Slope Processes Research Articles

Dynamic response and failure process of horizontal-layered fractured structure rock slope under strong earthquake

Dynamic response and failure process of horizontal-layered fractured structure rock slope under strong earthquake

Study on thermal‐hydro‐mechanical coupling and stability evolution of loess slope during freeze–thaw process

AbstractDisasters occurring at loess slopes in seasonal frozen regions are closely related to changes in the thermo‐hydro‐mechanical (THM) state in loess by freeze–thaw (FT) action. Current research on FT‐induced soil slope failure focuses on frozen stagnant water effects, while the intrinsic connection between the FT‐induced stagnant water effect and soil strength deterioration remains unclear. In this study, by taking the FT‐induced loess slope failure as an example, field surveys, boreholes, exploratory wells, and 3D topographic mapping were used to reveal the landslide features and stratigraphic information; Furthermore, the temporal and spatial variation of water and heat in loess slope was revealed by on‐site monitoring data; A THM coupled model of frozen soil was established using COMSOL Multiphysics simulation software to reconstruct the frozen stagnant water process of shallow loess slope, as well as the influence of THM field on loess landslide. The results show that the effects of FT in the seasonally frozen region occurred in the shallow layer of the loess slope. The water‐ice phase transition during FT process broke the phase equilibrium of loess. Numerical calculations and field monitoring indicated a continuous migration of water to the freezing front, creating a water‐enriched zone inside the loess. Both the impact of the frozen stagnant water and changes in the stress field led to the degradation of loess structure and reduced the strength properties, thus threatening the stability of the loess slope. The study results can contribute to an in‐depth understanding of the mechanism underlying FT loess landslides in seasonal frozen regions, and provide a scientific basis for the evaluation and prevention of FT landslides.

Initiation mechanism of shallow loess slope sliding under coupling effect of train vibration and rainfall

The large-scale construction and operation of the railway in Northwestern China has resulted in some geological disasters in recent times. Among them, the shallow sliding of the loess railway slope caused by the coupling effect of train vibration and rainfall has been a frequent occurrence, causing heavy losses of life and property. Accordingly, this is a major problem an needs an urgent solution. Therefore, this study used acceleration, pressure, moisture, and displacement monitoring equipment, among others, to conduct physical simulation experiments and theoretical analysis on the instability and sliding process of loess railway slopes under the coupling effect of train vibration and rainfall. The research results indicate that acceleration gradually decreases downward along the slope, and the pore water pressure and volumetric water content increase with the increase in rainfall infiltration. The slope displacement exhibits a phased increase after the initial slip. As vibration energy builds up, the slope bottom undergoes rapid structural damage and tensile shear coupled instability failure, followed by slip. Before sliding, both the crack density and fractal dimension of the slope have an active area, that is, a sliding slope area, which continues to expand upward under the cumulative effect of vibration energy. The failure process is divided into three stages according to the changes in macrodeformation, pressure, water content, displacement, and fractal dimension of the slope model: crack development stage, local liquefaction sliding stage, and slip propagation stage. This research elucidates the initiation mechanism of loess railway slope sliding under the coupling effect of train vibration and rainfall and provides a theoretical basis for predicting loess slope disasters under train vibration and providing adequate warning.

Hydrological processes in the megadune slopes and their implications for the water source of lakes in the Badain Jaran Desert

To elucidate the slope hydrology and their influence on the regional water balance and desert lake development, water migration and soil water conditions were studied in the megadunes of Badain Jaran Desert. Simulated rainfall of 15–60 mm with infiltration depths of ∼ 0.3–0.5 m, the lateral water migration ratios of ∼ 52.9 %-86.2 % and the differential distribution of tracers with depth in the flat sand lands indicate that 15 mm rainfall is the critical rainfall for effective recharge of deep soil water and that there is a shift from piston flow to preferential flow of water during infiltration. Soil micro-bedding and 4.2 % soil gravity water from locally wet surface soils and 6 mm of natural rainfall resulted in lateral migration of the tracer ∼ 1.2 m and 0.4 m in the slope surface and soil respectively, indicate surface flow and lateral gravity water flow resulting from differences in hydraulic conductivity and water-holding capacity of the soil micro-bedding. Soil water storage at 0–4 m depth showed that the bottom of the slope was ∼ 30 mm higher than the middle of the slope after the rainy season and ∼ 9 mm higher before the rainy season; in general the post-rainy season was ∼ 30–40 mm higher than the pre-rainy season. Surface flow and lateral gravity water flow in unsaturated soils increase the intensity of lateral water movement on the slope and improve the effective conversion rate of rainfall to deep soil water, especially below 15 mm. Annual recharge of deep soil water, assessed using soil water change and critical rainfall, will not be less than 8.5 mm and may even reach an upper limit of ∼ 30–40 mm. The megadune slopes respond strongly to local precipitation, which is sufficient to maintain the lake, but extreme precipitation does not play a decisive role. The methods and results provided in this work can advance our understanding of the desert hydrological cycle and water resources.

A Case Study for Stability Analysis of a Toppling Bank Slope with Fault Fracture Zones Developed under the Action of Bridge Loads and Reservoir Water

The mountainous areas of Southwest China have the characteristics of valley deep-cutting, a large topographic gradient, complex geological structures, etc. With the development of infrastructure construction in the area, the construction of bridges across valleys has gradually increased, and the phenomenon of slope failure occurs more and more frequently. As the weak interlayer, the fault fracture zones have a significant influence on the geological structure and stability of slopes, while the complexity of the mechanism of the deformation and failure of slopes increases with the combination of the development of the fracture zones and toppling deformation. This paper took the toppling bank slope of bridge foundations developed with fault fracture zones in Lancang River as the research object. Through an on-site field survey and geological survey technologies, it identified the distribution range of the fracture zones on the bank slope and determined the characteristics of the rock mass in the fracture zones. A stability evaluation model for the bank slope of the bridge foundations was established using the limit equilibrium method and discrete element method. Based on the two-dimensional limit equilibrium analysis, the potential failure modes of the bank slope were explored, and the stability of the bank slope under bridge loads was calculated. Through the three-dimensional geological model of the bank slope, including the fracture zones and toppling bodies, the three-dimensional discrete element numerical simulation method was adopted to simulate and calculate the deformation and failure process of the bank slope under different bridge loads and working conditions. According to the calculation results, the influence of bridge loads and reservoir water on the stability of the bank slope was analyzed from the perspectives of displacement, plastic zone, stability coefficient, and other factors. The formation process of the plastic zone and the development of the sliding surface were revealed, the incentive mechanism of bridge loads and reservoir water on the deformation and failure of the bank slope was analyzed, and the influence of fault fracture zones on the stability of the bank slope and the development of toppling deformation was determined. The results indicate that the fault fracture zones are important geological structures that affect the deformation and failure of the bank slope as a weak interlayer. Under the influence of bridge loads and reservoir water, the stability of the bank slope is affected by the quality of the rock mass and the development of the fault fracture zones, resulting in the unmet need for safety requirements and maybe leading to instability. Based on the calculation results of the stability evaluation prediction model for the bridge foundation bank slope and the engineering geological conditions, the bridge scheme has been selected.

Estimation of the Rate of Slope Processes and Morphological Variability of Kilometer-Sized Impact Craters on the Moon

Estimation of the Rate of Slope Processes and Morphological Variability of Kilometer-Sized Impact Craters on the Moon

Reconstructing the Eemian to Middle Pleniglacial pedosedimentary evolution of the Baix loess–palaeosol sequence (Rhône Rift Valley, southern France) – basic chronostratigraphic framework and palaeosol characterisation

Abstract. Loess–palaeosol sequences (LPSs) are important archives of landscape evolution, recording alternating periods of geomorphic activity (dust deposition and slope processes) and landscape stability (soil formation). LPSs of the Rhône Rift Valley are located along a spatial climatic gradient from the mid-latitudes to the Mediterranean region. This position renders them extremely valuable archives for correlating LPSs in the European loess belt and the Mediterranean region. Despite this important function, Rhône Rift Valley LPSs have been little investigated. In this study, we aimed to narrow this knowledge gap, in a first step towards linking LPS-based mid-latitude and Mediterranean palaeoenvironmental reconstructions. We studied the ∼ 14 m thick Baix LPS located at the western edge of the Rhône Rift Valley near Valence. Here, we focus on the lower ∼ 7 m of the LPS, which comprises 12 of 19 soil horizons overall, and record regional palaeoenvironmental variations from the Eemian to the Middle Pleniglacial (∼ marine isotope stage (MIS) 5 to MIS 3). Our reconstruction is based on detailed field description, complemented by granulometry (10 cm vertical resolution), and micromorphological analyses. Luminescence screening of cut-out soil-sediment columns subsampled with ∼ 5 cm vertical resolution (126 subsamples over 7 m) provides a preliminary chronometry. The loess deposits of the Baix LPS are strongly calcareous and predominantly silty but also contain sandy and fine gravelly laminae typical of loess deposits subjected to slope-wash processes. From bottom to top, the investigated part shows three intensely pedogenised levels: (1) a basal sequence of reddish-brown Btg and Bt horizons of a thick Eemian Stagnic Luvisol (MIS 5e); (2) an early glacial yellowish-brown Bw horizon (MIS 5d-a); and (3) a yellowish-brown Bw horizon with large cone-shaped carbonate nodules in the associated underlying Bk horizon, interpreted as a truncated Middle Pleniglacial (MIS 3) Calcic Cambisol. The Baix LPS is in parts very similar to the Collias LPS ∼ 100 km further south but also exhibits differences, reflecting its position at the spatial climatic transition between the presently temperate and the Mediterranean zone.

Определение количественных значений параметров селепроявлений с использованием БПЛА

As part of the development of improving methods for integrated monitoring of dangerous riverbed and slope processes, the authors worked out options for using an unmanned aerial vehicle (UAV) and specialized software in order to improve the quality of materials for field surveys of mudslide sites. The reliability of the quantitative determination of the parameters of mudflows is an urgent problem in assessing the spatial and temporal changes in the parameters of mudflow channels. The purpose of this work is to quantify the dynamics of changes in the landscape of residential areas exposed to negative impacts by determining the quantitative values of morphometric parameters of the mudflow channel and the adjacent territory before and after the passage of the mudflow. In particular, the volumes of soil carried away by the flow, as well as the volume of sediments in different sections of the mudflow transit, were determined. By comparative analysis of the results of software processing of materials from the removal of problem areas of the mudflow channel by a quadcopter, the values of the volumes of carried away soil (4376 m3, at the site of destruction by the flow of the highway) and mudflow deposits (above – 4623 m3, and below – 1788 m3 of the highway bridge) were obtained. Such an information base is indispensable in solving the problems of ensuring the safety of settlements and economic facilities from the negative impact of mudflows.

Experimental study on the failure process and modes of loess spoil slope induced by rainfall and engineering disturbance.

In this paper, indoor model tests were conducted using image analysis, pore pressure, and displacement measurement methods to investigate the failure evolution process and modes of loess spoil slopes with various components under the influence of rainfall and artificial excavation. The results of the experiments reveal that, under the action of rainfall, there are two types of cracks-to-failure modes for pure loess spoil slopes. One involves the formation of a large gully through the dominant channel, while the other is characterized by step-by-step retreating soil damage between cracks. The failure exhibits three distinct stages, and after failure, the slope angle is relatively large (>45°). The process of rainfall-induced destruction affecting loess spoil containing 25% coarse-grained content similarly unfolds in three stages, ultimately resulting in the formation of a regional landslide. This landslide typically encompasses a broader damage range compared to pure loess spoil, albeit with a shallower depth of damage. After the landslide stops and stabilizes, a tiny slope (45°) is created (<45°). The excavation at the toe of the slope induces loess spoil damage in a progressive multi-stage receding manner. This study provides a reference and basis for disaster prevention and warning of spoiled ground in loess areas.

Modelling rock fracturing by a novel implicit continuous to discontinuous method

This research introduces a novel implicit continuous to discontinuous method to investigate the cross-scale failure process of discontinuous rock masses, including fine fracture creation, propagation, and rigid block contact. This method enables an intact rock to split and crush, with the local deformation/movement propagating rapidly throughout the whole system. The method was applied to investigate the progressive slope failure. The results revealed that the number of failure elements within the slope increased rapidly at the primary fracture stage. The upper part of the failure band gradually shifted upward and backward towards the slope crest, where several tension cracks were clearly visible. Additionally, the failed zone became wider as the homogeneity coefficient m increased. Furthermore, the factor of safety (FoS) increased as the growth stage of m progressed, but it reached a constant value when m exceeded 8, indicating that the material became relatively uniform. Interestingly, for slopes with varying elevation heights, the FoS decreased in a power function form as the ratio of the slope height to the width of the slope top surface increased. Overall, these findings shed light on developing the continuous-discontinuous computational model, with the application to study the progressive failure process of slopes.

Seafloor geomorphology of the northern Argentine continental slope at 40-41° S mapped from high-resolution bathymetry

The southern sector of the northern Argentine continental margin (NACM), extending from 40 to 41° S, corresponds to a previously unmapped area of the South Atlantic Ocean in term of high-resolution bathymetry. Newly acquired high resolution data in the slope sector of the NACM between 900 and 5000 m allowed us to carry out a geomorphological analysis by combining novel multibeam data with a very high-resolution 3D seismic-derived bathymetry. The resultant digital elevation model revealed the presence of a wide variety of seafloor features and allowed us to characterize them by a geomorphometric analysis. Along slope processes, produced by the interaction of contour currents with the seafloor, make up a large array of erosional and depositional elements on the slope, including a contourite terrace, scours, drift bodies and sediment waves, that as a whole form part of a Contourite Depositional System (CDS). Additionally, across slope processes are also present, and give origin to four deeply incised submarine canyons that intersect the CDS. Overall, this work reveals the geomorphological complexity of this sector of the NACM and serves as a reference point for further studies regarding the sedimentary processes and oceanographic dynamics acting in the continental slope.

Investigation on the effects of isothermal holding temperature and time on the coarsening mechanism and rheological properties of ADC12 Al semi-solid slurry

The current work's key emphasis is on investigating the influence of isothermal holding temperature and time on the microstructural development and coarsening rate during the directly generated semi-solid slurry of ADC12 Al alloy from the cooling slope process. Additionally, a thorough investigation is conducted to optimize process variables in the rheo-pressure die-casting process to determine the correlation between the non-Newtonian flow behaviour and its morphological characteristics of the quenched slurry of ADC12 Al alloy. The obtained results inferred that with increasing isothermal holding time, average grain size marginally increases initially, then significantly increases with increasing time, while shape factor increases first and then declines. Furthermore, when isothermal temperatures increase, the average grain size rises, while the shape factor rises first before decreasing. As a result of the increase in grain size due to elevated processing temperature and prolonged processing time, the aluminium alloy's hardness deteriorated. The ideal condition for more spheroidization of α-Al in the synthesized semi-solid slurry of ADC12 aluminium alloys was at an isothermal temperature of 565 °C and a holding time of 7 min. Under ideal processing conditions, the alloy's grain size, shape factor, and hardness were 31 μm, 0.89, and 62.32 HV, respectively. The semi-solids of ADC12 Al alloy have a low coarsening coefficient. The coarsening rate constant at 565 °C was calculated using the Lifshitz-Slyozov-Wagner relationship, and a value of 37 μm3/s was discovered. The findings of the isothermal rheology experiment demonstrate that viscosity decreases as the shear rate increases, confirming the existence of shear-thinning actions in semi-solid slurries.

Machine-learning-based nowcasting of the Vögelsberg deep-seated landslide: why predicting slow deformation is not so easy

Abstract. Landslides are one of the major weather-related geohazards. To assess their potential impact and design mitigation solutions, a detailed understanding of the slope processes is required. Landslide modelling is typically based on data-rich geomechanical models. Recently, machine learning has shown promising results in modelling a variety of processes. Furthermore, slope conditions are now also monitored from space, in wide-area repeat surveys from satellites. In the present study we tested if use of machine learning, combined with readily available remote sensing data, allows us to build a deformation nowcasting model. A successful landslide deformation nowcast, based on remote sensing data and machine learning, would demonstrate effective understanding of the slope processes, even in the absence of physical modelling. We tested our methodology on the Vögelsberg, a deep-seated landslide near Innsbruck, Austria. Our results show that the formulation of such a machine learning system is not as straightforward as often hoped for. The primary issue is the freedom of the model compared to the number of acceleration events in the time series available for training, as well as inherent limitations of the standard quality metrics such as the mean squared error. Satellite remote sensing has the potential to provide longer time series, over wide areas. However, although longer time series of deformation and slope conditions are clearly beneficial for machine-learning-based analyses, the present study shows the importance of the training data quality but also that this technique is mostly applicable to the well-monitored, more dynamic deforming landslides.

Failure process and mechanism analysis of rock slope induced by underground mining: a case study in Yanqianshan open-pit mine, China

Failure process and mechanism analysis of rock slope induced by underground mining: a case study in Yanqianshan open-pit mine, China

Оценка деформационных процессов фотограмметрическим способом в Agisoft Metashape

Active development of digital cameras and computer software has made close-range photogrammetry an extremely popular way to solve various engineering tasks, in particular, to control deformations of constructions and mining objects. Automated measurement of tie points enables reviving traditional techniques of deformation measurement through single shot photogrammetric approach (a zero basis, pseudo parallaxes) at a qualitatively new level. The paper deals with the contour mapping equal displacement method adaptation offered by the first author in the 1970s for processing in Agisoft Metashape. It is proposed to create a virtual basis for two single multi-temporal images by adding a matrix of empty pixels to them. This enables processing those as stereo pair, building virtual point clouds and altitude matrices. In order to test the technique, the authors considered the deflection deformation of various objects under lab conditions and shot their photos with a non-metric camera before and after loading. The obtained images were processed in Metashape, and then the above products were created and contours of equal deformations were plotted. It was found out that the accuracy of displacement value estimation with this method exceeds the spatial resolution of the images more than three times. The technology is applicable for objects deformations monitoring shifting mainly in a single plane, in future it is planned to test it in field at studying slope processes

Bedrock Fractures Control Groundwater‐Driven Mountain Slope Deformations

AbstractSeasonal deformation of mountain rock slopes can be driven by groundwater infiltration and depletion. Such processes could explain our field observation in the Aletsch Valley, Switzerland, where GNSS‐derived 3D annual displacement amplitudes reach 3.4 cm. However, the physical mechanisms behind such groundwater‐driven surface displacements are not well understood. Here, we develop a fully coupled hydromechanical model to simulate the relevant processes in a valley slope embedded with numerous fractures of variable sizes. The magnitude and orientation of transient annual slope surface displacement obtained from our model are in overall agreement with the field observations. The key geological factors controlling the type and magnitude of reversible mountain slope deformations are fracture network geometry, fracture aperture, and regional stress field. We show that the heterogeneity and anisotropy of bedrock hydromechanical responses, originating from depth‐dependent variations of fracture properties, play a critical role in groundwater recharge and valley slope deformation. During recharge events, pore pressure perturbations migrate downward from the groundwater table and toward the receiving stream and the deep subsurface. This process driven by pressure diffusion and poroelastic stressing develops in the subsurface with a great reach of up to a few kilometers, called critical hydromechanical response zone, and controls surface deformation patterns. During groundwater recession, this hydromechanical response zone expands downward and ground surface displacement vectors rotate upwards. Our results suggest that slope surface deformation can inform about subsurface permeability structures and pore pressure fluctuations, which have important implications for understanding groundwater flow in fractured bedrock slopes.

A semi-implicit material point method for coupled thermo-hydro-mechanical simulation of saturated porous media in large deformation

The coupled thermo-hydro-mechanical (THM) response of liquid-infiltrated porous media underpins the safe operation and maintenance of key engineering infrastructure. Challenges remain in modeling and understanding the complicated multiphysics processes of porous media subjected to THM loads and undergoing large deformation. In this study, we develop a stabilized material point method (MPM) for modeling the THM responses of large deformation problems in biphasic solid–fluid mixtures. A novel and efficient staggered solution scheme is proposed to solve the governing equations of the coupled system formulated in terms of four primary variables: solid displacement (u), liquid velocity (v), pore pressure (p), and temperature (T). The scheme solves the energy balance equation first and employs the resulting temperature to further advance the calculation of the momentum and mass balance equations using a semi-implicit fractional step method to facilitate equal-order interpolations. Both the incompressible and weakly compressible fluid are considered in the presented fractional step formulations. We also develop the axisymmetric form of the coupled MPM to increase the applicability and efficiency of the method in THM problems. The validity, stability, and robustness of the proposed method are demonstrated through three benchmark problems, including the heating of a saturated half-space, the non-isothermal consolidation of a soil column, and a three-dimensional axisymmetric problem pertaining to the thermoelastic response around a point heat source. The predictive capability of the proposed method for large deformation problems is further showcased by the simulation of the progressive failure process of a thermal-sensitive slope.

Effects of vegetation on the spatiotemporal distribution of soil water content in re-vegetated slopes using temporal stability analysis

The temporal stability of soil water is a critical state variable affecting hydrological process and structural stability of slopes. In this study, the effect of vegetation on the spatiotemporal characteristics of soil water content (SWC) was assessed via temporal stability analysis. Three types of re-vegetated slopes (grass, shrub, and grass-shrub) were constructed to explore the spatiotemporal distribution of the SWC at depths of 0–100 cm. Then, the effects of different vegetation covers on the SWC were explored. The coefficient of variation, the Spearman rank correlation coefficient, the mean relative difference, and the index of temporal stability were utilized to demonstrate the temporal stability of the SWC. Finally, a method of estimating the soil water status of re-vegetated slopes based on representative locations was developed. The results revealed that soil water dynamics were considerably governed by vegetation and rainfall. The vegetation cover considerably reduced the similarity of the spatial distribution pattern of the soil water, which tended to be more stable under grass cover. The weight-based prediction method developed in this study can more accurately estimate the overall soil water state of re-vegetated slopes. It provides a theoretical basis for the reasonable layout of SWC monitoring points and guidance for the ecological restoration of engineering slopes.

INŽENJERSKOGEOLOŠKI KONCEPT URBANIZACIJE ŠIREG PODRUČJA SREBRENIKA

To create a spatial plan for Srebrenik City, geological and engineering-geological surveys were carried out. A detailed engineering geological map of the terrain was prepared based on the results of all previous research. A graphic visualization of the field was developed based on the survey, presented through a map of the slope, an engineering geological map, a map of the terrain's stability, and a map of construction convenience. Zoning space was used to determine and allocate favorable and safe terrain for building construction. The paper describes an innovative concept for terrain research, taking into account various factors that determine urbanization conditions. This work has shown the importance of studying the earth's environment, natural slopes, and slope processes (shedding, sliding, landslides, etc.) when planning, designing, and building capital and other construction facilities.

A New Type of IUP Settlement in the Selenga River Basin, Northern Mongolia: The Kharganyn Gol-13 Short-Term Occupation Site

Here we outline the results of excavations at a recently discovered Initial Upper Paleolithic site, Kharganyn Gol-13, located on a tributary of the Selenga River in northern Mongolia. The Selenga valley and those of its tributaries were key routes along which humans dispersed during the Initial Upper Paleolithic. The concentration of sites of that period is highest here. Most are situated near outcrops of lithic raw material and are classifi ed as relatively long-term quarry-workshops. Excavations at Kharganyn Gol-13 have revealed a single cultural layer in sediments damaged by bioturbation and slope processes. We describe the stratigraphy and spatial structure of the site and its lithic industry, which is shown to belong to the Initial Upper Paleolithic, being dominated by opposite platform bidirectional blade reduction. Analysis of the lithics reveals a lack of available raw materials nearby. Apparently, cores brought to the site were already prepared. All cores are heavily reduced and scarce, tools are frequent. The concentration of lithics is low. We conclude that the site, located at a distance from outcrops of suitable rocks on Selenga River tributaries, was a short-term camp associated with a specifi c activity.