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From the combination of existing modelling approaches, a constitutive framework is presented for the numerical modelling of soft structured clays. The formulation accounts, in a natural way, for time-dependent phenomena such as stress relaxation, loading rate dependency, ageing, and creep deformations under constant load. It also incorporates the effect of soil structure and its degradation under mechanical loading. To demonstrate the potential of the proposed approach, a constitutive model is presented, based on this framework, and it is applied to the simulation of a number of laboratory tests from the literature.

Penetration depth of Spudcan foundations for offshore mobile Jack-up rigs is typically predicted by considering a wished-in-place foundation at different depths and following traditional bearing capacity approaches. However, the large penetration depths involved, stress redistributions and the flow of the material around the spudcan are some example of features which make the wished-in-place assumption quite unrealistic. This paper presents an open access application package developed to simulate and hence predict load penetration curves of spudcan installation in multi-layered clay profiles. The numerical tool adopts the recently developed particle finite element method for geotechnical applications (G-PFEM). The potential of this large strain particle finite element application is demonstrated by simulating field data from the literature. The results show that load-penetration curves obtained using G-PFEM capture more efficiently the field results with respect to other numerical and analytical methods. It is also shown how the G-PFEM automatically captures cavity infill. In the paper the computational cost for the simulation of penetration up to 40m on a standard desktop are shown to be low compared to other commercial software. This work has been supported by the Ministry of Science and Innovation of Spain through research grant BIA2017-84752-R. The authors acknowledge financial support from the Spanish Ministry of Economy and Competitiveness, through the ‘Severo Ochoa Program for Centers of Excellence in R&D’ (CEX2018-000797-S).

A partir de la combinación de teorías existentes, se presenta un marco teórico para la modelación numérica de arcillas blandas estructuradas. La formulación toma en cuenta, de forma natural, fenómenos dependientes del tiempo como la relajación de esfuerzos, dependencia con la velocidad de carga, envejecimiento y deformaciones de creep bajo carga constante. También incorpora el efecto de la estructura del suelo y su degradación ante carga mecánica. Para demostrar el potencial del enfoque propuesto, se presenta un modelo constitutivo, basado en este marco teórico, y se utiliza en la simulación de algunas pruebas de laboratorio de la literatura.

Coupled thermo-hydro-mechanical (THM) analyses have been used to examine the interacting phenomena associated with the simultaneous heating and hydration of an engineered bentonite barrier placed in a drift excavated in granite. The specific problem studied is an in situ test being carried out in the underground laboratory at Grimsel (Switzerland). After describing the test and the theoretical formulation, the results of a coupled THM analysis using the best parameter estimation currently available are presented and discussed. The ffect of various features of analysis are explored by means of additional analyses in which each of those features are varied, one at the time. Finally, sensitivity analyses have been carried out to examine some critical aspects of the in situ test design. Performance of coupled THM analyses has led to a better understanding of the various inter-related phenomena occurring during heating and hydration of the engineered clay barrier.

A full scale field test to evaluate the effects of ventilation in a tunnel excavated in Opalinus clay has been performed in the underground laboratory of Mont Terri in Switzerland. The test involved several stages of wetting and drying under controlled conditions. To aid interpretation, coupled hydromechanical analyses have been performed taking into account the specific features of the test, especially the conditions in the boundary between air and clay. An elastoplastic model has been used to describe the mechanical behaviour of the rock. The results have revealed the existence of two different zones around the tunnel: a desaturation zone reaching only about 50 cm inside the clay and a larger zone, extending 2.5-3m from the tunnel wall, in which the Opalinus clay is under suction. Observed ventilation effects on Opalinus clay have been modest and reduced to zones quite close to the tunnel.

The paper examines the interaction between host rock and a clay-based engineered barrier in the context of deep underground disposal of high-level radioactive waste. A large scale ‘‘in situ’’ heating test currently under way in the underground Grimsel Rock Laboratory (GRL; Switzerland) is adopted as a representative case for study. The main features of the behaviour of the rock/barrier system have been examined using a comprehensive programme of coupled thermo–hydro– mechanical analyses. A parametric study has been performed to assess the effects of individual phenomena and parameters. The characterisation activities carried out in relation with the in situ test provide the information on material properties and test conditions required. Results highlighting the influence of vapour diffusion, permeability, and retention curve of rock and bentonite are presented. The interaction between clay barrier and host medium exhibits a high degree of complexity.

An appropriate understanding of the interaction and effects of thermal, hydraulic, mechanical and chemical (THMC) phenomena occurring in compacted swelling clay is greatly assisted by the development and use of coupled theoretical formulations. In this contribution one example of such a formulation is presented. Special attention is given to phenomena likely to be encountered in clay barriers and seals used as part of containment systems of nuclear waste. The types of processes considered in the chemical formulation include hydrolysis, complex formation, oxidation/reduction reactions, acid/base reactions, precipitation/dissolution of minerals and cation exchange. Both kinetically controlled and equilibrium-controlled reactions have been incorporated. The coupling between geochemical variables and mechanical behaviour is ensured by a chemomechanical constitutive law that is described in this paper. The formulation has been implemented in a numerical code. An application is presented concerning the performance of a small scale test simulating high-level nuclear waste repository conditions. Also numerical simulations of triaxial and oedometer tests are presentedwhere the samples were subjected to a sequence of mechanical and chemical actions.

The subject of this contribution is the hydromechanical behaviour of stiff clays and mudstones, i.e. geological materials in which fine grained particles predominate. It is especially focussed on argillaceous materials that are intermediate between soils and rocks not only with respect to strength but also in terms of porosity and compressibility. Because of space limitations, only sorne salient aspects of the behaviour are outlined herein. First, sorne general aspects of the mechanical behaviour are high1ighted, afterwards the issues of brittleness and progressive failure are addressed and finally sorne observations of their hydromechanical response in underground excavations are presented.

The paper examines some aspects of the hydromechanical behaviour of argillaceous hard soils and weak rocks. After considering the wide variety of this class of materials, some common behaviour features are sought concerning compressibility, structure development, uplift and swelling, microfabric, anisotropy, effects of discontinuities and hydraulic properties. Those features are examined in the context of appropriate behaviour frameworks developed for this type of materials. Two themes are then selected for special consideration: brittleness and progressive failure and the response of argillaceous weak rocks to deep underground excavations. For the second topic, particular attention is given to field results obtained in deep underground laboratories for nuclear waste disposal. The paper concludes with a summary of the main points.