Entire Slope Research Articles

GEOTECHNICAL DESIGN FOR THE STABILIZATION WORKS OF THE LETTOMANOPPELLO LANDSLIDE (ABRUZZO, ITALY)

In order to stabilize the landslide of Lettomanoppello, the stabilization works are finalized to reduce/control the causes and to mitigate the economic, social, and environmental risks. A careful geotechnical design, of the stabilization works can allow an economic recovery of the cost by means of a virtuous and profitable process to produce electric energy. The landslide of Lettomanoppello, located in Central Italy (south-west of the city of Pescara) is a large, very complex active landslide. Slope instability phenomena, often triggered by intense rainfall and seismic events are recurrent in this region of Apennines and frequently result in serious damage to the historical-environmental heritage and in dreadful economic losses. The stability of slope is mainly affects by the hydrogeological conditions of the area characterized by a complex drainage system. Various stabilization works were executed along the slope during the years. The paper presents the studies (geological and geotechnical characterizations) and a general plan of the works required to stabilize the entire slope. The general stabilization project includes different types of works: (i) structural works (retaining walls), effective in short term; (ii) drainage works (tunnel for deep water drainage), effective to medium-long term, aimed at reducing/controlling the major causes of the landslide; (iii) protection from erosion at the toe of slope and surface drainage works. The tunnel crosses a horseshoe shape underneath the historical centre of Lettomanoppello and the elevations of its mouths are at 296 m a.s.l. The drainage waters will be conveyed to pipe towards a hydraulic turbine located at 206 m a.s.l. in the lower part of the slope. Furthermore, the geometry of the cut-off retaining walls at the toe slope are conceived as foundations of aeolian turbines.

Characterization of transient movements within the Joshimath hillslope complex: Results from multi-sensor InSAR observations

This paper investigates the spatiotemporal characteristics and life-cycle of movements within the Joshimath landslide-prone slope over the period from 2015 to 2024, utilizing multi-sensor interferometric data from Sentinel‑1, ALOS‑2, and TerraSAR‑X satellites. Multi-temporal InSAR analysis before the 2023 slope destabilization crisis, when the region experienced significant ground deformation acceleration, revealed two distinct deformation clusters within the eastern and middle parts of the slope. These active deformation regions have been creeping up to −200 mm/yr. Slope deformation analysis indicates that the entire Joshimath landslide-prone slope can be categorized kinematically as either Extremely-Slow (ES) or Very-Slow (VS) moving slope, with the eastern cluster mainly exhibiting ES movements, while the middle cluster showing VS movements. Two episodes of significant acceleration occurred on August 21, 2019 and November 2, 2021, with the rate of slope deformation increasing by 20% (from −50 to −60 mm/yr) and around threefold (from −60 to −249 mm/yr), respectively. Following the 2023 destabilization crisis, the rate of ground deformation notably increased across all datasets for both clusters, except for the Sentinel‑1 ascending data in the eastern cluster. Pre-crisis, horizontal deformation was dominant both in the eastern and middle clusters. Horizontal deformation remained dominant and increased significantly in the eastern cluster post-crisis phase, whereas vertical deformation became predominant in the middle cluster. Wavelet analysis reveals a strong correlation between two acceleration episodes and extreme precipitation in 2019 and 2021, but no similar correlation was detected in other years. This indicates that while extreme rainfall significantly influenced the dynamics of slope movements during these episodes, less strong precipitation had a minimal impact on slope movements during other periods.

Investigation on the Instability Mechanism of Expansive Soil Slope With Weak Interlayer Based on Strain Softening

ABSTRACTExpansive soils are widespread in the world and coincide with areas of high human activity. The main cause of deep instability of expansive soil slopes is due to their softening caused by excavation and seepage. By developing a comprehensive numerical model based on the theory of unsaturated soil, this study examines the characteristics of stress and displacement distribution of expansive soil slopes through hydraulic‐mechanical coupled numerical simulation. This study analyzes the evolution patterns of slopes with excavation unloading and seepage of water storage to reveal the mechanisms of deep‐seated instability of expansive soil slopes. The findings demonstrate that: The instability of expansive soil slopes begins at the foot of the slope and propagates along the interlayer, affecting the entire slope. Excavation leads to the softening of the expansive soil interlayer and the transfer of shear stress. During water storage, the weakening of the soil strength results in slope instability along the weak interlayer slip. Softening of the expansive soil interlayer facilitates the redistribution of shear forces in the slope and alters the distribution law of the plastic zone in the deep layer. Overly slowing down the slope leads to significant excavation unloading, which is detrimental to the slope's stability.

Slope stability analysis of colluvial deposits along the Muketuri-Alem Ketema Road, Northern Ethiopia

Slope failures are a significant natural geohazard in hilly and mountainous regions, often resulting in loss of life and infrastructure damage. The Muketuri-Alem Ketema road in Ethiopia is particularly vulnerable to landslides due to colluvial deposits on steep slopes from the higher northeastern plots to the lower Jemma River valley. This study investigates the characteristics of colluvial soil and evaluates the stability of slopes prone to landslides. It combines geophysical data, penetrometer tests, laboratory analyses, Google Earth images, and detailed field visits to assess the soil and bedrock composition and structure. Numerical methods, including limit equilibrium (Bishop, Janbu, Spencer, and Morgenstern-Price methods) and finite element methods, were used to analyze slope sections under various saturation conditions and simulate different rainfall patterns. The results indicate that the Bishop, Morgenstern-Price, and Spencer methods produce similar safety factors with minimal differences (<0.3%), while the Janbu method shows more significant variation (1.5%–5.6%). Safety factor differences for sections A-A and B-B range from 5.26% to 9.86% and 3.5%–4.7%, respectively. Simulations reveal that short-term saturation significantly reduces the stability of the upper slope layer by 20%–46.76%, and long-term saturation decreases the entire slope section by 26.81%–46.76% compared to dry conditions due to increased pore water pressure and self-weight. Long-term saturation effects, combined with dynamic loads, can further reduce colluvial soil stability by over 50% compared to a dry static state. The finite element method predicts larger failure zones than limit equilibrium methods, emphasizing the need for accurate predictions to characterize slope behavior during failure and inform stabilization decisions. This study provides crucial data for maintaining and planning the Muketuri-Alem Ketema Road, highlighting slope performance over time and the effectiveness of stabilization techniques.

Dynamic optimization design of open-pit mine full-boundary slope considering uncertainty of rock mass strength

Rock and soil strength profoundly influences the stability of open-pit mine slopes. Traditional slope design, based on limited drilling data, often disregards inherent uncertainties. Effectively utilizing new sample information from mining operations poses a challenge, hindering dynamic and differentiated design for the entire perimeter slope. To address this, we propose a dynamic optimization method considering rock mass strength uncertainty for the entire perimeter slope. Our approach involves designing slope angles separately in different zones, while thoroughly considering decision-makers' preferences. Furthermore, we delegate the final adjustment authority of slope angles within the safety permissible range to on-site decision-makers. Compared to traditional methods, our dynamic design method incorporates rock mass strength uncertainty into slope evaluation while also accounting for decision-makers' safety and economic preferences. Through a case study of a specific open-pit mine, our proposed dynamic design method increases the overall slope angle by approximately 2.5°, fully accommodating the influence of on-site decision-making preferences on slope design. This article introduces a new method of dynamic optimization of open-pit mine slope based on simplified observation method, which improves the flexibility of decision-making and realizes the differential design of the whole surrounding slope.

Morphology and evolution of submarine canyons around the Zhongsha Platform, South China Sea: Implications for sedimentary processes in a modern isolated carbonate setting

Recent high-resolution multibeam bathymetry and seismic data from the platform-top to the abyssal plain of the Zhongsha Platform allow for a detailed investigation of the morphologies, spatial distribution, and trigger mechanisms of submarine canyons, submarine landslides, and associated sedimentary features along modern isolated carbonate slopes. The newly observed Zhongsha Canyon System provides a natural laboratory for reconstructing the source-to-sink sedimentary processes in a pure carbonate setting. This study reveals that there are thirty-four submarine canyons at water depths between 300 and 4100 m on the northern and western slopes of the Zhongsha Platform. Two morphologically different submarine canyon types are identified: (1) dendritic canyons, which exhibit abundant tributaries with scallop-shaped failures at the canyon heads, and (2) linear canyons, which feature rare tributaries with elongated failures at the canyon heads. The dendritic canyons are more complex in morphology than the linear canyons as a result of the interaction among numerous tributaries. Canyon initiation and evolution pass through three phases: (1) initial stage: off-platform sediment transport and platform margin failures contribute to erosive gravity flows; (2) developmental stage: initiation and incision of submarine canyons along platform margin failures; and (3) mature stage: numerous mature canyons along the platform margin. Off-platform sediment transport, density cascading, gravity flows, monsoon currents, and deep circulation play an essential role in shaping the slope morphologies. In addition, submarine landslides are extensively observed along the entire slope of the Zhongsha Platform at water depths of 600 to 4200 m, including canyon-wall failures, slope landslides, canyon-front landslides, and slope-toe failures based on their location and genesis. These processes can steepen the platform slopes by upward retrogressive and downward progressive erosion. On a larger scale, the persistent submarine canyons and occurrence of landslides around the Zhongsha Platform contribute to the uniqueness of this landscape among modern carbonate slopes. The morphologies and evolutionary processes of Zhongsha Canyon System present significant differences from the global carbonate submarine canyons in terms of their dimensions and trigger mechanisms. The findings of this work provide novel insights into the morphological features and sedimentary processes of submarine canyons in modern isolated carbonate platform settings.

Decoupling of carbon burial from productivity in the northeast Indian Ocean

The concentration of atmospheric carbon dioxide (CO2) is a crucial climate parameter as it has far-reaching implications on global temperature. The oceans are a significant sink for CO2. Biologically mediated carbon sequestration, in the form of both inorganic (CaCO3) and organic carbon (Corg), and its subsequent burial in marine sediments play a vital role in regulating atmospheric CO2. Understanding the distribution of carbon in marine sediments under different environments can help predict the fate of excess CO2 in the future. We studied the factors affecting the basin scale variation in carbon burial in the climatically sensitive northeast Indian Ocean, by using the data [CaCO3, Corg, Corg/Nitrogen, and isotopic ratio (δ13C, δ15N) of organic carbon] from a total of 718 surface sediments. The entire continental shelf and slope contain <10 % CaCO3. The highest CaCO3 is in the deepest parts of the central northeast Indian Ocean, away from the mouth of major river systems. Despite of the high productivity, the low Corg on the continental shelf is attributed to the well-oxygenated coarse-grained sediments. The lowest Corg is found in the well-oxygenated deeper central northeast Indian Ocean. Interestingly, the highest total carbon is in the deeper central and equatorial regions, far away from the highly productive marginal marine regions. Our study reveals that the grain size, terrigenous dilution, dissolved oxygen, and water masses strongly influence carbon accumulation in the northeast Indian Ocean, with only secondary influence of the productivity.

Mechanism of a rainfall-induced landslide in a large-scale flume experiment on a weathered granite sand

IntroductionsA large-scale flume experiment was performed to evaluate the mechanism of landslide occurrence due to rainfall using weathered granite sand. The dimensions of the flume were 9 m (length), 1 m (width), and 1 m (depth). The weathered granite sand from the actual landslide site at Da Nang City, Vietnam was used. The pore water pressure was measured by a pore-water pressure transducer at two depths (middle and bottom) to determine the process of rainwater infiltration into the soil. The surface deformation was measured with extensometers at three positions of the slope. The deformation of the entire slope was determined by the 160 cylindrical-shaped makers evenly spaced in the slope and three cameras.ResultsThe results showed that the rainfall infiltrated into the slope process, increasing from negative pore water pressure to approximately 0. The maximum shear strain contour has been plotted in total and in time increments. The shear band was detected from the time increments maximum shear strain contour. The localization in the shear band formed just before failure.ConclusionsTo the best of our knowledge, this is the largest scale laboratory test ever conducted to calculate the shear band. Moreover, it was found that the failure occurred when the sand was in an unsaturated phase. Failure does not seem to depend on the increase in pore water pressure but on the maximum shear strain. This feature can be used to explain the phenomenon of landslides that occur even when the groundwater level does not increase but large deformation occurs.

Impacts of straw mulching in longitudinal furrows on hillslope soil erosion and deposition in the Chinese Mollisol region

In the Northeast Mollisol region of China, straw mulching has a great effect on preventing soil loss from ridge tillage, but how furrow straw mulching (FSM) impacts the spatial distribution of erosion-deposition and sediment sources in longitudinal ridge tillage systems is still unclear. Therefore, this study was to quantify the effects of the FSM on the spatial distribution of soil erosion-deposition and sediment sources in longitudinal ridge tillage systems by using the magnetism tracing methodology and indoor simulation rainfall experiments. The experimental treatments included two surface treatments: without the FSM (NFSM) and with the FSM of 0.30 kg·m−2 amount, two rainfall intensities of 50 and 100 mm h−1 were included; each experiment was run for 60 min at a soil pan with a 5° slope gradient, 6.2 m length, 1.3 m width and 0.7 m depth. The results indicated that, compared with the NFSM treatment, the total slope runoff and soil loss in the FSM treatment at two rainfall intensities were decreased by 41.6 % and 99.5 % and by 37.9 % and 97.7 %, respectively, and the reduction in slope runoff and soil loss decreased with an increase of rainfall intensity. The total mass of sediments intercepted by straw mulching on the entire slope accounted for 36.9 % and 10.4 % of the total soil loss in the NFSM treatment, respectively. Erosion regimes dominated on the hillslope of the NFSM treatment with strong-weak alternation at two rainfall intensities, while for the FSM treatment, only deposition regime was observed at 50 mm h−1 rainfall intensity; a slight change with erosion-deposition on the ridge tops was observed and deposition in the furrows was observed at 100 mm h−1 rainfall intensity. Furthermore, the FSM treatment changed the main sediment source from ridge tops to furrows on the hillslope compared to the NFSM treatment, whose sediment contributions from the ridge tops and the furrows at the two rainfall intensities were approximately 16.4 % and 83.6 %, respectively. In conclusion, FSM should be promoted due to its high efficiency in decreasing slope runoff and intercepting sediments. The findings of this study served as a scientific reference for effectively controlling soil erosion along slopes in the Chinese Mollisol region.

Pre- and post-failure behaviour of a dike after rapid drawdown of river level based on material point method

The rapid drawdown of river level is very detrimental to the stability of dikes. In this paper, the entire slope failure process of a real dike with sandy soil interlayer after rapid river drawdown is accurately reproduced using the material point method (MPM). The analysis of pre-failure behaviour, in combination with field test results, reveals the triggering mechanism of such dike slope failure, demonstrating that the presence of sandy soil interlayer is the leading cause of dike instability. By tracking the response of the dike slope from failure initiation to runout termination, the failure mode of the dike slope with sandy soil interlayer is identified as a progressive and retrogressive failure mode, with shallow and deep-seated slip surfaces appearing successively. Parametric studies indicate the friction angle, cohesion, dilatancy, and permeability of the sandy soil play significant roles in dike slope stability. A relationship between the permeability of sandy soil and the maximum sliding displacement is also found. In the face of rapid river drawdown, river-facing slope surface protection is the most effective protection measure for such dike slopes with sandy soil interlayer, while traditional riprap protection at the slope toe has a limited protecting effect.

Study of Deformation and Fault Mechanisms in Bedding-Locked Rock Slope

In geotechnical engineering, a bedding slope often leads to geological disasters, particularly in the case of bedding-locked rock slopes. This study focuses on a typical bedding-locked rock slope in western Henan Province, China. The deformation and fault characteristics were examined through the development of laboratory analogue experiments which allowed for the analysis of the physical and mechanical properties of the rock slope when subjected to a load. The deformation and faulting mechanisms of the slope were studied through the application of different strength loads to the slope model, as well as through the combination of its physical properties. The deformation and fault process were then simulated through the application of numerical modeling. The results reveal that the upper part of the slope features a linear slip surface, while the lower part features a circular arc slip surface, resulting in “linear + circular arc” damage geometry and a relatively flat shear surface. Maximum and minimum lateral displacement occur around the top and the foot of the slope, respectively, leaving the intermediate values at the middle. The shear strength is greater at the locking section, with the highest value found at the foot of the slope, followed by the middle and the top. The evolution of slope deformation can be divided into three stages: the loose deformation stage at the slope top and back; the stage of crack development, extension, and interlayer misalignment; and the stage of complete through crack formation and complete instability damage of the slope. Thus, the process of the deformation and damage of a rocky slope under loading conditions can be described as follows: load-induced loosening and deformation at the top and back of the slope, crack development, expansion, and interlayer misalignment, as well as tension crack expansion at the foot of the slope. The latter can expand and intensify interlayer misalignment, leading to the destruction of the locking section and ultimately causing the destabilization of the entire slope.

Geomorphological assessment as basic complement of InSAR analysis for landslide processes understanding

Landslide research has benefited greatly from advances in remote sensing techniques. However, the recent increase in available data on land surface movement provided by InSAR techniques can lead to identifying only those areas that were active during data acquisition as hazardous, overlooking other potentially unsafe areas or neglecting landslide-specific geological settings in hazard assessments. Here, we present a case study that serves as a reminder for landslide researchers to carefully consider the geology and geomorphology of study areas where complex active movements are detected using InSAR technology. In an area extensively studied using InSAR and UAV-related techniques, we provide new insights by applying classical approaches. The area is the coastal stretch of La Herradura, and its importance lies in the fact that it has served as an illustrative example in the Product User Manual of the European Ground Motion Service, a platform that provides ground motion data on a European scale. Our approach is to revisit the area and carry out qualitative geological and geomorphological assessments supported by UAV surveys and GIS spatial analysis on a broader scale than previously published investigations. Our classical approach has yielded the following new observations, crucial for risk assessment and land management: active landslides identified by InSAR techniques since 2015 are bodies nested within large mass movements that affect entire slopes. A variety of processes contribute to slope dynamics, such as large slumps, marble rock spreading and block sliding, and surface rock falls and topples. The revised delineation of the landslide bodies reveals an area almost five times larger than previously mapped. These new findings in a well-known area highlight (1) the importance of updating and downscaling previous maps and (2) the ongoing importance of classical fieldwork and desk studies as basic complements to modern InSAR analyses.

Factors affecting the sediment concentration in runoff from a slope during the spring thawing period

AbstractSediment concentration (S) is vital in soil erosion models. However, research on estimating S at different positions on slopes in the spring thaw period is difficult. Thus, in this research, four flow discharges, two slope gradients, and four initial thawing depths were used in combination with Rare Earth Elements (REEs) tracing techniques to investigate the effects of hydraulic parameters at different locations of freeze–thaw rill flows on S. The results show that the S on the freeze–thaw slope gradually increases from the first section to the third section of the slope, with an increase of 43.99% from the first slope section to the third slope section. The flow velocity is the most critical factor to affect the S (R2 &gt; 0.7). The prediction equation of S on the entire slope under freeze–thaw conditions was established based on the flow turbulence intensity and relative gravity (R2 = 0.769). This study examined the S and hydraulic parameters of the freeze–thaw rill flow, which provided a reference for further research on the soil erosion model during the spring thawing period.

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.

Evolution of an earthquake-induced landslide complex in the South Island of New Zealand: How fault damage zones and seismicity contribute to slope failures

Abstract Tectonic deformation within fault damage zones can influence slope stability and landslide failure mechanisms due to rock mass strength effects and the presence of tectonic structures. Here, we used detailed site investigations to evaluate controls on deformation within the Half Moon Bay landslide complex, located ~1 km from the surface trace of the Hope fault in the South Island of New Zealand. During the 2016 Mw 7.8 Kaikōura earthquake, the slope experienced up to ~13 m of displacement and partially transitioned into a rock avalanche (with a volume of ~350,000 m3). Deep-seated deformation of the entire slope predated the 2016 earthquake. Results of geomorphological analysis, field mapping, geophysical surveys, slope displacement, and a 60-m-deep borehole in the incipient portion of the landslide indicated the presence of a subvertical tectonic fabric and intense fracturing and weathering of the rock mass, which gradually decrease with depth. Based on these results, we established a conceptual model wherein the landslide failure mechanism is a combination of flexural toppling along the subvertical structures coupled with joint-step-path sliding along preexisting, closely spaced discontinuities within the graywacke rock mass. Coseismic slope displacements revealed a large area of incipient failure behind the headscarp of the 2016 rock avalanche, which will likely result in further avalanching at the site. This case study demonstrates that inherited tectonic structures (combined with seismicity and weathering in an oversteepened coastal slope) play an important role in the evolution of hillslopes near active faults.

Analysis of the stability of the Kuban river landslide slope involving the materials of landslide hazard monitoring

The article discusses the improvement of methods for calculating the landslide threat in the monitoring of landslide hazard areas on the Kuban River and the study of the possibility of their negative impact on the operated hydraulic structures. The growth of economic activity, intensive use of water resources in the Kuban River basin leads to a decrease in the bearing capacity of slopes and an increase in landslide phenomena. These processes are also observed in the basins of other anthropogenically developed rivers of the Russian Federation. Shore protection structures and their construction are justified on the basis of the limit state method in accordance with the requirements of SR 58.13330.2011. The stability of such structures should be determined by reference to the stability conditions of the entire slope taking into account all acting loads and impacts. To solve this problem it is very effective to use a complex of structures regulating the flow of the river, flow guides (dams made of selected rockfill), slope-strengthening ones, etc. Measures justifying economic activity on a landslide slope are very effective. The right slope of the Kuban River in the suburbs of Armavir, Krasnodar Krai is characterized by the fact that significant (more than 3 m) fluctuations in inter-level and flood flow of rare frequency are observed on this section of the river. Realizing anti-landslide and bank strengthening measures it is necessary to provide for both a reduction in general and local erosion of the left bank and the drainage of groundwater and surface from the anthropogenically developed area adjacent to the right slope of the river Kuban. The purpose of this research is to substantiate the stability of the right slope of the Kuban River in the vicinity of the city of Armavir, Krasnodar Krai, where initial collapses are already taking place in connection with the construction of residential buildings in the immediate vicinity of the bank and the development of general and local erosion of the right bank of the river. The calculation is carried out according to several methods for the basic and special load combinations. These calculations are necessary to substantiate landslide and bank protection measures on the right bank of the Kuban River.

Temporal variability of saturated hydraulic conductivity on a typical black soil slope of northeast China

Saturated hydraulic conductivity (Ks) is highly variable in both space and time. Compared to its spatial variability, however, the temporal Ks variability has rarely been studied or taken into account in the hydrological modelling. The objectives were to characterize the slope-scale temporal variability of Ks and to diagnose the primary factors regulating Ks variation during the growing season. In the black soil region of northeast China, a typical slope farmland dominated by silt loam was selected and divided into five sections with respect to soil erosion. Soil samples were collected in each section at approximately every 3 weeks during the maize growing season, and Ks, bulk density (BD), land surface roughness, wet-aggregate stability (WAS), soil organic carbon content (SOC), clay and sand contents (SAND) were investigated. Mainly owing to root growth, precipitation and agricultural management, strong temporal variability of Ks was observed in each of the five sections, as the corresponding coefficients of variation all exceeded 35 %. Using the redundancy analysis (RDA) and classical correlation analyses, the primary variables controlling Ks distribution varied among sections, i.e., precipitation (P) and SAND in the erosive section and BD in the others. The predominance of BD was also manifested when performing RDA and structural equation modelling (SEM) over the entire slope covering all five sections.The other significant factors included SAND, SOC, P and WAS, in the decreasing order of direct path coefficient. In addition, these factors also indirectly affected Ks through their influence on BD and/or other factors. These findings demonstrate the strong temporal variability of Ks throughout the maize growing season and intricate interactions of Ks with related factors, and have important implications for hydrological modelling and agricultural production in the black soil region of northeast China and other similar regions.

Three-dimensional evaluation of dentopalatal changes after rapid maxillary expansion in growing children

In growing children with transverse malocclusion problems, various types of rapid maxillary expanders (RMEs) have been effectively used in skeletal and dental expansions. We evaluated 3-dimensional dentopalatal changes in growing children who underwent maxillary expansion using RMEs and bonded RMEs. We investigated dentopalatal changes in 20 patients treated with bonded RMEs, 19 with RMEs, and 38 control patients. Dental plaster models before and after expansion were scanned 3-dimensionally and superimposed to evaluate transverse expansion, expansion ratio, angular expansion, and palatal expansion height ratio. Using bonded RMEs, similar anterior and posterior dental expansions were achieved with an efficiency of 69%-76% (expansion ratio), and palatal soft-tissue expansion occurred more apically in the posterior area (palatal expansion height ratio, 1.00) than in the anterior area (palatal expansion height ratio, 0.64). Using RMEs, a larger posterior dental expansion was achieved, with an efficiency of 106%-117% (expansion ratio), than anterior dental expansion (55%-60%), and palatal soft-tissue expansion occurred more apically in the posterior area (palatal expansion height ratio, 0.99) than anterior area (palatal expansion height ratio, 0.23). Dental expansions in the anterior and posterior areas were similar using bonded RMEs, whereas the posterior dental expansions were larger than those of the anterior area using RMEs. The entire palatal soft-tissue slope expanded in the posterior area, whereas the occlusal part expanded inthe anterior area using RMEs and bonded RMEs.

Coupled stability of offshore wind monopile foundations and submarine slopes under periodic loads

Long-term cyclic loading on offshore wind monopiles will lead to a decrease in the mechanical properties of the seabed near the monopile's foundation, therefore, causing instability of the submarine slope and the monopile foundation. To capture the accumulation strain caused by high cycle numbers and plastic deformation of seabed sands, the high cycle accumulation (HCA) model is complied with Mohr-Coulomb constitutive models. The shear strength reduction (SSR) method is used to obtain the safety factor of submarine slopes. The coupled numerical model simulates a 6 MW offshore monopile foundation with a single periodic lateral load applied on the monopile at the sea level, which represents concentrated wind and wave loads in storm conditions. The results show that the plastic zones begin to form at the monopile foundation, then extends towards the slope toe and slope top, and eventually across the entire slope, leading to slope instability. In this process, the safety factor of the slope is significantly reduced with each stage of the process. It was found that both the sharp changes of load amplitude and large average load also decreases the safety factors. Moreover, at the beginning of the monopile installation, the safety factor will increase by nearly 10%, but it will drop by nearly 30% due to long-term periodic lateral loads. Therefore, these have important implications for the installation of monopile foundations for offshore wind turbines (OWTs) since the slopes we consider are within the range of slopes at planned sites for OWTs. An increase in monopile diameter and embedded depth can enhance the overall slope stability. However, an increase in embedded depth could potentially instigate more extensive seabed landslides despite enhancing overall stability.

Centennial scale temporal responses of soil magnetic susceptibility and spatial variation to human cultivation on hillslopes in Northeast China

Soil loss is a significant environmental issue that causes soil degradation and threatens national food security in the black soil region of Northeast China. The magnetic susceptibility (MS) technique is a promising method for evaluating soil loss and estimating soil redistribution. In this study, undisturbed soil samples were selected from four typical black soil cropland slopes with 110a, 60a, 30a, and 20a cultivated durations at 10 cm intervals from the surface to a depth of 50 cm to measure soil MS. Based on measurable magnetic indexes, a quantitative relationship between MS and cultivation duration was constructed. The results indicated that: (1) The MS showed an approximate trend, namely 110a < 60a < 20a < 30a < 0a, the longer the sloping land was cultivated, the smaller the MS. (2) The reduction rate of χlf on the surface and underlying soil ranged from 1.57 to 3.27 and was also enhanced in the topsoil. (3) The relative difference value of MS among cultivation durations were greater at the lower slope than at the upper and middle slopes for all selected slopes; however, all positions became nearly constant after 50a of cultivation; (4) MS values substantially correlated in power function with cultivation duration on the entire slope and on three slope positions with r2 values from 0.50 to 0.86 and root mean square error values from 0.21 to 0.41. Soil MS in croplands varied with cultivation duration and was directly proportional to the increase in cultivation duration, which was used to establish soil redistribution and erosion patterns. The results of this study demonstrate that MS is a credible index for quantifying soil loss during continuous tillage at the centennial scale.