Top Of Slope Research Articles

MLF-PointNet++: A Multifeature-Assisted and Multilayer Fused Neural Network for LiDAR-UAS Point Cloud Classification in Estuarine Areas

LiDAR-unmanned aerial system (LiDAR-UAS) technology can accurately and efficiently obtain detailed and accurate three-dimensional spatial information of objects. The classification of objects in estuarine areas is highly important for management, planning, and ecosystem protection. Owing to the presence of slopes in estuarine areas, distinguishing between dense vegetation (lawns and trees) on slopes and the ground at the tops of slopes is difficult. In addition, the imbalance in the number of point clouds also poses a challenge for accurate classification directly from point cloud data. A multifeature-assisted and multilayer fused neural network (MLF-PointNet++) is proposed for LiDAR-UAS point cloud classification in estuarine areas. First, the 3D shape features that characterize the geometric characteristics of targets and the visible-band difference vegetation index (VDVI) that can characterize vegetation distribution are used as auxiliary features to enhance the distinguishability of dense vegetation (lawns and trees) on slopes and the ground at the tops of slopes. Second, to enhance the extraction of target spatial information and contextual relationships, the feature vectors output by different layers of set abstraction in the PointNet++ model are fused to form a combined feature vector that integrates low and high-level information. Finally, the focal loss function is adopted as the loss function in the MLF-PointNet++ model to reduce the effect of imbalance in the number of point clouds in each category on the classification accuracy. A classification evaluation was conducted using LiDAR-UAS data from the Moshui River estuarine area in Qingdao, China. The experimental results revealed that MLF-PointNet++ had an overall accuracy (OA), mean intersection over union (mIOU), kappa coefficient, precision, recall, and F1-score of 0.976, 0.913, 0.960, 0.953, 0.953, and 0.953, respectively, for object classification in the three representative areas, which were better than the corresponding values for the classification methods of random forest, BP neural network, Naive Bayes, PointNet, PointNet++, and RandLA-Net. The study results provide effective methodological support for the classification of objects in estuarine areas and offer a scientific basis for the sustainable development of these areas.

Progressive failure and quantitative stability analysis of rock slope with cross-type discrete fracture network using spring-based smoothed particle hydrodynamics method

The propagation and coalescence of discontinuous cross-type joints are often the primary drivers of rock slope failures. Due to the inherent randomness of these joints, identifying suitable methods to accurately characterize progressive failure and quantitatively assess the stability of slopes with cross-type joints is particularly challenging. To address this, a Discrete Fracture Network-Spring Based-Smoothed Particle Hydrodynamics (DFN-SB-SPH) method is proposed, which considers cross-type DFN generation, rock matrix heterogeneity, cracking, block contact, and deposition within a unified SPH framework. In this approach, damage and contact of blocks are achieved by introducing a fracture sign to enhance the kernel function and applying Newton's law to the damaged particles to realize the point to point contact. A uniaxial compression test on rock samples with double fissures is carried out to verify the accuracy of the proposed method. The influence of joint density, geometric parameters (i.e., trace length, dominate dip angle) of cross joints, and rock mass heterogeneity on the failure characteristics of RSCD are investigated. The results revealed that the DFN-SB-SPH model possesses robust capabilities for crack tracking, mass movement, and contact slipping along fracture surfaces. Moreover, DFN generation, heterogeneous characterization, shear and tensile fractures within a single SPH framework without mesh distortion are realized. Five typical failure modes calculated by DFN-SB-SPH are primarily determined by the combination of joint dip angles and trace lengths. Furthermore, the dip angle, trace length, joint density, and rock mass heterogeneity significantly alter the stability of RSCD with sensitivity coefficients for factor safety of 27.7 %, 44.6 %, 72.9 % and 35.0 %, respectively. Higher dominant dip angles (above 60°) lead to significantly longer run-out distances for RSCD compared to lower angles (below 30°) once instability occurs. The sudden rise in major principal stress at the slope's top and toe, along with the shift of tensile stress concentration towards the middle, predicts the stages of crack propagation and sliding in slope failure.

Multispectral Inversion of Citrus Multi-Slope Evapotranspiration by UAV Based on Modified RSEB Model

Evaptotranspiration (ETc) is a crucial link in the farmland water cycle process. To accurately obtain the citrus ETc in different slope positions, the METRIC, RSEB, and FAO Penman–Monteith (P-M) models were constructed based on unmanned aerial vehicle (UAV) multispectral images to invert the ETc values. The ETc of citrus calculated by the P-M model was used as a reference standard, and the accuracy of the ETc inversion was evaluated by the METRIC model and the RSEB model. The results showed that the R2, RMSE, and SE of the METRIC model and the RSEB model were 0.396 and 0.486, 4.940 and 3.010, and 4.570 and 2.090, respectively, indicating a higher accuracy of the RSEB model for inverting the ETc values. Furthermore, the accuracy of the RSEB model could be improved by introducing the optimal correction coefficient (after correction: RMSE = 1.470, SE = 0.003). Based on the modified RSEB model, the ETc values of the citrus in different slope positions were obtained. We also found that the middle slope ETc > the top slope ETc > the bottom slope ETc, indicating that the slope position indeed affected the citrus ETc. This research provides a favorable framework for the ETc inversion, and the results are of theoretical and practical importance to realize crop water conservation.

Dry Deciduous Forests of the Poona District, Deccan, India

The deciduous vegetation grows in various ghats and hills in the Poona district. The present note describes the type from the Katraj ghats, on the south of Poona at a distance of 6 miles.The area consists of flat plateau at the top, eastern and western slopes and narrow valleys through which small rivulets flow during monsoons. The mountains are formed of trap rock, the strata of which dip towards east. Thus the eastern slopes are gentle with better developed soil but the western escarpments are steep comparatively dry with shallow soil. Seepage water is seen on eastern slope during monsoon. Alluvial soil deposits in the valley. The average rainfall is about 27".The following vegetation types are described:(I) Top of the plateau: They are mainly covered with Boswellia serrata which is regenerating profusely where biotic interference is excluded and the soil is dry shallow and gravelly.(II) The western slopes: These slopes bear a low type of forest. The following trees are common-Boswellia serrata, Lannea coromandelica, Diospyros montana and Largerstroemia parviflora. Shrubs-Acacia sp., Lantana camara, Zizyphus xylopyrus, Rhus mysorensis, Flacourtia, Cipadessa baccifera, Gymnosporia spinosa and Securinega sp.Herbs-Tridax procumbens, Leucas sp., Cocculus sp., Polyzygus tuberosus, Sida sp., Arisaema sp., Desmodium sp., Acanthospermum hispidum, Celosia sp. etc.This vegetation is also affected adversely by the biotic interference since lopping, coppicing and grazing are prevalent.(III) Eastern slope (top portion) ; It bears a community of Boswellia serrata-Diospyros montana-Lannea coromandelica on dry shallow and rocky soil. The commonest shrubs are Acacia sp., Zizyphus xylopyrus, Lantana camara, Cryptolepis buchanani, Woodfordia fruticosa, Cissuspallida and Securinega sp.The common herbaceous vegetation consists ot Locculus sp., Leucas sp., Tridax procumbens, Curculigo sp., Polyzygus tuberosus, etc.(IV) Eastern slope (lower portion): It bears a community of Tectona grandis-Lannea coromandelica-Diospyros-Boswellia serrata.Teak and Lannea coromandelica are predominant on the alluvial deposits towards the valley and higher up. Diospyros sp. and Boswellia become prominent in dry trap soil. Diospyros on alluvial soils is heavily infected by Viscum. But incidence of the parasite decreases in trees which are growing on dry trap rocks elsewhere in the area. Commonest shrubs in the community are Acacia sp., Clerodendron serratum, Zizyphus xylopyrus, Cissus pallida and Lantana camara. Commonest herbs are Leucas sp., Tridax procumbens, Hemidesmus indicus, Curcuma montana, Cocculus sp., Polyzygus tuberosus, Trichodesma sp., Crotalaria sp., Indigofera sp., Celosia sp., Aerva javanica, etc.Various stages of succession are seen in the area and regeneration of teak, Boswellta, Lagerstroemia. Lannea is common on different types of soils.

Study on the Effect and Enhancement of Near-Natural Integrated Plant Positioning Configuration in the Hilly Gully Region, China

The establishment of protective forests plays a crucial role in mitigating soil erosion on slopes within hilly and gully regions. However, in practical applications, the configuration of protective forests on slopes is intricate and diverse, and the suitability and rationality of different configuration patterns for various slope sections have not been thoroughly investigated. This study focuses on a 40-year-old artificial protective forest, examining 16 different configuration patterns on the top, middle, and lower slopes. It compares the growth conditions, community structure stability, and characteristics of the saturated soil’s hydraulic conductivity. The findings indicate that the top slope should be identified as a critical area for slope protection. The optimal configuration for this area is the “tree + grass” pattern with a spacing of 5 m × 5 m, which promotes the optimal growth of tree species and effectively reduces the surface runoff of gravel particles ranging from 1 cm to 3 cm in diameter. On the middle slope, the “tree + shrub + grass” structure proves effective in slowing down the erosive force of slope runoff. The recommended spacing for trees is 5 m × 6 m, and for understory shrubs, it is 1 m × 6 m. This configuration pattern results in the most stable structure for the plant community and maximizes the water conservation potential of forest litter. By analyzing the characteristics of the saturated soil’s hydraulic conductivity, we find that the complexity of the plant configuration on the lower slopes is correlated with a greater coefficient of variation in the saturated soil’s hydraulic conductivity. Nevertheless, there is no significant difference in the average soil saturated hydraulic conductivity per unit area between the different configuration patterns. Consequently, the lower slope can rely on the natural recovery of herbaceous plants. The results of this research contribute valuable scientific and technical insights to the management of soil erosion in hilly and gully areas, both in China and around the world.

Effect of vegetation restoration type and topography on soil water storage and infiltration capacity in the Loess Plateau, China

Vegetation restoration effectively mitigates soil erosion and improves soil properties, but in drylands, it can lead to soil water scarcity and disrupt ecological balance. Until now, limited research has examined the combined effects of vegetation restoration type and topography on soil water and infiltration in the Loess Plateau of China. Here, we investigated soil water content (SWC), soil water storage (SWS), soil infiltration rates and related soil properties in typical forestland, shrubland, and grassland across five slope positions on steep slopes, and compared them with cropland. The results indicated that vegetation restoration significantly decreased SWS compared to cropland. Across the entire 0–500 cm depth, reductions were observed at 30.9 %, 33.2 %, and 20.8 % for forestland, shrubland, and grassland, respectively, with forestland and shrubland demonstrating a more pronounced decrease, particularly in deeper soil layers. Shrubland had the lowest SWS on the upper, middle, and top slopes, while forestland showed the lowest SWS on the lower and foot slopes. In terms of infiltration, vegetation restoration generally increased steady infiltration rate but resulted in reduced initial and mean infiltration rates (except for shrubland). Shrubland had the highest infiltration rates, followed by forestland, while grassland had the lowest rates. Soil infiltration rates decreased gradually along the slope, indicating that the impact of vegetation restoration on soil infiltration improvement weakened with lower slope positions. Vegetation restoration type had a stronger direct and total effects on infiltration than slope position. Yet, the indirect influence of slope position through clay content and SWC outweighed that of vegetation restoration type. Our findings highlight the comprehensive assessment of the eco-hydrological effects of vegetation restoration is essential for identifying suitable species and designing optimal spatial distribution, ultimately maximizing the ecological benefits of the restoration. These insights can offer valuable guidance for ecological restoration and land management in fragile dryland ecosystems.

Study on progressive failure mode of surrounding rock of shallow buried bias tunnel considering strain-softening characteristics

Mountain tunnels portal often have to pass through slope terrain unavoidably, thus forming a shallow buried bias tunnel. During the construction of shallow buried bias tunnel, disasters such as slope sliding and tunnel collapse frequently occur. The failure mode of surrounding rock obtained by current research is based on the limit equilibrium theory, which cannot reflect the progressive failure characteristics of the surrounding rock of shallow buried bias tunnel. In order to reveal the failure mechanism of the gradual instability of surrounding rock of shallow buried bias tunnel, the problem of gradual failure of the surrounding rock is reduced to an elastic–plastic analysis problem for surrounding rock considering the strain-softening characteristics. Based on the elastic–plastic analysis of the failure process of shallow buried bias tunnel, MATLAB was used to compile a program to read the finite-difference calculation result file, extract the effective information such as shear strain and tensile strain at the center point of each unit, and establish the analysis method of the progressive failure mode of shallow buried bias tunnel. The reliability of the method proposed was verified by comparing the failure process of the model test with the development process of shear strain increment. Under the condition of no support, the formation mechanism of failure plane of surrounding rock on both sides of shallow buried bias tunnel is different. The shallow buried side is the shear failure plane formed by the collapse of surrounding rock, while the deep buried side of the tunnel is the shear failure plane formed by the collapse of surrounding rock and slope sliding. Under the conditions of excavation and support, the failure plane of the shallow buried bias tunnel can be divided into three parts according to the formation sequence and reasons. The part I is the failure plane, which is formed by active shear under the influence of tunnel excavation. The part II is the failure plane formed by tensile crack of slope top. The part III is the failure plane formed by passive shear under the push of the soil in the upper part of the slope.

Insights on seasonal solifluction processes in warm permafrost Arctic landscape using a dense monitoring approach across adjacent hillslopes

Solifluction processes in the Arctic are highly complex, introducing uncertainties in estimating current and future soil carbon storage and fluxes, and assessment of hillslope and infrastructure stability. This study aims to enhance our understanding of triggers and drivers of soil movement of permafrost-affected hillslopes in the Arctic. To achieve this, we established an extensive soil deformation and temperature sensor network, covering 48 locations across multiple hillslopes within a 1 km2 watershed on the Seward Peninsula, AK. We report depth-resolved measurements down to 1.8 m depth for May to September 2022, a period conducive to soil movement due to deepening thaw layers and frequent rain events. Over this period, surface movements of up to 334 mm were recorded. In general, these movements occur close to the thawing front, and are initiated as thawing reaches depths of 0.4–0.75 m. The largest movements were observed at the top of the south-east facing slope, where soil temperatures are cold (mean annual soil temperatures averaging −1.13 °C) and slopes are steeper than 15°. Our analysis highlights three primary factors influencing movements: slope angle, soil thermal conditions, and thaw depth. The latter two significantly impact the generation of pore water pressures at the thaw–freeze interface. Specifically, soil thermal conditions govern the liquid water content, while thaw depth influences both the height of the water column and, consequently, the pressure at the thawing front. These factors affect soil properties, such as cohesion and internal friction angle, which are crucial determinants of slope stability. This underscores the significance of a precise understanding of subsurface thermal conditions, including spatial and temporal variability in soil temperature and thaw depth, when assessing and predicting slope instabilities. Based on our observations, we developed a factor of safety proxy that consistently falls below the triggering threshold for all probes exhibiting displacements exceeding 50 mm. This study offers novel insights into patterns and triggers of hillslope movements in the Arctic and provides a venue to evaluate their impact on soil redistribution.

A multifactorial study of mass movement in the hilly and gully Loess Plateau based on intensive field surveys and remote sensing techniques

Mass movements, driven by various non-linearly correlated factors, exhibit high randomness, posing vast difficulties for field observations and subsequent investigations into the underlying mechanisms. In this study 157 mass movement incidents (including collapses, slump and spalling) and their primary influencing factors were surveyed in a small catchment of the hilly and gully Loess Plateau, China, through intensive field investigations and remote sensing techniques. The spatial pattern of mass movement and its relation with the influencing factors were assessed, while the relative impact of different factors was studied using the canonical correlation analysis. Results showed that 1) Mass movements predominantly occurred on gully slopes steeper than 70°. Collapses were the main type of mass movement, accounting for 87.9 % of the number of samples. 2) With regard to the impact of individual factors, rainstorms (rainfall intensity >50 mm day−1) significantly enhanced the occurrence frequency, erosion area and erosion volume of mass movement. The occurrence frequency and erosion area / volume were highest at a soil dry bulk density of 1.34 g cm−3 and 1.54 g cm−3, respectively. Mass movement occurred most frequently on unvegetated or unrooted gully slopes, where the resisting effect of vegetation on mass movement was absent. Gully slopes with smooth rather than rugged profiles were also found to be typical areas of mass movement. The occurrence frequency of mass movement decreased with the elevated topographic wetness index (TWI) and distance to slope top and increased with the distance to channels. 3) For the relative impact of different factors, rainfall and shear strength were key factors facilitating and resisting the onset of mass movement, respectively, while topography exerted the greatest influence on the erosion area and volume. This study revealed the relative influence of different factors on occurrence and scale of mass movement, providing a useful reference for modelling and control of the problem.

Influence of the anchor angle on the seismic response of anchored stabilizing piles: Centrifuge modeling tests

Anchored stabilizing piles (ASPs) are widely used as excavation support systems in slope anti-seismic reinforcement engineering. In this study, a set of centrifuge contrast tests were designed and used to explore the influence of the anchor angle on the seismic response of the system to further deepen the research on the seismic response of ASPs. To this end, the effects of two anchor cable arrangement angles on the slope seismic response, lateral dynamic earth pressure, anchor cable axial force, and pile dynamic moment were compared and analyzed. The results show that changing the angle of anchor cable arrangement can reduce the degree of seismic damage to the slope and the settlement of the slope top (up to a maximum reduction of 77%) and, to some extent, reduce the amplification of acceleration inside the slope. Under seismic action, the different angles of anchor cables do not change the distribution of seismic earth pressure and peak dynamic bending moment but can significantly affect their magnitude and growth rate. The appropriate arrangement angle of the anchor cable can effectively slow the growth of the internal force of the anchor cable and reduce the risk of anchor cable failure. The anchor cable is not the main load-bearing component in an ASP but the primary component that limits pile displacement. Overall, this study can provide a detailed data foundation for subsequent centrifuge comparative tests and parameter analysis.

Variables related to the stability of soil macro and microaggregates of a toposequence in the Brazil south region

Soil aggregates are the basic components of soil structure, being important to its environmental properties and functions. The objective of this study was to investigate the variables related to the aggregates stability, measured by the method of dry and wet sieving and by applying ultrasound energy, in three different soils of a toposequence in southern Brazil. The study was performed in three soils sampled in the city of Pinhais / PR: i) Oxisol (top slope); Ii) Inceptisol (medium third) and; Iii) Gleisol (floodplain). The aggregates stability was determined measured by the method of dry and wet sieving (macroaggregates), as well as by applying ultrasound energy (microaggregate). The results were correlated with soil chemical, physical and mineralogical attributes. The organic matter, the low crystallinity Fe oxides and kaolinite were the most important variables for the profile structural stability. In turn, the soil texture did not show a direct relation with soil aggregation. The Gleisol show highest structural stability, followed by Oxisol and Inceptisol.

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.

Creep characteristics and discharge optimization of overlying river inner dump: A case study of Yuanbaoshan open-pit coal mine in China

Overlying river can accelerate the creep of the inner dump, so to master the creep characteristics of the overlying river can provide a theoretical basis for mine safety and discharge optimization. Taking the overlying river inner dump of Yuanbaoshan open-pit coal Mine in China as the research object, a design scheme is proposed to divide it into rolling zone and non-rolling zone. Based on the creep model obtained by in-situ deformation monitoring and laboratory rheological test, the creep evolution law and deformation of overlying channel after soil discharge, slope morphology and advancing position are simulated and analyzed. The results showed that the creep variable in the (non-) rolling zone had a nonlinear upward trend with time, and the initial upward trend was large. The maximum vertical and horizontal creep in the rolling area was located in the middle and upper part of the rolling line, while the maximum vertical and horizontal creep in the dump was located in the middle and upper part of the non-rolling area, respectively. The post-construction settlement and horizontal discharging increased with the increase of the discharge height, and the convergence creep of the top ten years after construction increased approximately linearly with the decrease of the distance from the shoulder of the inner dump. The rolled sand and gravel backfill belonged to the foundation of uniform settlement deformation in general, and the change of slope shape had little effect on the deformation of the slope top in the rolled area. The geoglage elongation in the dam area met the requirements. On the premise of ensuring the stability of the dump, the slope angle of the inner dump can be appropriately increased to increase the capacity of the inner dump. The research results can provide guidance for the construction of inner dump in open pit.

Analysis of the stability of cracked soil slopes using a numerical model incorporating stochastic theory

Desiccation crack is a prevalent natural phenomenon that plays a significant role in the stability of soil slopes. In this study, a hydromechanical coupling model incorporating a layer of stochastic cracks is developed for analyzing cracked soil slopes. To properly consider the anisotropy and spatial variability of desiccation cracks, three crack indices are generated through cross-correlated random fields via Cholesky decomposition. The seepage and mechanical behavior of a cracked slope are analyzed by adjusting stochastic parameters and rainfall conditions. Applied to the Ningzhen Mountains area in China, the model investigates the stability of slopes under various annual meteorological conditions. The results indicate that neglecting the spatial variability of cracked layer properties can lead to inaccurate assessments of instability risks at the base and water accumulation at the top of slopes. During heavy rainfall, slopes with deeper (up to 5 m) and weaker cracked layers often show a roughly planar sliding morphology. Moreover, the uncertainties in crack depth have the most pronounced influence on the uncertainties of the slope stability, more than horizontal permeability or crack aperture. The average crack aperture’s influence on slope stability depends on the relationship between crack infiltration rate and rainfall intensity.

Spatiotemporal heterogeneity of soil available nitrogen during freeze–thaw cycles in a watershed: A 3‐year investigation

AbstractThe spatial pattern of soil available nitrogen (AN) is the key reference for farmland fertilization however, it is still unclear how freeze–thaw cycles (FTC) altered the spatiotemporal heterogeneity of AN at the watershed scale. In this study, the geostatistical, traditional analysis and structural equation models were used to detect how topography, land management, and soil properties influence the spatiotemporal heterogeneity of AN in both before‐ and after FTCs of Mollisols of a watershed in Northeast China for three consecutive years. The results showed that AN decreased in >88% of areas of the watershed after FTCs, and the mean value significantly decreased by >7.6% (>10.4 mg kg−1) in 0–20 cm soil depth during 2016–2017 years and 2017–2018 years. The AN distribution, especially in the surface soil layer, tended to be aggregated after FTCs. The AN decreased in the areas near the areas of top slope position, while it tended to increase in areas of downslope position covered by forest although the total N decreased here after FTCs. The AN‐change (ANbefore FTCs minus ANafter FTCs) influenced by land use types was greater than slope steepness. The slope aspect as the key factor combined with slope steepness, slope position, and previous crops influenced the spatiotemporal heterogeneity of AN‐change after FTCs. The higher content of AN before FTCs accelerated more N loss during FTCs, and this process was mainly influenced by soil pH, nitrogen (N), and phosphorus. The N loss (5.7%) did not significantly alter the AN‐change after FTCs in the watershed. Generally, the spatial heterogeneity of AN‐change was mainly influenced by topography, land management, and soil properties (before FTCs) during FTCs in the watershed. In order to sustain a high level of AN, the mediation of N transformation and both vertical‐ and horizontal migration, caused by the dynamics of soil water potential and snowmelt erosion should be considered during FTCs.

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.

Bearing capacity and failure mechanism of strip footings lying on slopes subjected to various rainfall patterns and intensities

Footing on slope is a prevalent construction encountered in geotechnical engineering, and its safety is receiving increased attention. A natural rainfall event will inevitably have adverse influences on the stability and bearing capacity of strip footings lying on slopes; however, the conventional practice to simulate the rainfall is realized by varying the soil moisture content and the actual rainfall characteristics cannot be fully reflected. As a result, the finite element (FE) software ABAQUS is employed in this study to model the temporally varying rainfall, and the bearing capacity, as well as failure mode of the strip footing placed at the top of slopes, is estimated accordingly. A series of FE analyses are carried out to quantify the influences of rainfall pattern, rainfall intensity, soil strength properties (i.e., effective cohesion c′ and effective friction angle φ′) and several geometric parameters associated with the location of embedded footing with B in width, such as the edge distance ratio L/B and the embedded depth ratio D/B. Results show that the bearing capacity will be decreased and the failure mode evidently changes under rainfall condition. Moreover, it is noted that the rainfall pattern produces less substantial impact on the bearing capacity and failure mode, compared with the rainfall intensity.

Conserving the threatened woody vegetation on dune slopes: Monitoring the decline and designing adaptive strategies for restoration

The southern tip of the Thal desert in Pakistan harbors the remnants of the original tropical thorn forest, amounting to two percent, which covered the province of Punjab a hundred years ago. In the past three decades, there has been a progressive decline in woody species cover on dunes, which is directly related to the increase in population in the surrounding area. Stabilized and destabilized dunes were subjectively selected followed by quantification of cover and diversity of woody species on the top and lower slopes. Dunes closely resembling the overall cover were grouped to suggest corresponding restoration measures. The results suggest that trends of decrease in cover and diversity of woody species were evident in the upper slopes of some stabilized dunes having less than 50% cover. The destabilized dunes with less than 20% cover are highly vulnerable to erosion. A general trend observed among dunes was that with a decrease in the cover of upper slopes, there is a decrease in the cover on lower slopes. The number of destabilized dunes is increasing without effective restoration measures against the prevailing trends of disturbances. Ranking dunes on the basis of cover could help in proposing simple restoration measures as a first step towards developing an understanding of designing adaptive strategies to restore the woody cover.

Stability of loess high-fill slope based on monitored soil moisture changes

This paper aims to assess the influence of moisture content changes during rainfall on the stability of loess high-fill slopes by taking a loess high-fill slope in Lanzhou City as an example. First, according to the moisture content monitoring data collected from a slope online monitoring system, direct shear tests were performed on soil samples of different moisture content to determine the relationship between the shear strength parameters and moisture content. Next, a coupled hydro-mechanical model with soil shear strength related to moisture content was established and used to analyze 16 working conditions with various rainfall intensities and durations for two cases: shear strength parameters from the site exploration report and those from this study. Finally, the results from the two cases were compared regarding the changes in stresses and displacements after rainfall infiltration to analyze the influence of moisture content on the stability of loess high-fill slopes. The conclusions are as follows: (1) Segmental relationship equations of cohesion and angle of internal friction were established for loess with various moisture content. (2) Under the conditions of different rainfall intensities, significant differences were observed in the trends of slope stress and displacement changes. (3) The slope displacement occurred in the shallow soil layer within about 12.5 m from the slope top, and the plastic strain concentrated in the soil layer within about 6 m from the slope top. (4) The results of slope stability analyses based on moisture content monitoring data are more in line with the observed.

Numerical simulation study on erosion collapse failure mechanism of cemented conglomerate accumulation

PurposeCemented conglomerate accumulation is a weak and heterogeneous medium that occurs in western China. It consists mainly of argillaceous cement that loses strength rapidly upon contact with water, leading to collapse instability failure. Its deformation failure mechanism is complex and poorly understood. In this paper, the erosion failure mechanism of cemented conglomerate accumulation is investigated.Design/methodology/approachThe collapse failure process after erosion of the slope foot for typical cemented conglomerate accumulation is studied based on field investigation using the particle discrete element method. And how the medium composition, slope angle and cementation degree influence the failure mode and process of the cemented conglomerate accumulation is examined.FindingsThe foot erosion of slope induces a tensile failure that typically manifests as “erosion at the foot of slope – tensile cracking at the back edge of slope top – integral collapse.” The collapse failure is more likely to occur when the cemented conglomerate accumulation has a higher rock content, a steeper slope angle or a weaker cementation degree.Originality/valueA model based on rigid blocks and disk particles to simulate the cemented conglomerate accumulation is developed. It shows that the hydraulic erosion at the foot of the slope resulted in a different failure mechanism than that of general slopes. The results can inform the stability management, disaster prevention and mitigation of similar slopes.