Stability Analysis of a Slope considering Two Reinforcement Processes

The strength reduction method embedded in a distinct element code was used to analyse the stability of a slope in a coal mining area that had been reinforced twice, primarily with pile and retaining wall, followed by porous steel-tube bored grouting. For the primary reinforcement, the factor of safety was calculated, slip surface and failure mechanism were determined, and the damage phenomenon of primary reinforcement was analysed in detail. Failure time of slope without further strengthening was predicted by applying a new quantitative method based on monitoring displacement data. The slope instability at the primary reinforced stage was verified by these analyses. For the second reinforcement, the effect was evaluated by combining the new factor of safety and the final monitoring data, which validates the slope stability. Especially, variations of displacement and factor of safety due to water influence are analysed. Through this procedure, a systemic method for the slope safety evaluation and assurance is presented for engineering practice reference.

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The 2001 R.M. Hardy Lecture: The limits of limit equilibrium analyses

Canadian Geotechnical Journal ◽

10.1139/t03-024 ◽

2003 ◽

Vol 40 (3) ◽

pp. 643-660 ◽

Cited By ~ 89

Author(s):

John Krahn

Keyword(s):

Finite Element ◽

Factor Of Safety ◽

Slip Surface ◽

Limit Equilibrium ◽

Geotechnical Engineering ◽

Software Tools ◽

Great Promise ◽

Engineering Practice ◽

Stability Factor ◽

Limit Equilibrium Methods

Limit equilibrium types of analysis have been in use in geotechnical engineering for a long time and are now used routinely in geotechnical engineering practice. Modern graphical software tools have made it possible to gain a much better understanding of the inner numerical details of the method. A closer look at the details reveals that the limit equilibrium method of slices has some serious limitations. The fundamental shortcoming of limit equilibrium methods, which only satisfy equations of statics, is that they do not consider strain and displacement compatibility. This limitation can be overcome by using finite element computed stresses inside a conventional limit equilibrium framework. From the finite element stresses both the total shear resistance and the total mobilized shear stress on a slip surface can be computed and used to determine the factor of safety. Software tools that make this feasible and practical are now available, and they hold great promise for advancing the technology of analyzing the stability of earth structures.Key words: limit equilibrium, stability, factor of safety, finite element, ground stresses, slip surface.

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Vertical Expansion Stability of an Existing Landfill: A Case Study of a Landfill in Xi’an, China

Advances in Civil Engineering ◽

10.1155/2021/5574238 ◽

2021 ◽

Vol 2021 ◽

pp. 1-14

Author(s):

Hui Sheng ◽

Yinbang Ren ◽

Man Huang ◽

Zhenying Zhang ◽

Jiwu Lan

Keyword(s):

Factor Of Safety ◽

Slip Surface ◽

Slope Instability ◽

Stability Factor ◽

Foundation Soil ◽

Instability Modes ◽

Leachate Level ◽

The Stability ◽

Leachate Water

The vertical expansion of existing landfills can hold significant amounts of domestic waste and solve practical difficulties such as local government site selection. This research topic has become increasingly popular in the field of environmental geotechnical engineering. This study examined vertical expansion stability of landfills considering high leachate water level. The results showed the following. (1) Four slope instability modes for landfill vertical expansion are categorized according to the following slip surface positions: shallow slippage of the existing landfill, shallow slippage of the expanding landfill, interface slip between the existing landfill and expanding landfill, and deep slippage passes through the foundation soil. (2) The factor of safety decreases as the height of leachate level increases. When the height of leachate level rises from 2 m to 20 m, the factor of safety of the landfill is reduced by 13.2–15.4%. (3) As the vertical expansion height increases, the factor of safety of the existing landfill decreases, and when the expansion height increases to 30 m, the stability factor of safety of the old waste landfill is reduced by 4.83%. A landfill in Xi’an is considered as an example for the analysis, which shows that a leachate drainage layer can discharge leachate from the landfill body efficiently, reduce the leachate level height of the landfill body, and improve the stability of vertical expansion of the landfill. This study and its findings can be used as a reference for similar expansion projects.

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Slip surface in narrow backfill behind retaining wall

E3S Web of Conferences ◽

10.1051/e3sconf/202133103012 ◽

2021 ◽

Vol 331 ◽

pp. 03012

Author(s):

Abdul Hakam ◽

Deni Irda Mazni

Keyword(s):

Factor Of Safety ◽

Slope Failure ◽

Slip Surface ◽

Retaining Wall ◽

Soil Mass ◽

Soil Slope ◽

Soil Pressure ◽

Earth Reinforcement ◽

The Stability ◽

Steep Slopes

For a particular area in Geotechnical engineering, a soil slope is defined as a surface of soil mass which is inclined. It the slope is unstable or has insufficient factor of safety, then it needs to be strengthened by a retaining wall or a particular earth reinforcement to ensue slope failure does not occur. It has long been known that the pattern of slip failure is classified into two main types: translation and rotation. Other patterns of slip failure can be approached within the two mentioned types above. The main purpose of this classification is to assist the engineers in the process of the the stability analysis in purpose to obtain the safety factor of the slope and the reinforcement system if any. For the retaining wall reinforcement analysis, the developed method is generally in the form of soil pressure behind the wall. The pressure due to the self weight of the soil is generated by assuming the backfill is long enough, so that the slip failure can be fully described according to the two main types above. Then in cases where the backfill behind the wall is quite narrow, the method should be corrected or modified. These narrow areas are often found on roads that are built on relatively steep slopes. In this paper, the form of the slip failure behind a narrow retaining wall is presented. The results of this study are very useful for developing analytical methods for retaining soils that are built in narrow areas due to location limitations.

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Experimental Study on Delaying the Failure Time of In-Service Cables in Trays by Using Fire-Retardant Coatings

Applied Sciences ◽

10.3390/app11062521 ◽

2021 ◽

Vol 11 (6) ◽

pp. 2521

Author(s):

Feng Jiang ◽

Jianyong Liu ◽

Wei Yuan ◽

Jianbo Yan ◽

Lin Wang ◽

...

Keyword(s):

Fire Resistance ◽

Failure Time ◽

Fire Retardant ◽

Resistance Test ◽

Control Group ◽

Engineering Practice ◽

Standard Fire ◽

Oil Storage ◽

Fire Resistance Test ◽

Test Furnace

Improving the fire resistance of the key cables connected to firefighting and safety equipment is of great importance. Based on the engineering practice of an oil storage company, this study proposes a modification scheme that entails spraying fire-retardant coatings on the outer surface of a cable tray to delay the failure times of the cables in the tray. To verify the effect, 12 specimens were processed using five kinds of fire-retardant coatings and two kinds of fire-resistant cotton to coat the cable tray. The specimens were installed in the vertical fire resistance test furnace. For the ISO 834 standard fire condition, a fire resistance test was carried out on the specimens. The data for the surface temperature and the insulation resistance of the cables in trays were collected, and the fireproof effect was analyzed. The results showed that compared with the control group, the failure time of the cable could be delayed by 1.57–14.86 times, and the thicker the fire-retardant coatings were, the better the fireproof effect was. In general, the fire protection effect of the fire-retardant coating was better than that of the fire-resistant cotton.

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Convergence aspect of limit equilibrium methods for slopes

Canadian Geotechnical Journal ◽

10.1139/t90-013 ◽

1990 ◽

Vol 27 (1) ◽

pp. 145-151 ◽

Cited By ~ 13

Author(s):

R. N. Chowdhury ◽

S. Zhang

Keyword(s):

Factor Of Safety ◽

Slip Surface ◽

Limit Equilibrium ◽

Solution Process ◽

Iterative Solution ◽

Friction Angle ◽

Equilibrium Analysis ◽

Negative Slope ◽

Slip Surfaces ◽

Geological Discontinuity

This note is concerned with the multiplicity of solutions for the factor of safety that may be obtained on the basis of the method of slices. Discontinuities in the function for the factor of safety are discussed and the reasons for false convergence in any iterative solution process are explored, with particular reference to the well-known Bishop simplified method (circular slip surfaces) and Janbu simplified or generalized method (slip surfaces of arbitrary shape). The note emphasizes that both the solution method and the method of searching for the critical slip surface must be considered in assessing the potential for numerical difficulties and false convergence. Direct search methods for optimization (e.g., the simplex reflection method) appear to be superior to the grid search or repeated trial methods in this respect. To avoid false convergence, the initially assumed value of factor of safety F0 should be greater than β1(=−tan α1 tan [Formula: see text]) where α1 and [Formula: see text] are respectively the base inclination and internal friction angle of the first slice near the toe of a slope, the slice with the largest negative reverse inclination. A value of F0 = 1 + β1, is recommended on the basis of experience. If there is no slice with a negative slope for any of the slip surfaces generated in the automatic, search process, then any positive value of F0 will lead to true convergence for F. It is necessary to emphasize that no slip surface needs to be rejected for computational reasons except for Sarma's methods and similarly no artificial changes need to be made to the value of [Formula: see text] except for Sarma's methods. Key words: slope stability, convergence, limit equilibrium, analysis, optimization, slip surfaces, geological discontinuity, simplex reflection technique.

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Numerical Analysis of Soil Slope Stabilization by Soil Nailing Technique

Engineering, Technology & Applied Science Research ◽

10.48084/etasr.2859 ◽

2019 ◽

Vol 9 (4) ◽

pp. 4469-4473

Author(s):

D. A. Mangnejo ◽

S. J. Oad ◽

S. A. Kalhoro ◽

S. Ahmed ◽

F. H. Laghari ◽

...

Keyword(s):

Factor Of Safety ◽

Slope Failure ◽

Limit Equilibrium ◽

Slope Instability ◽

Soil Nailing ◽

Soil Slope ◽

Prevention Measures ◽

Soil Nail ◽

Soil Shear Strength ◽

Nail Diameter

Slope instability may be a result of change in stress conditions, rise in groundwater table and rainfall. Similarly, many slopes that have been stable for several years can abruptly fail due to changes in geometry, weak soil shear strength or as the effect of an external force. Debris flows (i.e. slope failures) take place without any warning and can have devastating results. So, it is vital to understand the slope failure mechanism and adopt safety prevention measures. Soil nailing is one of the widely used stabilization techniques for soil slopes. In this study, soil nail technique is proposed to upgrade the existing slope in clay. A parametric study was conducted to understand the effects of different nail diameter (i.e. 25mm and 40mm) and nail inclination (i.e. 200, 250, 300, 350 and 400) on slope stability. Morgenstern-Price (i.e. limit equilibrium) method was used to determine the factor of safety of the slope. It was found that the factor of safety of the existing slope improved significantly with three rows of 40mm diameter nail at an inclination of 400.

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Slope failure characteristics and stabilization methods

Canadian Geotechnical Journal ◽

10.1139/t06-131 ◽

2007 ◽

Vol 44 (4) ◽

pp. 377-391 ◽

Cited By ~ 13

Author(s):

H (Joanna) Chen ◽

S H Liu

Keyword(s):

Numerical Model ◽

Slope Failure ◽

Slip Surface ◽

Distinct Element ◽

Distinct Element Method ◽

Soil Nails ◽

Failure Characteristics ◽

Stabilization Methods ◽

Installation Angle ◽

Element Method

This paper presents numerical and laboratory experiments to investigate slope failure characteristics and commonly used slope stabilization methods. Using an improved distinct element method, the interparticle adhesive force is incorporated with a modified numerical model to account for the effect of suction. The model is validated through laboratory tilting box tests. Calculated slope failure angles are consistent with experimental observations. Different patterns of slip surface are also identified. Furthermore, the modified numerical model quantifies the micromechanical characteristics of the interparticle network and their evolutions during shear deformation. The calculations show that the maximum ratio of shear stress to normal stress takes place when the contact plane coincides with the mobilized plane, whereas the minimum value occurs when it is parallel to the directions of principal stresses. On this basis, we propose the optimal installation angle of soil nails along the minor principal stress (σ3) direction. The effectiveness of this approach is evaluated through tilting box tests. Two commonly used slope surface stabilization methods are also experimentally investigated.Key words: distinct element method, tilting box test, slip surface, optimal installation angle of soil nails.

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Computational fluid dynamics optimization of gas drainage technology in gas-mining areas

Energy Exploration & Exploitation ◽

10.1177/01445987211063586 ◽

2021 ◽

pp. 014459872110635

Author(s):

Wei Zhao ◽

Wei Qin

Keyword(s):

Fluid Dynamics ◽

Computational Fluid Dynamics ◽

Coal Seam ◽

Field Tests ◽

Mining Area ◽

Engineering Practice ◽

Horizontal Distance ◽

Gas Drainage ◽

Working Face ◽

Gas Seepage

Coal mining results in strata movement and surrounding rock failure. Eventually, manual mining space will be occupied by the destructed coal rock, making it difficult to conduct field tests of the coal seam to explore gas seepage and transport patterns. Therefore, computational fluid dynamics (CFD) numerical computation is an important tool for such studies. From the aspect of gas pre-drainage, for layer-through boreholes in the floor roadway of the 8,406 working face in Yangquan Mine 5 in China, reasonable layout parameters were obtained by CFD optimization. For effectively controlling the scope of boreholes along coal seam 9 in the Kaiyuan Mine, CFD computation was performed. The results revealed that the horizontal spacing between boreholes should be ≤2 m when a tri-quincuncial borehole layout is used. Optimization of the surface well position layout for the fault structure zone in the Xinjing Mine of the Yangquan mining area indicated that the horizontal distance between the surface well and the fault plane should be <150 m. From the aspect of gas drainage with mining-induced pressure relief, CFD computation was performed for pressure-relieved gas transport in the K8205 working face of Yangquan Mine 3. The results showed that forced roof caving should be used before the overhang length of hard roof reaches 25 m in the K8205 working face to avoid gas overrun. From the aspect of gas drainage from the abandoned gob, surface well control scopes at different surface well positions were computed, and an O-ring fissure zone is proposed as a reasonable scope for the surface well layout. CFD computation has been widely applied to coal and gas co-extraction in the Yangquan mining area and has played a significant role in guiding related gas drainage engineering practice.

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Landslide Simulation Using Limit Equilibrium and Finite Element Method

Materials Science Forum ◽

10.4028/www.scientific.net/msf.857.555 ◽

2016 ◽

Vol 857 ◽

pp. 555-559 ◽

Cited By ~ 1

Author(s):

Zuhayr Md Ghazaly ◽

Mustaqqim Abdul Rahim ◽

Kok Alfred Chee Jee ◽

Nur Fitriah Isa ◽

Liyana Ahmad Sofri

Keyword(s):

Finite Element Method ◽

Finite Element ◽

Factor Of Safety ◽

Slip Surface ◽

Limit Equilibrium ◽

Main Concern ◽

Analysis Method ◽

Stability Of Slope ◽

The Stability ◽

Element Method

Slope stability analysis is one of the ancient tasks in the geotechnical engineering. There are two major methods; limit equilibrium method (LEM) and finite element method (FEM) that were used to analyze the factor of safety (FOS) to determine the stability of slope. The factor of safety will affect the remediation method to be underdesign or overdesign if the analysis method was not well chosen. This can lead to safety and costing problems which are the main concern. Furthermore, there were no statement that issued one of the analysis methods was more preferred than another. To achieve the objective of this research, the soil sample collected from landslide at Wang Kelian were tested to obtain the parameters of the soils. Then, those results were inserted into Plaxis and Slope/W software for modeling to obtain the factor of safety based on different cases such as geometry and homogenous of slope. The FOS obtained by FEM was generally lower compared to LEM but LEM can provide an obvious critical slip surface. This can be explained by their principles. Overall, the analysis method chosen must be based on the purpose of the analysis.

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Analysis of Dynamic Coupling Characteristics of the Slope Reinforced by Sheet Pile Wall

Shock and Vibration ◽

10.1155/2017/9043518 ◽

2017 ◽

Vol 2017 ◽

pp. 1-10 ◽

Cited By ~ 1

Author(s):

H. L. Qu ◽

H. Luo ◽

L. Liu ◽

Y. Liu

Keyword(s):

Slip Surface ◽

Retaining Wall ◽

Time History ◽

Interaction Force ◽

Body Parts ◽

Sheet Pile ◽

Stabilizing Piles ◽

The Difference ◽

Coupling Characteristics ◽

Sheet Pile Wall

Large deformation of slope caused by earthquake can lead to the loss of stability of slope and its retaining structures. At present, there have been some research achievements about the slope reinforcement of stabilizing piles. However, due to the complexity of the structural system, the coupling relationship between soil and pile is still not well understood. Hence it is of great necessity to study its dynamic characteristics further. In view of this, a numerical model was established by FLAC3D in this paper, and the deformation and stress nephogram of sheet pile wall in peak ground motion acceleration (PGA) at 0.1 g, 0.2 g, and 0.4 g were obtained. Through the analysis, some conclusions were obtained. Firstly, based on the nephogram of motion characteristics and the positions of the slip surface and the retaining wall, the reinforced slope can be divided into 6 sections approximatively, namely, the sliding body parts of A, B, C, D, and E and the bedrock part F. Secondly, the deformation and stress distributions of slope reinforced by sheet pile wall were carefully studied. Based on the results of deformation calculation from time history analysis, the interaction force between structure and soil can be estimated by the difference of peak horizontal displacements, and the structure-soil coupling law under earthquake can be studied by this approach.

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