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This paper proposes a new interface constitutive model for fully grouted rock-bolts and cable-bolts based on pull-out test results. A database was created combining published experimental data with in-house tests. By means of a comprehensive framework, a Coulomb-type failure criterion accounting for friction mobilization was defined. During the elastic phase, in which the interface joint is not yet created, the proposed model provides zero radial displacement, and once the interface joint is created, interface dilatancy is modeled using a non-associated plastic potential inspired from the behavior of rock joints. The results predicted by the proposed model are in good agreement with experimental results. The model has been implemented in a finite element method (FEM) code and numerical simulations have been performed at the elementary and the structural scales. The results obtained provide confidence in the ability of the new model to assist in the design and optimization of bolting patterns.

This paper presents an enhanced constitutive model integrating deviatoric hardening with a modified yield surface for overconsolidated clayey soils in a general framework of Cam-clay type models. Its performance was assessed with the simulation of drained and undrained triaxial tests on three clays at different consolidation states in comparison to two critical state models. The proposed model satisfactorily estimates the shear resistance, while capturing the smooth nonlinearity of the soil response. Shear triaxial tests at constant mean pressure were performed on an overconsolidated marl to study the shear response. Their simulation attests the importance of deviatoric hardening integration.

International audience; Increasing tunnel excavations in dense urban areas faces the issue of accurately predicting tunnelling-induced surface settlement. The quality of those predictions closely depends on the choice of soil constitutive model. In this context, some widely used soil models in engineering practice not only fail to reproduce some characteristics of soil behaviour on the constitutive level but also lead to shallower settlement. This article studies the influence of the choice of the soil model on tunnelling-induced displacements through a case study. Three different soil models are used to simulate soil behaviour, namely the hardening soil model, the modified cam clay model and a proposed enhanced critical state model incorporating deviatoric and volumetric hardening. The proposed model is first validated on different triaxial tests and its features are especially highlighted for overconsolidated soils. This model is then compared to the other two models on tunnelling simulations. The results show great predicted settlement sensitivity to the choice of soil model. The proposed model engenders deeper settlement and, consequently, enables a more conservative design. Furthermore, parametric studies demonstrate significant disparities in the predicted displacements by the different soil models depending on the initial conditions and the stress relaxation ratio.

The modeling of Artificial Ground Freezing in geotechnical engineering applications has two main objectives, the first is the prediction of the extent of the frozen zone around the cooling sources (Thermo-Hydraulic models) and the second is the prediction of the ground’s deformations and the site stability (Thermo-Hydro-Mechanical models). Reliable predictions require the consideration of unfavorable hydro-geological conditions such as high seepage velocities, ground heterogeneity and saline groundwater that may negatively influence the performance of AGF. The influence of the saturating fluid salinity on the THM behavior of the ground during freezing is the less documented point among the three and is therefore the subject of this paper. To this end, a fully coupled THM model considering the salinity effect has been derived. The formalism is completely thermodynamically consistent and introduces some simplifying assumptions, especially to describe phase change terms (capillary pressure and latent heat), in order to achieve a mathematical formulation that can be easily handled by computation software. Stress-free freezing laboratory tests carried out on specimens initially fully saturated with sodium chloride solutions at three different concentrations allowed to validate the proposed approach and to highlight some key mechanisms associated with the phase change of saline-saturated porous media.

Artificial ground freezing has been used in the mine of Cigar Lake to mitigate groundwater infiltration to underground mining operations and stabilize the heterogeneous and poor ground. In addition to the control of the freezing process, the ability to predict accurately the ground movements and the site stability is crucial to a successful use of this technique. This requires developing adequate constitutive models able to correctly reproduce the mechanical behavior of water-saturated soils at low temperatures. To achieve this goal, a digital control servo-hydraulic triaxial test facility with full data acquisition has been developed, and an experimental program was carried out to investigate the mechanical behavior of metapelite samples collected from the mine of Cigar Lake. A series of triaxial compression tests were conducted on reconstituted and natural frozen metapelite specimens under different strain rates (2.5, 4.5 and 8 × 10−6 s−1) and at different temperatures (−10, −20 and −30 °C) and confining pressures (1, 5 and 9 MPa). The experimental results showed that the stress-strain behavior of frozen metapelite, in the studied range of temperature and confining pressure, is elasto-viscoplastic, strain hardening, highly sensitive to temperature and moderately sensitive to the confinement level. They also proved that the transition contractancy-dilatancy is significantly dependent on temperature and suggested the existence of a critical temperature between −20 and −10 °C that represents a dilatancy threshold. To capture these observations, a recent phenomenological model developed for crystalline rocks was used. The model accounts for the phenomena of hardening, dilatancy/contractancy and time dependency and was extended to include the effect of temperature on the frozen material's distorsion and on the dilatancy onset. The proposed model was validated using the triaxial compression tests on metapelite and experimental results from literature on frozen sand.

The scope of this paper is to investigate rate effects on rock cutting process at bottomhole pressure . The solution of the cutting problem is derived in the framework of the theory of poroelastoplasticity. The problem is firstly solved analytically using some assumptions derived from the literature review. Then, a numerical resolution of the fully coupled problem is performed based on the finite element method . These two different approaches show that pore pressure in shear-dilatant rocks decreases as a function of the cutting velocity depending on rock permeability and interstitial fluid properties. Pore pressure change has a hardening effect leading to an increase of the rock drilling resistance.

In geotechnical engineering applications, the modeling of artificial ground freezing is primarily aimed at predicting the extent of frozen zone around the cooling sources. This modeling could be more or less complex not only according to the material’s texture and the hydro-geological context but also to the salt concentration of the saturating fluid. Through a thermodynamically consistent framework, a fully coupled heat and mass transfer formulation considering the salinity effect was derived. This formulation was intended to capture the most relevant phenomena of ground freezing encountered in geotechnical applications. Particular attention was given to the phase change problem where appropriate simplifying assumptions were made in order to make the proposed methodology easier to apply in field applications. The proposed approach was validated by means of freezing-thawing laboratory tests, carried out on specimens initially fully saturated with sodium chloride solutions at various concentrations. Good agreement was obtained between the measured and predicted results.

International audience; Lightly loaded structures constructed on expansive soils may develop structural damage as a result of changes in the soil’s moisture content. This study investigated an analytical model of soil–structure interaction to assess the settlement of dwellings built on swelling soils when droughts occur. The building behavior was investigated with the Euler–Bernoulli beam theory, and the ground behavior was investigated with a Winkler-derived model based on the state surface approach. The analytical model results were compared to those of a finite element analysis using the Barcelona Expansive Model (BExM) performed with Code_Bright. The analytical model was then used to assess the settlement transmission ratio for a typology of clayey soils and different parameters of building. The results indicated that the final deflection of the building increased with the building length and soil suction. The building deflection due to the suction variations was inversely proportional to the load, the rigidity of the building and the embedding depth of the foundation. Increasing these parameters made the building less vulnerable to shrinkage and swelling action.

In unsaturated swelling-shrinking soils, like clay soils, water content change results in significant volume change and drying is associated with high water content gradients.This work presents initially the soil water retention curve (SWRC) of a bentonite-silt mixture compacted at three different initial dry densities (1.27, 1.35 and 1.55 Mg.m− 3). The SWRCs were fitted by the van Genuchten (1980) and Brooks and Corey (1964) type functions. The estimated parameters were used to model the SWRC of the intermediate samples.

International audience; This paper presents a simple approach to model the hydro-mechanical behaviour of swelling soils at different initial states during successive wetting and drying cycles. This model was developed based on the experimental results obtained for an expansive bentonite/silt mixture compacted at three different initial dry densities representing loose, intermediate and dense states. The parameters of the simplified model were initially fitted based on the results obtained for the loose and dense samples and then used to estimate the hydraulic and mechanical behaviour of the intermediate samples. Generally, the model prediction produced a satisfactory correspondence with the experimental results.

Tunnels construction is increasingly favored as a sustainable transportation and infrastructure development system. 200km are going to be excavated only in France in the next ten years in dense urban areas.During tunnel excavation, ground movements must be controlled and well predicted to avoid any damage on existing buildings. The tunnel face moves typically instantly toward the excavation. The tunnel wall convergence is added to theface extrusion. These movements may spread to the surface of shallow tunnels leading to significant disturbances or accidental damage (differential settlement, cave-in occurrence, buildings collapse, etc.).Different parameters influence the quality of tunnels simulation and induced displacements prediction. The quality of those predictions closely depends on the choice of soil constitutive model. In this context, some widely used soil models in engineering practice not only fail to reproduce some characteristics of soil behavior on the constitutive level but also lead to shallower settlement.This PhD thesis proposes an enhanced critical state model incorporating deviatoric and volumetric hardening mechanisms adapted for tunneling simulations. This model satisfactorily reproduces the nonlinear soil response to laboratory tests and enables a more conservative tunneling design.The impact of other modeling choices is studied through 2D and 3D tunneling simulations in different configurations with the proposed soil model. Furthermore, comparison with measurements obtained from a tunnel section of the Grand Paris Project highlight the performance of the proposed model in simulating tunneling induced displacement.; Le développement de l’urbanisme privilégie de plus en plus souvent la solution souterraine. Le creusement d’environ 200km de tunnels est prévu dans les dix prochaines années en France seulement, en milieu urbain dense.L’excavation d’une cavité dans un terrain engendre des mouvements dans le massif. Le front de taille se déplace généralement instantanément vers l’excavation. A ce déplacement d’extrusion s’ajoute la convergence des parois du tunnel. A faible profondeur, ces mouvements risquent de se propager jusqu'à la surface du terrain constituant une cuvette de tassement qui peut conduire à des désordres importants voire de nature accidentelle (tassements différentiels, développement de fontis, effondrement de constructions, etc.). Plusieurs paramètres influencent la qualité des simulations et la prévision des déplacements induits par le creusement d’un tunnel. Le choix d’une loi de comportement est primordiale pour la modélisation des tunnels qui dépend de la réponse du sol en termes de déformations. La prédiction des déplacements engendrés requière un modèle de comportement du sol rigoureux qui puisse simuler le plus fidèlement possible la réponse du sol.Cette thèse propose un modèle de comportement adapté à la simulation du creusement de tunnel avec un mécanisme d’écrouissage déviatorique dans le cadre de la théorie de l’état critique. Ce modèle reproduit de manière satisfaisante la réponse non linéaire du sol à l’échelle des essais de laboratoire et présente une alternative sécuritaire pour les simulations à l’échelle de la structure.L’effet de l’influence de plusieurs paramètres sur la simulation des tunnels est étudié à travers des simulations 2D et 3D avec différentes configurations et en considérant le couplage hydromécanique. Le modèle proposé est aussi utilisé pour la reproduction de mesures in-situ d’une section de tunnel du Grand Paris.

Tunnels construction is increasingly favored as a sustainable transportation and infrastructure development system. 200km are going to be excavated only in France in the next ten years in dense urban areas.During tunnel excavation, ground movements must be controlled and well predicted to avoid any damage on existing buildings. The tunnel face moves typically instantly toward the excavation. The tunnel wall convergence is added to theface extrusion. These movements may spread to the surface of shallow tunnels leading to significant disturbances or accidental damage (differential settlement, cave-in occurrence, buildings collapse, etc.).Different parameters influence the quality of tunnels simulation and induced displacements prediction. The quality of those predictions closely depends on the choice of soil constitutive model. In this context, some widely used soil models in engineering practice not only fail to reproduce some characteristics of soil behavior on the constitutive level but also lead to shallower settlement.This PhD thesis proposes an enhanced critical state model incorporating deviatoric and volumetric hardening mechanisms adapted for tunneling simulations. This model satisfactorily reproduces the nonlinear soil response to laboratory tests and enables a more conservative tunneling design.The impact of other modeling choices is studied through 2D and 3D tunneling simulations in different configurations with the proposed soil model. Furthermore, comparison with measurements obtained from a tunnel section of the Grand Paris Project highlight the performance of the proposed model in simulating tunneling induced displacement.; Le développement de l’urbanisme privilégie de plus en plus souvent la solution souterraine. Le creusement d’environ 200km de tunnels est prévu dans les dix prochaines années en France seulement, en milieu urbain dense.L’excavation d’une cavité dans un terrain engendre des mouvements dans le massif. Le front de taille se déplace généralement instantanément vers l’excavation. A ce déplacement d’extrusion s’ajoute la convergence des parois du tunnel. A faible profondeur, ces mouvements risquent de se propager jusqu'à la surface du terrain constituant une cuvette de tassement qui peut conduire à des désordres importants voire de nature accidentelle (tassements différentiels, développement de fontis, effondrement de constructions, etc.). Plusieurs paramètres influencent la qualité des simulations et la prévision des déplacements induits par le creusement d’un tunnel. Le choix d’une loi de comportement est primordiale pour la modélisation des tunnels qui dépend de la réponse du sol en termes de déformations. La prédiction des déplacements engendrés requière un modèle de comportement du sol rigoureux qui puisse simuler le plus fidèlement possible la réponse du sol.Cette thèse propose un modèle de comportement adapté à la simulation du creusement de tunnel avec un mécanisme d’écrouissage déviatorique dans le cadre de la théorie de l’état critique. Ce modèle reproduit de manière satisfaisante la réponse non linéaire du sol à l’échelle des essais de laboratoire et présente une alternative sécuritaire pour les simulations à l’échelle de la structure.L’effet de l’influence de plusieurs paramètres sur la simulation des tunnels est étudié à travers des simulations 2D et 3D avec différentes configurations et en considérant le couplage hydromécanique. Le modèle proposé est aussi utilisé pour la reproduction de mesures in-situ d’une section de tunnel du Grand Paris.