Safety Factor Of Slope Research Articles

High fill slope collapse: Stability evaluation based on finite element limit analyses

The stability of high fill slopes, which are typically encountered when building airports in mountainous areas, is influenced by complex geotechnical profiles, the fill strength, reinforcement, and rainfall conditions. On 3 October 2009, a catastrophic landslide occurred at Panzhihua Airport in Sichuan Province, China. Investigations indicated that this event was attributable to the presence of carbonaceous mudstone. However, the overall stability of the high fill slope in different construction phases has not been explored. In this study, finite element limit analyses were performed to examine the overall stability of a critical section of the high fill slope in 11 cases that differed in terms of their strength parameters, reinforcement, and rainfall conditions. The results indicate that the original slope stability determined using parameters based on the laboratory shear tests of fill materials was overestimated. Furthermore, the original slope reinforcement with three rows of stabilising piles was ineffective. The safety factor of the pile-reinforced slope was computed to be 0.95 when rainfall infiltration was considered, and the predicted slip surface coincided with the actual failure surface. Random field limit analyses of this slope indicated that the failure probability increased under the assumed rainfall infiltration conditions. Remediation plans could ensure stability against landslides. Overall, reliable parameters and methods must be used to calculate the stability of high fill slopes.

ANALISA GEOTEKNIK PADA TANAH LUNAK PADA LONGSORAN TANGGUL SUNGAI TUNTANG

Soil is a structure that chan be used as an embankment to prevent flooding in rivers and also sea eater tidal waves. Rivers are surface flows that are formed naturally or artificially and flow continuously to the sea. The condition of the soil on the river embankment is very unstable, which is directly adjacent to the irrigation canal, and the condition of the soil is very weak, causing the slope or embankment to collapse. The aim of this research is to determine soil stability analysis using the Plaxis Program Version 8.2, a geotechnical analysis program that can analyze soil stability using the finite element method which is capable of carrying out analyzes that can approximate actual behavior. Plaxis Version 8.2 provides various analyzes of displacement, stresses that occur in the soil, slope safety factors and others.The results of the analysis using the plaxis program Version 8.2 obtained maximum results. From the analysis of the Plaxis program on the construction of the Tuntang River Embankment landslide, it was found that in conditions where the soil was not repaired, it had a safety factor of 1.237 <1.5, which was smaller than the required safety factor, namely 1.5, so that the soil condition was unstable or a landslide. The condition of the soil in the channel was excavated and piled on top of the embankment, safety factor 1.105 < 1.5, this condition became worse due to the load on the embankment, the soil was strengthened by handling bamboo cerucuks to ensure that the soil did not experience movement at a distance of 0.5 m zig-zak. If a safety factor of 1.501 > 1.5, then with bamboo reinforcement the embankment can be overcome and not experience landslides.

Reliability analysis and uncertainty quantification of clay and sand slopes stability evaluated by Fellenius and Bishop’s simplified methods

Slope stabilities are mainly designed using the conventional design approach (CDA), where the limit equilibrium methods (LEMs) are performed. Fellenius and Bishop’s simplified methods are the two commonly LEMs adopted as recommended in most design codes. In the design process of CDA, the safety factors (FS) of slopes are checked with specified FSs to ensure stability. The CDA has inherent drawbacks because the design process does not account for uncertainties. Moreover, different LEMs using different assumptions to solve the safety factors might include some amount orders of approximations. This study conducts probabilistic analyses, i.e., Monte Carlo simulations (MCSs) and uncertainty quantification, to obtain insights into the two LEMs applied to clay and sand slopes. The results reveal that the reliability indexes (RIs) obtained from the two LEMs-based MCSs are relatively identical for the same slope. Concerning the soil types, however, the RIs of the clay slope are significantly lower than those estimated for the sand slope, regardless of the LEMs used. The uncertainty quantifications for the clay slopes reveal that the two LEMs have relatively similar bias factors regarding FSs. Nevertheless, using the Fellenius method underestimates the probabilistic safety (about 17% in terms of the mean of FSs) for the sand slope compared to Bishop’s simplified method. Moreover, the coefficients of variation of FS obtained from the clay slope are consistently larger than those from the sand slope. These observations imply that the clay slope is more uncertain than the sand slope, and the Fellenius method results in lower FSs for sand slopes. Therefore, the FSs specified in the design codes should be connected to the soil type or the LEMs used to achieve the same probabilistic safety levels. Finally, the equivalent FSs associated with a RI of 1.75 are derived for each slope and each LEM used.

Estimating the Slope Safety Factor Using Simple Kinematically Admissible Solutions.

Determining soil and water conditions is essential for designing the optimal foundation and safely transferring loads, including the self-weight of structures, to the ground. Excessive or uneven settlement of the subsoil may ultimately lead to the formation of structural cracks in buildings or the loss of slope stability. In extreme cases, the damage results in structural failure. This paper presents the application of simple solutions from plasticity theory-an evaluation of the upper and lower bounds of the exact solution-to estimate the slope safety factor. It is demonstrated that simple kinematically admissible mechanisms for the non-associated flow rule provide solutions are close to those obtained from the traditional Fellenius method.

A Numerical Method for Evaluating the Collapse of High-Steep Scarp Slopes Based on the Bonded Block Model–Discrete Fracture Network Model

Geotechnical engineering works in deep-incised valleys or open-pit mining areas often encounter high-steep scarp slopes with a slope angle greater than 75°. This type of slope directly threatens the safety of construction personnel, so assessing their stability is essential to ensure construction safety. The natural geometry of high-steep scarp slopes possesses complexity in terms of geometric morphology, structural features of rock mass, and occurrence mechanisms of collapse. There is little research and less emphasis on the evaluation of the collapse risk of high-steep scarp slopes. In particular, the fracture of intact rock or rock bridges is generally ignored in the analysis of collapse processes. A bonded block model (BBM)–discrete fracture network (DFN) coupling characterization model for the high-steep scarp slope is proposed based on a high-steep scarp slope containing dominant joint sets on the left bank of the dam site of the Huangzangsi Water Conservancy Project (Qinghai Province, China). By using the model, the complex geometric forms of the surface of the high-steep scarp slope are quantified, and the fracture process of falling rock masses as well as the controlling effect of dominant joints on the collapse of the scarp slope are revealed. A strength reduction method based on the BBM–DFN model is constructed, and the safety factor of the collapse-prone scarp slope is evaluated. The research results show that (1) the BBM–DFN model can be used to describe the local collapse process; (2) the occurrence of dominant joints plays an important part in controlling the collapse process; (3) there are differences in the safety factor of the scarp slope with different coupling methods; the collapse and failure modes also differ. For safety considerations, the safety factor of the scarp slope on the left bank of the dam site area is determined to be 1.85. The research findings can be used to guide the safety assessment of high-steep scarp slopes and the formulation of both collapse risk prevention and control measures to ensure construction safety in high-steep scarp slope areas.

A novel framework for ascertaining the safety factor and critical slip surface of 3D slopes reinforced with piles

The pile is a widely used reinforcement device in geotechnical engineering. For the present paper, we propose a new solution for calculating the safety factor (SF) of the 3D slope reinforced with piles and determining the critical slip surface (CSS) in the framework of minimum potential energy method. In particular, the mobilized shear stress on failure surface is determined by the equilibrium equation of forces operating on slip body. Meanwhile, the moving direction of 3D slope is equivalent to the direction of combined force acting on slip body. Additionally, the present method is combined with the genetic algorithm to identify CSS, and a novel criterion is proposed to locate the shape and position of CSS of a 3D slope using the total potential energy of landslide system as the objective function. The validation and comparison of results indicate that the SF obtained by the introduced method are close to reference solutions, and SF shows an obvious negative correlation with sliding direction (SD). It is also found that the support effect of pile is related to the pile location and the pile density. Meanwhile, the optimal pile position depends on the shape of failure surface and shear strength parameter of soil. Moreover, the effects of some parameters on SD of 3D slopes reinforced with piles are also studied.

An optimized model based on the gene expression programming method to estimate safety factor of rock slopes

An optimized model based on the gene expression programming method to estimate safety factor of rock slopes

Research on a Non-Synchronous Coordinated Reduction Method for Slopes Based on the Hoek–Brown Criterion and Acoustic Testing Technology

In the process of the evolution of rocky slope instability, the decay deterioration rate of cohesion c and internal friction angle φ are different, and there are also differences in the order and degree of their impact on slope stability; thus, it is of great theoretical value to propose a more practical calculation method for the reduction in slope degradation. This paper combines the Hoek–Brown criterion and an acoustic test method to estimate the mechanical parameters of slope rock mass; the correlative relationship within the double-strength parameter reduction was established by introducing advanced reduction steps (ARS), n, and correlation factor, λ, and a non-synchronous coordinated reduction (NSCR) method for the double parameters of slopes was proposed. Furthermore, methods for determining the comprehensive safety factor (CSF) of slopes during the coordinated reduction of double parameters are comparatively analyzed. The results of the application of engineering examples show that the strength of the slope rock mass is significantly reduced after several blast disturbances, and the equivalent cohesion is reduced from 1.05 MPa to 0.89 MPa, while the internal friction angle is reduced from 25.68° to 21.77°. The CSF calculated using the W. Yuan-2 method is closer to the results of the limit equilibrium method and is suitable for the calculation of the CSF of the NSCR of slopes. The slope CSFs show a trend of first increasing and then decreasing with the increase in n; FS = 3.349 when n = 50, with a relative error of only 8.1% compared to the results calculated using the limit equilibrium method. The NSCR method remediates the blindness of the traditional strength reduction method in double-parameter reduction and ensures that the reduction range of the internal friction angle is no lower than its residual strength limit value, making it practical and feasible for slope stability analysis.

Treatment measures for the creep–slip phase of landslides induced by twin tunnels

Tunnel excavation in geologically challenging areas can lead to slope instability and consequent landslides, which pose a serious threat to the integrity of the tunnel lining. To address this issue, a study was conducted to investigate the stability of the tunnel–landslide system using the finite-difference method (FDM) based on the Hanshankou tunnel of the Shaoguan–Xinfeng expressway in Guangdong province, China. A plane-strain model was used to examine the effect of various treatment measures on the system, and the strength reduction (incremental) method was employed to determine the range of initial slope safety factors applicable to different treatment measures, with the maximum shear strain increment serving as the criterion. The ‘anti-slip pile + anchor frame beam’ reinforcement system was found to be the most effective solution, reducing daily deformation by 60.1% after implementation. The results indicated that the pile–anchor reinforcement system can significantly mitigate landslide creep, and the corresponding treatment measures can be categorised based on the critical slope safety factor under different conditions.

Three-dimensional slope stability and anti-slide pile treatment of Zhangjiayao landslide under rainfall

PurposeTo solve the instability problem of Zhangjiayao landslide caused by rainfall, the internal mechanism of slope instability and the supporting effect of anti-slide piles are studied. The research results can provide theoretical basis for the prevention and control of loess landslides.Design/methodology/approachA three-dimensional finite element model of Zhangjiayao landslide is established by field geological survey, laboratory test and numerical simulation.FindingsThe results show that Zhangjiayao landslide is a loess-mudstone contact surface landslide, and rainfall leads to slope instability and traction landslide. The greater the rainfall intensity, the faster the pore water pressure of the slope increases and the faster the matrix suction decreases. The longer the rainfall duration, the greater the pore water pressure of the slope and the smaller the matrix suction. Anti-slide pile treatment can significantly improve slope stability. The slope safety factor increases with the increase of embedded depth of anti-slide pile and decreases with the increase of pile spacing.Originality/valueBased on the unsaturated soil seepage theory and finite element strength reduction method, the failure mechanism of Zhangjiayao landslide was revealed, and the anti-slide pile structure was optimized and designed based on the pile-soil interaction principle. The research results can provide theoretical basis for the treatment of loess landslides.HighlightsA three-dimensional finite element model of Zhangjiayao landslide is established.Zhangjiayao landslide is a loess-mudstone contact surface landslide.The toe of Zhangjiayao slope is first damaged by heavy rainfall, resulting in traction landslide.The deformation of Zhangjiayao slope is highly dependent on rainfall intensity and duration.The anti-slide pile can effectively control the continuous sliding of Zhangjiayao slope.

Application of Clay–rubber Mixtures for the Transportation Geotechnics—the Numerical Analysis

Abstract The use of waste materials (including rubber) in industry is one of the most important issues in terms of environmental protection. One of such applications is the use of soil–rubber mixtures in backfills or lower layers of embankments or road structures. The numerical analyses of the behavior of a clay–rubber mixture layer built into a road embankment are presented in this article. An elastic-perfectly plastic model with a Coulomb–Mohr yield surface was used in the finite element analysis. The parameters of soil–rubber mixtures adopted for the analysis were estimated on the basis of triaxial tests: monotonic (UU—unconsolidated undrained, and CU—consolidated undrained) and cyclic (CU) performed with low frequency (f = 0,001 Hz). The triaxial tests were carried out on mixtures of kaolin (K) and red clay (RC) with the addition of 1–5 mm rubber granulate (G) in the amount of 5–25% by weight. Numerical analyses included a static plate load test (VSS) of a layer made of a rubber–soil mixture built into the embankment and testing the stability of embankments using the c–ϕ strength reduction procedure. The results of laboratory tests confirm the necessity of testing soil–rubber mixtures each time before their use in embankments. The observed overall decrease in shear strength and stiffness of the tested material is variable and depends on the type of soil and the content of rubber waste. Satisfactory results of the analysis were obtained, both in terms of the values of layer stiffness modules and slope safety factors, which allows for the conclusion of the possibility of using soil–rubber mixtures (with the recommended granulate addition up to 30% by weight) in the layers of road embankments and (depending on the road class) in the lower layers of the pavement structure.

Stability Analysis of Strongly Weathered Muddy Slate Slopes Considering Softening Conditions of Water Immersion

To understand the stability of strongly weathered muddy slate slopes under water immersion effects, we obtained shear strength parameters of the weakly layered structures within this slate through direct shear tests. Point load tests were performed on in-site slate samples with varying water immersion durations to assess the water immersion’s softening impact on slate strength. Results highlight that muddy slate strength presents pronounced random variability, declining as water immersion duration increases. Drawing from shear strength parameters and the water immersion softening observed in laboratory and in-site tests, we formulated a numerical slope model that considers layered structures and water immersion conditions to evaluate slope stability. Numerical simulations suggest that the slate slope’s sliding surface, when layered, does not consistently form a basic circular arc or straight line. The slope safety factor (FOS) drops below 3, marking a notable decrease compared to a homogeneous slope (FOS = 3.22). In the model, multiple secondary sliding surfaces can emerge, leading to a sliding band with a specific thickness after introducing the random distribution of layer strength parameters. This further reduces the slope’s FOS to below 2.9. Water immersion makes slopes inclined to slide following the layered structure. If the dip angle of the slate’s layered structure is less steep than the slope’s dip angle, water immersion notably diminishes the FOS, which can dip to a minimum of 1.12.

Research on Stability of Dam Substation on Inclined Soft Soil Foundation Reinforced by Pile Foundation

For the construction of dam substations in coastal or mountainous areas, inclined soft soil foundations are very common. The unique engineering characteristics of inclined soft soil foundations can bring great difficulties to the construction of dam substations. In this paper, a pile foundation reinforcement dam slope model on an inclined soft soil foundation is established; the influence of different pile spacings, the pile length, and the soft soil foundation angle on the slope safety factor is studied; and the failure mechanism and stability of pile-supported dam slope foundation are analyzed. The research results indicate that pile foundation reinforcement can reduce the deformation of the dam slope foundation and improve stability. The pile layout has an important impact on stability, but a change in the pile spacing has little effect on the settlement surface at the bottom of the dam slope. The pile length has a significant impact on the safety of the slope within a certain range. The main stress area of the pile is 0–2 m above the pile, and its main deformation is the lateral deformation of the upper part of the pile. The research results of this article can provide parameter support and theoretical guidance for the construction of dam substations.

Relationship of Rock Geomechanics and Coal Mine Slope Safety Factor in South Sumatra Region, Indonesia

The research location is in the coal mine area South Sumatera region, Indonesia. This study aims to determine the geomechanics relationship of the rock which includes the physical properties of the rock: bulk density, and mechanical properties of the rock (shear strength), cohesion and internal shear angle to the safety factor of the coal mine slopes in the study area. Field research is carried out by observing and measuring directly in the field in the following ways: (a) Measuring slope azimuth, slope, dip direction and slope height and width using a measuring tape and geological compass. (b) Rock description based on physical characteristics (megascopic) and rock sampling for testing the physical and mechanical properties of the rock in the laboratory. (c) Observing the general condition of water from rock slopes (dry, moist, watery, wet or flowing) and slope vegetation. 2. Cohesion values and internal shear angles are secondary data obtained from PT. X which has been analyzed in the laboratory. 3. Slope modeling was carried out using Rocscience Slide software. This shows that the smaller the rock density value, the greater the rock cohesion value. The greater the cohesion value of the rock, the smaller the value of the shear angle on the rock. The smaller the value of the shear angle in the rock, the greater the value of the safety factor of the rock slope.

Optimizing slope safety factor prediction via stacking using sparrow search algorithm for multi-layer machine learning regression models

Optimizing slope safety factor prediction via stacking using sparrow search algorithm for multi-layer machine learning regression models

Engineering Geology and Slope Stability Analysis in Kendari-Andoolo Road Section, Wolasi District, South Konawe Regency, Southeast Sulawesi

This research presents the engineering geological features of the Kendari-Andoolo road section, Wolasi Sub-district, South Konawe Regency, Southeast Sulawesi, a vulnerable area for landslides. The slope factor of safety (FoS) was also determined using the limit equilibrium method on a single and overall slope. Hand auger drilling and Wenner-Schlumberger configuration geoelectric surveys were conducted to estimate the slope failure plane. The study area is composed of phyllite, mudstone, and sandstone. Discontinuities at the face of the slope are N45ºE and N105ºE shear fractures, N280ºE foliation, and N310ºE fault brecciation. The overburden is low plasticity organic silt (OL) with a density range of 16.92 kN/m3-18.01kN/m3 and a plasticity index of 8.64-10.57 (medium). The FoS values of the slopes assumed rotational and nonrotational slip failures. On a single slope assuming rotational failures, the FoS value was lower than the nonrotational plane but still above the threshold value. The critical FoS is on the rotational sliding plane on the overall slope model. The slope's landslide failure plane is the clay's boundary layers and weathered phyllite.

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.

Multiple reinforcement measures of flysch landslide.

This work is mainly intended to investigate the flysch landslide reinforcement measures used in the Smokovac-Mateševo section of the North-South Expressway project in Montenegro. Bentley's Plaxis software is used for a numerical analysis of sliding surface parameters of flysch strata in the limit equilibrium state. This study analyzes the slope safety factor for rreinforcement measures such as rock bolts, retaining walls, anti-sliding piles, slope unloading and bolt anchoring and obtains an optimal combination of reinforcement application for the flysch landslide. The effects of seismic action on complex stress and the discontinuous stress boundary conditions arising from various reinforcement measures on landslide stability are also examined. The measures applied in this paper can be used as a reference for flysch landslide reinforcement or other similar slope engineering measures.

Study on the Influence of Wet Backfilling in Open Pit on Slope Stability

The residual open pit left in the wake of open-pit mining poses significant safety hazards, with backfilling being an effective strategy to wholly eliminate these risks. The stability of the slope following wet backfilling, however, should not be overlooked. This paper examines the impact of the seepage field conditions and backfill height on the stability of open-pit slopes using a case study of cemented backfill in a specific open pit in Anhui Province. Moreover, it utilizes onsite research, Slide simulations, and similar simulation tests. The study findings suggest that as the height of the tailing solidification backfill increases, the safety factor of open-pit slopes gradually elevates. When the backfill height exceeds 10 m, all profiles of the studied open-air slope fulfill the stability prerequisites. Furthermore, when the solidification backfill reaches 20 m, all profiles of the studied open-pit slope satisfy the stability requirements. The research outcomes offer a methodology for mining corporations to avert slope instability and destruction, thereby providing effective safeguards for the extraction of scarce resources in mines.

Dynamic reliability analysis of three-dimensional slopes considering the spatial variability in soil parameters

Slopes are commonly a significant aspect of geotechnical engineering projects. The incorrect evaluation and prediction of slope stability can cause serious disasters when it experiences seismic activity, and reliability is the key index a slope’s dynamic state. Spatial variability is an inherent soil property and has an essential influence on the dynamic response of a slope body. However, in previous studies, soil was often described deterministically, and the interaction between the uncertainty and spatial dimensions was ignored. To fill this gap, in this paper, practical expressions for the cohesion and friction angle in each working condition are given to simulate spatial variability by a lognormal random field. Then, the finite element method and effective dynamic reliability calculation method are used to obtain the safety factor of a 3D slope. Finally, the generalized probability density evolution method is performed to obtained the probability density information of the dynamic slope response and judge the influence of the soil spatial variability probabilistically. Due to the spatial variability in soil, the probability density distribution under each condition is distributed in a large range and thus may not provide results that are much more dangerous than those of the deterministic simulation. Meanwhile, the friction angle is more sensitive than cohesion and shows stronger discreteness in the spatial variability. The change in the cross-correlation coefficient has a greater influence on reliability than the autocorrelation length. Consequently, the simplification of model slopes in dimension and variability could deviate the reliability results from actual dynamic responses, either overestimating or underestimating, resulting in incorrect designs and evaluations.