Sand cushions for passive protection structures could reduce the damage that is induced by rockfall impact. Therefore, evaluation of the peak impact force generated by rockfall on the sand cushion is significant to the design of passive protection structures. This study aims to estimate the peak impact force using the elastoplastic linear strengthening model when a rockfall hits the sand cushion. Impact tests were conducted to study the effect of rockfall mass, impact velocity, and cushion thickness on the rockfall impact force. The experimental results indicate that the decreasing rockfall mass, impact velocity, and increasing cushion thickness could decrease the impact force of rockfalls. The sensitivity analysis results show that the main factor that influences the peak impact force is impact velocity, followed by rockfall mass and cushion thickness. In addition, the calculation method for the peak impact force and penetration depth of rockfall was proposed by the elastoplastic linear strengthening model. The impact force-deformation curves of this model were provided and discussed. The relationship between the strengthening coefficient and influencing factors was established. In addition, the simulation results indicate that the elastoplastic linear strengthening model showed good reliability when estimating the impact force compared with the five classical models. The strengthening coefficient of other cushion materials needs to be calibrated.

Ground reinforced embankment (GRE) is a common and efficient rockfall mitigation measure. However, due to the diversity of geometric dimensions and composite components of the embankments worldwide, the design methods have not yet been unified. This article proposes a DEM-based framework for modeling the GREs impacted by rockfalls, and to optimize the structural design by comparing the block-intercepting performance. The numerical model based on MatDEM is validated by restoring the Peila's field tests, and the simulated materials are calibrated by comparing the laboratory test results. The design elements can be determined through simulated impact tests, with the site topography and rockfall trajectory as prerequisite information. The simulation test results show that the structural positions and cross-sectional shapes alter the interaction between rockfalls and embankments, thereby affecting the block-intercepting capacity. Under the impact of high-energy blocks, the characteristic of structural failure is that the extrusion of the downhill face is greater than the displacement of the uphill face, which can be used as a criteria to determine the reasonable design elements. The proposed framework can be applied to an actual site and maximize the cost-benefit performance of design depending on the site space and budget conditions.

Reinforced concrete (RC) sheds with sand cushions laying on the top are commonly adopted to resist rockfall impacts. To improve the rockfall-impact resistance of RC shed with sand cushion, this study investigated the buffering performance of sand cushion and examined the effect of sand cushion on the dynamic behaviors of RC shed. Firstly, a series of impact tests on sand cushion were conducted to analyze the influence of cushion thickness and falling height of rockfall on the penetration depth into the cushion, impact force and impact duration, as well as the development of vertical and horizontal stresses inside the cushion. Then, a finite elementdiscrete element coupling model was established to consider the particle interaction of sand cushion under rockfall impacts and impact behaviors of RC shed. Finally, based on the validated numerical analysis method, the effect of sand cushion on the dynamic responses and damage of prototype RC shed subjected to the impact of rockfall was simulated and evaluated. The results showed that: (i) with the increase of cushion thickness, the peak impact force was reduced, but the penetration depth and duration increased; as the falling height elevated, the impact force and penetration depth increased while the duration was shortened; (ii) sand cushion had excellent buffering performance to attenuate vertical and horizontal stresses inside the cushion; (iii) stress diffusion angle formed in the sand cushion can enlarge the load-bearing area at the bottom of the cushion, and the buffering performance of sand cushion can be improved through increasing the stress diffusion angle; (iv) compared with the non-cushion one, the rockfall-impact resistance of RC shed was effectively improved by the sand cushion through reducing impact force, penetration depth, dynamic bending moment and shear force of the shed roof, as well as transforming brittle punching-shear failure of the shed roof into flexural failure.

This paper presents a new design numerical tool for geosynthetic-reinforced soil embankments, used to mitigate rockfall risk in scenarios of large volumes, energies, and multiple block failures. The model can simulate both local block penetration into the uphill embankment face and extrusion mechanism frequently affecting the downhill face. The new model is based on an existing elastic-visco-plastic model, originally developed to simulate impacts of blocks on homogeneous granular strata. The model has been enhanced and modified by incorporating a plastic mechanism, accounting for the extrusion process potentially occurring within the embankment body. The model is initially described and then validated using available in situ real-scale test data; finally, the results of a parametric study, examining the influence of the main controlling parameters and the applicability of the tool for pre-design purposes, are illustrated.

The 2022 Paktika earthquake (moment magnitude: 6.2) occurred on June 22, 2022, near the border between the Khost and Paktika Provinces of Afghanistan, causing heavy damage and casualties in Paktika Province. This study evaluated the crustal deformation and associated strong motions induced by the Paktika earthquake. Crustal deformations were determined using the Differential Interferometric Synthetic Aperture Radar (DInSAR) technique and three-dimensional finite element method (3DFEM) and the results were compared. The permanent ground displacements obtained from the DInSAR and 3D-FEM analyses were similar in terms of amplitude and areal distribution. Strong motions were estimated using the 3D-FEM with and without considering regional topography. The estimations of maximum ground acceleration, velocity, and permanent ground deformations were compared among each other as well as with those inferred from failures of some simple structures in the Spera and Gayan districts. The inferred maximum ground acceleration and velocity from the failed adobe structures were more than 300 Gal and 50 cm/s, respectively, nearly consistent with the estimates obtained using empirical methods. The empirical method yielded a maximum ground acceleration of 347 Gal, whereas the maximum ground velocity was approximately 50 cm/s. In light of these findings, some surface expressions of crustal deformations and strong ground motions, such as failures of soil and rock slopes and rockfalls, have been presented. The rock slope failures in the epicentral area were consistent with those observed during various earthquakes in Afghanistan and worldwide.

Ground reinforced embankment (GRE) is an economical and efficient protection measure against rockfalls. In various design guidelines of ground reinforced embankments, the impact force of the rockfall is the principal factor, which is significantly affected by rockfall shape. This article conducts real scale tests and numerical tests to observe the external deformation behavior and the internal dynamic response of GREs subjected to lateral impact. Five shapes of the rockfalls corresponding to three contact types are set up in the tests. The experimental results show that the impact surface shapes of the rockfalls govern the penetration deformation patterns of the embankments, and the deformation extent of the disturbed soils. For different contact types between rockfalls and construction materials, the failure mode of the geosynthetics and the displacement distribution of the disturbed soils are distinguishing. The disturbed soils can be divided into two parts, the part surrounds the rockfall mainly expands laterally, and the rest is extruded and slips backward. Basically, the sharpness of the rockfall results in the deeper penetration and the smaller impact force. The influence of the rockfall shape needs to be carefully considered in the design of ground reinforced embankments.

Natural hazard processes, as an inherent component of mountain environments, react sensitively to global warming. The main drivers of these changes are alterations in the amount, intensity or type of precipitation, glacier melting, or thawing of permafrost ice. The hazard responses can involve a change in hazard intensity or frequency (increasing or decreasing), a shift in their location or, a shift from one type of hazard to another. As climate change impacts vary in space and time, this variability must be considered when planning measures to protect populations and infrastructure from hazardous processes. To support this, we developed a method for assessing the climate sensitivity of small individual rock releases and larger rockfall processes. The method is based on a fuzzy logic approach and uses highly resolved climate scenario data, allowing application on a regional or even larger scale. The application in a study area of 700 km2 in the central Valais (Switzerland) shows that the impacts of climate change on natural hazard processes can vary quite substantially across small spatial scales. Generally, an increase in rockfall frequency and magnitude is simulated under future warming scenarios, especially at higher altitudes. However, at lower elevations and on south-exposed slopes, a decrease in freeze-thaw cycles leads to a decrease in material availability. This knowledge is essential in discussions of how climate change should be considered in hazard and disaster management.

The distribution of freezing and thawing within rock masses is time varying (day to day or season to season) and controls the effectiveness of the frost cracking processes from the surface until various depths. These processes are major contributors to the development of rock instabilities. By altering the thermal regime of rockwalls, global warming could have a major impact on rockfall dynamic by the end of the 21st century. This study seeks to improve our understanding of the influence of this warming on (i) the distribution of freezing and thawing within rock masses, (ii) the effectiveness of frost cracking and (iii) the frequency and magnitude of rockfalls. Thermistor sensors inserted in a 5.5-m horizontal borehole and a weather station were installed on a vertical rockwall located in the northern Gasp & eacute; Peninsula (Canada). This instrumentation was used to calculate the surface energy balance of the rockwall and to measure and model its thermal regime at depth over a period of 28 months. Combining locally recorded historical air temperature data with simulated future data (scenarios RCP4.5 and RCP8.5) made it possible to extend the rockwall thermal regime model over the period 1950-2100. The effectiveness of frost cracking over this 150-year period has been quantified using a thermomechanical model. Depending on the scenario, warming of 3.3 degrees C to 6.2 degrees C is expected on the northern Gasp & eacute; Peninsula by the end of the 21st century. This rapid warming is likely to decrease the maximum depth reaches by the seasonal frost by 1-2 m and shorten its duration by 1-3 months. The frequency of freeze-thaw cycles could increase twelvefold in January. Frost cracking effectiveness should intensify around 70 cm in depth and disappear beyond that (RCP4.5) or diminish starting at 10 cm in depth (RCP8.5). In areas subject to seasonal freeze-thaw cycles, decimetric rockfall frequency could grow considerably in winter but be significantly reduced in fall and spring. Furthermore, frost cracking would cease contributing to the development of larger magnitude instabilities. Depending on the scenario, warming of 3.3 degrees C (RCP4.5) to 6.2 degrees C (RCP8.5) is expected on the northern Gasp & eacute; Peninsula by the end of the 21st century. By altering the thermal regime of rockwalls, the global warming could have a major impact on rockfall dynamic. In regions subject to seasonal freeze-thaw cycles, small magnitude rockfall frequency could grow considerably in winter but be significantly reduced in fall and spring. Frost weathering would cease contributing to the development of larger magnitude instabilities. image

The pile-anchor structure is widely used in slope/landslide reinforcement, and is also applicable to debris flow and rockfall barriers in mountainous areas. However, the impact behavior of this structure has not been studied. To promote the use of this retaining structure in the prevention of slope geological disasters, this study investigated the dynamic responses and impact behavior of pile-anchor structures through a set of impact experiments, wherein dry granular materials with different particle size and sliding blocks with different masses were adopted to simulate different impact loading scenarios of granular flow and rockfall. The impact pressure on the pile-anchor structure, the seismic signals induced inside the slope during the sliding and impact processes, and the deformation characteristics and failure modes of the piles and anchors were systematically investigated. The results indicate that the peak impact force and intensity of the seismic signal are affected by the particle size of the impact granular materials. As the impact loading of sliding blocks increased, the tensile force of the anchor increased nonlinearly, the distribution pattern of the pile's impact dynamic moment changed, and anchor prestress loss was observed. The preliminary results obtained by this study are expected to provide the theoretical basis for designing relevant barriers in areas prone to debris flow and rockfall, and promote the inclusivity of the impact behavior of slope retaining structures in existing design codes pertaining to retaining structures.

On February 6, 2023, two significant earthquakes with magnitudes (Mw) of 7.7 and 7.6 struck Turkey, occurring nine hours apart. In addition to the tragic loss of over 50,000 lives in the earthquakes centered in Kahramanmaras,, hundreds of thousands of engineering structures, such as residences, schools, hospitals, historical landmarks, highways, and more, were severely damaged. This study assesses the damages and risk scenario following the Kahramanmaras, earthquakes concerning Siverek Castle. In addition, remediation and strengthening proposals, required to eliminate the damage and the possible risk, have been developed. The initial stage involved observational damage assessments on the castle and surrounding slopes as part of field studies, identifying five different types of damage and potential risks. Subsequently, a precise 3D digital model of the damaged castle and its slopes was generated using the digital photogrammetry method. Additionally, geological and geophysical studies were conducted in the field to determine the characteristics of the mound structure, historical castle walls, soil and rock on the slope. Non-destructive, geophysical methods consisting Vertical Electrical Sounding (VES), Seismic Refraction Method (SRM) and Multichannel Analysis of Surface Waves (MASW) measurements were specifically employed in the area with historical remnants. To verify the obtained data, five boreholes were drilled in the lower parts of the slope, and experimental studies were conducted to determine the soil and rock material properties of the slope. In the numerical studies, a total of 54 2D stability analyses were performed under static, long-term static, and dynamic conditions. Additionally, 1000 different probabilistic rockfall analyses were conducted, both in 2D and 3D, to calculate the run-out distance, bounce height, velocity, and kinetic energies of the blocks that fell or were about to fall during the earthquake. In the final stage of the study, remediation and strengthening recommendations were prepared for the strengthening of the fortification walls and slopes where failures occurred, and stability analyses were conducted. Consequently, a design proposal recommending five distinct approaches to remediate and strengthen the castle and slopes impacted by the Kahramanmaras, earthquakes was endorsed by the relevant authorities, and construction has commenced. When the remediation and strengthening works are completed, the security of the cultural heritage will be ensured, and it is planned to be opened to visitors.