Stress hydro-mechanics

In this paper, the focus is on the development of a poromechanics model which addresses the chemical effects within the framework of the anisotropic porothermoelastic model [2], The resulting model, termed as porochemo-thermoelastic, accounts for fully coupled chemo-thermo-hydro-mechanical response of a chemically active formation saturated with a pore fluid comprising of two species under non-isothermal conditions. The numerical example presented demonstrates the thermo-chemical effect on the stress and pore pres-... 

Based on the characterization of the bentonite and on the details of the process of test installation, a thermo-hydro-mechanical model for the bentonite barrier and the heaters was to be prepared. Using this model, the thermo-hydro-mechanical response of the bentonite barrier as a result of the heat released by the heaters and the hydration from the host rock was required. Local field variables such as temperature, relative humidity, pore water pressure, stresses and displacements, as well as global... 

Abstract The Canadian Nuclear Safety Commission (CNSC) used the finite element code FRACON to perform blind predictions of the FEBEX heater experiment. The FRACON code numerically solves the extended equations of Biot s poro-elasticity. The rock was assumed to be linearly elastic, however, the poro-elastic coefficients of variably saturated bentonite were expressed as functions of net stress and void ratio using the state surface equation obtained from suction-controlled oedometer tests. In this paper, we will summarize our approach and predictive results for the Thermo-Hydro-Mechanical response of the bentonite. It is shown that the model correctly predicts drying of the bentonite near the heaters and re-saturation near the rock interface. The evolution of temperature and the heater thermal output were reasonably well predicted by the model. The trends in the total stresses developed in the bentonite were also correctly predicted, however the absolute values were underestimated probably due to the neglect of pore pressure build-up in the rock mass. 

Model performance is demonstrated for a simplified three-dimensional test case that takes into consideration both the thermo-hydro-mechanical interaction and a stress dependent permeability. The functionality of the described control concept for the coupled processes is illustrated by some selected simulations of Benchmark Test IB (BMTIB) of DECOVALEX III. 

Abstract A methodology for quantifying the contributions of hydro-mechanical processes to fractured rock hydraulic property distributions has been developed and tested. Simulations have been carried out on discrete fracture networks to study the sensitivity of hydraulic properties to mechanical properties, stress changes with depth, mechanical boundary conditions, initial mechanical apertures and fracture network geometry. The results indicate that the most important (and uncertain) parameters for modelling HM processes in fractured rock are fracture density and rock/fracture mechanical properties. Aperture variation with depth below ground surface is found to be of second order importance. 

JCS) values were used to represent the range of mechanical properties observed in all three formations (Formation 1 see Blum et al. 2(X)3 Formation 2 JRC (/- ) = 4.28, 5.98, 4.18, 2.29 JCS (1-4) = 39.3. 31.9, 90.9, 43.1 in MPa and the unchanged uniaxial compressive strength for all 4 cases UCS = 120.0 MPa Fault Zone JRC = 4.22, JCS = 105.9 MPa and the UCS = 128.4 MPa). In case of Formation 2 only four pairs were available, thus the entire data set is provided here. Stress conditions corresponding to five depths were also applied to the DFN. Table 1 summarizes the hydro-mechanical modelling results in terms of the median hydraulic apertures. Values range between 0.3 pm and 180.7 pm. 

Stress conditions for this study are selected in two ways, based on the above conceptual mechanisms of hydro-mechanical coupling in fractured rock. 

To get better the understanding of the system, the mechanical behaviour of the clay has been taken into account. The initial conditions are null total stresses everywhere. So, in-situ mechanical stresses are not taken into account. The results of our THM calculation show only stresses induced by thermal-hydro-mechanical couplings. The contact between the EB and the canister is once again supposed to be perfect, so that no radial displacement of the clay is allowed at that boundary. Biot s poroelastic model is chosen to represent clay behaviour. It takes partial saturation into account via an equivalent pressure which includes capillary effects, involving both gas and liquid, Dangla (1998). Biot s model is added as fourth equation to the system. The associated main variable is total stress state. The couplings with thermal-hydraulics behaviour are introduced by... 

In the production phase, the oil pressure decrease at well to reach a depletion of 10 MPa after 5 years. Due to hydro-mechanical couplings, this pressure decrease leads to a compaction of the reservoir (increase of the effective stress). Figure 5 shows that compaction is low after 1 year (40 cm). However, up to 5 years, irreversible deformations appear and compaction reaches a value of 13 meters at the production well after 20 years. 

Recognizing the importance of the coupled hydro-mechanical effects on the performance of civil engineering structures involving fractured rocks, the stress-flow coupling mechanism of the dam-foundation system at Longyangxia site was simulated using a three-dimensional Finite Element code, supported by two visco-elastic constitutive models to represent the time-dependent material behaviour of the dam concrete and the foundation rock. The calculated results were concord with the measured ones and helped to interpret the causes of this continuous displacement at the 13" dam section of the Longyangxia hydropower project, towards the left bank. 

By calculation on the basis of damage coupled hydro-mechanical model, it is clear that the stress of slope increases slightly. The mode of the fractures propagation and coalescence is mainly in tension, but sometimes is also shearing or tension-shearing. 

Hydro-mechanical properties of soil during the variation of saturation can be controlled by Soil Water Characteristic Curve (SWCC) (van Genuchten 1980), Hydraulic Conductivity Function (HCF) (Mualem 1976) and Suction Stress Characteristic Curve (SSCC) (Lu Likos 2006). These constitutive relationships can describe the relationship of saturation, matric suction, coefficient of permeability and suction stress of various saturation soil. In addition, recent researches indicate that hydromechanical properties of soil have hysteresis effect related to the difference of drying and wetting history (Kool Parker 1987, Mualem 1984, Likos Lu 2004). 

For the significant influence of saturation and hysteresis on the hydraulic conductivity and stress condition of soil, hydro-mechanical properties in both drying and wetting paths are very important factors that should be considered in the valuation of strength of sliding zone soil and the stability... 

After the generation of the DFN model, various boundary stress and flow conditions are applied to the model for hydro-mechanical coupling analysis. Figure 3 shows the boundary conditions adopted in the UDEC models. 

The hydro-mechanical numerical experiments of fractured rock mass are conducted by increasing the stress ratios K = horizontal stress/vertical stress) while keeping vertical stress constant in this paper. And then some conclusions are reached ... 

I want to emphasize, above all, that these theories of matter as stresses, strains, singularities, or vortices of ether, were mechanical (and even hydro-dynamic) theories. When scientists such as Crookes and Lodge, and Theoso-phists such as Besant and Leadbeater, melded physics with spiritual and psychic forces via theories of the ether (and the additional particles that Theosophy added to the equation), they were lending scientific credibility to spiritual ideas. Paradoxically, in their critique of scientific materialism, they asserted a mechanical theory of spirituality. Theosophy thus required a form of vitalism to counterbalance the mechanistic tendencies of its physics. 

Many researches have been conducted to clarify the mechanism of the volume change of polyelectrolyte gels. The H NMR imaging experiments have been made and provided spatial information on the change in the distribution and motion of water in the PMAA gel induced by stress [24] and electric fields [25-27]. The solvent, water, plays an important role in the deformation of the hydro-swollen PMAA gel and Yasunaga and Ando [28-... 

The mechanical state of a drying body is described by the coupled system of differential equations composed of the equilibrium of internal forces and constitutive equations relating stresses with themechano-thermal-hydro strains. The internal equilibrium of forces is expressed by stresses as follows ... 

---