The research will examine the coupled thermomechanical behavior of fluid-infiltrated geologic continua with particular emphasis on nonlinear phenomena. This investigation will be an extension of previous work on mall deformation hygrothermal response evaluation of geological media. The governing field equations and finite element formulations will be developed within a framework consistent with continuum thermodynamics mixture theory. One-dimensional and axisymmetric boundary value problems will be initially analyzed for interpretation of coupled mechanisms, model calibration, and assumption refinement. Particular attention will be devoted to the characterization of critically stressed zones using recently developed strain or stress based continuum damage models. Subsequently, advanced two-dimensional problems with applications in nuclear waste isolation and hydraulic fracturing will be investigated.