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3 RESULTS OF MODEL TESTS UNDER STATIC LOADING Three-dimensional well-instrumented model tests in a scale of 1:3 were carried out to investigate the bearing and deformation behaviour and to check and verify the concept and theory mentioned above. A group of four piles was placed in a weak soil of peat in a rectangular grid, above which a reinforced or unreinforced sand fill was placed in different heights (Fig. 4). Figure 4 Typical 1:3 scale test arrangement (ZAESKE, 2001) The stress distribution in the reinforced sand layer was recorded by pressure cells. The part of the load carried by the piles was measured by load-cells and allowed a comparison with the measured stress field in the sand. Under static loading the dependency of the stress transfer on geometric boundary conditions and the shear strength of the sand fill was verified. Figure 5 Test results versus analytical model (ZAESKE, 2001) Vertical rod extensometers to monitor settlements beneath the geogrid and strain measurements in the geogrid reinforcement confirmed the membrane effect and allowed a localisation of the highest tension. The maximum strains were localised in the zone overspanning neighbouring piles (Fig. 6). Figure 6 Typical geogrid-strain distribution, predicted and measured values (ZAESKE, 2001) Similar to field measurements, the strains in the geogrid were found to be relatively small, provided that reaction stress of the underlying soil between the rigid pile elements is mobilised. In addition to the model tests, numerical investigations with the finite element method (FEM) were performed for static conditions. The evaluation of the FE-calculations resulted in further information on the stress distribution in the reinforcing layer and the resulting load transfer onto the piles. After these verifications, the new method became part of Chapter 6.9 of the new edition of the EBGEO (draft) and is explained in the following chapter. 4 DESIGN RECOMMENDATION IN CHAPTER 6.9 EBGEO (DRAFT) The design procedure recommended in Chapter 6.9 of the EBGEO (draft) (EMPFELHUNG 6.9 (2003)) is divided into two steps: In the first step the load/stress distribution in the embankment is evaluated without considering any geosynthetic reinforcement, which results in the vertical stresses on top of the piles (σx,a1) and on the soft subsoil between them (σx,a2). The analytical model is based on the lower bound theorem of the plasticity theory and results from predefined directions of the stress trajectories in the reinforced soil body (ZAESKE (2001, 2002)). According to the numerical and experimental results the stress in the reinforced embankment is divided into a zone, where the normal pressures at rest can be assumed, and an arching region, where the stress redistribution takes place (Fig. 4). Equation (1) shows the differential equation derived from the equilibrium of the forces of the three-dimensional soil element in radial direction (Figure 7). Figure 7 Geometry: "arching" and equilibrium of stresses (ZAESKE, 2001, 2002) The solution of the equation gives the vertical stress σx,a2 inside the arch. The vertical pressure on the soft soil σx,a3 results from the limit θ → 0, Equation (2). 4 DESIGN RECOMMENDATION IN CHAPTER 6.9 For more convenience, σx,a2 can also be derived from dimensionless design graphs e.g. (Figure 9 for χ = 30°). Figure 4 shows the calculated vertical stress distribution in comparison with results of the model tests In the second step, the vertical pressure σmax is applied to the geosynthetic reinforcement as external load. To predict the stresses in the reinforcement, an analytical model is applied based on the theory of elastically embedded membranes (ZAESKE (2001)). The maximum strain in reinforcement (i.e. the maximum tensile force) is concentrated in the band bridging two neighboured piles (despite the common engineering sense, it was confirmed by the experimental work as well). Therefore the analytical model assumes that the maximum stress in the geosynthetic membrane takes place within the width Δex, and may σx,a1 = γffx + γ" . β l . kn σx,a2 = rb . ((xi + ) k . (xi . µk ) 0.1 - [(bi1 + bi2 )i . xi + bi1 - xi ) )] + (k2b* - [bi1 + bki) bi3k ) - (bi1 + bi2 ) . ) ] + xi x.x = kn-1k . γwb3 * kn-1k . β b1 b2 ki 0.2d - 0.5 . d con = 1 - xi =1 eax-αa. b1 = α . k2c2 . - xi1 - 2k3. d - 0.2d b2 = ki . b2 . axi = ak1 . [x + kn-1)2b3 . p2 - d . kn2 b3 α.5 k32 = 5.2 - 0.2 d = 0.4 . d Figure 8 Vertical stress σx,a on the soft soil (EMPFELHUNG 6.9, 2003) For more convenience, σx. can also be derived from dimensionless design graphs e.g. (Figure 9 for χ = 30°). Figure 4 shows the calculated vertical stress distribution in comparison with results of the model tests p'k = 30° σd x,a1 = χ.' Nγp,i Figure 9 Typical graph for the vertical stress σx,a on the soft soil between "piles" (EMPFELHUNG 6.9, 2003) be calculated based on a planar system (Fig. 10). Biaxial geogrids must be analysed both in x- and y-direction. [diagram] Figure 10 Load transfer and simplified planar (2D) bearing system (ZAESKE, 2001, 2002) The resulting triangular vertical strip load Ft on the geogrid strip is calculated from the pressure σmax and the loaded area A (Fig. 11). [diagram] Figure 11 Calculation of the resulting force Ft assigned to the load influence area A. (EMPFEHLUNG 6.9, 2003) The influence of the bearing effect of the soft soil between piles is considered by using a modulus of subgrade reaction. A simplified approximation is given in Equation (3) for multiple soil layers; see EMPFEHLUNG 6.9 (2003). The maximum strain in the geosynthetic reinforcement results from the tensile stiffness EA of the geosynthetic, the modulus of subgrade reaction ks of the soft soil, the total vertical load Fv and the dimensions bse and L. Since all geosynthetics tend to creep, the tensile modulus EA is time-dependent and has to be read out from the real isochrones of the geosynthetic reinforcement; the latter is essential. In EMPFEHLUNG 6.9 (2003), the values of ε can respectively F can be out from a dimensionless design graph; see e.g., (Fig. 12). Finally, the tensile force in the reinforcement EA (M = membrane) can be calculated directly as a function of the strain of the geosynthetic, Equation (5). For two geosynthetic reinforcements the calculated force is divided with respect to the ratio of their tensile moduli. [graph] Figure 12 Maximum strain in the geosynthetic reinforcement (EMPFEHLUNG 6.9, 2003) The influence of an inclined surface of the reinforced embankment (typically slope) is illustrated in Figure 13. In addition to the membrane effect, geosynthetics are stressed by horizontal forces. The lateral thrust can be considered on the safer side assuming an active earth pressure condition without any support by "piles" or soft soil (BS 8006 (1995), ZAESKE (2001, 2002)). The concept is conservative. ΔFt = EAix ( ( δx – σmax - δ ) – aL ) – ks ( Φ ) [depth area] Figure 13 Additional horizontal force in the reinforcement beneath embankment slope (EMPFEHLUNG 6.9, 2003) [depth area] Figure 14 Distance z in the case of one and two reinforcement layers (EMPFEHLUNG 6.9, 2003) 5 CONSTRUCTION RECOMMENDATIONS IN CHAPTER 6.9 EBGEO Based on German and international experience with geosynthetic-reinforced pile-supported embankments, practical reasons, experimental results and the validity of the analytical model following recommendations are established: 5.1 Pile elements and spacing The center-to-center distance s and the pile diameter d of the piles resp. pile caps should be chosen as follows: (s - d) ≤ 3.50 m; resp. (s - b)s 3.00 m; in the case of elastic subgrade (s - d) ≤ 2.5 m; resp. (s - b)s 2.5; in the case of heavily live loads d / z ≤ 0.15 netp. bl / z ≤ 0,15 (s - d )/(1-d) > 2 The value of ks = modulus of subgrade reaction between the pile elements and the surrounding soft soil shall ks / k0 > 700 (to ensure full “arching” and structural efficiency in the design); normally, conventional pile-systems fulfil this condition. 5.2 Geosynthetic reinforcement The distance between the reinforcement layer and the plane of the pile/column/wall heads should be as small as possible, in order to achieve maximum efficiency of the geosynthetic membrane. However, it is recommended to have a safe distance (interlayer) between the lowest reinforcement and the pile heads in order to prevent a structural damage of the reinforcement because of shearing at the edge of the pile heads. maximum two reinforcement layers (Fig. 14) z < 0.15 m for single layer reinforcement z < 0.30 m for two layers reinforcement for two layers the distance between the geosynthetic layers should be 15 to 30 cm design value of the tensile strength Fku ≥ 330 kN/m; ultimate strain ≤ 12 % Overlapping is generally allowed, but only just above the piles (caps) and only in the secondary bearing direction; length of overlapping ≥ d. 5.3 Embankment For the embankment a cohesionless fill should be used. The angle of internal friction φ should be greater than 30°. Use of low-cohesion soils is also permitted, but not preferred. (Note: A general issue to be always kept in mind is if the soft soil upward counter-pressure will be available for the entire design life. Not-supported situations should be checked additionally.) 6 FINAL REMARKS AND FUTURE PROSPECTS Geosynthetic-reinforced embankments on point- or line shaped bearing elements (“piles”) provide an economical and effective solution for embankments constructed on soft soil, especially when rapid construction and strict deformation of the structure are required. To examine the bearing effect of the system, large scale model tests and numerical investigations were carried out. Based on these results a theoretical model was developed, which describes the stress-distribution in the embankment and the membrane effect of the geosynthetic reinforcement. The developed design procedure is introduced in the recommendation “Chapter 6.9 - Reinforced soil structures above point - or line shaped bearing elements”, which has now been approved as a draft for public. Chapter 6.9 will be soon part of the new edition of the EBGEO (German Recommendations for Geosynthetic Reinforcement) The design method provides a realistic approximation of the bearing behaviour of the composite structure under static loading and represents a new State-of-the-Art. Comparisons of the analytical results with model test data and field measurements demonstrate that the new design model still leads to a conservative prediction of the bearing behavior, at least so far as counter-pressure from the soft soil is available. Recommendations regarding geometry, soils, reinforcement and construction are given as well. At present, a research project is in progress at the Institute of Geotechnics, University of Kassel, which examines the behaviour of such systems under cyclic loading. The first model tests show that the arching effect was confirmed in a very limited amount and the part of the load carried directly by the piles decreased remarkably, which resulted in an increase of the load on the soft soil and/or in the reinforcement. Due to the reduction of the arching effect, the strains in the geogrid and the settlements of the surface increase considerably. Because such negative effects of service load have been suspected earlier due to common sense, a quasi-elastic approach was suggested in KEMPFER (1997) by applying an additional increasing partial factor to traffic loads, which at present an acceptable compromise. Nevertheless the bearing behavior and the settlements expected under cyclic load are not yet fully explained. The further research required for that specific important issue and is ongoing. 7 REFERENCE Alexiew, D., Vogel, W., 2001: Railroads on piled embankments in Germany: Milestone projects. In: Landmarks in Earth Reinforcement, Swets & Zeitlinger, 2001, pp. 185-190 Alexiew, D., Gertung, E., 1999: Geogrid reinforced railway embankment ab test site — performance monitoring 1994;1998. Proc. 7th Int. Sympnonium on Geosynthetics, '99, Die 30 juin et vendredi, 1999, pp. 403-411 Hewlett, W.J., Randolph, M.F., 1988: Analysis of piled embankments, Ground Engineering, Vol.21, pp. 12-17 BS: 1995: Code of practice for Strengthened/Reinforced Soils and other Fills. British Standard Institution. Kempfert, H.G., Sai'ada, M., Ziegeler, DH 1997: Berechnung von geogitgestütUen, über CFP hatgut.g unterstützten, über Pfahlanhämten. Bautechnik, Jahrgang 74, Heft 12, pp.815-825 Neculescu, A., 2002: Filed embankments: methods and case histories. Convegno nelii'appal fogaligiesuil: metodologia ed esempi realizzati. Proc. XV Italian Conference on Geotechnical, Bologna, 16 October 2002 Kempfert, H.G., Zakshe, D., Alexiew, D., 1999: Interactions in the interface: load bearing layers on partial supported underground, Proc. of the 12th ECSMFE, Amsterdam, 1999. Balkema, Rotterdam, 1999, pp. 1527-1532 Zandertion, J., Richter, R., 2002: Nachweissee von unbewehrten und bewehrten mario PhäIenlagelüng, gewagklichen üben! philärlatn Grün!-üëmten. iii: Kolloquium von Read the Geotechnik, Universitäten Geotechnik, Innsbruck, 16. April 2002 Zakshe, D., Kempfert, H.G., 2002: Berechnung und Wirkungswage geogrid-bewrackten an beuihemt lewatmen traggliederan. Bauwesen, > 06/2002 Empfehlungen: Paheffenkörper auf punkt- oder Ihtertlüftmfferten Gnmodienlagen. Euroherpung zur Geosdflatenstoffen (EBGEO) (Draft of Chapter 6.9 of the new edition of the German Recommendations for Geosynthetic Reinforcement, September 2003).
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3 RESULTS OF MODEL TESTS UNDER STATIC LOADING Three-dimensional well-instrumented model tests in a scale of 1:3 were carried out to investigate the bearing and deformation behaviour and to check and verify the concept and theory mentioned above. A group of four piles was placed in a weak soil of peat in a rectangular grid, above which a reinforced or unreinforced sand fill was placed in different heights (Fig. 4). Figure 4 Typical 1:3 scale test arrangement (ZAESKE, 2001) The stress distribution in the reinforced sand layer was recorded by pressure cells. The part of the load carried by the piles was measured by load-cells and allowed a comparison with the measured stress field in the sand. Under static loading the dependency of the stress transfer on geometric boundary conditions and the shear strength of the sand fill was verified. Figure 5 Test results versus analytical model (ZAESKE, 2001) Vertical rod extensometers to monitor settlements beneath the geogrid and strain measurements in the geogrid reinforcement confirmed the membrane effect and allowed a localisation of the highest tension. The maximum strains were localised in the zone overspanning neighbouring piles (Fig. 6). Figure 6 Typical geogrid-strain distribution, predicted and measured values (ZAESKE, 2001) Similar to field measurements, the strains in the geogrid were found to be relatively small, provided that reaction stress of the underlying soil between the rigid pile elements is mobilised. In addition to the model tests, numerical investigations with the finite element method (FEM) were performed for static conditions. The evaluation of the FE-calculations resulted in further information on the stress distribution in the reinforcing layer and the resulting load transfer onto the piles. After these verifications, the new method became part of Chapter 6.9 of the new edition of the EBGEO (draft) and is explained in the following chapter. 4 DESIGN RECOMMENDATION IN CHAPTER 6.9 EBGEO (DRAFT) The design procedure recommended in Chapter 6.9 of the EBGEO (draft) (EMPFELHUNG 6.9 (2003)) is divided into two steps: In the first step the load/stress distribution in the embankment is evaluated without considering any geosynthetic reinforcement, which results in the vertical stresses on top of the piles (σx,a1) and on the soft subsoil between them (σx,a2). The analytical model is based on the lower bound theorem of the plasticity theory and results from predefined directions of the stress trajectories in the reinforced soil body (ZAESKE (2001, 2002)). According to the numerical and experimental results the stress in the reinforced embankment is divided into a zone, where the normal pressures at rest can be assumed, and an arching region, where the stress redistribution takes place (Fig. 4). Equation (1) shows the differential equation derived from the equilibrium of the forces of the three-dimensional soil element in radial direction (Figure 7). Figure 7 Geometry: "arching" and equilibrium of stresses (ZAESKE, 2001, 2002) The solution of the equation gives the vertical stress σx,a2 inside the arch. The vertical pressure on the soft soil σx,a3 results from the limit θ → 0, Equation (2). 4 DESIGN RECOMMENDATION IN CHAPTER 6.9 For more convenience, σx,a2 can also be derived from dimensionless design graphs e.g. (Figure 9 for χ = 30°). Figure 4 shows the calculated vertical stress distribution in comparison with results of the model tests In the second step, the vertical pressure σmax is applied to the geosynthetic reinforcement as external load. To predict the stresses in the reinforcement, an analytical model is applied based on the theory of elastically embedded membranes (ZAESKE (2001)). The maximum strain in reinforcement (i.e. the maximum tensile force) is concentrated in the band bridging two neighboured piles (despite the common engineering sense, it was confirmed by the experimental work as well). Therefore the analytical model assumes that the maximum stress in the geosynthetic membrane takes place within the width Δex, and may σx,a1 = γffx + γ" . β l . kn σx,a2 = rb . ((xi + ) k . (xi . µk ) 0.1 - [(bi1 + bi2 )i . xi + bi1 - xi ) )] + (k2b* - [bi1 + bki) bi3k ) - (bi1 + bi2 ) . ) ] + xi x.x = kn-1k . γwb3 * kn-1k . β b1 b2 ki 0.2d - 0.5 . d con = 1 - xi =1 eax-αa. b1 = α . k2c2 . - xi1 - 2k3. d - 0.2d b2 = ki . b2 . axi = ak1 . [x + kn-1)2b3 . p2 - d . kn2 b3 α.5 k32 = 5.2 - 0.2 d = 0.4 . d Figure 8 Vertical stress σx,a on the soft soil (EMPFELHUNG 6.9, 2003) For more convenience, σx. can also be derived from dimensionless design graphs e.g. (Figure 9 for χ = 30°). Figure 4 shows the calculated vertical stress distribution in comparison with results of the model tests p'k = 30° σd x,a1 = χ.' Nγp,i Figure 9 Typical graph for the vertical stress σx,a on the soft soil between "piles" (EMPFELHUNG 6.9, 2003) be calculated based on a planar system (Fig. 10). Biaxial geogrids must be analysed both in x- and y-direction. [diagram] Figure 10 Load transfer and simplified planar (2D) bearing system (ZAESKE, 2001, 2002) The resulting triangular vertical strip load Ft on the geogrid strip is calculated from the pressure σmax and the loaded area A (Fig. 11). [diagram] Figure 11 Calculation of the resulting force Ft assigned to the load influence area A. (EMPFEHLUNG 6.9, 2003) The influence of the bearing effect of the soft soil between piles is considered by using a modulus of subgrade reaction. A simplified approximation is given in Equation (3) for multiple soil layers; see EMPFEHLUNG 6.9 (2003). The maximum strain in the geosynthetic reinforcement results from the tensile stiffness EA of the geosynthetic, the modulus of subgrade reaction ks of the soft soil, the total vertical load Fv and the dimensions bse and L. Since all geosynthetics tend to creep, the tensile modulus EA is time-dependent and has to be read out from the real isochrones of the geosynthetic reinforcement; the latter is essential. In EMPFEHLUNG 6.9 (2003), the values of ε can respectively F can be out from a dimensionless design graph; see e.g., (Fig. 12). Finally, the tensile force in the reinforcement EA (M = membrane) can be calculated directly as a function of the strain of the geosynthetic, Equation (5). For two geosynthetic reinforcements the calculated force is divided with respect to the ratio of their tensile moduli. [graph] Figure 12 Maximum strain in the geosynthetic reinforcement (EMPFEHLUNG 6.9, 2003) The influence of an inclined surface of the reinforced embankment (typically slope) is illustrated in Figure 13. In addition to the membrane effect, geosynthetics are stressed by horizontal forces. The lateral thrust can be considered on the safer side assuming an active earth pressure condition without any support by "piles" or soft soil (BS 8006 (1995), ZAESKE (2001, 2002)). The concept is conservative. ΔFt = EAix ( ( δx – σmax - δ ) – aL ) – ks ( Φ ) [depth area] Figure 13 Additional horizontal force in the reinforcement beneath embankment slope (EMPFEHLUNG 6.9, 2003) [depth area] Figure 14 Distance z in the case of one and two reinforcement layers (EMPFEHLUNG 6.9, 2003) 5 CONSTRUCTION RECOMMENDATIONS IN CHAPTER 6.9 EBGEO Based on German and international experience with geosynthetic-reinforced pile-supported embankments, practical reasons, experimental results and the validity of the analytical model following recommendations are established: 5.1 Pile elements and spacing The center-to-center distance s and the pile diameter d of the piles resp. pile caps should be chosen as follows: (s - d) ≤ 3.50 m; resp. (s - b)s 3.00 m; in the case of elastic subgrade (s - d) ≤ 2.5 m; resp. (s - b)s 2.5; in the case of heavily live loads d / z ≤ 0.15 netp. bl / z ≤ 0,15 (s - d )/(1-d) > 2 The value of ks = modulus of subgrade reaction between the pile elements and the surrounding soft soil shall ks / k0 > 700 (to ensure full “arching” and structural efficiency in the design); normally, conventional pile-systems fulfil this condition. 5.2 Geosynthetic reinforcement The distance between the reinforcement layer and the plane of the pile/column/wall heads should be as small as possible, in order to achieve maximum efficiency of the geosynthetic membrane. However, it is recommended to have a safe distance (interlayer) between the lowest reinforcement and the pile heads in order to prevent a structural damage of the reinforcement because of shearing at the edge of the pile heads. maximum two reinforcement layers (Fig. 14) z < 0.15 m for single layer reinforcement z < 0.30 m for two layers reinforcement for two layers the distance between the geosynthetic layers should be 15 to 30 cm design value of the tensile strength Fku ≥ 330 kN/m; ultimate strain ≤ 12 % Overlapping is generally allowed, but only just above the piles (caps) and only in the secondary bearing direction; length of overlapping ≥ d. 5.3 Embankment For the embankment a cohesionless fill should be used. The angle of internal friction φ should be greater than 30°. Use of low-cohesion soils is also permitted, but not preferred. (Note: A general issue to be always kept in mind is if the soft soil upward counter-pressure will be available for the entire design life. Not-supported situations should be checked additionally.) 6 FINAL REMARKS AND FUTURE PROSPECTS Geosynthetic-reinforced embankments on point- or line shaped bearing elements (“piles”) provide an economical and effective solution for embankments constructed on soft soil, especially when rapid construction and strict deformation of the structure are required. To examine the bearing effect of the system, large scale model tests and numerical investigations were carried out. Based on these results a theoretical model was developed, which describes the stress-distribution in the embankment and the membrane effect of the geosynthetic reinforcement. The developed design procedure is introduced in the recommendation “Chapter 6.9 - Reinforced soil structures above point - or line shaped bearing elements”, which has now been approved as a draft for public. Chapter 6.9 will be soon part of the new edition of the EBGEO (German Recommendations for Geosynthetic Reinforcement) The design method provides a realistic approximation of the bearing behaviour of the composite structure under static loading and represents a new State-of-the-Art. Comparisons of the analytical results with model test data and field measurements demonstrate that the new design model still leads to a conservative prediction of the bearing behavior, at least so far as counter-pressure from the soft soil is available. Recommendations regarding geometry, soils, reinforcement and construction are given as well. At present, a research project is in progress at the Institute of Geotechnics, University of Kassel, which examines the behaviour of such systems under cyclic loading. The first model tests show that the arching effect was confirmed in a very limited amount and the part of the load carried directly by the piles decreased remarkably, which resulted in an increase of the load on the soft soil and/or in the reinforcement. Due to the reduction of the arching effect, the strains in the geogrid and the settlements of the surface increase considerably. Because such negative effects of service load have been suspected earlier due to common sense, a quasi-elastic approach was suggested in KEMPFER (1997) by applying an additional increasing partial factor to traffic loads, which at present an acceptable compromise. Nevertheless the bearing behavior and the settlements expected under cyclic load are not yet fully explained. The further research required for that specific important issue and is ongoing. 7 REFERENCE Alexiew, D., Vogel, W., 2001: Railroads on piled embankments in Germany: Milestone projects. In: Landmarks in Earth Reinforcement, Swets & Zeitlinger, 2001, pp. 185-190 Alexiew, D., Gertung, E., 1999: Geogrid reinforced railway embankment ab test site — performance monitoring 1994;1998. Proc. 7th Int. Sympnonium on Geosynthetics, '99, Die 30 juin et vendredi, 1999, pp. 403-411 Hewlett, W.J., Randolph, M.F., 1988: Analysis of piled embankments, Ground Engineering, Vol.21, pp. 12-17 BS: 1995: Code of practice for Strengthened/Reinforced Soils and other Fills. British Standard Institution. Kempfert, H.G., Sai'ada, M., Ziegeler, DH 1997: Berechnung von geogitgestütUen, über CFP hatgut.g unterstützten, über Pfahlanhämten. Bautechnik, Jahrgang 74, Heft 12, pp.815-825 Neculescu, A., 2002: Filed embankments: methods and case histories. Convegno nelii'appal fogaligiesuil: metodologia ed esempi realizzati. Proc. XV Italian Conference on Geotechnical, Bologna, 16 October 2002 Kempfert, H.G., Zakshe, D., Alexiew, D., 1999: Interactions in the interface: load bearing layers on partial supported underground, Proc. of the 12th ECSMFE, Amsterdam, 1999. Balkema, Rotterdam, 1999, pp. 1527-1532 Zandertion, J., Richter, R., 2002: Nachweissee von unbewehrten und bewehrten mario PhäIenlagelüng, gewagklichen üben! philärlatn Grün!-üëmten. iii: Kolloquium von Read the Geotechnik, Universitäten Geotechnik, Innsbruck, 16. April 2002 Zakshe, D., Kempfert, H.G., 2002: Berechnung und Wirkungswage geogrid-bewrackten an beuihemt lewatmen traggliederan. Bauwesen, > 06/2002 Empfehlungen: Paheffenkörper auf punkt- oder Ihtertlüftmfferten Gnmodienlagen. Euroherpung zur Geosdflatenstoffen (EBGEO) (Draft of Chapter 6.9 of the new edition of the German Recommendations for Geosynthetic Reinforcement, September 2003).