Stability Safety Coefficient Research Articles

Bank erosion under the impacts of fluvial erosion, frost heaving/freeze-thaw process of rivers in seasonal frozen regions

Bank erosion is a key feature of channel evolution in alluvial rivers, and will occur under the combined effect of hydraulic erosion and frost heave/freeze-thaw process of rivers in seasonal frozen regions. However, most research on bank erosion modeling has seldom considered the impact of the frost heave/freeze-thaw process. Therefore, the variation in the mechanical characteristics of riverbank soil under the freeze-thaw cycle was investigated firstly in the current research and then used in the modeling of bank erosion processes at typical sections of the Songhua River. Additionally, a sensitivity analysis of riverbank stability was conducted using orthogonal experiments. The results indicate that after 7 freeze-thaw cycles, the soil cohesion and internal friction angle of bank soil decreased by about 10%–47 % and 9%–19 %, respectively. Unlike lowland rivers, bank erosion of rivers in seasonal frozen regions is more likely to occur during the rising water period. The frost heaving/freeze-thaw process will make the bank stability safety coefficient Fs more quickly decrease to the unstable critical value. As compared with the case without considering the frost heaving/freeze-thaw process, the mass failure occurred in advance when the frost heaving/freeze-thaw process was considered, and the calculated bank erosion volume was increased by 11%–51 %, agreeing better with the measured value. The sensitivity ranking of the four influencing factors on riverbank stability under freezing-thawing conditions is as follows: river stage > groundwater level > cohesion > internal friction angle. The current study can provide a reference for research on bank erosion and channel evolution of rivers in seasonal frozen regions.

Effects of freeze–thaw on bank soil mechanical properties and bank stability

Riverbank instability in the seasonally frozen zone is primarily caused by freeze–thaw erosion. Using the triaxial freeze–thaw test on the bank of Shisifenzi Bend in the Yellow River section of Inner Mongolia, we investigated the changes in the mechanical properties of the soil at different freezing temperatures and freeze–thaw times, and analyzed the bank’s stability before and after freezing based on the finite element strength reduction method. The results showed that the elastic modulus, cohesion, internal friction angle and shear strength of the soil tended to decrease with the increase in the number of freeze–thaw cycles and the decrease in freezing temperature. After 10 freezing cycles at − 5 ℃, − 10 ℃, − 15 ℃ and − 20 ℃, the modulus of elasticity of soil decreased by 40.84 ~ 68.70%, the cohesion decreased by 41.96 ~ 56.66%, the shear strength decreased by 41.92 ~ 57.32%, respectively. Moreover, the stability safety coefficient of bank slope decreased by 18.58% after freeze–thaw, indicating that the freeze–thaw effect will significantly reduce the stability of bank slope, and the bank slope is more likely to be destabilized and damaged after freeze–thaw.

A Fast Prediction Method for Stability Safety and Reliability of Reservoir Bank Rock Slopes Based on Deformation Monitoring Data

The stability of reservoir bank slopes is critical to the engineering operation’s safety. Due to the complexity of geological conditions, the monitoring mode based on deformation monitoring data cannot directly respond to the structural damage stability state, whereas anther mode based on structural calculation is time-consuming and lacks real-time capabilities. To that end, this paper proposes a method for fast prediction of the safety state of reservoir bank rock slope based on the physical significance of time-dependent deformation and rock creep at monitoring points, with the safety coefficient and reliability obtained by numerical calculation as the dependent variables and the slope deformation monitoring sequence as the independent variable, based on full verification of the rationality of numerical calculation. The model can be used to forecast the stability and reliability coefficients of reservoir bank slopes online using deformation data from the field. The application verification of the left bank slope of the Dagangshan arch dam reveals that the average and maximum error of slope stability safety coefficient prediction is within 5% for 90 and 180 days and the average and maximum error of reliability index prediction is within 10%, which meet the engineering requirements and can provide a new way for rapid prediction of slope engineering safety.

Dynamic stability analysis and Experiment of the Mobile Elevating Work Platforms

In order to calculate dynamic stability of the Mobile Elevating Work Platforms (MEWP) during driving across obstacles and operating on the slope, the analysis method based on mathematical models and simulation models of the MEWP was put forward, then the MEWP dynamic simulation models where the tires and booms were set as flexible bodies were made by ADAMS. Four kinds of the most dangerous working conditions were analyzed, and then the dynamic curves of tire loads and dynamic stability safety coefficient were obtained. Next, the dynamic stability of the MEWP during operating on the slope was verified by field experiments, and the results show that the minimum dynamic stability safety coefficient is 0.157. By comparison and analysis of dynamic stability safety coefficient between simulation analysis and field experiment, it can be seen that the deviations are all positive and less than 5%, therefore the results show that the dynamic stability of the MEWP during driving across obstacles are satisfied. At the same time, the analysis method combining dynamic simulation and some field experiments of the MEWP is proved reliability, accuracy and economy. In all, the dynamic stability of the MEWP can be calculated accurately by ADAMS, in the meantime, the overload operation test (1.5 times rated load) must be performed on the 5° cross slope before the MEWP are selled, and so long as the minimum dynamic stability safety coefficient is no less than 0.1, the MEWP are proved stability and safety.

Slope stability analysis under rainfall conditions considering unsaturated characteristics of materials

As one of the important facilities in mines, the dump has become one of the major hidden dangers of mine safety management due to its large volume and loose structure. In this paper, based on unsaturated seepage theory of soil and practical engineering slope cases, the slope stability calculation model based on Bishop limit equilibrium method is established. This paper analyzes and calculates the evolution law of slope stability under extreme rainfall, obtains the law of slope stability safety coefficient changing with rainfall under unsaturated characteristics, and puts forward the corresponding countermeasures.

Stability Analysis and Application of Two-Stage Support on The High Fill Slope

This paper relies on the two-stage slope project, which is in Sanmenxia. The first grade slope is reinforced by soil nailing, multi-row piles and buttress retaining wall support scheme are adopted for the second stage subsequent fill slope, finite element simulation software is used, a numerical analysis model for multi-stage support slope is established, the development and change of soil nail axial force, pile axial force, pile shear force and bending moment as well as slope displacement and overall stability safety coefficient of multi-grade slope during layered construction process are simulated and analyzed. The results show that the horizontal load formed by the layered filling soil of the second grade slope makes the pile produce bending moment and shear force and the soil nail produce axial force. The vertical load formed by the filling soil makes the plastic area of the slope develop into the deep part of the soil, slip surface is formed around the soil nailing and multi-row pile supporting area, finally. It is proved that it is reasonable and feasible to adopt soil nail reinforcement and multi-row pile and supporting wall joint support scheme for multi-grade slope respectively, slope is stable as a whole.

Static stability behavior of aluminum alloy single-layer spherical latticed shell structure with Temcor joints

In recent years, aluminum alloy single-layer latticed shell has been extensively used in civil and industrial infrastructure. The elasticity modulus of aluminum alloy is low, the rigidity of aluminum joints are weak and the roof load transmission path is different. Therefore, the stability performance of this dome is unique. To clarify the stability performance of aluminum alloy single-layer latticed shell, over 500 aluminum alloy single-layer spherical latticed shells were analyzed with nonlinear finite method. The suggested values of rise/span ratio and initial imperfection were presented. The influencing coefficients of initial imperfection, material nonlinearity and stressed skin effect on stability bearing capacity were obtained. And the structural stability safety coefficient and the approximate calculation formula for stability bearing capacity of aluminum alloy single-layer spherical latticed shell were derived. The influences of joint semi-rigidity were investigated. All the aforementioned results provide a scientific basis for future stability design of aluminum alloy single-layer spherical latticed shell structure.

Study on design parameters of leaning-type arch bridges

Leaning-type arch bridge is a new spatial structural system composed of two vertical arches and two leaning arches. So far there has been no contrast analysis of leaning type arch bridge with different systems. This paper focus on a parametric study of leaning type arch bridge with different systems to find the influential rules on structural forces and stability and to provide some reference for practical designs. The parametric analysis is conducted with different rise-to-span ratios and bending rigidities of arch ribs by comparing internal forces. The internal forces decline obviously with the increase of the rise-to-span ratio. The bending moments at the centers of the main arches and the leaning arches are sensitive to the bending rigidities of arch ribs. Parametric studies are also carried out with different structural systems and leaning angles of the leaning arch by comparing the static stability. The lateral stiffness of leaning-type arch bridge is less than the in-plan stiffness. Compared with the leaning-type arch bridge without thrust, the leaning-type arch bridge with thrust has a lower stability safety coefficient. The stability safety coefficient rises gradually with the increase of inclining angle of the leaning arch. This study shows that the rise-to-span ratio, bending rigidities of arch ribs, structural system and leaning angles of the leaning arch are all critical design parameters. Therefore, these parameters in unreasonable range should be avoided.

Stability Analysis of Single-Pier Variable Cross-Section Box-Girder Continuous Bridge

On the basis of Umansky box-girder torsion theory, the software of ANSYS is applied to simulate related engineering model. In considering a variety of live load conditions, the lateral stability of multi-span single-pier variable cross-section box-girder under torsion eccentric load is analyzed. Analysis results reveal that under different working conditions, the factors affecting the transverse stability of the bridge and the proportion of the value on each, such as gravity, the span ratio and the distance between support are different; When the overload ratio is 2 times larger, the bridge stability safety coefficient decreases along the curve and changes rapidly. In the future design of this kind of bridge, the overall lateral stability should be paid much more attention. Some methods and suggestions about how to prevent the emergence of security and stability problems are put forward in the end.

Analysis on In-Plane and Out-Plane Instability Coupling of Steel Bowstring Arch Bridge with Box Section Single Rib

Steel single rib box section arch bridge is established on the basis of secondary development using parametric language of large-scale finite element software ANSYS. On the premise of same sectional area A of arch rib,height breadth ratio h/b is changed, and both the spatial instability mode under the condition of arch bridges dead weight and the stability safety coefficient under the condition of the first step instability mode is calculated. With the aim to optimize distribution of stiffness and stability of single rib arch bridge, the target is to find out a height breadth ratio h/b which can make in-plane and out-plane instability mode coupling, that is to say, equivalent stiffness of in-plane and out-plane of the mode.

The Numerical Analysis of Stability against Upheaval of Foundation Pit

Great region discrepancy exists in natural soil, while analysis and calculation of stability against upheaval of foundation pit in current specifications is only to soft soil. In order to study the stability against upheaval of foundation pit bottom in different geological conditions, FLAC3D numerical analyzing software is adopted to calculate and visualize the influence that several factors cause to stability safety coefficient, and contrast and checking is also made with current analysis and calculation methods and normal formula of stability against upheaval of excavation. The study shows that : a increase in soil’s cohesion,internal frication angle and embedded depth can develop the stability against upheaval of foundation pit.

Deformation and Stability Analysis of Large Slope Based on ADINA Software

Slope failure is a kind of serious geologic disaster. This paper based on the detailed geology survey and analysis, judged the failure mode of the Pipayuan slope; Using ADINA which is professional finite element software, made mechanic calculation of slope, analyzed the stress condition and discussed the change of stress. According to the Strength Reduction Method, the slope stability safety coefficient was calculated. Results show that: the whole slope, may be slide along the soft interlayer, especially in the case in the event of heavy rainThe effectiveness is verified by the finite element calculation of slope with anti-slide pile reinforcement.

Stability Analysis of Concrete Gravity Dam Foundation Based on Catastrophe Model of Plastic Strain Energy

A catastrophe model of plastic strain energy based on strength reduction factor was established. Then the model was applied to the sliding stability analysis of a concrete gravity dam. The results show that the catastrophe model of plastic strain energy can solve the issue of the dam stability analysis well. And the result of the catastrophe model is more accurate than that of the displacement catastrophe criterion based on displacement curves. The strength reduction is used to analyze the anti-sliding stability safety of a concrete gravity dam with the water depth of 100m upstream and 0m downstream. By catastrophic model of plastic strain energy, anti-sliding stability safety coefficient of this dam can be accurately determined to be 1.4.

The Seismic Stability Numerical Analysis of Embankment High Slope with Different Filling

In recent years, frequent earthquakes had happenned everywhere in the world.Through establishing soil dynamic constitutive model and boundary conditions, implement finite element numerical analysis of embankment high slope of different filling, using large geotechnical software GEO–SLOPE, inputting El Centro wave, Taft wave and artificially wave according to requirements specification fitting respectively in this article.Results show that different degree earthquake will reduce the stability safety coefficient of embankment slope, the properties of embankment high slope of different filling is worse,the range of reduction is larger.

Laser application in the current profile control and pressure distribution in tokamaks and stellarators

Physical grounds are discussed for the laser control of the current and plasma pressure distribution profiles. The mechanism of generation is discussed of a noninductive current drive under laser irradiation of a frozen-hydrogen pellet from the plasma volume; a possibility of arrangement of the peaked profiles of the current is shown; the estimates of the bootstrap current are made. It is noted that by using the laser methods, one can excite, among the others, the local currents with the reverse charge motion in respect to the initial ohmic current. One can, thus, provide the optimal current distributions, from the viewpoint of the magnetic plasma confinement, and hence, the profiles of the stability safety coefficient, and the value and sign of `shear'). The pressure (density) distribution is controlled by a time-programmed laser pulse irradiation of a moving pellet.