Safety Factor Research Articles

Stability Study and Strengthening Strategy of Spiral Case-Encased Concrete Structure of Pumped Storage Power Station

With the development of global hydropower, the scale of hydropower stations is increasing, and the operating conditions are becoming more complex, so the stable operation of hydropower stations is very important. The vibration of the turbine unit will cause resonance in the powerhouse, and the structural stability of the powerhouse will be affected. Many scholars pay attention to the stability of the turbine unit operation, and there are few studies on the powerhouse of the hydropower station. Therefore, this paper relies on the Weifang Hydropower Station project to study key issues such as the tensile strength of concrete and how to arrange steel bars to increase the structural stability by changing the material properties through FEA. Three schemes are designed to evaluate the safety of the powerhouse structure when the turbine unit is running through the safety factor. Our findings indicate that the stress variation patterns observed on the inner surface of the powerhouse remain consistent across different operating scenarios. Notably, along the spiral line of the worm section, we observed that the stress levels on the vertical loop line decrease gradually with increasing distance from the inlet. Conversely, stress concentrations arise near the inlet and the tongue. Additionally, it has been noted that the likelihood of concrete cracking increases significantly at the tongue region.

Computational modeling of three-dimensional slope reinforcement by anchor cable micropile group considering coordinated deformation

The application of anchor cable micropile group (ACMPG) in small and medium-sized slope support is gradually widespread. However, the coordination deformation of the structure and the resistance of the soil in front of the piles are less considered in the existing calculation models. Therefore, based on the load transfer approach and according to the structural characteristics of the ACMPG, the calculation method was provided for the resistance of the soil in front of the pile and the tension of the anchor after deformation. And the equations for calculating the resistance of the ACMPG were established. Based on the method of upper bound limit analysis, the display equation had been established for the safety factor of reinforcing the 3D slope of the structure. And finite element models were developed to validate the theoretical model. Finally, a parametric study was conducted to investigate the influence of slope angle, soil friction angles, location, 3D effects, on the slope safety factor and the support effect of piles and anchor cables supporting the structure. The results showed that the theory proposed in this paper can accurately calculate the safety factor of slopes, which is helpful for the design and construction of slope reinforcement.

Efficient optimization-based method for simultaneous calibration of load and resistance factors considering multiple target reliability indices

This study introduces an innovative optimization process for calibrating probabilistic load and resistance factors (LRFs) in limit state designs, effectively accommodating multiple target reliability indices. Given the impracticality of direct Monte Carlo simulations (MCS) for this task, a response surface method (RSM) is proposed to approximate load and resistance components separately rather than fitting conventional safety factors. This approach eliminates the need for additional implicit evaluations, thereby improving the efficiency of LRF calibration across multiple targets. The process is further enhanced by an adaptive boundary algorithm that updates search domains in real-time, streamlining the optimization. Validation through three examples—including one explicit and two implicit performance functions (a structural and a geotechnical example)—demonstrates that the method achieves accurate results with fewer iterations by dynamically narrowing search domains. Specifically, the accuracy of the proposed method is confirmed by comparing results with those from the literature for the explicit example and with basic MCS results applied to the initial implicit problems. Performance on the illustrative examples shows that the structural example achieves calibration for three targets within ten iterations. Additionally, this method eliminates the need for approximately ten thousand implicit evaluations when calculating limit state points for the geotechnical example.

Accuracy of kinetic equilibrium reconstruction of NSTX and NSTX-U plasmas and its impact on the transport and stability analysis

Abstract An accurate magnetohydrodynamic (MHD) equilibrium reconstruction is an essential starting point for stability and transport plasma analysis. This work describes an approach for obtaining kinetic equilibrium reconstructions using the OMFIT framework, which has been applied for the first time to spherical tokamak data from NSTX and NSTX-U. The EFIT equilibrium solver is integrated with experimental data analysis procedures and subsequent TRANSP transport simulations to enhance the accuracy of the reconstruction, in particular at the edge region, by adding constraints on the total pressure and current density profiles, based on the transport code solution. The accuracy of the equilibrium depends on the uncertainty and number of constraints, as well as the choice of basis functions to represent the pressure and current density profiles. An improved fidelity of the equilibrium reconstruction is demonstrated by reducing the variability of the magnetic axis and boundary locations from several centimeters for reconstructions based on magnetic and experimental pressure constraints to only several millimeters for kinetic reconstructions based on transport code constraints, when different representations for basis functions were tested. Variability of the safety factor on-axis was reduced ten times in the same sensitivity study. The accuracy of the equilibrium reconstruction and subsequent mapping of experimental kinetic profile data have a significant impact on TGLF and linear CGYRO turbulence simulations, which predict different spectra of unstable modes and turbulent fluxes for cases with different numbers of constraints in the equilibrium reconstruction. Conversely, the stability analysis performed with the GATO code shows plasmas stable to n = 1 MHD modes in both equilibria using magnetic and experimental pressure constraints as well as the transport code constrained equilibrium. However, a scan of parameters away from these conditions shows considerable deviation in the threshold of unstable modes between these reconstructions. Therefore, for reliable plasma analysis and use in turbulence and stability calculations, a high fidelity equilibrium reconstruction with accurate kinetic constraints based on transport code solutions is necessary.

Helical resonant magnetic perturbation coils for controlling edge localized modes: a robustness study

Abstract Plasma response to helical resonant magnetic perturbation (RMP) coil current is numerically computed for tokamak plasmas, with optimization results compared with that for conventional window-frame coils. The key aspect of study is the robustness of the proposed new concept against variation of plasma equilibrium parameters including (i) the plasma resistivity, (ii) the toroidal rotation and (iii) the plasma shaping (both elongation and triangularity). Toroidal modeling results yield several important conclusions. First, assuming the same coil current, the optimal helical coils robustly outperform the optimal window-frame coils against variation of the aforementioned plasma equilibrium parameters. Secondly, for a chosen toroidal spectrum, the optimal helical coil geometry including the poloidal location, poloidal coverage and the overall shape, is robust against variation of plasma parameters except the safety factor. Finally, in all cases, optimization based on the plasma response naturally yields a single row of helical coils located near the outboard mid-plane of the torus, ensuring a relatively simple design of the coil geometry.

Analysis of cement-stabilized soil on road embankment employing finite element analysis - a case study

Abstract The application of stabilized soil is fast expanding around the world, and it is delivering improvements to the construction industry. Stabilized soil is a popular choice for reinforcing road embankments around the world. A layer of cement-stabilized soil can reduce the settlement of the soil layer below the embankments. This study compares the long-term settlement of road embankments with and without cement-stabilized soil layers of the Chittagong Port Access Road located at Teknaf Bangladesh. The settlement analysis of the road embankment was performed using the Finite Element Analysis with Plaxis2D. In this study, two forms of sequence modeling were used. First, the settlement of a road embankment without reinforcement was examined. The second modeling step was to determine the settlement of an embankment reinforced with a cement-stabilized soil layer. Following the simulation, a comparison was performed. Additionally, the effect of cement content (4%, 8%, and 12%), compaction energy, and single, double, and triple layers of CSS on long-term settlement along with the factor of safety of the embankment have been addressed. The results demonstrated that using this specific cement-stabilized soil below the road embankment has decreased the long-term settlement of the soil while increasing the safety of the embankment compared to that without the cement-stabilized soil reinforcement.

Some Observations on the Strength of Viking Ship Rudders

Technical papers which attempt to analyse historic and ancient ship structures using modern techniques appear only spasmodically in today’s learned engineering journals. There could be many good reasons for this; the lack of commercial incentives, the paucity of accurate engineering data and perhaps a certain reluctance to cross into an area which is rightly the province of the nautical archaeologist. This, in the author’s view is a pity since simplified analytical techniques of the type routinely used in design offices can offer useful cost-effective insights into the physical behaviour of historic ships and craft, without endangering the physical reconstruction or its crew. In addition as the input data are often only loosely defined, less sophisticated methods are ideal for conducting “data-sensitivity” investigations. One such paper (Loscombe, 2022) described efforts to apply modern local and global structural design methods to Viking-age ships with a view to establishing plausible operational factors of safety for comparison with modern requirements. This follow-up contribution continues with the theme by focusing on the rudder. Rudder failure can endanger any ship, ancient, medieval or modern but the Viking ship rudder has a number of structural features not found on modern vessels which invite retrospective stress analyses. One component in particular, the lower bearing in modern terminology, appears to have a very short operational life, measured in days rather than years as is the expectation for today’s marine vehicles and hence the Viking ship rudder is a good candidate for such simplified numerical analyses.

A scientometrics review of conventional and soft computing methods in the slope stability analysis

Predicting slope stability is important for preventing and mitigating landslide disasters. This paper examines the existing approaches for analyzing slope stability. There are several established conventional approaches for slope stability analysis that can be applied in this context. However, in recent decades, soft computing methods has been extensively developed and employed in stochastic slope stability analysis, notably as surrogate models to improve computing efficiency in contrast to traditional approaches. Soft computing methods can deal with uncertainty and imprecision, which may be quantified using performance indices like coefficient of determination, in regression and accuracy in classification. This review study focuses on conventional methods such as the Bishop’s method and Janbu’s method, as well as soft computing models such as support vector machine, artificial neural network, Gaussian process regression, decision tree, etc. The advantages and limitations of soft computing techniques in relation to conventional methods have also been thoroughly covered in this paper. The achievements of soft computing methods are summarized from two aspects—predicting factor of safety and classification of slope stability. Key potential research challenges and future prospects are also given.

Multiscale Analysis of Pedestrian Crossing Distance

Problem, research strategy, and findings Crossing distance is considered a factor in both pedestrian safety and behavior. However, it has seldom been quantified within or across entire cities or related to walking outcomes. Combining data encoded in OpenStreetMap and drawn from high-resolution satellite imagery, we measured formal pedestrian crossings throughout a dense European city (Paris [France]), a dense American city (San Francisco [CA]), and a less-dense, more car-centric American city (Irvine [CA]). This granular approach—covering roughly 49,000 total crossings—identified inter- and intraurban spatial patterns in the distribution of pedestrian crossing distance, including clusters of long crossings that likely deter walking and increase its risk. By overlaying recent pedestrian–vehicle collisions on these novel data sets we found that longer crossing distance correlated with increased likelihood of collisions, raising the salience of traffic-calming interventions. Takeaway for practice Quantifying pedestrian crossing distance at the scale of entire municipalities empowers transportation planners to identify pedestrian-hostile crossings (individuals and clusters), add context to collision trends, and geographically target locations for traffic calming. These cases collectively demonstrate how the increasing prioritization of the automobile in city planning quantitatively changes (and degrades) the pedestrian environment, as well as how low-tech investments, such as sidewalk extensions and refuge islands, can mitigate these trends.

A meshless model for three-dimensional direct numerical simulation of local scour around cylinder bridge foundation

A meshless local scour model for cylinder bridge foundation based on the smoothed particle hydrodynamics (SPH) method is proposed in this paper. Differing from the traditional Eulerian mesh model used for monopile local scour, it overcomes the high requirements of mesh quality and density for capturing large deformations at the fluid interface. Unlike the transient sediment erosion SPH model used for dam-break, sediment flushing, and water jet, the meshless approach is innovatively applied to the continuous simulation of bridge local scour under steady flow conditions. The present SPH model is established based on the SPH multi-phase fluid model, integrating a classical fluid model combined with numerical stabilization algorithms to govern water particle motion and a sediment model from Zhang et al. (2024) to govern sediment evolution, and tests a new scheme for boundary treatment in the model based on DualSPHysics. Furthermore, a novel scour visualization method that aims at extracting both visible and actual bed surfaces from discrete particles is proposed. The model is validated through comparison with rigid bed and live bed experiments, demonstrating favorable agreement in terms of flow and scour simulation. Importantly, the model results reveal a discrepancy between the elevation of the post-scour visible bed surface derived from the conventional Eulerian mesh model and experimental data, compared to the actual bed surface unaffected by water flow erosion. This indicates the necessity for incorporating a safety margin in foundation design when utilizing experimental results to determine the maximum scour depth.

Evaluation of a novel central venous access port for direct catheter insertion without a peel-away sheath.

This study retrospectively evaluated the feasibility and safety of implanting a newly developed central venous access port (CV-port) that allows catheter insertion into a vein without the use of a peel-away sheath, with a focus on its potential to minimize risks associated with conventional implantation methods. All procedures were performed using a new device (P-U CelSite Port™ MS; Toray Medical, Tokyo, Japan) under ultrasound guidance. The primary endpoint was the implantation success rate. The secondary endpoints were the safety and risk factors for infection in the early postprocedural period (< 30days). We assessed 523 CV-port implantations performed in a cumulative total of 523 patients (240 men and 283 women; mean age, 61.6 ± 13.1years; range, 18-85years). All implantations were successfully performed using an inner guide tube and over-the-wire technique through 522 internal jugular veins and one subclavian vein. The mean procedural time was 33.2 ± 10.9min (range 15-112min). Air embolism, rupture/perforation of the superior vena cava, or hemothorax did not occur during catheter insertion. Eleven (2.1%) intraprocedural complications occurred, including Grade I arrhythmia (n = 8) and subcutaneous bleeding (n = 1), Grade II arrhythmia (n = 1), and Grade IIIa pneumothorax (n = 1). Furthermore, 496 patients were followed up for ≥ 30days. Six early postprocedural complications were encountered (1.1%), including Grade IIIa infection (n = 4), catheter occlusion (n = 1), and skin necrosis due to subcutaneous leakage of trabectedin (n = 1). These six CV-ports were withdrawn, and no significant risk factors for infection in the early postprocedural period were identified. The implantation of this CV-port device demonstrated comparable success and complication rates to conventional devices, with the added potential benefit of eliminating complications associated with the use of a peel-away sheath.

Efficacy, safety, and optimal intervention of belimumab for proliferative lupus nephritis patients in real-world settings: LOOPS registry.

This study investigated the efficacy, safety, and predictive factors of belimumab (BEL) in induction therapy for patients with proliferative lupus nephritis (LN) in real-world settings. Patients with biopsy-proven ISN/RPS class III or IV LN, with or without coexisting class V LN, who underwent standard of care (SoC), glucocorticoid (GC), and either mycophenolate mofetil or cyclophosphamide treatments were included. Participants were treated with SoC (SoC group, n = 32) or BEL and SoC (BEL+SoC group, n = 30). The primary end point was complete renal response (CRR) at 52 weeks. Baseline patient characteristics were not significantly different between the two groups. The 52-week retention rate of BEL was 90.0%. The BEL+SoC group showed significantly higher CRR and primary efficacy renal response achievement at 52 weeks and significantly lower GC dosage, adverse events, and Systemic Lupus International Collaborating Clinics damage index scores. Multivariate analysis of CRR achievement at 52 weeks revealed that the lack of estimated glomerular filtration rate (eGFR) improvement at 4 weeks was associated with CRR failure in the SoC group. A shorter duration (cut-off of 42 days) between the start of induction therapy and addition of BEL was also related to the CRR in the BEL+SoC group. BEL, in addition to SoC, controls disease activity, reduces GC use, and suppresses organ damage in case of proliferative LN. Earlier BEL induction within 6 weeks may help achieve CRR in treatment-resistant cases without eGFR improvement at 4 weeks after induction therapy.

Characteristics of disruptions observed in the initial operation phase of JT-60SA

Abstract Disruption database in the JT-60SA first plasma operation period has been constructed. The disruptions have been divided into three categories based on their characteristics, and the characteristics of each category have been discussed. The most commonly observed disruptions were vertical displacement events (VDEs). As expected by simulations using the MHD equilibrium control simulator (MECS), a highly elongated plasma was likely to disrupt by VDE when the gap between the plasma surface and the wall is large. Despite the quite high edge safety factor q95 of above 10 in the initial operation, some discharge disrupted because of control failure caused by the n=1 tearing mode. One possible cause of the n=1 tearing mode is the edge cooling in high density. The last category is the radiative disruptions, which is characterized by slow current decay with multiple spikes in soft X-ray signals. These spikes are thought to be related to the MHD activity that occurred when the cooling front crossed the rational surface. The radiative disruptions are attributed to a sudden change in edge power balance.

An Analytical Insight Into Stability Analysis of Unsaturated Multi‐Layered Slopes Subjected to Rainfall Infiltration

ABSTRACTSlopes in nature usually present layered characteristics, and its stability is susceptible to rainfall events. Considering that current analytical solutions are only suited to simulate the rainfall infiltration of double‐layered infinite unsaturated slopes, an analytical procedure is hence proposed in this study to tackle the consideration of multiple layers. The variable separation method and transfer matrix method are combined to derive the analytical solution of pore water pressure (PWP) for simulating rainfall infiltration in layered infinite unsaturated slopes. After having validated the proposed model and analytical solutions by comparing with existing literature and numerical simulation, the closed‐form solution of PWP is incorporated into the limit equilibrium for assessing slope stability. A three‐layer slope is selected as an example for further discussion. PWP distribution and factor of safety are calculated, considering the effects of saturated hydraulic conductivity and thickness of the upper layer, intensity of antecedent and subsequent rainfall, and varied soil unit weight along the depth. The slope stability subjected to rainfall effects is consistent with the variation of PWP. The proposed analytical solutions provide a simple and practical avenue for computing PWP distribution and evaluating the stability of multi‐layered slopes under rainfall conditions, which can also serve as a benchmark for numerical solutions.

Effect of toroidal mode coupling on explosive dynamics of m/n = 3/1 double tearing mode

The CLT code was used to quantitatively study the impact of toroidal mode coupling on the explosive dynamics of the m/n = 3/1 double tearing mode. The focus of this study was on explosive reconnection processes, in which the energy bursts and the main mode no longer dominates when the separation between two rational surfaces is relatively large in the medium range. The development of higher m and n modes is facilitated by a relatively large separation between two rational surfaces, a small q min (the minimum value of the safety factor), or low resistivity. The relationships between the higher m and n mode development, explosive reconnection rate, and position exchange of 3/1 islands are summarized for the first time. Separation plays a more important role than q min in enhancing the development of higher m and n modes. At a relatively large separation, the good development of higher m and n modes greatly reduces the reconnection rate and suppresses the development of the main mode, resulting in the main mode not being able to develop sufficiently large to generate the position changes of 3/1 islands.

Online Base Transportation Service Quality and Customers Satisfaction Analysis

This study investigates how customer satisfaction is influenced by various service quality factors, including price, convenience, safety, and information and communication technologies (ICT). The study focused on Go-Jek users in Airmadidi and its surrounding areas, encompassing both frequent and first-time users. Data were collected using a Google Forms questionnaire from a sample of 315 respondents selected through convenience sampling. Prior to distribution, the validity and reliability of the questionnaire were tested with 37 respondents in a pilot study. Pearson correlation coefficients were calculated to assess the relationships between the different service quality attributes (safety, price, convenience, ICT) and customer satisfaction. The results revealed a strong relationship between customer satisfaction and the service quality factors of safety, price, convenience, and ICT. Among these factors, ICT showed the strongest association with customer satisfaction.

Slope stability analysis of colluvial deposits along the Muketuri-Alem Ketema Road, Northern Ethiopia

Slope failures are a significant natural geohazard in hilly and mountainous regions, often resulting in loss of life and infrastructure damage. The Muketuri-Alem Ketema road in Ethiopia is particularly vulnerable to landslides due to colluvial deposits on steep slopes from the higher northeastern plots to the lower Jemma River valley. This study investigates the characteristics of colluvial soil and evaluates the stability of slopes prone to landslides. It combines geophysical data, penetrometer tests, laboratory analyses, Google Earth images, and detailed field visits to assess the soil and bedrock composition and structure. Numerical methods, including limit equilibrium (Bishop, Janbu, Spencer, and Morgenstern-Price methods) and finite element methods, were used to analyze slope sections under various saturation conditions and simulate different rainfall patterns. The results indicate that the Bishop, Morgenstern-Price, and Spencer methods produce similar safety factors with minimal differences (<0.3%), while the Janbu method shows more significant variation (1.5%–5.6%). Safety factor differences for sections A-A and B-B range from 5.26% to 9.86% and 3.5%–4.7%, respectively. Simulations reveal that short-term saturation significantly reduces the stability of the upper slope layer by 20%–46.76%, and long-term saturation decreases the entire slope section by 26.81%–46.76% compared to dry conditions due to increased pore water pressure and self-weight. Long-term saturation effects, combined with dynamic loads, can further reduce colluvial soil stability by over 50% compared to a dry static state. The finite element method predicts larger failure zones than limit equilibrium methods, emphasizing the need for accurate predictions to characterize slope behavior during failure and inform stabilization decisions. This study provides crucial data for maintaining and planning the Muketuri-Alem Ketema Road, highlighting slope performance over time and the effectiveness of stabilization techniques.

Stability evaluation method of gasification coal pillar under thermal coupling condition for prevention of environment secondary pollution

The instability of gasification coal pillars can easily induce the further development of water-conducting fractures, which leads to the connection of gasification combustion space and aquifer, and then causes groundwater pollution. Therefore, it is crucial to assess the stability of gasification coal pillar to forestall the potential risk of environmental contamination resulting from underground coal gasification. In this paper, based on the shape of the combustion space area of underground coal gasification, considering the influence of the mechanical properties of the coal pillar and the temperature field under the condition of thermal coupling, the calculation method of the yield zone width of gasification coal pillar is proposed. Considering the destabilizing factors affecting the coal pillar and the relationship between actual and ultimate bearing capacities after stripping and yielding, a stability evaluation method for the ‘hyperbolic’ coal pillar is proposed. Additionally, the effects of various factors on the stripping, yielding, and safety factor of the coal pillar are analyzed. The new method was applied to the Ulanqab underground coal gasification test site, which proved its effectiveness. The research results are of great practical significance for designing underground coal gasification production and preventing environmental pollution.

Effects of degraded durability on the long-term stability of in-service slopes with reinforced concreted support structures

Engineering slope stability issues typically exhibit the impact of deteriorating durability on the susceptibility of slopes to failure. A thorough investigation was essential to explore theoretical and experimental aspects of slope durability degradation and its implications on long-term stability. Hence, a durability model was developed to accommodate slope stabilization using reinforced concrete (RC) support structures. This model was grounded in classical durability principles for RC structures. Subsequently, a model test was conducted to compare the responses of a standard slope model with a weakened counterpart subjected to environmental impacts. According to the proposed methodology for slope durability and stability, a case study involving future durability and stability predictions was performed. It was found that the theoretical solutions for the carbonation or neutralization (CN) velocity, depth, and penetration time agreed well with model test results. The slope surface displacements of the weakened slope with deteriorating coefficients between 0.6 and 0.9 were 4 to 8 times those of the standard slope, demonstrating significant degradation in stability. The case study indicated a steady reduction in the safety factor, at a rate of 2.3 to 2.4‰ per year throughout the slope’s service life. Finite-element-based predictions also suggested the potential for corrosion of slope anchor bolts within 20 years and breakage within 30 years, at an average rate of 7.5‰ per year in the ultimate bearing capacity. These findings highlight the need for timely maintenance and reinforcement interventions to ensure the long-term durability of operational slopes.

Optimal mine pitwall profiles in jointed anisotropic rock masses

ABSTRACT A new methodology based on the limit analysis upper bound method for the topological optimisation of slopes is presented, to determine geotechnically optimal slope profiles in anisotropic jointed rock masses. The methodology accounts for the effects of discontinuities such as joints, bedding planes, and tension cracks. We applied this methodology to the context of open pit mines, with the goal of achieving geotechnically optimal pitwall profiles. The optimal profiles maximise the Overall Slope Angle (OSA) while maintaining a prescribed Factor of Safety (FoS) and satisfying the geometric constraints imposed by benches and ramps. The method, implemented in the software OptimalSlope, utilises direction-dependent cohesion and internal friction angle parameters to replicate the effect of joints on slope stability. Key inputs include joint orientation, non-persistence, and probability of occurrence. We tested the methodology on a Mexican open pit mine to be excavated into Cretaceous siltstone featuring eight different joint sets and a primary bedding plane. Optimal pitwall profiles were determined for various combinations of bedding dip angles (0°, 15°, 30°, 45°, 60°, 75°, 90°) and mine pitwall orientations (hanging wall, footwall, side walls), considering the three-dimensional kinematics of the joints through anisotropic functions of cohesion and friction angle. Results indicate that the optimal pitwall profiles generally exhibit higher OSA compared to planar profiles with the same FoS, except in one bedding dip direction. Additionally, stability analyses performed using Rocscience Slide2 independently verified the FoS values of the optimal profiles.