Foot Of Slope Research Articles

Modern morphodynamics in quarries of crystalline rocks of the Middle Pobuzhzhia

The study aims to characterize the modern morphodynamics in the quarries of crystalline rocks of the Middle Pobuzhzhia (Hnivanskyi, Sabarivskyi, and Novosyniavskyi quarries). General geographical and geomorphological research methods were used. General geographical methods include cartographic and remote sensing, while geomorphological methods involve morphographics, morphometrics, and morphodynamics. In the granite quarries of Middle Pobuzhzhia, we can identify both major and minor anthropogenic processes. The major processes shape the primary elements and forms of the relief in the quarries and dumps, while the minor processes add complexity to the structure of the anthropogenic relief. The main anthropogenic processes include: 1) blasting operations in quarries; 2) selection of crushed rock by excavators; 3) formation of overburden ledges; 4) formation of hydraulic dumps and dams; 5) filling of overburden dumps; 6) dumping within processing plants; 7) formation and modification of quarry roads. Anthropogenic processes are mainly represented by two groups of processes: gravity and water erosion. Gravity processes are common on quarry walls and embankment slopes. These processes include collapses, landslides, and slumps, primarily on hard crystalline rock layer, and landslides on loose bedrock layer. Water erosion processes are represented by linear and planar erosion. They are common in the upper parts of quarry walls, where the ledges of loose overburden are exposed, and on the slopes of overburden dumps and processing plants. Planar erosion can be in the form of total and small-scale flushing and accumulation at the foot of ledges and slopes of embankments. Linear erosion consists of the formation of gullies and small ravines, rather short with a significant slope of the longitudinal profile. For the first time, the main and secondary anthropogenic geomorphological processes for mining areas are identified and characterized. Anthropogenic processes in crystalline rock quarries were studied based on our field research, . For the first time, modern geomorphological processes in the quarries of the Middle Pobuzhzhia were examined from a regional perspective. The practical significance of the research is that its results can serve as a basis for predicting anthropogenic and anthropogenically determined processes within quarries.

Deposition, deformation, and flexure in a transpressional trough, Queen Charlotte fault, offshore Haida Gwaii (British Columbia, Canada)

Transpressional deformation along the Pacific–North American plate boundary off British Columbia (Canada) generates interactions between tectonic and depositional processes; first-order deformation is creation of a bathymetric trough by flexure of the Pacific plate. Interpretation of a suite of single-channel seismic reflection data in the central and southern trough shows second-order internal structure and depositional systems within the trough. Much of these sediments originated from Quaternary slope fans, although the age of the underlying oceanic crust is 8–13 Ma. These turbidite deposits overlie hemipelagic deposits. Two distinct layers of turbidite deposits in the trough can be explained by sediment deposition systems rather than tectonic events. We infer that the most recent flat-lying deposits, which have been previously interpreted in the northern trough as indicating a lack of compressive deformation, consist, in fact, of along-axis flows based on the general geomorphology of the margin. Second-order deformation consists of small-offset extensional and compressive structures common within 15 km of the foot of the continental slope. A few normal faults are observed tens of kilometers further out on the flexural bulge. Recent faults that cut the seafloor are observed offshore from the rupture plane of the 2012 M7.8 earthquake and match an area of extensional aftershocks. These faults may not be from bending of the entire bulge, which is 30–40 km wide, but from the plate being pulled into the underthrust zone. Maximum depression of the Pacific plate is also offshore from the region of recent rupture, indicating that this rupture is representative of long-term geologic processes.

Geodynamic hazard assessment for the archaeological park-museum by the town of Nikopol

This study was conducted to establish the engineering geological and hydrogeological conditions of the site and to assess the geodynamic hazard in relation to the design and construction of the archaeological park-museum and feeder road in the town of Nikopol (Bulgaria). The studied terrain occupies a river terrace and the foot of a delluvial slope with an elevation of 23-68 m. The tasks of the study are to identify: the geological structure of the slope, the area and depth range of the landslides, the location of the slip surface, the physical and mechanical properties of the engineering geological strata, the hydrogeological conditions, the current stability of landslides, the change of slope stability under the action of various factors. The ground investigation includes analysis of archival and published information on the area; geodetic survey of the landslide; engineering geological mapping; exploratory boreholes; geophysical surveys using the VES method; testing of soil and water samples; compilation of longitudinal engineering geological profiles and slope stability analysis using the computational models. To the south of the study site the slope is affected by an ancient landslide with a volume of about 30 million m3 developed on the right valley slope of the Danube River in the section between the plateau and the river terrace. Consistent landslides occur in its lower part. Slope stability calculations show that the landslides are triggered by a rise in the groundwater level, an earthquake and undermining of the slope base. Rock-falls has developed on the steep rock slopes, composed of moderately to highly weathered and fractured cherty and glauconitic limestones. The size of the rockfall blocks is in the range 0.3-0.8 m3 and their transport distance reaches from 10 m to 50 m from the base of the slope. Stabilization measures and facilities are proposed to strengthen the landslides and rockfalls in the considered section of the slope. For the landslides it is proposed to implement a counterfort embankment on which to build the feeder road, drainage ribs and drainage ditches. For protection of the buildings from collapsing rock debris, an anchored high-strength net is recommended. The design takes into account the trajectory of the falling blocks and their kinetic energy. For monitoring the condition of the landslides and rockfalls, as well as for evaluating the effectiveness of the implemented strengthening, drainage and coastal protection structures, a control and measurement system for regime observation was built.

Centrifugal test on the mechanical characteristics of existing prestressed anchor bolts in highway widening

To study the stress characteristics of existing prestressed bolts and slope stability during secondary excavation in a slope reconstruction and expansion project, five slope centrifugal tests were conducted. Tests focused on prestressed bolt-reinforced bedding slope with anchoring angles of 10°, 20°, 30°, 45°, and 60° during the excavation phase. The test results showed that the horizontal displacement at slope top increased slightly during the excavation of rock and soil masses in the upper slope part, while during the excavation of slope foot, such displacement increased rapidly. The bolt axial force in the anchorage section decreased along the anchoring depth. The peak axial force in the free section decreased significantly with the progress of excavation, and the axial force distribution in the free section presented a monotonically decreasing pattern. The anchoring angle significantly impacted the attenuation amplitude of axial forces in the anchorage section, while having insignificant effect on the distribution of axial forces. With the increase of anchoring angle, the cumulative horizontal displacement at slope top first decreased and then increased, while the earth pressure in slope first increased and then decreased, suggesting the presence of an optimal anchoring angle for the prestressed bolt.It is suggested that graded excavation should be adopted for the secondary excavation of slope engineering. Moreover, it is recommended to appropriately reduce the rate of excavation when working on the top and foot of the slope. Additionally, the design of the anchoring angle should consider various factors, including slope slope, rock formation, and the dip angle of the weak surface.

Изучение геологии Северо-Тянь-Шаньского трагического оползня

The method of reconstruction and investigation of the pre-landslide condition of the tragic landslide «Ak-Kain» of the Northern Tien Shan is proposed. Information about the study of this mountain slope located along the Almaty – Talgar highway above the sanatorium of the same name is presented. The results of a geological study of the structure and composition of ground sediments from the ceiling to the foot of the Northern slope, along which the landslide occurred, are presented. Also, visual studies of the remains of landslide masses have established the layers of the initial position of the cover soils and the underlying layers. A geometric model of the initial to landslide structure of the slope with its geological deposits both along the slope and in depth towards the basalt-granite rock surface has been developed. The results of the study are shown in the form of pictures of the exact zones and layers from the top of the slope to the bottom. The meaning of the proposed methodology consists in purposeful step-by-step scientific research, starting with the study of the geology, tectonics of the region, structure, composition of soils, taking into account the eluvial-deluvial-proluvial zones, their physico-mechanical, strength properties, especially attention is paid to the real anisotropy of the composition of soil deposits and their properties. The developed algorithms for studying infiltration movements of rainwater are described. In general, the results of this work make it possible to conduct targeted research by methods of mechanical and mathematical modeling to assess and determine the critical condition for predicting the place of the beginning of soil separation from the slope.

Dynamic responses of steep bedding slope-tunnel system under coupled rainfall-seismicity: Shaking table test

The coupling effects of rainfall, earthquake, and complex topographic and geological conditions complicate the dynamic responses and disasters of slope-tunnel systems. For this, the large-scale shaking table tests were carried out to explore the dynamic responses of steep bedding slope-tunnel system under the coupling effect of rainfall and earthquake. Results show that the slope surface and elevation amplification effect exhibit pronounced nonlinear change caused by the tunnel and weak interlayers. When seismic wave propagates to tunnels, the weak interlayers and rock intersecting areas present complex wave field distribution characteristics. The dynamic responses of the slope are influenced by the frequency, amplitude, and direction of seismic waves. The acceleration amplification coefficient initially rises and then falls as increasing seismic frequency, peaking at 20 Hz. Additionally, the seismic damage process of slope is categorized into elastic (2-3 m/s2), elastoplastic (4-5 m/s2) and plastic damage stages (≥ 6.5m/s2). In elastic stage, ΔMPGA (ratio of acceleration amplification factor) increases with increasing seismic intensity, without obvious strain distribution change. In plastic stage, ΔMPGA begins to gradually plummet, and the strain is mainly distributed in the damaged area. The modes of seismic damage in the slope-tunnel system are mainly of tensile failure of the weak interlayer, cracking failure of tunnel lining, formation of persistent cracks on the slope crest and waist, development and outward shearing of the sliding mass, and buckling failure at the slope foot under extrusion of the upper rock body. This study can serve as a reference for predicting the failure modes of tunnel-slope system in strong seismic regions.

Analysis on slope stability by anchorage based on soil creep with flood effect

In order to analyze the adverse effect of flood affection on slope stability, the analytical expressions of buoyancy force and capillary force, hydrodynamic pressure and impact force, and scour erosion were proposed based on the aging characteristics of soil shear strength and limit equilibrium theory. According to the load combination and flood action, shear failure occurs preferentially at the foot of slope. Then, the plastic zone continues to extend upward to produce traction landslide disaster mode. Furthermore, the power function relation between shear strength index and time was established. The nonlinear accelerated creep model was also obtained. At the same time, the safety factor formula for flood loading effect slope aging stability, the time-varying characteristic value of anchor force and the compensation value of anchor force were also obtained and used to research sliding mechanism. In addition, the numerical calculation example shows that the slope safety factor decreases by more than 20 % considering the effect of flood ascending scour and impact, and the compensation value of anchorage force increases obviously with time increasing. Simultaneously, the change rate of compensation value of anchorage force increases nonlinearly with the increase of design safety factor.

Using dendrogeomorphic and lichenometric approaches for rockfall analysis in the high mountains of Central Mexico

Rockfall represents one of the most destructive geomorphic processes for infrastructure and settlements located at the foot of mountain slopes. Furthermore, it poses a hazard for visitors and hikers. Despite the high anthropic activity in these environments, research on the reconstruction of rockfall in the high mountains of Mexico is still scarce. We used dendrochronological, dendrogeomorphological and lichenometric approaches to study the age and rockfall dynamics in a talus slope in central Mexico. Tree- ring chronologies were constructed from 140 samples of 50 Pinus hartwegii trees, 10 Juniperus monticola shrubs and 16 Ribes ciliatum shrubs to determine the age, frequency and rockfall stability at the upper limit of the forest (~4000 m a.s.l.). 52% of the tree samples showed impact scars, 39% callus tissue, 7% growth suppression and 2% corresponded to trees killed by rockfall. The frequency of rockfalls has increased since the second half of the 20th century, with the 1990s being the period of greatest activity. The years with the greatest disturbance were 1991, 1994 and 1998, possibly due to the intense rainfall that accumulated during the summer, as well as the earthquakes recorded in central and southern Mexico with magnitudes ⩾6. For the lichenometric analysis, 231 thalli of Rhizocarpon geographicum were measured in an active rockfall area. The results suggested three areas of rockfall activity. In the first area the ages were from 61 (±5 year) to 322 years (±41 year). In the second area, the ages were from 12 (±3 year) to 50 years (±12 year). The third area corresponds to an active zone with lichen-free blocks, located near the escarpment. The combination of dendrochronological and lichenometric methods allows a better determination of the minimum ages of rockfall, frequency, spatial distribution, and their possible factor triggers.

Analysis on the stability of a coal mine's dumping slope and its influence on oil pipeline

There is cross-interference between an-yu-meng line of Yunnan product oil pipeline about 920m and NO.1 dump of a coal mine. In order to analyze the stability of the dump slope under heavy rain and other working conditions, and the influence of the dump continued dumping on the pipeline safety, combined with the geological environment conditions, quantitative calculation of stability and numerical simulation in the study area, a comprehensive analysis is carried out. The results show that the south section of the dump is about 200m long and unstable under heavy rain, and the other sections are in a stable state, because the pipeline in the south section of the dump is located at the foot of the dump slope, the soil has the possibility of squeezing and shearing the pipeline, and the cross-interference pipeline in the north section of the dump is about 490m long, the northern section of the dump has a good stability. Most of the pipelines are buried at a depth of 1.5 m ~ 2 m, and the local depth is 7.5 m. the buried depth of the pipelines is in strongly weathered basalt, which is beneficial to the safety of the pipelines, the slope of the pipeline is inclined to the west, the slope of the pipeline is inclined in the opposite direction to the lateral compression of the dump, and the possibility of the pipeline forming lateral shear is small, the main hazards of the north slope instability to pipelines are burial and impact. The research results provide basis for safety evaluation and later treatment design of pipeline in cross-interference section of dump slope.

Method for Delineating the Formula Limit of the Continental Shelf under the Maximum Area Principle Constraint

In current practices of determining continental shelf area, the measured sediment thickness data do not effectively reflect the distribution of sediments across the area due to its dispersed nature. This issue raises potential limitations in unknown optimal survey line layout strategies for maximizing the posterior determination area. This paper adopts the binary search algorithm, relies on existing sediment thickness grid data, and uses geodetic formulas to build an ellipsoidal surface grid distance calculation model. This model quickly screens potential areas for the 1% sediment thickness line candidate points set. By constraining the azimuth parameter values during the construction process of the ellipsoidal point feature buffer zones, efficiently select the candidate points set for the 1% sediment thickness line. Furthermore, by elucidating the essential meanings of points on the formula limit and combining the candidate points set of the foot of the continental slope (FOS)+60 n mile line, the polygon minimal convex hull construction technique and a baseline points optimization algorithm with a length threshold are used to efficiently select points on formula limit. Experimental results demonstrate that this method can effectively assist coastal states in optimizing the determination of continental shelf area to the fullest extent under the length threshold requirements of the United Nations Convention on the Law of the Sea. Experiments have proven that compared to the traditional intersection method, the method presented in this paper can help coastal countries delineate a larger continental shelf area. In typical application scenarios, the gain in area can reach 77,278,427 m2 accounting for 0.51% of the total area.

Protective effects of measures for railway subgrade adjacent to excavation of a parallel pit

The Hongqiao Airport–Pudong Airport urban railway construction project in Shanghai, includes a 156.1-m-long deep strip foundation pit that runs closely parallel to the subgrade of the Shanghai–Hangzhou High-speed Railway, operating at 300 km/h. With a maximum excavation depth of 25.5 m and a minimum distance of only 10.6 m between the outer edge of the pit and the subgrade slope foot, controlling the deformation of the foundation pit in soft soil and ensuring the safe operation of the adjacent high-speed railway present significant challenges. Various protective measures were implemented to mitigate subgrade deformation caused by pit excavation, including partition excavations, 1.5-m-thick diaphragm walls, a servo steel strut system, isolation piles between the subgrade and diaphragm walls, and water-resistant barriers. The foundation pit, soil, and railway subgrade deformations during excavation were measured and analysed. The results demonstrate that the protective measures limited lateral diaphragm wall deformation to within 0.14% of the excavation depth. The maximum horizontal and vertical displacements of the subgrade caused by excavation were 3.2 mm and 1.5 mm, respectively. As a result, trains safely passed through this section at a limited speed of 120 km/h. The findings presented provide useful reference information for similar projects.

Instability evolution of expansive soil slope due to short duration-varying intensities of rainfall

This study examines the evolution of instability in induced expansive soil slopes under varying rainfall intensities. The destabilization evolution of expansive soil slopes and their stability under three different rainfall intensities were revealed through indoor modelling and numerical simulation. The findings indicate that slopes are not destabilized by short duration and low rainfall intensity alone. Slope failure under strong rainfall intensity follows a three-stage evolutionary process. As rainfall intensity increases, the slope's water content, soil pressure, and pore water pressure increase. However, the stress at each monitoring point of the slope affected by rainfall follows a different pattern. Under low rainfall intensity, the water content of the slope surface is higher than that of the slope foot. Under strong rainfall conditions, the water content of the slope foot is higher than that of the slope surface. Therefore, it is important to implement seepage prevention measures on the slope surface and drainage measures on the slope foot to ensure slope stability. Rainfall affects the soil pressure at each monitoring point of the slope, causing unloading on the slope surface and fluctuation at the foot of the slope. This phenomenon becomes more pronounced with increasing rainfall intensity. Numerical simulation confirms that the overall horizontal displacement distance of the slope increases with rainfall intensity, but the horizontal displacement range becomes shallower. The slope's maximum horizontal displacement occurs at its foot, with values of 0.29 m and 0.34 m under moderate and heavy rainfall, respectively, representing a growth rate of 17 %. Settlement of the slope under different rainfall intensities was greatest at the top of the slope area. The lateral stresses generated by the settlement resulted in soil uplift at the leading edge of the slope.

LITHO-STRATIGRAPHIC FEATURES OF THE LOWER CRETACEOUS DEPOSITS OF THE SKYBA AND DUKLA-CHORNOGORA NAPPES OF THE UKRAINIAN CARPATHIANS AND PROSPECTS FOR THEIR OIL AND GAS POTENTIAL

Lower Cretaceous sediments are widespread within the Skybа and Dukla-Chornorgora Nappes (Spas and Shypot Formations) over a considerable area. These deposits contain sandstones that can be industrial reservoirs for hydrocarbons. Such sandstones are described both on the surface and identified in deep wells. Thick sandy strata in the middle part of the Spas and Shypot formations formed as deposits of gravity flows at the second level of avalanche sedimentation, at the foot of the continental slope of the northern continental margin of the Tethys Ocean. Their formation is correlated with global regression in Aptian time. Porous sandstones of the Spas formations are present on the surface in the areas of the villages of Tershiv and Busovysko. They sometimes form bundles up to 60 m thick. They are exposed in the Oryv and Berehyv Skybas by deep wells 1-Lugy, 1-Shevchenko, and 4-Maksymivka. During the drilling of the 1-Shevchenko well from a depth of 6,900 meters, a film of oil and gas continuously flowed into the drilling mud. According to the results of industrial and geophysical studies, the section of the Spas formations of the second (lower) scale in the interval of 6,940–7,520 m was recognized as the most promising in terms of oil and gas potential. Two promising objects in the intervals of 7020–7070 and 6945–6985 m were identified, the oil and gas saturation coefficients of which are 65–70%. Similar sandstones are noted in the Hoverla sub-Nappe of the Dukla-Chornogora Nappe along the Balzatul River and its tributaries (Bila Tysa River Basin) as part of the Shypot Formation. Sandstones with an open porosity of 8–12 % were identified in the 1-Hrynyava and 1-Semakiv wells in the deposits of the Shypot Formation of the Skupiv sub-Nappe according to the results of industrial-geophysical research. When testing them in the 1-Semakiv well, from the total interval of 473–569 m, they received inflows of combustible gas and light oil with flow rates of 3,000 m3/day and 2.64 m3/day, respectively. The analyzed materials testify to the prospects of the Spas and Shypot formations in relation to the discovery of industrial accumulations of hydrocarbons.

Networks of geometrically coherent faults accommodate Alpine tectonic inversion offshore southwestern Iberia

Abstract. The structural styles and magnitudes of Alpine tectonic inversion are reviewed for the Atlantic margin of southwestern (SW) Iberia, a region known for its historical earthquakes, tsunamis and associated geohazards. Reprocessed, high-quality 2D seismic data provide new images of tectonic faults, which were mapped to a depth exceeding 10 km for the first time. A total of 26 of these faults comprise syn-rift structures accommodating vertical uplift and horizontal advection (shortening) during Alpine tectonics. At the regional scale, tectonic reactivation has been marked by (a) the exhumation of parts of the present-day continental shelf, (b) local folding and thrusting of strata at the foot of the continental slope, and (c) oversteepening of syn- and post-rift sequences near reactivated faults (e.g. “passive uplift”). This work proves, for the first time, that geometric coherence dominated the growth and linkage of the 26 offshore faults mapped in SW Iberia; therefore, they are prone to reactivate as a kinematically coherent fault network. They form 100–250 km long structures, the longest of which may generate earthquakes with a momentum magnitude (Mw) of 8.0. Tectonic inversion started in the Late Cretaceous, and its magnitude is greater close to where magmatic intrusions are identified. In contrast to previous models, this work postulates that regions in which Late Mesozoic magmatism was more intense comprise thickened, harder crust and form lateral buttresses to northwest–southeast compression. It shows these structural buttresses to have promoted the development of early stage fold-and-thrust belts – typical of convergent margins – in two distinct sectors.

Effect of slope position on the spatial distribution of soil preferential flow paths based on point pattern analysis.

The mechanisms of soil preferential flow occurrence and development are influenced by topographic and geomorphological factors. However, the complex distribution patterns of soil preferential flow paths on different slopes remain unclear. Therefore, taking the subtropical evergreen broad-leaved forest area of Simian Mountain as the study area, this study conducted a quantitative analysis of the spatial distribution characteristics and spatial association of soil preferential flow at different slope positions (slope shoulder (SS), mid-slope (SM) and slope foot (SF)) using field staining tracer tests and spatial point pattern analysis. Results showed that the maximum infiltration depth, the depth of matrix flow, average dye coverage, preferential flow fraction and length index of the SM plot were all greater than those of the SS and SF plots. The number of preferential flow paths in different slope positions decreases with soil depth, with most preferential flow paths measuring 2.5-5.0 mm in each soil layer. The total number of preferential flow paths in SM plot was approximately twice that of the SS and SF plots, and the preferential flow paths in SM plot, regardless of pore size, were all in an aggregated distribution. These findings indicated that differences in soil physical properties and vegetation coverage at different slope positions lead to variations in the spatial distribution and association of soil preferential flow paths. Accordingly, strategies must be modified for the distribution, storage and utilisation of soil water resources. This study provides a theoretical basis for the effective management and protection of water resources in the Simian Mountain area and a scientific basis for exploring the mechanisms of the occurrence and development of the water cycle in forested watersheds.

Термическое воздействие на приземный слой тропосферы как способ управления рисками природных чрезвычайных ситуаций

Purpose. Natural emergencies that occur in mountainous regions annually damage ecosystems, the country's economy and lead to the death of people. On leeward mountain slopes, where precipitation is insufficient, there is an increased fire hazard of territories, complicating water supply of the population and ecosystems. On windward slopes excessive precipitation leads to the risk of avalanches, floods, and mudflows. The search for ways to redistribute the volume of precipitation between the windward and leeward slopes to control the risks of natural emergencies is relevant. The intensity of precipitation is significantly affected by the dew point height (DPH), which determines the position of the lower cloud boundary (the lower the dew point height, the greater the probability of precipitation). The article discusses the possibility of local thermal impact on the ground layer of the troposphere by heating a section of the mountain windward slope in order to increase the dew point height for the subsequent natural transfer of the precipitation zone to its leeward slope. The purpose of the study is to determine the values intervals of the difference in average temperatures of the tropospheric ground layer at its opposite boundaries and values intervals of average wind speed over the relief, where the thermal interaction of the tropospheric ground layer with a local area of the earth's surface can be used to effectively control the dew point height over the entire windward slope of the mountain. Methods. Three-dimensional field modeling is applied using the Fire Dinamic Simulator software product, which provides a numerical solution of the complete nonlinear Navier-Stokes thermohydrodynamic equations for low-speed temperature-dependent flows. Findings. It has been established that the thermal effect on the ground layer of the troposphere above the foot of the mountain windward slope under forced convection conditions can be used to control the distribution of the dew point height over this entire slope. Research application field. The conducted numerical study is the initial stage of a new scientific direction related to natural emergencies risks control caused by excess or lack of mountain slopes moisture (floods, droughts, forest and steppe fires). The obtained results indicate the fundamental possibility of such control by means of local temperature impact from the earth's surface to the ground layer of the troposphere. The practical significance of the results, including financial costs, required for the specified impact on the ground layer of the troposphere, can be revealed in subsequent publications after conducting full-scale experiments. Conclusions. The possibility of reducing the natural emergencies risks caused by excess or lack of moisture in mountain slopes territories by controlling the dew point height value over windward mountain slopes is shown. A solution to this problem is proposed through thermal impact on the ground layer of the troposphere from the earth's surface.

The role lyncharts in the redistribution of products of anthropogenic soil erosion

The paper considers the spatial heterogeneity of the flow of eroded soil material to the foot of the plowed slope and further to the side of the valley in the presence of a lyncahrt resulting fr om mechanical tillage on the lower border of arable land. A small catchment area in the area of intense Chernobyl pollution has been studied, wh ere the po- sition of the lower boundary of the arable land over the past few decades coincides with the upper boundary of the side of the valley. This made it possible to trace the spatial patterns of the distribution of eroded material with stable functioning of the lynchart as an important lithodynamic boundary accumulating and redistributing the slope runoff of sediments. The determination of the volume of material coming from arable slopes was carried out using mathematical modeling of erosion based on a high-precision digital terrain model, climate data, soil erodibility and crop rotations. To assess the intensity of accumulation, 137Cs of Chernobyl origin was used as a reliable tracer. The bulk of the eroded material enters the valley network through a system of slope hollows that concentrate the slope runoff and cut through the valleys. In the areas of the valleys sides outside the runoff concentration zones, the re- deposition of the material mainly depends on the morphology of the lyncahrt, occurs locally and is associated with episodic overflows as a result of the gradual filling of the depression before the lyncart. Under existing conditions, accumulation on the sides of the valley occupies a relatively small share in the total sediment balance of the studied catchment area. Significant changes may occur due to a gradual decrease in the barrier role of the soil as a result of sediment accumulation and climatic changes that contribute to an increase in erosion rates.

Large-scale toppling slope under water level fluctuation of reservoir: A case of Yunnan Province, China

Landslides induced by reservoir inundation are common in Southwest China, negatively influencing hydropower stations. The Wunonglong hydropower station dam was constructed in the upper reaches of the Lancang River, accordingly causing the water level at the Lajinshengu slope to increase by 30 m. A tension crack with a visible depth of 8 m was observed in the upper sector of the Lajinshengu slope after reservoir impoundment for 170 d. In the following days, numerous cracks appeared on the surface of the slope, and the maximum displacement of the slope reached 3.22 m. Then, a large-scale active deformation body within the Lajinshengu slope formed with an area of 2.62 × 105 m2 and a volume of 1.65 × 107 m3. Detailed field investigations, on-site monitoring, and centrifugal model tests were carried out to analyze the surface features, deformation characteristics, and failure mechanism of the Lajinshengu slope. The results show that the slope is an ancient landslide, divided into two parts (i.e. zone A and zone B) by the gully. Zone B is a traction landslide caused by the displacement of zone A. The long-term inundation weakens the soft rock at the slope foot, intensifying the toppling of bedrock and consequently triggering the sliding of the overburden in zone A. The failure mode of the Lajinshengu slope is a typical case of toppling-sliding failure, and the underlying rock toppling drives the overlying sliding. In addition, early identification methods for toppling deformation covered by overburdened soil were proposed based on monitoring data and deformation signs.

Centrifugal model test study on instability mechanism by rain of widened roadbed slope

To study the instability mechanism of the slope of the widened highway roadbed during rainfall, a rainfall simulation device was developed for geotechnical centrifugal model testing. Settlement and widening tests for the old roadbed, and settlement and simulation rain tests for the widened roadbed were performed in sequence. During the test, the settling process of the old and the new roadbeds and the instability process of the embankment slope by rainfall were observed by the settling monitoring device installed on the centrifuge manipulator system. The test results showed that the major consolidation of the old roadbed was completed in the first year of operation; after the roadbed was widened, the new settlement of the old roadbed was much smaller than the new settlement of the widened roadbed, resulting in the differential settlement between the new and old roadbeds. Longitudinal cracks formed by the differential settlement on the road surface provided infiltration channels for rainwater. After rainfall, the rainwater first infiltrates downward at the foot of the slope and expands the vertical joints of the loess to form vertical infiltration channels, causing settlement at the foot of the slope. After that, the rainwater infiltrated laterally into the interior of the roadbed and beyond the slope toe, increasing further settlement. The settlement area expanded continuously, eventually causing the roadbed slope to become unstable. According to the research results, the key to preventing rainfall damage to the subgrade was to protect the slope foot, block the rainfall infiltration channel, and reduce the settlement of the foundation.

Экологическая оценка варьирования состава травянистого покрова по контрастным элементам мезорельефа Лесной Опытной Дачи РГАУ-МСХА имени К.А. Тимирязева

The present paper analyzes the results of a comparative ecological study of regional typological patterns of spatial variability of the herbaceous cover composition in the conditions of a gently sloping mesorelief at the Forest Experimental Station of the Russian Timiryazev State Agricultural University – the background object of environmental monitoring for the northern part of the Moscow metropolis. Standardized descriptions of the composition and biodiversity assessments of the vegetation cover are presented on five representative sites of the orographic transect, cutting in the direction from northeast to southwest the gently sloping moraine hill dominating in the mesorelief and its opposite slopes of the northeastern and southwestern exposures, including their foots – with a total height difference not more than 15 meters. The greatest variety of herbaceous species from the 20 families represented in the studied plots was found at the foot of slopes with more stable humidification conditions, and its minimum level was at the summit of a moraine hill with pronounced summer desiccation of the topsoil of the zonal sod Podzoluvisols characteristic for the Forest Experimental Station. Other important ecological factors of herbaceous biodiversity are the exposure and shape of the slope, which affect both the temperature regime and the seasonal dynamics of the topsoil moisture – under conditions of relatively insignificant variation in the tree canopy density and pronounced recreational load on the ground vegetation and topsoil. Humus-podzolic soils dominating on the bottom of the slope of the north-eastern exposure with a steadily increased moisture level are characterized by reduced resistance to recreational load, which leads to the maximum severity of the pathway network and relatively reduced biodiversity indices. The analysis of the patterns of spatial variation in the composition of the herbaceous cover allowed one to identify the problematic environmental situations and factors of reducing its biodiversity, that has to be taken into account when further planning the regulation of recreational load at the Forest Experimental Station and similar areas of the forest infrastructure of the northern part of Moscow, as well as when assessing the projected anthropogenic impact in the conditions of the Moscow megalopolis and comparable urban ecosystems of the southern taiga and mixed-forest subzones at the European territory of Russia. Keywords: BIODIVERSITY, URBAN FOREST PARKS, FOREST ECOSYSTEMS, MOSCOW, IMPACT ASSESSMENT, RECREATIONAL LOAD, HERBACEOUS COVER, ENVIRONMENTAL FACTORS, URBAN ECOSYSTEMS