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The presence of oil contamination causes changes in mechanical properties of clayey soil trenches with low liquid limits (CL) such as stress-strain behavior, rupture plain position, plastic zone, and strain energy for soil trenches compared with uncontaminated soils. These changes usually lead to a lower factor of safety against failure and expansion of the plastic zone. The effects of crude oil contamination on the soil shear strength were evaluated by direct shear and plate load tests for various clays and sandy soils. In this research, a numerical finite element modeling in ABAQUS software was used to estimate the effect of oil contamination in the range of 0 to 16% (0%–4%–8%–12%–16%) on the stability safety factor of vertical clayey trenches with heights of 3 m, 4 m, 5 m, and 6 m, and the results were compared with results of a limit state analysis. The findings of the limit equilibrium method show that adding 4% of oil contamination to a clayey trench will decrease 62% of its critical depth. Also, the numerical analysis results show that adding oil contamination in the range of 0 to 16% to the clayey soil will increase the maximum displacements of the trenches to five times their clean state. [ABSTRACT FROM AUTHOR]

Rigid retaining walls with polyline backs are possibly used in filling engineering, and some types of these walls may have better stability than ordinary gravity walls with planar backs. Aiming at the active earth pressure on polyline-back walls under the translation mode, an analytical method within the frame of limit equilibrium is provided according to the potential two slip surfaces intersected in the retained backfill. The proposed method focuses on the minimum slide-resisting factor of safety of the polyline-back wall to be the objective function, and it can be performed easily using the nonlinear programming approach. Analysis results of some examples show that the proposed earth pressure is close to those obtained using the test and numerical methods with an average error of about 15%. The platform width and the ratio of the upper to lower wall height in the counterweight wall have more obvious influences on earth pressure than the slip surfaces. The overall and local critical slip surfaces are considerably influenced by the lower-back and backfill surface inclinations, respectively. The counterweight wall is the optimum configuration for the overall sliding stability among the compared five polyline-back walls due to its outward-extending platform and positively inclined lower back. Practical Applications: This work provides a calculation method for the active earth pressure on rigid walls with polyline backs under wall translation, which holds practical significance for geotechnical engineers or practitioners in filling engineering such as embankments. The proposed method can analytically solve the active earth pressure on different segments of the polyline back of gravity walls and the two critical slip surfaces intersected in the retained soil. As a result, the slide-resisting stability of the wall can be analyzed in the design. The proposed method can be used further to compare possible different types of polyline backs of a wall and then for the quick optimization design of the gravity wall. Analysis results of an example show that the counterweight wall is the optimum configuration for overall sliding stability due to its outward-extending platform and positively inclined lower back. In brief, this work can provide a significant reference for the practical design of rigid walls with polyline backs, such as counterweight walls and hunchbacked walls, based on the easily operated limit equilibrium methods. [ABSTRACT FROM AUTHOR]

A geotextile-reinforced retaining wall is a geotechnical structure with many design parameters. Hence, the uncertainty of the input parameters considerably affects the design of these structures. On the other hand, when the number of uncertain parameters increases, the time of this analysis increases drastically. Accordingly, the current study used an analytical method, namely, jointly distributed random variables (JDRV) method, that requires less running time than the simulation methods for stochastic analysis. For this purpose, stochastic analysis of the geotextile-reinforced retaining wall was carried out based on the limit equilibrium method (LEM), with soil parameters considered as uncertain variables. To verify the results, the probability density functions (PDFs) of the wall safety factors were compared with the Monte Carlo simulation (MCS). Next, to assess the effect of the external and internal stability modes on system reliability, the system reliability index was determined using the sequential compounding method (SCM). The results of the system reliability analysis revealed that, among the reliability indices of the components, the minimum values are attributed to the bearing capacity. The correlation between the rupture and pullout safety factors exhibited the maximum correlation, indicating that they are more dependent components than others. Based on the stochastic sensitivity analysis, the internal friction angle emerged as the most influential in the external and internal safety factors. [ABSTRACT FROM AUTHOR]

In this paper, a discussion on the applicability and limitations of the limit equilibrium method is presented. In this manner, the reliability of a concrete arch dam-foundation system under static loading is evaluated by considering a set of potentially moveable rock wedges in the foundation. The safety of the system is assessed utilizing a quasi-analytical method, which employs the limit equilibrium method and numerical analysis to calculate the sliding safety factors and the dam trust forces, respectively. The reliability is evaluated using the Latin Hypercube Sampling method. Random variables in the system are the friction angle, cohesion, and the Grout Curtain Efficiency Coefficient. In the end, the influence of two parametric variables of discontinuities, elastic slip and rock mass deformability modulus, on the rock wedges' sliding safety factor is evaluated by comparing the results of the quasi-analytical method with the purely numerical method. The results show that in the case of complicated geotechnical conditions, the limit equilibrium method may not reflect real-world failure scenarios. [ABSTRACT FROM AUTHOR]

Compared with the traditional "earth pressure balance" tunneling mode, the "air-pressure assisted" mode of shield tunneling has a more complex mechanism for maintaining excavation face balance, with significant differences in ground deformation and tunneling parameters compared to conventional full-chamber earth pressure balance tunneling mode. In order to quantitatively assess the stability of the excavation face under the air-pressure assisted tunneling mode and to determine a reasonable air-pressure setting, this study proposed an evaluation method for overall excavation face stability in the air-pressure assisted mode by using the limit equilibrium method, considering the spatial surface characteristics of the slip surface. Based on the Krabbe formula, considering the layering of the strata and the influence of groundwater, the formula for calculating gas loss was modified. In addition, a comparative tunneling test was conducted under different tunneling modes in the same strata condition, comparing the overall stability, air-pressure loss, ground settlement and tunneling parameters of the excavation face. The results showed that: according to the proposed overall stability evaluation method and the gas loss calculation method, the experimental section of this project met the overall stability requirements for air-pressure assisted tunneling. The selected air compressor had sufficient power for maintaining air-pressure stability in the strata, and the air-pressure setting met the requirements of engineering safety. Compared to the full-chamber earth pressure balance mode, the total thrust and cutterhead torque in the air-pressure assisted mode were reduced by 35% and 44%, respectively, while the advancing speed increased by 173% and energy consumption decreased by 66%. The air-pressure assisted tunneling mode resulted in a higher ground loss rate and relatively larger surface settlement. [ABSTRACT FROM AUTHOR]

To perform the stability analysis of soil slopes, the traditional limit equilibrium method (LEM) based on geostresses calculated by the standard finite element method (LEM-FEM) appears to be competitive. In LEM-FEM, the stress variables are stored at the Gaussian points within each element, so stress interpolation from the Gaussian points for each line segment of trial slip surfaces shall be inefficient for stability analysis of soil slope. To improve the accuracy and efficiency of stress interpolation, an implicit stabilized node-based smoothed finite element method (NsFEMstab) in conjunction with 3-node triangular (T3) elements, in which stress variables are stored at the element nodes, is implemented to calculate the stresses at each line segment. Furthermore, a novel method of LEM-NsFEMstab is developed by replacing the standard FEM in LEM-FEM with NsFEMstab. Based on four plane-strain slope examples, the stability analysis results disclose that the factor of safety (FOS) and the slip surfaces predicted by LEM-NsFEMstab agree well with those predicted by LEM-FEM in conjunction with 6-node triangular (T6) elements. Additionally, the search of the critical slip surface is accelerated using the OpenMP parallel platform. Compared to the serial implementation of LEM-FEM(T6) and the serial implementation of LEM-NsFEMstab, the computational efficiency of the parallel version of LEM-NsFEMstab may be increased by 5~7 and 4~6 times, respectively, and based on comparisons of threads parallel performance, it is found that one half of the total number of CPU threads can be utilized to achieve optimal computational efficiency. [ABSTRACT FROM AUTHOR]

The support pressure at a shield tunnel face is significant for the stability of the shield excavation and prediction of ground disturbance. This study presents an optimization measure that relies on the three-dimensional (3D) limit equilibrium method (LEM) to determine the reasonable support pressure of the shield tunnel face. The predetermined support pressure is subsequently incorporated into the finite-element (FE) model, and the ground disturbance that is induced by the shield excavation could be estimated by the FE simulation. The face support pressure that is obtained from the optimization measure aligns remarkably well with those derived from other methodologies, therefore confirming its efficacy. Furthermore, the numerical results demonstrate that the support pressure, as determined by the optimization measure, provides superior control on the ground disturbance. To further estimate the sensitivity of the tunnel buried depth and soil strength in relation to the ground disturbance, orthogonal testing is conducted. The outcomes of this orthogonal testing inform the development of a predictive approach for evaluating ground disturbances that are caused by the shield excavation, which is then validated by comparing it with previous works. The findings of this study serve as a valuable asset in facilitating the rapid prediction of ground disturbance that is induced by shield excavation. [ABSTRACT FROM AUTHOR]

The analysis of slope failure modes is essential for understanding slope stability. This study investigated the failure modes and triggering factors of a rock slope using the limit equilibrium method, finite differences method, and exploratory factor analysis. First, the limit equilibrium method was used to identify potential sliding surfaces. Then, the finite differences method was employed to study deformation and failure features in a slope. Stability factors were calculated considering specific conditions such as rainfall, prestressing loss, and earthquakes using the strength reduction method. Finally, exploratory factor analysis was utilized to identify the triggering factors of each failure mode. The results revealed that failure modes were categorized into two types based on the positions of the sliding surface. The main triggering factors for Failure Mode 1 were rainfall and prestress loss, while for Failure Mode 2 they were earthquake loading and prestress loss. This study offers a comprehensive exploration of potential failure modes and their triggering factors from mechanical and statistical perspectives, enriching our understanding of potential failure modes in rock slopes. [ABSTRACT FROM AUTHOR]

This paper introduces a numerical investigation into the stability analysis of soil nailed slopes. It establishes a simplified framework within the limit equilibrium method, focusing on the physical distribution of tension force along nails. MATLAB® was adapted for the Analysis of Soil Nailed Walls (ASNW) based on Bishop's method, with major command loops optimized through 'array operations'. Employing K-fold cross-validation, five regression models predicted the maximum tensile force (Tmax), revealing Gaussian process regression (GPR) as the best model based on root mean square error and r-squared metrics. To capture the amount of uncertainty in the nail load model, we have used a clustering method for estimating the measured Tmax. Self Organizing Map (SOM) was employed for clustering the nail load dataset. We randomly generated Tmax between the measured Tmax obtained by SOM and the predicted Tmax gained by the GPR model for each soil nail. We apply these loads in ASNW program to compute the Factor of Safety, and finally estimate system failure probability for 35 different nail layouts. A parametric study with a uniform nail layout explores the impact of nail length on system failure probability. Results show diminishing significance of nail length on failure probability beyond a nominal length. [ABSTRACT FROM AUTHOR]

Research on the stability of tailings dam is often achieved through the finite element method with strength reduction. The influence of shear strength parameters(c) of tailings dam stability varies. In this paper, the theory of shortest path strength reduction is introduced to conduct a stability analysis of a large tailings dam in Northeast China. The main conclusions are as follows: 1) Approximating the actual unit weight of tailings using Optum G2, stability analysis of tailings dam with shortest path strength reduction under seepage conditions is conducted to obtain the minimum safety factor of the slope and potential failure surfaces. 2) During unequal strength reduction, as the reduction ratio increases, the length of the reduction path first decreases and then increases, indicating that the minimum safety factor obtained by the shortest reduction path corresponds to the most unfavorable limit state of the tailings dam. 3) The minimum safety factor obtained through the limit analysis of shortest path strength reduction is slightly lower than the results of the Swedish slip circle method and simplified Bishop method, but overall, it is in good agreement. 4)With the increase in height of the tailings dam, the minimum safety factor continues to decrease, and the range of potential sliding bodies of the tailings dam increases, with the corresponding sliding surface expanding towards the reservoir. [ABSTRACT FROM AUTHOR]

For the excavation of a shallow tunnel in soft soil, the controllable range of the support pressure is narrow due to the small area of overburdened earth pressure, and passive failure of the tunnel face can be easily induced; therefore, the soft soil must be reinforced to increase the stability of the tunnel face. In this work, numerical simulation and theoretical analysis were adopted to explore the passive failure mechanism of a tunnel face in soft ground reinforced with a soil–cement wall. First, finite element analyses were conducted to investigate the passive failure mechanism. The impact of L1 (the distance between the tunnel face and soil–cement wall) on the passive failure mode was disclosed. Three types of failure modes—the full-penetration, partial-penetration, and non-penetration modes—were identified based on the shear failure zone and variation in Pp (the limit support pressure of passive failure) with L1. Then, analytical models based on the limit equilibrium method for the three passive failure modes were established, and formulas for predicting Pp were derived. The predictions by the formulas were validated by the numerical results, and their differences were within 10%. Both indicate that Pp achieved a maximum value when L1 = 0.2D (D is the diameter of tunnel); therefore, it is reasonable to choose a distance of 0.2D between cement walls in this engineering project. [ABSTRACT FROM AUTHOR]

Copyright of China Mining Magazine is the property of China Mining Magazine Co., Ltd. and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

AbstractIn mountain tunnels, a series of advanced reinforcement measures are often employed to maintain the stability of the tunnel face, particularly in challenging geological conditions. However, there is a lack of design theories regarding the advanced support structure for uniquely shaped tunnel faces, necessitating further exploration. Based on the limit equilibrium method, this paper presents a derivation of the mechanical model for analyzing excavation face stability considering shape changes and bolts. Additionally, a design theory for horizontal glass fiber bolts in longitudinally inclined tunnel faces is established. The reinforcement effect of the pipe shed is further considered. Finally, the proposed model is validated, and parameter analysis is conducted to guide design practices. [ABSTRACT FROM AUTHOR]

The state of Espirito Santo is the most important producer and exporter of ornamental quarry stone. In its various quarries, it uses bench heights that range from 5, 20, 50 and 100 meters. The high altitudes raise concerns about the stability of the slopes. Therefore, the study focuses on determining the value of the safety factor (SF) for these heights using the limit equilibrium method. To make this possible, the values of simple uniaxial compression, Geological Strength Index (GSI), the disturbance factor, and intact rock parameter must be obtained. To obtain the GSI, it is necessary to establish a correlation with the Rock Mass Rating, the values of which are determined using a scan line. The uniaxial compression values were treated statistically, obtaining classes at 75, 100, 125, 150, 175, and 200 Mpa. The 2D slide software was used to obtain the SF values for the respective heights. With the results obtained, these rocks do not present stability problems. The correct choice of GSI is of paramount importance for a good analysis, as it directly affects the results. Using this technique to determine safety factors is appropriate, but it is necessary to analyze more robust methods to compare the results. [ABSTRACT FROM AUTHOR]

Earthquakes are one of the main causes of bedding slope instability, and scientifically and quantitively evaluating seismic stability is of great significance for preventing landslide disasters. This study aims to assess the bedding slope stability under seismic loading and the influences of various parameters on stability using a pseudo-dynamic method. Based on the limit equilibrium theory, a general solution for the dynamic safety factor of bedding slope is proposed. The effects of parameters such as slope height, slope angle, cohesion, internal friction angle, vibration time, shear wave velocity, seismic acceleration coefficient, and amplification factor on stability are discussed in detail. To evaluate the validity of the pseudo-dynamic solution, the safety factors are compared with those given by early cases, and the results show that the safety factors calculated by the present formulation coincide better with those of previous methods. Moreover, a two-dimensional numerical solution of bedding slope based on Mohr–Coulomb's elastic–plastic failure criterion is also performed by using the finite element procedure, and the minimum safety factor is essentially consistent with the result of the pseudo-dynamic method. It is proved that the pseudo-dynamic method is effective for bedding slope stability analyses during earthquakes, and it can overcome the limitations of the pseudo-static method. [ABSTRACT FROM AUTHOR]

Face bolting has been widely utilized to enhance the stability of tunnel face, particularly in soft soil tunnels. However, the influence of bolt reinforcement and its layout on tunnel face stability has not been systematically studied. Based on the theory of linear elastic mechanics, this study delved into the specific mechanisms of bolt reinforcement on the tunnel face in both horizontal and vertical dimensions. It also identified the primary failure types of bolts. Additionally, a design approach for tunnel face bolts that incorporates spatial layout was established using the limit equilibrium method to enhance the conventional wedge-prism model. The proposed model was subsequently validated through various means, and the specific influence of relevant bolt design parameters on tunnel face stability was analyzed. Furthermore, design principles for tunnel face bolts under different geological conditions were presented. The findings indicate that bolt failure can be categorized into three stages: tensile failure, pullout failure, and comprehensive failure. Increasing cohesion, internal friction angle, bolt density, and overlap length can effectively enhance tunnel face stability. Due to significant variations in stratum conditions, tailored design approaches based on specific failure stages are necessary for bolt design. [ABSTRACT FROM AUTHOR]

This paper introduces a novel closed‐form equation (surrogate model) for approximating the Morgenstern–Price estimate of the factor of safety of homogeneous dry finite slopes with circular failure surfaces. Unlike typically used methods, the proposed equation does not require the definition of a critical failure surface, splitting the soil mass into slices, or the iterative reduction of soil resistance to the limit state. It can be easily programmed into calculators or computers and accurately determines the minimum factor of safety based on the shear strength parameters and slope geometry—meaning that it is ideally suited for integration into reliability calculations. The equation is determined parametrically for various soil parameters and slope geometry using the Morgenstern–Price method and compares favorably with conventional techniques, such as slope stability charts, limit equilibrium, and strength reduction methods (SRM). From a practical perspective, the proposed equation greatly simplifies the analysis of the slope stability as the creation of a numerical model is not required and is suited to use in the feasibility stage of a project, for example, for large linear infrastructure projects with differing slope geometries or in situations where a quick assessment is desired. [ABSTRACT FROM AUTHOR]

In hilly regions like Aizawl city, wherein houses are mostly built on slopes, the layout of building plays a crucial role in slope stability. Building failures in Aizawl often results from a) non-engineered alterations of slopes b) faulty foundation construction without soil investigation or design. Many residents build and reside on slopes without considering the soil characteristics. To address this, a study was conducted to examine the impact of two common building types - step-back buildings and step-back setback buildings on slope stability in Aizawl. Fifty different sites with varying slope geometries were analysed using Limit Equilibrium Method (LEM), considering soil parameters like cohesion, internal friction angle, unit weight, and slope geometry. The study evaluated slope stability under conditions such as free slope, slope with building loads under static and seismic conditions. The study found that sites with lower slope angles generally demonstrated greater stability, but there were cases where steeper slopes showed better stability due to superior shear strength values. Sites with higher cohesion values exhibited better stability in free slope analysis, while those with higher internal friction angles showed better stability under building loads of both static and seismic condition. To validate the above findings, a sensitivity analysis along with a comparative analysis between step-back and step-back setback building types were conducted. The results indicated that step-back setback buildings offered better stability compared to step-back buildings alone. This suggests that implementing step-back setback buildings could significantly improve slope stability in cities like Aizawl.

Slope failure is a prominent and recurring geohazard in numerous parts of Ethiopia, including Adama City, which is located in the Northern Main Ethiopian Rift (NMER). The city is surrounded by two ridges oriented in the NNE-SSW direction, which are susceptible to slope instability. Thus, this study is aimed at modeling slope stability along these two ridges using Finite Element Method (FEM) and Limit Equilibrium Method (LEM). The modeling was carried out on slopes of multifaceted geometry composed of eluvium soil, pumice, and moderately to highly-weathered ignimbrites. Critical slope sections were identified using satellite imagery and field manifestations such as slope toe condition and slope face tilting. Their geometries were then inferred from detailed geological cross-sections based on field data. Input parameters for the modeling, such as cohesion, friction angle, and elastic modulus, were calculated via Back Analysis using the Hoek-Brown criterion while unit weight and Poisson ratio were determined from empirical equations. For soil formations, the parameters were determined via standard laboratory experiments. The modeling was then carried out under different conditions, including dry, saturated, static, and dynamic conditions. Results from both LEM and FEM models revealed that three of the four analyzed slope segments were unstable under dynamic and saturated conditions, highlighting the influence and importance of precipitation and seismicity as triggering variables. Results from both methods tend to agree when the critical slip surface passes through a single geological material in both models. However, notable differences arise when the slip surface involves multiple geological materials. Under such conditions, LEM tends to yield higher FOS values compared to FEM. The results also showed that all unstable slopes were associated with the NNE-SSW striking fault of the study area, as inferred from failure surfaces generated from both models and field data. The study concluded that unstable slopes pose a serious risk to nearby residents and infrastructure, and as a remedy, it designed and recommended coupled benching and slope flattening.

The Ethiopian economy is primarily dependent on agriculture, making the construction of water harvesting facilities, such as dams, crucial for improving the productivity of this sector. The ongoing construction of the Gololcha dam on the Kurkura River located in Eastern Ethiopia aims to enhance irrigation schemes in the region. However, the dam site's complex geological and structural conditions pose challenges related to leakage and slope instability. Hence, this study focuses on addressing the abutment slope stability and leakage condition of this dam. This study employed kinematic analysis and the Limit Equilibrium Method (LEM) to assess slope stability. Additionally, engineering geological mapping, discontinuity surveys, seismic refraction tomography (SRT), and in-situ permeability testing were used to evaluate the leakage condition of the dam site. Notably, the permeability and SRT survey results identified potential leakage zones to the depth of 35, 30, and 35 m at the left, right, and central foundations of the dam, respectively. The kinematic method revealed one planar and two wedge modes of failure in the slope section covered by slightly weathered and fractured basalt rock at the right abutment. Further stability analysis of these two modes of failures via LEM analysis indicated slope instability under saturated conditions, emphasizing the role of pore water pressure. Furthermore, LEM modeling was directly utilized using the Slide 6.0 software to analyze the slope stability condition of the left abutment of the dam. This modeling also uncovered instability under saturated conditions. Based on the study findings, this study recommended curtain grouting to address potential leakage, as well as slope flattening and removing unstable rock wedges and loose material to stabilize unstable slope sections.

Highlights: A block limit equilibrium analysis method is proposed based on the respective advantages of block theory and three-dimensional rigid limit equilibrium method. This method perfectly explains the continuous transformation from double-plane sliding to single-plane sliding. The proposed method was successfully applied in the anti-slip stability analysis of a gravity dam foundation optimal design. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Ground Improvement is the property of Journal of Ground Improvement Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

We present a new computationally efficient methodology to estimate the probability of rainfall-induced slope failure based on mechanical probabilistic slope stability analyses coupled with a hydrogeological model of the upslope area. The model accounts for: (1) uncertainty of geotechnical and hydrogeological parameters; (2) rainfall precipitation recorded over a period of time; and (3) the effect of upslope topography. The methodology provides two key outputs: (1) time-varying conditional probability of slope failure; and (2) an estimate of the absolute frequency of slope failure over any time period of interest. The methodology consists of the following steps: first, characterising the uncertainty of the slope geomaterial strength parameters; second, performing limit equilibrium method stability analyses for the realisations of the geomaterial strength parameters required to calculate the slope probability of failure by a Monte Carlo Simulation. The stability analyses are performed for various phreatic surface heights. These phreatic surfaces are then matched to a phreatic surface time series obtained from the 1D Hillslope-Storage Boussinesq model run for the upslope area to generate Factor of Safety (FoS) time series. A time-varying conditional probability of failure and an absolute frequency of slope failure can then be estimated from these FoS time series. We demonstrate this methodology on a road slope cutting in Nepal where geotechnical tests are not readily conducted. We believe this methodology improves the reliability of slope safety estimates where site investigation is not possible. Also, the methodology enables practitioners to avoid making unrealistic assumptions on the hydrological input. Finally, we find that the time-varying failure probability shows marked variations over time as a result of the monsoon wet–dry weather. Highlights: Probabilistic slope stability analyses are coupled with a hydrogeological hillslope model to estimate the probability and frequency of rainfall-induced slope failure. The model accounts for the uncertainty about rainfall using a time-dependent method, and for uncertainty relative to the geomaterial properties. The model is tested on a road cut slope in Nepal (mountainous area subject to a monsoon season) finding that the cut slope will fail every other year. Time-varying failure probability shows marked variations over time as a result of the monsoon wet–dry weather. The findings indicate that it is important to use a time-dependent system to represent rainfall variability for slope failure probability analysis. [ABSTRACT FROM AUTHOR]

Copyright of Guangdong Architecture Civil Engineering is the property of Guangdong Architecture Civil Engineering Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

How to guarantee the stability of the cofferdam slope during and after construction is a difficult problem. In this article, a practical procedure is developed to implement probabilistic stability analysis for reinforced slope considering the spatial variability of soil strength. In the proposed procedure, the improved random limit equilibrium method is adopted to calculate the safety factor and particle swarm optimization is adopted to search critical sliding surface of slope. The influence of different reinforcement positions, lengths, and number of layers on the reliability of reinforced slope and critical sliding surface is studied. The results show the variability of soil, the length, location, and the number of layers of geosynthetics are important factors affecting probability of failure (Pf) of reinforced slope. The location and the number of layers of geosynthetic reinforcement play an important role in the statistical characteristics of FOS and slip mass volume. The reinforcement length has a greater impact on the safety factor. [ABSTRACT FROM AUTHOR]

Abstract The state of Espirito Santo is the most important producer and exporter of ornamental quarry stone. In its various quarries, it uses bench heights that range from 5, 20, 50 and 100 meters. The high altitudes raise concerns about the stability of the slopes. Therefore, the study focuses on determining the value of the safety factor (SF) for these heights using the limit equilibrium method. To make this possible, the values of simple uniaxial compression, Geological Strength Index (GSI), the disturbance factor, and intact rock parameter must be obtained. To obtain the GSI, it is necessary to establish a correlation with the Rock Mass Rating, the values of which are determined using a scan line. The uniaxial compression values were treated statistically, obtaining classes at 75, 100, 125, 150, 175, and 200 Mpa. The 2D slide software was used to obtain the SF values for the respective heights. With the results obtained, these rocks do not present stability problems. The correct choice of GSI is of paramount importance for a good analysis, as it directly affects the results. Using this technique to determine safety factors is appropriate, but it is necessary to analyze more robust methods to compare the results.

In this paper, a discussion on the applicability and limitations of the limit equilibrium method is presented. In this manner, the reliability of a concrete arch dam-foundation system under static loading is evaluated by considering a set of potentially moveable rock wedges in the foundation. The safety of the system is assessed utilizing a quasi-analytical method, which employs the limit equilibrium method and numerical analysis to calculate the sliding safety factors and the dam trust forces, respectively. The reliability is evaluated using the Latin Hypercube Sampling method. Random variables in the system are the friction angle, cohesion, and the Grout Curtain Efficiency Coefficient. In the end, the influence of two parametric variables of discontinuities, elastic slip and rock mass deformability modulus, on the rock wedges’ sliding safety factor is evaluated by comparing the results of the quasi-analytical method with the purely numerical method. The results show that in the case of complicated geotechnical conditions, the limit equilibrium method may not reflect real-world failure scenarios.

Ultra-high performance concrete (UHPC) is a durable and versatile construction material that enables the engineering of slender fabricated beams. Nonetheless, existing design methodologies exhibit certain discrepancies in predicting the ultimate shear capacity of UHPC beams. This study aimed to develop an improved predictive shear model based on design and mechanical properties. Eleven prestressed rectangular UHPC beams were subjected to shear tests, systematically investigating essential design parameters such as shear-span-to-depth ratio, stirrups ratio, longitudinal reinforcement ratio, prestressing force, and prestressing type. The results demonstrated that UHPC beams exhibit strain-hardening behavior after cracking, accompanied by the formation of dense diagonal cracks. Localized cracking eventually led to shear failure. The shear behavior was primarily influenced by the shear-span-to-depth ratio, showing an inverse relationship with shear strength. Increasing the longitudinal reinforcement ratio, stirrups ratio, and prestressing force marginally improved shear capacity. Furthermore, a limit equilibrium state-based method was proposed to develop a practical prediction formula that incorporates steel fibers and matrix interaction. The proposed method demonstrated superior accuracy compared to existing design models, displaying an average difference of 1.1% and a correlation coefficient of 0.96 with experimental results. [ABSTRACT FROM AUTHOR]

Copyright of Mining & Metallurgy (10057854) is the property of Beijing Research Institute of Mining & Metallurgy Technology Group and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Since the stability of slopes in infrastructures such as road and railroad embankments, excavations, and, in general, earthwork is important, analyzing the stability of these slopes has been one of the main focuses of geotechnical engineers. Although analyzing both reinforced and unreinforced slopes is needed, reinforced slopes require special attention as the reinforcement elements significantly affect the calculations. Hence, the current study's aim is to find out the differences between obtained safety factors using the Limit Equilibrium Method (LEM) and Shear Strength Reduction Method (SSRM). For this purpose, first, the origin differences in terms of Safety Factor (SF) are theoretically determined according to basic formulas for the aforementioned techniques. Then, to verify the formula, several numerical modelings are carried out using in situ measured geotechnical data to better understand the differences in terms of safety factors. The results indicate that for the reinforced slope with an SF value of higher than 1, the SSRM provides a higher SF in comparison with the other techniques, and the origin of this difference is the definitions of the SF in the different methods. [ABSTRACT FROM AUTHOR]

Different methods like limit equilibrium and soft computing-based methods are scattered in the literature for the prediction of the factor of safety (FoS) of slopes. However, selecting reliable models among them may be difficult for the users. Therefore in this study, we propose two different hybrid ANN models and perform the reliability analysis of the existing models and the proposed models using the historical datasets. The obtained datasets comprised the geotechnical properties of the soil and the slope geometric parameters. Subsequently, the ANN models were simulated, and the optimum ANN model was selected and then subjected to two stochastic optimization algorithms to improve its performance. Next, the performance of the ordinary and hybrid ANN models was compared using the empirical cumulative frequency distribution (CFD). Thereafter, 19 independent datasets outside those used in developing the models were used to validate the proposed models, the classical slope stability analysis models along with an existing ANN model. The validation was done using both the empirical CFD and mean absolute relative error (MARE). The results in all the validation cases favored hybrid ANNs. Then, the models were further subjected to rigorous statistical analysis by subjecting the models to the normality test, analysis of variance (ANOVA), variance homogeneity test, two-way t test, and nonparametric test. The output of all the tests conducted in this study revealed that the hybrid ANNs are most suitable for the slope stability analysis. [ABSTRACT FROM AUTHOR]

Ultra‐high performance concrete (UHPC) prefabricated beams are competitive in accelerated bridge construction. However, their broader application has been hindered by limited large‐scale tests and inaccurate design methods. To fill this gap, the authors conducted an experimental investigation on the shear and flexural performance of UHPC pi‐beams using two full‐scale specimens. One specimen was a precast UHPC beam, while the other was a composite beam with a normal concrete slab on the UHPC beam. The primary focus was on crack propagation, ultimate capacities, and failure modes. To complement the experimental findings, the extended finite element method (XFEM) was developed as a numerical approach. Nevertheless, relying solely on XFEM to understand real structural behavior is prone to misinterpretations. Moreover, the shear and flexural capacities were evaluated using existing codes and compared with the experimental results. The comparisons revealed that the predictions of shear capacities were at least 15% lower than the experimental values, whereas the flexural capacities showed acceptable agreement. To address this, the authors introduced the limit equilibrium method, leading to a more accurate prediction of shear capacity for UHPC beams with a deviation of <2%. [ABSTRACT FROM AUTHOR]

Stability assessments of block-flexural toppling failure using limit equilibrium methods are significantly affected by the assumption of a single overall failure surface, and the joint configuration and discontinuity persistence can affect the prior assumption of the overall failure surface used in limit equilibrium methods. In this study, a particle-based discrete element method (DEM) is used to assess the stability of rock slopes with the potential for toppling failure. The DEM is used to simulate block-flexural toppling failure based on an experimental tilting table. A validated numerical method is then developed to investigate the stability of block-flexural toppling failure-prone slopes. The results demonstrate that the calibrated DEM can successfully simulate the toppling failure of blocks prone to this failure mode. The presence of complex joint distributions in the model highlights that a single overall failure surface is not necessarily a reliable assumption in theoretical models of block-flexural toppling failure. In a slope with different cross-joint sets, two failure surfaces were observed. The results indicate that the spacing and friction angle of the main joint set and the joint configuration significantly influence the overall failure plane, slope deformation patterns and slope stability in block-flexural toppling failure-prone slopes. Furthermore, the identified stable, toppling and sliding regions in a slope undergoing block-flexural toppling failure were affected when the joint persistence was changed. Overall, this study highlights the assumption of a single failure surface used in the limit equilibrium method is not necessarily valid for block-flexural toppling failures. [ABSTRACT FROM AUTHOR]

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

The analysis of slope failure modes is essential for understanding slope stability. This study investigated the failure modes and triggering factors of a rock slope using the limit equilibrium method, finite differences method, and exploratory factor analysis. First, the limit equilibrium method was used to identify potential sliding surfaces. Then, the finite differences method was employed to study deformation and failure features in a slope. Stability factors were calculated considering specific conditions such as rainfall, prestressing loss, and earthquakes using the strength reduction method. Finally, exploratory factor analysis was utilized to identify the triggering factors of each failure mode. The results revealed that failure modes were categorized into two types based on the positions of the sliding surface. The main triggering factors for Failure Mode 1 were rainfall and prestress loss, while for Failure Mode 2 they were earthquake loading and prestress loss. This study offers a comprehensive exploration of potential failure modes and their triggering factors from mechanical and statistical perspectives, enriching our understanding of potential failure modes in rock slopes.

Earthquakes are one of the main causes of bedding slope instability, and scientifically and quantitively evaluating seismic stability is of great significance for preventing landslide disasters. This study aims to assess the bedding slope stability under seismic loading and the influences of various parameters on stability using a pseudo-dynamic method. Based on the limit equilibrium theory, a general solution for the dynamic safety factor of bedding slope is proposed. The effects of parameters such as slope height, slope angle, cohesion, internal friction angle, vibration time, shear wave velocity, seismic acceleration coefficient, and amplification factor on stability are discussed in detail. To evaluate the validity of the pseudo-dynamic solution, the safety factors are compared with those given by early cases, and the results show that the safety factors calculated by the present formulation coincide better with those of previous methods. Moreover, a two-dimensional numerical solution of bedding slope based on Mohr–Coulomb’s elastic–plastic failure criterion is also performed by using the finite element procedure, and the minimum safety factor is essentially consistent with the result of the pseudo-dynamic method. It is proved that the pseudo-dynamic method is effective for bedding slope stability analyses during earthquakes, and it can overcome the limitations of the pseudo-static method.