Jan Blahůt

Rock slopes are dynamic geomorphic systems whose stability is influenced by an interplay between geological structures and environmental forcing. Among these, meteorological variables, particularly temperature and precipitation, are recognised as key drivers of both long-term slope evolution and short to medium-term joint deformation expressed through diurnal and annual displacement cycles. However, their influence on block scale displacement remains poorly explored. This study investigates meteorologically driven rock slope surficial dynamics using high-resolution crack meter measurements of blocks ranging in volume from 0.3 to 150 m³ and environmental monitoring data collected from four instrumented sites in Czechia, Central Europe. Each site comprises unique geological and morphological conditions and is equipped with joint displacement sensors, a weather station, and an in-depth thermal probe. A total of twelve representative rock blocks were monitored across the sites, capturing both thermally driven and potentially gravitationally induced displacements. We analysed multi-year time series data (≥2 years) to assess the relationships between joint movements and meteorological variables, including air temperature, in-depth rock temperature up to 3 m and rainfall. Statistical observations revealed distinct seasonal and diurnal cycles in joint dilation linked to thermal forcing. Moreover, several blocks exhibited signs of compound kinematics, with joint displacements influenced by thermal cycles, rainfall and irreversible gravitational destabilisation trends. This study provides new insights into the temporal dynamics of rock slope instability in temperate climates. The observed thermal sensitivity highlights the importance of temperature variations in driving short-term reversible joint deformation and potentially contributing to progressive rock-slope destabilization. This study demonstrates the value of long-term, high-frequency monitoring for quantifying weather–rock mass interactions and supports the integration of kinematical interpretations into future monitoring system designs.

Rock slopes are dynamic geomorphic systems whose stability is influenced by an interplay between geological structures and environmental forcing. Among these, meteorological variables, particularly temperature and precipitation, are recognised as key drivers of both long-term slope evolution and short to medium-term joint deformation expressed through diurnal and annual displacement cycles. However, their influence on block scale displacement remains poorly explored. This study investigates meteorologically driven rock slope surficial dynamics using high-resolution crack meter measurements of blocks ranging in volume from 0.3 to 150 m³ and environmental monitoring data collected from four instrumented sites in Czechia, Central Europe. Each site comprises unique geological and morphological conditions and is equipped with joint displacement sensors, a weather station, and an in-depth thermal probe. A total of twelve representative rock blocks were monitored across the sites, capturing both thermally driven and potentially gravitationally induced displacements. We analysed multi-year time series data (≥2 years) to assess the relationships between joint movements and meteorological variables, including air temperature, in-depth rock temperature up to 3 m and rainfall. Statistical observations revealed distinct seasonal and diurnal cycles in joint dilation linked to thermal forcing. Moreover, several blocks exhibited signs of compound kinematics, with joint displacements influenced by thermal cycles, rainfall and irreversible gravitational destabilisation trends. This study provides new insights into the temporal dynamics of rock slope instability in temperate climates. The observed thermal sensitivity highlights the importance of temperature variations in driving short-term reversible joint deformation and potentially contributing to progressive rock-slope destabilization. This study demonstrates the value of long-term, high-frequency monitoring for quantifying weather–rock mass interactions and supports the integration of kinematical interpretations into future monitoring system designs.

Rock slopes are dynamic geomorphic systems whose stability is influenced by an interplay between geological structures and environmental forcing. Among these, meteorological variables, particularly temperature and precipitation, are recognised as key drivers of both long-term slope evolution and short to medium-term joint deformation expressed through diurnal and annual displacement cycles. However, their influence on block scale displacement remains poorly explored. This study investigates meteorologically driven rock slope surficial dynamics using high-resolution crack meter measurements of blocks ranging in volume from 0.3 to 150 m3 and environmental monitoring data collected from four instrumented sites in Czechia, Central Europe. Each site comprises unique geological and morphological conditions and is equipped with joint displacement sensors, a weather station, and an in-depth thermal probe. A total of twelve representative rock blocks were monitored across the sites, capturing both thermally driven and potentially gravitationally induced displacements. We analysed multi-year time series data (≥2 years) to assess the relationships between joint movements and meteorological variables, including air temperature, in-depth rock temperature up to 3 m and rainfall. Statistical observations revealed distinct seasonal and diurnal cycles in joint dilation linked to thermal forcing. Moreover, several blocks exhibited signs of compound kinematics, with joint displacements influenced by thermal cycles, rainfall and irreversible gravitational destabilisation trends. This study provides new insights into the temporal dynamics of rock slope instability in temperate climates. The observed thermal sensitivity highlights the importance of temperature variations in driving short-term reversible joint deformation and potentially contributing to progressive rock-slope destabilization. This study demonstrates the value of long-term, high-frequency monitoring for quantifying weather–rock mass interactions and supports the integration of kinematical interpretations into future monitoring system designs.

The effects of high temperature on the tensile strength and physical properties of rocks were investigated using furnace heating and simulated fire treatments. Four rock types—basalt, granite, limestone, and sandstone—were examined under dry, wet, and saturated conditions (0%, 50–60%, and 100% water content, respectively). Tensile strength was measured before and after heating using the Brazilian test, while changes in porosity, thermal conductivity, mass, and P- and S-wave velocities were also evaluated. Thermal measurements indicate that both heating methods reached maximum temperatures of approximately 600 °C and produced comparable effects on rock properties. Initial water content had a negligible influence on post-treatment tensile strength and physical properties. In contrast, rock lithology strongly controlled the degree of thermal damage. Basalt, characterized by high initial tensile strength, exhibited minor reductions in tensile strength and wave velocities, whereas sandstone showed greater degradation. Granite and limestone exhibited pronounced reductions in P- and S-wave velocities. Rocks with higher thermal conductivity, such as sandstone, experienced larger decreases in thermal conductivity after heating, while basalt showed the smallest change. Conversely, basalt exhibited the greatest increases in porosity and mass loss. Overall, rock lithology and initial mechanical strength are the primary factors governing rock degradation under high-temperature exposure.

Our research investigates the complex thermo-mechanical coupling within landslide shear zones, specifically focusing on how temperature variations influence the residual shear strength of clayey soils. This parameter is a critical determinant for the stability of reactivated, slow-moving landslides.In our laboratory investigations, we utilised a modified ring-shear apparatus equipped with a temperature-control system to conduct heating-cooling cycles (typically between 20 °C and 70 °C) on various soil samples. We have tested materials ranging from low-plasticity mountain soils to high-plasticity marls and bentonites. Our findings reveal that the thermal response of soil is sensitive to both mineral composition and rate of shearing.Regarding slope modelling, we developed numerical frameworks, utilising finite-element analysis, that incorporate temperature-dependent failure criteria. By simulating scenarios from the 1960s to the 2060s based on historical and projected climate data, our results suggest that gradual ground warming may increase the factor of safety in certain clay-rich slopes, potentially transitioning active landslides into long-term dormancy. We also quantified the nonlinear coupling between temperature variations and groundwater table fluctuations, demonstrating that their combined impact on stability is more significant than the sum of their individual effects.Our field monitoring and regional activities involved extensive sampling at disaster-prone sites and the calibration of thermal parameters using historical meteorological data to accurately reproduce ground temperature profiles. Furthermore, we have implemented spatial probability analyses at a national scale, utilising soil composition and topographic data to map expected changes in slope stability under global warming scenarios.In the future, we plan to incorporate the soil-vegetation-atmosphere nexus into our framework. By evaluating how vegetation and root systems modulate heat and moisture fluxes, we should be able to capture the thermo-mechanical behaviour of the shallow subsurface more accurately. Additionally, we intend to expand our experimental investigations to a broader range of soil compositions and refine testing protocols to objectively assess the thermal sensitivity of landslide-prone formations.

Temperature fluctuations can influence the internal stress field of a rock mass, especially in its surficial layer. Inherent properties (mineral composition, porosity, and fracturing) and external forcing (air temperature, humidity, and solar radiation) control the heat flux and temperature within the rock. Long-term thermal forcing, particularly when combined with wetting-drying cycles, can exacerbate rock deterioration and weathering, leading to progressive changes in mechanical properties, as shown by laboratory experiments.In this study, granodiorite samples from the Požáry field laboratory (Central Czechia) were subjected to thermal cycling in a controlled environment of a climate chamber, with repeated and increasing cycles reaching 80°C, a temperature that was most probably never reached after the rock´s formation. During the cycling, repeated UPV measurements were made (P and S waves) to observe the changes in their velocity and the inferred dynamic elastic moduli.The results showed slow but progressive decrease in the P and S wave velocities, suggesting rock damage after only a few cycles. This indicates possible increased rock wear in case of an expected future temperature rise.

Rockfalls and slides pose significant hazards in open-pit mines; however, widely adopted tools for non-contact geomaterial characterisation and slope monitoring are still lacking.This study investigates the application of unmanned aerial vehicle-mounted thermal infrared cameras (UAV-IRT) for observing, detecting, and inferring material parameters in active surface mining environments. A multitemporal UAV‑IRT campaign was conducted to acquire thermal imagery across the full diurnal temperature range, from daily maxima to minima. Results from the thermal images collected at the Jezeří open-pit mine in Czechia showed that cooling indices can be used to estimate material properties, such as porosity, demonstrating strong potential for integration into geotechnical slope-design systems.On the one hand, the analysis also highlights limitations, particularly when target features receive intense solar radiation, which can reduce the reliability of parameter detection. On the other hand, UAV-based infrared thermography is shown to be a practical tool for characterising surface materials in areas affected by mass wasting—a step toward the development of automated material‑parameter detection algorithms, applicable to both artificial and natural slopes, with the overarching goal of improving safety.

On 2 ^nd June 2010, heavy rainfall triggered a significant debris flow on the southern slope of Lemešná Mountain in the Javorníky Range (Outer Western Carpathians), Czech Republic. Multidisciplinary research was carried out there, including geomorphological survey, electrical resistivity tomography, laser scanning, soil and rainfall analysis. The debris flow occurred after the prolonged convective and intense rainfall. The antecedent precipitation index calculated for the previous 30 days reached 134.1 mm and the daily rainfall 37.4 mm, 13 times higher than the long-term average daily rainfall. The debris flow occurred in unconsolidated flysch sediments and caused minor damages. The locality was affected by slope movements in the past, as evidenced by two debris flow deposit cones in the valley. Electrical resistivity tomography revealed a sliding surface at a depth of 5 m and another at 15–20 m. However, according to local residents and the forest manager, no mass movement has been recorded in there in the last 40 years. Human intervention, particularly artificial drainage and deforestation, could also have contributed to the debris-flow triggering. The aim of this work was a complex analysis of the triggering conditions of the debris flow and a risk assessment of new events in this area.