Stože Landslide – A Case History

Geologija, 2007

The landslide Slano Blato, is situated above the village Lokavec near Ajdov{~ina in the weat of Slovenia. It has a relatively long history and was first mentioned in a document in 1887. At that time it destroyed a part of a main road and reconstruction works took 17 years. In the last decade, movement of the landslide was observed in November 2000, when it reached distances of 60-100 m/day. By means of geotechnical research work on the landslide in the year 2004, several rheological tests were also carried out, which is not usual for geotechnical research work. A stability analysis was carried out numerically by applying the Burger elasto-plastic model. The model took into account geomechanical and rheological characteristics of the landslide. Izvle~ek Plaz Slano Blato leži nad vasjo Lokavec pri Ajdov{~ini v zahodnem delu Slovenije. Ima že dokaj dolgo zgodovino, saj je bil v dokumentih omenjen že leta 1887. V tem ~asu je uni~il glavno cesto in njegova sanacija je trajala 17 let. V zadnjem desetletju so bili prvi ve~ji premiki na plazu v novembru 2000. Najve~ji izmerjeni pomiki splazele mase so bili 60-100 m/dan. V letu 2004 so se izvajale geotehni~ne raziskave za namen pridobitve podatkov za sanacijo plazu. V sklopu teh raziskav so bile izvedene tudi obsežne reolo{ke raziskave. Stabilnostne analize so bile izvedene z Burgerjevim elasto-plasti~nim modelom. Model pri izra~unu upo{teva geomehanske in reolo{ke karakteristike splazele mase.

This paper presents the results from the investigations and applied remedial works on a specific case of landslide. Namely, in a town of Veles in R.Macedonia, a large landslide exists on intensively urbanized hilly area. According to the existing data, the main mass movements occurred during 1963. Unfortunately, after 1963, the area was intensively "urbanized", especially in a zone on the top of the landslide. After longer period without visible mass movements, a landslide zone was reactivated during 1999 and 2002. The extent of the damage on the housing and other infrastructure has a character of real natural disaster. The reactivation and high level of damage on the infrastructure was a reason to perform complex investigations including geophysical, geological, geotechnical methods, inclinometer and geodetic measurements etc. The investigations and remedial work were performed in two phases. The results from the geotechnical investigations indicate that the landslide character is very complex. The landslide length is about 320m, with 80-90m average width, where the landslide thickness on certain places reaches up to 20 meters. The volume of the moved mass is in a range of about 400 000m 3 . After defining the geotechnical models, a complex analytical and numerical analyses were performed with the help of sophisticated programs, SLIDE 4 (limit equilibrium methods-stability back analyses) and PLAXIS v 8.1 (finite element method for analyze of stress-deformation conditions). Having in mind the complexity of the landslide from one and the presence of the highly urbanized region, from the other side, the suggested remedial works are extensive and designed in two phases. In the first phase, by unloading the top of the landslide (scattered profile), in combination with a technical solution of flexible reinforced sheet-pile retaining wall structure consist of 67 deep piles is designed. The diameter of the piles is about 90 cm. They are placed in two rows, and spaced generally on 3 meters one from each other. This phase is completely finished, and the obtained results on the stability conditions of the field are very satisfactory. Afterwards, inspecting the results and effects from the first phase in details, the second phase was designed. The solution is again based on retaining wall structure with reinforced piles, in some zones combined with tensioned anchors. The design is made and the whole project is in a phase of tendering procedure. With these measures, it's expected the problem with mass movements to be resolved in an appropriate way. The conclusion will be that the urbanization must follow the logic of the natural environment and every kind of unplanned construction can only lead to high level of risks on the surrounded area and disaster.

1. INTRODUCTION The evolution of stresses inside a soil slope mass and the consequent change of the status from stability towards instability, is usually described by the variation of the resistant and active forces (or moments) ratio, known as safety factor (Fs). In this ratio, the active forces are quite easily determined, whereas the shear strength is usually determined by geotechnical laboratory tests, or, less often, by in situ tests. In both cases, however, measurements may be affected by numerous uncertainties, caused, for each type of soil, by the following: • scale and shape factors • anisotropy and non homogeneity • dependence on the strain • non representativeness of the sampling • sampling or probe preparation disturbances • test errors, such as, the use of distilled water interacting with soil, or, anyhow, of water with a different chemism from that of the interstitial water (Spilotro, Fidelibus, 1995 ; Di Maio, 1996). For these reasons, the strength, (mean along failur...

2011

Engineering Geology, 2004

... doi:10.1016/j.enggeo.2004.01.011 | How to Cite or Link Using DOI Copyright © 2004 Elsevier BV All rights reserved. Permissions & Reprints. Hydrologic conditions responsible for triggering the Sto e landslide, Slovenia. ... 1. Introduction. 1.1. Land sliding in Slovenia. ...

Several metres thick top cover of a hillside slid down in a town near to Budapest. Buildings, communication and utility lines suffered damage. The author has found the cause of the movement in the seeping ground-water on the top of the underlying highly plastic clay. The design of stabilization rested on underground investigations and finite element analysis. The actual event calls the attention what type of careful arrangements are needed at similar construction projects.

European Journal of Environmental and Civil Engineering, 2014

Numerical modelling represents a powerful technique to develop a quantitative assessment of the stress-strain mechanisms leading to either first-time slope failures or evolution of slopes already failed in the past. In this perspective, a valid interpretation of the landslide behaviour and an adequate strategy of risk mitigation can be achieved from a numerical validation of both the causative factors and the evolution mechanism that have been previously assumed according to detailed phenomenological or simple analytical approaches. This paper presents two case histories of slow landslides in clay slopes, both located in Puglia (Southern Italy), for which detailed phenomenological studies have been firstly carried out to infer assumptions on the slope failure mechanisms that have been later on verified by means of numerical analyses accounting for soil mechanical behaviour and slope hydraulic processes. The first case study concerns the first-time failure of a stiff clay slope in Lucera, which has been induced by the slow dissipation of negative excess pore water pressures generated by previous quarry excavation at the slope toe. The second case history is represented by the analysis of the stress-strain evolution of the ancient Volturino landslide, which is observed to reactivate mainly in wet seasons.

This article deals with landslide geomorphology, which should be placed alongside fluvial, tectonic, karst, coast, or slope geomorphology. Slovenia is used as an example to present landslide susceptibility mapping and the relative landslide rate, which was used to quantify the relative role of landslides in recent relief development in comparison to other fluvio-denudational or erosion processes. Landslides are a geographical constant in certain areas, and in the past some researchers have also used expressions such as landslide-prone region for certain regions of Slovenia. The last section deals with geographers' role in landslide hazard research, which consists of several activities, although map-making remains the fundamental skill applied by geomorphologists. Methods of landslide hazard assessment are also discussed.

Journal of Mountain Science, 2005

A catalogue of possible landslide initial failure mechanisms, taking into account the geological setting and the geometry of the slope, the joint structure, the habitus of the rock blocks, as well as the mechanical behaviour of the rocks and of the rock mass (deformation and strength parameters), is presented. Its aim is to give geologists as well as engineers the opportunity to compare phenomena in the field and phenomena belonging to particular mechanisms and to find the mechanism occurring. The presented catalogue of initial landslide mechanisms only comprises the mechanisms having a clearly defined mechanical model that can be divided into empirical relations and into mechanical models, as well as an overview of run out models, which can be divided into empirical relations and into mechanical models.

Journal of Geotechnical and Geoenvironmental Engineering, 2005

This paper presents recommendations for selecting the type and magnitude of drained shear strength parameters for analysis of landslides. In particular, the importance, existence, and use of the cohesion shear strength parameter is reviewed. For slope stability analyses, it is recommended that the shear strength be modeled using a stress dependent failure envelope or a friction angle that corresponds to the average effective normal stress acting on the slip surface passing through that particular material instead of using a combination of cohesion and friction angle to represent soil shear strength. Other recommendations for stability analyses include using an effective stress cohesion of zero for residual and fully softened strength situations. To facilitate selection of shear strength parameters for landslide analyses, empirical relationships for the drained residual and fully softened strengths are updated from the previous empirical relationships presented by Stark and Eid. Finally, the paper presents torsional ring shear test results that indicate that pre-existing shear surfaces exhibit self-healing that results in increased shear resistance. The magnitude of healing appears to increase with increasing soil plasticity, and this increase could have implications for the size, timing, and cost of landslide remediation.