Coupled thermohydroelasticity phenomena in variably saturated fractured porous rocks ‐‐ formulation and numerical solution

• Published in: Coupled Thermo-Hydro-Mechanical Processes of Fractured Media Vol. 79; pp. 93 - 134
• Main Authors: Noorishad, Jahan, Tsang, Chin-Fu
• Format: Book Chapter
• Language: English
• Published: The Netherlands Elsevier B.V 1996; Elsevier; Elsevier Science & Technology
• Subjects: CIVIL ENGINEERING, SURVEYING & BUILDING; Earth Sciences; ENVIRONMENTAL ENGINEERING & TECHNOLOGY; Geology & the lithosphere; Geotechnical Engineering
• ISBN: 9780444825452; 0444825452
• ISSN: 0165-1250
• DOI: 10.1016/S0165-1250(96)80023-X

The physicochemical environment of geologic systems is host to various coupled thermal, hydraulic, mechanical and chemical processes that take place continually at varying rates, dependent on the nature and strength of the sources of these processes in the systems. Scientific interest in these coupled physicochemical processes in the earth's crust, in general, and economic and environmental concerns related to waste geologic disposal, in particular, have resulted in many research efforts aimed at understanding the coupled thermal, hydrologic, chemical, and mechanical (THMC) behavior of geologic systems subject to complex natural or man-made perturbations. In this chapter, the physical aspects of the coupled thermo-hydro-mechanical behavior (THM) are investigated. The work begins with a presentation of background development in the theoretical aspects of the THM phenomena followed by a search in the literature for the THM solution methodologies developed up to the present time. After this review of the state of the art, we first derive the (macroscopic) governing equations for simultaneous occurrences of coupled processes in fully saturated fractured porous media.Next, we propose general field equations for the coupled thermohydroelastic response of variably saturated rocks. This section is complemented by the development of an alternative formulation for the specific cases of weakly non-isothermal conditions. Following these fundamental developments, we offer a finite-element solution methodology and the related algorithms for the solution of the coupled THM problems in variably saturated porous fractured rocks subject to the condition of weak nonisothermal conditions. Finally, solutions of a number of THM sample problems addressing thermoelastic consolidation, flow to a heater test hole, thermohydraulic fracturing, post closure far-field effect in a hypothetical High Level Nuclear Waste Repository (HNLW) and the effects of placement of a HNLW canister and bentonite overpack, are discussed. The solutions to these problems were obtained using the ROCMAS code developed at the Berkeley National Laboratory, which embodies the formulation for low-temperature, coupled thermohydroelasticity phenomena.