Earth Slopes Research Articles

Stability Analysis of Anchor-Reinforced Soil Slopes with Taylor’s Stability Chart

The stability of earth slopes can be enhanced by introducing an anchoring system. The factor of safety of an anchor-reinforced slope is one of the essential items required to evaluate stability. This parameter can be predicted using limit equilibrium and numerical approaches by relevant software. Taylor’s stability chart has been frequently used to estimate the factor of safety of an unreinforced homogeneous cohesive-frictional soil slope. An analytical expression was developed in this study based on the friction circle method by which the factor of safety of anchor-reinforced slopes can be predicted using Taylor’s chart. The anchor-reinforced slope considered in the analysis consisted of homogeneous cohesive-frictional soil. The analyses were carried out considering different slope inclinations, anchor loads, anchor orientations, and slip circles. An illustrative example explained the procedure for finding the factor of safety and showed how the developed method could be used by practicing engineers. A comparison between the factor of safety estimated by Taylor’s chart and the limit equilibrium method using SLIDE indicates a good agreement.

Comparative Analysis for Slope Stability by Using Machine Learning Methods

Earth slopes’ stability analysis is a key task in geotechnical engineering that provides a detailed view of the slope conditions used to implement appropriate stabilizations. In the stability analysis process, calculating the safety factor (F.S) plays an essential part in the stability assessment, which guarantees operations’ success. Providing accurate and reliable F.S can be used to improve the stability analysis procedure as well as stabilizations. In this regard, researchers used computational intelligent methodologies to reach highly accurate F.S calculations. The presented study focused on the F.S estimation process and attempted to provide a comparative analysis based on computational intelligence and machine learning methods. In this regard, the well-known multilayer perceptron (MLP), decision tree (DT), support vector machines (SVM), and random forest (RF) learning algorithms were used to predict/calculate F.S for the earth slopes. These machine learning classifiers have a strong capability predict the F.S under certain conditions for slope failures and uncertainties. These models were implemented on a dataset containing 100 earth slopes’ stabilities, recorded based on F.S from various locations in the provinces of Fars, Isfahan, and Tehran in Iran, which were randomly divided into the training and testing datasets. These predictive models were validated by Janbu’s limit equilibrium analysis method (LEM) and GeoStudio commercial software. Regarding the study’s results, MLP (accuracy = 0.901/precision = 0.90) provides more accurate results to predict the F.S than other classifiers, with good agreement with LEM results. The SVM algorithm follows MLP (accuracy = 0.873/precision = 0.85). Regarding the estimated loss function, MLP obtained a 0.29 average loss in the F.S prediction process, which is the lowest rate. The SVM, DT, and RF obtained 0.41, 0.62, and 0.45 losses, respectively. This article tried to fill the gap in traditional analysis procedures based on advanced procedures in slope stability assessments.

Comparison of test results to determine the parameters of soil strength to ensure the stability of earth slopes

The content of large soil fractions in soils complicates the experimental part of the research, but, the modeling method makes it possible to determine the effect of soil filler on slope stability.
 The article presents the results of experimental study of the strength of coarse-clastic soils with different percentages of large fractions of gravelly soil (up to 20 mm) and aggregate (up to 5 mm) in the study of slope stability. The studies were carried out on three types of experimental equipment, which confirms the reliability of the results obtained. Recommendations are given for applying the values of the strength characteristics of coarse-grained soils in calculating the stability of slopes.
 The results of the tests are carried out in a tray and shear testing devices. Mixture of soil fractions from 2 mm to 50 mm. Purpose of the tests is to determine the actual parameters of soil strength j and C, taking into account the effect of impurities on the stability of slopes.
 Reliability of the results confirmed the comparability of the results of previous tests. Tray allows for testing models of slopes composed of mixtures of sand fractions from 2 mm to 20 mm. Model sizes slopes are defined relative to the size tray. Tray dimensions ‑ length 1400 mm, width 500 mm, height 1000 mm.
 The design of the shear device allows to investigate coarse soils of different factions. The diameter of the fractions were tested for shear device area of 100 sm2 is from 2 mm to 20 mm.
 The diameter of the fractions were tested for shear device area of 1000 sm2 ‑ from 5 mm to 50 mm. The experiments were performed in the laboratory "Geotechnics in Construction" in KazGASA.

Probabilistic Slope Stability Evaluation Using Hybrid Metaheuristic Approach

This paper develops an efficient evolutionary hybrid optimization technique based on the adaptive salp swarm algorithm (ASSA) and pattern search (PS) for the reliability evaluation of earth slopes considering spatial variability of soils under the framework of the limit equilibrium method. In the ASSA, to improve the salp swarm approach's exploration ability while also avoiding premature convergence, two new equations for the leaders' and followers' position updating procedure are introduced. The proposed hybrid algorithm (ASSPS) benefits from the effective global search ability of the adaptive salp swarm algorithm as well as the powerful local search capability of the pattern search method. The suggested ASSPS algorithm's efficiency is confirmed using mathematical test functions, and its findings are compared with the standard salp swarm algorithm as well as some efficient optimization techniques. Then, the ASSPS is applied for calculation of the lowest safety factor and reliability index of earth slopes. The safety factor is formulated using the Morgenstern and Price approach and the advanced first-order second-moment (AFOSM) method is implemented for the reliability calculation model. The ASSPS's efficacy for the evaluation of the minimum reliability index of slopes is investigated by considering two literature-based case studies. The numerical experiments demonstrate that the new algorithm could generate better optimal solutions and significantly outperform other methods in the literature.

Earth slope stability evaluation subjected to earthquake loading using chaotic sperm swarm optimization

Earth slope stability evaluation subjected to earthquake loading using chaotic sperm swarm optimization

Minimum Safety Factor Evaluation of Slopes Using Hybrid Chaotic Sand Cat and Pattern Search Approach

This study developed an efficient evolutionary hybrid optimization technique based on chaotic sand cat optimization (CSCO) and pattern search (PS) for the evaluation of the minimum safety factor of earth slopes under static and earthquake loading conditions. To improve the sand cat optimization approach’s exploration ability, while also avoiding premature convergence, the chaotic sequence was implemented. The proposed hybrid algorithm (CSCPS) benefits from the effective global search ability of the chaotic sand cat optimization, as well as the powerful local search capability of the pattern search method. The suggested CSCPS algorithm’s efficiency was confirmed by using mathematical test functions, and its findings were compared with standard SCO, as well as some efficient optimization techniques. Then the CSCPS was applied for the calculation of the minimum safety factors of the earth slope exposed to both static and seismic loads, and the objective function was modeled based on the Morgenstern–Price limit equilibrium method, along with the pseudo-static approach. The CSCPS’s efficacy for the evaluation of the minimum safety factor of slopes was investigated by considering two case studies from the literature. The numerical experiments demonstrate that the new algorithm could generate better optimal solutions via calculating lower values of safety factors by up to 10% compared with some other methods in the literature. Furthermore, the results show that, through an increase in the acceleration coefficient to 0.1 and 0.2, the factor of safety decreased by 19% and 32%, respectively.

Grassholme Reservoir: northern embankment stabilisation works

Grassholme Reservoir is a large impounding reservoir commissioned in 1914 in the Lunedale Valley of County Durham. The most recent statutory inspection in 2016 resulted in a ‘Measures in the Interests of Safety’ (MIOS) recommendation to investigate and rectify a suspected unstable embankment slope between the reservoir and an adjacent watercourse. In November 2021, the stability works were completed to the satisfaction of the qualified civil engineer and the MIOS recommendation discharged. A total of around 20 000 m3 of selected clay fill was used to construct a reinforced earth slope with an interlocking concrete block wall at the toe. As a consequence of stabilising the northern embankment, the adjacent Carl Beck has been diverted through a buried pipe until realignment in spring 2022. The aim of this paper is to summarise and illustrate the various complexities associated with stabilising the northern embankment and realigning the existing watercourse, such as mitigating the loss of ancient woodland, managing complex ecological constraints and mitigating land access delays from the offset.

Effects of spatial variability of soil properties and ground motion characteristics on permanent displacements of slopes

The seismic performance of earth slopes is a problem of great importance in geotechnical earthquake engineering associated with various sources of uncertainty. This research investigates the effects of two important causes of such uncertainty: (a) the spatial variability of soil properties and (b) the variability of the temporal and frequency characteristics of the earthquake excitation. The former is investigated based on a series of detailed dynamic numerical simulations using stationary random fields of both cross-correlated and spatially autocorrelated soil properties. The latter is explored by conducting incremental dynamic analysis at various levels of excitation intensity using (a) a total of forty historic earthquake and synthetic records, modified to match the Eurocode 8 design spectra for rock sites, and (b) thirty original historic earthquake records. The results demonstrate the significant effect of the spatial variability of soil properties on the permanent slope displacements. Moreover, they show that the effect of the uncertainty associated with the variability in the temporal and frequency characteristics of excitations is more important compared to the effect of the spatial variability of soil properties.

A fully nonlinear coupled seismic displacement model for earth slope with multiple slip surfaces

For slopes consist of layered soil profiles, the earthquake-induced deformation may occur in various locations and the slope may exhibit a set of plastic slip surfaces. In this paper, a fully nonlinear coupled sliding displacement model is presented to evaluate the seismic performance of slopes considering multiple slip surfaces. Both the nonlinear behavior in the cyclic response of soils and the sliding process at different slip surfaces are described based on a multi-degree-of freedom lumped parameter model. The nonlinear hysteretic soil response is represented by the hyperbolic stress-strain curve and the Masing rules. The yield coefficients obtained from pseudo-static analysis of slopes are used to represent the limit shear strength at each slip surface. The dynamic equations of motion of the system in the cases of various sliding modes at shallow, median and deep slip surfaces are derived, and the sliding displacements at different locations of slopes during the earthquake motion can be computed. The code is validated by degrading the developed model to the conventional seismic site response analysis and seismic sliding analysis models. The sliding displacement at different slip surfaces and the stress-strain results of soil are analyzed to highlight the coupling effects of the plastic shear deformations at different slip surfaces and the cyclic responses of soil. The comparisons of displacement results for different slopes are then performed between the proposed model and the linear soil model and the single sliding analysis model. Finally, an application to the Bainigou slope is presented to evaluate the seismic performance of the slope.

Experimental Study on the Effect of Hemp Fiber on Mechanical Properties of Stabilized Clayey Soil

ABSTRACT Clayey soils have fine particles and contain clay minerals. Therefore, they are sensitive to water and cause stability problems. Nowadays, soil stabilization is an accepted method to resolve the problem of stability. In this study, hemp fiber was used as an additive material for stabilization of clayey soil. The use of fibers in the stabilization of clayey soils is becoming widespread, particularly with regard to applications involving the stabilization or reinforcement of shallow steep earth slopes and steep cover systems for landfills. In these applications, the use of natural fibers use is very important due to their environmentally friendly properties. Hemp legally planted in different countries is used in several industries, such as paper, textiles, clothing, biodegradable plastics, construction, body products, health food, and biofuel. In this study, hemp fiber was preferred because of its natural and environmentally friendly properties. To observe the effect of hemp fiber on the compressive strength of clayey soil material, the unconfined compression tests and shear box tests were carried out under laboratory conditions. The experimental results showed that hemp fiber is effective on the compressive strength of clayey soils. As a result, hemp fiber can be used successfully in clayey soil stabilization as an environmentally friendly material.

Multi-slip surfaces searching method for earth slope with weak interlayer based on local maximum shear strain increment

To perfect the present slip surface searching method, by which only one slip surface can be obtained, existing the phenomenon of slip surface identification omission or errors when applied to the slope with multiple potential slip surfaces, a multi-slip surfaces searching method based on local maximum shear strain increment is proposed. Firstly, the strength reduction method is adopted to calculate the contour of shear strain increment on critical state of slope. Then, feature points on slip surfaces are extracted based on the local maximum shear strain increment, and multiple feature point clusters on the slip surface are obtained by the DBSCAN algorithm. Finally, Kalman filters (KF) and Rauch-Tung-Strieber Smoother (RTSS) are used to smooth the slip surface feature point clusters one by one. Numerical examples show that the proposed method can accurately locate multiple potential slip surfaces, providing a theoretical foundation for accurately determining the potential slip surfaces in the slope. On this basis, the influence of grid density on extraction results of feature points and weak interlayer parameters on the distribution of slip surfaces are further discussed, which provides a reference for the location and shape research of potential slip surfaces in slope engineering.

Flood risk analysis using gis-based analytical hierarchy process: a case study of Bitlis Province

Floods are the most common natural disasters on earth. Population growth with global warming and climate changes increases the impact of floods on people every year. Combating natural disasters such as floods is possible with effective disaster management. An effective disaster management can only be possible with a comprehensive risk analysis. Flood risks depend on many factors such as precipitation, flow, earth slope, soil structure, and population density. A holistic flood risk analysis considering all these factors will provide a more effective disaster management. This study focuses on an assessment of flood hazard analysis in Bitlis province of Turkey using analytical hierarchy method which is a multi-parameter modeling technique. Flood hazard zones were mapped according to the weight of the selected factor by using geographic information system. It is concluded that while especially the south-western regions are exposed to high flood risk due to high stream density and precipitation, the high slope and rugged nature of this region restrict the risk mainly to the vicinity of low elevation streams and high population regions.

Limit state line-based seismic stability charts for homogeneous earth slopes

The stability charts for static and pseudo-static (PS) stability analysis of homogenous slopes have been widely used for preliminary design work. Based on the concept of a graphical stability chart, where the factor of safety (FoS) is simply a ratio between two lines, this study presents a series of improved stability charts based on limit equilibrium PS analysis of a wide range of homogeneous slope models with inclination angles varying from 10° to 60°, and considering both horizontal and vertical seismic loads. The limit state lines (LSL) are presented, and their mathematical expressions are obtained from extensive regression analyses. The LSL-based graphical stability charts’ solutions are proposed for PS stability analysis of homogeneous slopes with any given combinations of physical parameters. The proposed charts show very good performance for rapidly obtaining the PS FoSs; the calculation errors are generally within 10%. In addition, the developed charts can intuitively reflect the possible slope failure modes and their state transformation with the variations of soil strength, slope inclination and seismic coefficient. Thus, the proposed chart solutions may serve as a promising tool for practising engineers to estimate the FoS of homogenous slopes considering seismic loading effects.

Multi-Source Information Fusion Correlation Analysis of Bedrock Deterioration on Slopes Under Leaching Erosion

To explore the effect of leaching erosion on the deterioration mechanism of ionic rare earth slope bedrock. The E-TOPSIS method and fuzzy grey correlation method were used to fuse and analyze the multi-source heterogeneous information such as porosity, pH, mass, volume, density, P-wave and characteristic strength of bedrock specimens. The dominant response parameters of bedrock deterioration of slopes under leaching erosion were obtained, and the multi-source information fusion correlation analysis model was established. The results show that compared with the basic physical parameters of bedrock, the influence of leaching erosion on the pore structure of bedrock is more significant; the pore space and leaching solution pH show obvious dominant responsiveness in the E-TOPSIS analysis with soaking duration. Basically, from the results of fuzzy grey correlation analysis, the micropore of bedrock specimens continued to increase after the decrease in the early stage of soaking, and the porosity varied significantly; the micropore and porosity of bedrock specimens had the highest correlation with the characteristic strength of bedrock, followed by the pH of leaching solution.

In Situ Experimental Study of Natural Diatomaceous Earth Slopes under Alternating Dry and Wet Conditions

Very few studies have focused on diatomaceous earth slopes along high-speed railways, and the special properties of diatomaceous earth under alternating dry and wet conditions are unknown. This paper studies diatomaceous earth in the Shengzhou area, through which the newly built Hangzhou–Taizhou high-speed railway passes, and the basic physical and hydraulic properties of diatomaceous earth are analyzed by indoor test methods. A convenient, efficient, and controllable high-speed railway slope artificial rainfall simulation system is designed, and in situ comprehensive monitoring and fissure observation are performed on site to analyze the changes in various diatomaceous soil slope parameters under rainfall infiltration, and to explore the cracking mechanisms of diatomaceous earth under alternating dry and wet conditions. The results indicate extremely poor hydrophysical properties of diatomaceous earth in the Shengzhou area; the disintegration resistance index values of natural diatomaceous earth samples subjected to dry and wet cycles are 1.8–5.6%, and the disintegration is strong. Comprehensive indoor tests and water content monitoring show that natural diatomaceous earth has no obvious influence when it contacts water, but it disintegrates and cracks under alternating dry and wet conditions. The horizontal displacement of both slope types mainly occurs within 0.75–2.75 m of the surface layer, indicating shallow surface sliding; after testing, natural slope crack widths of diatomaceous earth reach 10–25 mm, and their depths reach 40–60 cm. To guarantee safety during high-speed railway engineering construction, implementing proper protection for diatomaceous earth slopes is recommended.

Stability and Deformation Responses of Earth Slopes Subjected to Multiple Natural and Manmade Hazards

Multiple hazards such as rainfall, earthquake, and excavation may occur simultaneously, and the stability (factor of safety) and deformation (movement) behaviors must be investigated to prevent loss of life and properties. In this study, the stability and deformation behaviors of earth slopes subjected to the individual and simultaneous occurrence of these events are investigated using a coupled Geotechnical–Hydrological finite-element method (FEM). First, the finite-element model was validated against a case history and a widely used limit-equilibrium method (LEM) considering site-specific soil properties and rainfall records. The shape and the size of the critical failure surface obtained from the field investigation coincided well with those calculated using FEM and LEM. Also, the predicted onset of slope failure (after eight days of rainfall) coincided well with the real-time occurrence of the slope failure. The validated finite-element model was then used to predict the stability and deformation responses of earth slopes subjected to several possible scenarios, including individual and simultaneous occurrences of these events. The rainfall–excavation scenario indicated that the slope would have failed two days before the recorded time if the slope had a vertical cut width of 4.25 m. The rainfall–earthquake hazard scenario caused the slope to move horizontally by 799 mm. The parametric study conducted by varying the friction angle of the slope soil by ± one standard deviation (STD) with 10% covariance showed that the slope would have failed one day later and two days prior to the mean friction angle, respectively, when subjected to rainfall. Also, varying the friction angle by +1 STD and −1 STD failed the slope for 0.5 m above and 0.4 m below the cut width for the slope with mean friction angle when subjected to excavation, respectively. Further, the percent increase in the horizontal movement of the slope soil with friction angle by +1 STD and −1 STD compared to mean friction angle was 56% and 18%, respectively, when subjected to earthquake.

Importance of seismic wave frequency in FEM-based dynamic stress and displacement calculations of the earth slope

Abstract Reliable assessment of earthen dams’ stability and tailing storage facilities widely used in the mining industry is challenging, particularly under seismic load conditions. In this paper, we propose to take into account the effect of the dominant frequency of seismic load on the stability assessment of tailing/earthen dams. The calculations are performed by finite element modelling (FEM) with the Mohr–Coulomb failure criteria. To separate the frequency content from other dynamic parameters describing the seismic wave, synthetic waveforms with identical amplitude and attenuation characteristics, but differing spectral characteristics have been used. The analysis has been performed for three different slope angles and two scenarios of seismic wave propagation. Consequently, the changes of total displacement and shear stresses depending on the frequencies have been determined and clearly show that lower frequencies cause higher stress levels and displacement. Finally, the response surface methodology has been applied to determine how different parameters affect the slope stability under dynamic load conditions. Overall, this study is a first step to improve the existing methods to assess slope stability when considering seismic load.

Seismic Analysis of Earth Slope Using a Novel Sequential Hybrid Optimization Algorithm

One of the most important topics in geotechnical engineering is seismic analysis of the earth slope. In this study, a pseudo-static limit equilibrium approach is applied for the slope stability evaluation under earthquake loading based on the Morgenstern–Price method for the general shape of the slip surface. In this approach, the minimum factor of safety corresponding to the critical failure surface should be investigated and it is a complex optimization problem. This paper proposed an effective sequential hybrid optimization algorithm based on the tunicate swarm algorithm (TSA) and pattern search (PS) for seismic slope stability analysis. The proposed method employs the global search ability of TSA and the local search ability of PS. The performance of the new CTSA-PS algorithm is investigated using a set of benchmark test functions and the results are compared with the standard TSA and some other methods from the literature. In addition, two case studies from the literature are considered to evaluate the efficiency of the proposed CTSA-PS for seismic slope stability analysis. The numerical investigations show that the new approach may provide better optimal solutions and outperform previous methods.

Beneficial role of batter pile in slope under infinite uniform surcharge loading

Batter pile is used to find a more effective way to stabilize the slope. Thus, these two questions “where is the optimal location of batter piles on earth slopes?” and “which inclination angle is most beneficial for pile in earth slopes?” arise. The numerical simulation was conducted to investigate the performance of slope reinforced by batter pile. The surcharge loading, inclination angle and pile location were varied while keeping geometry of the slope and the soil property constant. The surcharge loading was applied on the slope crest by steps. The inclination angle varied from 0° to 20°. The pile was placed at middle-down (MD), middle (MI), middle-upper (MU) and upper (UP) part of slope, respectively. A finite length of batter pile (10 m) was adopted, and the pile toe was free. Four series of numerical models were proceeded to search the optimum location and inclination angle for pile, one that provided maximum lateral resistance. By analyzing the slope deformation and pile bending moment, the effects of position and inclination angle of pile were determined. The following conclusions could be drawn: (1) The surcharge loading on the slope crest will influence the deformation of slope remarkably. Both the lateral displacement and settlement increases simultaneously with the raise of loading. (2) The lateral displacement and settlement of slope vary as the pile location moves from the crest to the toe. The slope of UP condition has the the minimum lateral displacement, following by MI, MD and MU condition. The ranking of settlement is same with the lateral displacement. That is to say, the UP condition is the best location for piled slope, followed by MI condition. (3) The batter pile is beneficial for slope engineering, which can not only reduce the deformation of slope, but also decrease the bending moment exerted on pile shaft. The inclination angle should be in a reasonable range, a relatively small inclination angle could not fully utilize the potential capacity of batter pile, while exaggerated inclination degree is not befitting for construction. The inclination angle of 15° is an optimal choice for batter pile in slope. (4) The inclination angle has mutual effect with the pile location, they should be considered synchronously. For comprehensive consideration, UP 10°, UP 15°, MI 15° and MI 20° are preferred options for the piled earth slope when subjected to surcharge loading.

Hydro-mechanical behaviour of soil experiencing seepage erosion under cyclic hydraulic gradient

Numerous incidents and failures of earth slopes, dykes, levees and embankment dams are caused by internal erosion. At a time of global climate change, rapid pore-water pressure changes in soil masses are frequently induced by extreme rainfall, storm surges, waves, flash floods and so on. Under such complex cyclic hydraulic conditions, the soil erodibility, hydraulic conductivity and subsequent stress–strain behaviour may differ from those under the monotonic seepage condition, and are still poorly understood. In this study, preliminary laboratory tests have been conducted to investigate the development of internal erosion and changes in hydraulic conductivity under one-way cyclic seepage, and the post-erosion stress–strain behaviour. Representative internally stable and unstable soils were tested. The effects of mean hydraulic gradient and cyclic gradient amplitude were investigated in detail. Results show that the erosion development is significantly influenced by both the initial grain size distribution and the pattern of imposed cyclic hydraulic gradient. The cyclic seepage promotes the loss of fine particles and leads to larger hydraulic conductivity. For the internally unstable soil, the eroded soil mass and hydraulic conductivity increased significantly with increasing cyclic gradient amplitude. Nevertheless, the internally stable soil experienced a small amount of particle loss, even under large cyclic gradients. For both types of soil, a larger cyclic gradient amplitude corresponds to a stronger post-erosion contractive shearing behaviour and a smaller critical friction angle.