Introduction
Code-Bright has been developed at the Department of Geotechnical engineering and Geosciences, University of the Polytechnic University of Catalonia (UPC). This code has been developed to carry out a simulation of Coupled Deformation Brine, Gas and Heat Transport. Code-Bright could be used to solve load-displacement, gas pressure, liquid pressure, and inclusion content problems. The code was first developed on the basis of a new general theory for saline media (Olivella et al. 1996). After that, the code was generalized for modeling coupled thermos-hydro-mechanical processes in geological media.
The code uses the finite element to discretize the space (geometry) and finite deference for time discretization for the partial differential equations. For non-linear iterative scheme, the Newton-Raphson method is used. The mass and energy balance equations are used for flow-type
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problems, while the stress equilibrium equations are used for equilibrium-type problems. The program is designed for a wide range of problems from simple uncoupled cases to more complicated cases.
One of the main advantages of Code-Bright is the wide range of material constitutive laws included. The constitutive laws in Code-Bright are categorized as hydraulic and thermal constitutive models and mechanical models. The hydraulic and thermal constitutive models include retention curve intrinsic permeability, liquid and gas phase relative permeability, diffusive fluxes of mass, diffusive fluxes of mass and energy constitutive flux of heat. The mechanical constitutive models include Elasticity, non-linear elasticity, visco-plasticity for saline and granular materials, visco-plasticity for unsaturated soils based on BBM, damage-elasto- plastic model for argillaceous rocks, a thermo-elasto-plastic model for soils, and CASM’s family models. One additional powerful option in the material constitutive models is the new material command. The new material command gives the ability to create a new material taking an existing material as a base material. The new material will have the same fields as the base material. Moreover, the properties of materials could be changed each interval. This gives the ability to define any material with time-dependent properties using Code-Bright. The thermos- hydro-mechanical (THM) ability coupled with material constitutive laws and interval dependent material properties make Code-Bright a very powerful tool for numerical simulation of
unsaturated collapsible and expansive soils as well as frost-heave problems.
Many researchers used Code-Bright to study and investigate the behavior of unsaturated soils and frost heave-problems. Rutqvist et al. (2005) used Code-Bright for coupled thermal- hydrological-mechanical-chemical analysis. In this research, a multiyear large-scale underground heating test was performed to investigate the coupled-thermal-hydrological-chemical behavior of
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unsaturated fractured and welded tuff in Yucca Mountains, Nevada, USA. Afterwards, the experimental results were compared against four different numerical models performed by different research teams. In this study, the capability of Code-Bright to perform such
complicated coupled problems was investigated and verified. Code-Bright was used successfully to investigate and study the behavior of expansive unsaturated soils based on the coupling
between micro and macro structures of the soil (Sánchez et al. 2005). In this study, Code-Bright was used to simulate three application cases. Of particular interest is the simulation of an accidental overheat took place in a large-scale heating test for 0.64 m thick engineered barrier made up of compacted bentonite.
Code-Bright has the capability to consider the dynamic Evapotranspiration (ET) boundary condition coupled with THM analysis. This capability was used by Rodríguez et al. (2007) to analysis and study the desiccation of a mining waste. In this test a set of experimental results to characterize the mining waste hydraulically and mechanically. Afterwards, a
theoretical formulation was developed based on the experimental results. Finally, Code-Bright was successfully used to simulate the some of the experimental tests considering the ET process to predict the time and location of crack initiation.
Hydro-Mechanical Slope Stability Analysis
Barcelona Basic Model (BBM) (Alonso et al., 1990) coupled with van Genuchten (1980) equation were used to study the hydro-mechanical behavior. Both models are already
implemented in CODE_BRIGHT. The BBM (Alonso et al., 1990) used for studying the mechanical behavior is coupled with a modified form of the van Genuchten (1980) equation proposed by Universitat Politecnica de Catalunya (UPC, 2017) for the hydraulic behavior. The BBM is an elasto-plastic model that can be considered as state-of-the-art for unsaturated soils at
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the time of writing. The model was formulated for isotropic and triaxial compression stress states. It can model both collapse and expansive responses of unsaturated soils upon wetting. When the soil reaches saturation, the BBM defaults to the modified Cam-clay model. The Calibrated parameters the BBM by MST team (Chapter 7) along with the calibrated parameters for van Genuchten by UHM team (Chapter 8) are used. A significant limitation for the
CODE_BRIGHT is that it doesn’t consider the hydraulic hysteresis behavior for the SWCC. In reality, all the wetting and drying paths in the field are following the scanning curve. Neglecting the hydraulic hysteresis behavior, CODE_BRIFGT was used to simulate the soil initial condition and to check the suction distribution. Figure 10.1 shows the FEM mesh for CODE_BRIGHT simulation. The ground water table was assigned at 30 m depth from the slope crest. A time interval for 1 day was utilized for the soil to reach equilibrium. The pore water pressure distribution is presented in Figure 10.2. The pore water pressure at the slope crest is negative (i.e., suction) and equal to -0.314 MPa. Figure 10.3 shows the initial conditions for the second stage in which the slope surface was subjected to a phase of 30 days continuous raining and the slope behavior was further investigated. Figure 10.4 shows the liquid pressure distribution at the end of the 30 days. Figure 10.5 shows the slope lateral displacement at the end of 30 days. It is clear that the maximum slope displacement was 5.23 cm. The lateral movement distribution can be used as an additional threshold value when compared with the inclinometer field reading. However, it was noticed that the inclinometer readings were very minimal and within the device accuracy. Moreover, again, CODE_BROGHT neglects the hydraulic hysteresis and cannot be used for these kind of cycles of wetting and drying. This preliminary FEM was just to investigate the software capabilities. After extensive use of this software to solve just hydro- or seepage problems for the unsaturated slope, it was discovered that agreement between the calculated and measured values of suction and volumetric water content was difficult to achieve. When the field
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suction paths were superimposed on the SWCC, it was realized that the field values of suction and water content do not follow the wetting or drying curves in most instances. Instead, they scan. Since CODE_BRIGHT does not allow scanning, it was recognized as a major limitation that precluded its use to evaluate the slope deformation behavior.
Figure 10.1 FEM mesh for CODE_BRIGHT.
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Figure 10.3 Second stage conditions.
Figure 10.4 Pore water distribution at the end of 30 days.
S=0.0 MPa
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SUMMARIES, CONCLUSIONS AND SUGGESTION FOR FUTURE RESEARCH