Influence of Soil Fabric and Gradation on Excess Pore Water Pressure Development Based on Laboratory PWP Tester Božana Baćić, Ivo Herle Geotechnical and Geological Engineering, 2026 The build-up of the excess pore water pressure (PWP) during shearing under constant total stresses can significantly influence the stability and performance of geotechnical structures, particularly in coarse grained soils under cyclic and dynamic loading conditions. This study investigates the role of soil fabric and granulometric properties in the generation of the excess PWP using a newly developed PWP Tester. Series of experiments were conducted on both natural and crushed sands with varying grain size distributions, grain shapes, and particle orientations. The results indicate that the resistance to the excess PWP build-up in natural soils increases with larger mean grain diameter and a reduced amount of fines, while crushed sand with narrower grain size distribution show a slight increase in resistance to the excess PWP development. Furthermore, the findings suggest that soil resistance to the excess PWP cannot be adequately captured by solely considering the relative density, and that the soil fabric plays an equally significant role. This study contributes to a deeper understanding of the soil behaviour under cyclic loading in undrained conditions, offering a simple and straightforward method for testing the soil tendency to the excess PWP evolution.
Experimental studies on the cyclic behaviour of reinforced unbound railway base courses Claudia Bräunig, Ivo Herle, Ulrike Weisemann E3s Web of Conferences, 2025 In railway construction, base courses of unbound coarse-grained material are usually placed between the existing subgrade and the track. Geosynthetics, in particular geogrids, are used to improve the system behaviour. The reduction in the thickness of the base course due to the geogrid is based on empirical approaches. In this work triaxial tests were performed to investigate the influence of the geogrid. A specimen size of d · h = 100 · 200 mm was chosen. This small sample size saved material, reduced workload and allowed the use of a standard triaxial apparatus. However, the base course material and the geogrid had to be geometrically scaled. Cyclic triaxial tests were carried out on the unreinforced and reinforced specimens with the aim to reproduce the conditions caused by rail traffic loading. For this purpose, the low stress and high number of loading cycles N = 500,000 were chosen. It was shown that the inserted geogrid reduces the magnitude of deformation and the accumulated strains compared to the unreinforced material.
Triaxial Compression of Sand-Fines Mixtures at Low Confining Pressures Sebastian Ullmann, Selma Schmidt, Ivo Herle Geotechnical and Geological Engineering, 2025 A series of triaxial compression tests was performed on a natural sand-fines mixture under both drained and undrained conditions at initial confining pressures ranging from 20 to 300 kPa. The tests aimed to better understand the mechanical behaviour of the soil at low stress levels. Additionally, images of the soil fabric were taken using a µCT device, revealing that the fabric was characterised by the sand grains being fully embedded within the fine-grained matrix and that only few direct contacts between the sand grains existed. The results of the triaxial tests showed that the fabric of the sand-fines mixture significantly influenced the macroscopic properties of the specimens when compared to clean sands. In the drained triaxial tests, the dilatancy and friction angles showed minimal dependence on the confining pressure, even at pressures below 60 kPa. The undrained triaxial tests showed different response patterns in the development of excess pore water pressure. Tests starting from lower confining pressures resulted in a greater build-up of pore water pressure after reaching the phase transition line, whereas at higher confining pressures the soil exhibited lower excess pore water pressures.
Soil fabric of coarse-grained soils sedimented under water and its relation to relative density and excess pore water pressure Božana Baćić, Ivo Herle, Martin Oppermann Granular Matter, 2025 The soil fabric varies significantly depending on the deposition process that forms the grain skeleton. Each deposition method produces a specific type of soil fabric, which can be linked to a particular soil density. When represented as relative density, determined using limit densities from standard index tests, a wide range of relative densities can be observed for different sands produced by the same deposition method. The influence of this variation in relative density, resulting from a single deposition method, on the development of the excess pore water pressure (PWP) should be further investigated. A fast testing of the excess PWP accumulation in sandy soils during undrained cyclic shearing can be easily performed using the newly developed PWP Tester. In the PWP Tester, specimens are prepared through sedimentation in water, which yields a comparable fabric in different sands but significantly different relative densities. Despite these relative density differences, the rate of the excess PWP evolution during undrained shearing is remarkably similar among different sands. This indicates that relative density should not be regarded as a primary factor influencing the development of the excess PWP and that the soil fabric plays equal or even a greater role.
Scaling effects under monotonic shear loading on unbound reinforced base courses Claudia Bräunig, Ivo Herle, Tom Schulze, Ulrike Weisemann Geotechnik, 2025 Durch den Einsatz von Geogittern in ungebundenen Tragschichten können die Tragfähigkeits‐ und Gebrauchstauglichkeitseigenschaften verbessert werden. Um die Tragwirkung dieses Verbundsystems zu analysieren, wurden Triaxial‐ und Rahmenscherversuche durchgeführt, in welchen die Auswirkung der Skalierung der Versuchsmaterialien Tragschichtmaterial und Geogitter unter monotoner Scherbeanspruchung untersucht wurde. Bei der Untersuchung des Systems Tragschicht – Geogitter mittels bodenmechanischer Versuche werden aufgrund der begrenzten Probenabmessungen häufig kleinere Öffnungsweiten des Geogitters und kleinere Korngrößen des Tragschichtmaterials gegenüber denen in der Baupraxis verwendet. Bei der Übertragung der Ergebnisse sind Skalierungseffekte zu beachten, welche in der vorliegenden Arbeit untersucht werden. In den Triaxialversuchen wurde das Verhältnis der Öffnungsweite des Geogitters zur Korngröße beibehalten, es wurden zwei Tragschichtmaterialien untersucht. In beiden Skalierungen führte der Einsatz von Geogittern im Tragschichtmaterial zu einer Verbesserung der Tragfähigkeit durch eine Erhöhung der maximal aufnehmbaren Spannung. In den Rahmenscherversuchen wurde das Verhältnis zwischen Öffnungsweite des Geogitters und Korngröße verändert. Die Versuche mit bewehrten Proben führten bei parallel zur Scherrichtung gewählter Anordnung des Geogitters im Scherspalt zu geringeren aufnehmbaren Scherspannungen.
Heterogeneous and scale-dependent behaviour of an initially dense sand specimen in triaxial compression Selma Schmidt, Ivo Herle Granular Matter, 2025 The heterogeneity of a dense sand specimen in triaxial compression has been revealed in many different studies using tools such as x-ray computed tomography. It has been shown that a significant variation of the soil variables already exists at the initial state and that, if shear banding occurs, all variables localise inside the specimen. To resolve the discrepancy between such observations and the assumption of a homogeneous specimen, which is commonly made in the interpretation of triaxial tests, one could either extract the local soil behaviour rather than the global one or use the initial distribution of the variables as the initial state of a boundary value problem. For both purposes, the size of a representative elementary volume (REV) is determined regarding the void ratio, two contact fabric descriptors, the volumetric and deviatoric strain. The size of the REV is either determined for individual loading states or by considering the evolution of deforming elements throughout the triaxial test. At the final loading state, a REV size of 3.6 $$d_{50}$$ is identified, which is also the size where the statistical distribution of the variables becomes independent of the element size. The same size is determined for the deforming elements and is therefore used to extract the soil behaviour from the evolving shear band. The local soil behaviour is found to be much simpler than the global one, which suggests that the complexity of the global behaviour mainly results from homogenising the highly different zones inside the specimen. Graphical Abstract Extraction of the soil behaviour inside the evolving shear band with the help of deforming representativeelementary volumes. The volumetric behaviour is represented by the evolution of the void ratio and the evolution ofthe contact fabric anisotropy is closely connected to the stress-strain behaviour. The soil behaviour on the REVscale might form the basis for an alternative approach for the development and calibration of constitutive modelsconsidering the heterogeneity of a soil specimen.
EVOLUTION OF FABRIC AND STRAIN WITHIN REPRESENTATIVE ELEMENTARY VOLUMES INSIDE A SHEAR BAND BY TRACKING GRAINS OF A SAND SPECIMEN IN TRIAXIAL COMPRESSION S. Schmidt, I. Herle Iop Conference Series Earth and Environmental Science, 2025 It has been shown in several different studies that the behaviour of sands in triaxial tests is, in contrast to common assumptions, not homogeneous and that, after the localisation of strain, most of the soil behaviour takes place inside the shear band. In this work, the evolution of fabric and strain is extracted from the evolving shear band with the help of representative elementary volumes (REV) and compared with other regions inside the specimen as well as the overall behaviour. The size of the REV is determined by analysing the evolution of the fabric variables and the strain inside cubic elements with increasing size. For this purpose, a set of grains is assigned to the elements at the initial state and the grains are tracked throughout the test. The REV is then placed in different regions of the specimen and the evolution inside and outside the shear band as well as the global behaviour is compared.
INFLUENCE OF SAND FABRIC ON PORE WATER PRESSURE BUILD-UP B. Baćić, I. Herle Iop Conference Series Earth and Environmental Science, 2025 The sand fabric is created depending on the art of the grain deposition. A certain deposition method creates a specific type of soil fabric that can be linked to a particular soil density which, when related to the limit density states obtained from the standard index tests, can vary within a large range for different sands prepared by the same method. This paper aims to clarify the impact of varying the relative density in the case of one deposition method on the pore water pressure (PWP) accumulation in sands. A simplified cyclic shear test (PWP Tester) enabling a fast testing of the PWP accumulation during undrained cyclic shearing in granular soils is used for this purpose. The tested specimens are pluviated under water via a funnel and thus have a similar fabric. The results show a greatly comparable rate of PWP accumulation during undrained shearing, despite the fact that the relative densities following the same soil deposition vary greatly for different soils.
Identification and evaluation of uncertainty sources of materials and sensors for the digital twin road initiative A Chihadeh, M Böttcher, D Crampen, E Kamratowsky, M Hagmanns, ... Structure and Infrastructure Engineering, 1-18 , 2026 2026
Influence of Soil Fabric and Gradation on Excess Pore Water Pressure Development Based on Laboratory PWP Tester B Baćić, I Herle Geotechnical and Geological Engineering 44 (2), 88 , 2026 2026 Citations: 1
Sand-anchors, theory and application: Sandanker, Theorie und Anwendung SB Stazhevsky, D Kolymbas, I Herle Anchors in Theory and Practice/Anker in Theorie Und Praxis, 367-371 , 2026 2026
Incorporation of a hypoplastic material model for sandy soils into a dynamic ALE formulation suitable for structures subjected to moving loads A Anantheswar, S Ullmann, I Wollny, S Skatulla, I Herle, M Kaliske Transportation Geotechnics, 101876 , 2025 2025
Triaxial compression of sand-fines mixtures at low confining pressures S Ullmann, S Schmidt, I Herle Geotechnical and Geological Engineering 43 (6), 267 , 2025 2025 Citations: 8
Soil fabric of coarse-grained soils sedimented under water and its relation to relative density and excess pore water pressure B Baćić, I Herle, M Oppermann Granular Matter 27 (3), 65 , 2025 2025
Influence of Sand Fabric on Pore Water Pressure Build-Up B Baćić, I Herle IOP Conference Series: Earth and Environmental Science 1480 (1), 012001 , 2025 2025
Evolution of Fabric and Strain within Representative Elementary Volumes Inside A Shear Band by Tracking Grains of a Sand Specimen in Triaxial Compression S Schmidt, I Herle IOP Conference Series: Earth and Environmental Science 1480 (1), 012067 , 2025 2025
Skalierungseffekte bei monotoner Scherbeanspruchung von ungebundenen bewehrten Tragschichten C Bräunig, I Herle, T Schulze, U Weisemann geotechnik 48 (1), 3-15 , 2025 2025
Heterogeneous and scale-dependent behaviour of an initially dense sand specimen in triaxial compression: S. Schmidt, I. Herle S Schmidt, I Herle Granular Matter 27 (1), 24 , 2025 2025
Considering realistic soil behaviour in numerical simulations of the road S Ullmann, I Herle # PLACEHOLDER_PARENT_METADATA_VALUE# 4, 189-192 , 2025 2025 Citations: 1
Experimental studies on the cyclic behaviour of reinforced unbound railway base courses C Bräunig, I Herle, U Weisemann E3S Web of Conferences 644, 03010 , 2025 2025
Build-Up of Pore Water Pressure in Coarse-Grained Soils of Similar Fabric I Herle, B Bacic Recent Developments of Soil Mechanics and Geotechnics in Theory and Practice … , 2024 2024
Build-Up of Pore Water Pressure in I Herle, B Bacic Recent Developments of Soil Mechanics and Geotechnics in Theory and Practice, 48 , 2024 2024
Experimentelle Untersuchungen zum Einfluss von Geogittern in ungebundenen Tragschichten C Bräunig, I Herle, U Weisemann geotechnik 47 (3), 155-165 , 2024 2024 Citations: 2
A simplified cyclic shear test for pore water pressure build-up of different soils B Baćić, I Herle E3S Web of Conferences 544, 01002 , 2024 2024
Characterisation of the heterogeneity of a sand specimen in triaxial compression using x-ray CT and representative elementary volumes S Schmidt, M Wiebicke, I Herle E3S Web of Conferences 544, 04003 , 2024 2024 Citations: 1
A simplified cyclic shear test for pore water pressure build-up in sands B Bacic, I Herle Japanese Geotechnical Society Special Publication 10 (56), 2122-2127 , 2024 2024
Vereinfachter zyklischer Scherversuch zum PWD‐Aufbau in grobkörnigen Böden B Bacic, I Herle geotechnik 46 (4), 210-219 , 2023 2023 Citations: 3
Density-dependent pore water pressure evolution in a simplified cyclic shear test B Baćić, I Herle International Journal of Geosynthetics and Ground Engineering 9 (4), 47 , 2023 2023 Citations: 11
MOST CITED SCHOLAR PUBLICATIONS
Hypoplastic model for cohesionless soils with elastic strain range A Niemunis, I Herle Mechanics of Cohesive‐frictional Materials: An International Journal on … , 1997 1997 Citations: 1366
Determination of parameters of a hypoplastic constitutive model from properties of grain assemblies I Herle, G Gudehus Mechanics of Cohesive‐frictional Materials: An International Journal on … , 1999 1999 Citations: 797
Hypoplastizität und granulometrie einfacher korngerüste I Herle Inst. für Bodenmechanik und Felsmechanik , 1997 1997 Citations: 258
The soilmodels. info project G Gudehus, A Amorosi, A Gens, I Herle, D Kolymbas, D Mašín, ... International Journal for Numerical and Analytical Methods in Geomechanics … , 2008 2008 Citations: 223
Hypoplasticity for soils with low friction angles I Herle, D Kolymbas Computers and Geotechnics 31 (5), 365-373 , 2004 2004 Citations: 158
Hypoplastic constitutive equation with internal variables D Kolymbas, I Herle, PA Von Wolffersdorff International journal for numerical and analytical methods in geomechanics … , 1995 1995 Citations: 131
On the metrology of interparticle contacts in sand from x-ray tomography images M Wiebicke, E Andò, I Herle, G Viggiani Measurement Science and Technology 28 (12), 124007 , 2017 2017 Citations: 127
Measuring the evolution of contact fabric in shear bands with X-ray tomography M Wiebicke, E Andò, G Viggiani, I Herle Acta Geotechnica 15 (1), 79-93 , 2020 2020 Citations: 104
State boundary surface of a hypoplastic model for clays D Mašín, I Herle Computers and Geotechnics 32 (6), 400-410 , 2005 2005 Citations: 104
FE‐studies on the influence of initial void ratio, pressure level and mean grain diameter on shear localization J Tejchman, I Herle, J Wehr International Journal for Numerical and Analytical Methods in Geomechanics … , 1999 1999 Citations: 103
Numerical simulation of a tunnel surrounded by sand under earthquake using a hypoplastic model J Hleibieh, D Wegener, I Herle Acta Geotechnica 9 (4), 631-640 , 2014 2014 Citations: 76
A consolidation model for lumpy composite soils in open-pit mining XS Shi, I Herle, D Muir Wood Géotechnique 68 (3), 189-204 , 2018 2018 Citations: 64
Prediction of permanent soil deformations due to cyclic shearing with a hypoplastic constitutive model D Wegener, I Herle geotechnik 37 (2), 113-122 , 2014 2014 Citations: 59
A" class A" prediction of the bearing capacity of plane strain footings on sand J Tejchman, I Herle Soils and Foundations 39 (5), 47-60 , 1999 1999 Citations: 59
Effect of grain size and pressure level on bearing capacity of footings on sand I Herle Deformation and progressive failure in geomechanics, 781-786 , 1997 1997 Citations: 55
Improvement of a hypoplastic model to predict clay behaviour under undrained conditions D Mašín, I Herle Acta Geotechnica 2 (4), 261-268 , 2007 2007 Citations: 54
Numerical analyses of a tunnel in London clay using different constitutive models D Mašın, I Herle Proceedings of the 5th international symposium TC28 geotechnical aspects of … , 2005 2005 Citations: 53
Numerical simulation of lumpy soils using a hypoplastic model XS Shi, I Herle Acta Geotechnica 12 (2), 349-363 , 2017 2017 Citations: 50
Stationary states in hypoplasticity E Bauer, I Herle Constitutive modelling of granular materials, 167-192 , 2000 2000 Citations: 48
Comparison of vibrocompaction methods by numerical simulations M Arnold, I Herle International Journal for Numerical and Analytical Methods in Geomechanics … , 2009 2009 Citations: 46