Changes In Factor Of Safety Research Articles

Establishment of Pile-soil Interaction Model and Optimization Analysis of Distance Diameter Ratio

Abstract The anti-skid pile is s an effective method for slope treatment. Analyzing its stress law and designing reasonable schemes are urgent problems that must be solved to guide slope prevention and control, and in this paper, combined with the original anti-skid pile reinforcement scheme, 5 pile-soil interaction models with different distance diameter ratios D/d are established. The anti-skid pile and slope are discretized, and the slope displacement and safety factor, pile stress and deformation, and soil arching effect between piles are numerically analyzed so as to optimize the design parameters of spacing diameter ratio of anti-skid piles. The results show that (1) the distance diameter ratio of anti-skid piles negatively correlates with the safety factor. When D/d>2.8, the slope safety factor is 2.011>2.0. (2) The peak shear force and soil arching effect of anti-skid piles are positively and negatively correlated with the distance diameter ratio, respectively. The reaction force of the anti-skid pile suddenly changes at the soil-rock interface about 10 m away from the pile top, and local reinforcement should be carried out when the anti-skid pile is designed and optimized. (3) Based on the analog data of displacement and safety factor changes, pile body stress, and soil arch stress between piles, and considering economic factors, the optimal distance diameter ratio D/d is determined to be 2.8-3.0. Compared with other methods, the optimization method proposed in this paper has reasonable theory and sufficient data. The research results will provide theoretical reference and engineering technical guidance for similar slope reinforcement with anti-skid piles, and have specific application and promotion value.

Retraction Note to: Controlling the Diffusion of Runaway Electrons by Safety Factor Changes in IR-T1 Tokamak

Retraction Note to: Controlling the Diffusion of Runaway Electrons by Safety Factor Changes in IR-T1 Tokamak

Analisis Stabilitas Tempat Pembuangan Akhir (TPA) Sampah Akibat Pengaruh Perubahan Sifat Mekanis Material Sampah

The stability of landfill is a crucial aspect of waste management. Numerous factors influence the stability of landfill, one of which is the alteration of the mechanical properties of the waste material. This research aims to analyze landfill stability by considering the effects of changes in the mechanical properties of waste material. A construction stage analysis was conducted to model the process of altering the mechanical properties of waste material. The analysis was divided into 13 stages corresponding to the number of landfill steps. The initial five stages were modeled as waste with an age of < 5 years, stages 6-10 were modeled as waste with an age of 5-10 years, and the last three stages were modeled as waste with an age of > 10 years. Stability analysis using the finite element method was conducted using the concept of shear strength reduction. The analysis results indicated changes in the landfill's safety factor throughout its operational period. Stages 1-5 experienced changes in the safety factor, although these changes were not significant. Stages 6-10 witnessed a considerable decrease in the safety factor before experiencing an increase in stage 11, followed by a continuous decline until the end of stage 13. Despite changes in the safety factor during the operational process, the overall safety factor values obtained still met the minimum safety factor criteria required.

Temperature and shear-rate effects in two pure clays: Possible implications for clay landslides

Temperature fluctuations in landslide shear zones can originate from heat exchanges with deeper layers as well as with the atmosphere through the landslide body. Shallow landslides (depth <10 m) are especially subject to seasonal temperature oscillations and rapid climatic changes. Various hydro-mechanical properties of clayey soils are sensitive to changes in temperature. Few studies suggested that the residual shear strength may vary significantly even in temperature ranges typical of shallow layers in temperate and warm regions. Here, we verified the response of two pure clays (Ca-bentonite, kaolin) to shearing at temperatures up to ∼55 °C under various normal stresses (50–150 kPa) and shear rates (0.018–44.5 mm/min) by equipping a ring-shear device with a temperature-control system. Then, we performed experiments on an ideal slope to quantify the extent to which ground temperature can condition the stability of clay slopes, across the seasons and under prolonged warming. Considering the largest effects evaluated experimentally (change in residual shear strength by ±1.5 %/°C), we determined changes in global factor of safety by ∼20 % for rotational slides ∼6 m deep, solely attributable to seasonal heating-cooling. Warming of 5 °C over decades would change the stability condition by an additional ±7 %. Although these results were obtained under simplified geometry and boundary conditions, without considering changes in triggers, preconditions, and effects of other thermo-hydro-mechanical couplings, they provide an upper bound to the role of the temperature-dependence of the residual shear strength on the factor of safety. We argue that this role should not be neglected in slope stability and landslide hazard assessments in clay-rich soils, thus warranting in-depth experimental analyses and advanced modelling.

A Numerical Study on The Change in Safety Factor (FOS) According to Slope Angle Change for The Establishment of Photovoltaic Facilities Using SRM (Strength Reduction Method)

A Numerical Study on The Change in Safety Factor (FOS) According to Slope Angle Change for The Establishment of Photovoltaic Facilities Using SRM (Strength Reduction Method)

Evaluasi Stabilitas Lereng Pada Struktur Bangunan Penahan Lokasi Gedung C Fakultas Ekonomi Universitas Cenderawasih

Thus, the slope at Building C of the Faculty of Economics of Cenderawasih University needs to be handled in the form of evaluation or review of the plaster structure (talud), by improving the dimensions, and the slope is analyzed by drained conditions, the slope becomes stable as the slope safety factor changes to 1.557. which according to the safety factor (SF) slope is more than 1.5, and the calculation of Stabilita against shear of slope safety factor is 1,678, which according to safety factor more 1.5. Means that the wall is able to withstand the moment of land that works

Analisa Penyebab Penurunan Badan Jalan Di Ruas Jalan Baru Furia Kotaraja STA (0+000 – 0+520)

Topography in Papua is generally an area consisting of mountains and valleys that have various slopes. Means of transportation was planned in such a way that it had to go through the slope. One of them is on the New Furia Kotaraja road section. On this road section, the slope is cut so that the road is made safe and comfortable for motorists to pass. However, at several points there was damage to the road body which was identified as a landslide, namely the formation of an avalanche crown on the surface of the road body. Therefore it is necessary to analyze the stability of the slopes in order to obtain ways to overcome them. Analysis of slope stability on the New Furia Kotaraja road section used the GeoStudio 2007 Slope/W assist program and manually used the Fellenius method. From the analysis that has been carried out, given the condition of the road load and pore water pressure, it can be concluded that the slopes on the New Furia Kotaraja road section Km 0+000 – 0+520 are unstable slopes because according to the results of the calculation of the slope safety factor based on the Fellenius formula, namely 0.589, according to Bowles, the slope is unstable if the factor of safety is less than 1.07. Thus, the slopes on the Baru Furia Kotaraja Km 0+520 road section need to be treated in the form of a box cover / culvert, with a surface depth of 280 cm box coler because at that depth it has a rather dense soil type, silty sand, and a channel is also planned. square type drainage with dimensions (b = 2.00 ; h = 1.70 m ) to drain water discharge (Q = 0.68 m3/s), the slope becomes stable because the slope safety factor changes to 1.259 which according to Bowles's opinion the slope is included stable when the factor of safety is above 1.25.

Evaluation of the Influence of In Situ Stress on the Stability of Mine Pit Walls: A Case Study of Songwe Mine

The investigation of the influence of in situ stress in Open Pit Mine (OPM) projects has not been accorded a deserved attention despite being a fundamental concern in the design of underground excavations. Hence, its long-term potential adverse impacts on pit slope performance are overly undermined. Nevertheless, in mines located in tectonically active settings with a potential high horizontal stress regime like the Songwe mine, the impact could be considerable. Thus, Using FLAC3D 5.0 software, based on Finite Difference Method (FDM) code, we assessed the role of stress regimes as a potential triggering factor for slope instability in Songwe mine. The results of the evaluated shearing contours and quantified strain rate and displacement values reveal that high horizontal stress can reduce the stability performance of the pit-wall in spite of the minimal change in Factor of Safety (FoS). Since mining projects have a long life span, it would be recommendable to consider “in situ stress-stability analyses” for OPM operations that would be planned to extend to greater depths and those located in tectonically active regions.

Safety Factor of Unsaturated Soil Slopes considering the Intermediate Principal Stress Effect and Different Profiles of Matric Suction

Profiles of matric suction are critical for assessing the stability of unsaturated soil slopes, and the strength of unsaturated soils is affected by the intermediate principal stress. This study presents a theoretical formulation of safety factor for infinite unsaturated soil slopes under four different profiles of matric suction using the limit equilibrium method. The unified shear strength equation under plane strain conditions is adopted to capture the effect of intermediate principal stress on the strength of unsaturated soils. The proposed formulation of safety factor is found to have good comparability and broad applicability. The validity of the proposed formulation is demonstrated by comparing its predictions with the results of the extended shear strength method and the finite element method available in the literature. Parametric studies show that the effect of intermediate principal stress on the stability of unsaturated soil slopes is significant; the difference of safety factor among four suction profiles is pronounced, and the safety factor is highest for a linear suction profile. In addition, the safety factor changes with the infiltration depth in two stages, decreases with the slope angle, and increases with effective strength parameters. The results of this study are capable of providing beneficial guidance for optimization designs and disaster preventions of unsaturated soil slopes.

Slope stability analysis in various Terraces model (case study: Sendangmulyo, Tirtomulyo District, Wonogiri Regency)

Wonogiri has various contours. Steep slopes dominate some areas. Hence it has a high possibility to occur landslides. There are still a lot of people living under the slopes. Therefore, this research is essential for disaster mitigation purposes. The study aims to know how the value of the slope safety factor changes with construction terraces design. The research was conducted by collecting secondary data and improving the Terraces construction carried out. The data was analyzed in the limit equilibrium method to provide conditions before and after the rain. The models were tried with several Terraces variations on the slope to obtain the most optimal design. The results used a simplified Bishop method. The design of terraces on the slopes of Sendangmulyo Wonogiri Village shows that the SF value increase is only for the conditions before a rain. In contrast, the states after the rain do not yield a safety condition. The SF value increases if the number of steps increases, whereas the more step height increases, the less the SF value will be.

Forecasting the long-term deterioration of a cut slope in high-plasticity clay using a numerical model

This paper details development of a numerical modelling approach that has been employed to forecast the long-term performance of a cut slope formed in high plasticity clay. It links hydrological and mechanical behaviour in a coupled saturated and unsaturated model. This is used to investigate the influence of combined dissipation of excavation-generated excess pore water pressures and seasonal weather-driven near-surface cyclic pore water pressures. Deterioration of slope performance is defined in terms of both slope deformations (i.e. service) and factor of safety against shear failure (i.e. safety). Uniquely, the modelling approach has been validated using 16 years of measured pore water pressure data from multiple locations in a London Clay cut slope. Slope deterioration was shown to be a function of both construction-induced pore water pressure dissipation and seasonal weather-driven pore water pressure cycles. These lead to both transient and permanent changes in factor of safety due to effective stress variation and mobilisation of post-peak strength reduction over time, respectively, ultimately causing shallow first-time progressive failure. It is demonstrated that this long-term (90 year) deterioration in slope performance is governed by the hydrological processes in the weathered near surface soil zone that forms following slope excavation.

Effect of changing groundwater level on shallow landslide at the basin scale: A case study in the Odo basin of south eastern Nigeria

This study investigated the effect of changing groundwater level on the propagation and continued expansion of gully erosion and landslide in the Odo River sub basin (a major section of the Agulu-Nanka gully erosion and landslide complex located in south eastern Nigeria). A novel modified deterministic approach, loosely coupled stability (LOCOUPSTAB) framework which involves the development and linkage of groundwater recharge model, groundwater model (MODFLOW) and slope stability model (using Oasys slope, a program for stability analysis by limiting equilibrium) was used to determine the possibility of improving the stability of the study area. For the modelled scenario, reducing groundwater level through pumping from three boreholes at 300m3/day over one year, resulted in an increase in proportional change in factor of safety by an average 0.56 over the Odo river sub-basin. A stability risk map was also developed for the sub-basin. Useful information can be obtained even based on imperfect data availability, but model output should be interpreted carefully in the light of parameter uncertainty.

Analisis Perubahan Faktor Keamanan Lereng Akibat Hujan

Infiltration causes a decrease in soil shear strength parameters. Decrease in soil shear strength parameters can cause landslides. Landslides often occur in Bogor Regency, one of the landslide locations is Puncak, Bogor. Landslides in Puncak, Bogor on 05 February 2018 at 09.20 WIB must have a safety factor 1.07. Changes in safety factors due to rainfall are observed from 03 February 2018 at 05.00 WIB until 05 February 2018 at 09.20 WIB. This research includes testing soil samples, pore water pressure analysis and slope stability analysis. The software used for this analysis is GeoStudio. The analysis results are the changes in safety factor due to rainfall. The safety factor on 03 February 2018 at 05.00 WIB is 1.602. Safety factor until 05 February 2018 at 03.40 WIB are still above 1.25. So, the slopes are still safe. The decline in safety factor continued until 1.070 due to a decrease in cohesion on 05 February 2018 at 09.20 WIB with cohesion on SW-SM soil and SM soil at 4.01 kPa and 9.18 kPa. So, the duration needed to change a safe slope to landslide is only 5 hours 40 minutes. This can occur because of the intensity of the rain on 05 February 2018 at 07.00 WIB and 08.00 WIB are 34.1 mm/hour and 34.9 mm/hour. &nbsp; Key words: cohesion, landslides, rainfall, safety factor

Assessment of Infrastructures Assets Induced by Water Level Fluctuation along the Bengawan Solo River

The stability of infrastructure along river channel, such as bridges and embankments, is paramount to continuing service and public safety, and therefore, is essential consideration in the design, construction and maintenance. During the design process, infrastructure stability is often assumed to be static, and considered by implementing a safety factor which is produced by an analysis of extreme condition. However, this has failed to consider the variability of natural factors and importantly, the escalating threat of extreme environmental condition, induced by global climate change. This assumption should, therefore, be revisited for developing a more resilient design and maintenance regime. To demonstrate the changing infrastructure stability, an assessment of safety factor of river embankment and bridge foundation as nearby infrastructures along Bengawan Solo River’s channel and estuary is presented. This was undertaken to determine the impact of water level fluctuation during two extreme conditions during dry and rainy seasons in several critical locations. The river characteristics (i.e. morphology, water fluctuations, velocity, and sub-soil characteristics), embankment conditions and bridge pile foundation were investigated in-situ to assess the change of safety factor. The laboratory investigation focused on river and embankment characteristics including the analysis of the drying-wetting conditions. In-situ and laboratory investigations found an extreme condition which the infrastructures are subjected into, where the water level and flow velocity were 3 m and 0.04 - 0.27 m/s during dry season; and 10 m and 0.46 - 0.84 m/s during rainy season. Furthermore, from the analysis, it can be concluded that certain areas in the river do not meet the minimum requirements for bridge foundation and embankment stability.

Influence of Water Level Rise on the Bank of Reservoir on Slope Stability: A Case Study of Dagangshan Hydropower Project

This paper considers stability of slope under varying water level for the right bank of reservoir of Dagangshan hydropower project. SEEP/W and SLOPE/W are used for numerical analysis. Morgenstern-Price method is used for stability analysis. Change in Factor of Safety with the rise in water level is obtained. Three cases of water level rise are studied as fast, medium and slow. It is found out that, when water level rises, the water table also rises correspondingly hence changing the properties of the rock mass in slope and its behavior to different situations and stresses. With the change in the water table line, the property like permeability changes, which is a significant property for slope stability and affects directly the strength of rock mass. Also due to change in water table within the slope, the situation of saturated and unsaturated portions in the slope also changes which is a complex phenomenon to deal with. So it has to be considered as an important factor. The changing pattern of the factor of safety with the elevation is similar for the cases of slow and medium but it is different for fast case. There is difference in factor of safety for the same elevation for different cases so the speed of the rise in water level also influences the impact on the stability. The comparison of fast and medium cases show that the difference in factor of safety is low but while comparing the cases- slow and fast the difference is high.

Effect of Seepage Force on Stability of High Embankment with Coarse-Grained Soil during Rainfall

A new numerical calculation method for slope stability is proposed to analyze the effect of the seepage force of a coarse-grained soil embankment slope on the distribution of the plastic zone and the change in safety factor under rainfall condition. The framework of coarse-grained soil was analyzed, and the SEEP/W module of software Geo-studio was used to calculate the change in matrix suction, underground water table line, and seepage gradient. Then, the calculation result for seepage was imported into FLAC3D using FISH language, considering the change in underground water table line, matrix suction, and seepage force. The influence of seepage force on the stability of the slope was also analyzed. Results showed that rainfall affected the spatial distribution of the underground water table line, matrix suction, and seepage gradient. The underground water table line lifted gradually from the foot of the embankment slope and developed into a deep slope. After a rainfall, the underground water table line decreased rapidly and the height of the final line near the embankment center was higher than the initial state. The matrix suction dissipated gradually because of the change in the underground water table line but recovered slowly when the rainfall stopped. At the beginning of a rainfall, the positive values of X-direction seepage gradients turned to negative and the negative areas expanded gradually. The plastic zone of the slope extended gradually from the foot to the inside of the slope as the rainfall continued. After the rainfall, the plastic zone mainly occurred at the foot of the slope. The slope safety factor increased gradually at the beginning of the 24 h period. The safety factor decreased rapidly and reached the minimum after 72 h. Then, the rainfall safety factor was gradually restored, but the recovery of the safety factor was delayed and smaller than during the initial state.

Time-frequency analysis of instantaneous seismic safety of bedding rock slopes

An earthquake wave has many non-linear and non-stationary components. In current methods for seismic slope stability analysis, the time-frequency-amplitude characteristics of the earthquake waves, which can significantly affect the computation results, are not taken into account. In this paper, formulas for computing the seismic safety factor of bedding rock slopes are derived based on the elastic wave mechanics. The Hilbert-Huang transform (HHT) signal processing technique is employed to identify the time-frequency-amplitude characteristics of the earthquake waves in the time-frequency domain. Then a time-frequency method for computing the instantaneous seismic safety factor of bedding rock slopes, which considers the time-frequency-amplitude characteristics of the earthquake waves simultaneously, is proposed. A shaking table test example is worked out to illustrate the application of the proposed time-frequency analysis method to a bedding rock slope. The instantaneous seismic safety factors of all bedding planes are calculated based on the time-frequency analysis method proposed in this research. The seismic safety factor changes significantly over time, and the seismic safety factor of the upper part of the bedding rock slope is smaller than that of the lower part of the bedding rock slope. Hence the upper part of the bedding rock slope is more vulnerable to seismic damage.

Effect of pile driving adjacent to soil slopes on safety factor of specific sliding surface

The effect of pile driving force, plastic zone around the pile tip and anti-sliding action of the pile body on safety factor of sliding surface is investigated by using the stability calculation methods for slopes based on the cavity expansion theory with the consideration of elasto-plasticity of soil. Through a numerical case, change of safety factor in the whole process of the pile driving is analyzed. And the effect of pile diameter, slope angle and distance between pile and slope top on the change of safety factor of slope is discussed. The results show that the pile driving force and the plastic zone at pile top have an adverse effect on slope stability, which leads to a decrease in the safety factor, while the anti-sliding effect of the pile has a positive contribution to the slope stability, especially when the end of pile is below the sliding surface. The safety factor decreases significantly with the increase of the pile diameter, and it significantly increases after the pile end penetrates through the sliding surface. The greater the slope angle, the smaller the safety factor after pile driving. The safety factor drops more slowly with the increase of the distance of the pile away from the slope top, and the effect of the plastic zone on the safety factor also gradually decreases. The pile driving will not affect the stability of the sliding surface when the pile is far from the top of the slope. The results may provide some guiding significance and reference value for the design and construction of static pile driving adjacent to slopes.

Slope Sensitivity Analysis Using Spencer's Method in Comparison with General Limit Equilibrium Method

This paper analyses the sensitivity analysis of a natural-unreinforced slope in Kepong, Kuala Lumpur. In order to conduct a sensitivity analysis, several ranges of data, based on borehole information and figures and also typical range of earth materials geotechnical values are used to set the minimum and maximum value of parameters in Slide 6.0 software. Under Mohr-Coulomb failure criterion, Spencer's and General Limit Equilibrium methods of slices were used in the analysis to determine the influence of varying parameters values towards the change in safety factor. In addition, the percentage differences in safety factors obtained by both methods based on General Limit Equilibrium method are also determined in the analysis. In the analysis, water table location has the highest influence to the change in safety factors of the slope. Besides, the percentage differences in safety factors obtained by both methods are very nominal and showed a good agreement to each other.

RETRACTED ARTICLE: Controlling the Diffusion of Runaway Electrons by Safety Factor Changes in IR-T1 Tokamak

The high-energy current of runaway electrons during a major disruption in tokamak reactors can cause serious damage to the first wall of the reactor and reduce its lifetime. Therefore, it is important to find methods for decreasing the generation of runaway electrons and their energy. The safety factor plays an important role in determining the stability criteria for a wide range of MHD modes. Since runaway electrons suffer only rarely from collisions and are hardly sensitive to electrostatic turbulence, their transport is governed by the magnetic lines structure. On the other hand, since the safety factor is related to the magnetic lines structure, changes in safety factor may have important effects on the diffusion of runaway electrons. In this paper, the generation of runaway electrons and their transport is investigated theoretically. Moreover, by changing the discharge voltage of ohmic and toroidal capacitors, different values of the edge safety factor is generated. In fact, in this experiment, the researchers try to increase the diffusion of runaway electrons by using safety factor changes in the IR-T1 tokamak.