized top cap and pedestal.

Typhoon Morakot induced the catastrophic and deadly Shiaolin landslide in southern Taiwan on 9 August 2009, resulting in more than 400 casualties. We undertook a geological and geomorphological investigation with the aim of reconstructing the events leading up to this landslide and to clarify factors that contributed to its development. Cumulative rainfall reached up to 1676.5 mm in about three days under the influence of the typhoon, and the Shiaolin landslide, with a volume of 25 × 106 m3, occurred one day after the peak in rainfall intensity. The landslide occurred on a dip slope overlying late Miocene to early Pliocene sedimentary rocks consisting of silty shale, massive mudstone, and sandstone. It started as a rockslide in the upper third of the landslide area and transformed into a rock avalanche that crossed a series of terraces and displaced or buried the village below. It buried the riverbed of the Chishan River and ran up the opposite slope, creating a landslide dam 60 m high, which was breached about 1 h and 24 min later, flooding the village. The velocity of the landslide is estimated to have been 20.4 to 33.7 m s− 1 and its apparent friction angle was 14°, which indicates its high mobility. The detachments in the source area consist of combinations of bedding planes and joints or faults. The landslide was preceded by gravitational deformation, which appeared as hummocky landforms before the landslide and as buckle folds exposed after the event. The landslide deposits consist of fragments of mudstone, shale, and sandstone, as well as clayey material at its base. This clayey material, consisting of illite, chlorite, quartz, feldspar, and calcite, is assumed to have strongly influenced the long, rapid runout.

The Shanshucao landslide is a recent landslide that occurred in the China Three Gorges Reservoir area. It is next to the Daling Hydropower Station landslide, one of the geological hazard professional monitoring points in the China Three Gorges Reservoir. The Shanshucao landslide had not shown a significant deformation during recent decades until September 2nd, 2014. On that day, the Shanshucao landslide abruptly started to move at around 9 a.m. local time, stopped at 13:19 p.m., and caused a 43.2 × 104m3 landslide mass which slipped into the Luogudong River, the secondary branch of Yangtze River. Fortunately, the local government gave an efficient early warning and organized a successful emergency evacuation. Nobody was injured or killed in this landslide failure event. The Daling Hydropower Station and its attached buildings were eradicated by the landslide. Posterior to the failure, a newborn free surface occurred on the dip slope. The remaining body of the landslide poses a great threat to the safety of both the village and the Three Gorges Reservoir operation. Subsequently, an emergency monitoring system has been placed on the slope to observe any subsequent deformation. By applying the kinematic model, this article will give a general outlook on the failure event and investigate the geological features which caused the slope instability. Also, the two inclined blocks models are introduced in the back analysis and show a good comparison to the site observation results. This article will provide guidance and suggestion for the stability analysis of similar highly weathered bedded landslides in the China Three Gorges Reservoir area.

A major gap in the stratigraphic record of underlying rocks of a cuesta landform in southern Franconia causes local absence of resistant cap rock. As a consequence the scarp is atypical, capped by less resistant, mainly pelitic rock. Its dip slope is identified as a planation surface, as it disconformably cuts underlying rock structures. These findings indicate that cuesta landscapes may contain prominent sculptural elements. The formation of the planation surface started during or after the Oligocene at least in the southern part of the study area, but may have started earlier farther north. Evidence of processes acting on this surface is derived from coarse, partially ventifacted gravel, which allow reconstructing two individual river courses. These presumably formed under dry climate. The surface was dissected some 10 Ma after its onset, in Late Miocene times, by deeply cut valleys fostering lacustrine deposits.

The damage caused by an earthquake-induced landslide can generally be classified as either a limited deformation or a catastrophic failure. From an engineering point of view, the latter can be much more dangerous because the sliding mass may continue moving until it collides with another object. If a catastrophic failure occurs near a river, the debris may block the river, causing serious damage to the adjacent area. Therefore, examination of the mechanism of such catastrophic slope failures is important with respect to the mitigation of earthquake disasters in mountainous districts, although numerical modeling of such phenomena is rather difficult. In the present study, a new numerical model is developed to simulate an earthquake-induced catastrophic landslide that occured at a typical dip slope, namely, the Yokowatashi Landslide in Japan. In this case, the upper part of the bedrock on the planer tectonic dip surface slid more than 70 m. Only shear-strength degradation at the bedding plane could cause such a long-distance traveling failure. To investigate the strain-softening characteristics of the materials that filled the bedding plane, a series of laboratory tests involving undisturbed block samples was performed. The measured stress-displacement relationships under cyclic loading were numerically modeled as a newly proposed elasto-plastic constitutive model to be used in numerical simulations of landslide, based on the dynamic finite element method. The observed phenomena were appropriately simulated by the proposed method. The mechanism of catastrophic failure is discussed in detail in this paper in order to clarify the relationships between the strain-softening characteristics and the global slope stability. Our newly proposed method to evaluate the possibility of a catastrophic failure was applied to the landslide, and the moment when the slope becomes unstable was able to be predicted. The results confirm that the proposed method can predict the catastrophic failure of a slope.

On the basis of the status quo of Jinyang Grand Buddha in Taiyuan, some factors such as topography, geological structures, climate, hydrology, and engineering geology that influence the stability of the Buddha slope are considered, and several working situations of the slope that possibly suffered are presented in this article. The Buddha slope stands upright and the rock masses are composed of thick Permian sandstone, which dips slightly inward to the slope. Affected by both the incision of regional joints and the load relief to the free surface, the rock mass of the Buddha slope has turned into loosened blocks. Numerical stability analysis by FLAC-2D on the basis of the strength reduction method reveals that the localized deformation of the rock masses near the vertical surface of the slope may trigger reversing of rock beddings making the back dip slope convert into a dip slope with the possibility of plane sliding failure. Furthermore, the pseudostatic method for the dynamic process and limit equilibrium method for the static process are applied to different working situations of the Buddha slope. The analytical results illustrate that plane sliding failure will not occur when the slope is affected only by seism. However, water filling in the cracks of the loosened rock mass may greatly contribute to the potential plane sliding failure. When horizontal seism-force and hydrostatic pressure are coupled, the Buddha slope can hardly keep stable. Additionally, the loosened rock masses are prone to block toppling failure when influenced by the seism force.

The 12 March 2001 landslide at a slate quarry in Okayama, Japan killed three workers. Composite studies based on field surveys of the landslide slope, interviews with local residents and quarry workers, and inspections of hydrological and seismological data have been used to clarify the causes of this slide and its movements. The results indicate that the landslide was enabled firstly by the steepness of the slope, which had been undercut by river; secondly, the structure was that of a dip-slope that was prone to deep-seated slides along bedding planes; thirdly, numerous joints and faults were present. Surprisingly, rainfall, earthquakes, and explosions do not appear to have played any role in the triggering of this slide. The interviews demonstrated that the frequency of precursory failures increased over a period of several hours before the 12 March 2001 landslide. Inspection of the seismograph records and the eyewitness evidence both indicate that the main part of the landslide consisted of two phases of slope failure within 23 s. After the slide, the frequency of the failures gradually decreased with time over a period of several days. Three new terms are proposed for landslides: foreslide, mainslide, and afterslide, following the terms foreshock, main shock, and aftershock used in seismology.

2004年の新潟県中越地震では中山間地における多数の斜面崩壊が発生した。二次元動的弾塑性有限要素法によりある流れ盤斜面の崩壊を再現した事例を報告する。このような大規模崩壊を再現するために, 不撹乱ブロック試料による繰返し直接せん断試験に基づいて, 層理面に介在する薄い砂層の繰返し載荷時のひずみ軟化特性が検討された。その結果, 観測された現象が精度良く再現され, 長距離移動型の崩壊が層理面のひずみ軟化挙動により誘引されることが示唆された。

Numerous natural or artificially embanked slope failures were caused by the 2004 Niigata-ken Chuetsu Earthquake. Characteristics of large scale natural slope failures that occurred at folding hills, river terraces, etc, were classified from a geometric structural view point. It was noted that surface failures occurred at steep cliffs and landslides occurred at gently slanting dip slopes. The cause of a landslide in a dip slope at Yokowatashi, Ojiya city was analytically investigated based on cyclic shear test results of the laminar sand at the bedding plane. This study revealed that the safety factor of the slope stability became momentarily smaller than 1.0 several times during the earthquake due to the small undrained shear strength of the tuff sand seam and the landslide behavior was simulated by an elasto-plastic dynamic finite element analysis where the strength decrease of the sand seam with increasing number of cycles was taken into consideration. The cause of destructive damage of a school building at Nagaoka National College of Technology (NNCT) was next examined by another elasto-plastic dynamic FEM. From the analysis results, it was confirmed that the building was pulled and twisted by the landslide of the bank shotcrete accompanied with pile fracture.

An array of meander scroll sets (point bar complexes) is exposed over a land surface eroded across the dip slope of sandstones of the Nubia Group, Taref Formation (Turonian) around the southern fringe of Dakhla Oasis, Egypt (25.5°N, 29°E). These sandstones are thus interpreted as fluvially deposited. Using published equations, bankfull channel width, depth, as well as sinuosity are estimated from radii of meander curvature. With a reasonable assumption of velocity, bankfull discharge is then estimated. This is found to be comparable with bankfull discharge values estimated from published plots of hydraulic geometry (width and depth) against discharge. Both approaches result in mean bankfull discharge estimates of 4.4–7.0×103 m3s−1. Using mean radius of meander curvature, sinuosity is estimated at 1.66. In this hyperarid climatic region aeolian erosion has carved yardangs into the Taref sandstone, the flanks of which expose uniform, tabular cross-beds of coarse, clean quartz sand. From the palaeofluvial estimates, from other features of the exhumed meander scrolls, and from the character of the sandstone, channels in which the Taref sands were deposited are inferred to have been wide and shallow, of low sinuosity, rapidly migrating laterally, with minimal overbank deposition of muds, and rapid vertical accretion. Published indications of a tropical monsoon climate over Egypt in the Turonian are harmonized with the absence of fossil flora from the Taref with reference to indications of a rapidly changing fluvial landscape.

Special features were correlated to the geological causes of the Chiu-fen-erh-shan landslide, a gigantic rockslide on a dip slope, induced by the Chi-chi earthquake (ML=7.3) in central Taiwan in 1999. An aerial photo interpretation and the succeeding geological mapping of the failure were employed in this study. A linear depression, a steep step, and a low drainage density in the landslide area were detected from the aerial photos taken in 1998. The gravitational creep was believed to result in the features of the linear depression and the low drainage density. The steep step represented a buckling feature found in the field. The landslide area is composed of stratified sandstone and shale, with dip angles ranging 20–36°. The slip surface developed along a pre-existing bedding fault that resulted from flexural slip folding. Before the Chi-chi earthquake, the rock on the upslope side buckled and was retained by a thick-bedded sandstone downslope. The earthquake shock seriously damaged the sandstone support and led to the catastrophic landslide. This type of landslide is likely to occur on the moderately dipping slope of stratified rocks that were previously deformed by flexural slip folding.

A disastrous earthquake rocked Taiwan on September 21, 1999, with magnitude M L =7.3 and an epicenter near the small town of Chi-Chi in central Taiwan. The Chi-Chi earthquake triggered landslide on the dip slope at the Chiufengershan. In this study, a review of the topography and geology of this area was followed by field investigations. Laboratory testing was applied to understand the geomaterial composing the slope. Then, based on a series of limit equilibrium analyses, the failure mechanism of this landslide and the risk of the residual slope were studied. According to the stability analyses, the pre-quake slope is quite stable, with factor of safety of 1.77 (dry) to 1.35 (full groundwater level); explaining why there is no written record of a landslide here for the past 100 years. In contrast, a back analysis shows that the Chi-Chi earthquake-induced dynamic loading is far more than the dip slope can sustain, due in part to the short distance to the epicenter. A Monte Carlo type probability analysis suggests that the residual slope is more dangerous than the pre-quake slope and needs more attention.

The Tsaoling landslide, one of the largest landslide areas in Taiwan, has been affected by catastrophic events triggered by rain or earthquakes six times since 1862. These landslides, including that caused by the 1999 earthquake, have essentially not been reactivated old slides, but were sequential new ones that developed upslope, retrogressively. The landslide area is underlain by Pliocene sandstone and shale to form a dip slope with a bedding plane, dipping uniformly at 14°. The slip surface of the 1999 landslide was smooth and planar, parallel to the bedding plane with a slightly stepped profile; it formed within thinly alternated beds of fine sandstone and shale with ripple lamination or in a shale bed. The shale is weathered by slaking and probably by sulfuric acid, which is inferred to be one of the major causes of the intermittent retrogressive development of the landslides. The weathering was likely accelerated by the removal of overlying beds during earlier landslides in 1941 and 1942. The top margin of the 1999 landslide, in plan view, coincided with a V-shaped scarplet, which can be clearly recognized on aerial photographs taken before the landslide. This geomorphological feature indicates that this landslide had already moved slightly before its 1999 occurrence, providing precursory evidences.

It is found by engineering geological exploration that No.5 slope in Wutai-Yuxian expressway is typical dip slope forming in ancient gneiss terrain. We conclude that slope deformation and failure mainly result from the gneiss and mica schist constituting the slope and the heavy precipitation in construction period. Besides, the insufficiency of geological exploration in revealing the complex geology and the deficiency of designation and constructing in preventing and controlling geohazards are the engineering factors causing landslide in No.5 slope. Slope cutting and reinforcement, draining and cutting off the surface water, and enhancing the displacement monitoring for potential sliding surface may serve as a reference for construction and supporting designation of deep cutting slope in this area as well as for constructing slope engineering in the areas sharing similar geology with this area.

Owing to tectonic collision, about 70% of Taiwan’s land are mountains and foothills. With several unfavourable conditions such as typhoons, strong rainfalls, and earthquakes, the landslide hazard is a critical issue in Taiwan. This issue is increasingly important because the use of hillsides for residence are growing in recent years. To address the issue and to protect its citizens, Taipei City Government initiated a pilot project to monitor landslide displacements in 2010. The project involves a selected hillside community with dip slope in Taipei City. The community had a major landslide in 1983.The monthly monitoring with non-automated devices is not helpful for residence to react to landslides. To help improve the situation, we use motion sensors to develop fully automated devices to infer displacements. We also used numerical analyses to help determine the best locations to install these devices. They were mounted to the ground surface to sense the tilt. The tilt converts to displacements by assuming slip surfaces. Small displacements were detected during a typhoon event in July of 2013.With the developed monitoring device, standard operation procedures were developed accordingly. Community residents has been educated how to react to unfavourable conditions. These conditions are defined by displacements exceeding certain thresholds.

Tsaoling is an important area for landslide studies in Taiwan because of its repetitive occurrences of landslides. In 1999, the Chi-Chi earthquake triggered a dip slope failure and the landslide mass deposit in the channel and opposite bank of the Chinshui River. Long-term (3 decades) as well as the rapid landscape evolution after the Chi-Chi earthquake is inspected in the present study, by using a total number of ten high-resolution digital terrain models (DTMs). These DTMs were constructed by using aerial orthophotos dated between 1979 and 2009 and they were calibrated against the 2009 DTM, with the root mean square error controlled to be less than 1 m. The focus is on the surface elevation changes of two representative cross-sections and recession of the Chunqui Cliff in the landslide scarp zone. Because the Chinshui River cuts through the loose deposit, significant incision was found and the incision undergoes a common exponential natural process. The half-life time is estimated about 3.2–4.3 years. On the other hand, cliff recession is associated with the extreme climate events and the recession rate is found to increase after 2003.