Vladimir Greif

Monitoring of post-failure landslide deformation by the PS-InSAR technique at Lubietova in Central Slovakia

Interferometric synthetic aperture radar data from ERS and ENVISAT sensors were utilized in the analysis of the post-failure deformations in the area of Lubietova town in Central Slovakia. The catastrophic landslide of 1977 together with surrounding landslides in the Lubietova area were analysed with the help of persistent scatterers (PS) technique in order to evaluate recent and past deformations of the unstable slopes. Although long-term precise geodetic monitoring of the 1977 landslide revealed differential deformations inside the sliding mass, due to the lack of the PS located inside the landside caused by temporal decorrelation, unfortunately, these records could not be directly compared. The adjacent landslides with sufficient number of PS were analysed by transformation of the line of sight displacements recorded by the sensors to the slope vector direction. This procedure allowed identification of the precise boundaries of the actively moving landslide parts and the updating of the landslide inventory for the Lubietova area.

Application of the PS-InSAR Technique for the Post-Failure Landslide Deformation Monitoring at Lubietova Site in Central Slovakia

The interferometric synthetic aperture radar data from ERS and ENVISAT sensors were utilized in the analysis of the post-failure deformations in the area of Lubietova town in Central Slovakia. The catastrophic landslide of 1977 together with surrounding landslides in the Lubietova area were analysed with the help of persistent scatterers (PS) technique in order to evaluate recent and past deformations of the unstable slopes. Although long-term precise geodetic monitoring of the 1977 landslide revealed differential deformations inside the sliding mass, due to the lack of the PS located inside the landside caused by temporal decorrelation, unfortunately these records could not be directly compared. The adjacent landslides with sufficient number of PS were analysed by transformation of the line of sight displacements recorded by the sensors to the slope vector direction. This procedure allowed identification of the precise boundaries of the actively moving landslide parts and the updating of the landslide inventory for the Lubietova area.

Model for Cuboid Shape Samples and its Analysis Used for Measurements of Thermophysical Properties of Sandstone

Model for Cuboid Shape Samples and its Analysis Used for Measurements of Thermophysical Properties of Sandstone A new model for the sample of square cross section with cuboid geometry including the effect of heat loss from the surface of the sample was tested using the theory of sensitivity coefficients. Theoretical calculation of model uncertainty and derived analytical formulas are presented. Results of the uncertainty analysis set out the range of experimental conditions under which the model is valid and the uncertainty of estimated parameters is low. Propagation of error for non-stochastic dynamic measurements based on the sensitivity coefficients shows limitations related to a range of model validity. The analysis improves the accuracy of measurements. The model was used for data evaluation of thermophysical parameters measured on the sandstone from the locality Pravčická brána. Evaluation procedure was tested on experimental data measured under different experimental conditions. In conclusion, the discussion of the experiment optimization is presented.

Physical Model of the Mechanism for Thermal Wedging Failure in Rocks

Cyclic diurnal and annual temperature variations acting upon rocks are rarely considered among triggers of slope movements. The importance of temperature change is viewed mainly as a precursor of failures, where the triggers are rainfall or seismic activity. This paper aims to determine the limit conditions in which plastic deformation develops in a situation where one or more blocks fallen into an open crack create a wedge, causing non-elastic displacement of a block resting on an inclined plane. A physical model was prepared to study this phenomenon in a thermal dilatometer, in which the displacements were measured using linear variable differential transformer (LVDT) sensors for blocks with different block/wedge ratios, while temperature was varied in a controlled manner. Nine physical models of sandstone blocks were tested over a cyclic temperature change of ΔT = 35 °C while measuring the permanent displacements of a block in order to confirm the existence of this type of failure mechanism. Further, a series of cyclic tests were performed on all nine physical models to determine the threshold temperature change at which plastic deformation occurs for different block/wedge ratios. Results showed plastic deformation resulting from a cyclic wedging mechanism for a block/wedge ratio 0.5 and total model size of 50 mm, reaching a permanent displacement of 4.23 × 10−3 mm for a block resting on an inclined plane with a slope of 7°. For these conditions, a temperature change which caused permanent block displacement by thermal wedging was as low as 6 °C. The results of the physical model are in agreement with a proposed analytical solution by Pasten (2013) and measurements of Bakun-Mazor et al. (2013) at a site at Masada, Israel.

Deformations Dynamics in Response to Seasonal Temperature Oscillations: An Example from Pravcicka Brana Rock Arch (Czech Republic)

The paper discusses the results of the research devoted to the preservation of natural heritage site carried out at Pravcicka Brana Rock Arch located in Bohemian Switzerland National Park, Czech Republic., the largest natural sandstone bridge in Europe. The aim of the study was laid on the relationship between spatial temperature distribution and rate of displacement, as the response to temperature oscillations and to find out kinematic behaviour (deformations dynamics) of the rock arch using computer modeling to simulate if there exists any potential hazard to sandstone body rock arch to collapse.

Rock Deformation Monitoring at Cultural Heritage Sites in Slovakias

The article deals with a socially important topic — preservation of cultural heritage in Slovakia. Current results of an engineering geological investigation of five medieval castles, one of them under the patrimony of UNESCO (Spis Castle) located in different geotechnical and engineering geological conditions are discussed. The obtained results are based upon an investigation program sponsored by the Ministry of Environment in which about 40 most prominent medieval castles or castle ruins have been investigated with the aim to recommend the remedial measures and thus to prevent their gradual disintegration. A following project focused on monitoring of the selected castle rocks showing instability problems was later carried out.

Kinematic Analysis of a Rock Slope at Strecno Castle (Slovakia) Based on the Processing of the Point Cloud Generated by UAV Photogrammetry

Open image in new window The Strecno Castle (northern Slovakia) stands upon rock cliff formed by Triassic dolomite-limestone rocks which are in overthrusted position. At the toe of the castle rock in relatively narrow area the Vah River, international railway and the primary international road with large volume of traffic is running. Due to extreme morphology formed by almost vertical slopes with several overhangs, lithological composition, tectonic setting and the high degree of weathering, the rock mass is in critical state of stability. Following this situation and having in mind one causality from 2008 when one person in car was killed by the falling rock block, the Ministry of the Environment initiated the programme covering detailed engineering geological investigation including elaboration of kinematic analysis of the rock slope based on the high density point cloud data generated by UAV photogrammetry to delineate potentially unstable parts in the rock slope. The authors describe the procedure of identifying critical structural data sets delineating potentially unstable rock blocks, type of down fall movement and rock fall trajectories. This, along with detailed stability calculation of the critical rock blocks serves as powerful tool to recommend mitigation measures needed to secure the international road and the castle, as well.

Stone pillar rockfall in Danxia landform area, Mt. Langshan, Hunan Province, China

Abstract A typical Danxia stone pillar, Leipishi I, in the World Natural Heritage site at Mt. Langshan, China, collapsed on 2 November 2009. To understand the mechanism controlling this rockfall event, uniaxial compressive strength, tensile strength, resistance against sulfuric acid, and freezing and thawing properties were analyzed from 44 sandstone and conglomerate cores collected from the Lanlong Formation, the only exposed formation on Mt. Langshan. In addition, four rock slices were created for analysis under a polarizing microscope. A detailed reconstruction of the geometry and restraint conditions of the stone pillar in place before the rockfall occurred permitted an estimation of the stress state before collapse using 3D finite-element code. The results show that the rapid retreat of soft, intercalated rock layers due to weathering can profoundly change the stress state within the rock body, causing compressive or tensile stresses to rise above compressive or tensile strengths in specific sections of a rock body, and causing partial or complete collapse.

Monitoring of the Thermal-Moisture Regime at St. Jacob´s Church in Levoča UNESCO Site, Eastern Slovakia

The paper deals with the monitoring of thermal-moisture regime, as one of the deterioration factors within the rock material at UNESCO historic site, particularly in the supporting pillars of St. Jacobs’s church in Levoca, Eastern Slovakia. The moisture sensor consists of a small cylinder having the diameter and length of 20 mm in which a small ball of 2 mm diameter is placed that delivers the heat in step-wise regime and simultaneously measures temperature. Two sensors have been positioned in South-North orientation and embedded in the church supporting pillars. During monitoring we have identified diffusion of moisture associated with cycle day/night and cycle wetting/drying caused by meteorological precipitation.

Gypsum Decay Simulation: Risco de las Cuevas Case Study, Madrid, Spain

Since troglodyte population has excavated their dwellings in the gypsum escarpment of the Risco de las Cuevas of Perales de Tajuna (Spain), atmospheric processes have preferentially sculptured the rockwall. This weathering has a negative effect on the future of the monument, and to preserve it, it is important to investigate how the different content of clay in the gypsum that constitute the escarpment, respond to the weathering. Three types of gypsum, with different amounts of clay, material that constitute El Risco de las Cuevas, were subjected to accelerated ageing tests in laboratory (freezing/thawing and wetting/drying). In addition to laboratory observations, results from field observations and digital photogrammetry were obtained, serving to draw the geometry of the escarpment, comparing with old photographs, taken by neighbors of the village of Perales de Tajuna, in which images of the detached tape bock of gypsum can be seen, their dimensions and volume. All artificial accelerated ageing tests have leaded to gypsum caused decay, being the most aggressive the resistance to freezing in the gypsum specimens with the highest clay content.