Rockslide Research Articles

Ferguson rock slide buries California State Highway near Yosemite National Park

During spring 2006, talus from the toe area of a rock-block slide of about 800,000 m3 buried California State Highway 140, one of the main routes into heavily-visited Yosemite National Park, USA. Closure of the highway for 92 days caused business losses of about 4.8 million USD. The rock slide, composed of slate and phyllite, moved slowly downslope from April to June 2006, creating a fresh head scarp with 9–12 m of displacement. Movement of the main rock slide, a re-activation of an older slide, was triggered by an exceptionally wet spring 2006, following a very wet spring 2005. As of autumn 2006, most of the main slide appeared to be at rest, although rocks occasionally continued to fall from steep, fractured rock masses at the toe area of the slide. Future behavior of the slide is difficult to predict, but possible scenarios range from continued scattered rock fall to complete rapid failure of the entire mass. Although unlikely except under very destabilizing circumstances, a worst-case, rapid failure of the entire rock slide could extend across the Merced River, damming the river and creating a reservoir. As a temporary measure, traffic has been rerouted to the opposite side of the Merced River at about the same elevation as the buried section of Highway 140. A state-of-the-art monitoring system has been installed to detect movement in the steep talus slope, movement of the main slide mass, local strong ground motion from regional earthquakes, and sudden changes in stream levels, possibly indicating damming of the river by slide material.

Correlation between natural slope angle and rock mass strength rating in the Betic Cordillera, Granada, Spain

This study proposes a method to determine zones gentler or steeper than the equilibrium slope angle based on rock mass strength (RMS) and to regionalize the parameters. The method was developed using GIS and applied to rock masses of the Alpujarride Complex (Granada, Spain). 41% of the natural slopes studied have angles lower than the equilibrium due to dissolution processes and the presence of alluvial or colluvial deposits, while 28% of those slopes have angles higher than the equilibrium due to rapid erosion in tectonically active zones. Cross correlation analysis between maps showing degrees of slope equilibrium and landslide inventories suggest that long-term geomorphic changes have induced slope angles higher than the equilibrium which are associated with rock falls and rock slides.

Slovenian National Landslide DataBase – A promising approach to slope mass movement prevention plan

The Slovenian territory is, geologically speaking, very diverse and mainly composed of sediments or sedimentary rocks. Slope mass movements occur almost in all parts of the country. In the Alpine carbonate areas of the northern part of Slovenia rock falls, rock slides and even debris flows can be triggered. In the mountainous regions of central Slovenia composed from different clastic rocks, large soil landslides are quite usual, and in the young soil sediments of eastern part of Slovenia there is a large density of small soil landslides. The damage caused by slope mass movements is high, but still no common strategy and regulations to tackle this unwanted event, especially from the aspect of prevention, have been developed. One of the first steps towards an effective strategy of struggling against landslides and other slope mass movements is a central landslide database, where (ideally) all known landslide occurrences would be reported, and described in as much detail as possible. At the end of the project of National Landslide Database construction which ended in May 2005 there were more than 6600 registered landslides, of which almost half occurred at a known location and were accompanied with the main characteristic descriptions. The erected database is a chance for Slovenia to once and for all start a solid slope mass movement prevention plan. The only part which is missing and which is the most important one is adopting a legal act that will legalise the obligation of reporting slope mass movement events to the database.

Wettability Determination of the Reservoir Brine−Reservoir Rock System with Dissolution of CO2 at High Pressures and Elevated Temperatures

An experimental method has been developed to determine the wettability, i.e., the contact angle, of a reservoir brine−reservoir rock system with dissolution of CO2 at high pressures and elevated temperatures by using the axisymmetric drop shape analysis (ADSA) technique for the sessile drop case. Prior to the experiment, a rock slide is horizontally placed in a specially designed rock slide holder in a see-through windowed high-pressure cell, which is subsequently filled with CO2 at a prespecified pressure and a constant temperature. Then, a reservoir brine sample is introduced by using a syringe delivery system to form a sessile brine drop on the rock slide inside the pressure cell. The sequential digital images of the dynamic sessile brine drop are acquired and analyzed by applying computer-aided image acquisition and processing techniques to measure the dynamic contact angles at different times. It is found that the dynamic contact angle between the reservoir brine and the reservoir rock remains almost...

Alternative approaches for analyses of a 100,000 m3 rock slide based on Barton–Bandis shear strength criterion

A data set was derived for the Aknes rock slope, Norway, with the main focus on deriving input parameters for the Barton–Bandis shear strength criterion. Back-calculations of a 100,000 m3 rock slide were performed for evaluation of the data set. The limit equilibrium analysis showed that the joint roughness coefficient (JRC) has the greatest effect on the calculated safety factor of the slide. Probabilistic computations showed that the JRC stands out as the most important contributor to the total uncertainty over the whole set of variables and that the computed failure probability of the 1960 slide was very high, which may be interpreted that the input variables and the Barton–Bandis shear strength criterion are reasonable for the slide. JRC was measured on 0.25 m scale and on 1 m scale. The results from the two scales were different.

A channelised long run-out debris slide triggered by the Noto Hanto Earthquake in 2007, Japan

A strong earthquake (MJ 6.9, MW 6.6–6.7) at about 11 km depth hit the western shore of the Noto Peninsula on Honshu, Japan, at about 00:42 coordinated universal time (9:42 a.m. local time) on 25 March 2007 (the Noto Hanto Earthquake in 2007). The earthquake triggered only 61 landslides, with most traveling short distances. It caused one long run-out landslide in the Nakanoya district of Monzen town, Wajima city, Ishikawa Prefecture, when a portion of a deep-seated landslide transformed into a moderate debris slide down a channel. The rock slide occurred on a south-facing convex-shaped slope on a small spur where earthquake ground shaking likely was strongly amplified by topography. A portion of the rock slide reached a small channel floored by materials containing abundant groundwater. Constant-volume box-shear tests on normally consolidated saturated specimens revealed that the apparent angle of internal friction of the channel-floor material was 33–36° at 10-mm shear displacement and did not show much decrease in effective normal stress during shearing. In situ rock-sliding testing on the exposed channel materials showed a low kinetic-friction angle of about 21°. We suggest that an unsaturated portion of the rock slide slid down the channel, with sliding between the rock-slide mass and the channel floor. Because the slope angle of the travel path nearly equaled the kinetic-friction angle, the unsaturated rock slide mass may have traveled at a moderately slow speed, or it might have decelerated and accelerated. Slow speed is supported by accounts from local residents that suggest movement of debris continued for 3 days after the main shock.

Geomorphological hazards and monitoring activity along the western rocky coast of the Portofino Promontory (Italy)

The results of geomorphological studies and monitoring activity conducted in the western sector of the Portofino Promontory are presented here. This sector is characterized by numerous, extensive landslide masses and there is evidence of their reactivation during the last century. The instability phenomena can be attributed to landslides with complex kinematics classifiable as rock slump and rock topple, rock slide and rock fall, and rock fall and rock flow. They have involved hamlets and communication routes, with observable damage to man-made structures and terraced agricultural terrain, including collapses and deformations of the dry-stone walls. The geomorphological surveys, the boreholes and the monitoring activity have shown that several landslides are active, with movement rates of some cm/year. With the presence of predisposing factors relating to the structural lithology and geomorphology of the rocky slopes, the triggering causes of the gravitational movements are attributable to extreme heavy rainfall and to wave cutting, often with concomitant action on the part of both. The study offers a contribution to encourage concrete efforts to continue the monitoring of this area; the overall objective would entail the planning of general stabilization measures, or at least measures to reduce evident geomorphological risks, also taking into account the remarkable environmental value and qualities of this coastal sector.

Landslides triggered by the 8 October 2005 Kashmir earthquake

The 8 October 2005 Kashmir earthquake triggered several thousand landslides. These were mainly rock falls and debris falls, although translational rock and debris slides also occurred. In addition, a sturzstrom (debris avalanche) comprising ∼ 80 million m 3 buried four villages and blocked streams to create two lakes. Although landsliding occurred throughout the region, covering an area of > 7500 km 2, the failures were highly concentrated, associated with six geomorphic–geologic–anthropogenic settings, including natural failures in (1) highly fractured carbonate rocks comprising the lowest beds in the hanging wall of the likely earthquake fault; (2) Tertiary siliciclastic rocks along antecedent drainages that traverse the Hazara–Kashmir Syntaxis; (3) steep (> 50°) slopes comprising Precambrian and Lower Paleozoic rocks; (4) very steep (» 50°) lower slopes of fluvially undercut Quaternary valley fills; and (5) ridges and spur crests. The sixth setting was associated with road construction. Extensive fissuring in many of the valley slopes together with the freshly mobilized landslide debris constitutes a potential hazard in the coming snowmelt and monsoon seasons. This study supports the view that earthquake-triggered landslides are highly concentrated in specific zones associated with the lithology, structure, geomorphology, topography, and human presence.

High-resolution mapping of rock fall instability through the integration of photogrammetric, geomorphological and engineering–geological surveys

A semi-quantitative methodology for rock fall susceptibility assessment is presented. The test area is located along the Amalfi coast (Sorrento Peninsula, Southern Italy) which is characterized by high relief energy and very steep slopes, made up of dolomite limestone of Mesozoic age. Generally, the cliffs are strongly jointed and affected by karst processes. For this reason rock falls, rock slides and, more seldom, topples are very frequent in the area. The study took a multidisciplinary approach mixing classical field geology observations with typically geo-mechanical ones and required the support of highly professional staff, such as applied geologists, experts in photogrammetric survey techniques and engineers for stabilization works planning. The acquisition of the data involves a detailed large-scale study (scale 1:500). This methodology is mainly suitable for the study of single cliffs or slope with limited dimensions. Cartographic representation is a main problem in the study of a vertical cliff. A frontal topographic survey (terrestrial photogrammetry) was first carried out. After this, different geo-thematic maps showing the main geological, geomorphological and geostructural information were elaborated and then compared, allowing the elaboration of the triggering susceptibility map. The semi-quantitative proposed method has a good accuracy in the realization of the potential detachment area of rock falls, in order to predispose stabilization works and to rationalize the disposal resources for the hazard mitigation in the unstable areas near human utilization (urban centres, roads, etc.).

Landslide analysis in Apennine chain areas

The paper exposes the results of the study carried out in chain geological context where slopes, because of their lithology and local climate conditions, show to be historically affected by landsliding. The knowledge of the geologic context and of the geomorphological features characterizing an area represents the first step to identify the causes that led to landsliding and to describe its evolutive style. In geological chain areas, the physical properties and rock layering often facilitate slope instability and mass wasting. The study area belongs to the southern slope of the Peloritani Mountains (Sicily, Italy) and lies within the hydrographic basin of the Roccella torrent, an affluent of the Alcantara River. In this area, the slopes that are mainly constituted by flyschoid alternations tectonized during the formation of the Apennine–Maghrebian chain are affected by numerous landslides whose activity permits a detailed study of their evolution. The instability that characterizes the entire basin of the Roccella torrent is well represented by the complex rock slide–earth flow of Roccella Valdemone that has destroyed part of the village of the same name. The paper describes the last landslide event and suggests its previous evolutive history, along with the evolutionary tendency of the slope, through a comparison of several sections at a scale of 1:2,000 that was made on the topographic map carried out in 1970 and successively updated in 1990. Furthermore, the volume of mobilized rock and the erosion rate have been calculated from two different discrete element methods. The results are supported by borehole, seismic, and geoelectrical data confirming the analytical procedure’s validity, applied for complex landslides description, besides the acquisition of useful information for in situ investigation planning in analogous geological frameworks, where instability-induced phenomena are frequent and historical data are fragmentary or missing.

Landslides around the Pliocene lava plateau in west Hokkaido:catastorophic rockslide avalanche at Mt.Teine and landslide at Mt. Tengudake

札幌市の西に広がる後志火山性台地は，中新世後半から更新世にかけて形成された溶岩台地で，平坦面溶岩が広く分布しその火山原面が残されている.また，活発な火山活動は変質作用を伴い，多くの金属資源が開発されてきた．これらの地質要因を背景とする大規模地すべりを含む地すべり地形が広く分布し，時には自然災害としてあるいは開発行為を契機に地すべり活動が発生している．この見学コースでは，地質時代に発生した山体崩壊と岩屑なだれ堆積物，周氷河斜面堆積物を母材とした地すべりを観察する．

Remote Sensing Observations of Landslides and Ground Deformation from the 2004 Niigata Ken Chuetsu Earthquake

In recent years, major developments in remote sensing have made it possible to use these technologies to document the effects of earthquakes. Specifically, high-resolution satellite imagery and three-dimensional laser scanning (LIDAR) can provide important observations of earthquake damage that supplement traditional observations from field reconnaissance. The 2004 Niigata Ken Chuetsu earthquake provided an opportunity to use remote sensing to document the distribution of landslides in the epicentral region through the use of high-resolution satellite imagery and to document the detailed three-dimensional geometries of several failures using LIDAR. The satellite imagery was acquired the day after the earthquake, but at very large acquisition angles that resulted in image distortion. Nonetheless, the satellite imagery accurately identified the landslide distribution in the epicentral region, although the total area of landslides was underestimated by about 25% as compared with traditional aerial reconnaissance because of the large acquisition angle for the satellite imagery. Terrestrial LIDAR was used to collect three-dimensional data at several failure sites, including two large rock slides and a railroad tunnel portal affected by ground deformation. The LIDAR data allowed for precise measurement of failure deformations and geometries, and provided digital terrain models that could be archived and used in future analyses. In the future, satellite imagery and LIDAR, as well as other remote sensing technologies, will play an increasing role in documenting and understanding the effects of earthquakes.

Mapping fractures with GPR: A case study from Turtle Mountain

Ground-penetrating radar (GPR) surveys were acquired of rocks on the highly fractured summit of Turtle Mountain in Canada. In 1903 a disastrous rock slide occurred at Turtle Mountain and it still poses a geologic hazard. Dips, shapes, and penetration depths of fractures are important parameters in slope-stability analysis. Determination of fracture orientation at Turtle Mountain has been based mostly on areal geologic mapping and, most recently, on data collected from boreholes. The purpose of GPR surveys was to test, confirm, and extend information about fractures and bedding planes. Data acquisition was complicated by the rough terrain; because slopes are steep and uneven. This also complicated analysis of the data. Measurement of in situ velocity — an important value for migration — was impossible. Instead, data were migrated with different velocities and data results were chosen that were considered to be reasonable. Analysis and interpretation of the data, resulted in confirmation and extension of the a priori information on orientations of fractures and bedding planes at Turtle Mountain. Despite the rough terrain and highly fractured rock mass, GPR surveys provide reliable information about the shapes and density of fractures — information important for slope-stability evaluation. The most reliable migration results obtained for velocities were considerably less than the standard velocities recorded for limestone, the dominant lithofacies at Turtle Mountain. We interpret this observation as an indicator of water within the rock. However, thorough investigation of this conclusion remains a project for future work.

English

The Elizabeth mine Superfund site offers unique opportunities to investigate the interplay between geochemical and physical processes in the geochemical evolution of an acidic pit lake. The mine exploited a steeply dipping massive sulfide ore body. Ores contained pyrrhotite and chalcopyrite and were hosted by siliciclastic sedimentary rocks and amphibolites. An open pit that accessed part of the ore body is filled by a long (380 m), narrow (< 25 m), and shallow (< 7 m) lake, which is divided into two parts by a rock slide. The southern end serves as a decant point, and discharges for most of the year. Quarterly sampling and continuous temperature monitoring of the water column in the lake document geochemical variations that depend on seasonal variations in the amount of precipitation and the presence or absence of ice. From spring to fall, parameters show limited variation with depth except for temperature, which decreases with depth. The lake experienced overturn in the fall. During winter under ice cover, the lake developed a chemocline shown by a sharp decrease in pH, a doubling of total dissolved solids (TDS), and a ten-fold increase in dissolved Fe with depth (0.4 - 55.2 mg/L). Oxia throughout most of the year causes removal of Fe, but low pH prevents significant sorption of Cu and other metals. Ca (25 - 72 mg/L), Mg (9.6 - 15.0 mg/L), K (6.0 - 8.3 mg/L), Si (6.7 - 9.6 mg/L), and SO4 -2 (210 - 280 mg/L) are the major dissolved constituents during non-stratified ice-free periods; Fe (0.2 - 0.5 mg/L), Al (1.0 - 3.1 mg/L), Cu (0.6 - 1.2 mg/L), and Zn (0.3 - 0.5 mg/L) are important minor dissolved constituents. Throughout the year, the water quality is dependent upon a variety of factors including the geometry of the pit, the short residence time of water within the pit, wind mixing and fall overturn, the oxidation of sulfides on the pit walls and in the unsaturated waste on the floor of the pit south of the haulage way, oxidation of iron within the water column, and mixing of surface waters with high TDS waters entering the bottom of the lake.

The Zymoetz River landslide, British Columbia, Canada: description and dynamic analysis of a rock slide–debris flow

The Zymoetz River landslide is a recent example of an extremely mobile type of landslide known as a rock slide–debris flow. It began as a failure of 900,000 m3 of bedrock, which mobilized an additional 500,000 m3 of surficial material in its path, transforming into a large debris flow that traveled over 4 km from its source. Seasonal snow and meltwater in the proximal part of the path were important factors. A recently developed dynamic model that accounts for material entrainment, DAN3D, was used to back-analyze this event. The two distinct phases of motion were modeled using different basal rheologies: a frictional model in the proximal path and a Voellmy model in the distal path, following the initiation of significant entrainment. Very good agreement between the observed and simulated results was achieved, suggesting that entrainment capabilities are essential for the successful simulation of this type of landslide.

High Spatial Resolution Satellite Imagery, DEM Derivatives, and Image Segmentation for the Detection of Mass Wasting Processes

An automated approach to identifying landslides using a combination of high-resolution satellite imagery and digital elevation derivatives is offered as an alternative to aerial photographic interpretation. Previous research has demonstrated that per pixel spectral response patterns are ineffective in discriminating mass movements. This technique utilizes image segmentation and digital elevation data in order to identify mass movements based not only on their reflectance but also on their shape properties and their geomorphic context. Dividing the classification by process into debris slides, debris flows, and rock slides makes the method far more useful than methods that group all mass movements together. A hierarchical classification scheme is utilized to eliminate areas that are not of interest and to identify areas where mass movements are probable. A supervised classification is then conducted using spectral, shape, and textural properties to identify failures that were greater than 1 ha in area. The resulting accuracy was 90 percent for debris slides, 60 percent for debris flows, and 80 percent for rock slides.

Space‐borne and ground‐based SAR interferometry as tools for landslide hazard management in civil protection

In recent years, SAR interferometry has become one of the most popular emerging techniques for the assessment of ground displacements, and, as such, it is of great interest as a possible operational tool for civil protection institutions having to deal with landslide risk. The paper presents some of the results obtained in northern Italy during a research project aimed at testing the potentiality of the application of C‐band space‐borne interferometry and Ku‐band ground based interferometry during different specific civil protection activities. Main research objectives were the detection of the movements of complex earth and rock slides affecting built‐up areas during the 1990s, and the near real‐time monitoring of a reactivated rotational earth slide over an emergency period of 15 days. Results of space‐borne interferometry did qualitatively fit with the geological interpretation of the mass movements and with ground truths such as damaged buildings and in situ monitoring systems. However, this was not achieved in quantitative terms, suggesting that this technique should be used limitedly for displacement recognition and not monitoring. On the other hand, ground‐based interferometry proved valuable both for a qualitative and a quantitative estimate of slope movements. Nonetheless, the research has also enabled the limitations that are still to be tackled in order to bring these systems to an operational usage in civil protection to be highlighted.

Sediment production and delivery from recent large landslides and earthquake-induced rock falls in the Upper Soča River Valley, Slovenia

Landsliding not only changes the morphology of the terrain but is also an effective factor in sediment production. Extreme events such as earthquake-induced large rock falls or rainfall-induced landslides may, during the event itself or in a period after it, greatly increase the sediment delivery and river sediment transport. The effects of strong earthquakes and large landslides on sedimentation are evident in the Upper Soča River basin, NW Slovenia. The annual sediment production in the headwaters of this typical alpine valley in western Slovenia is estimated to average>1000 m3 km−2 a−1. In the last few years, two large landslides triggered there were of comparable volume but differed regarding sediment delivery to the fluvial network. The 2000 Stože landslide at 1.5 million m3 was a debris flow that delivered more than 1 million m3 to the Koritnica River. The Strug complex landslide was initiated in 2001 by a rock slide and soon amounted to an estimated volume of 310,000 m3. In 2002, it released over 20 rainfall-induced debris flows on the order of 100 to 1000 m3 to the fluvial system.In mountainous terrain in the headwaters of the Upper Soča River, slope failures may occur during strong earthquakes depending on the event magnitude. The earthquake of April 12, 1998 (MS 5.6) caused more than 100 failures, among them 50 rock falls. About 260,000 m3 of rock fall material will remain on hill slopes with no potential of reaching the river network, while an estimated volume of 480,000 m3 may be released to watercourses in a longer period during extreme events. About 200,000 m3 of rock fall debris was deposited in areas from where the material was released to watercourses during rainfall events. As a consequence of the 1998 earthquake, hyperconcentrated flows were observed during floods in some torrential tributary channels of the Upper Soča River. After the earthquake of July 12, 2004 (MS 4.9), 50 rather superficial slope failures including 38 rock falls were registered. From 2000 until 2004, more than 150,000 m3 sediments were dredged from the Upper Soča River channel.

Internal structure of an alpine rock glacier based on crosshole georadar traveltimes and amplitudes

ABSTRACTRapid melting of permafrost in many alpine areas has increased the probability of catastrophic rock slides. In an attempt to provide critical structural information needed for the design and implementation of suitable mitigation procedures, we have acquired low frequency (22 MHz) cross‐hole radar data from within a fast‐moving rock glacier, an important form of alpine permafrost. Since the ice, rock and pockets of water and air found in the underground of high alpine areas have very different dielectric permittivities and electrical conductivities, the radar method was well‐suited for investigating the structure and state of the rock glacier. Our interpretation of the radar velocities and attenuations was constrained by geomorphological observations, borehole lithological logs and the results of a surface seismic survey. The radar data revealed the existence of a discontinuous 7–11 m thick ice‐rich zone distinguished by high velocities (0.14–0.17 m/ns) and low attenuations (0.04–0.09 m−1) and a thin underlying ice‐free zone characterized by moderate velocities (0.11–0.12 m/ns) and low attenuations (0.04–0.09 m−1). Beneath these two zones, we observed a prominent band of high velocities (0.14–0.17 m/ns) and moderately high attenuations (0.10–0.20 m−1) associated with unconsolidated glacial sediments and numerous large air‐filled voids, which in the past were probably filled with ice. At greater depths, the variably dry to water‐saturated sediments were represented by generally lower velocities (0.08–0.10 m/ns) and higher attenuations (0.16–0.24 m−1). The bedrock surface was represented by an abrupt ∼0.03 m/ns velocity increase. We speculate that the disappearance of ice, both laterally and with depth, occurred during the past one to two decades.

Failure mechanism in an extremely slow rock slide at Bitchu-Matsuyama castle site (Japan)

One of the specific problems related to historical structures is the fact that they are prone to damage caused by even very small deformations acting over a long period of time, such as creep or extremely small rock displacements. If any damage has already occurred, the determination of the rock slope failure mechanism is one of the prerequisites for successful mitigation technique selection. In this study a medieval castle in central Japan, suffering damage caused by deformation of the rock mass in the subgrade of the castle, was investigated using a combination of field investigation, high-precision monitoring and physical modeling experiments. Using these techniques an attempt to determine the failure mechanism of the rock slope was made. Based on the field investigation a toe-slope failure seemed to be the main triggering factor activating the deformations in the upper slope area, right below the defense walls of the castle. The displacement monitoring of the surface rock blocks revealed a slumping failure with the backward rotational component prevailing over the sliding in the immediate vicinity of the castle wall. This was in accordance with the expectations obtained from the structural analysis of the rock mass carried out during the field investigation. The displacements obtained during the rock block monitoring, especially from the crack gauges, were not sufficient for drawing a satisfactory conclusions about the failure mechanism of the blocks located in the central part of the slope. Therefore, the failure mechanisms of rock blocks inferred from their displacements obtained from the monitoring were correlated with the results of modeling experiments carried out on the scaled slope model. The physical modeling revealed a possibility of toppling failure of rock blocks in the central area of the slope caused mainly by block interlocking, which was supported by the data from surface tilt meters installed additionally in the field. Furthermore, the possibility of the occurrence of forward and backward rock block rotations in the same sliding body at given conditions was supported by the physical modeling experiments.