Results Of Stability Calculations Research Articles

Inclusion of Nature-Based Solution in the Evaluation of Slope Stability in Large Areas

In areas affected by mining, which are undergoing reclamation, their geotechnical characteristics need to be monitored and the level of landslide risk should be assessed. This risk should preferably be reduced by nature-based solutions. This paper presents a KurZeS slope stability assessment technique based on areal data. This method is suitable for large areas. In addition, a procedure is presented for how to incorporate a prediction of the impact of nature-based solutions into this method, using the example of vegetation root reinforcement. The paper verifies the KurZeS method by comparing its results with the results of stability calculations by GEO5 software (version 5.2023.52.0) and validates the method by comparing its results with a map of closed areas in the area of the former open-cast mine Lohsa II in Lusatia, Germany. The original feature of the KurZeS method is the use of a pre-computed database. It allows the use of an original geometrical and geotechnical concept, where slope stability at each Test Point is evaluated not just along the fall line but also along different directions. This concept takes into account more slopes and assigns the Test Point the lowest safety factor in its vicinity. This could be important, especially in soil dumps with rugged terrain.

Stability of cylindrical anisotropic composite shells under torsion in a three-dimensional formulation

The article presents a calculation of the stability of non-thin cylindrical anisotropic layered shells under the action of end torsional moments in a spatial formulation. The anisotropy of the used material is characterized by one plane of elastic symmetry of characteristics. This is caused by the mismatch between the main elastic directions of the composite fibrous orthotropic material and the axes of the curvilinear cylindrical coordinate system.
 A three-dimensional inhomogeneous system of partial differential equations describing the subcritical stress-strain state within the linear theory of elasticity is derived using the Hu-Washizu variational principle. Reducing the dimension of the problem under consideration from three-dimensional to one-dimensional is carried out by taking into account the axial symmetry of the deformation of the cylindrical shell and using the method of straight lines along the generatrix.
 Based on the modified Hu-Washizu variational principle, a three-dimensional system of homogeneous partial differential stability equations is derived within the framework of the spatial theory of elasticity. The reduction of a three-dimensional system to a one-dimensional one is carried out along the generatrix and in the circular direction - by expanding the components of stresses and displacements into double trigonometric series when applying the procedure of the Bubnov-Galorkin method, as well as taking into account the periodicity of the resolving functions.
 An algorithm has been developed, implemented in the form of application software packages for PCs. In it, in a single computational process using the numerical method of discrete orthogonalization in the direction normal to the middle surface of the shell, the establishment of the parameters of the subcritical stress-strain state and the solution on this basis of stability problems for non-thin anisotropic cylindrical shells under the influence of torsion are combined.
 The problem of the influence on the stability of an anisotropic cylindrical non-thin shell of an increase in the number of cross-reinforced layers depending on the angle of rotation of the main directions of elasticity of the material and the direction of application of torque is considered. The obtained results of stability calculations according to the proposed approach were compared with critical torsion loads calculated using an orthotropic model for calculating anisotropic shells. It is shown that for single-layer cylindrical shells the difference between the compared results reaches 69%. An increase in the number of cross-reinforced layers leads to a decrease in this discrepancy, and with seven to eight layers, the difference between the critical loads obtained using the described approach and the orthotropic model is within 5%. This result is consistent with those obtained using classical or refined theories of calculations of both thin and non-thin anisotropic cylindrical shells.

Application of Grey Lotka-Volterra Model in Water-Economy-Industry-Technology Innovation System in Beijing-Tianjin-Hebei Region.

With the proposal of China’s high-quality development strategy, how to promote regional stability and coordinated development based on a deep understanding of the main contradictions and changes in China’s society has become the focus of research. High-quality development is a brand-new coordinated development concept, which aims to optimize the economic structure, transform the development model, enhance the development momentum, and take innovation as the primary driving force. How to promote the coordinated development of this region has become a hot issue considered by scholars. The Beijing-Tianjin-Hebei region is the capital economic circle of China, and the purpose of this study is to promote the coordinated and stable development of the region. On this premise, this paper firstly adopts the composite Grey Lotka-Volterra (GLV) model and Fractional GM(1,1) (FGM(1,1)) model to research Water Resources system-Economic System-Industrial System-Technology Innovation System in the Beijing-Tianjin-Hebei region. Secondly, by analyzing the research data, it is found that the relationship between the system is very complex, and the stability calculation results are all below 0. Then, the analysis of the research results shows that there is no obvious coordination among the three regions, and they have not yet reached a state of mutual promotion and stable and coordinated development. Finally, four suggestions are put forward for the coordinated development of the Beijing-Tianjin-Hebei region. This can not only provide direction for the future development of the region but also have reference significance for the development of other regions. Further, accelerate the coordination and unity of all factors of production in China and promote China’s development at a deeper and higher level.

Application of the Nailing Technique to Stabilize a Slope in a Section of the Twinning of Road and Rail Infrastructure

Nailing is one of the most widely used stabilization techniques because of its technical and economic advantages. It is a practical and effective solution for the reinforcement of in-place slopes. It consists of placing in the soil high resistance nails to increase the cohesion of the soil and its resistance to traction and shear, which allows having a new material of great capacity. In this paper, we present the slope stability study in a section twinning of the road and railroad infrastructures between the kilometer points (KP) 105+938 and 106+263 of the line connecting Casablanca to Marrakech. The railroad track's topographic constraints and geometric requirements made the nailing method appeal to the realization of the new railroad in this area. The objective of this work is, on the one hand, to present the stability analysis of the slope before the earthwork and the implementation of the new railroad and, on the other hand, to evaluate the performance and stability of the nailed walls. The stability analysis of the soils in this section was verified in terms of safety coefficient using the calculation software TALREN. In the end, it can be concluded that the stability calculation results are conclusive and allow for highlighting the effectiveness of the innovative solution of nailing. This technique can be considered a good alternative to improve the safety and performance of excavation walls.

The formation and failure process of Yigong landslide in Tibet Plateau

Yigong landslide is located in Zhamunong gully, Yigong Township, Bomi County, Linzhi region in Tibet, the volume of which is 3×108m3. Firstly, we analyse the formation mechanism of Yigong landslide in 2000, based on the field investigation and data collection. Secondly, we analyse the failure mechanism of Yigong landslide in 2000, combined with the mechanical test results of granite rock and stability calculation results of slumped mass (BH01). Under the combined effect of rapid incision and seismic activity in Yigong Lake zone, the basic factor of landslide formation is that the rock mass structure for controlled slope rock mass evolution has entered a stage of progressive failure in Zhamunong gully, and precipitating factors of landslide are excess melt-water and continuous rainfall under the temperature rise before landslide hazard happens, according to the results of the study. The formation process of landslide can be divided into 4 stages. (i) Trailing edge fracture of slope rock mass is in rapid development stage due to the effect of fast incision in the valley. (ii) The frequent seismic activities in Yigong Lake district facilitate the development and evolution of granite rock mass’s structural plane; (iii) The combined effect of excess melt-water and continuous rainfall at the prophase of the disaster makes the high angle fissure in trailing edge of BH01 rock fall body further develop. (iv) The high-speed rock fall block of BH01 rock fall body triggers the liquefaction of detrital accumulation materials at the source of gully, which forms landslide and finally transforms into high-speed granular mass flows. The stability-losing distruction mechanism of landslide is as follows. Under the combined effect of many conditions, such as fast incision of valley in Yigong district, earthquakes, temperature change, and continuous rainfall and so on, the high angle fissure in trailing edge of BH01 rock fall body develops quickly, and continuous creeping deformation occurs in rock fall body along weak structural plane or fracture surface, forming mid ‘locking section’. When the depth of cracking segment in trailing edge of BH01 rock fall body Hcr >363m or the length of rock mass’s locking section L<455m, sudden brittle failure occurs in the mid locking section of BH01 rock fall body, and rock fall occurs in rock fall body.

Исследования устойчивости монолитных и слоистых пластин при сжатии

The results of calculations of the stability of monolithic and layered plates, obtained by analytical and numerical methods, are presented, which are compared with experimental data. The obtained results of stability calculations are within the limits of the permissible error. The results of numerical calculations of stability by the finite element method in the ANSYS program turned out to be higher than the values ​​determined by the Euler formula and lower than the results obtained by the formula for calculating the stability of plates. To study the bearing capacity of layered samples under compression, an assessment of their stability was carried out with different numbers and arrangement of layers of alloy and composite material. The optimal layouts of layers in the material for designing a composite panel have been determined. The results were used to design a composite wing panel based on sheets and profiles made of high-strength aluminum-lithium alloy and laminated aluminum-fiberglass. Stability of the composite panel under compression were 7% higher than the experimental values due to the local loss of stability of its elements, which precedes the general loss of stability and reduces the value of the critical load.

Precise evaluation method for the stability analysis of multi-scale slopes

Slope stability analysis is a multi-scale problem. Typically, owing to the distinctions of slope scales (e.g., slope height or slope angle) in practical engineering, the stability calculation results of slopes with various scales from numerical methods inevitably exhibit different computational precision levels in the case of identical computational grids, and therefore the stability results of different slopes cannot be compared. To achieve equal accuracy stability analysis for multi-scale slopes, this study establishes numerical models of slopes with various scales as well as different grid shapes and sizes to conduct stability analysis. The results show the following: (a) a positive correlation relationship exists between the safety factor of the slope and the scaling factor, which is defined as the ratio of the grid size to the slope height; (b) the definition of the refined safety factor is given, representing the safety factor that corresponds to the infinitesimal grid size and eliminating the computational error of slope stability analysis caused by grid size or shape; (c) on this basis, embarking on the composite influence of multiple scales of slope on stability analysis, the study proposes a simplified treatment method suitable for evaluating the refined safety factor of the multi-scale slopes, which is verified as valid and feasible by some examples.

Overall stability of steel web-tapered frame members

The solution to the problem of fully nonlinear stability analysis of web-tapered I-shaped members is presented in the paper. In order to accelerate the analysis, an analytical- numerical approach was applied in the solution. Nonlinear stability analysis in the elastic range is carried out by the use of the analytical procedure (so-called “Member” procedure) which is based on the combination of the results of buckling and linear analyses. The growth of the plastic deformations is taken into account by adding extra displacements in the “Member” procedure. These displacements are determined numerically in the process of incremental loading (so-called “Section” procedure). The proposed approach allows the calculation of all displacements at each load step and the estimating of the member’s overall stability capacity, rapidly (up to 20 times faster than using shell-FEM) and accurately enough. The overall stability calculation results, depending on the different variables (slenderness, load eccentricities and their ratios, rigidity variations) under different load cases, are given in the paper. The stability capacity comparison between tapered and prismatic members is presented. Also the comparison with existent experimental researches’ results is provided in the paper.

Rainfall thresholds for the occurrence of shallow landslides determined for slopes in the Nowy Wiśnicz Foothills (Polish Flysch Carpathians)

Values of rainfall thresholds on selected shallow landslide slopes (Dzial, Gwoździec) located in the Nowy Wiśnicz Foothills are determined using a physically-based slope stability model considering a long-term period of analysis (GeoSlope Inc. software). Slope stability analysis included determination of the impact of rainfall on changes of stress state within the soil substrate and their influence on estimation of mass movement risk. The slope stability calculation results have shown that the rainfall threshold values are a function of many variables, primarily the hydraulic properties of soil and rock substratum, temporal distribution of precipitation, and soil moisture content conditions in the period proceeding rainfall. The results of the calculations indicate that, in extreme cases, accumulated rainfall threshold values for the same slope can range from ~100 to 500 mm. Estimated rainfall threshold values were lower than those values reported in the literature for the Polish Carpathians, but are similar to those determined by Guzetti et al. (2007) for Central and Southern Europe.

A time-spectral approximate Jacobian based linearized compressible Navier-Stokes solver for high-speed boundary-layer receptivity and stability

A numerical method for conducting linear receptivity and stability investigations of high-speed wall-bounded flows based on the linearized compressible Navier-Stokes equations is presented. The current approach is directly applicable for stability investigations of arbitrarily complex geometries. The left-hand-side operator for the linear system of equations is obtained by computing numerical right-hand-side Jacobians while the right-hand-side is build from exact flux Jacobians. Utilizing the numerical right-hand-side Jacobian approach avoids lengthy, error prone derivation of the stability equations in the context of generalized curvilinear coordinates. The governing equations are solved using either time-stepping or time-spectral discretizations. Three different time-spectral approaches, i.e., direct inversion, unfactored and factored schemes, are presented and their numerical characteristics for the solution of the linearized Navier-Stokes equations for linear receptivity and stability analysis for large-scale transition problems are explored. Linear receptivity and stability calculation results are provided for different solver options. Performance comparison of the three schemes are presented for a wide range of test cases: An incompressible cross-flow for a swept flat plate boundary layer, a supersonic shock-boundary-layer interaction, hypersonic boundary layers on a flat plate and a flared cone, and, finally, for the receptivity of a hypersonic boundary layer for a right sharp cone.

THE ANALYSIS OF THE STABILITY OF THE COMMUNICATION SUPPORT STABILIZED BY GABION WALL WITH VARIABLE CONFIGURATION

The subject of the article concerns the stabilization of communication earthworks using the so-called lightweight retaining structures. The stability of the embankment with the embankment built with the gabion wall is analysed, assuming a uniformly distributed load on the crown and a case of unilateral water pressure in the event of a flood. Final results of stability calculations made with the Fellenius and Bishop method in the form of slip surface with the smallest value of the coefficient were presented. Then, assuming the case of damming up of flood water, discretization of the filtration area, velocity distribution and hydrodynamic grating and slip surfaces were developed. The variable parameter is the wall configuration.

07.30: Ways of improving the stability design calculations of cold‐formed columns

ABSTRACTThe article presents the theoretical basis of engineering approach to the stability resistance calculation of cold‐formed columns subjected to an axial or eccentric compression. The research is based on an analytical stability solution and Eurocode provisions in terms of determining the reduced cross‐section in a combined action loading. It is demonstrated, that the reduced cross‐section, defined by the limit state of the column without reduction, in most cases has sufficient accuracy for engineering practice. Taking this assumption into account the engineering algorithm is designed for stability calculations by: flexural mode relatively the major axis; flexural‐torsional mode relatively the minor axis and overall mode. The results of stability calculations are demonstrated on examples of pin‐pin end restrained cold‐formed columns with high degree of section reduction. Stability resistance coefficients depending on column slenderness and load eccentricities are given. The degree of reduction influence on the overall stability is highlighted. The comparison with Eurocode results and authors experimental studies is also given.

Shear strength of clayey soils from the vicinity of Gorlice and Ciężkowice

Abstract The work presents results of maximum and residual strength tests of six clayey soils from the landslide areas near Gorlice and Ciężkowice. The tests were carried out in a direct shear apparatus on samples of dimensions 60 × 60 mm that were sheared at least three times. A shearing strain rate was equal 0.1 mm·min–1, and the range of horizontal deformation of the samples was equal 20%. The results of the tests revealed that multiple shearing of the soil caused a significant decrease of its shear strength, resulting in significant changes in cohesion, and the smaller changes in the angle of internal friction. It was shown that the three-time shearing reduced the initial shear strength of about 50%, and further three series of shearing decreased it approximately 15% more. The study also showed that by using a Coulomb-Mohr shear strength linear equation, the analyzed soils had a little residual cohesion. Therefore, to describe the characteristics of the residual strength, there were used two non-linear equations proposed by Mesri and Shanien (2003) and Lade (2010), which led to the same results. It was also shown that the use of non-linear characteristics of the residual strength at low values of the normal stresses gave more unfavourable results of stability calculations in relation to the method based on the linear strength characteristic taking into consideration the presence of the residual cohesion.

From Discrete to Continuum Models of Three-Dimensional Deformations in Epithelial Sheets

Epithelial tissue, in which cells adhere tightly to each other and to the underlying substrate, is one of the four major tissue types in adult organisms. In embryos, epithelial sheets serve as versatile substrates during the formation of developing organs. Some aspects of epithelial morphogenesis can be adequately described using vertex models, in which the two-dimensional arrangement of epithelial cells is approximated by a polygonal lattice with an energy that has contributions reflecting the properties of individual cells and their interactions. Previous studies with such models have largely focused on dynamics confined to two spatial dimensions and analyzed them numerically. We show how these models can be extended to account for three-dimensional deformations and studied analytically. Starting from the extended model, we derive a continuum plate description of cell sheets, in which the effective tissue properties, such as bending rigidity, are related explicitly to the parameters of the vertex model. To derive the continuum plate model, we duly take into account a microscopic shift between the two sublattices of the hexagonal network, which has been ignored in previous work. As an application of the continuum model, we analyze tissue buckling by a line tension applied along a circular contour, a simplified set-up relevant to several situations in the developmental contexts. The buckling thresholds predicted by the continuum description are in good agreement with the results of stability calculations based on the vertex model. Our results establish a direct connection between discrete and continuum descriptions of cell sheets and can be used to probe a wide range of morphogenetic processes in epithelial tissues.

Buckling stability of multilayer plates and shells with interfacial structural defects under axial compression

Based on the discrete-structural theory of thin plates and shells, a variant of the equations of buckling stability, containing a parameter of critical loading, is put forward for the thin-walled elements of a layered structure with a weakened interfacial contact. It is assumed that the transverse shear and compression stresses are equal on the interfaces. Elastic slippage is allowed over the interfaces between adjacent layers. The stability equations include the components of geometrically nonlinear moment subcritical buckling conditions for the compressed thin-walled elements. The buckling of two-layer transversely isotropic plates and cylinders under axial compression is investigated numerically and experimentally. It is found that variations in the kinematic and static contact conditions on the interfaces of layered thin-walled structural members greatly affect the magnitude of critical stresses. In solving test problems, a comparative analysis of the results of stability calculations for anisotropic plates and shells is performed with account of both perfect and weakened contacts between adjacent layers. It is found that the model variant suggested adequately reflects the behavior of layered thin-walled structural elements in calculating their buckling stability.

Determination Of The Stability Parameters And The Position Of A ShipIn The Condition Of Flooding Of The Watertight Compartment

This paper presents the results of stability calculations in the case of damaged watertight compartment during flooding. Working out these calculations there have been applied the constant displacement method and the method of established volume. The work has contributed to the analysis of changes of metacentric height, angles of heel and angles of trim, which may occur during flooding of the watertight compartment. The method of determination of the position of a ship during the flooding of the watertight compartment and computer programmes elaborated might be exercised on training stability and survivability simulator which is being prepared to be executed at The Naval University of Gdynia. These calculations might be of some help in training midshipmen and functional persons who are responsible for safety of floating.

Judder analysis of electronically controlled limited slip differential

The electronically controlled limited slip differential system used on the new Skyline contributes to improvements in vehicle dynamics. One important performance parameter that is improved is the start-off acceleration when one drive wheel is on an ultra-low friction surface. There was concern, however, that larger LSD torque might cause drivetrain judder due to the negative μ-v slope of the wet multiplate clutch used in the system. An analysis based on natural mode calculations clarified the mechanism generating judder, and the results of stability calculations revealed measures for improvements. As a result, the problem of self-excited vibration was resolved.

Combustion zone - Acoustic cavity interactions in rocket combustors

Analytical and numerical models are employed to assess the stabilizing impact of acoustic absorbers on liquid propellant rocket engine intrinsic stability. The tuning and stability behavior of cavities in which two-dimensional flow and temperature variations exist are predicted through the application of an iterative-integral, Green's function method of analysis. Results of stability calculations performed for a variety of cavity geometries and temperature gradients indicate that adding a large open area absorber to a combustion chamber significantly alters the spatial shape of the oscillation. This alteration consequently affects the driving and damping mechanisms in the chamber. Because of this interaction, the maximal stabilizing effect of a cavity with a given open area does not in general occur for a design tuned in the acoustic sense to the frequency of the oscillation, but rather for a design that is not tuned but which tends to maximize the influence of the damping mechanisms in the chamber relative to the driving mechanisms. Additionally, absorbers with large backing cavities are shown to perform better over a wider range of operating conditions than absorbers with small backing cavities. Calculations also reveal that large temperature gradients in an absorber tend to reduce its broadband effectiveness.

The possible role of meridional flows in suppressing magnetic buoyancy

The equation of motion for a toroidal flux ring in a stellar convective envelope is derived, and the equilibrium of such a ring is considered. Necessary conditions for the stability of toroidal flux rings are derived, and results of stability calculations for a particular model of the meridional flow are presented. The motions of the flux rings when the rings are far from their equilibrium position or when equilibrium does not exist are considered. The results confirm the linear stability analysis, and show that in the absence of stable equilibrium, the rings move toward the solar surface along a trajectory which is parallel to the rotation axis. It is expected that viscosity will tend to reduce the rotational velocity difference between the flux ring and its surroundings, thus reducing the Coriolis force and altering the equilibrium. The storage time of toroidal flux rings is estimated, and some implications for the sun are discussed.

Critical Period for Stability of an Excavated Slope in Clay Soil

Bishop and Bjerrum have hypothesized that the critical period for stability of a slope excavated in weak clay soil would not occur at the end of the excavation period but, rather, would occur some time after completion of the excavation when the pore-water pressures in the slope corresponded to natural seepage conditions; for natural seepage conditions the pore-water pressures would no longer be influenced by the effects of stress changes in the soil caused by excavation of the slope. Evidence in support of this hypothesis will be presented in the form of a stability study of an excavated slope along the Kimola Canal in Finland. It will be shown from the results of stability calculations, based on measured pore-water pressures, that the safety factor of the slope decreased immediately after excavation was completed and that the slope failed some time later when the water-pressure conditions were most adverse to stability.