Markus Schleier

Landslide reliability analysis based on transfer coefficient method: A case study from Three Gorges Reservoir

To evaluate the reliability of a landslide in a reservoir, the universal transfer coefficient method, which is popularized by the Chinese standard, is adopted as performance function in this study for: (1) common deterministic method stability evaluation; (2) reliability evaluation based on a Monte Carlo method; (3) comparison of landslide reliability under different water levels and under different correlation coefficients between soil shear strength parameters (c, Φ), respectively with mean, standard deviation, reliability coefficient and failure probability. This article uses the Bazimen (八字门) landslide, which is located at the outlet of Xiangxi (香溪) River in the Three Gorges Reservoir, as an example to evaluate its stability and reliability under different water levels with two-dimensional deterministic and probabilistic methods. With the assumption that constant mean and normal distributed shear strength parameters (c, Φ), correlation coefficient ρc, Φ=−1 based reliability analysis, compared with ρc, Φ=0 and 1, indicates obviously more increase of reliability index and lower standard deviation as water levels rise. To the case of a certain water level, ρc,Φ=−1 does not have constantly positive or negative effects on landslide reliability compared with ρc, Φ=0 or 1, but is associated with water level. Whereas the safety factor Fs by deterministic method, which is almost the same value as corresponding mean of safety factor from probabilistic analysis, will increase slightly as water level increases.

Research on water–rock (soil) interaction by dynamic tracing method for Huangtupo landslide, Three Gorges Reservoir, PR China

AbstractAs groundwater activity develops in a landslide system, the water–rock (soil) interaction increasingly influences the development of the landslide hazard. In this paper, Huangtupo landsli de was chosen as the subject of our research, which is located beside the Three Gorges Reservoir and the deformation continued for a long time. First, based on a comprehensive field survey, ten types of bad geological elements which probably induce the deformation were collected from different parts of landslide. These include a soft rock layer, the sliding soil, a weak intercalation and the typical rock close to the slip zone. Then, to trace the internal relationships among these samples, the microstructure, chemical composition of minerals, the migration and evolution of clay minerals, also the particle size distribution characteristics of all the samples were analyzed separately. Comparison of the result shows, that the evolutionary paths are very obvious among these samples. With the activities of water–rock (soil) interaction, the formation and evolution of main bad geological elements can be summarized. Afterwards, the detailed mechanism of interaction is revealed by focusing on four samples which compose one of these three paths, using additional data from physical and mechanical tests, the study shows how water–rock (soil) interaction affects the microstructure and weakens the mechanical properties of rock and soil. The presented detailed research probes the water–rock (soil) interaction mechanism specifically for Huangtupo riverside landslide as a case study. Furthermore, the applied multi-sample dynamic tracing method is verified as a means to discover and illustrate the deformation mechanism of landslides.

Rock-avalanche activity in w and s Norway peaks after the retreat of the scandinavian ice sheet

We have compiled recently published and unpublished cosmogenic 10Be exposure ages of rock-avalanche deposits and break away scars in western and southern Norway in order to compare those to the retreat of the Scandinavian ice sheet. In total 22 rock-avalanche events were dated by their deposits (19) or break away scars (3). Sampling of rock-avalanche deposits and failure surfaces was not systematic over the region but with few exceptions we sampled all deposits within the same valley. All ages were recently calculated using the CRONUS online calculator and the geochronology ensemble reveal five late Pleistocene events, eight Preboreal events, and nine younger events. The decay of the Scandinavian ice sheet was not spatially synchronous but differed regionally and lasted over several thousand years in places, hence the requirement for widespread dating targets. One rock avalanche (at Innerdalen at 14.1 ka) occurred when ice existed in the valley, which is in agreement with the latest deglacial models. Depositional characteristics of ten (44%) of the rock avalanches suggest ice free conditions although they occurred within the first millennia following local deglaciation. Five events (22%) occurred between 9 and 7.5 ka at a time when climate was warmer and moister than today. Finally seven events (30%) appear to be relatively evenly distributed throughout the rest of the Holocene. Although limited in number we interpret that the dated events are representative of the temporal distribution of post-ice sheet rock avalanches in western Norway. However, the number of rock avalanches occurring onto the decaying ice sheet is likely underrepresented as those deposits are reworked and can be difficult to distinguish from moraine deposits. Our widespread data reveal a rapid rock slope instability response to the initial local decay of the Scandinavian ice sheet followed by a lower and constant frequency following the climate optimum (ca. 8.5 ka) in the Holocene.

Large scale mass movements triggered by the Kashmir earthquake 2005, Pakistan

The SPOT image analysis in Muzaffarabad Azad Kashmir, northwest Himalayas, Pakistan reveals that the Kashmir earthquake 2005 triggered a number of coseismic mass movements along the hanging wall block of the Muzaffarabad Fault. The Neelidandi and Langarpura rock falls have been identified as two major reactivated mass movements with an estimated volume of 3.1 × 106 m3 and 5.76 × 106 m3, respectively. The Neelidandi and Langarpura mass movements were initiated during earthquake in the direction of northwest-southeast extension and northeast-southwest directed thrusting, respectively. The Neelidandi rock fall occurred in sheared cherty dolomites and limestones of the Cambrian Muzaffarabad Formation, whereas the Langarpura rock fall occurred in alternating clays, shales, claystones, siltstones and sandstones of the Miocene Murree Formation. These rock units along the fault are highly fractured and jointed. The geotechnical maps and geological longitudinal profiles show the relationship between the geometrical characteristics and mechanism of these mass movements. Their characteristics were analyzed according to the role of topographic, seismic, geological and tectonic factors. The steep topography, sheared rocks, lithology, coseismic uplift and strong ground shaking of the hanging wall block along Muzaffarabad Fault facilitated the gravity collapse of these mass movements.

Rock Avalanches in a Changing Landscape Following the Melt Down of the Scandinavian Ice Sheet, Norway

Rock avalanches can form complex deposits for which the interpretation can be challenging, especially if they occur in valleys affected by other ‘fast’ geological processes, such as, glaciations or isostatic rebound. The mountains of western Norway enable to study rock avalanches in such a complex geological setting. Within the two valleys of Innerdalen and Innfjorddalen (~70 km afar), several rock avalanches occurred since the Late Pleistocene. The rock avalanches in Innerdalen have volumes of 31 × 106 and 23 × 106 m3 and yielded terrestrial cosmogenic nuclide 10Be ages of 14.1 ± 0.4 and 7.97 ± 0.94 ka, while those in Innfjorddalen have volumes of 15.1 × 106, 5.4 × 106 and 0.3 × 106 m3 and yielded ages of 14.3 ± 1.4, 8.79 ± 0.92 ka and 1611–12 CE, respectively. Although being of nearly similar age, the rock avalanches in both valleys occurred under different environmental settings associated with the decay of the Scandinavian ice sheet. One of which fell onto a retreating valley glacier, partly depositing as supraglacial debris (Innerdalen), while the contemporaneous one fell into a fjord, partly forming a subaqueous deposit which is today exposed due to post-glacial isostatic uplift (Innfjorddalen). The younger rock avalanches fell into the ice-free valleys onto the older rock-avalanche deposits. All of the observed rock avalanches are preserved in rock-boulder deposits distributed on the valley floor and its slopes showing a variety of geomorphological features and landforms, which are diagnostic for their paleodynamics. Numerical runout modeling using DAN3D supports the landform interpretations, which are further confirmed by 10Be ages of the rock-avalanche deposits. The presented description of rock-avalanche deposits can enable a better identification and interpretation of similar deposits in other mountain areas and contributes to the knowledge of Quaternary landscape evolution in western Norway, such as, ice-sheet thickness and post-glacial isostatic rebound.