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

The safety factor is a crucial quantitative index for evaluating slope stability.However,the traditional calculation methods suffer from unreasonable assumptions,complex soil composition,and inadequate consideration of the influencing factors,leading to large errors in their calculations.Therefore,a stacking ensemble learning model(stacking-SSAOP)based on multi-layer regression algorithm fusion and optimized by the sparrow search algorithm is proposed for predicting the slope safety factor.In this method,the density,cohesion,friction angle,slope angle,slope height,and pore pressure ratio are selected as characteristic parameters from the 210 sets of established slope sample data.Random Forest,Extra Trees,AdaBoost,Bagging,and Support Vector regression are used as the base model(inner loop)to construct the first-level regression algorithm layer,and XGBoost is used as the meta-model(outer loop)to construct the second-level regression algorithm layer and complete the construction of the stacked learning model for improving the model prediction accuracy.The sparrow search algorithm is used to optimize the hyperparameters of the above six regression models and correct the over-and underfitting problems of the single regression model to further improve the prediction accuracy.The mean square error(MSE)of the predicted and true values and the fitting of the data are compared and analyzed.The MSE of the stacking-SSAOP model was found to be smaller than that of the single regression model(MSE=0.03917).Therefore,the former has a higher prediction accuracy and better data fitting.This study innovatively applies the sparrow search algorithm to predict the slope safety factor,showcasing its advantages over traditional methods.Additionally,our proposed stacking-SSAOP model integrates multiple regression algorithms to enhance prediction accuracy.This model not only refines the prediction accuracy of the slope safety factor but also offers a fresh approach to handling the intricate soil composition and other influencing factors,making it a precise and reliable method for slope stability evaluation.This research holds importance for the modernization and digitalization of slope safety assessments.

Factor of safety of strain-softening slopes

Stability analysis of strain-softening slopes is carried out using the shear strength reduction method and Mohr-Coulomb model with degrading cohesion and friction angle.The e ffect of strain-softening behavior on the slope factor of safety is investigated by performing a series of analyses for various slope geometries and strength properties.Stability charts and equations are developed to estimate the factor of safety of strain-softe ning slopes from the results of traditional stability analysis based on perfectly-plastic behavior.Two example applications including an open pit mine in weak rock and clay shale slope with daylighting bedding planes are presented.The results of limit equilibrium analysis and shear strength reduction method with perfectly-plastic models were in close agreement.Using perfectly-plastic models with peak strength properties led to overly optimistic results while adopting residual strength properties gave excessively conservative outcomes.The shear strength reduction method with a strain-softening model gave realistic factors of safety while accounting for the process of strength degradation.

Hysteresis of Dam Slope Safety Factor under Water Level Fluctuations Based on the LEM Coupled with FEM Method

Water level variations have caused numerous dam slope collapse disasters around the world,illustrating the large influence of water level fluctuations on dam slopes.The required indoor tests were conducted and a numerical model of an actual earth-filled dam was constructed to investigate the influences of the water level fluctuation rate and the hysteresis of the soil-water characteristic curve(SWCC)on the stability of the upstream dam slope.The results revealed that the free surface in the dam body for the desorption SWCC during water level fluctuations was higher than that for the adsorption SWCC,which would be more evident at higher water levels.The safety factor of the upstream dam slope initially decreased and then increased for the most dangerous water level as the water level rose and fell.The water level fluctuation rate mainly influenced the initial section of the safety factor variation curve,while the SWCC hysteresis mainly affected the minimum safety factor of the water level fluctuations.The desorption SWCC is suggested for engineering design.Furthermore,a quick prediction method is proposed to estimate the safety factor of upstream dam slopes with identical structures.

Toroidicity Dependence of Tokamak Edge Safety Factor and Shear

Using a simple analytical model equilibrium, the dependence of tokamak edge safety factor qedge which can be understood as qa for a limiter device or 595 for a divertor device, and the shear value are calculated and compared with the ITRE-recommended formula. This dependence relation is useful in designing the medium and small aspect ratio tokamaks and reactors.

Method of Calculating the Safety Factor Profile on the HT-7 Tokamak

A method of calculating the safety profile on the HT-7 tokamak has been described in this paper. It is derived from Maxwell's equations, among which we-mainly use .two of them: one is the magnetic field diffusion equation, and the other is Ampere's Law. This method can be also used to evaluate the safety factor on other devices with a circular cross sections. It is helpful to the study of the plasma MHD behavior on the HT-7 tokamak.

Safety factors for anterior pedicle screw fixation tunnel in axis

Objective To investigate feasibility and safety of anterior pedicle screw fixation tunnel in the axis so as to provide theoretic evidence for further clinical application.Methods Thirty-two dry axis specimens were used foranterior

A Calculation Method of Double Strength Reduction for Layered Slope Based on the Reduction of Water Content Intensity

The calculation of the factor of safety(FOS)is an important means of slope evaluation.This paper proposed an improved double strength reductionmethod(DRM)to analyze the safety of layered slopes.The physical properties of different soil layers of the slopes are different,so the single coefficient strength reduction method(SRM)is not enough to reflect the actual critical state of the slopes.Considering that the water content of the soil in the natural state is the main factor for the strength of the soil,the attenuation law of shear strength of clayey soil changing with water content is fitted.This paper also establishes the functional relationship between different reduction coefficients.Then,a USDFLD subroutine is programmed using the secondary development function of finite element software.Controlling the relationship between field variables and calculation time realizes double strength reduction applicable to the layered slope.Finally,by comparing the calculation results of different examples,it is proved that the stress and displacement distribution of the critical slope state obtained by the improved method is more realistic,and the calculated safety factor is more reliable.The newly proposedmethod considers the difference of intensity attenuation between different soil layers under natural conditions and avoids the disadvantage of the strength reduction method with uniform parameters,which provides a new idea and method for stability analysis of layered and complex slopes.

Probabilistic Analysis of Slope Using Finite Element Approach and Limit Equilibrium Approach around Amalpata Landslide of West Central, Nepal

The stability study of the ongoing and recurring Amalpata landslide in Baglung in Nepal’s Gandaki Province is presented in this research. The impacted slope is around 200 meters high, with two terraces that have different slope inclinations. The lower bench, located above the basement, consistently fails and sets others up for failure. The fluctuating water level of the slope, which travels down the slope masses, exacerbates the slide problem. The majority of these rocks are Amalpata landslide area experiences several structural disruptions. The area’s stability must be evaluated in order to prevent and control more harm from occurring to the nearby agricultural land and people living along the slope. The slopes’ failures increase the damages of house existing in nearby area and the erosion of the slope. Two modeling techniques the finite element approach and the limit equilibrium method were used to simulate the slope. The findings show that, in every case, the terrace above the basement is where the majority of the stress is concentrated, with a safety factor of near unity. Using probabilistic slope stability analysis, the failure probability was predicted to be between 98.90% and 100%.

Comparative Study on Structural Redundancy of Cable-Stayed and Extradosed Bridges Through Safety Assessment of Their Stay Cables

This study provides new insights into the comparison of cable-stayed and extradosed bridges based on the safety assessment of their stay cables.These bridges are often regarded as identical structures owing to the use of inclined cables;however,the international standards for bridge design stipulate different safety factors for stay cables of both types of bridges.To address this misconception,a comparative study was carried out on the safety factors of stay cables under fatigue and ultimate limit states by considering the effects of various untoward and damaging factors,such as overloading,cable loss,and corrosion.The primary goal of this study is to describe the structural disparities between both types of bridges and evaluate their structural redundancies by employing deterministic and nondeterministic methods.To achieve this goal,three-dimensional finite-element models of both bridges were developed based on the current design guidelines for stay cables in Japan.After the balanced states of the bridge models were achieved,static analyses were performed for different safety factors of stay cables in a parametric manner.Finally,the first-order reliability method and Monte Carlo method were applied to determine the reliability index of stay cables.The analysis results show that cable-stayed and extradosed bridges exhibit different structural redundancies for different safety factors under the same loading conditions.Moreover,a significant increase in structural redundancy occurs with an incremental increase in the safety factors of stay cables.

Finite element model with imposed slip surfaces for earth mass safety evaluation

The study of earth masses requires numerical methods that provide the quantification of the safety factor without requiring detrimental assumptions. For that, equilibrium analysis can perform fast computations but require assumptions that limit its potentiality. Limit analysis does not require detrimental assumptions but are numerically demanding. This work provides a new approach that combines the advantage of both the equilibrium method and the limit analysis. The defined hybrid model allows probabilistic analysis and optimization approaches without the assumption of interslice forces. It is compared with a published case and used to perform probabilistic studies in both a homogeneous and a layered foundation. Analyses show that the shape of the density probability functions is highly relevant when computing the probability of failure, and soil elasticity hardly affects the safety of factor of the earth mass.

Deep learning approaches to recover the plasma current density profile from the safety factor based on Grad–Shafranov solutions across multiple tokamaks

Many magnetohydrodynamic stability analyses require generation of a set of equilibria with a fixed safety factor q-profile while varying other plasma parameters.A neural network(NN)-based approach is investigated that facilitates such a process.Both multilayer perceptron(MLP)-based NN and convolutional neural network(CNN)models are trained to map the q-profile to the plasma current density J-profile,and vice versa,while satisfying the Grad–Shafranov radial force balance constraint.When the initial target models are trained,using a database of semianalytically constructed numerical equilibria,an initial CNN with one convolutional layer is found to perform better than an initial MLP model.In particular,a trained initial CNN model can also predict the q-or J-profile for experimental tokamak equilibria.The performance of both initial target models is further improved by fine-tuning the training database,i.e.by adding realistic experimental equilibria with Gaussian noise.The fine-tuned target models,referred to as fine-tuned MLP and fine-tuned CNN,well reproduce the target q-or J-profile across multiple tokamak devices.As an important application,these NN-based equilibrium profile convertors can be utilized to provide a good initial guess for iterative equilibrium solvers,where the desired input quantity is the safety factor instead of the plasma current density.

Estimation of the behavior factor of existing RC-MRF buildings

In recent years, several research groups have studied a new generation of analysis methods for seismic response assessment of existing buildings. Nevertheless, many important developments are still needed in order to define more reliable and effective assessment procedures. Moreover, regarding existing buildings, it should be highlighted that due to the low knowledge level, the linear elastic analysis is the only analysis method allowed. The same codes（such as NTC2008, EC8） consider the linear dynamic analysis with behavior factor as the reference method for the evaluation of seismic demand. This type of analysis is based on a linear-elastic structural model subject to a design spectrum, obtained by reducing the elastic spectrum through a behavior factor. The behavior factor（reduction factor or q factor in some codes） is used to reduce the elastic spectrum ordinate or the forces obtained from a linear analysis in order to take into account the non-linear structural capacities. The behavior factors should be defined based on several parameters that influence the seismic nonlinear capacity, such as mechanical materials characteristics, structural system, irregularity and design procedures. In practical applications, there is still an evident lack of detailed rules and accurate behavior factor values adequate for existing buildings. In this work, some investigations of the seismic capacity of the main existing RC-MRF building types have been carried out. In order to make a correct evaluation of the seismic force demand, actual behavior factor values coherent with force based seismic safety assessment procedure have been proposed and compared with the values reported in the Italian seismic code, NTC08.

Safety Level and Reliability Index for Bank Slope Stability

Based on statistics and analysis of the safety factor of unstable bank slopes, the relation between safety level and reliability index of stability is studied and discussed, and then the elementary calibrating calculation is carried out to the levels of safety and reliability for bank slope stability in the range of safety factors stipulated in existing China Technical Specifications for Port Engineering - Foundation Part (1987) and to those reached by some stable bank slopes already built. The results show that the reliability index beta in the effective stress method is able to reach a high value of 2.4 similar to 4.1 (mid-value 3.25), while the value of beta in other three kinds of total stress method can just reach a lower value of 0.5 similar to 2.8 (mid-value 1.65), which are in conformity with the engineering experience in China, and thus acceptable. Some suggestions are also given in this paper to the adoption of the value of beta(0)-objective reliability index for bank slope stability.

Effect of Food Safety Training on Achieving Good Hygiene Practices in Restaurants in the Emirates of Dubai

Food safety,specifically in restaurants,is becoming a key public health priority because of the increased number of meals eaten outside the home.Foodborne illness prevention thus is a significant concern and a public health priority in the United Arab Emirates,particularly Dubai,because of the extensive tourism industry.The purpose of the study was to evaluate the effectiveness of using demonstrations in training sessions to improve food safety knowledge and practices amongst food handlers.A descriptive and quantitative approach has been applied to collect the quantifiable information related to the research study.This has been further analyzed using the correlation tests to gather the required data.On comparison of the pre-test scores between the intervention and the control group,the t-test analysis showed significant difference in the level of food safety knowledge between the two groups.Pre-test score for the control group was 78.33 and post-test score was 104.66.In the case of the intervention group,pre-test score was 91.37 and post-test score was 130.75.The scores of food handlers’food safety practice for control group:pre-treatment score was 470 and post-treatment score was 646.For intervention group:pre-test score was 723 and post-test score was 1,056.The study concluded that training with demonstration techniques is an effective way of improving compliance with food safety guidelines.It has been understood that training helps in improving the performance of the employees while reducing the foodborne diseases and maintaining hygiene in the food.The study recommends every restaurant needs to provide regular trainings to the employees so that the restaurants can maintain hygiene and food safety practices.

A new anchor-siphon drainage combined method used for slope stabilization

A new anchor-siphon drainage combined method used for slope stabilization is proposed in this paper.It includes an anchoring section and a siphon drainage section.The novelty of the anchor-siphon drainage combined method is the realization of the drainage and anchoring in the one inclined borehole.The engineering cost of drilling and the resulting disturbance to the slope is reduced.To validate the feasibility of the proposed method,a numerical method that combines the pore water pressure distribution after siphon drainage and the anchoring force of the anchoring section is used to evaluate the safety of the slope with the anchor-siphon drainage method.The proposed method was illustrated and validated with the Hongpu Village landslide,in Tonglu County,Zhejiang Province,in China.Compared with the common anchor bar with the same length in the anchoring section,the factor of safety(FOS)for Hongpu Village slope with anchorsiphon drainage is increased by 0.085.The calculation method of the optimal length ratio between the drainage section and the anchoring section and its influencing factors were studied.For the different design parameters,there is always an optimal length ratio of the drainage section.Compared with the siphon drainage and full-length anchor bar with the same borehole length,the anchor-siphon drainage combined method shows better landslide prevention ability.Moreover,when the optimized parameters with a bond strength of 560kPa,a borehole inclination of 35°,and no reduction in length are used,the calculated safety factor is 1.316,which is significantly higher than the FOS of 1.131 for the slope with siphon drainage.

Stability evaluation method of large cross-section tunnel considering modification of thickness-span ratio in mechanized operation

Purpose-This study aims to research the large cross-section tunnel stability evaluation method corrected after considering the thickness-span ratio.Design/methodology/approach-First,taking the Liuyuan Tunnel of Huanggang-Huangmei High-Speed Railway as an example and taking deflection of the third principal stress of the surrounding rock at a vault after tunnel excavation as the criterion,the critical buried depth of the large section tunnel was determined.Then,the strength reduction method was employed to calculate the tunnel safety factor under different rock classes and thickness-span ratios,and mathematical statistics was conducted to identify the relationships of the tunnel safety factor with the thickness-span ratio and the basic quality(BQ)index of the rock for different rock classes.Finally,the influences of thickness-span ratio,groundwater,initial stress of rock and structural attitude factors were considered to obtain the corrected BQ,based on which the stability of a large cross-section tunnel with a depth of more than 100 m during mechanized operation was analyzed.This evaluation method was then applied to Liuyuan Tunnel and Cimushan No.2 Tunnel of Chongqing Urban Expressway for verification.Findings-This study shows that under different rock classes,the tunnel safety factor is a strict power function of the thickness-span ratio,while a linear function of the BQ to some extent.It is more suitable to use the corrected BQ as a quantitative index to evaluate tunnel stability according to the actual conditions of the site.Originality/value-The existing industry standards do not consider the influence of buried depth and span in the evaluation of tunnel stability.The stability evaluation method of large section tunnel considering the correction of overburden span ratio proposed in this paper achieves higher accuracy for the stability evaluation of surrounding rock in a full or large-section mechanized excavation of double line high-speed railway tunnels.

Slope Stability Analysis: Case of the West Wall of the EMZ Pit at the Essakane Gold Mine in Burkina Faso (West Africa)

Knowledge of the state of stability of mining pits is both a basic condition, an essential axis and a safety benchmark for mining operations. This stability is largely based on the knowledge of the rock mass sheltering the mining works and this requires a perfect characterization of all of its structural formations through mapping (manual or digital). The families of discontinuities, namely family 1 (bedding), family 2 (Joint 2) and family 3 (Joint 1) obtained through structural mapping in the Essakane open pit mine, made it possible to analyze the failure modes at the origin of rock instabilities. The respective dips of these different directional families are: 77˚ - 85˚/N 058˚ - 068˚, 66˚ - 74˚/N 133˚ - 143˚, 25˚ - 35˚/N115˚ - 130˚. An average safety factor of 4.3 was estimated for the area with a quality of the rock mass (RMR) estimated at 47. The results obtained reflect on the one hand the risks of instability associated with the quality of the rock mass studied and on the other hand highlights the state of stability of the study area.

Study of Slope Stability Using the Bishop Slice Method: An Approach Combining Analytical and Numerical Analyses

The importance of slope stability in civil engineering cannot be underestimated, as failure of these structures can result in significant damage to downstream infrastructure and property. In this study, we used the Bishop slice method, combining both an analytical approach and a numerical approach using the SLOPE/W module of the Geostudio 2018 R2 software. The results obtained from these two methods showed that increasing soil cohesion helps to improve slope stability. The safety coefficients obtained by the analytical method vary between 0.621 and 1.422, while those obtained by the numerical method vary between 0.622 and 1.447, for cohesion values ranging from 4 kPa to 20 kPa. The results obtained by these two methods show a linear relationship between the safety coefficients and soil cohesion. The equation of the analytical method is y = 0.0496x + 0.4407, while that of the numerical method is y = 0.0512x + 0.4357. The results of the analytical approach indicate that a safety coefficient of 1.5 is reached when the cohesion reaches a value of 22 kPa, while the numerical approach shows a safety coefficient of 1.5 reached at a cohesion of 21 kPa. The difference between these two cohesion values can be explained by the number of slices used, which is smaller in the analytical method. However, the equation derived from the analytical method can be used as a general guide to assess the evolution of the safety coefficient of an overloaded slope in long-term behaviour with an increase in cohesion. However, it is important to stress the importance of verification using specialised software based on the finite element method.

The Hidden Earthquake Induced Liquefaction Risks in the Rohingya Refugee Camp Hills & Surrounding Areas of Ukhiya, Cox’s Bazar, Bangladesh—A Geotechnical Engineering Approach

Liquefaction is one of the major catastrophic geohazards which usually occurs in saturated or partially saturated sandy or silty soils during a seismic event. Evaluating the potential liquefaction risks of a seismically prone area can significantly reduce the loss of lives and damage to civil infrastructures. This research is mainly focused on the earthquake-induced liquefaction risk assessment based on Liquefaction Potential Index (LPI) values at different earthquake magnitudes (M = 5.0, 7.0 and 8.0) with a peak ground acceleration (amax) of 0.28 g in the Rohingya Refugee camp and surrounding areas of Ukhiya, Cox’s Bazar, Bangladesh. Standard Penetration Test (SPT) results have been evaluated for potential liquefaction assessment. The soils are mainly composed of very loose to loose sands with some silts and clays. Geotechnical properties of these very loose sandy soils are very much consistent with the criteria of liquefiable soil. It is established from the grain size analysis results;the soil of the study area is mainly sand dominated (SP) with some silty clay (SC) which consists of 93.68% to 99.48% sand, 0.06% to 4.71% gravel and 0% to 6.26% silt and clay. Some Clayey Sand (SC) is also present. The silty clay can be characterized as medium (CI) to high plasticity (CH) inorganic clay soil. LPI values have been calculated to identify risk zones and to prepare risk maps of the investigated area. Based on these obtained LPI values, four (4) susceptible liquefaction risk zones are identified as low, medium, high and very high. The established “Risk Maps” can be used for future geological engineering works as well as for sustainable planning, design and construction purposes relating to adaptation and mitigation of seismic hazards in the investigated area.

Landslide susceptibility mapping using the infinite slope,SHALSTAB,SINMAP,and TRIGRS models in Serra do Mar,Brazil

Slope failure triggered by heavy rainfall is very common in tropical and subtropical regions and a cause of major social and economic damage.Landslide susceptibility maps can be generated using geographical information systems(GIS)and limit equilibrium slope stability models coupled or not to hydrological equations.This study investigated the efficacy of four models used for slope stability analysis in predicting landslide-susceptible areas in a GIS environment.The selected models are the infinite slope,the shallow slope stability model(SHALSTAB),the stability index mapping(SINMAP),and the transient rainfall infiltration and grid-based regional slope-stability(TRIGRS).For comparisons,the authors(a)included the infinite slope equation in all models,(b)clearly defined input parameters and failure triggering mechanisms for each simulation(soil depth,water table height,rainfall intensity),(c)determined appropriate values for each model to obtain stability levels that represented similar hydrogeotechnical conditions,and(d)considered upper-third areas of landslide scars to estimate the reliability of susceptibility maps using validation indices.An intense rainfall event occurred in Serra do Mar,Brazil in January 2014 triggered hundreds of landslides and was used for back analysis and evaluation of the slope stability analysis models.When rainfall intensity is not considered,the four models produced very similar results.The most reliable landslide susceptibility map was generated using TRIGRS and considering the granite residual granite soils geological-geotechnical unit,subjected to a rainfall intensity of 210 mm for 2 h under unsaturated conditions.