Dynamic Safety Factor Research Articles

An energy-based criterion for defining slope failure considering the coupling effect of groundwater table and impact loading

Slope instability poses significant risks in tunnel construction, particularly under the influence of impact loading and fluctuations in groundwater table. This study addresses the complexity of energy transformation and distribution in slopes affected by these factors. The research aims to analyze the local dynamic Factor of Safety (FOS) from the perspective of energy-based criterion, considering groundwater table, impact loading, and load position. Key findings indicate that the groundwater table is the most influential factor on slope stability, followed by load position and impact loading. The overall dynamic FOS was observed to peak at 0.35 s and trough appears at 1.0 s during impact loading, stabilizing after 2 s. The evolution of the overall dynamic FOS is explained from the energy dissipation and transformation mechanisms. These insights provide a critical basis for risk assessment and prevention in complex slope scenarios, contributing to sustainable infrastructure development in line with UN SDG 11 (Sustainable Cities and Communities).

Research on the Design of Multi-Rope Friction Hoisting System of Vertical Shaft Gravity Energy Storage System

Renewable energy generation methods such as wind power and photovoltaic power have problems of randomness, intermittency, and volatility. Gravity energy storage technology can realize the stable and controllable conversion of gravity potential energy and electric energy by lifting and lowering heavy loads. The hoisting system is an important component of a gravity energy storage system, and its lifting capacity and speed seriously restrict its energy storage capacity, energy conversion efficiency, and operational safety and reliability. In this paper, a design method for a multi-rope friction hoisting system of a vertical shaft gravity energy storage system is proposed. The parameter design and calculation of the hoisting rope, balance rope, and friction wheel of the friction hoisting system under typical conditions were carried out. The static and dynamic anti-slip capabilities of the friction hoisting system under the typical condition were explored. The results show that the maximum acceleration and deceleration speed of the compacted strand wire rope scheme is the largest, and the lifting and lowering time is the shortest. The maximum acceleration and deceleration speed of the triangular strand wire rope scheme is the lowest, and the lifting and lowering time is the longest. The dynamic tension of the hoisting rope at the heavy-load end is positively correlated with the acceleration, and the maximum value occurs in the accelerated lifting stage and decelerated lowering stage of the heavy load. The static anti-slip safety factor between the hoisting rope and the friction lining and the specific pressure between the hoisting rope and the friction lining comply with the requirements of China’s Safety Regulations for Coal Mines. The dynamic anti-slip safety factor of the hoisting system under different rope selection schemes is greater than the minimum value of 1.25 stipulated in the Safety Regulations for Metal and Nonmetal Mines. The research results are of great significance for the safety, reliability, and stable and efficient energy storage of a gravity energy storage system.

Seismic Stability Study of Bedding Slope Based on a Pseudo-Dynamic Method and Its Numerical Validation

Earthquakes are one of the main causes of bedding slope instability, and scientifically and quantitively evaluating seismic stability is of great significance for preventing landslide disasters. This study aims to assess the bedding slope stability under seismic loading and the influences of various parameters on stability using a pseudo-dynamic method. Based on the limit equilibrium theory, a general solution for the dynamic safety factor of bedding slope is proposed. The effects of parameters such as slope height, slope angle, cohesion, internal friction angle, vibration time, shear wave velocity, seismic acceleration coefficient, and amplification factor on stability are discussed in detail. To evaluate the validity of the pseudo-dynamic solution, the safety factors are compared with those given by early cases, and the results show that the safety factors calculated by the present formulation coincide better with those of previous methods. Moreover, a two-dimensional numerical solution of bedding slope based on Mohr–Coulomb’s elastic–plastic failure criterion is also performed by using the finite element procedure, and the minimum safety factor is essentially consistent with the result of the pseudo-dynamic method. It is proved that the pseudo-dynamic method is effective for bedding slope stability analyses during earthquakes, and it can overcome the limitations of the pseudo-static method.

Dynamic factor of safety of rock slopes due to blasting based on critical displacement and critical acceleration

Analysis of slope stability due to blasting based on the pseudostatic principle is considered too conservative because the slope receives a constant maximum seismic load (and hence constant acceleration) without considering the duration of the blast. In reality, the acceleration fluctuates with time and eventually diminishes. One method to analyze the stability of rock slopes due to blasting is to conduct dynamic simulations using Newmark displacement analysis to obtain the dynamic Factor of Safety (FoS) based on the magnitude of critical displacement (ucrit ) and critical acceleration (acrit ). This study was carried out using hypothetical slopes of various rock mass strengths determined from the Rock Mass Rating (RMR). A case study of a highway rock slope excavated using the drill-and-blast method was also carried out to validate the research results. The findings reveal that very good rock (RMR Class I) has FoSdynamic = 11.7, ucrit = 6 mm, and acrit = 0.061g, while very poor rock (RMR V) has FoSdynamic = 1.7, ucrit = 16 mm, and acrit = 0.035g. This result indicates that the smaller the strength of the rock mass, the smaller the critical acceleration and the greater the value of the critical displacement will be. This study reinforces the significance of critical displacement and critical acceleration in assessing the dynamic stability of rock slopes due to blasting.

Evaluation of performance and storey drift ratio limits of high-rise structural systems with separated gravity and lateral load resisting systems using time history analysis and incremental dynamic analysis

To increase the efficiency of prefabricated construction of high-rise structure, a composite structural system with separated gravity and lateral load resisting systems (referred to as a ‘new separable system’) is proposed. Efficient numerical models of the composite frames, reinforced-concrete (RC) shear walls, RC coupling beams, and braces in the new separable system were developed using the finite-element program MSC.Marc. The fragility curves of these components were developed through parametric analysis and a literature review of previous research and database documents. Through time history analysis, the responses of roof displacement, storey drift, and residual drift were analysed and compared with those of the traditional composite frame–shear wall system. An incremental dynamic analysis (IDA) was performed to obtain the IDA curves of the new separable system and the traditional system, and the seismic fragility curves of the two systems were built. The seismic performance of the new separable system was compared with that of the traditional system in terms of the collapse probability, dynamic safety factor, and risk of seismic damage. The results indicated that for high-rise composite structural systems with separated gravity and lateral resisting systems under frequently occurring earthquakes, the reasonable range of the storey drift ratio limit in design is 1/800 to 1/1000, and a limit value of 1/1000 is recommended conservatively.

Dynamic stability assessment of consequent rock slopes considering multiple transmissions and reflections of stress waves

In this work, Based on the conservation of momentum at the wave fronts and the displacement discontinuity method, a theoretical approach for calculating the dynamic safety factor of consequent rock slopes is proposed. The multiple transmissions and reflections of stress waves on the joints and free surfaces are taken into account. A comparison of UDEC simulation and theoretical calculation was carried out to verify the feasibility of the proposed method. Moreover, parametric studies were conducted to investigate the effects of free surfaces, joint stiffness, amplitude of incident waves, and frequency of incident waves. The results show that the proposed method can predict the time history curve of the safety factor of a slope readily and accurately. Waves reflected from both the slope and top surfaces are found to have a significant effect on the stability of the slope – considering them or not can cause a difference in the safety factors up to 32.5%. The greater the joint stiffness is, the greater the safety factor fluctuates with time. However, when the joint stiffness is sufficiently high, the effect of joint stiffness on the safety factor can be neglected. The approach proposed in this work provides a theoretical tool for the dynamic assessment and design of consequent rock slopes. Highlights An analytical method is proposed for calculating the dynamic safety factor of rock slopes. Multiple transmissions and reflections of stress waves are considered. The proposed method has high calculation accuracy and can be applied in practice.

Dynamic stability analysis of jointed rock slopes using the combined finite-discrete element method (FDEM)

The combined finite-discrete element method (FDEM) is an advanced finite element and discrete element coupling method, which is commendably suitable for simulating the slope’s entire evolution process from cracking, expansion, penetration, sliding, collision to deposition under seismic load. The original FDEM has apparent shortcomings in simulating the dynamic instability process of earthquake-induced landslides, and some targeted improvements are made to the original program. Numerical tests are carried out to prove the accuracy and robustness of the improved FDEM, and the influence of the structural plane on the dynamic evolution mechanism and process of the slope is studied. The results show that the improved FDEM can accurately reproduce the entire dynamic evolution processes and failure forms of different jointed rock slopes under seismic load and can quantitatively evaluate the dynamic stability of jointed rock slopes (dynamic safety factor and critical failure surface). In addition, the results also emphasize that the slope failure degree significantly affects the dynamic response of the slope and suggest that the combination of the cut-through of the failure surface and the increase of kinetic energy should be used as the criteria for slope dynamic instability simulation by FDEM. This study provides scientific and technological support for revealing the failure mechanism of jointed rock slopes and disaster reduction and prevention.

ANALISIS SIMULASI KEKUATAN DAN PEMBUATAN RANGKA KENDARAAN SEPEDA MOTOR LISTRIK

The development of the automotive industry, especially my vehicle transportation, has changed from a fuel motor to an electric motor vehicle. The purpose of writing is to get results from the simulation of frame design and power on an electric motorcycle. The simulation result from the design where the material used is low carbon steel that the frame of an electric motorcycle with a rider weight of 170 kg is safe based on the "machine element" book on the dynamic load safety factor, which is determined from 2.0-3.0 For static loads 1.25-2.0 and shocks 3-5 this frame construction includes dynamic loads, displacement resulting from the stress analysis of the electric motorcycle frame receiving a load of 1700 N which is assumed to be the weight of the rider. Based on the simulation results, the maximum displacement is 0.2118 mm, and the von Mises stress generated by the stress analysis of the electric motorcycle frame receives a load of 1700 N, which is assumed to be the weight of the rider. Based on the simulation results, the maximum von Mises is 101.3 MPa. The von mises voltage. This electric motorcycle uses a 48 V BLDC brushless motor, 1500 W, 550 rpm, and uses a 58 V and 24 Ah lithium-ion battery.

Stiffness as a criterion of dynamic load carrying capacity of tension-loaded bolted joints

The influence of the bolt size and the width of the joint members/bolt diameter ratio (relative clamped length) on the stiffness coefficient of the bolt and joint members, as well as on the ratio of these stiffness coefficients are discussed in this paper. The individual stiffness coefficients of the bolt and the joint members decrease with the increase of the relative clamped length and the decrease of the bolt size. However, the stiffness ratio of the joint members and the bolt increases with the increase of the relative clamped length. Of the considered bolts M6 ... M24, the bolted joint with the M6 bolt has the highest stiffness ratio of the joint members and the bolt, and the bolted joint with the M12 bolt has the lowest stiffness ratio. When a bolted joint is loaded with a variable working load, then the dynamic safety factor (DSF) is used for evaluating the joint load capacity. The DSF increases with a decrease in the stiffness of the bolted joint, i.e. by increasing the relative clamped length of the bolted joint. For the same conditions analyzed, the bolted joint with M6 bolt has the largest DSF, and the bolted joint with M12 bolt has the smallest DSF. The obtained result can be used by engineers to evaluate the load-carrying capacity of dynamically tension-loaded bolted joints.

Parametric study of the earth dam's behaviour subjected to earthquake

Abstract Static stability of an earth dam can be established by estimating the static safety factor equal to the ratio of the shear strength to the shear stress along a critical sliding area. In contrast, it is more complicated to evaluate the dynamic stability during an earthquake. The water filling the interstices of the earth dams cannot drain during the short duration of an earthquake. An excess pore water pressure ΔU develops, and its role is predominant in the destabilisation of the dam. The pore water increase causes a decrease in the soil shear strength. It is, therefore, crucial to evaluate and take into consideration ΔU in the dam dynamic stability analysis. This research is a contribution to reach this objective. A parametric study was conducted by varying the physical and mechanical soil characteristics constituting the dam, as well as its geometrical values, in order to evaluate their effects on the dynamic safety factor. The dynamic safety factor is calculated using the pseudo-static method, taking into account the excess pore water pressure that develops during cyclic loading into the granular soil of the earth dam upstream face. The results of the parametrical analytical study were also compared to the results of numerical simulations of the dam seismic stability trough pseudo-static method. The numerical simulations were done with three different software: PLAXIS and ABAQUS (based on the finite element method) and GEOSTAB (deals with the problem at the limit equilibrium using the simplified Bishop method). At the end, on one hand, we were able to describe how and at what level of the dam upstream face the sliding occurs, and on the other hand, we were able to underline the adequate combination between the dam geometric parameters and the mechanical soil characteristics which may ensure seismic stability.

SEISMIC DESIGN OF EMBANKMENTS - NUMERICAL AND ANALYTICAL STUDY

In this paper, a dynamic shear strength analysis was performed in a finite elements environment to evaluate the stability of embankments under seismic loadings. In addition, a dynamic factor of safety depending on the results of the numerical analysis was defined. To study these parameters' effects on the embankment's stability, a parametric study concerning the embankment inclination and the soil type was performed. Finally, the numerical analysis results were compared with the results of the pseudo-static analysis according to the EC8. The results of this study show the significance of the numerical seismic analyses in comparison with the analytical calculations.

Characteristics of Dynamic Safety Factors during the Construction Process for a Tunnel-Group Metro Station

Dynamic safety factors during the construction of an overlapping tunnel-group metro station were studied in the framework of the strength-reduction finite element method. Based on the equivalent plastic strain and displacement of surrounding rock, its damage mode under typical excavation conditions was investigated. The aim of this investigation was to provide information for the design activities concerning the supporting system of the station and the pre-reinforcement of its surrounding ground. The accuracy of the model was assessed by comparing the ground settlements obtained from on-site monitoring with those from the numerical model. The analysis results show that the safety factor reaches the minimum when the No. 3 guide hole of the station hall is excavated. Thus, this is the most dangerous construction step. During this step, the plastic zone penetration phenomenon occurs in the surrounding rock, which is sandwiched between the hall and the platform of the station. In this case, both the deformation of the surrounding rock and the internal forces of the lining increase. The surrounding rock in the sidewall loses its stability. Thereafter, the primary support plays a role of stabilizing the guide hole.

Three-dimensional rigorous upper-bound limit analysis of soil slopes subjected to variable seismic excitations

In the present study, a semi-analytical model that couples the three-dimensional (3D) kinematical approach of limit analysis and the modified pseudo-dynamic method was developed. The model was used to assess the critical safety factor of slopes from a realistic and wholistic perspective. Time-space dependent sinusoidal-cosinusoidal waves were introduced to represent cyclic effects of seismic waves, and the shaking amplitude and damping effect were incorporated. A 3D discretized failure mechanism comprising a series of kinematically admissible triangle meshes was generated. This failure mechanism is superior compared with conventional mechanisms as the normality condition required by the plastic theorem is fully met and variable seismic excitations can be directly incorporated. The work-rate of the external forces and the internal dissipation rates were numerically acquired to explicitly determine critical safety factors. Accuracy of the proposed model was determined through numerical simulations and dynamic safety factors and plastic zones were compared. Comparisons and parametric analyses showed the importance of accounting for the third dimension of slopes, damping ratios, the relationship between shaking frequency and natural frequency. Testing of proposed model was performed through seismic stability analysis of the Longnan slope located in an earthquake-prone zone.

Analytical Computation of Sandy Slope Stability under the Groundwater Seepage and Earthquake Conditions

Groundwater and earthquake are two of the factors behind the occurrence of slope instability. This paper focuses on the computation of the safety factor acting on a sandy slope when subjected to groundwater seepage and earthquake load. Based on the theory of limit equilibrium and a pseudodynamic method of analysis, a general solution for the dynamic factor of sandy slope containing two load conditions is proposed. In the solution, the effects of parameters such as water level, seismic acceleration coefficients, slope angle, and soil internal friction angle on the slope stability have been discussed. In order to evaluate the validity of the present formulation, the dynamic factors of safety computed by the present method are compared with those given by other cases. It is found that the results of the present method are in good agreement with those of the previous method. The results indicate that the dynamic of safety factor increases linearly with an increase in the soil internal friction angle but decreases with the slope angle and groundwater level and that the effects of direction and magnitude of the seismic inertia forces on the dynamic safety factor of sandy slope are different at different times.

Structural Design and Strength Analysis of Lifting Machine for Home Appliance Flood Safety Tool: A Problem-based Learning

In Indonesia, floods become an annual disaster, especially in the rainy season. The number of floods occurs in Indonesia in 2019 reached 1,277 cases. The floodwater can cause massive damage to the home appliance, especially when contacted with electronic devices. Moreover, the lifting machine comes as an excellent solution, securing the electronic device when floods come. A preliminary design of a hydraulic scissors lifter for elevating the home appliance during floods is introduced along with its static and fatigue strength analyses. The proposed design comes up with a combination of scissors lifter mechanism combined with the hydraulic jack device. The analyses in the critical components of the lifting machine - the support link and the scissors rod link - are presented. The lowest and upper conditions are assumed and resulted in a dynamic safety factor of 1.252 for the lowest position and 3.11 for the highest position. These values indicate that the proposed design offers excellent safety. Additionally, this work can be classified as teaching material for the machine element course.

ANALISIS KESTABILAN LERENG HIGHWALL MENGGUNAKAN METODE BISHOP SIMPLIFIED PADA PIT 13 PT BELAYAN INTERNASIONAL COAL KECAMATAN MARANGKAYU KABUPATEN KUTAI KARTANEGARA

PT Belayan Internasional Coal is an open-pit system mining company, one of its geotechnical activities is the construction of the slopes. Slope stability analysis used the Bishop Simplified method to obtain the value of the dynamic safety factor (≥ 1,1). Currently, the value of the Safety Factor (FK) is an indicator in determining whether the slope is stable or not. The parameters used in the slope stability analysis are the physical and mechanical properties of the rock, namely weight (ɣ), cohesion value (c), and internal shear angle (∅). From the results of dynamic overall slope calculations, the recommended overall slope is constructed with an individual slope angle of 55°, a bench width of 5 meters, a height of 10 meters, and the number of individual slopes of 8 slopes. This design will produce dimensions of the overall slope with 41° slope angle, 80 meters high, and has a dynamic safety factor value of 1,102 with the water-saturated condition. Thus, the slopes are in stable condition.

Extensions of the dynamic Newmark method for seismic stability analysis of a rock block

AbstractThe Newmark sliding block method combined with block theory (referred to as the dynamic Newmark method) can be used to calculate the dynamic safety factor and the permanent displacement, which provides a quantitative tool to evaluate the dynamic stability of a rock block under seismic action. Frequent changes in the position of a rock block under seismic action may lead to the changes in contact areas and modes of contact between sliding faces. These problems that are not considered in the original dynamic Newmark method are solved to extend the dynamic Newmark method. First, the loop analysis method is introduced to obtain the contact polygonal faces of a sliding surface, and the simplex integration method is used to calculate the contact areas. Second, the reference point method is defined to identify the mode of contact between a structural plane and the surrounding rock mass, and the possible mode of motion of the rock block is determined. Based on these extensions of the dynamic Newmark method, an Extended Newmark Method (ENM) program is developed, and a verification example, three comparison cases, and an application are used to validate the correctness and effectiveness of the extended method. The results show that the ENM program can be used to calculate the effects of the change in contact areas and modes of contact on block motion, which better reflects the dynamic response of a rock block under seismic action compared with the original dynamic Newmark method.

Kombinasi Metode Kontrol dan Perkuatan untuk Penanganan Longsor (Studi Kasus: Longsor Waikerap, Tanggamus, Lampung)

Landslides often cause heavy casualties and material losses in Tanggamus Regency. These incidentscontinue to be repeated so that it still requires a landslides risk reduction. Landslides risk mitigation begins with a field survey and soil investigation, followed by analyzing the investigation results and planning the potential mass movements. The results from the geological survey show that the study area has a lithology of constituents in the form of andesite and landslide material in the form of volcanic breaks with a high level of weathering so as to form a thick layer of soil. The basic landslide handling design plan in Pekon Waykerap is to perform the geometry arrangement of the slopes so itprovides a strengthened structure with gabion slopes. The slope design results give the slope height limited to 5 meters, a 1H:1V slope gradient, and 2.5 meter bench. The slope surface is suggested to be covered with a patch of grass and equipped with surface drainage. The slope stability analysis results for Pekon Waykerap landslides using the limit equilibrium method shows that using the combination of control and retrofitting method and increases the static safety factor from 1.092 to 1.298 and the dynamic safety factor from 0.846 to 1.031, which means the groundmass movement risk decreases.

Safety performance of self-expandable NiTi alloy stent

In order to evaluate the safety performance of self-expandable NiTi alloy stents systematically, the dynamic safety factor drawn up by International Organization for Standardization, was used to quantitatively reflect the safety performance of stents. Based on the constitutive model of super-elastic memory alloy material in Abaqus and uniaxial tensile test data of NiTi alloy tube, finite element method and experiments on accelerated fatigue life were carried out to simulate the self-expansion process and the shape change process under the action of high and low blood pressure for three L-type stents of Φ8×30 mm, Φ10×30 mm, Φ12×30 mm. By analyzing the changes of stress and strain of self-expanding NiTi alloy stent, the maximum stress and strain, stress concentration position, fatigue strength and possible failure modes were studied, thus the dynamic safety factor of stent was calculated. The results showed that the maximum stress and plastic strain of the stent increased with the increase of grip pressure, but the maximum stress and strain distribution area of the stent had no significant change, which were all concentrated in the inner arc between the support and the connector. The dynamic safety factors of the three stents were 1.31, 1.23 and 1.14, respectively, which indicates that the three stents have better safety and reliability, and can meet the fatigue life requirements of more than 10 years, and safety performance of the three stents decreases with the increase of stent's original diameter.

Seismic fragility functions for slope stability analysis with multiple vulnerability states

The seismic performance and stability analysis of slopes are important in predicating damage and mitigating potential losses in landslide-prone areas. Fragility functions can give results of slope performance assessment that are more comprehensive and richer. This study presents a procedure of constructing seismic fragility functions for slope stability analysis with various vulnerability states based on incremental dynamic analysis (IDA). IDA is a performance-based earthquake engineering analysis based on a series of dynamic time history analyses conducted for suitable multiple-scaled seismic records. IDA not only estimates the seismic demand and capacity of systems but also provides basic data for the estimation of fragility functions. Firstly, an ensemble of seismic records meeting the requirements of specific site conditions of a slope is selected to consider the randomness of ground motion. A series of seismic stability analyses of the slope are performed to obtain the dynamic safety factor time history of the slope. Each minimum safety factor and corresponding seismic intensity measure is then extracted to develop a set of IDA curves. On the basis of IDA results, analytical seismic fragility functions of a slope are developed considering the prescribed various vulnerability states of the slope in terms of the safety factor. The failure probabilities of exceeding different specific vulnerability states for a given intensity measure of the earthquake are finally obtained.