Safety Factor Of Slope Stability Research Articles

Slope Stability Analysis of Rockfill Embankments Considering Stress-Dependent Spatial Variability in Friction Angle of Granular Materials

Slope stability is a major safety concern of rockfill embankments. Since rockfills are incohesive materials, only friction angle is considered as a shear strength parameter in the slope stability analysis of rockfill embankments. Recently, it was found that confining pressure can significantly affect the mean value and variance of the friction angle of rockfills. Since the confining pressure spatially varies within a rockfill embankment, the effect of stress-dependent spatial variability in the friction angle of rockfills should be investigated for slope stability evaluation of rockfill embankments. In the framework of the Limit Equilibrium Method (LEM), an approach is proposed for the slope stability analysis of rockfill embankments considering the stress-dependent spatial variability in the friction angle. The safety factors of slope stability are computed with variable values of the friction angle at the bases of slices which are determined by the stress-dependent mean value and variance of the friction angle of rockfills. The slope stability of a homogeneous rockfill embankment is analyzed to illustrate the proposed approach, and a parametric analysis is carried out to explore the effect of variation in the parameters of the variance function of friction angle on slope stability. The illustrative example demonstrates that the stress-dependent spatial variability of friction angle along the slip surface is obvious and is affected by the location of the slip surface and the loading condition. The effects of the stress-dependent spatial variability of the friction angle on the slope stability of high rockfill embankments should be considered.

Static and Pseudo Static Analysis of Embankment Slope Stability of Bener Dam, Purworejo Regency, Central Java

The Bener Dam is considered as one of the largest rock-fill dams in Indonesia. This dam will impact the inundation area of three main villages in the Wonosobo and Purworejo regency. Since this zoned embankment dam consists of rock-fill and the core material, the stability of the dam slope has to be done to ensure that the dam is stable against any failures including the seismic effects. Moreover, the seismic coefficient in the study area in the seismic analysis of the large dam slope is needed to be used in the analysis which is not yet done from the previous studies. This paper presents the analysis of the embankment slope stability of the Bener dam under static condition and pseudo static condition. The analysis takes into account the end stage of construction, the steady-state stage, and rapid drawdown stage. The results of utilizing the Finite Element Method to analyse the slope stability demonstrates that the dam embankment slopes are stable under static and seismic stress conditions in all the reservoir condition stages. After applying the seismic loading, the result of safety factor of slope stability is reduced while the rapid drawdown stage has the lowest safety factor.

Mechanisms of slope instability induced by two-hole oversized tunnels with small clearances underneath

The double-tunnels crossing potential landslides are gradually developing towards smaller clearances and larger cross-sections. The disturbance of the tunnel construction is very likely to cause slope instability, tunnel damage, and other natural disasters. In the paper, model tests and numerical analysis are applied to investigate the instability mechanism of landslides caused by double-tunnels with oversized sections orthogonally beneath, based on the Shaoxin High-Speed Hanshankou Tunnel. The mechanism of tunnel-induced landslides is obtained and the stability factor of safety is modified by strength reduction and parametric analysis. The results indicate the following: The superimposed effect of double-hole excavation and the disturbance of surrounding rock caused by super-large cross-section excavation are the two main reasons for the landslide in Hanshankou Tunnel. The degree of influence of various factors on the stability of the tunnel-landslide mass is: section size > buried depth > clear distance > construction method > support parameters. It is recommended to use the formula F=α1α2α3Fst to modify the slope stability safety factor.

Experimental Study on Repairing the Mechanical Characteristics of Oil-Contaminated Silty Clay in Ancient Dike with Modified Lime Mortar.

Flood-controlled ancient dikes play a significant role in flood control and have received widespread attention as historical and cultural symbols. Flood-controlled ancient dikes often undergo disasters, and research on their repair is receiving increasing attention from experts and scholars. This article studies the control of seepage and bank slope instability in flood-controlled ancient dikes. Starting from the repair of ancient dike materials, three types of work are carried out: a test of soil's mechanical properties, finite element numerical simulation, and repair technology research. The research results show that the soil of the ancient dike site has hardened after being contaminated with waste oil from catering. The strength index of the ancient dike soil decreases and shows brittleness when the water content is 15% and the oil content exceeds 6%. The strength index and permeability coefficient of oil-contaminated soil improved using modified lime mortar (MLM), which was achieved using the method of MLM to repair oil contaminated soil. When the MLM content was 10% and the oil content was 6%, the friction angle of the soil sample reached its maximum value. When the MLM content was the same, the higher the density of the soil sample, the greater the friction angle and cohesion and the smaller the permeability coefficient. Establishing a finite element numerical model, through comparative analysis, it was found that after MLM remediation of oil-contaminated soil, the extreme hydraulic gradient of the ancient dike decreased by 31.3%, and the extreme safety factor of the bank slope stability increased by 31.2%. MLM pressure grouting technology was used to improve the soil during the remediation of contaminated soil at the ancient dike site. Through on-site drilling inspection, the effective diffusion radius of MLM grouting was obtained, and the plane layout and grouting depth of MLM pressure grouting were determined. The on-site water injection permeability test showed that using MLM pressure grouting technology can effectively repair oil-contaminated soil in the ancient dike while reducing the permeability coefficient by 8-15%.

Stability analysis of rock slope under Sujiaba overpass in Chongqing City based on kinematic and numeric methods

Rock slopes have the characteristics of complex geological conditions, weak structural surface development, steep slope, and great damage. In this study, the Sujiaba overpass slope in Chongqing was selected as the evaluation object, and the main stability evaluation methods of rock slope were analyzed. Combined with the special geological conditions and geographical location of the rock slope, through a geological survey, the slope was qualitatively analyzed based on the stereographic projection method, and the slope stability safety factor was calculated by using the finite element strength reduction method. FLAC3D was used to simulate the initial stress state of the unstable rock mass, the limit state stability of the unstable rock mass before bolt support, and the stability after bolt support. The simulation results show that the stability coefficients of selected unstable rock masses W1, W2, W6, and W7 under the limit state before bolt support are, respectively, 1.22, 1.80, 5.90, and 2.10. Unstable rock masses separate from the parent rock, causing a large displacement due to their instability and downward sliding. After bolt support, stability coefficients for those four unstable rock masses are 1.60, 2.40, 8.60, and 3.20, respectively. Under the same reduction coefficient, rock masses are stable and the displacement is small. The results show that the calculation results of the initial stress state of the rock slope are consistent with the theoretical understanding and field investigation. After the implementation of bolt support, the anti-sliding stability of unstable rock is obviously improved. The research results have important scientific guiding significance and practical value for revealing the failure mechanism of rock slope and analyzing the stability of unstable rock mass.

Updating Active Deformation Inventory Maps in Mining Areas by Integrating InSAR and LiDAR Datasets

Slope failures, subsidence, earthworks, consolidation of waste dumps, and erosion are typical active deformation processes that pose a significant hazard in current and abandoned mining areas, given their considerable potential to produce damage and affect the population at large. This work proves the potential of exploiting space-borne InSAR and airborne LiDAR techniques, combined with data inferred through a simple slope stability geotechnical model, to obtain and update inventory maps of active deformations in mining areas. The proposed approach is illustrated by analyzing the region of Sierra de Cartagena-La Union (Murcia), a mountainous mining area in southeast Spain. Firstly, we processed Sentinel-1 InSAR imagery acquired both in ascending and descending orbits covering the period from October 2016 to November 2021. The obtained ascending and descending deformation velocities were then separately post-processed to semi-automatically generate two active deformation areas (ADA) maps by using ADATool. Subsequently, the PS-InSAR LOS displacements of the ascending and descending tracks were decomposed into vertical and east-west components. Complementarily, open-access, and non-customized LiDAR point clouds were used to analyze surface changes and movements. Furthermore, a slope stability safety factor (SF) map was obtained over the study area adopting a simple infinite slope stability model. Finally, the InSAR-derived maps, the LiDAR-derived map, and the SF map were integrated to update a previously published landslides’ inventory map and to perform a preliminary classification of the different active deformation areas with the support of optical images and a geological map. Complementarily, a level of activity index is defined to state the reliability of the detected ADA. A total of 28, 19, 5, and 12 ADAs were identified through ascending, descending, horizontal, and vertical InSAR datasets, respectively, and 58 ADAs from the LiDAR change detection map. The subsequent preliminary classification of the ADA enabled the identification of eight areas of consolidation of waste dumps, 11 zones in which earthworks were performed, three areas affected by erosion processes, 17 landslides, two mining subsidence zone, seven areas affected by compound processes, and 23 possible false positive ADAs. The results highlight the effectiveness of these two remote sensing techniques (i.e., InSAR and LiDAR) in conjunction with simple geotechnical models and with the support of orthophotos and geological information to update inventory maps of active deformation areas in mining zones.

Slope stability analysis during an earthquake in flow-slide affected area of Jono Oge

On September 28th, 2018, the earthquake with a moment magnitude (Mw) 7.5 due to strike-slip Palu-Koro Fault in Central Sulawesi caused a major geological failure. In the Jono Oge area, the earthquake-induced liquefaction and flow-slide occurred on relatively flat ground with an average slope of 2%. In this paper, the safety factor for slope stability analysis was determined by shear strength reduction caused by the earthquake at the potentially liquefied soil layer, varying peak ground acceleration values, and groundwater level conditions. This analysis evaluated the potential of ground movement occurrence in Jono Oge with the condition of soil layer pre and post the Palu-Donggala earthquake that happened in 2018 using GeoStudio Slope/W geotechnical software. The analysis was conducted on the cross-section of the soil layer based on three boreholes incorporating standard penetration test (SPT) data on the study area. The analysis results showed ground movement potential because of the seismic loads and groundwater level conditions. The lower the safety factor of slope stability, the higher the ground movement potential in flow-slide affected area. This ground movement potential could trigger the occurrence of flow-slide in Jono Oge area.

Freeze-Thaw Effect on Riverbank Stability

The stability of riverbanks in cold regions is affected by the freeze-thaw action. The freeze-thaw process causes changes in the moisture content, friction angle, and cohesiveness of the bank material. Together with the freeze-thaw effect, seepage pressure influenced by the changing water levels, and the bank slope are the key factors affecting bank stability. A limit equilibrium bank stability model considering the infiltration water pressure effect is developed and applied to the Shisifenzi section of Inner Mongolia reach of the Yellow River. Laboratory tests of field samples with moisture contents of 15%, 18%, 21%, and saturated showed that the freeze-thaw action reduced the degree of saturation by 34.37 %, 30.71%, 32.48%, and 46.23%, respectively, accompanied by reductions in the internal friction angles by 1.78%, 2.74%, 6.33%, and 5.32%. These changes resulted in a 24.35% to 29.13% reduction in the safety factor of bank stability. Together with seasonal variations in the water levels the field data showed that the bank stability safety factor in the study site increases gradually through the melting period, dry period, wet period, flooding period, and low flow period. The slope stability safety factor increases with the stage of the river but decreases with the groundwater level.

SEEPAGE MODELING IN EMBANKMENT DAMS WITH VARIOUS SUB SOIL CHARACTERISTICS

The embankment dam has the advantage that it can be built in all sub-base conditions although poor topography, but the weakness is seepage, so research on seepage is needed. This study uses numerical modelling with the GeoStudio program: SEEP/W and SLOPE/W. The data used is data from the Tugu Dam, Trenggalek, while the subbase data used five soil types, namely clay, silty clay, silt, silty sand, and sand. This research simulation is divided into two; the first simulation is the condition of the soil characteristics remains with the water level increasing every 5 meters from the base elevation of the dam to below the floodwater level;. In contrast, the second simulation is the condition of the water level elevation remains constant, but the soil characteristics change. Each simulation will be checked for seepage discharge and soil stability. The first simulation results show that seepage discharge and water level elevation have a logarithmic correlation with R 2 > 0.75. The largest seepage discharge of 1,90 x 10 -3 m 3 /s is sand soil, while the smallest is clay soil of 1,47 x 10 -9 m 3 /s. The results of the second simulation show that the seepage discharge and saturated volumetric water content also have a logarithmic correlation, but some results cannot be used because they have an R 2 value < 0.75. From the two simulations, the seepage discharge that occurs is said to be safe because it is below the average annual runoff which is 1% of the 10-year re-flood discharge calculated using the Nakayasu Synthetic Unit Hydrograph (HSS) which is 5.99 m 3 /s, and the safety factor of slope stability is > 1.2 then the dam is considered stable.

Influence of Rainfall Infiltration on Stability of Granite Residual Soil High Slope

The seepage evolution characteristics and stability change rule of granite residual soil inside the high cutting slope under the action of rainfall infiltration were studied. Based on the saturated-unsaturated seepage theory, the numerical simulation of the rainwater infiltration path inside the granite residual soil slope was carried out under the condition of rainwater infiltration. The evolution characteristics of the seepage field of the granite residual soil cutting high slope under the condition of rainfall infiltration were revealed, and the influence of the rainwater infiltration on the stability of the granite residual soil slope was mainly studied. The research results show that with the accumulation of rainfall infiltration, the pore water pressure of the granite residual soil slope increases continuously, and the pore water pressure of the soil below the platform increases the fastest. With the increase in elevation, the water content of the slope presents a wave crest distribution. In the early stage of rainfall, the seepage velocity vector distribution on the slope surface is relatively uniform. In the middle stage of rainfall, the seepage velocity vector is the most dense at the platform, and the rainwater migration rate is accelerated. In the later stage of rainfall, the infiltrated rainwater at the slope angle of the first-level slope spreads to the surrounding area. With the continuous rainfall, the slope stability safety factor gradually decreased unevenly, and after the rainfall stopped, it gradually increased with the rainwater infiltration.

Searching Method of Critical Slip Surface of Slope Based on Improved Wolf Swarm Algorithm

Determining the critical sliding surface and calculating the safety factor of slope stability are the key problems of slope stability analysis. Firstly, according to the characteristics of the existing wolf swarm algorithm, an improved wolf swarm algorithm is proposed, which abandons the assumption of a circular sliding surface. Then, a multipoint spline curve is introduced to describe the shape of a slope sliding surface. The optimization of the curve can determine the critical slip surface of slope and avoid falling into the local optimum. This method is programmed and implemented in Python, and then, accuracy and reliability are verified through typical slope cases and engineering examples, and the sensitivity analysis of factors that have great influence is carried out. The research results show that the slope sliding surface search method based on the improved wolf swarm algorithm can effectively and quickly determine the critical sliding surface of the slope. Compared with traditional methods, it has higher convergence accuracy and reliability. It provides an effective method for slope stability analysis.

Effect of Slope on Landslide Potential at Kuranji Watershed

The Kuranji watershed is one of the largest watersheds in the city of Padang. Several landslides and floods have been reported in this area. Many factors cause landslides, both natural and non-natural factors. One of the natural factors that cause landslides is the topography/slope condition. The sloping/steep topography in the downstream area of the Kuranji watershed causes a high potential for landslides in this area. Landslides occur due to balance disturbances that cause the movement of soil and rock masses from a higher place to a lower place. Therefore, it is necessary to analyze slope stability to determine the effect of slope conditions on the potential for landslides. In this study, an analysis of the potential for slopes stability was carried out using the Ordinary Method of Slices. The analysis is carried out by making different slopes so that the value of the safety factor will be obtained from each slope. The slope variation used in this study is the ratio of height to slope width of 1:5, 1:4, 1:3, 1:2, 1:1, 1:0.5, 1:0.25. The results showed that the smaller the slope and the height of the slope, the more stable the slope will be, on the contrary, the larger the slope, the more unstable the slope. This can be assessed from the value safety factor (SF) of slope stability which is obtained from the calculation, which is getting smaller as the slope and height of the slope decrease.

Numerical Simulation of the Stability of a Cutting Slope and Study on Its Reinforcement Scheme

Analyzing the stability of the slope and studying the reinforcement scheme can reduce ecological disasters, improve the ecological environment, and protect people’s lives and property. In this paper, taking the left side slope of ZK100 + 860∼+975 cutting of the Huizhou‐Qingyuan section of the Shantou‐Zhanjiang Expressway as an example, based on the strength reduction method (SRM), the stability of the slope under different conditions (natural conditions, unsupported excavation conditions, rainstorm conditions, and reinforcement conditions) is analyzed by using finite element software. The results show that the slope was almost stable before excavation, and the safety factor of slope stability decreases due to excavation, so it is in an unstable state. Rainwater has a great influence on the stability of the slope. The damage to the slope is deepened, and the stability safety factor is decreased under the rainstorm condition. The stability safety factor of the slope has increased by 24.3% after the reinforcement of the anchor rod and anchor cable, and the slope is in a stable state. It can be seen that the anchor rod and anchor cable can effectively control the deformation of the slope and have a good reinforcement effect.

Analysis of Mechanical Properties and Slope Stability of Red Bed Soft Rock: A Case Study in Xinjiang Irrigation Diversion Channel

The channel slope in the red‐bed soft rock area is prone to instability and collapse due to the influence of the channel flow movement, rainfall, weathering, and other factors. Under long‐term operation conditions, the sediment stripped from the channel side wall is liable to silt along the process of water flow transportation in the channel, which seriously leads to elevation of the channel bottom, increase of channel width, and reduction of the horseway, which affect the normal water conveyance and operation safety of channels. In view of the collapse and instability of Zhetang diversion irrigation channel project in Xinjiang hydraulic project, through on‐site sampling and indoor rock mechanics test, the strength mechanical parameters of slope rock samples are obtained, and the indoor rheological test is carried out, and the triaxial rheological law is obtained. Under different levels of stress, the axial creep strain accounts for more than 50% of the total axial strain, indicating that the rheological effect of sample rock is obvious. Based on the strength parameters of rock samples, a numerical model is established. The stability of red‐bed soft rock channel bank slope is studied by using the strength reduction method of finite element method. The seepage field of channel slope under conventional working conditions is analyzed, and the slope stability under different operating conditions is compared and calculated. The results show that the slope stability safety factor of Zhetang diversion irrigation channel slope is 1.60 under conventional working conditions and 1.33 under check working conditions, which are greater than the recommended value in the specification.

Comparative assessment of the slope stability using different calculation methods

Comparison of the results of assessment of the of slope stability to determine the feasibility of construction of retaining structures is presented in this paper
 The construction of a grain terminal on a landslide slope in the Odessa region was selected as the object of researching. The building area belongs to the Black Sea basin region and is located on the southwestern slope of the Ukrainian Crystal Shield. The uneven stepped surface of the crystalline basement consists of blocks. Despite the significant irregularities of the crystalline basement, they are reflected in the relief through the sedimentary cover. To ensure of the slope stability, it is planned to install a cascade of retaining structures. There are pile retaining walls.
 The calculations are based on the analysis of the stress-strain state of the slope and anti-landslide structures using two fundamentally different methods. These methods of calculation using modern software:
 - analytical method for assessing the slope stability (limit equilibrium method);
 - assessment of the slope stability by the method of numerical modeling of the stress-strain state of the elements of the system "soil mass - anti-landslide structures".
 Calculations were made for two calculated cross-sections and for different stages of construction. There are stages native state, during construction and exploitation. 1st stage is assessment of the slope stability in its natural state, before building beginning. 2nd stage is assessment of the slope stability during the construction of the 1st retaining wall and excavations of the first level of the pit; stage 3 - assessment of slope stability after construction of anti-landslide structures and excavations of the pit. Stage 4 - assessment of the slope stability at the stage of grain terminal exploitation, it is meaning the construction of foundation structures.
 According to the results of calculations, the slope stability safety factors were determined, the analysis of SSS elements of the system "soil mass - landslide structures" was carried out and the reinforcement of retaining walls was selected.

ANALISIS STABILITAS LERENG MENGGUNAKAN APLIKASI PLAXIS 8.2 DENGAN PERKUATAN DINDING PENAHAN TANAH

The high embankment is one of the most common problems in toll road construction projects. Embankment aims to equalize the ground elevation. Higher the embankment, the greater the load will be received by the subgrade. So, it is necessary to analyze the stability of the embankment to determine condition of stability and some important safety factor (SF) values. Slope stability planning was carried out using reinforced retaining wall with a height of 9,5 m and a width of 5,7 m. Soil foundation type was cohesive soil (clay) and the embankment soil type used non-cohesive soil (sandy). Several SF values are obtained by using Plaxis 8.2, such as: the safety factor (SF) of slope stability without and with reinforcements are 1,23 and 1,59, respectively; SF of shear stability is 2,24; SF of overturning stability of 2,1; and SF of bearing capacity is 3,36.

Numerical Simulation Analysis of Slope Instability and Failure of Limestone Mine in Weibei

Weibei area is the largest limestone resource area in Shaanxi Province, which is an important boundary to distinguish the climate difference between the south and the north of China, and also a significant ecological safety protection barrier in the northwest of China. The complex geological environment and harsh environment make the mining area have serious geological disaster hidden danger. Based on the site engineering geological data of typical limestone quarry slope in Weibei, this paper constructs a three-dimensional geological model, uses FLAC3D software to simulate excavation, and analyzes the stress and strain law of the quarry slope. SlopeLE software was used to analyze the safety factor of slope stability and the potential slip surface before and after taking reinforcement measures. The results show the following: (1) Limestone is the main rock component of the mine, followed by mudstone. The joint and fissure are developed, the rock mass is broken, and the hidden danger of engineering geological disaster is high. (2) There is a sliding trend in both sides during excavation, and the maximum vertical displacement is 2.1 cm. (3) If the slope is reinforced according to the design scheme, the slope stability safety factor will be increased from 1.062 to 1.203 in a stable state, which greatly improves the stability of the slope and provides a guarantee for human and financial resources.

Stability Analysis of Rock Slope Based on Improved Principal Component Analysis Model: Taking Fuwushan Slope as an Example

Aiming at the problems of low accuracy, low efficiency, and many parameters required in the current calculation of rock slope stability, a prediction model of rock slope stability is proposed, which combines principal component analysis (PCA) and relevance vector machine (RVM). In this model, PCA is used to reduce the dimension of several influencing factors, and four independent principal component variables are selected. With the help of RVM mapping the nonlinear relationship between the safety factor of slope stability and the principal component variables, the prediction model of rock slope stability based on PCA-RVM is established. The results show that under the same sample, the maximum relative error of the PCA-RVM model is only 1.26%, the average relative error is 0.95%, and the mean square error is 0.011, which is far lower than that of the RVM model and the GEP model. By comparing the results of traditional calculation method and PCA-RVM model, it can be concluded that the PCA-RVM model has the characteristics of high prediction accuracy, small discreteness, and high reliability, which provides reference value for accurately predicting the stability of rock slope.

Do the standards need modifications? A proposal for geotechnical stability safety factor of breakwater

In different countries and continent, different standards are followed for geotechnical stability safety factors of breakwaters which are not exactly in the same line. Parties involved in breakwater design and construction projects might follow different procedures/standards (load cases to be analysed and the acceptable safety factor). It is a fact that a clear table that shows the acceptable safety factors for different load cases is not clearly presented in the standards. So the aim is to provide a proposal that covers all the standards. In this paper, four guidelines/standards of “Rock Manual”, “US Army Corps of Engineers”, “Eurocodes” and “ROM” are reviewed. Based on the mentioned standards and some considerations a table that shows the acceptable safety factors for different load cases is presented. Another concerns is that the actual more powerful and advanced calculation software allows to find the results with less uncertainty compared to the formerly applied methods. It means that lower safety factors in comparison to the old methods can be applied and accepted with the recent software. The aim of the paper is presenting a procedure for the slope stability safety factors in order to reduce the amount of discussions and disagreements that of course come from the interpretations of different standards. Furthermore, reduced slope stability safety factors for different load cases are proposed.

Early mitigation of landslide prone areas with remote sensing and analysis of slope stability in ampera, south jayapura district, papua province

Ampera, located in the eastern slope of Cycloop Mountains, Papua Province had a landslide disaster on March 17, 2019. Landslides in Ampera is caused by the steep slope. Landslides occur due to lack of early mitigation which results in material loss and death. Early mitigation was carried out by remote sensing aimed at mapping landslide-prone areas in Ampera. The determination of landslide-prone areas is based on several parameters and weighting of remote sensing. The parameters are based on the provisions made by the author with secondary data. Weighting is used based on the results AHP method. Parameters and weighting using rainfall (44%), slope gradient (31%), NDVI (15%), slope water density (7%), and road density (3%). This parameter is processed into raster data which is then combined with weighting. The results, Ampera has a moderate to high vulnerability for landslides. Three high vulnerability area was made a modeling incision to determine safety factor value for slope stability. Modeling was done using characteristics of Podzolic Soil type, obtained from the Soil Distribution Map of Papua Province. Based on the results of the modeling, the average value of the safety factor of slope stability in three areas with high vulnerability is 0.5 (unstable).