Reinforced Earth Structures Research Articles

Design of reinforced earth structures based on nonlinear finite element analysis and limit equilibrium method : Bauer, G.E; Abd El-Halim, A O; Mowafy, Y M Proc Symposium on Computer Aided Design and Monitoring in Geotechnical Engineering, Bangkok, 3–6 December 1986P392–410. Publ Bangkok: AIT, 1986

Design of reinforced earth structures based on nonlinear finite element analysis and limit equilibrium method : Bauer, G.E; Abd El-Halim, A O; Mowafy, Y M Proc Symposium on Computer Aided Design and Monitoring in Geotechnical Engineering, Bangkok, 3–6 December 1986P392–410. Publ Bangkok: AIT, 1986

Geosynthetic Reinforced Soil Structures

An approach for stability analysis of geosynthetic reinforced earth structures over firm foundations is presented. The approach involves both internal and external stability analyses. The internal stability analysis is based on variational limiting equilibrium and satisfies all equilibrium requirements. Two extreme inclinations of reinforcement tensile resistance are investigated: orthogonal to the radius defining the geosynthetic sheet, and horizontal, signifying the as‐installed position. Although a horizontal positioning requires slightly longer anchorage to assure pullout resistance, the slip surface is shallower when compared to the orthogonal case. As a result, the required total embedment length is longer for the orthogonal inclination. The external stability analysis is an extension of the bilinear wedge method and it allows a slip plane to propagate horizontally along a reinforcing sheet. The results for both the internal and external stability analyses are conveniently presented in the form of design charts. Given a slope and a design safety factor, the geosynthetic sheets' profile as well as their required tensile resistance can be determined utilizing these charts.

Laboratory Investigation of Earth Walls Simultaneously Reinforced by Strips and Random Reinforcement

Abstract The performance of reinforced earth structures depends, among other factors, on the shear strength of the backfill material used in construction. The shear strength can be enhanced by the use of random reinforcement. This paper presents the result of laboratory investigations concerning the effects of several types of random reinforcement on soil strength and, in particular, on the performance of reinforced earth model walls. Six series of experiments were conducted, in which a medium sand randomly reinforced by various metal particles was used as a backfill material for construction of 32 model walls. In construction of the walls standard reinforcement (horizontal metal strips attached to facing units) was used as well. The results obtained from shear box tests and from observation of model wall failures indicate that the presence of random reinforcement could lead to a significant increase in the critical height of model walls. An increase of up to 13% was observed as a result of adding only 0.5% of random reinforcement to the sand used for the construction of model walls. It was also found that fiber-like shapes of random reinforcement particles give a more significant increase in the soil strength and critical height of walls than other shapes tested. It might be reasonably expected that a small quantity of similar random reinforcement used in full-scale constructions could lead to a significant increase of their design height or, alternatively, to a decrease in volume of standard reinforcement needed.

DURABILITY OF REINFORCED EARTH STRUCTURES: THE RESULTS OF A LONG-TERM STUDY CONDUCTED ON GALVANIZED STEEL.

Keywords TERRE ARMEE INTERNATIONALE FRANCE, CENTRE NATIONAL DE LA RECHERCHE, SCIENTIFIQUE FRANCE DURABILITY, EARTH, REINFORCED, STRUCTURES, STUDIES, STEEL, GALVANISED, UNDERGROUND, CORROSION, BURIED, DATA, SOILS, GRANULAR, LABORATORIES, MONITORING, LOSS, STRIP, TESTS, SPECIMENS, CORRELATION, RESEARCH, STRENGTH, THICKNESS, CONTAINERS, WATER, CONTENT, ELECTROCHEMISTRY, RED, LOW, SPECIFICATIONS, CLAYS, SAND, RIVERS, SATURATION, DRY, SHALE, EFFECT, CHLORIDE, SULPHATES, BEHAVIOUR, ZINC, COATINGS, OXIDATION, SITE INVESTIGATION, TENSILE, STRENGTH, LONG TERM, CALCULATIONS LOIRE FRANCE, USA... Show All

Temperature distributions in reinforced soil retaining walls

Temperature observations are presented from a seven-year study of a reinforced earth retaining wall forming part of the M25 motorway at Waltham Cross, UK. The structure employed the proprietary components of the Reinforced Earth Company involving galvanised mild steel reinforcement and cruciform facing units of reinforced concrete. Detailed observations of temperature in reinforced soil structures are rarely reported. This may be attributable to the fact that, over the usual temperature range associated with civil engineering structures, the stress-strain properties of steel reinforcements are not significantly affected. This can be contrasted with geotextiles whose properties may be affected over quite small temperature ranges. To ensure a satisfactory long-term performance of geotextile reinforcement, the properties employed in design must be based on reliable estimates of the temperatures to which this material is subjected. The paper also provides details of a method of analysis for determining the variation of temperature in a reinforced earth structure. When applied to the site at Waltham Cross, reasonable agreement was obtained with the recorded temperatures. The calculations were based on published meteorological data of ambient temperature and a coefficient of thermal diffusivity of 70m 2/year for the fill determined from one-dimensional analysis of the temperature records. This latter value is not considered to have been greatly influenced by the presence of the metallic reinforcement. In this regard the value may be applicable to other structures in which non-metallic reinforcements have been employed in granular fills. Although it is generally recognised that temperature fluctuations can have a very significant influence on geotextile properties, relatively little information has been published on the subject. Some consideration is also given to this topic, employing previously published information.

Seismic stability of reinforced earth structures. Recent progress in research (In French) : Bastick, M J Rev Fr GeotechN37, 1986, P67–71

Seismic stability of reinforced earth structures. Recent progress in research (In French) : Bastick, M J Rev Fr GeotechN37, 1986, P67–71

Large Scale Experiments on the Behavior of Embankment Reinforced with Spun-Bonded Non-Woven Fabrics (Part 1)

Large scale experiments on the behavior and the failure mechanism of embankment reinforced with spun-bonded non-woven fabrics were carried out under heavy rain condition. Test results show that the amount of drainage water from fabrics is not so large as expected, but the seepage water gather near fabrics and it cause erosion of the surface soil near fabrics. And the fabrics restrained the deformation or the plastic strains of the reinforced earth effectively, in spite of low stiffness of them. These observations led to the conclusion that the fabrics certainly modified the failure mechanism or the stresses and strains pattern and therefore an appropriate design method based on the real mechanism of the reinforced earth structures must be established.

Composite FEM Analysis for Layered Systems

A composite characterization and accompanying finite element analysis for layered systems is presented. The model is developed for plane strain and axisymmetric (horizontal layers) configurations with stiff, relatively thin isotropic layers of reinforcement sandwiched between layers of relatively flexible isotropic matrix material. Potential applications include elastomeric bearings and reinforced earth structures. The composite theory, in addition to capturing the overall response characteristics of the layered system, approximately models the important edge effects which occur at boundaries and the stress concentrations at layer interfaces. The primary dependent variables for the composite theory have been selected such that the highest derivatives appearing in the strain energy function are first order, thus requiring only C\do continuity of the finite element approximations. As a result, the accompanying finite analysis is simple and computationally efficient. Numerical examples are presented to verify the theory, compare it to previous results, and to illustrate potential applications of the analysis.

Reinforced earth - its design and application : Warwick, E R J Civ Engng, London, Sept 1982, P52–59

Applications for reinforced earth structures, described by the author, have now extended beyond retaining walls and bridge abutments to sea walls, dams and dykes. In such applications galvanised steel reinforcing strip, extending into compacted backfill, are attached to concrete facing panels. Friction developed between the reinforcement and the fill creates sufficient tensile stress to stablilise the entire mass. Dimensions of the reinforcing strips are designed so that the equivalent cross-section at the end of the anticipated life will be sufficient to withstand loads. Such structures are designed to distribute forces evenly within the mass so avoiding stress concentrations and the risk of sliding along the base. Concentrated loads are distributed by transferring shear forces in the fill to tensile forces in the reinforcement. A number of reinforced earth construction projects are described including bridge abutments, railway track beds and sea retaining walls. (TRRL)

Polymer grids and nets as soil reinforcement : Sweetland, D Civ Engng, London, March 1981, supplement, P30–P31

The author examines the use of polymer grids and nets used in soil reinforcement applications. Polymer meshes are increasingly being used for steep sided embankments over 15 M high for land recovery, slope protection and for gabion and mattress structures. Research in ground stabilization has shown that polymer grids are efficient for the reinforcement of granular sub-bases. Their use can reduce the depth of aggregate required to form a stable base. Grid structures, particularly those with high moduli, improve the performance of granular materials laid over soft sub-grades. A number of reinforced earth structures are mentioned which incorporate tensar geogrids. The work of the TRRL is also mentioned in which a motorway slip on the M4 was repaired using netlon geogrid and re-using existing soil to give cost savings of some 70000 pounds. (TRRL)

Discussion: Reinforced earth structures situated on soft foundations

Discussion: Reinforced earth structures situated on soft foundations

Fabric reinforced earth walls: Development of design equations : Murray, R T Ground Engng, V13, N7, Oct 1980, P29–36

The use of fabric as a reinforcing element for reinforced earth retaining structures is potentially attractive in view of its low cost, light weight and good durability. A few reinforced earth walls have been actually constructed using fabric but these have been mainly for experimental purposes. Current design methods for reinforced earth structures take no account of the magnitude of the strains induced in the tensile members as these are invariably manufactured from high modulus materials - such as steel - where strains are unlikely to be significant. With fabrics, however, large strains may frequently be induced and it is important to determine these to enable the suitability of the structure to be assessed. In this report design equations relating to the use of fabric in the reinforced earth application are developed. These equations take account of conventional force-equilibrium considerations as well as the influence of strain behaviour of the fabric. In addition, a procedure is outlined for specifying the strength characteristics of fabric which may provide a more convenient method for incorporating the fabric properties into the design equations. (Author/TRRL)

Reinforced earth structures situated on soft foundations. Technical note : Geotechnique, V30, N2, June 1980, P207–213

Reinforced earth structures situated on soft foundations. Technical note : Geotechnique, V30, N2, June 1980, P207–213

Reinforced earth structures situated on soft foundations

The authors investigate weaknesses in some current empirical design studies when used with structures situated on poor ground. Although it is theoretically possible to show that conventional earth retaining structures should be better suited to sites with poor bearing pressure capacity than reinforced earth structures, this is not generally the case in practical experience. A series of parametric studies using common material properties and an embankment height of 9 M have been undertaken using the program felsta to illustrate the properties of soft and very soft foundations. The effect of the width of the embankment or reinforced earth structure on overall stability is also investigated. It is concluded that the resistance to movement of the reinforced earth structure produced by the subsoil material radically alters the assumption that the structure will rotate forward about the toe. An expression for the stability of the structure is determined. Empirical design rules are only acceptable for narrow embankments. (TRRL)

World-wide development and use of reinforced earth structures : McKittrick, D P; Darbin, M Ground Engng, V12, N2, March 1979, P15–21

World-wide development and use of reinforced earth structures : McKittrick, D P; Darbin, M Ground Engng, V12, N2, March 1979, P15–21

Corrosion in reinforced earth structures : Ground Engng, V11, N7, Oct 1978, P39–40

An introduction to the fundamentals of soil corrosion is given. The factors which affect the corrosion of metallic reinforcements in reinforced earth structures are outlined and major areas of risk in structures identified. A brief outline is given of the TRRL sponsored research programme into corrosion problems in reinforced earth structures. /Author/

Use of FRP as reinforcing elements in reinforced soil systems : Ground Engng, V11, N7, Oct 1978, P19–22

Fibreglass Reinforced Plastics (FRP) based on chemically resistant thermosetting resins and undirectionally aligned glass fibres appear to have a useful combination of high strength and good corrosion properties which suit the material for use as reinforcement in soil structures. This paper outlines some properties of FRP straps including their frictional, strength, and corrosion behaviour and in particular the work carried out to establish their long-term durability. Additionally the strain distributions measured along FRP straps in an experimental reinforced earth structure are presented. /Author/

Performance of a reinforced earth structure at granton : Ground Engng, V11, N7, Oct 1978, P42–44

The performance is reported of a wall 106m long, between 1.8m and 7.2m high and partly curved in plan. Details of the wall and measurements made during and after construction are given. The measurements indicate the important role played by the construction operations on the performance of a reinforced earth wall, and particularly the effect of compaction carried out close to the wall panels. The measurements indicate the vertical and horizontal movement and the stresses set up within the reinforcing strips. The total vertical movement was 35mm. It was presumably caused by compression of the packing in the horizontal joints caused by self weight of the panels and downdrag of the fill behind the wall. Analysis of the measurements showed that the horizontal movement was made up of 2 components: horizontal movement at the joints, and tilt of the panels. The overall outward tilt of the completed wall at the test section was 2.3%. The measured values of tensile stress are shown in figures, and several points noted from the observations are recorded.

Reinforced earth — Practical construction techniques : Ground Engng, V11, N7, Oct 1978, P24–26, 37

The author illustrates the three methods of constructing reinforced earth structures: the concertina, telescope and sliding (York) methods. Examples are given of their use and their relative merits are discussed. In Britain a derivation of the concertina method is only used for temporary site works, although it is proposed to construct walls in Yorkshire with an acceptable appearance using fabric reinforcement. Details are given of the operational sequence and factors of importance in the York method of construction using lightweight material. Differences in the constructional sequence when a structural facing is used are discussed. Details are also given of base, drainage and capping methods. The ease of maintenance should be considered during the design stage including the replacement of hexagon facing units and top drainage. The author suggests that the design theories for the loads applied to the facing by the fill may be incomplete. /TRRL/

Reinforced earth structures on loose soils : In French. Conference. Session four. 9F, 3R. PROC. EIGHTH INT. CONF. ON SOIL MECH. FOUND. ENGNG. MOSCOW, V2.2, 1973, P201–205

Reinforced earth structures on loose soils : In French. Conference. Session four. 9F, 3R. PROC. EIGHTH INT. CONF. ON SOIL MECH. FOUND. ENGNG. MOSCOW, V2.2, 1973, P201–205