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.

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.

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.

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.

Detailed Stress Analysis of a Spherical Acrylic Submersible by 3-D Finite Element Modeling

1999 ◽  
Author(s):  
Partha S. Das
Keyword(s):  
Finite Element ◽  
Numerical Modeling ◽  
Dissimilar Materials ◽  
Analysis Model ◽  
Element Analysis ◽  
Finite Element Analysis Model ◽  
New Model ◽  
Ocean Exploration ◽  
Near Future ◽  
First Time

Abstract Harbor Branch Oceanographic Institution (HBOI) designed, built and has operated two JOHNSON-SEA-LINK (JSL) manned submersibles for the past 25 years. The JSL submersibles each incorporate a 66–68 in. (1.6764–1.7272 m) OD, 4–5.25 in. (0.1016–0.13335 m) thick acrylic two-man sphere as a Pressure Vessel for Human Occupancy (PVHO). This type of spherical acrylic sphere or submersible was first introduced in around 1970 and is known as Naval Experimental Manned Observatory (NEMO) submersibles. As the demand increases for ocean exploration to 3000 ft. (914.4 m) depth to collect samples, to study the ocean surfaces, the problem of developing cracks at the interface of these manned acrylic submersibles following few hundred dives have become a common phenomena. This has drawn considerable attentions for reinvestigation of the spherical acrylic submersible in order to overcome this crack generation problem at the interface. Therefore, a new full-scale 3-D nonlinear FEA (Finite Element Analysis) model, similar to the spherical acrylic submersible that HBOI uses for ocean exploration, has been developed for the first time in order to simulate the structural behavior at the interface and throughout the sphere, for better understanding of the mechanical behavior. Variation of the stiffness between dissimilar materials at the interface, lower nylon gasket thickness, over designed aluminum hatch are seemed to be few of the causes for higher stresses within acrylic sphere at the nylon gasket/acrylic interface. Following the basic understanding of the stresses and relative displacements at the interface and within different parts of the submersible, various models have been developed on the basis of different shapes and thickness of nylon gaskets, openings of the acrylic sphere, hatch geometry and its materials, specifically to study their effect on the overall performance of the acrylic submersible. Finally, the new model for acrylic submersible has been developed by redesigning the top aluminum hatch and hatch ring, the sphere openings at both top and bottom, as well as the nylon gasket inserts. Altogether this new design indicates a significant improvement over the existing spherical acrylic submersible by reducing the stresses at the top gasket/acrylic interface considerably. Redesigning of the bottom penetrator plate, at present, is underway. In this paper, results from numerical modeling only are reported in details. Correlation between experimental-numerical modeling results for the new model will be reported in the near future.

scholarly journals Finite Element Analysis of Natural Thawing Heat Transfer of Artificial Frozen Soil in Shield-Driven Tunnelling

2020 ◽  
Vol 2020 ◽  
pp. 1-18
Author(s):  
Yong Fu ◽  
Jun Hu ◽  
Jia Liu ◽  
Shengbin Hu ◽  
Yunhui Yuan ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Finite Element ◽  
Three Dimensional ◽  
Frozen Soil ◽  
Soil Reinforcement ◽  
Freezing Process ◽  
Element Analysis ◽  
Heat Transfer Behavior ◽  
Transfer Behavior ◽  
Three Dimensional Finite Element

The technology of artificial horizontal freezing method is increasingly being used in the soil reinforcement of urban underground projects such as shield-driven tunnelling. Compared with the freezing process, the thawing process is more complicated, and the thawing behavior of artificial frozen soil surrounding shield-driven tunnels has not been well investigated in both the academic and industrial domains. This study, therefore, aims to investigate the natural thawing heat transfer behavior of artificial horizontal frozen soil in shield-driven tunnelling using a three-dimensional finite element method. The finite element modelling is based on the horizontal freezing reinforcement project of Chating Station to Jiqingmen Station Tunnel in the Nanjing Metro Line 2. Validation between finite element results and site measured results is firstly conducted. The natural thawing temperature field contours as well as the radial and longitudinal distributions of natural thawing temperature in the frozen soil surrounding the tunnel are then explicitly examined. Furthermore, sensitivity analysis of influencing factors such as the thermal conductivity, latent heat of phase change, ambient temperature inside tunnel, freezing time, and original ground temperature is carried out. The results and findings of this study may enrich the current limited database and enable a better understanding of natural thawing heat transfer behavior of artificial frozen soil in shield-driven tunnelling.

scholarly journals Finite Element Analysis of Geogrid-Stabilized Unpaved Roads

2020 ◽  
Vol 12 (5) ◽  
pp. 1929
Author(s):  
Giovanni Leonardi ◽  
Dario Lo Bosco ◽  
Rocco Palamara ◽  
Federica Suraci
Keyword(s):  
Finite Element ◽  
Fem Analysis ◽  
Base Layer ◽  
Element Analysis ◽  
Unpaved Roads ◽  
Unpaved Road ◽  
Traffic Loads ◽  
Granular Fill ◽  
Wheel Loading ◽  
Granular Base

The need to increase the durability of unpaved roads and the need to improve driver comfort have led to this research: to focus more attention on the use of reinforcements for this type of road. Unpaved roads are created by using an unbound granular base layer placed on compacted cohesive soils. When the subgrade is weak, due to its poor consistency and high compressibility, generally, a geosynthetic reinforcement (geogrid and/or geotextile) is placed over the subgrade, followed by a compacted granular fill layer. The use of geosynthetics can produce several benefits, such as draining, reinforcement, filtering, separation, and proofing. This paper aims to present a numerical investigation using 3-D Finite Element Modeling (FEM) to analyze the improvement, in terms of the rutting reduction of an unpaved road system, reinforced by a geogrid, under repeated traffic loads. 3-D FEM analysis was carried out on two unpaved road sections, one reinforced and the other unreinforced, with both subjected to an impulsive wheel loading. It can be concluded that a significant improvement in pavement behavior is obtained by placing a geogrid layer at the base–subgrade interface. In fact, the obtained results show that geogrid reinforcement can provide a relevant contribution to the reduction of permanent deformations.

Finite element modeling of hexagonal wire reinforced embankment on soft clay

2000 ◽  
Vol 37 (6) ◽  
pp. 1209-1226 ◽  
Author(s):  
D T Bergado ◽  
C Teerawattanasuk ◽  
S Youwai ◽  
P Voottipruex
Keyword(s):  
Finite Element ◽  
Full Scale ◽  
Soil Reinforcement ◽  
Wire Mesh ◽  
Direct Shear ◽  
Full Scale Test ◽  
Element Analysis ◽  
Consolidation Process ◽  
Scale Test ◽  
Test Embankment

A full-scale test embankment was constructed on soft Bangkok clay using hexagonal wire mesh as reinforcement. This paper attempts to simulate the behavior of the full-scale test embankment using the finite element program PLAXIS. The agreement between the finite element results and the field data is quite good. The important considerations for simulating the behavior of the reinforced wall embankment were the method of applying the embankment loading during the construction process, the variation of soil permeability during the consolidation process, and the selection of the appropriate model and properties at the interface between the soil and reinforcement. The increased reinforcement stiffness tends to increase the reinforcement tension and increase the embankment forward rotation. The reinforcement tensions increased with the compression of the underlying soft foundation. The appropriate interface properties between the backfill soil and the hexagonal wire mesh reinforcement corresponding to the interaction mechanism at working stress conditions were dominated by the direct shear mechanism. The direct shear interaction coefficient of 0.9 was used.Key words: soil reinforcement, hexagonal wire mesh, finite element analysis, field embankment.

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