David Mašín

Charles University in Prague | CUNI

This article presents the results of an experimental programme devoted to inspecting the validity of Miner’s rule under one-dimensional conditions on Zbraslav sand and Malaysian kaolin. For this purpose, a series of stress-controlled oedometer tests were performed, considering packages of cycles with varying axial stress amplitudes in different seq...

Numerous geotechnical applications are significantly influenced by changes of moisture conditions, such as energy geostructures, nuclear waste disposal storage, embankments, landslides, and pavements. Additionally, the escalating impacts of climate change have started to amplify the influence of severe seasonal variations on the performance of foun...

This article experimentally evaluates the influence of shearing rate on the monotonic and cyclic response of isotropically-consolidated samples of Malaysian kaolin. On the one hand, a series of undrained monotonic triaxial tests were performed with varying shearing displacement rate. On the other hand, undrained cyclic triaxial tests were conducted...

This article proposes an extended constitutive model for liquefaction analysis of sands. The proposed model is formulated based on the hypoplastic model for granular soils by von Wolffersdorf (1996), enhanced with Intergranular Strain Anisotropy by Fuentes et al. (2019), which is usually referred to as ISA-hypoplasticity. The proposed extended mode...

This article presents a critical discussion of the repercussion of overshooting effects on element test and finite element simulations. For exemplification purposes, three advanced constitutive models for sands which already achieved a certain level of accuracy in the simulation of monotonic and cyclic loading were carefully selected, namely: a bou...

The Resilient Modulus (Mr) is perhaps the most relevant and widely used parameter to characterise the soil behaviour under repetitive loading for pavement applications. Accordingly, it is a crucial parameter controlling the mechanistic-empirical pavement design. Nonetheless, determining the Mr by laboratory tests is not always possible due to the h...

Modelling of slow-moving landslides and creeping slopes and predicting their rate of movement can provide important information to reduce risk and related costs. However, numerical modelling of landslide movements that accounts for soil mechanical behaviour is scarce in literature, especially when rate-dependent mechanical behaviour such as creep i...

Soil deposits may be subjected to preloading episodes due to different factors such as previous earthquakes, excavations, refilling, compaction, construction of overlying structures, storms under onshore/offshore conditions, among many others. It is well-known that preloading episodes remarkably influence the subsequent soil mechanical behavior and...

This paper presents a study of the accuracy of two-dimensional (2D) finite-element predictions of a displacement field of retaining structures supporting the excavation next to the Komořany tunnel in Prague, Czech Republic. The ground material is a Komořany sand, which is a sand with some gravel and almost no fines. Two different constitutive model...

This article presents a comprehensive experimental investigation on Zbraslav sand under monotonic and cyclic loading. Initially, the material response at large strains was investigated by means of undrained monotonic triaxial tests with different initial mean effective stresses and relative densities. A set of oedometric compression tests with mult...

The prediction of soil cyclic behaviour is relevant for several geotechnical applications. In order to obtain accurate predictions of settlements and pore water pressure build-up on boundary value simulations, robust constitutive models which are able to realistically reproduce the soil mechanical behaviour under monotonic and cyclic loading are ne...

This article experimentally evaluates the influence of directional drained cyclic preloadings on the subsequent undrained monotonic and cyclic response of Zbraslav sand. The cyclic tests were performed on dense samples and under triaxial conditions. The experiments considered several different preloading directions, magnitude of the maximum deviato...

Despite a considerable progress in the analysis and design of monopiles, many methods are based on complex mathematical structures with doubtful or hard assumptions to verify. Therefore, there is still a need for simple and yet accurate methods for the analysis of monopiles under drained and undrained lateral cyclic loading conditions. In this work...

The results of an experimental investigation on Malaysian kaolin under monotonic and cyclic loading are presented. In the tests, a wide range of initial conditions was varied in order to investigate their influence on the mechanical behavior of the kaolin. The response under monotonic loading was analyzed by means of undrained monotonic triaxial te...

Numerous studies in the literature are concerned with proposing new constitutive models for sands to simulate cyclic loading. Despite considerable progress in this area, there are various limitations on their simulation capabilities that are either overlooked or not communicated clearly by the developers. A number of these limitations are rather cr...

Around 80% of offshore wind turbines are founded using large-diameter monopiles, with a length reaching up to 60 m due to the lack of easily accessible shallow waters. Thus, there is a natural tendency to seek more economically viable solutions where tripod bucket foundation seems to be especially promising. However, the up-to-date knowledge on the...

Bentonite materials are considered as the main sealing component in the closure of repositories for radioactive waste. This is particularly due to their swelling capacity upon hydration, which helps to close remaining gaps and voids at the sealing location and thus ensure the confinement of the disposed radioactive waste. In repository conditions,...

This paper presents a study on Chlef sand to examine the effect of fines content (Fc), relative density (RD) and initial conditions on the compressibility behavior. The interpretation of the results is based on the concept of the intergranular voids ratio (es) and two hypoplastic parameters model Hs and n for calculation of the maximum voids ratio....

A wide range of geotechnical structures founded in fine-grained soils are subjected to complex cyclic loading scenarios. The prediction of their behavior has motivated the development of several constitutive models for soils under different mathematical frameworks. Some success has been achieved under certain simplified cyclic conditions. However,...

An advanced hypoplastic constitutive model for soft clay has been developed with the following features: pre-yield non-linearity, strength anisotropy (different critical state friction angles in compression and in extension), stress- and OCR-dependency of undrained shear strength and soil structure and its degradation during loading. The model feat...

This paper introduces an automated deterministic method for the calibration of the Modified Cam-Clay and hypoplastic clay model. The calibration is structured in a hierarchical order established based on the apriori sensitivity study performed. The proposed method favours the clear physical meaning of the model parameters to a complete optimization...

This paper discusses an automated deterministic approach to parameters calibration of the hypoplastic model for sand. The calibration is performed on results from basic laboratory experiments such as the oedometric test, isotropic compression test, and the drained and undrained triaxial shear tests. The calibration method is structured in a hierarc...

The Soil Mechanics group led by David Mašín at Charles University, Prague, Czech Republic, is seeking three motivated PhD students with experience in modelling and/or experiments to work on the following projects: 1) Calibration of advanced #constitutive models (supervisor: Tomáš Kadlíček); 2) Evaluation of soil behaviour including creep and numeri...

Compacted bentonite is often utilized as a buffer material between the canister containing radioactive waste and the host rock in deep geological repositories. Extremely low permeability and a potential to swell and develop large swelling pressures upon hydration are desirable characteristics for such material. This study focused on the B75 bentoni...

A novel approach of using existing implementations of constitutive material models in any numerical code interfaced with MFront. In this work, we developed a novel approach, which consists of using existing constitutive models already available in different finite element codes in any numerical codes interacting with MFront. We used for that the ve...

Implementing a constitutive material model is a long tedious and error-prone process, in particular for soils where a wide variety of models must be taken into account. Moreover, the implementation must satisfy the interface of the targeted solver. MFront is a popular code generator based on C++ mostly dedicated to mechanical behaviours which provi...

Irrespectively of fast development of approaches for the analysis and design in geomechanics based on the methods for discontinuum (such as discrete element method), analysis of continua based on mesh or fast developing particle-based meshless methods still represents major means of numerical analysis in geomechanics. At the very core of such an an...

The experimental data dealing with the so-called small strain stiffness of soils are indispensable in developing and calibrating advanced numerical models. A literature review revealed a lack of such data for unsaturated soils. In this study, the laboratory measurements of very small and small strain stiffness are carried out in a double-walled tri...

Around 80% of offshore wind turbines (OWTs) are founded on deep seabeds using large-diameter monopiles that reach a length up to 60 m. In a race to seek cost-effectiveness, tripod foundations made with suction caissons represent a promising solution. The deformation mechanism induced by cyclic lateral loading on the tripod bucket embedded in sand r...

Bentonites are considered to be the most suitable materials for the multibarrier system of high-level radioactive waste repositories. Since BCV bentonite has been proved to be an ideal representative of Czech Ca-Mg bentonites in this respect, it has been included in the Czech Radioactive Waste Repository Authority (SÚRAO) buffer and backfill R&D pr...

The paper presents evaluation of the newly proposed hypoplastic model for soft clays by modelling of the well-documented geotechnical failure of a deep excavation of Nicoll Highway, Singapore, in 2004. The marine clays present at the site are typical normally consolidated soft clays, exhibiting large deformability and stiffness and strength anisotr...

The study of cyclic loading on saturated natural clay deposits is of great interest for the analysis of offshore and onshore structures. Recent experimental research in the field of offshore engineering has indicated that the mechanical behavior of monopiles is strongly influenced by the reconsolidation processes that take place during calm conditi...

Development and Improvement Of NUmerical methods and Tools for modelling coupled processes (DONUT) Workpackage in the European Joint Programme on Radioactive Waste Management (EURAD)

This paper presents a new viscohypoplastic model for soft clays accounting for their typical features-strength anisotropy and rate-dependency. The model is based on the hypoplastic model for clays enhanced by the anisotropic shape of the asymptotic state boundary surface. It has been shown that if the surface is skewed the model predicts different...

An evaluation of the slope stability in FEM software is often performed as a complementary analysis to the plastic deformation analysis. The slope stability represented by the factor of safety is, in the most of FEM software, evaluated by the reduction of the strength parameters \(c\) and \(\varphi \) of the Mohr-Coulomb model. Consequently, the la...

The paper presents a procedure for utilization of photographic image data via digital photogrammetry for use in geotechnics. The process of data manipulation in various programs in thoroughly described step-by-step. The motivation of the development is to prepare the final geometrical structure for finite element method software, where numerical mo...

The Intergranular Strain Anisotropy (ISA) model by Fuentes and Triantafyllidis (2015) corresponds to an extension for the conventional hypoplastic models to account for the effects observed under cyclic loading. Similar to the Intergranular Strain (IS) theory proposed by Niemunis and Herle (1997), this extension enhance the hypoplastic models in ma...

Argillaceous formations are currently being considered in several countries as a possible host medium for deep geological disposal of high- and intermediate-level and long-lived nuclear waste (Delage et al., 2010). They exhibit desirable features such as low hydraulic conductivity, low molecular diffusion, and significant radionuclide retention cap...

An evaluation of slope stability using the finite element method is often performed as a complementary analysis to the plastic deformation analysis. The slope stability is typically evaluated by the reduction of the strength parameters c and φ of the Mohr-Coulomb model and it is represented by the so-called factor of safety. It is much less common...

The analysis of geotechnical problems involving saturated soils under cyclic loading requires the use of advanced constitutive models. These models need to describe the main characteristics of the material under cyclic loading and undrained conditions, such as the rate of the pore water pressure accumulation and the stress attractors. When properly...

Large-diameter monopiles are the most commonly used foundation to support offshore wind turbines. Early designs usually adopted pile diameters (D) between 4 and 6 m, which is recently extended to 8 m and will target 10 m in the future. It is increasingly evident that the existing design method (i.e., API's p-y model) can significantly under-predict...

In the present work, a constitutive model for anisotropic clays is proposed and evaluated under monotonic and cyclic loading. To that end, the hypoplastic model for anisotropic clays by Mašín is extended to consider the effects observed on cyclic loading. The extension follows from the intergranular strain anisotropy (ISA) approach by Fuentes and T...

In this paper, we aim to clarify microstructure of bentonite from Cerny vrch deposit in the Czech Republic. We adopt results of ESEM and MIP experiments performed at various suctions along wetting and drying paths on bentonite samples compacted from powder to two different initial dry densities. The data were used for quantification of fractal dime...

Arcades, i.e. lenticular and other specifically shaped hollows controlled by discontinuities, have recently been recognized as a weathering form typical for sandstones, weathered quartzites, granites, or tuffs. They are produced by accelerated weathering and erosion in stress shadows related to the redistribution of gravity-induced stress along pla...

This paper describes how MFront can be used as a wrapper to integrate an existing implementation of a constitutive equation in a solver supported by MFront. More precisely, this document shows how to wrap the bentonite behaviour developed by D. Mašín (see [1, 2]) for its use in the thermo-hydro-mechanical model of the OpenGeoSys’ solver (OGS, see...

This paper presents a new viscohypoplastic model for soft clays accounting for their typical features—strength anisotropy and rate dependency. The model is based on the hypoplastic model for clays enhanced by the anisotropic shape of the asymptotic state boundary surface. It has been shown that if the surface is skewed, the model predicts different...

Thermo-hydro-mechanical coupling is relevant in various natural processes and engineering applications involving clay soils. It can affect slope deformations and stability, as well as the functioning of clay barriers and energy piles. Temperature changes can alter the water retention capacity of expansive clays and, in turn, produce pressure, stren...

The intergranular strain concept was originally developed to capture the small‐strain behaviour of the soil with hypoplastic models. A change of the deformation direction leads to an increase of the material stiffness. To obtain elastic behaviour for smallstrains, only the elastic part of the material stiffness matrix is used. Two different approac...

In the original version of the book, the following corrections have been incorporated: Equation 5.1 has been updated in Chapter 5. Equation 7.14 has been updated in Chapter 7.

In this chapter, the hypoplastic model developed by von Wolffersdorff [1] is introduced. This model is often considered as a reference hypoplastic model for predicting the behaviour of granular materials. To clarify the model structure, the model development was followed step by step in Chap. 4. In this chapter, its mathematical formulation is summ...

In Chap. 3 of this book, the basic principles of hypoplastic models were described. Obviously, for the models to be applicable in numerical modelling tools, models must be formulated in full tensorial notation. To explain the mathematical structure of hypoplastic models, their historical development is traced back in this chapter, starting with the...

In this chapter, the two features of soil (and particulate material in general) mechanical behaviour that distinguish it from most other materials are introduced: stiffness non-linearity and asymptotic behaviour. Supporting experimental evidence is outlined, along with various modelling concepts suggested by different researchers in the past. The a...

In this chapter, a rate independent hypoplastic model for clays, formulated by Mašín [1], is described. It is based on an explicit asymptotic state boundary surface approach, which has been introduced in Chap. 4. The model, in its basic form, requires specification of five parameters \(\varphi _c\), N, \(\lambda ^*\), \(\kappa ^*\) and \(\nu \). Th...

The two reference models for sand and clay, introduced in Chaps. 5 and 6, cover the behaviour of a variety of common soils under standard conditions. However, specific applications or specific soil types require enhancements of these models to achieve the predictive goal. A selection of such enhancements is described this chapter. The readers are i...

The aim of this chapter is to demonstrate the basic principles of hypoplasticity without the formalism of tensorial operations. Simple 1D scalar hypoplastic models for shear and for compression are introduced first. Subsequently, the model is defined in terms of vectors and, finally, simple tensorial models are introduced as hypoplastic equivalents...

This book explains the hypoplastic modelling framework. It is divided into two parts, the first of which is devoted to principles of hypoplasticity. First, the basic features of soil’s mechanical behaviour are introduced, namely non-linearity and asymptotic properties. These features are then incorporated into simple one-dimensional hypoplastic equ...

In this paper, the microstructure of the Czech bentonite B75 was investigated by three methods: water retention curve (WRC) measurements, mercury intrusion porosimetry (MIP) measurements and environmental scanning electron microscopy (ESEM) investigation. The experiments were performed on samples at various compaction levels (between 1·27 and 1·90...

Proper understanding of the deviatoric behaviour of peats represents a challenge in soil mechanics. Exceptional high compressibility together with extremely high friction angles distinguishes peats from classical organic soils. Considerable amount of triaxial test data on peats can be found in the literature, mostly coming from standard undrained t...

Compacted bentonites are popularly being considered as buffer or backfill material in high level nuclear waste repositories around the world. These bentonites may undergo various conditions including hydration from around geo-environmental water and heating by the radiation of the used fuel during its period of operation. Water retention properties...

Weathering patterns on sandstone cliff faces and sloping surfaces were studied from the viewpoint of gravity-induced stress combined with the presence of planar discontinuities in the rock. Critical evaluation of hundreds of photos taken in various regions around the world, numerical modelling using finite element method (including automatic stress...

https://soilmodels.com/presentations-on-hypoplasticity-applications-d-masin-ngi-2017/

The aim of this paper is to evaluate soil shear strength from the Dobkovicky landslide. The landslide was activated on June 6, 2013 after heavy rains and the D8 motorway, which was under construction at the time, was damaged. The laboratory tests were carried out on two types of soils, clay and tuff, both from the surface of the rupture. Critical a...

In this paper, water retention curves of compacted Czech bentonite B75 measured by vapour equilibrium methods are presented. The controlled suction range was 3.29 MPa-286.7 MPa. The changes in microstructure of compacted bentonite under free swelling was studied upon wetting and drying path. Mercury intrusion porosimetry (MIP) and environmental sca...

The installation of jack-up platforms involves a first stage where the spudcan foundations are penetrated into the seabed for several diameters in depth. When installed in fine-grained soils, this usually results in the accumulation of excess pore pressures. Once the installation is completed, the undrained spudcan capacity under combined vertical,...

Dynamical In Situ Study of Morphological Changes of Bentonite in ESEM - Volume 23 Issue S1 - Eva Navrátilová, Vilém Nedéla, Haiquan Sun, David Masin

The modelling of interfaces is important for the holistic simulation of geotechnical structures (e.g. piles, tunnels and geogrids). For this reason, advanced constitutive interface models and numerical techniques are needed. There are few user-friendly models, and these are rarely implemented. In this paper, a new approach for advanced interface mo...

Contact descriptions for interfaces between structural elements (e.g. piles, anchors and tunnel-linings) and soils are widely used in geotechnical engineering. Most of these constitutive interface models, developed for sands, consider 2D conditions. For clays, only a limited number of 3D interface models exist. In this paper, the fine-grained conti...

Previous studies on laterally loaded piles in clay have mainly focused on flexible and rigid piles. Little attention has been paid to semi-rigid piles (whose pile–soil stiffness lies somewhere between those of rigid and flexible piles), which may behave as either flexible piles or rigid piles, depending on the change in soil stiffness during cyclin...