scholarly journals Numerical Analysis on Reinforcement Range of a Closed Steel Sleeve against Collapse

2021 ◽  
Vol 2021 ◽  
pp. 1-10
Author(s):  
Qing-Feng Yin
Keyword(s):  
Reinforced Soil ◽  
Soil Reinforcement ◽  
Longitudinal Reinforcement ◽  
Soil Pressure ◽  
Element Analysis ◽  
Jet Grouting ◽  
Soil Settlement ◽  
Steel Sleeve ◽  
Shield Machine ◽  
Closed Steel

Before the shield machine begins to excavate, the end of the station structure often requires extensive soil reinforcement to ensure construction safety. Closed steel sleeve can prevent water leakage, sand leakage, and cave door collapse by balancing the water and soil pressure on the tunnel surface, thereby reducing the reinforcement range. In this study, a launching project of a closed steel sleeve is investigated; the Madis GTS finite element analysis software is used to simulate the triple-tube high-pressure jet-grouting pile to reinforce the water-rich sand layer. Soil displacement and stress after opening of the tunnel door are studied in detail at different longitudinal reinforcement lengths and transverse reinforcement scopes. The results show that, as the longitudinal reinforcement length increases, the displacement of the soil shows a decreasing trend, and the greater the length of the reinforced soil, the smaller the reduction in displacement. Furthermore, with the decrease of the lateral reinforcement range, though the soil settlement area has increased, the displacement remains unchanged. However, changing the end reinforcement range has no effect on the soil stress. In general, based on the strength and stability of the soil after the gate is cut out, the reinforcement range of the closed steel sleeve can be appropriately reduced compared to traditional reinforcement methods.

Stresses and deformations in a reinforced soil slope

1990 ◽  
Vol 27 (2) ◽  
pp. 224-232 ◽  
Author(s):  
R. J. Chalaturnyk ◽  
J. D. Scott ◽  
D. H. K. Chan ◽  
E. A. Richards
Keyword(s):  
Finite Element ◽  
Slip Surface ◽  
Limit Equilibrium ◽  
Maximum Load ◽  
Reinforced Soil ◽  
Soil Reinforcement ◽  
Soil Slope ◽  
Element Analysis ◽  
Reinforced Slope ◽  
Reinforcing Layer

Nonlinear finite element analyses were performed on a nonreinforced embankment and a polymeric reinforced embankment, with 1:1 side slopes, constructed on competent foundations. The nonreinforced and reinforced embankment analyses are compared to examine the influence of polymeric reinforcement within a soil slope. It is shown that significant reductions in the shearing, horizontal, and vertical strains within the slope occur because of the presence of the reinforcement.The finite element analysis of the reinforced embankment construction gives the magnitude and distribution of load within the reinforcement. For all embankment heights, the maximum reinforcement load did not occur in the lowest reinforcing layer but in the reinforcing layer placed 0.4H above the foundation, where H is the height of the slope. The displacement patterns and surface deformations of the nonreinforced and reinforced slopes are compared to show the marked reduction in slope movements resulting from the presence of the reinforcement.The location and shape of potential shear surfaces within the homogeneous reinforced slope are examined. The position of the maximum load in each reinforcing layer within the reinforced slope indicates that, for the example studied, a circular-shaped slip surface represents a probable failure mechanism within the slope. Key words: soil reinforcement, geotextiles, finite element, slope stability, geogrids, limit equilibrium, reinforced slope.

scholarly journals Influence of Water Inrush from Excavation Surface on the Stress and Deformation of Tunnel-Forming Structure at the Launching-Arrival Stage of Subway Shield

2019 ◽  
Vol 2019 ◽  
pp. 1-20
Author(s):  
Shusheng Lv ◽  
Wen Liu ◽  
Shihong Zhai ◽  
Peishuai Chen
Keyword(s):  
Simulation Analysis ◽  
Coupling Effect ◽  
Water Inrush ◽  
Ground Surface ◽  
Reinforced Soil ◽  
Soil Reinforcement ◽  
Shield Tunnel ◽  
Deformation Properties ◽  
Stress And Deformation ◽  
Shield Machine

The launching-arrival stage of the shield is the most dangerous construction stage in subway construction. During the conversion process of the soil and air medium in the shield machine, water inrush at the excavation surface often occurs because of the effect of groundwater. Previous research has focused on the overall stress and deformation of existing tunnels caused by water inrush from the excavation face of the shield machine excavation stage. However, the stress and deformation states of the segments and anchors at different assembly locations of the tunnel, as well as the interaction between the soil reinforcement region and the segments and anchors in the launching-arrival stage have not been considered in previous studies. In this study, the inrush model of the launching-arrival stage of the subway shield was established by utilizing the equivalent refinement modeling technology and ABAQUS simulation analysis with consideration of the fluid-solid coupling effect of water and soil to study the influences of different water head differences on the mechanical and deformation properties of segments and anchors in shield construction under the conditions of water inrush on the excavation surface. The results showed that the water inflow from the tunnel excavation surface caused significant surface subsidence at the tunnel portal, vertical convergence at the cross section of the shield tunnel, and significant increases in the axial and shear forces on the bolt. In addition, based on the existing subway regulation, combined with the simulation results of soil reinforcement measures at different depths, the emergency control criterion for controlling water inrush on the excavation surface was established by using the depth of soil reinforcement. The minimum depth of the reinforced soil from the ground surface at 15 m is recommended to ensure construction safety of the subway shield at the launching-arrival stage.

Some techniques for finite element analysis of embankments on soft ground

1993 ◽  
Vol 30 (4) ◽  
pp. 710-719 ◽  
Author(s):  
J.C. Chai ◽  
D.T. Bergado
Keyword(s):  
Finite Element ◽  
Numerical Models ◽  
Relative Displacement ◽  
Technical Note ◽  
Reinforced Soil ◽  
Soil Reinforcement ◽  
Soft Ground ◽  
Element Analysis ◽  
Consolidation Process ◽  
Interface Elements

The accuracy of finite element results depends on the numerical models and the parameters used as well as the numerical techniques adopted. Three aspects of modelling the behavior of embankment on soft ground are discussed in this technical note: (i) simulating the actual construction process, (ii) modelling the soft ground permeability variation during the loading and consolidation process, and (iii) selecting proper soil–reinforcement interface properties according to the relative displacement pattern of the upper and lower interface elements placed between the soil and reinforcement in the case of a reinforced embankment. The significance of these factors on the performance of the embankment on soft ground is demonstrated by case studies. Key words : finite element method, loading, permeability, reinforced soil.

Analysis of membrane action in reinforced unpaved roads

1995 ◽  
Vol 32 (6) ◽  
pp. 946-956 ◽  
Author(s):  
H.J. Burd
Keyword(s):  
Finite Element ◽  
Soft Clay ◽  
Reinforced Soil ◽  
Soil Reinforcement ◽  
Single Application ◽  
Membrane Action ◽  
Element Analysis ◽  
Unpaved Roads ◽  
New Model ◽  
Design Procedures

Polymer grid or geotextile reinforcement may be used to improve the performance of reinforced fill layers placed on soft ground. This paper is concerned with the mechanics and design of reinforced unpaved roads built over soft clay, which is a particular application of this reinforced soil technique. A discussion is given of the mechanics of reinforced unpaved roads for the case of a single application of a plane strain, monotonic load, and the design procedures that are currently available for this type of structure are reviewed. A new analytical design model is proposed. This new model is based on a membrane reinforcement mechanism and is appropriate for cases where large surface deformations are acceptable. Results obtained using this new model are shown to compare well with data obtained from previously published laboratory tests. The use of a finite element method to study this type of structure is described, and the results of finite element analysis are used to discuss the accuracy of the proposed analytical model. Key words : soil reinforcement, unpaved roads, membrane, finite elements, reinforcement mechanisms, foundations.

scholarly journals Effect of Soil Reinforcement on Tunnel Deformation as a Result of Stress Relief

2019 ◽  
Vol 9 (7) ◽  
pp. 1420
Author(s):  
Huasheng Sun ◽  
Wenbin Sun
Keyword(s):  
Young’S Modulus ◽  
Young's Modulus ◽  
Stress Transfer ◽  
Longitudinal Direction ◽  
Stress Relief ◽  
Reinforced Soil ◽  
Soil Reinforcement ◽  
Element Analysis ◽  
Quantitative Studies ◽  
Centrifugal Model

Adjacent geotechnical engineering activities, such as deep excavation, may adversely affect or even damage adjacent tunnels. Ground reinforcement before excavation may be an effective approach to reduce tunnel heave as a result of stress relief. However, there are few quantitative studies on the effect of soil reinforcement on tunnel deformation. Moreover, the reinforcement mechanism of the reinforced soil and the reinforcement depth are not fully understood. In order to investigate the effect of reinforcing the ground on the tunnel response, a finite element analysis was conducted based on a previously reported centrifugal model test with no ground reinforcement. The effect of the Young’s modulus and depth of the reinforced soil on tunnel deformation was analyzed. Soil stresses around the tunnel were also considered to explain the tunnel response. The results revealed that the Young’s modulus of the reinforced soil and the reinforcement depth had a significant impact on tunnel deformation as a result of basement excavation. The tunnel heave in the longitudinal direction decreased by 18% and 27% for modulus of the reinforced soil, five times and ten times higher than that of the non-reinforced soil, respectively. The reinforcement depth was effective with regard to controlling the tunnel heave caused by stress relief. This is because the reinforced soil blocked the stress transfer and thus reduced the tunnel heave caused by excavation unloading. It is expected that this study will be useful with regard to taking effective measures and ensuring the safety and serviceability of existing metro tunnels during adjacent excavation.

Improved understanding of geogrid response to pullout loading: insights from three-dimensional finite-element analysis

2020 ◽  
Vol 57 (2) ◽  
pp. 277-293 ◽  
Author(s):  
Mahmoud G. Hussein ◽  
Mohamed A. Meguid
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Three Dimensional ◽  
Reinforced Soil ◽  
Soil Reinforcement ◽  
Interface Condition ◽  
Element Analysis ◽  
Analysis And Design ◽  
Dimensional Finite Element ◽  
Three Dimensional Finite Element

Soil reinforcement has rapidly become one of the most common soil improvement techniques used in geotechnical engineering. Understanding the behavior of a geogrid under pullout loading is essential for the analysis and design of reinforced soil systems. The overall behavior of reinforced soils is generally dependent on the properties of the geogrid material, the backfill soil, and the interface condition. Modeling the three-dimensional aspects of soil–geogrid interaction under pullout loading condition is numerically challenging and requires special consideration of the different modes of resistance that contribute to the pullout capacity of the geogrid reinforcement. This study describes the results of a three-dimensional finite-element analysis that has been developed to investigate the behavior of a biaxial geogrid embedded in granular backfill material and subjected to pullout loading. The modeling approach considers the noncontinuous nature of the geogrid geometry and the elastoplastic response of the geogrid material. Model validation is performed by simulating laboratory-size pullout test and comparing the experimental data with the analytical as well as numerically calculated results. The detailed behavior of the geogrid and the surrounding backfill is investigated using the proposed numerical approach. Conclusions are made to highlight the suitability of this technique for analyzing similar soil–structure interaction problems.

Comparison of Field Behavior with Results from Numerical Analysis of a Geosynthetic Reinforced Soil Integrated Bridge System Subjected to Thermal Effects

2020 ◽  
Vol 2674 (1) ◽  
pp. 294-306
Author(s):  
Arshia Taeb ◽  
Phillip S.K. Ooi
Keyword(s):  
Pressure Fluctuations ◽  
Axial Loading ◽  
Reinforced Soil ◽  
Element Analysis ◽  
Vertical Pressure ◽  
Geosynthetic Reinforced Soil ◽  
End Wall ◽  
Cyclic Straining ◽  
Toe Pressure ◽  
Bridge System

When subjected to ambient daily temperature fluctuations, a 109.5 ft-long geosynthetic reinforced soil integrated bridge system (GRS-IBS) was observed to undergo cyclic straining of the superstructure. The upper and lower reaches of the superstructure experienced the highest and lowest strain fluctuation, respectively. These non-uniform strains impose not only axial loading of the superstructure but also bending. Pure axial loading in a horizontal superstructure will cause the footings to slide. However, bending in the superstructure will cause the footings to rotate thereby inducing cyclic fluctuations of the vertical pressure beneath the footing and also lateral pressure behind the end walls. Measured vertical footing pressure closest to the stream experienced the greatest daily pressure fluctuation (≈ 2,500–3,000 psf), while that nearest the end wall experienced the least. The toe pressure fluctuations seem rather large. That these large vertical pressure fluctuations are observed in a tropical climate like Hawaii when no other GRS-IBS in temperate regions has reported the same (or perhaps higher fluctuation) is indeed surprising. The larger these pressures are, the greater the likelihood of inducing cyclic-induced deformations of the GRS abutment. A finite element analysis of the same GRS-IBS was performed by applying an equivalent temperature and gradient to the superstructure over the coldest and hottest periods of a day to see if the field measured values of pressures are reasonable and verifiable, which indeed they were. This methodology is novel in the sense that the effects of axial load and bending of the superstructure are simulated using measured strains rather than measured temperatures.

Application of High Pressure Spiral Jet Grouting Piles in Shield Tunnel Portal Soil Reinforcement Engineering

ICPTT 2012 ◽  
2012 ◽  
Author(s):  
Chengliang Gao ◽  
Lei Nie ◽  
Xiaoqiang Liang
Keyword(s):  
High Pressure ◽  
Soil Reinforcement ◽  
Shield Tunnel ◽  
Jet Grouting ◽  
Tunnel Portal

scholarly journals An Experimental Study of Horizontal Bearing Capacity of Vertical Steel Floral Tube Micropiles with Double Grouting

2018 ◽  
Vol 2018 ◽  
pp. 1-11
Author(s):  
Kaiyang Wang ◽  
Yanjun Shang
Keyword(s):  
Bearing Capacity ◽  
Large Scale ◽  
Slip Surface ◽  
Bending Moment ◽  
Shear Capacity ◽  
Soil Reinforcement ◽  
Scale Model ◽  
Soil Pressure ◽  
Floral Tube ◽  
Grouting Pressure

This paper examines the performance of a novel technology, vertical steel floral tube micropiles with double grouting. It is the combination of micropile technology and double grouting technology. A large-scale model tank was applied to impart horizontal bearing capacity, and the slope soil pressure and flexural performance of the micropile were investigated under four experimental conditions. The peak grouting pressure during the double grouting process was defined as the fracturing pressure of the double grouting, and it was positively correlated to the interval time between first grouting and secondary grouting. Compared with traditional grouting, double grouting increased the horizontal bearing capacity of the single micropile with the vertical steel floral tube by 24.42%. The horizontal bearing capacity was also 20.25% higher for the structure with three micropiles, compared with a 3-fold value of horizontal sliding resistance. In the test, the maximum bending moment acting on the pile above the sliding surface was located 2.0–2.5 m away from the pile top, and the largest negative bending moment acting on the pile below the slip surface was located 4.0 m away from the pile top. The ultimate bending moment of the single pile increased by 12.8 kN·m with double grouting, and the bending resistance increased by 96.2%. The experimental results showed that the double grouting technology significantly improved the horizontal bearing capacity of the micropile with the steel floral tube, and the soil reinforcement performance between piles was more pronounced. Also, the shear capacity and the flexural capacity were significantly improved compared with the original technology.

Parameter Analysis on Bearing Capacity of Concrete-Filled Square Steel Tubular Column to Steel-Encased Concrete Composite Beam Joint with through Diaphragm

2014 ◽  
Vol 1065-1069 ◽  
pp. 1203-1207
Author(s):  
Yan Lin ◽  
Xue Jun Zhou ◽  
Yu Chen Liu ◽  
Wen Qing Kong
Keyword(s):  
Bearing Capacity ◽  
Composite Beam ◽  
Plastic Hinge ◽  
Nonlinear Finite Element ◽  
Parameter Analysis ◽  
Longitudinal Reinforcement ◽  
Element Analysis ◽  
Obvious Effect ◽  
Axial Compression Ratio ◽  
New Type

A new type of concrete-filled square steel tubular column to steel-encased concrete composite beam joint is proposed. In order to study the influences of parameters on bearing capacity for the joint formed plastic hinge in the beam end, nonlinear finite element analysis under monotonic loading is conducted by software ANSYS. The results show that axial compression ratio has little influence on joint bearing capacity, and with the increasing of it, the bearing capacity is enhanced slightly. The height of U-shape steel has a significant impact on joint bearing capacity, and with the rise of it, the bearing capacity is enhanced obviously. The thickness of U-shape steel has a comparatively obvious effect on joint bearing capacity with certain limits, and with the growth of it, the bearing capacity of the joint is also grown observably. The diameter of longitudinal reinforcement in the flange slab of beam has some effects on joint bearing capacity, and with the improvement of diameter, the bearing capacity is achieved.

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