scholarly journals Upper Bound Analysis of the Stability of 3D Slopes in the Saturated Soft Clay Subjected to Seismic Effect

2021 ◽  
Vol 9 ◽  
Author(s):  
Biao Zhang ◽  
Yi Jiang ◽  
Hao Cheng ◽  
Ze Liu
Keyword(s):  
Upper Bound ◽  
Soft Clay ◽  
Slope Angle ◽  
Three Dimensional ◽  
Stability Coefficient ◽  
Seismic Force ◽  
The Stability ◽  
Seismic Forces ◽  
Saturated Soft Clay ◽  
Clay Slopes

In order to study the three-dimensional stability problem of the saturated soft clay slope under earthquake loads, based on the three-dimensional rotation failure model, the seismic force was introduced into the calculation by the quasi-static method. The work rate of external loads and the internal energy dissipation rate of the saturated soft clay slope were calculated using the upper bound method of limit analysis, and the analytical solution of stability coefficient of saturated soft clay slopes was derived based on the fictitious power principle. By virtue of the exhaust algorithm, the optimal solution of stability coefficient of saturated soft clay slopes was obtained. The influence of the slope angle and the horizontal and vertical seismic forces on the stability coefficient of saturated soft clay slope was analyzed. The results show that the slope angle has a great influence on the stability coefficient, and the relative difference is up to 35.7%. Therefore, the stability coefficient of saturated soft clay slopes can be effectively increased by a proper slope setting. The horizontal and vertical seismic forces also have a significant influence on the stability of saturated soft clay slopes. The relative differences of the stability coefficient under horizontal and vertical seismic forces are as high as 41 and 14.7%, respectively. If they are ignored, the stability coefficient of saturated soft clay slopes will be seriously overestimated. It is suggested that the effects of horizontal and vertical seismic forces must be considered simultaneously in the seismic design of saturated soft clay slopes.

Seismic stability of a long unlined circular tunnel in sloping ground

2016 ◽  
Vol 53 (8) ◽  
pp. 1346-1352 ◽  
Author(s):  
Sounik Kumar Banerjee ◽  
Debarghya Chakraborty
Keyword(s):  
Finite Element ◽  
Lower Bound ◽  
Plastic Zone ◽  
Slope Angle ◽  
Seismic Stability ◽  
Circular Tunnel ◽  
Infinite Slope ◽  
Sloping Ground ◽  
The Stability ◽  
Seismic Forces

The stability of an unlined long circular tunnel underneath an infinite slope is examined with the inclusion of seismic body forces. The study is carried out by using the lower bound finite element limit analysis. The values of γH/c are plotted as a function of H/D, [Formula: see text], β, and kh in the form of charts. The magnitude of γH/c is found to decrease consistently with an increase in β and kh. With an increase in the magnitude of β and kh, the plastic zone around the periphery of the tunnel becomes more and more asymmetric. The stability charts presented in this note would be useful for examining the effect of slope angle on the stability of an unsupported circular tunnel under seismic forces.

scholarly journals Investigation on the Stability of Fissured Slopes Reinforced with Anchor Cables under Seismic Action

2021 ◽  
Vol 2021 ◽  
pp. 1-14
Author(s):  
Jingwu Zhang ◽  
Mingdong Li ◽  
Jinxiang Yi ◽  
Zhidan Liu
Keyword(s):  
Axial Force ◽  
Upper Bound ◽  
Crack Depth ◽  
Slope Angle ◽  
Optimization Procedure ◽  
Seismic Action ◽  
Upper Bound Theorem ◽  
Critical Location ◽  
The Stability ◽  
The Impact

Based on the upper bound theorem of limit analysis (UBLA) combined with the pseudostatic methods, this paper elaborates on a calculated procedure for evaluating fissured slope stability under seismic conditions reinforced with prestressed anchor cables. An existing simple slope case is presented as a case study in this work. The comparison is given to verify that the solution derived from this study is correct and feasible. By means of a numerical optimization procedure, the critical location of the crack is determined from the best upper bound solutions. The results demonstrate a significant influence of the depth of crack and seismic acceleration coefficient on the critical location distribution of the cracks. Meanwhile, the axial force of anchor cables is investigated via parametric studies. It is shown that the variation of the crack depth has little effect on the axial force of anchor cables. Moreover, this paper also illustrates the variation in the axial force of anchor cables under the impact of five marked factors (crack depth, anchor arrangement, anchor inclination angle, slope angle, and seismic conditions). Finally, the required critical length of the free section of anchor cables is determined to ensure the stability of fissured slopes subjected to seismic action.

scholarly journals Influence of Both Soil Properties and Geometric Parameters on Failure Mechanisms and Stability of Two-Layer Undrained Slopes

2020 ◽  
Vol 2020 ◽  
pp. 1-13
Author(s):  
Shuangfeng Guo ◽  
Ning Li ◽  
Wenpeng Liu ◽  
Zongyuan Ma ◽  
Naifei Liu ◽  
...  
Keyword(s):  
Finite Element Method ◽  
Failure Mechanism ◽  
Failure Mechanisms ◽  
Slope Angle ◽  
Strength Parameter ◽  
Strength Ratio ◽  
Stability Number ◽  
Parametric Studies ◽  
The Stability ◽  
Clay Slopes

The stability of the two-layer undrained clay slopes should be given considerable attention since they are commonly observed in nature and in manmade structures, and they traditionally have low stability. Therefore, with the elastoplastic finite element method, this paper thoroughly explores the influence of the soil strength parameter cu, slope angle β, and slope depth ratio DH on the slope stability and failure mechanisms by the wide-ranging parametric changes. The aims of this study are also to find the critical strength ratio (cu2/cu1)crit and the maximum values of the stability number Nc that were observed in the parametric studies. Numerical results are displayed in the form of charts to give Nc and (cu2/cu1)crit as a function of cu, β, and DH. Moreover, influences of DH and β on Nc and failure mechanisms are examined in this study. The results of numerical analysis demonstrate that cu2/cu1 significantly affects both the critical failure mechanism and the stability of the two-layer undrained slope. Improved knowledge of the location of the critical failure mechanism allows for accurately estimating the stability of the two-layer undrained slopes for future strengthening measurements to preserve stability.

Coupled Numerical Analysis of Tunnel Excavation in Saturated Soft Clay under High Groundwater

2011 ◽  
Vol 368-373 ◽  
pp. 2533-2536
Author(s):  
Hua Yuan ◽  
Hai Tao Wan ◽  
Zhi Liang Zhao
Keyword(s):  
Soft Clay ◽  
Three Dimensional ◽  
Bending Moment ◽  
High Water ◽  
Shield Tunnel ◽  
Deep Soil ◽  
Tunnel Excavation ◽  
Axial Forces ◽  
Reduction Effect ◽  
Saturated Soft Clay

A coupled numerical simulation of a river-crossing shield tunnel excavation in saturated soft clay with high groundwater has been performed using a three-dimensional finite difference model, which takes into account variation of soil permeability with stress, anisotropy of permeability, reduction effect of joints on segment bending stiffness and the hardening process of synchronized grouting material. Groundwater seepage conditions around the tunnel, bending moment, axial forces and strength safety factor of tunnel segment as well as deep soil displacement during tunnel diving are investigated numerically. The analyses provide valuable information concerning the mechanical behavior of tunnel segment and hydrological field in soil around tunnel during advancing. The result also is benefited to control groundwater for river-crossing tunnel in soft clay under high water table.

scholarly journals Settlement simulation of soft clay in the subway under dynamic load based on Midas GTS NX

2021 ◽  
Vol 237 ◽  
pp. 03011
Author(s):  
Quan Cao ◽  
Yu Hang
Keyword(s):  
Finite Element ◽  
Dynamic Load ◽  
High Speed ◽  
Large Population ◽  
Soft Clay ◽  
Three Dimensional ◽  
Element Model ◽  
Structural Safety ◽  
Finite Element Software ◽  
Saturated Soft Clay

The subway has become the main way for people to travel nowadays. The saturated soft clay area has a large population and subway construction is the most extensively distributed. The saturated soft clay foundation will settle under the dynamic load of the subway train, which will affect the service life and structural safety. To study the settlement characteristics of soft clay under the dynamic load of the subway, a three-dimensional dynamic finite element model was established based on the finite element software Midas GTS NX, and the soft clay under the normal design speed (80 km/h) and the high-speed (120 km/h) were compared and analyzed. The research results show that the higher the train speed, the larger the lateral influence range of the surface settlement trough, but the settlement decreases with the increase of the subway running speed. The settlement of the subway line after one year of operation is about 45mm, and the settlement after 20 years is about 58mm. The growth rate of the settlement prediction curve decreases gradually, and the settlement increment is very small for a long time in the later period of operation.

Research on Mechanism of Consolidating the Saturated Soft Clay with the Application of Pile-Supported Composite Foundation

2012 ◽  
Vol 594-597 ◽  
pp. 370-375
Author(s):  
Zhao Hua Zhang
Keyword(s):  
Pore Water Pressure ◽  
Water Pressure ◽  
Soft Soil ◽  
Soft Clay ◽  
Drainage System ◽  
Single Layer ◽  
Composite Foundation ◽  
Critical Height ◽  
The Stability ◽  
Saturated Soft Clay

In order to reduce both uneven settlements and construction duration, researches on pile-supported composite foundation of highway were carried out. When the groundfill is higher than the critical height（1.35 times space between piles）, a complete geostatic arch is formed in the pile-supported composite foundation, which could significantly reduce the uneven settlement. Grids installed at the bottom of embankment could markedly reduce the side displacement and increase the stability of embankment, multilayer grids with layout of loose on the top and dense at the bottom prefer to single layer grids. Plastic drainage board makes up well-functioned drainage system, which can shorten the dispersal time of pore water pressure and accelerate the consolidation of soft soil to shorten the construction duration.

scholarly journals 3D Limit Analysis of the Transient Stability of Slope during Pile Driving in Nonhomogeneous and Anisotropic Soil

2020 ◽  
Vol 2020 ◽  
pp. 1-10
Author(s):  
Pingping Rao ◽  
Jian Wu ◽  
Zhihao Mo
Keyword(s):  
Upper Bound ◽  
Limit Analysis ◽  
Transient Stability ◽  
Three Dimensional ◽  
Optimization Method ◽  
Pile Driving ◽  
Failure Patterns ◽  
Anisotropic Soil ◽  
The Stability ◽  
Rotational Failure

To evaluate the stability of a slope subjected to pile driving in nonhomogeneous and anisotropic soils, an upper-bound limit analysis method is employed in this paper. A 3D rotational failure mechanism for soil slope is extended to account for different failure patterns (i.e., toe failure and base failure). In order to avoid missing the global minimum, an efficient optimization method is simultaneously employed to find the least upper bound to the factor of safety (FS). The effectiveness and accuracy of the proposed method is well demonstrated by comparing the results obtained from the proposed approach with the solutions from published literatures. The effects of key designing parameters are presented and discussed. The optimal pile location and the three-dimensional effect of the slope are discussed. In addition, these results highlight that the adverse effects of pile driving on slope stability should be highly concerned during the design of geotechnical infrastructures, rather than emphasizing the reinforcement effect of a pile only.

Horizontal drains to stabilize clay slopes

1984 ◽  
Vol 21 (2) ◽  
pp. 241-249 ◽  
Author(s):  
K. C. Lau ◽  
T. C. Kenney
Keyword(s):  
Three Dimensional ◽  
Test Theory ◽  
Two Dimensional ◽  
Natural Clay ◽  
Piezometric Head ◽  
Horizontal Drains ◽  
The Stability ◽  
Clay Slopes ◽  
Viable Method ◽  
Piezometric Heads

Five horizontal drains were installed in a natural clay slope and the piezometric heads in the slope were monitored with piezometers. Decreases of piezometric head in the vicinity of the drains were measured and indicated that horizontal drains can be used to improve the stability of clay slopes.Based on the theory of consolidation, estimates were made of the changes of piezometric head within the test slope due to the installation of drains. Good comparisons were obtained between the predicted and the measured values, demonstrating that the method of prediction can be used with confidence for design purposes. The three-dimensional pattern of piezometric levels was averaged to give an equivalent two-dimensional pattern, and this was used in slope stability calculations to determine the improvement in safety factor of the slope.The effectiveness of horizontal drains depends on the spacing and diameter of the drains, and on their location relative to the critical slip zone.The study has shown that installation of horizontal drains is a viable method of improving the stability of certain clay slopes. Keywords: slope, clay, stability, drains, field test, theory.

Low-Degree Tibial Slope Angle Prevents Component Overhang by Enlarging the Lateral Plateau Surface Area in Total Knee Arthroplasty

2020 ◽  
Author(s):  
Mehmet Emin Simsek ◽  
Mustafa Akkaya ◽  
Safa Gursoy ◽  
Özgür Kaya ◽  
Murat Bozkurt
Keyword(s):  
Total Knee Arthroplasty ◽  
Surface Area ◽  
Knee Arthroplasty ◽  
Tibial Plateau ◽  
Slope Angle ◽  
Three Dimensional ◽  
Tibial Slope ◽  
Total Knee ◽  
Lateral Plateau ◽  
Gender Groups

AbstractThis study aimed to investigate whether overhang or underhang around the tibial component that occurs during the placement of tibial baseplates was affected by different slope angles of the tibial plateau and determine the changes in the lateral and medial plateau diameters while changing the slope angle in total knee arthroplasty. Three-dimensional tibia models were reconstructed using the computed tomography scans of 120 tibial dry bones. Tibial plateau slope cuts were performed with 9, 7, 5, 3, and 0 degrees of slope angles 2-mm below the subchondral bone in the deepest point of the medial plateau. Total, lateral, and medial tibial plateau areas and overhang/underhang rates were measured at each cut level. Digital implantations of the asymmetric and symmetric tibial baseplates were made on the tibial plateau with each slope angles. Following the implantations, the slope angle that prevents overhang or underhang at the bone border and the slope angle that has more surface area was identified. A significant increase was noted in the total tibial surface area, lateral plateau surface area, and lateral anteroposterior distance, whereas the slope cut angles were changed from 9 to 0 degrees in both gender groups. It was found that the amount of posteromedial underhang and posterolateral overhang increased in both the asymmetric and symmetric tibial baseplates when the slope angle was changed from 0 to 9 degrees. Although the mediolateral diameter did not change after the proximal tibia cuts at different slope angles, the surface area and anteroposterior diameter of the lateral plateau could change, leading to increased lateral plateau area. Although prosthesis designs are highly compatible with the tibial surface area, it should be noted that the component overhangs, especially beyond the posterolateral edge, it can be prevented by changing the slope cut angle in males and females.

A Liquid Metal Flow Between Two Coaxial Cylinders System

2019 ◽  
Vol 11 (1) ◽  
pp. 79-86
Author(s):  
Abdelkrim Merah ◽  
Ridha Kelaiaia ◽  
Faiza Mokhtari
Keyword(s):  
Couette Flow ◽  
Metal Flow ◽  
Three Dimensional ◽  
Liquid Sodium ◽  
Taylor Vortex ◽  
Turbulent Regime ◽  
Coaxial Cylinders ◽  
Concentric Cylinders ◽  
Ideal Tool ◽  
The Stability

Abstract The Taylor-Couette flow between two rotating coaxial cylinders remains an ideal tool for understanding the mechanism of the transition from laminar to turbulent regime in rotating flow for the scientific community. We present for different Taylor numbers a set of three-dimensional numerical investigations of the stability and transition from Couette flow to Taylor vortex regime of a viscous incompressible fluid (liquid sodium) between two concentric cylinders with the inner one rotating and the outer one at rest. We seek the onset of the first instability and we compare the obtained results for different velocity rates. We calculate the corresponding Taylor number in order to show its effect on flow patterns and pressure field.

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