Stability Evaluation Method Research Articles

Optimization of Configuration Design for Underwater Dam Defect Detection Vehicles

Hydropower stations and dams play a crucial role in water management, ecology, and energy. To meet the requirements of underwater dam defect detection, this study develops a streamlined underwater vehicle design and operational framework inspired by bionic principles. A parametric modeling approach was employed to propose the vehicle’s streamlined configuration. Using CFD simulations, hydrodynamic coefficients were calculated and validated through towing experiments in a pool. The hydrodynamic stability of the vehicle was assessed and verified through these analyses. Additionally, various configurations were generated using a free deformation method. An optimization function was established with resistance and stability as the objectives, and the optimal result was derived based on the function’s calculation outcomes. The study designed a high-metacentric underwater vehicle, inspired by the seahorse’s shape, and introduced a novel stability evaluation method. Simulations were conducted to analyze the vehicle’s variable attack angle, drift angle, pitching, and rotational motion at a forward three-throttle speed. The results demonstrate that the vehicle achieves static stability in both the horizontal and vertical planes, as well as dynamic stability in the vertical plane, but exhibits limited dynamic stability in the horizontal plane. After optimizing the original configuration, the forward resistance was reduced by 2.15%, while the horizontal plane dynamic stability criterion CH was improved by 35.29%.

A data-driven evaluation method for tunnel rock stability based on multi-core support vector regression

A data-driven evaluation method for tunnel rock stability based on multi-core support vector regression

Explainable deep learning method for power system stability evaluation with incomplete voltage data based on transfer learning

Explainable deep learning method for power system stability evaluation with incomplete voltage data based on transfer learning

Influence of information flow topology and maximum platoon size on mixed traffic stability

Beyond platooning with pure connected and automated vehicles (CAVs), mixed platooning with both CAVs and human-driven vehicles (HDVs) emerges as a practical formation pattern in mixed traffic flow. This paper investigates how the two types of information flow topology (IFT) as “looking ahead” or “looking behind”, alongside the maximum size of mixed platoons, influence the stability of the entire traffic flow. Precisely, the mixed traffic system is partitioned into three subsystems: independent HDVs, independent CAVs, and mixed platoons, and a dynamical modeling framework is established under two types of specific IFT: Multi-Predecessor Following (MPF) for “looking ahead” and Multi-Successor Leading (MSL) for “looking behind”. Then, a unified string stability evaluation method is proposed, which captures the role of IFT and maximum platoon size, the latter being associated with the emergence probability of different subsystems and CAV penetration rates. Practical considerations, such as the heterogeneity of vehicle dynamics and the absence of HDV communication capabilities, are also incorporated. Extensive numerical analysis and nonlinear traffic simulations reveal that “looking behind” shows superior performance in mitigating traffic perturbations, especially at low penetration rates, compared with the prevailing choice of “looking ahead”. In addition, increasing the platoon size could further enhance traffic flow stability. These results provide practical insights into the design of IFT and platoon size for CAV cooperation in future mixed traffic environments.

Shale Fracture Static Stability Evaluation Method Based on 3D Discrete Fracture Model: A Case Study on the Luzhou Area in Southern Sichuan Basin, SW China

Abstract The stress interference in deep shale may lead to shale fracturing and instability and consequently results in engineering risks such as casing deformation in horizontal wells. Therefore, in the early stages of shale gas exploration and development, it is of great significance to evaluate the stability of shale fractures in advance. The stability evaluation of shale reservoir faults can be mainly divided into two categories at present: quantitative evaluation of single faults and qualitative evaluation of wide-range faults. The quantitative evaluation of single faults primarily relies on numerical simulation techniques, while the qualitative evaluation of wide-range faults primarily employs geophysical methods. Both methods are difficult to meet the needs of shale gas exploration and development. The shale fracture stability evaluation method based on 3D discrete fracture model which is developed in this article can quantitatively evaluate the static stability of wide-range shale fractures in the early stage of exploration and development. In this article, seismic geometric attributes were calculated, and fracture seismic facies was established by means of the Bayesian probabilistic cluster analysis method. Then, 3D discrete fracture modeling under the constraint of fracture seismic facies was performed to establish a discrete fracture model. Finally, according to the Mohr–Coulomb criterion, the shear stress and effective normal stress of discrete fracture were calculated by using the formation pressure data in other exploration and development results and the regional in situ stress obtained through seismic prestack inversion. And thus, the stability evaluation of the fractures in shale reservoirs was eventually completed. In addition, this method was verified by using the casing deformation points in some actual shale-gas horizontal wells, the actual small fault points, and microseismic data. It indicates that the method has higher accuracy and is better applicable to the early shale gas exploration and development.

Stability evaluation method of gasification coal pillar under thermal coupling condition for prevention of environment secondary pollution

The instability of gasification coal pillars can easily induce the further development of water-conducting fractures, which leads to the connection of gasification combustion space and aquifer, and then causes groundwater pollution. Therefore, it is crucial to assess the stability of gasification coal pillar to forestall the potential risk of environmental contamination resulting from underground coal gasification. In this paper, based on the shape of the combustion space area of underground coal gasification, considering the influence of the mechanical properties of the coal pillar and the temperature field under the condition of thermal coupling, the calculation method of the yield zone width of gasification coal pillar is proposed. Considering the destabilizing factors affecting the coal pillar and the relationship between actual and ultimate bearing capacities after stripping and yielding, a stability evaluation method for the ‘hyperbolic’ coal pillar is proposed. Additionally, the effects of various factors on the stripping, yielding, and safety factor of the coal pillar are analyzed. The new method was applied to the Ulanqab underground coal gasification test site, which proved its effectiveness. The research results are of great practical significance for designing underground coal gasification production and preventing environmental pollution.

Investigating the Immediate Effects of Static and Dynamic Stretching Exercises of Lower Extremities Muscles on Core Stability in Young Healthy Females

Introduction: This study investigates the immediate effects of warm-up exercises, specifically static and dynamic stretches for the lower extremities, on strength, endurance, flexibility, motor control, and core stability function in young, healthy females. Materials and Methods: A total of 60 healthy, active women aged 19-30 years were randomly divided into three groups as follows: Static stretching (SS), dynamic stretching (DS), and a control group (CG), which received no exercises. Evaluation methods for core stability included strength, endurance, sit-and-reach, Y-balance, and bilateral squat tests. Meanwhile, these tests were conducted before and after the prescribed exercise protocols. Results: Both the SS and DS groups experienced significant increases in all core stability components compared to their baseline values (P<0.05). Meanwhile, the analysis of variance/ analysis of covariance indicated that immediately after performing the stretching exercises, the SS and DS groups exhibited significantly greater improvements in parameters, such as strength, endurance, flexibility, and balance tests (except for the posterior-medial direction) when compared to the CG (P<0.05). Regarding functional parameters after the exercises, there were no statistically significant differences between the study groups (P>0.05). In addition, dynamic exercises demonstrated a higher effectiveness than static exercises for most parameters (P<0.05). Conclusion: Warm-up exercises, involving both static and dynamic stretches for lower limb muscles appear to have an immediate positive impact on core stability parameters. In sports that demand strong trunk muscles and balance, the dynamic protocol may be more effective

Influence Analysis of Material Parameter Uncertainties on the Stability Safety Factor of Concrete Gravity Dams: A Probabilistic Method

Anti-sliding stability safety is a critical issue that must be given sufficient and widespread attention during the entire lifecycle of gravity dams. The calculated anti-sliding stability safety factor (ASS-SF) is usually compared with the allowable value required by the standards in the traditional method, which ignores the influence of material parameter uncertainties and leads to unreasonable safety evaluation results. Therefore, the nonlinear functional relationship between the stability safety factor (SF) and the random variable parameters is constructed based on the response surface equations, and the distribution types of SF sequences calculated by the Monte Carlo sampling are determined, then a probabilistic stability evaluation method for concrete gravity dams is proposed. Engineering application shows that the calculated SF obeys the normal distribution; the minimum guaranteed rate of different sliding paths in a gravity dam is 86.66%, and the guaranteed rate for the overload safety factor (OSF) is 36.00%. The results imply that a guaranteed rate for the allowable value of the ASS-SF should be provided when making the stability safety evaluation of the dams, especially the OSF. The outcome of this research will advance the understanding of stability evaluation of concrete dams, and reduce the potential risk of sliding instability of concrete dams.

Evaluation Method of Magnetic Field Stability for Robotic Arc Welding Based on Sample Entropy and Probability Distribution

In this study, we analyzed the arc magnetic field to assess the stability of the arc welding process, particularly in robotic welding where direct measurement of welding current is challenging, such as under water. The characteristics of the magnetic field were evaluated based on low-frequency fluctuations and the symmetry of the signals. We used double-wire pulsed MIG welding for our experiments, employing Q235 steel with an 8.0 mm thickness as the material. Key parameters included an average voltage of 19.8 V, current of 120 A, and a wire feeding speed of 3.3 m/min. Our spectral analysis revealed significant correlations between welding stability and factors such as the direct current (DC) component and the peak power spectral density (PSD) frequency. To quantify this relationship, we introduced a novel approach using sample entropy and mix sample entropy (MSE) as new evaluation metrics. This method achieved a notable accuracy of 88%, demonstrating its effectiveness in assessing the stability of the robotic welding process.

Stability Evaluation Method of High Fill Loess Foundation Based on Numerical Simulation

In order to understand the stability evaluation method of high fill loess foundation, the author proposes a study on the stability evaluation method of high fill loess foundation based on numerical simulation. The author first established a three-dimensional finite element model of a multi-level high fill slope using PLAXIS 3D software based on a loess high fill slope engineering project in a certain section of northwest China. The study investigated the effects of changes in fill materials, fill boundaries, slopes, and unloading platforms on slope stability. Secondly, based on the vertical and horizontal displacement of the top and foot of each level of slope under step-by-step filling, the distribution pattern of the most dangerous points of each level of slope and the overall deformation trend of the slope were analyzed. The results indicate that the cohesion and internal friction angle of the filling material are key factors affecting the stability of high fill slopes. Reducing the height of the steps at the boundary between the filling and the undisturbed soil, deepening the width of the steps, reducing the slope, and widening the unloading platform can all improve the stability of the slope. During the construction of lower slopes, there is a significant vertical displacement mutation, while the horizontal displacement mutation is relatively slow; After the construction is completed, the deformation situation is good, and the vertical and horizontal displacement of the higher slope during construction changes greatly, with uneven distribution; After the completion of construction, the consolidation settlement period is long and the deformation is large; Emphasis should be placed on strengthening deformation monitoring at high altitudes after construction is completed. Finally, the platform width can be selected within this range based on the actual engineering situation. After the platform width is greater than 3.6m, as sufficient platform width has been reached at this point, further increasing the platform width has little impact on the safety factor, and the curve gradually flattens out. The research results have determined the stability influencing factors, deformation trends, and development laws of loess high fill slopes in the northwest region, providing a scientific basis for further research on deformation control of loess high fill slopes.

SE-CNN based emergency control coordination strategy against voltage instability in multi-infeed hybrid AC/DC systems

For receiving-end power systems with multi-infeed HVDCs and large-scale renewable energy generation, the challenges of weak reactive power support and limited anti-interference capacity pose a threat to the power system voltage stability. To enhance the voltage stability under large disturbances, this paper proposes a data-driven method for coordinated emergency control strategy against voltage instability in multi-infeed hybrid AC/DC systems based on the squeeze and excitation (SE) module and convolutional neural network (CNN). Firstly, the SE module and CNN are integrated to intuitively capture correlations among various feature channels and extract key features related to voltage stability levels. Secondly, a voltage stability evaluation method is proposed based on the SE-CNN model, utilizing a dual channel structure to unveil the quantitative relationship between key response characteristics and voltage stability margin. Finally, regarding the control measures containing load shedding and DC modulation, the emergency control sensitivity index is proposed to assess the stability margin improvement effect of various control objects, and the optimal emergency control strategy is formulated to coordinate multiple voltage stability emergency control measures. Case studies were conducted on a typical China local region receiving-end power grid test system with voltage instability problems, and the simulation results verified the effectiveness of the proposed method. © 2017 Elsevier Inc. All rights reserved.

A stability evaluation method for deep-seated toppling in the upper Lancang river, Southwestern China

Deep-seated toppling in the upper reaches of the Lancang River, southwest China involves deformations exceeding 100 m in depth. The slope deformation is initiated by river downcutting and evolves distinctive characteristics with a depth of river incision. In this study, we propose a system for evaluating the stability of deep-seated toppled slopes in different evolutionary stages. This system contains identification criteria for each evolutionary stage and provides the corresponding stability evaluation methods. Based on the mechanical and kinematic analysis of slope blocks, the specific stage of slope movement can be identified in the field through outcrop mapping, in situ tests, surface displacement monitoring, and adit and borehole explorations. The stability evaluation methods are established based on the limiting equilibrium theory and the strain compatibility between the undisturbed zone and the toppled zone. Finally, several sample slopes in different evolution stages have been investigated to verify the applicability and accuracy of the proposed stability evaluation system. The results indicate that intense tectonic activity and rapid river incision lead to a maximum principal stress ratio exceeding 10 near the slope surface, thus triggering widespread toppling deformations along the river valley. When considering the losses of joint cohesion during the further rotation process, the safety factor of the slope drops by 7%–28%. The self-stabilization of toppling deformation can be recognized by the layer symmetry configuration after the free rotation of the deflected layers. Intensely toppled rock blocks mainly suffer sliding failures beyond the layer symmetry condition. The factor of safety of the K73 rockslide decreased from 1.17 to 0.87 by considering the development of the potential sliding surface and the toe-saturated zone.

An image-processing method based on regional separation-parameter coupling for the stability analysis of biodiesel flame

Flame stability is vital to obtain good combustion performance. Therefore, the development of flame stabilization technologies and stability evaluation methods has always received considerable research attention. However, the existing evaluation methods have low precision, which makes it difficult to accurately assess the flame stability. To address this issue, we proposed an effective flame state evaluation method in this study. We conducted relevant combustion experiments, and applied the proposed method to evaluate the flame stability of biodiesel. Furthermore, we established a numerical evaluator of the flame state based on a regional separation-parameter coupling image-processing method. This numerical evaluator combines the statistical characteristics of six flame parameters, which we derived from the flame images. The experimental results suggested that the proposed method can be used to determine some characteristic parameters that cannot be obtained by traditional methods, such as oscillation frequency and propagation velocity. Notably, these characteristic parameters are important for the evaluation of flame stability. At an oxygen concentration of 24 % and fuel pressure of 0.5 MPa, we subdivided the combustion state of biodiesel into stable, relatively stable, unstable, and extinguished states. We observed that by decreasing the airflow rate from 0 to 12.50 m3/h, the flame color changed from orange to green, then blue, and finally to yellow-green. We also observed, contraction and spreading in the flame highlight region. The color space analysis revealed that the larger the blue-to-red ratio, the more complete the combustion, which led to a blue flame. Overall, the proposed evaluation method provides a useful guide for regulating the combustion of biodiesel. Furthermore, these result can be generalized to assess the combustion states of other fuels.

Optimization and classification control of permanent basic farmland based on quality classification

Permanent basic farmland plays an important role in stabilizing agricultural production and ensuring national food security. Therefore, it is necessary to reasonably delineate and control permanent basic farmland. This article is based on the idea of classifying the quality of cultivated land resources, combined with the rules for the delineation of permanent basic farmland, and from the perspective of the synergy of “suitability-connectivity-stability” of cultivated land, a indicator system is constructed. Application of suitability, connectivity, and stability evaluation methods. Taking Zhangshu City, Jiangxi Province as an example, the status of cultivated land resources is comprehensively evaluated, and permanent basic farmland is optimized and graded for protection. The results show that: (1) the arable land in Zhangshu City is mainly of medium suitability, medium continuity and high stability. (2) Zhangshu City is divided into 43218.80 hm2 of permanent basic farmland, accounting for 79.35% of the total area of cultivated land. (3) Control and partition permanent basic farmland into three categories: core protected areas for permanent basic farmland, quality improvement areas, and key transformation areas. The above results indicate that this evaluation has a supportive role in supporting the spatial optimization and hierarchical management of permanent basic farmland, and is of great significance for the unified management of natural resources.

Dynamic stability analysis method of anchored rocky slope considering seismic deterioration effect

The seismic deterioration effects of anchor cables and slope structural planes are often neglected in the dynamic stability analysis of anchored rocky slopes to the extent that the stability of slopes is overestimated. In this paper, a dynamic calculation method for anchored rocky slopes considering the seismic deterioration effect is established, and a stability evaluation method for anchored rocky slopes based on the Gaussian mixture model is proposed. The seismic deterioration effect on the stability of anchored rocky slopes is quantitatively analyzed with an engineering example, and the relationship between seismic intensity and the failure probability of slopes is clarified. The results show that compared with the calculation method without considering the seismic deterioration effect, the minimum safety factor and post-earthquake safety factor obtained by the proposed method in this paper are smaller. The number of seismic deteriorations of the slope is used as the number of components of the Gaussian mixture model to construct the failure probability model of the slope, which can accurately predict the failure probability of anchored rocky slopes. The research results significantly improve the accuracy of the stability calculation of anchored rocky slopes, which can be used to guide the seismic design and safety assessment of anchored rocky slopes.

Quick Extraction of Joint Surface Attitudes and Slope Preliminary Stability Analysis: A New Method Using Unmanned Aerial Vehicle 3D Photogrammetry and GIS Development

The present study proposes a preliminary analysis method for rock mass joint acquisition, analysis, and slope stability assessment based on unmanned aerial vehicle (UAV) photogrammetry to extract the joint surface attitude in Geographic Information Systems (GIS). The method effectively solves the difficulties associated with the above issues. By combining terrain-following photogrammetry (TFP) and perpendicular and slope surface photogrammetry (PSSP), the three-dimensional (3D) information can be efficiently obtained along the slope characteristics’ surface, which avoids the information loss involved in traditional single-lens aerial photography and the information redundancy of the five-eye aerial photography. Then, a semi-automatic geoprocessing tool was developed within the ArcGIS Pro 3.0 environment, using Python for the extraction of joint surfaces. Multi-point fitting was used to calculate the joint surface attitude. The corresponding attitude symbols are generated at the same time. Finally, the joint surface attitude information is used to perform stereographic projection and kinematic analysis. The former can determine the dominant joint group, and the latter can obtain the probability of four types of failure, including planar sliding, wedge sliding, flexural toppling, and direct toppling. The integrated stability evaluation method studied in this paper, which combines a 3D interpretation of UAV and GIS stereographic projection statistical analysis, has the advantages of being efficient and user-friendly, and requires minimal prior knowledge. The results can aid in the geological surveys of slopes and guide engineering practices.

A novel primary stability test method for artificial acetabular shells considering vertical load during level walking and shell position.

Uncemented acetabular shell primary stability is essential for optimal clinical outcomes. Push-out testing, rotation testing, and lever-out testing are major evaluation methods of primary stability between the shell and bone. However, these test methods do not consider shell loads during daily activity and shell installation angle. This study proposes a novel evaluation method of acetabular shell primary stability considering load during level walking and acetabular installation angles such as inclination and anteversion. To achieve this, a novel primary stability test apparatus was designed with a shell position of 40° acetabular inclination and 20° anteversion. The vertical load, corresponding to walking load, was set to 3 kN according to ISO 14242-1, which is the wear test standard for artificial hip joints. The vertical load was applied by an air cylinder controlled by a pressure-type electro-pneumatic proportional valve, with the vertical load value monitored by a load cell. Torque was measured when angular displacement was applied in the direction of extension during the application of vertical load. For comparison, we also measured torque using the traditional lever-out test. The novel primary stability test yielded significantly higher primary stabilities; 5.4 times greater than the lever-out test results. The novel primary stability test failure mode was more similar to the clinical failure than the traditional lever-out test. It is suggested that this novel primary stability test method, applying physiological walking loads and extension motions to the acetabular shell, better reflects in vivo primary stability than the traditional lever-out test.

Influencing factors and evaluation methods for early stability of immediate implant.

At present, implant restoration has become a hot research topic in the field of prosthodontics. The in-depth studies of new materials and new technologies enable immediate implantation, immediate and early loading to be realized, which meets the needs of patients for shortening the course of implant restoration and obtaining better aesthetic effects. However, compared with the traditional delayed implantation technology, it is equally challenging for clinicians how to achieve and even improve the initial and long-term stability of implants in order to raise the success rate of implant restoration. The initial stability of the implant is influenced by a combination of factors, including the implant, the patient's condition, and the surgical procedure. Recently, there have been a lot of studies on the influencing factors and common research methods for immediate implant stability and bone healing. Summarizing and analyzing them can provide reference for preoperative evaluation, surgical plan and loading timing of immediate implant restoration in the later stage.

Stability analysis of pumped storage hydropower plant in abandoned open-pit mine affected by dynamic surface subsidence of combined mining.

The construction of a pumped storage hydropower plant (PSHP) in an abandoned open-pit mine is a potential alternative to green mining and energy storage, which can increase the utilization rate of renewable energy and develop residual resources of abandoned mines. Dynamic surface subsidence affected by combined underground and open-pit mining (CUOPM) seriously affects the construction and operation of the PSHP and is one of the critical scientific issues that needs to be solved immediately. The stability of the PSHP was analyzed and treatment scheme of the goafs was proposed based on on-site measurement, theoretical analysis, and numerical simulation. First, the distribution of goafs in the Haizhou open-pit mining area was investigated and surface subsidence value was obtained using InSAR technology and ground monitoring. Secondly, the surface subsidence mechanism affected by CUOPM is analyzed and indicates the subsidence maximum values and scope of influence are greater than those of single underground mining. A dynamic surface subsidence prediction model for combined mining is established based on the Knothe time function model. Thirdly, based on the CVISC model, the numerical calculation models were established by using FLAC3D, and the characteristics and laws of surface subsidence in different periods of CUOPM were studied. The comparative analysis of the observation results shows that the proposed model and numerical simulation calculation method have excellent applicability and accuracy. Finally, a stability evaluation method of PSHP was established, and the results of the evaluation show that the affected areas are the semi-ground powerhouse (SGPH) and the west side of the lower reservoir. The method of grouting filling was used to treat the goafs, and the results showed that it effectively alleviates the dynamic surface subsidence affected by CUOPM, and provides a safety guarantee for PSHP.

Disturbed zone calculation and stability evaluation method of footwall slope with slip-shear failure under excavation

Disturbed zone calculation and stability evaluation method of footwall slope with slip-shear failure under excavation