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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.

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.

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