Stability Evaluation Method Research Articles

On dynamic stability evaluation methods for long combination vehicles

The dynamic stability of long combination vehicles (LCVs) is an important part of vehicle safety. An LCV, its driver and the road constitute a unique closed-loop dynamic system. Assessing the dynamic stability is difficult due to the complex interactions of driver-tractor-trailers-road. Rearward amplification (RA) is an effective performance measure of the dynamic stability; various methods are applied for evaluating the RA. However, the measures from different methods may differ significantly. What are the root causes for the disparity of evaluation results? This paper tackles the problem by investigating the typical methods for evaluating the measure of two LCVs, i.e. an A-train double and a B-train double. To this end, simulations of the LCVs are conducted using TruckSim software. The study discloses the main causes for the disparity of the measures from different methods, and recommends the effective approaches to the assessment of the RA.

Unsaturated 3D Column Method: New Method for Evaluation of Stability of Unsaturated Slopes Subjected to Vertical Steady-State Infiltration and Evaporation

Abstract A new analytical method for investigating the stability of unsaturated soil slopes was developed by considering a 3D failure wedge under different steady-state infiltration and evaporation...

Stability evaluation method for assessing bedrock and overburden layer slope (BOLS) under seismic load

Seismic load is a type of dynamic load that can easily induce the failure of the foundation slope. Using the continuum-based discrete element method in continuum mechanics, herein, the rupture degree and permanent displacement are defined and their evaluation steps are proposed. The sensitivity of rupture degree and the permanent displacement of overburden under seismic force are also analyzed. A new stability evaluation method for an overburden layer under seismic load, which considers rupture degree and permanent displacement, is established. The results showed that the overburden layer and the interface between bedrock and overburden are damaged to a certain extent under the action of a small-intensity earthquake (a peak = 0.03–0.06 g), although the overburden surface is not damaged. With the increase of seismic frequency and slope height, the permanent displacement of overburden decreases, although it increases with the increase of peak acceleration and slope angle. Furthermore, duration has little to no influence on the permanent displacement of the overburden under the condition of a small or moderate earthquake. In the case of a large earthquake, the permanent displacement of overburden increases linearly with the increase in duration.

Rock Slope Stability Analysis Based on Comprehensive Failure Mechanism and Engineering Application

The sliding modes of rock slopes are closely related to the strength yield criterion of the rock mass adopted in numerical analysis. In order to make theoretical calculation results meet engineering practice, particularly for complex rock slopes with multiple empty surfaces, multiple control sliding surfaces and potential sliding modes, numerical analysis method used for stability evaluation should take comprehensive failure of the rock mass into consideration. This paper proposes a stability evaluation method based on a comprehensive failure mechanism of the rock mass based on discrete element theory and a modified M-C strength yield criterion to overcome the shortcomings of traditional strength yield criteria, which are mainly derived from shear strength failure. However, the method is used to analyze deformation and failure modes of a typical rock slope in Shuang Jiang Kou Hydropower Station. The results of the findings demonstrated that the method mentioned above can describe different failure modes of rock blocks and joints, deformation trend and stable state of the slope. The experimental results are approved by geological exploring. To adapt to the yield modes of the rock block and joint, a space support system with variable angles, lengths, and design forces is chosen for this typical rock slope. This support system has been proven to be practical and can improve the stability coefficient of the slope. The results presented in this study are useful in engineering practice.

재생에너지 발전출력의 변동성을 고려한 정적안정도의 위험도(Risk) 평가 방법에 관한 연구

In this paper, a probabilistic static stability evaluation method considering the variability of renewable energy generation output and a Well-Being Analysis (WBA) method that can evaluate the level of risk of static stability are presented. In order to apply the WBA, we analyzed the measured renewable energy generation output and variability. In addition, to prove the effectiveness of the proposed WBA method, a probabilistic stability evaluation was performed using a test system and the WBA method was applied.

Application of Multi Body System Coupling Dynamic Model in Posture Stability Evaluation of Sports

Due to the lack of more precise and complete data support, the reliability of posture stability evaluation method based on common technology is poor. In the face of such problems, the application of multi-body system coupling dynamic model in the evaluation of sports posture stability is proposed. The coupling dynamic model of human motion posture is established, and the relevant data of human motion posture is collected. The complete data of human motion posture is obtained by solving the dynamic model. Choose the appropriate stability evaluation index, calculate the stability evaluation index, divide the stability level, and realize the evaluation of posture stability. The experimental results show that: the application of multi-body system coupling dynamic model in the stability evaluation method makes the time delay and data error of the evaluation method small, and its overall reliability is improved.

Research on the stability evaluation method of anchored slopes based on group decision making and matter element analysis

This research is focused on the evaluation method of anchored slope stability, and an accurate evaluation method with a simple operation is proposed. Group decision theory and the analytic hierarchy process are used to determine the weight of each evaluation element, the correlation degree of each indicator is determined based on matter element analysis theory, and inverse hierarchical calculations are performed based on the obtained weight value and correlation degree to finally obtain the criteria layer correlation degree used for stability evaluation. The results show the following: (1) the evaluation method better integrates the effects of multiple factors on the stability of the anchored slope, and the evaluation results are accurate and consistent with the actual situation of the project; (2) the evaluation method can make full use of the experience of the expert group and effectively avoid the evaluation error caused by the subjective deviation of a single expert; (3) the group decision theory-entropy model was introduced to realize the quantitative evaluation of the reliability of expert scoring and effectively improve the efficiency of expert discussion; and (4) the evaluation result is intuitive, and the correlation degree obtained can not only reflect the stability grade of the anchored slope but also reflect the "distance" between the anchored slope and other stability grades.

On-Site Monitoring for the Stability Evaluation of a Highway Tunnel above Goaves of Multi-Layer Coal Seams

This paper presents the on-site monitoring of a medium–long highway tunnel constructed above a goaf of a multi-layer coal seam, in order to evaluate and maintain safety during operation. The case study of the Tianzimiao medium–long highway tunnel in Shanxi province was conducted above a goaf of a multi-layer coal seam with typical geological and engineering conditions in China, where a total of four coal seams (seam no. 3, 8, 12, and 15) were mined out with a total thickness of up to 11 m. Methods including data collection, engineering geological survey, drilling, geophysical prospecting, testing, and on-site monitoring were adopted, and a geo-mechanical model was established to conduct the research. Stratified monitoring was applied to investigate the individual settlement and deformation of the four layers of the goaf below, and a prediction of the possible deformation in tunnel floor ground was made based on the stratified measurements. The settlement of the tunnel sidewall, the internal stress in the fractured zone of the surrounding rock, and the deformation above the tunnel entrance were also monitored, and the monitoring data were compared with the numerical simulation results for the safety evaluation of the tunnel. The results show that the current tunnel deformation values and trend are both within the safety scope of the evaluation and prediction. The stability evaluation method for the multi-layer goaf used in this paper and the long-term on-site monitoring and timely feedback during operation is helpful to ensure the safe use of the tunnels above the goaves of multi-layer thick coal seams.

Evaluation Method of Complex Slope Stability in Construction Industry Based on Correlation Calculation

Based on the basic-element expression method and correlation function theory in Extenics, combined with the knowledge of slope engineering, a method for evaluating the stability of complex slope is proposed. The evaluation process includes the selection of suitable evaluation indexes of slope stability, identificationof the classification standard for the slope stability, identificationof the weights of evaluation indexes by using the improved analytic hierarchy process,identificationof the classical domain, node domain and matter-element under evaluation,the calculation of the correlation of each stability class for each evaluation index, normalization of correlation,and so on. The selection rule of the slop stability evaluation indexes and selection of correlation function and optimal points are also discussed, which can provide reference for slope engineering designin construction industry.

Evaluation and Application of Surrounding Rock Stability Based on the Improved Weighting Multidimensional Cloud Model

Aiming at the uncertainty in the existing tunnel surrounding rock stability evaluation methods and the inability to make scientific explanations in the process of determining the weights of multiple evaluation indicators, this paper combines subjective weighting based on the nonlinear characteristics of the surrounding rock stability evaluation criteria. Based on the advantages of the method AHP and the objective weighting method CRITIC, a comprehensive weighting method with multiple evaluation indicators is proposed, which is integrated with the multidimensional normal cloud model to establish a surrounding rock stability evaluation method for the improved weighted multidimensional cloud model and accurately obtain the safety level of tunnel surrounding rock construction. The multidimensional cloud model based on improved weighting not only solves the two major problems of randomness and ambiguity in surrounding rock stability evaluation but also fully considers the influence of the information contained in each evaluation factor on the results. The surrounding rock stability evaluation method in this paper is applied to the tunnel construction of the Beijing-Shanghai Expressway and Jinan Expressway connecting line construction project, and the evaluation results have a scientific guiding role for construction risk control.

Comprehensive Review of Short-Term Voltage Stability Evaluation Methods in Modern Power Systems

The possibility to monitor and evaluate power system stability in real-time is in growing demand. Whilst most stability-related studies focus on long-term voltage stability and frequency stability, very little attention is given to the issue of short-term (voltage) instability. In this paper, the most common evaluation methods present in the literature are summarized, with a focus on their applicability to modern power systems with a large amount of renewable energy integration. The paper presents a first-of-a-kind structured review of this topic. We find that all existing methods have noteworthy limitations that necessitate further improvements. Additionally, the need of having an inclusive short-term instability prediction method is demonstrated, due to strong interactions between various short-term instability mechanisms. These findings provide a good foundation for further research and advancement in the field of real-time stability monitoring.

Stability Analysis of Half-rotating Walking Mechanism with Self-balancing Configuration

Aiming at the problem of dynamic stability of half-rotating walking mechanism, a walking mechanism with self-balancing configuration is proposed. Using D-H method, the transformation matrix between coordinate systems is obtained. Based on the structural and kinematic characteristics of the half-rotating walking mechanism, a new evaluation method for the kinematic stability of the half-rotating walking mechanism is proposed: the stable triangle method. A stable walking strategy of half-rotating walking mechanism is proposed to keep the minimum stable angle as the maximum in the process of motion. Adams motion simulation shows the strategy adopted is reasonable and effective. The stability analysis based on the minimum stability angle shows that the half-rotating walking mechanism can walk stably, and the faster the speed of the half-rotating mechanism is, the weaker the stability of the mechanism is.

Influences of Pore-Water Pressure on Slope Stability considering Strength Nonlinearity

The pore-water pressure is a vital factor in determining the slope stability. To deal with the stability of slopes undergoing pore-water pressures, this paper used the pore-water pressure coefficient to develop the three-dimensional limit analysis method for slope stability evaluation with a nonlinear strength envelope. For numerical slope examples, the critical heights and corresponding critical slip surfaces associated with linear and nonlinear envelopes were derived by using a numerical optimization procedure. The influences of pore-water pressures on the slope stability were addressed by comparing the upper-bound solutions derived by linear and nonlinear strength envelopes (the linear and nonlinear results for short). The obtained two critical inclinations between the linear and nonlinear results both decrease and gradually approach with increasing pore-water pressure coefficient. For most slopes subjected to pore-water pressures, using the linear Mohr–Coulomb envelope will obviously overestimate the slope critical height. The overestimation resulted from the linear criterion will become more distinct for slopes with smaller widths. Besides, the presented results showed that the equivalent internal friction angle tends to have a weaker increasing trend for steeper slopes as pore-water pressure coefficient increases. Hence, when pore-water pressure coefficient increases, the critical slip surfaces of gentle slopes with nonlinear strength criteria become shallower, but the critical slip surfaces of steep slopes seem to have no consistent change law. These results and analyses can illustrate the significance of the application of nonlinear strength envelopes in slope stability evaluation considering pore-water pressures and provide certain reference advice in slope engineering design and landslide prevention.

Surface/Near‐Surface Structure of Highly Active and Durable Pt‐Based Catalysts for Oxygen Reduction Reaction: A Review

Proton exchange membrane fuel cells (PEMFCs) are highly promising energy‐conversion devices because of their zero‐emission and high efficiency. A great deal of Pt is of significant necessity on the cathode to accelerate the rate of kinetically sluggish oxygen reduction reaction (ORR) and maintain the long‐term operation, leading to the prohibitive cost of PEMFCs and limiting their widespread deployment. In the past decades, numerous efforts including manipulation of composition, morphology, and structure have been devoted to improving their higher activity and stability, but still lag behind the actual requirement. ORR is a typical surface‐sensitive electrochemical reaction and its process is mainly determined by surface/near‐surface structure. Herein, the recent advances in the manipulation of surface structure are summarized. The ORR mechanism and evaluation method for activity and stability are introduced. Then, solutions toward the engineering of surface structure and its effect on activity and stability are presented. Finally, comments on the future direction of nanocatalysts for ORR are presented in terms of engineered surface structure.

The Evaluation Method of Rock Mass Stability Based on Natural Frequency

The limit equilibrium method’s analysis index cannot be measured by on-site monitoring equipment and cannot be used for monitoring and early warning of rock instability. The existing rock stability evaluation methods based on vibration information cannot evaluate the stability of rocks quantitatively. In this paper, the slope’s constraints on the rock were simplified to springs and a three-dimensional analysis model of rock vibration was established. The equation for calculating the natural frequency of rock that includes the spring stiffness as an indicator was derived. The rock stability calculation function containing the index of natural frequency was brought into the traditional rock stability coefficient calculation equation, and a new rock stability analysis method based on natural frequency was established. The experiment proved the measurability of the index of the natural frequency of rock and the method’s effectiveness for the stability analysis of the rock based on natural frequency.

Study on fracture occurrence characteristics and wellbore stability of limestone formation

The development of micro fractures in the KT-II formation in a block of China National Petroleum Corporation (CNPC) overseas caused the downhole collapse and touching resistance repeatedly occurs, which seriously hindered the normal drilling process. To solve these problems, the occurrence of fractures in the underground was sorted out based on the field data, and the physicochemical and mechanical properties of the downhole cores were analyzed under different downhole conditions via systematic experiments to determine the main factors affecting the formation collapse and instability. Based on the main control factors of wellbore collapse and experimental data, the wellbore-formation coupling stress field and wellbore stability evaluation and prediction method for unstable KT-II formation were established. Results show that the unstable KT-II strata are mainly fractured limestone strata having a “thousand-layer cake” shape. Clay or mudstone intercalations with strong hydration and expansion capacity can be observed between cracks. Deviation angle, azimuth and fracture tendency have obvious influence on wellbore stability of KT-II fractured limestone formation. The straight hole runs vertically through the fracture plane, and the borehole wall exhibits good stability. When the deviation angle becomes larger than 50°, the weak plane effect of fracture mechanics is prominent and the borehole wall will easily collapse along the crack. For the formation with horizontal fractures, the optimal wellbore stability can be observed when drilling is performed in the direction of the minimum horizontal principal stress. For limestone formation with a certain dip angle fracture, horizontal well is drilled in the direction opposite to the fracture tendency, i.e., the fracture tendency +180° direction, the equivalent density of the collapse pressure is the lowest. The seepage and pressure penetration effects between wellbore and formation lead to an increase in the equivalent density of caving pressure by 0.08–0.1 g/cm 3 . Improving the sealing characteristics of drilling fluid will improve the wellbore stability. The results of this study will provide guidance for achieving effective and safe drilling in fractured limestone formations. • The occurrence of fractures in the underground was sorted out based on the field data, and the main influencing factors of formation collapse and instability were determined through systematic experimental tests. • Based on the main control factors of wellbore collapse and experimental data, the wellbore-formation coupling stress field and wellbore stability evaluation and prediction method for unstable KT-II formation were established. • For limestone formation with a certain dip angle fracture, horizontal well is drilled in the direction opposite to the fracture tendency, the equivalent density of the collapse pressure is the lowest.

An Optical Method for Immediate Evaluation of Microfoam Stability in Foam Sclerotherapy

Objectives: The objective of our study was to develop an optical method that instantly evaluates the stability of sclerosing foam, which would enable early predictions of the clinical performance of the foam and reduce the occurrence of clinical side effects. Methods: Based on the principle of light scattering, we developed a method to optically test foam stability and verified it experimentally using sodium morrhuate (2 mL; 0.05 g/mL) and carbon dioxide. A self-made foam preparation instrument was used to achieve a preparation speed of 275 mm/s. The liquid-gas ratios were considered as 1:3, 1:4, and 1:5. Curves of illuminance with respect to the drainage rate and decay time were obtained. By fitting the curve, the relationship between foam half-life time (FHT) and foam decay was obtained. Thus, foam stability was evaluated using the initial illuminance value; the foam transfer time was approximately 3 s. Results: The experimental FHT varies between 205 and 232 s. Illuminance is exponentially related to drainage rate and linearly related with time. FHT can be expressed by the initial illuminance and illuminance curve fitting coefficients. The half-life of the foam decreases as the initial illuminance value increases, for the same sclerosing drug. The suitability of foam stability is determined by the position of the initial value in the chart. Conclusion: Optical methods are feasible for evaluating foam stability over a short period of time. Clinically predicting the stability of freshly prepared foam can reduce number of incidences of further complications. This will promote the development of foam sclerotherapy and provide a basic understanding of the internal mechanical properties of foam.

A new method for wellbore stability evaluation based on fractured carbonate reservoir rock breaking degree

Borehole wall collapse is rare in the drilling of carbonate rock formations. However, several wells in the Maantang–Leikoupo carbonate formation have collapsed and released blocks to varying degrees, which have caused sticking and hindered efficient development of oil and gas resources. Thus, through the study of macroscopic and microscopic characteristics of carbonate rocks in this area, it is concluded that the fractures in this area are developed. In order to facilitate the analysis of formation fracture development, the concept of formation integrity coefficient which is commonly used in rock engineering was introduced. Firstly, the feasibility of using the formation integrity coefficient to characterize the degree of rock fragmentation was verified by the laboratory acoustic experiment. Finally, the empirical formulas were proposed regarding the formation integrity coefficient and the cohesion of carbonate rocks in this area by combining the laboratory mechanical experiment and acoustic experiment, and a calculation model for the collapse density considering formation integrity was established. Results provide guidance for research on carbonate wellbore stability, especially for fractured carbonate strata.

Optimization and Evaluation of Platooning Car-Following Models in a Connected Vehicle Environment

With the rapid development of information and communication technology, future intelligent transportation systems will exhibit a trend of cooperative driving of connected vehicles. Platooning is an important application technique for cooperative driving. Herein, optimized car-following models for platoon control based on intervehicle communication technology are proposed. On the basis of existing indicators, a series of evaluation methods for platoon safety, stability, and energy consumption is constructed. Numerical simulations are used to compare the effects of three traditional models and their optimized counterparts on the car-following process. Moreover, the influence of homogenous and heterogeneous attributes on the platoon is analyzed. The optimized model proposed in this paper can improve the stability and safety of vehicle following and reduce the total fuel consumption. The simulation results show that a homogenous platoon can enhance the overall stability of the platoon and that the desired safety margin (DSM) model is better suited for heterogeneous platoon control than the other two models. This paper provides a practical method for the design and systematic evaluation of a platoon control strategy, which is one of the key focuses in the connected and autonomous vehicle industry.

Study of the bubble collapse mechanism and its influencing factors on stability under ultra-low surface tension

In this paper, a foam stability model was established to analyze the flow rate, pressure, and gas–liquid phase distribution of the foam during the crushing process, and the evaluation method of foam stability was improved. The results show that the collapsing process of foam is mainly affected by the release of energy inside the foam, and the pressure inside the foam is higher. Before the collapsing of the foam, the velocity of the liquid film position fluctuates and, with the increase in time, the amplitude of the velocity fluctuation increases. When the surface energy between the gas–liquid phases is less than the kinetic energy inside the gas, the bubble collapses and the energy inside the bubble is released. The method of evaluating foam stability was further determined. The stability of foam was analyzed by studying the volume fraction of liquid phase at the location of the foam liquid membrane. For a single bubble, the larger the size of the bubble and the thicker the thickness of the liquid film, the more stable the foam. The density and viscosity of the liquid phase have relatively little effect on foam stability. For the same surfactant, when the surfactant concentration is lower than the critical micelle concentration, the higher the surfactant concentration in the liquid phase, the lower the surface tension between the liquid phase and the gas phase, and the better the foam stability. For different surfactants, the lower the surface tension, the stronger the foaming.