Dynamic Safety Factor Research Articles

Analisis deformasi pada coupling element dari automatic mechanical coupler: studi kasus LRT Palembang

Coupler merupakan komponen yang menyambungkan gerbong kereta. Kekuatan coupler terhadap beban eksepsional dan ketahanannya terhadap beban kerja normal menjadi parameter keamanan yang sangat penting dalam operasinya. Kajian ini melakukan analisis deformasi secara numerik terhadap coupling element dari automatic mechanical coupler yang digunakan pada tipe kereta ringan (Light Rail Transit, LRT) berdasarkan beban aktual yang diterima. Bagian coupling element yang diteliti adalah coupling link dan hooked plate. Model solid 3D dibuat tanpa penyederhanaan untuk hasil simulasi yang lebih mendekati fenomena aktual. Material isotropik yang digunakan adalah baja ASTM A633 Grade E. Simulasi statis dan transien dilakukan untuk mendapatkan faktor keamanan statik dan dinamik. Simulasi fatik dari analisis pembebanan transien dengan tiga mode pembebanan dilaksanakan untuk memperkirakan umur kerja coupling element. Hasil simulasi menunjukkan bahwa coupling element yang diobservasi aman terhadap beban eksepsional dan normal yang diberikan. Selain itu, simulasi mengindikasikan bahwa komponen yang kritis berdasarkan tegangan von Mises maksimum adalah coupling link dan komponen yang kritis berdasarkan siklus umur adalah hooked plate.

Analysis of seismic Response and Slope Stability for Intake Tunnel Entrance of Hongyan River Nuclear Project

The principle of dynamic analysis of Flac3D, setting of boundary condition and the solving method of dynamic safety factor for slope are introduced in this article firstly, and the three-dimensional finite difference model of the portal of intake tunnel is built by Flac3D which uses the nonlinear dynamic analytical method to simulate response regularity of the portal of intake tunnel and the high slope backfilled here under seismic load for Hongyan River nuclear intake tunnel first-stage project in Liaoning province. The corresponding change rule of the internal force of tunnel entrance under the effect of running safe seismic load SL1 and ultimate safe seismic load SL2 is gotten by time-histories changing curve under the effect of different seismic and the comparison of tunnel lining internal force diagram; the location sliding surface and dynamic safety factor time-histories curve of the high slope backfilled at the tunnel entrance are gotten by building two-dimension finite element model and doing stability analysis under seismic. Analysis result shows that for tunnel entrance, the analysis method and conclusions of the seismic weak position of the tunnel portal are the sidewall and getting the location of sliding surface and minimum dynamic safety factor time-histories curve of high slope. For similar nuclear power intake tunnel project, the conclusion can be a reference and have a certain reference value for the seismic design of tunnel.

Attachment Beyond the Adhesive System: The Contribution of Claws to Gecko Clinging and Locomotion.

Attachment is imperative for many biological functions, such as holding position and climbing, but can be challenged by natural conditions. Adhesive toe pads and claws have evolved in multiple terrestrial lineages as important dynamic attachment mechanisms, and some clades (e.g., geckos) exhibit both features. The functional relationship of these features that comprise a complex attachment system is not well-understood, particularly within lizards (i.e., if pads and claws are redundant or multifunctional). Geckos exhibit highly adept frictional adhesive toe pads that continue to fuel biological inquiry and inspiration. However, gecko claws (the ancestral lizard clinging condition) have received little attention in terms of their functional or evolutionary significance. We assessed claw function in Thecadactylus rapicauda using assays of clinging performance and locomotor trials on different surfaces (artificial and natural) and inclines with claws intact, then partially removed. Area root mean square height (Sq), a metric of 3D surface roughness, was later quantified for all test surfaces, including acrylic, sandpaper, and two types of leaves (smooth and hairy). Maximum clinging force significantly declined on all non-acrylic surfaces after claw removal, indicating a substantial contribution to static clinging on rough and soft surfaces. With and without claws, clinging force exhibited a negative relationship with Sq. However, claw removal had relatively little impact on locomotor function on surfaces of different roughness at low inclines (≤30°). High static and dynamic safety factor estimates support these observations and demonstrate the species' robust frictional adhesive system. However, maximum station-holding capacity significantly declined on the rough test surface after partial claw removal, showing that geckos rely on their claws to maintain purchase on rough, steeply inclined surfaces. Our results point to a context-dependent complex attachment system within geckos, in which pads dominate on relatively smooth surfaces and claws on relatively rough surfaces, but also that these features function redundantly, possibly synergistically, on surfaces that allow attachment of both the setae and the claw (as in some insects). Our study provides important novel perspectives on gecko attachment, which we hope will spur future functional studies, new evolutionary hypotheses, and biomimetic innovation, along with collaboration and integration of perspectives across disciplines.

Limit analysis under seismic conditions of a slope reinforced with prestressed anchor cables

Based on limit analysis and pseudo-dynamic methods, a proposed method for evaluating slope stability under seismic conditions that considers dynamic changes in the axial force of the anchor cables is presented. The case study shows that compared to the computational conditions that neglect the dynamic changes in axial forces, the dynamic safety factors obtained by the proposed method are greater, whereas the dynamic variation amplitudes of the dynamic safety factors obtained by the proposed method are smaller. The better anti-seismic effect of the anchor cables due to considering the dynamic changes in axial forces is reflected by the proposed method.

Three-dimensional stability analysis of seismically induced landslides using the displacement-based rigorous limit equilibrium method

Previously, the stability analysis of seismically induced landslides was investigated by the factor of safety of the entire sliding body, which provided no information on the displacements of the analyzed seismically induced landslides. The landslides are assessed to be dangerous when the minimum value of the factor of safety (Fs) is less than a critical value. However, unlike the landslides subjected to static loads, the dynamic safety factors of seismically induced landslides vary with time. The minimum value of the dynamic safety factors being less than the critical value does not necessarily imply failure of the seismically induced landslides. In this paper, the three-dimensional displacement-based rigorous limit equilibrium method is proposed to study the displacements of seismically induced landslides. The relationship between the shear stresses acting on the base of the columns and the shear displacements is established based on the hyperbolic soil model. By introducing the strength reduction technique, the relationship between the reduction factor (RF) and the accumulated vertical displacement can be obtained. According to the definition of the strength reduction method, the safety factors of seismically induced landslides are determined, which do not vary with time. Then, the landslides can be assessed to be dangerous when the minimum value of Fs is less than a critical value.

Proračun čvrstoće točkova železničkih vozila

This paper presents a methodology for calculating strength of railway vehicles wheel, according to current international standards. The methodology is demonstrated by the example of monoblock wheel of a standard wheelset of a freight wagon for a axle load of 200 kN. Analysis of stress-strain states and static and dynamic safety factor of wheel was performed using the finite element method in the software package ANSYS. For determination sizes of contact surface at places where loads are placed, Hertz contact theory between two elastic bodies was applied. The obtained result showed that the analyzed wheel has the necessary safety factor and satisfies all the strength criteria defined by the standards.

Dynamic Stability Analysis of Arch Dam Abutment Based on Strength Reduction Method

Dynamic stability analysis of dam abutment is related to safety, reliability and rationality, which gives significant consideration on arch dam development. This paper aims at an engineering project, using static and dynamic combined method, firstly to slove the static forces from dam body to dam abutment; Then using strength reduction method combined with seismic load got from response spectrum with the same strength reduction factor to get the dynamic safety factor. The result s provide design basis for the projects.

Dynamic stability of composite foundation under different area replacement ratio based on intelligent sensing technology

Oil storage tanks are widely used in petrochemical industry. But the improper foundation treatment is likely to cause the damage of structure and accessory components under the action of earthquake, as a result, environmental pollution and fire will be caused by chemical leakage. Therefore, it is necessary to study the dynamic stability and the security affecting factors of composite foundation. Taking foundation treatment of one oil depot belong to Petro China as the engineering background, the discrete compacted piles arranged by equilateral triangle are simplified by the equivalent continuum method. Contacts are set between pile and soil, between concrete foundation and subsoil, and between concrete foundation and tank to reflect the mechanical behavior of the system as far as possible. The composite foundation with three kinds of area replacement ratios are studied by the dynamic stability analysis. The results show that safety factors corresponding to the three area replacement ratios are all greater than the general safety factor 2 which is required in engineering; the dynamic safety factors increase with the increase of area replacement ratio. Besides, area replacement ratio has a great influence on the distribution of plastic zone. Therefore, in the actual project, taking into account the dynamic safety factor and the distribution of plastic zone, there is an optimal area replacement ratio, and it may not only meet requirements for engineering safety, but make use of materials rationally and increase economic benefits.

Analysis on seismic dynamic response and liquefaction area of tailings dam

Taking a tailings dam in Hebei as the research object, the dynamic response of the dam under action of flood and earthquake is simulated by using a finite element software, and the seismic dynamic responses of the dam with respect to acceleration, stress, displacement, liquefaction area and stability are analysed. The results show that the vertical acceleration increases with the height of the dam, the horizontal acceleration is gradually increasing from outside to inside. A larger horizontal and vertical displacement occurs at the 3/4 height of tailings dam. After considering the relative density of the tailings dam and drainage condition, all the three kinds of seismic waves cause a small range of liquefaction area. The stability of the tailings dam is calculated with Sweden Arc Method, showing dynamic stability safety factor is 1.257 when considering drainage, which is larger than code value, indicating the tailings dam is stable in the case of earthquake.

Analysis on seismic dynamic response and liquefaction area of tailings dam

Taking a tailings dam in Hebei as the research object, the dynamic response of the dam under action of flood and earthquake is simulated by using a finite element software, and the seismic dynamic responses of the dam with respect to acceleration, stress, displacement, liquefaction area and stability are analysed. The results show that the vertical acceleration increases with the height of the dam, the horizontal acceleration is gradually increasing from outside to inside. A larger horizontal and vertical displacement occurs at the 3/4 height of tailings dam. After considering the relative density of the tailings dam and drainage condition, all the three kinds of seismic waves cause a small range of liquefaction area. The stability of the tailings dam is calculated with Sweden Arc Method, showing dynamic stability safety factor is 1.257 when considering drainage, which is larger than code value, indicating the tailings dam is stable in the case of earthquake.

Calculation models and stability of composite foundation treated with compaction piles

Composite foundation treated with compaction piles can eliminate collapsibility and improve the bearing capacity of foundation in loess area. However, the large number of piles in the composite foundation leads to difficulties in the analysis of such type of engineering works. This paper proposes two simplified methods to quantify the stability of composite foundation treated with a large number of compaction piles. The first method is based on the principle of making the area replacement ratios of the simplified model as the same time as the practical engineering situation. Then, discrete piles arranged in a triangular shape can be simplified in the model where the annular piles and compacted soil are arranged alternately. The second method implements equivalent continuous treatment in the pile-soil area and makes the whole treated region equivalent to a type of composite material. Both methods have been verified using treated foundation of an oil storage tank. The results have shown that the differences in the settlement values obtained from the water filled test in the field and those calculated by the two simplified methods are negligible. Using stability analysis, the difference ratios of the static and dynamic safety factors of the composite foundation treated with compaction piles calculated by these two simplified methods are found to be 3.56% and 5.32%, respectively. At the same time, both static and dynamic safety factors are larger than the general safety factor, which should be greater than or equal to 2.0 according to the provisions in civil engineering. This indicates that after being treated with compaction piles, the bearing capacity of the composite foundation is effectively improved and the foundation has enough safety reserve.

Study on the Influence of Elevation of Tailing Dam on Stability

This paper takes Yunnan as the object of a tailing, by theoretical analysis and numerical calculation method of the effect of seismic load effect of elevation on the stability of the tailing, to analyse the stability of two point driven safety factor and liquefaction area. The Bishop method is adopted to simplify the calculation of dynamic safety factor and liquefaction area analysis using comparison method of shear stress to analyse liquefaction, so we obtained the influence of elevation on the stability of the tailing. Under the earthquake, with the elevation increased, the safety coefficient of dam body decreases, shallow tailing are susceptible to liquefy. Liquefaction area mainly concentrated in the bank below the water surface, to improve the scientific basis for the design and safety management of the tailing.

Research on the two-way defense model of large data dynamic security SAT

To guarantee the safety of big data calculation, the concept of security research and trusted cloud combined with large data security, a two-way defense system model of a large data calculation of SAT. The model of user data evidence through the dynamic safety factor; gradually determine the behavior of security permissions according to the reliability test implementation behavior. Provide the maximum-security defense for users. the experimental results show that the model can effectively improve the data big data security, reduce malicious hackers, to improve the efficiency of data analysis.

Pre-Alarm System Based on Real-Time Monitoring and Numerical Simulation Using Internet of Things and Cloud Computing for Tailings Dam in Mines

The tailings dam, a necessary facility to maintain the normal operation of mining enterprises, is a hazard source of human-caused debris flow with high potential energy. The real-time pre-alarm for the instability of tailings dam is vital to ensure the normal mining and safety of human lives and properties. Based on the Internet of Things and wireless networks, the multiple and the key information system of tailings dam is constructed using the sensor data, which include the stability indexes like phreatic line, reservoir water level, internal and external deformation of the tailings dam. The cloud platform is applied to predict the future state of the phreatic line based on real-time monitoring data, where the equation of phreatic line can be obtained. The numerical simulation model is established by considering the predicted equation of phreatic line, limit equilibrium state parameters, reservoir water level, and rainfall. Then, the safety factor, random reliability, and interval non-probabilistic reliability can be solved out through the cloud platform. Combined with the trend of real-time monitoring deformation, as well as calculated dynamic safety factor, random reliability, and interval non-probabilistic reliability, the stable or dangerous warning signals of tailings dam can be obtained by the remote real-time pre-alarm system. The main solved method for the key parameters and pre-alarm process are presented through a case study. It is proved that the pre-alarm system is an efficient and real-time platform for the tailings dam stability with the integration and mutual validation of key information.

Stability analysis of two-dimensional landslides subjected to seismic loads

In the past, the pseudo-static method used to be the most common for evaluating the stability of landslides under seismic loads, in which static forces acting on the center of gravity of a sliding body are used to consider the effects of earthquake. However, seismic loads of rock and soil differ from time and location to time and location. Obviously, it is irrational for the pseudo-static approach to be applied to solving dynamic problems. In this paper, a displacement-pseudo-dynamic model is proposed to assess seismic stability of landslides, in which the sinusoidal-cosinusoidal wave is applied to simulating earthquake displacement, and an “amplification factor” of peak seismic displacement is referred to as the amplification of seismic wave when it propagates from the bottom to the top of the landslide. The effects of physico-mechanical behaviors of a sliding body on seismic stability of soil slopes are taken into account as well as inertia forces and damping forces. The sensitivity analyses on the permanent displacement and the dynamic factor of safety of landslides are studied in detail. Moreover, a large-scale Tangjiashan landslide that occurred in Wenchuan earthquake is investigated to verify the robustness and precision of the present method. It is found that the results from the present method is in good agreement with those from the previous method.

Study on Slope Stability Evaluation Methods under Seismic Load

Slope dynamic factor of safety (FOS) under earthquake was calculated based on time history analysis method and compared with acceleration time history to analyze correspondence between them. In view of the fact that earthquake is a dynamic process, this paper proposed that three respects can be considered to analyze the slope stability rather than adopting a single FOS value. Firstly, the variation trend of the FOS time history can be combined with the forces on key points to analyze slope stability. Secondly, the displacement and stress vector fields can be adopted to evaluate the final slope stability. Thirdly, the variation trend of the displacement and velocity time history can be used as well. The above methods are applied to Beihoushan landslide in Hanyuan in Wenchuan earthquake to evaluate slope stability under earthquake and the analysis shows that the slope is stable as a whole.

Dynamic stability analysis of wedge in rock slope based on kinetic vector method

A new method (kinetic vector method, KVM) is presented for analyzing the dynamic stability of wedge in rock slope. The dynamic analysis is carried out based on three dimensional distinct element code (3DEC), and the kinetic inertial force of the wedge under seismic loading can be obtained via calculating the net vectorial nodal force of the finite difference grid. Then, the factor of safety (FOS) of the wedge can be calculated based on limit equilibrium method (LEM) at each dynamic analysis step, therefore time series of the FOS for whole earthquake process can be obtained. For the purpose of evaluating the entire dynamic stability of the wedge, dynamic factor of safety (DFOS) is proposed and defined as a numerical value corresponding with a given rate of probability guarantee based on reliability theory. Consequently, the KVM inherits the merits of the LEM and also has fully nonlinear dynamic analysis capabilities, and the feasibility and correctness of the KVM are tested by an example given by Hoek and Bray (1981). Finally, a rock slope case in Wenchuan Earthquake regions of China is presented to verify the engineering practicability of the KVM, and the results matched the actual situation well.

Dynamic response of underground gas storage salt cavern under seismic loads

A dynamic elastoplastic damage constitutive model is proposed based on the failure characteristic of rock salt under seismic loads. The coding of the proposed model is achieved by the embedded FISH (short for FLACish) language of FLAC3D (Fast Lagrangian Analysis of Continua). Numerical models of bedded salt cavern gas storage facilities in China are developed by using FLAC3D, and the proposed constitutive model is used in the simulations. The effects of seismic input angle, seismic acceleration, seismic moment, types of seismic waves, and gas pressure on the dynamic response, stress, displacement, plastic zone, and safety factor (SF) of rock masses that surround salt cavern gas storage facilities are studied. Results show that the seismic wave perpendicular to the surface poses the greatest risk to the safety of the cavern. With an increase in seismic acceleration, the cavern’s SF decreases and that of the lower structure of the cavern decreases more than that of the upper section. Plastic zones propagate from the cavern’s internal surface to the pillar, and then to the pillar and floor along the right and left corners of the cavern bottom. Higher internal gas pressure improves cavern safety. The acceleration and duration of seismic waves are critical factors in ensuring the safety of the cavern. The SF of the cavern’s lower structure is more sensitive to changes in seismic parameters than that of the other locations, which makes the cavern bottom more likely to be destroyed during an earthquake. Therefore, the lower structure should be the study target in the seismic design for a salt cavern gas storage facility. Results have been used in the seismic design of salt cavern gas storage facilities in China.

Static and Dynamic Stability Analysis on Artificial Rock Mass Slope Using Strength Reduction Method

This paper focuses on stability analysis of an artificial rock mass slope by a nonlinear finite element method (FEM). For a long time, rock slope stability problem is always an important research issue in the field of geotechnical engineering, which is related to human life and property safety as well as engineering security and efficiency. Therefore, the stability analysis and evaluation on rock slope is of great significance. The static and dynamic stability analysis on the artificial rock mass slope of WuAn power plant in China is carried on respectively in this paper by using the strength reduction method and FLAC3D software. In this analysis, static and dynamic instability criterions are enumerated, and the static and dynamic safety factors are calculated with the developed criterions of the displacement mutation, respectively. The analysis results show that the artificial rock mass slope is basically stable. It indicates that analyzing slope stability with strength reduction method is feasible.

Subsidence risk assessment of decommissioned bord-and-pillar collieries

Underground mining of coal results in voids with remanent pillars to support the overlying strata. Failure of any individual pillar overloads adjacent pillars and may result in failure propagation with damaging surface subsidence. It has been shown that coal pillar strength can be estimated from the attributes of effective width and height, however the risk for pillar panel failure resulting in surface subsidence cannot be estimated by consideration of individual pillars in isolation. In this paper we show the calculation of a panel failure probability density function from a statistical distribution of the pillar geometrical attributes reflecting mine design uncertainties and environmental degradation with time. We first calculate the static then dynamic safety factors. In a piece-wise fashion over the surface area we estimate the probabilities that 80% of pillars in a circular area of diameter equal to the cover depth have a safety factor less than 1.6. These probabilities then form the risk matrix likelihood and estimated surface tilts form the consequence in a thematic surface map of risk. In studies of an urban residential site experiencing multiple incidences of mine induced surface subsidence we demonstrate the methodology and show that when every pillar, numbering more than 1100, is evaluated for stability and the interaction between these pillars is considered, then both the location of observed failures and the resultant measured surface tilts are predictable. Based on this assessment, geotechnical monitoring by a seismic array, extensometers and piezometers of a mine panel identified as at risk is currently being undertaken while remediation options are evaluated.